Photodynamic therapy (PDT) involves the treatment of a patient with a non-toxic photosensitiser. Upon irradiation by an external light source (600-850 nm)[1,2], the photosensitiser causes the production of singlet oxygen radicals at the tumour site which in turn provokes destruction of the tumour and so arousing significant interest as a potential cancer treatment.[3] Notably, a range of Rhenium(I) tricarbonyl complexes were found to induce cell death in a manner recognisably different to that of cisplatin and overcome cisplatin resistance in several resistant cell lines.[4,5]

It has become apparent that 1,10-phenanthroline moieties show favourable fluorescence for the detection of metal ions.[6] Sensors based on the 1,10-phenanthroline moiety coordinated to various metal ions have resulted in compounds exhibiting strong fluorescent properties. El-Awady et al. reported the effects of imidazopyridine derivative binding to DNA. They found that this introduction resulted in apoptosis in lung and breast cancer cells.[7] Thapa et al. synthesised a range of phenanthroline-type derivatives. Structure-activity relationship studies of these phenanthroline-type derivatives confirmed the importance of a [2,2’;6,2”]-terpyridine skeleton for cytotoxicity toward several cancer cell lines.[8]

A range of imidazo[4,5-f]-1,10-phenananthroline type ligands were synthesised and coordinated to Rhenium(I) yielding compounds of the general formula [Re(CO)₃(N,N’)(H₂O)]⁺ where N,N’ is the imidazo[4,5-f]-1,10-phenananthroline type ligand. These ligands and complexes were characterised by multinuclear NMR spectroscopy and IR Spectroscopy. X-ray crystallography data has been obtained for several ligands thus far. The photoluminescent, as well as the DNA binding capacity to calf thymus DNA were studied.

Nucleotides are the building blocks of DNA and RNA. Metal ion play a key role for their functional activities and stability. As nucleotide contains multiple functional groups, such as nucleobases, phosphate group and hydroxyl in the sugar moiety, it is therefore necessary to know the affinities of different coordination donor of nucleotide towards a particular metal ion. In this regard, X-ray investigation have made an important contribution by providing accurate information on the geometry of metal binding to the nucleotides. Molecular structure of these metal-nucleotide complex help to understand specific interaction at a certain condition which set the stage for biological and material applications.In this present work we are specifically synthesized the monomeric structure with phosphate only metal binding where we used ferric ion as metal centre. This is the first example of Iron (III)-Nucleotide ternary complex where we used tripodal tetradentate ligand as an auxiliary ligand. Single crystal X-ray diffraction showed that crystal of [Fe₂O(TPA)₂(AMP)](ClO₄)₂[TPA=Tris pyridyl methyl amine; AMP=Adenosine 5’-monophosphate] and [Fe₂O(TPA)₂(CMP)](ClO₄)₂ [CMP=Cytosine 5’-monophosphate] were crystallized in the triclinic crystal system (space group type P1). In these two structures we observed different packing arrangements of the nucleobase moiety with respect to the metal free counterpart. Here we observed adenine-adenine (Ade-Ade) and cytidine-cytidine (Cyt-Cyt) hydrogen bond formation from two different molecules in the unit cell. Because of the non-coplanar “nature” of auxiliary ligand, we didn’t find π-π stacking interaction between TPA ligand and nucleobase, but it is believed that TPA ligand is providing hydrophobic atmosphere which is important for forming H-bonding “interaction” between nucleobases. In case of [Fe₂O(TPA)₂(GMP)](ClO₄)₂ [GMP=Guanosine 5’-monophosphate] and [Fe₂O(TPA)₂(IMP)](ClO₄)₂ [IMP=Inosine 5’-monophosphate] belong to the monoclinic system , space group P2/c where we found that guanine moiety is making π-π stacking interaction with another guanine moiety and hypoxanthine is hydrogen bonded with another hypoxanthine moiety through bifurcating water molecule. As all the nucleotides are chiral in nature, we records CD spectra of free nucleotide and Iron-nucleotide complexes in liquid state to understand the chirality of nucleotide–metal complexes and supramolecular assemblies.

Phosphine ligands are considered by many as one of the most significant class of ligands in organometallic chemistry. The search of new phosphine chelators, as well as the subsequent functionalization thereof, is a continuing process in order to induce appropriate properties for highly effective catalyst and to a lesser extend in medicinal purposes. Of particular interest is the search for water-soluble and highly stable ligands that can preserve their aquatic solubility even after metal coordination.

In this study, we aim to improve the efficiency of middle/late transition metal homogeneous catalysts (i.e. Re, Rh, Pd and Pt) and fac-[M(CO)₃] (M = Re and Tc) radiopharmaceutical synthons by selectively introducing monodentate and bidentate phosphine ligands consisting of various electronic and steric properties. The use of systematically altered bidentate phosphine ligands such as diphosphinoamine ligands has already been reported to show high selectivity improvements in catalytic reactions such as ethylene tri- and tetramerization [1].

A series of diphosphinoamine ligands was synthesized using methods described in literature [2, 3]. These ligands were then coordinated to various metal (i.e. Re(I), Tc(I), Pt(II) and Pd(II)). Results obtained from the biological analysis and catalytic evaluations have opened up a new window of opportunities for such compounds. @font-face {font-family:"Cambria Math"; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-536870145 1107305727 0 0 415 0;}@font-face {font-family:Cambria; panose-1:2 4 5 3 5 4 6 3 2 4; mso-font-charset:0; mso-generic-font-family:roman; mso-font-pitch:variable; mso-font-signature:-536870145 1073743103 0 0 415 0;}p.MsoNormal, li.MsoNormal, div.MsoNormal {mso-style-unhide:no; mso-style-qformat:yes; mso-style-parent:""; margin-top:0cm; margin-right:0cm; margin-bottom:10.0pt; margin-left:0cm; mso-pagination:widow-orphan; font-size:12.0pt; font-family:"Cambria",serif; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-ansi-language:PT; mso-fareast-language:JA;}.MsoChpDefault {mso-style-type:export-only; mso-default-props:yes; font-family:"Cambria",serif; mso-ascii-font-family:Cambria; mso-ascii-theme-font:minor-latin; mso-fareast-font-family:"Times New Roman"; mso-fareast-theme-font:minor-fareast; mso-hansi-font-family:Cambria; mso-hansi-theme-font:minor-latin; mso-bidi-font-family:"Times New Roman"; mso-bidi-theme-font:minor-bidi; mso-ansi-language:ES-TRAD; mso-fareast-language:JA;}.MsoPapDefault {mso-style-type:export-only; margin-bottom:10.0pt;}div.WordSection1 {page:WordSection1;}

Due to their vast applications in science and technology, the thermo-responsive materials have always been the forefront of the materials science. Usually, materials expand upon heating but the negative thermal expansion (NTE) materials are unusual because they contract along one or more directions with increasing temperature.⁴ Although the NTE effects are not uncommon effect are rarely observed in organic materials and especially in single-component all-organic systems.¹ Recently focus has been shifted to develop the pure organic materials due to their benign nature and flexibility. Moreover, existence of both positive thermal expansion (PTE) and NTE in organic molecular systems are extremely rare.^1b Materials with NTE property finds immense applications in modern technologies² and lightweight, environmentally benign and easily tunable organic materials have plenty to offer in this niche area.^2,3 In an effort to discover unusual PTE and NTE in organic materials, we have studied a series of imidazoline derivatives, where 2-(4-bromophenyl)-4,5-dihydro-1H-imidazole has shown a prominent NTE effect compared to its other derivative. This unique system not only undergoes solvent mediated polymorphic modifications to form centrosymmetric (1C, space group P2₁/c) and non-centrosymmetric (1N, space group Cc) structures but each of the forms experiences single-crystal to single-crystal reversible yet isosymmetric phase transition at ~210 K upon cooling. While form 1C transforms to a structure with space group P2₁/n, the form 1N converts to a new structure but without changing the space group. Interestingly, upon cooling, across the phase transition temperature at ~210 K, 1N undergoes colossal PTE to NTE transition along the a-axis but NTE to PTE along the b-axis while c-axis experiences almost zero thermal expansion. Whereas, 1C exhibits PTE to NTE only along the b­-axis and only PTE along the other two axes. These anisotropic unusual thermal expansions, which is mainly due to the scissor like motion that molecules are undergoing upon temperature stimuli. Given these unusual properties, this novel all-organic material, which is analogous to a known molecular ferroelctric,⁴ may find potential applications in future organic electronics.

Plastic crystals (PCs), formed by certain types of molecules or ions with reorientational freedom, offer both exceptional mechanical plasticity and long range order, hence they are attractive for many mechano-adaptable technologies. While most classic PCs belong to simple globular molecular systems, a vast number of examples in the literature with diverse geometrical (cylindrical, bent, disk, etc.) and chemical (neutral, ionic, etc.) natures have proven their wide scope and opportunities. All the recent reviews on PCs aim to provide insights into a particular application, for instance, organic plastic crystal electrolytes or ferroelectrics. This tutorial review presents a holistic view of PCs by unifying the recent excellent progress in fundamental concepts from diverse areas as well as comparing them with liquid crystals, amphidynamic crystals, ordered crystals, etc. We cover the molecular and structural origins of the unique characteristics of PCs, such as exceptional plasticity, facile reversible switching of order-to-disorder states and associated colossal heat changes, and diffusion of ions/molecules, and their attractive applications in solid electrolytes, opto-electronics, ferroeletrics, piezoelectrics, pyroelectrics, barocalorics, magnetics, nonlinear optics, and so on. The recent progress not only demonstrates the diversity of scientific areas in which PCs are gaining attention but also the opportunities one can exploit using a crystal engineering approach, for example, the design of novel dynamic functional soft materials for future use in flexible devices or soft-robotic machines.

The study of fission tracks in terrestrial minerals and meteorites has demonstrated its usefulness for cosmic-ray prehistory, age, and thermal history of minerals studies [1]. The techniques based in chemical etching of natural tracks has been described by Fleisher, Price & Walker [2]. In 1965 Fleisher, Price & Walker proposed etching conditions for so many minerals. For garnets, the authors proposed a KOH etching for two hours at 150°C, but without measuring these etching conditions and their relation with the fission tracks in the garnets. Haack & Gramse [3] have demonstrated that garnets, especially andradites and spessartines, can be appropriate minerals for fission tracks dating. Posteriorly, [4] etched in boiling (-150 °C) 50 mol / 1 NaOH solution for 20 - 30 min to reveal spontaneous fission tracks in the garnet.

However, for the garnets (Ca,Mg,Fe2+,Mn)3(Al,Fe3+.Mn,Cr,Ti4+)2(SiO4)3, common rock-forming mineral in basic and ultrabasic igneous rocks and metamorphic rocks, any satisfactory or new etchant has been reported after Fleisher, Price & Walker [2], Haack & Gramse [3] and Wang, Chen & Tein [4]. Over the past years the research in fission tracks focused on minerals like Apatite and Zircon and theirs methods and techniques. In certain degree it was influenced by the fact of these minerals present low closing temperatures, in agreement with the maturity temperatures of the hydrocarbons. This research describes a satisfactory revelation of spontaneous fission tracks in garnets. The experimental method used consists in submitting the garnets to a chemical attack using an etching technique. The methodology has been based in [5], however these authors have used their methodology to revel natural fission tracks in olivines. For this reason, in this research we considered some modifications in their experimental method.

The attack has been consisted in a base-acid sequential immersion, where Potassium Hydroxide (KOH) (1mol/L^-1) and Hydrofluoric Acid (HF) were used. The garnets were submitted to KOH at 100°C for 4 minutes. After this, we insert the garnets in the HF for 30 seconds at 23°C. After chemical etching, the fission tracks in our garnets were characterized with scanning electron microscopy (SEM). The fission tracks were analyzed using a scanning electron microscopy. The SEM images were measured using a Zeiss, EVO-MA10. The samples were irradiated with an electron beam of 5kV and the images was captured at 400x magnification.

The fission tracks revealed on this experimental method have between 18.96μm and 50.06μm of length. Based on these results, it indicates that the experimental method is efficient to revel spontaneous tracks in garnets. Whtas suggests that this experimental method can be applied in others minerals and meteorites. On the other hand, new studies with variations of concentration, temperature and time of exposure in the experimental method are necessary to determine the behavior of the fission tracks in the new conditions for the garnets.

Melamine is a precursor for polymeric Carbon Nitride (p-CN) materials showing great promise in a variety of different applications including electro- and photo catalysis [1]. The structure consists of layers of extended graphite-like CN with stoichiometry close to C₃N₄ including only a small amount of hydrogen. Insight into the electronic properties of precursor materials could be valuable for understanding the catalytic properties of p-CNs. The 2,4,5-triamino-s-triazine molecule (melamine) crystalizes in the P2₁/n space group and is an archetypical example of an organic molecular crystal. This study presents the ongoing work of benchmarking synchrotron radiation (with a wavelength of ~0.25 Å) against state of the art in house diffractometers, using respectively Mo (0.71 Å) and Ag (0.56 Å) radiation. Preliminary results show no significant deviation between the three different methods, and the electron density models obtained from the data analysis are for all practical purposes the same. The experimental electron density of melamine crystals is analyzed in terms of chemical interactions. In particular Bader topology and energy frameworks are used to study the chemical importance of the inter-molecular interactions in crystal formation of melamine. Future work includes studies of other p-CN materials with structures that are even closer to the catalytically active p-CN, e.g to gain insight into the chemical effects responsible for the layer forming mechanism.

[1] F. K. Larsen, A. Mamakhel, J. Overgaard, J. E. Jørgensen, K. Kato and B. B. Iversen, Acta Cryst. (2019). B75, 621–633

The phosphorus (P)-stereogenic enantiomers are used in many fields of chemistry, for example in chiral catalysis, stereoselective transformation and optical resolution. They are in the forefront of interest in the last decade.

Several dialkyl-arylphosphine oxide compounds have been prepared by Péter Bagi and his co-workers [1]. The newly synthetized phosphorous derivatives are sensitive racemic compounds. Trying several resolving agents, resolution was performed and the enantiomers were separated with (R,R)- or (S,S) -spiro-TADDOL (-1,4-dioxaspiro[4.5]decane-2,3-diylbis(diphenylmethanol)) in gram scale. Some diastereomers of the series (i.e. methylphenylpropylphosphine oxide and ethylphenylpropylphosphine oxide) were crystallized in nitrogen atmosphere, and investigated by single crystal X-ray diffraction (Figure 1). The absolute configurations of the dialkyl-arylphosphine oxides were successfully determined [2]. We present the structures of a few diastereomers formed using TADDOL, where the SXRD results revealed the main interactions which contribute to the enantiomeric recognition. Hirshfeld surface analysis and DFT calculation were performed using the software Crystal Explorer in order to understand the secondary interaction network.

Rod-shaped single crystals of HoF(OH)₂ could be synthesized from Ho₂O₃ and HoF₃ using a high-pressure hydrothermal synthesis route in order to obtain crystalline holmium fluoride oxide (HoFO). The reaction was performed in a gold capsule filled with the starting materials and about 15 vol-% of demineralized water to provide suitable conditions. The gold capsule was sealed by cold-welding and placed into a rock-salt pressure cell. Using an end-loaded piston-cylinder high-pressure apparatus deriving from the Boyd and England design, the cell pressure was dwelled on 500 °C at 10.5 kbar for five days [1]. After quenching to room temperature, small pale-yellow crystals were isolated and investigated using single-crystal X-ray diffractometry. The hexagonal unit cell of the measured crystals showed a noticeable deviation regarding the detected axes and density, when compared to UCl₃-type Ho(OH)₃ (a ≈ 626.6 pm, c ≈ 355.3 pm, ρ_X = 5.94 g/cm³ [2]; our results for HoF(OH)₂: a ≈ 603.3 pm, c ≈ 356.8 pm, ρ_X = 6.44 g/cm³). Therefore, it was concluded that a mixed F^–/OH^– anion site is present, leading to the composition HoF(OH)₂. The F^–-to-OH^– ratio of 1:2 is plausible, when the molar volumes of UCl₃-type Ho(OH)₃ (V_m = 36.38 cm³/mol) [2] and HoF(OH)₂ (V_m = 33.86 cm³/mol) are compared with the one of YF₃-type HoF₃ (29.03 cm³/mol; d(Ho–F) = 229 – 232 pm plus 250 pm for C.N. = 8+1) [3].

The UCl₃-type crystal structure of HoF(OH)₂ (space group: P6₃/m) features one crystallographic position for each ion. Ho³⁺ is surrounded by nine anions in the shape of a tricapped trigonal prism [HoF₃(OH)₆]^6– (Figure 1) with interatomic distances of d(Ho–F/OH) = 237 pm for the prism anions and d(Ho–F/OH) = 234 pm for the capping ones. This finding contrasts with the crystal structure of Ho(OH)₃, where the bond lengths to the prism corners are with 242 pm almost 3 pm shorter than those to the caps [2].

To investigate the mixed occupation of the anion site with OH^– and F^– anions, wavelength-dispersive X-ray spectrometry (WDXS) was performed for the measured crystal. The spectrum clearly showed the presence of both the O-K_α and the F-K_α emission line in relevant intensity with a F:O ratio of 35:65 and thus confirmed the structure model derived from the single-crystal X-ray diffraction data.

High-spin Ni(II) complexes have been a very important class of molecules due to their potential application as a new type of magnetic materials. In general, multinuclear Ni(II) complexes, such as Ni₄O₄ cubane, may exhibit either ferromagnetic or antiferromagnetic interactions between the nickel ions, as well as the slow magnetic relaxation characteristic for single molecule magnets (SMM) [1].

In this work we describe the preparation of four new multinuclear Ni(II) complexes: [Ni₂(BrQ)₃(HBrQ)₃]ClO₄ (1), [Ni₂(dBrQ)₄(MeOH)₂] (2), NH₂(CH₃)₂[Ni₂(µ-Cl)₂(BrQ)₃(DMF)(H₂O)]·DMF (3) and [Ni₄(ClQ)₆Cl₂(H₂O)₂]·2DMF (4), containing molecules of halogen derivatives of 8-hydroxyquinoline: 5-chloro-8-hydroxyquinoline (HClQ), 7-bromo-8-hydroxyquinoline (HBrQ) and 5,7-dibromo-8-hydroxyquinoline (HdBrQ) (Fig. 1). The complexes were studied by infrared spectroscopy, CHN elemental analysis and single crystal X-ray analysis.

Figure 1. Structural formulas of different halogen derivatives of 8-hydroxyquinoline.

Using infrared spectroscopy, we identified individual characteristic vibrations in the measured spectra of complexes 1 – 4, which confirmed the presence of coordinated molecules of anionic ligands ClQ, BrQ or dBrQ, as well as perchlorate anion in sample 1 and solvent water and dimethylformamide molecules in samples 3 and 4.

Structural analysis revealed different bridges between the central nickel atoms in the structures of these multinuclear complexes. Nickel atoms are bridged by the hydrogen atom connecting the opposite oxygen atoms in the HBrQ molecules (1), by two oxygen atoms of the dBrQ ligands (2), by two chlorine atoms (3) and by six oxygen atoms of the ClQ ligands; four of them bridge two nickel atoms while remaining two bridge three nickel atoms (4). As a result, complexes 1, 2 and 3 are dinuclear, while complex 4 forms a tetranuclear structure. We observed the stabilization of these complexes through intermolecular interactions, such as hydrogen bonds (1 – 4) and π – π interactions (2 and 4).

[1] Gusev, A. N., Nemec, I., Herchel, R., Baluda, Y. I., Kryukova, M. A., Efimov, N. N. & Kiskin, M. A. (2021). Polyhedron. 196, 115017.

Slovak Grant Agencies (VEGA 1/0148/19 and VVGS-PF-2021-1769) are acknowledged for financial support.

Five new zinc(II) complexes, {Na[Zn(ClNQ)(SO₄)(H₂O)]}_n (1), [Zn(dNQ)₂(H₂O)₂]·1,4-dioxane (2), [Zn(dNQ)₂(H₂O)₂] (3), NH₂(CH₃)₂[Zn(ClNQ)₃]·DMF (4) and K[Zn(ClNQ)₃]·2DMF (5), (HClNQ = 5-chloro-7-nitroquinolin-8-ol, HdNQ = 5,7-dinitroquinolin-8-ol (Fig.1)) have been prepared. All complexes were characterized by IR spectroscopy, elemental analysis and X-ray structure analysis.

Figure 1. Chemical structures of HClNQ (left) and HdNQ (right)

Complex 1 has a polymeric structure. Zn(II) atom is penta-coordinated by one bidentate molecule of ClNQ ligand, one molecule of water and a pair of crystallographically equivalent sulfate anions, which interconnect adjacent zinc atoms to form a zig-zag chain.
In addition, the central atoms are also connected through ionic interactions between oxygen atoms with a partial negative charge and sodium cation.

Complexes 2 and 3 have similar molecular structures, Zn(II) atom sits at the center of the symmetry, therefore only a half of the molecule is independent. In their crystal structures, there are two trans-coordinated dNQ molecules in the equatorial plane while two water molecules occupy axial positions, forming a deformed octahedral geometry. Complex 2 also contains one uncoordinated molecule of 1,4-dioxane.

Complexes 4 and 5 are ionic compounds with very similar structures, in which Zn(II) atom is tris-coordinated by molecules of deprotonated 5-chloro-7-nitro-quinolin-8-ol with nitrogen and oxygen donor atoms coordinated in mer-fashion. The negative charge of the complex anions is counterbalanced by uncoordinated dimethylammonium and potassium cations, respectively, and interesting orientation of the oxygen atoms to NH₂(CH₃)₂⁺ (4) and K⁺ (5) ions is observed. In addition, the complex 5 contains one more solvated molecule of DMF molecule.

Slovak Grant Agencies (VEGA 1/0148/19, VVGS-PF-2020-1425 and VVGS-PF-2021-1772) are acknowledged for financial support.

Ever since their first description in 2013 [1] crystal sponges have attracted considerable attention, for their ability to provide structural information on hard to crystallize or non-crystalline compounds [2]. However, their analysis proved to be tricky, with infused compounds highly disordered in the structure channels in overlapping disorder with solvent. Since the solution of highly disordered systems requires reliable high resolution data, and considering large unit cell of crystal sponges, the use of Mo-Kα radiation was discouraged in favour of Cu-Kα radiation [3]. During our studies of crystal sponge infusion procedure, we have observed gradual darkening of studied crystals combined with gradual disappearance of strong diffractions in measured frames. We have decided to evaluate the possible radiation decay of studied (ZnI₂)₃(tpt)₂ crystal sponge, by measuring the series of identical experiments with the same crystal. We have chosen series of five experiments with 12 hours each, resulting in overall irradiation time of 60 hours. The crystal darkening was observed during the measurements, resulting in a black crystal, with apparent loss of strong diffraction spots in measured frames, see Fig. 1a. The data we obtained have shown significant loss of diffraction reliability with I/σ(I) decreasing from 3.62 to 1.67 in 0.84-0.81 Å shell and from 6.09 to 3.34 in 0.97-0.92 Å shell. The R_int increased in respective shells from 0.166 to 0.335 and from 0.099 to 0.158. The decrease of data quality was also apparent in the structure model, with R_all increasing from 8.36 % to 10.56 %. Average U_eq increased from 0.071 to 0.099 considering only the framework atoms.

We decided to evaluate the radiation decay using the Mo-Kα as well, since the radiation of lower wavelength should be less absorbed by the crystal sponge. As previously stated the use of Mo-Kα is discouraged for possibility of diffraction spot overlaps and presence of low and high angle diffraction spots in one frame, disallowing the longer irradiation times for high angle diffractions. However, both of these issues are counteracted by increasing the detector distance from the sample. Increasing the detector distance from 53 mm to 140 mm allows an experimental strategy similar to Cu-Kα experiments, with varying irradiation times without detector overflows. During the data collection following the same procedure, no significant crystal darkening or loss of strong diffraction in measured frames was observed, see Fig 1b. Although some loss of diffraction reliability was observed, with I/σ(I) decreasing from 4.75 to 4.36 in 0.85-0.82 Å shell and 8.30 to 7.65 in 1.00-0.94 Å shell, it was less pronounced. Only a minor increase of R_int in respective shells was observed, with 0.110 increasing to 0.113 and 0.063 to 0.069. The structure model behaves accordingly with R_all increasing from 10.48 to 10.97 and average U_eq increasing from 0.034 to 0.035.

Figure 1. Crystal image and selected frame before and after 60 hours of irradiation using a) Cu-Kα radiation, b) Mo-Kα radiation.

[1] Inokuma, Y., Yoshioka, S., Ariyoshi, J., Arai, T., Hitora, Y., Takada, K., Matsunaga, S., Rissanen, K., Fujita, M. (2013). Nature 495, 461–466. [2] Matsuda, Y., Mitsuhashi, T., Lee, S., Hoshino, M., Mori, T., Okada, M., Zhang, H., Hayashi, F., Fujita, M., Abe, I. (2016). Angew. Chem. Int. Ed. 55, 5785–5788. [3] Hoshino, M., Khutia, A., Xing, H., Inokuma, Y., Fujita, M. (2016). IUCrJ 3, 139–151.

Keywords: X-ray diffraction; Crystal sponge; Decay

This research was supported by the project 20-14770Y of the Grant Agency of the Czech Republic.

In 2002, Kanatzidis et al. synthesized and characterized the rare-earth metal(III) hexaselenidodiphosphate(IV) Ce_1.333[P₂Se₆], which crystallizes monoclinically in the space group P2₁/c [1]. Schleid et al. succeeded to find with Nd_1.333[P₂Se₆] [2,3] a further representative, which showed the same structured formula, but adopts a different structure type. It crystallizes in the triclinic space group P with a modified NaYb[P₂S₆]-type structure [3], whilst Ce_1.333[P₂Se₆] principally mimics the NaCe[P₂Se₆]-type structure [1]. Here we present the gap-filling Pr_1.333[P₂Se₆], which also crystallizes triclinically in the space group P with a = 685.32(5) pm, b = 759.41(6) pm, c = 962.56(7) pm, α = 90.087(3)°, β = 91.723(3)° and γ = 90.034(3)° for Z = 2 at 293 K (CSD number: 2089248), just like Nd_1.333[P₂Se₆]. An extended unit cell of the title compound is depicted in Figure 1 (mid) with highlighted [P₂Se₆]^4– units, which occur in staggered conformation, very characteristic for hexaselenidodiphosphates(IV). The interatomic distances within these ethane-like anions are also well in the usual range (d(P–P) = 220 – 221 pm, d(P–Se) = 218 – 220 pm). The environment of the two distinct Pr³⁺ cations resemble bicapped trigonal prisms with distances between praseodymium and selenium from 303 to 337 pm for C.N. = 8 (Figure 1, left and right). Bicapped trigonal prisms are also found in the neighboring compounds Ce_1.333[P₂Se₆] and Nd_1.333[P₂Se₆] with very similar interatomic Ln–Se distances. Whilst in the neodymium and praseodymium derivatives these [LnS₈]^13– polyhedra are edge-connected to form single chains for every individual cation (Ln1 and Ln2), which finally fuse to a framework, a three-dimensional network immediately emerges for the cerium compound from selenium polyhedra of the three crystallographically different Ce³⁺ cations with C.N. = 8. All three compounds have cationic defects in common, but the defect sites for Pr_1.333[P₂Se₆] are on different crystallographic positions as compared to Nd_1.333[P₂Se₆], making both structures not completely isotypic.

If the volumes of the unit cells for Ce_1.333[P₂Se₆] (a = 680.57(5) pm, b = 2296.85(15) pm, c = 1172.26(8) pm, β = 124.096(1)° for Z = 6 at 100 K), Pr_1.333[P₂Se₆] (vide supra) and Nd_1.333[P₂Se₆] (a = 682.41(5) pm, b = 757.98(6) pm, c = 961.03(7) pm, α = 90.176(3)°, β = 91.789(3)°, γ = 90.108(3)° for Z = 2 at 293 K) are compared and the effect of the lanthanoid contraction is taken into account, they can be nicely compared, if the number of formula units in the unit cell is reduced to Z = 2. Then the volumes are 0.506 nm³ for Ce_1.333[P₂Se₆], 0.501 nm³ for Pr_1.333[P₂Se₆] and 0.497 nm³ for Nd_1.333[P₂Se₆].

Synthesis, characterization and in vitro activities of aniline dithiocarbamate crystals

Ayodele Temidayo Odularu¹, Peter Adewale Ajibade², Johannes Zanoxolo Mbese¹, Opeoluwa Oyehan Oyedeji¹

¹University of Fort Hare, Alice, South Africa; ²University of Kwa Zulu-Natal, Pietermaritzburg, South Africa.; 201106223@ufh.ac.za

One pot synthesis was used to prepare aniline dithiocarbamate from aniline, carbon(IV) sulfide and sodium hydroxide [1]. Aniline dithiocarbamate crystals (ai-dtc; C₇H₁₂NNaO₃S₂) which grew from solution were washed with diethyl ether, and subjected to single x-ray crystallography. The crystals were collected and mounted on a four circles diffractometer Gemini of Oxford Diffraction, using a graphite monochromated CuKα radiation (λ = 1.54184 Å). Super flip program was used to solve the crystal structure; while refinement was done using full matrix least-squares technique with the support of Jana 2006. The resulting synthetic crystalline structure (Figure 1) appeared as crystalline polymolecule (Figure 2) which has crystal data with three dimensions of a= 2.86663(4) Å, b=6.9 386 (3) Å and c=11.3127 (3) Å. Other characterization techniques of physicochemical parameters, FT-IR, UV-Vis and NMR further confirmed ai-dtc structure. [2] For the in vitro antibacterial studies, ai-dtc was screened against four bacterial strains (Staphylococcus aureus MRSA252, Enterococcus faecalis ATCC 19433, Escherichia coli MC4100 and Pseudomonas aeruginosa PAO1). Result showed that ai-dtc had modest activity against Staphylococcus aureus [2].

Keywords: One pot synthesis, dithiocarbamates crystals, polymers, single x-ray crystallography, antibacterial activities

Figure 1: C₇H₁₂NNaO₃S₂ crystal structure. Figure 2: C₇H₁₂NNaO₃S₂ polymolecule.

References

1. Ahamad, M. M.; SureshKumar, E. V.; Rao, R. M.; Phebe, P. Arch. Appl. Sci. Res. 2016, 8, 61-64.

2. Odularu, A. T.; Ajibade, P. A. Bioinorg. Chem. Appl. 2019, 2019, 1-15.

The new orthophosphate PbNi₂Fe(PO₄)₃ have been synthesized by solid-state reaction route and characterized by X-ray diffraction, scanning electron microscopy, Infrared and Raman spectroscopy.

The analysis by single crystal and powder X-ray diffraction techniques showed that this compound crystallizes in the orthorhombic system with Imma space group and unit cell parameters a = 10,415 (3) Å; b = 13,165 (4) Å; c = 6,536 (2) Å; V = 896,15 (5) ų; Z = 4.

The three-dimensional framework of the crystal structure is built up by [PO₄] tetrahedra, [FeO₆] octahedra and [Ni₂O₁₀] dimers of edge-sharing octahedra, linked through common corners or edges. This structure comprises two types of layers stacked alternately along the [100] direction. The first layer is formed by edge sharing octahedra ([Ni₂O₁₀] dimer) linked to [PO₄] tetrahedra via common edges and vertices while the second layer is built up from a row of corner-sharing [FeO₆] octahedra and [PO₄] tetrahedra forming an infinite linear chain. The layers are held together through vertices of [PO₄] tetrahedra and [FeO₆] octahedra, leading to the appearance of two types of tunnels parallel to the a and b-axis directions in which the Pb²⁺ cations are located.

The structure affiliation of the studied phosphate to that of α-CrPO₄ and its spectroscopic properties will be discussed.

There are adequate number of molecules in nature which exhibit stimuli-response behaviour. Mimicking them, molecular crystals responding to mechanical and thermal stimuli, arraying actuating properties, comparable to that of soft materials, are yet in quest. With advances in the field of stimuli responsive molecular crystals, detailed investigation on the existing systems are helping in reformation of models which help in relating the macroscopic (kinematic) events to molecular (mechanistic) aspects.[1] Dynamic effects such as jumping, bending, popping, splitting as an outcome of thermal/mechanical/photo stimuli have become much more intriguing and explicate by linking observations from AFM/SEM/HSM to SCXRD/PXRD/Stress-Tensile test experimental data.[2,3]

On lowering temperature (258-278K), single crystals of a diphenyl phosphate 2-chloroanilium salt were observed exhibiting reversible thermal expansion/compression, [4] accompanying phase transition which simultaneously shows splitting and/or bending (morphology and size specific phenomenon) of crystals [5] (Fig 1, Right). The reversible thermoelastic phase transitioning behaviour could be classified under shape memory materials. [6,7] The elastic bending response to mechanical stimuli, on exerting force on the major face of the crystal at room temperature (Fig. 1, Left), highlights another exploitable application of this molecular crystal. [8]

Figure 1. Three-point bending experiment carried out at major face (001) of single crystal; Observation of reversible bending and splitting on carrying out cooling-heating cycle of single crystals on cold stage microscope.

[1.] Karothu D. G, Weston J., Desta I.T. & Naumov P. (2016). J. Am. Chem. Soc., 138, 13298−13306.

[2.] Devarapalli R., Kadambi S. B., Chen C-T, Rama Krishna G., Kammari B. R., Buehler M. J., Ramamurty U., & Reddy C. M. (2019). Chem. Mater., 31, 1391-1402.

[3.] Dey S., Das S., Bhunia S., Chowdhury R., Mondal A., Bhattacharya B., Devarapalli R., Yasuda N., Moriwaki T., Mandal K., Mukherjee G. D. & Reddy C. M. (2019). Nat. Commun., 10, 3711.

[4.] Liu H, Gutmann M. J., Stokes H. T., Campbell B. J., Evans I. R., & Evans J.S.O. (2019). Chem. Mater., 31, 4514−4523.

[5.] Ahmed E., Karothu D. P., Warren M. & Naumov P. (2019). Nat. Commun., 10, 3723.

[6.] Takamizawa S. & Takasaki Y. (2016). Chem. Sci., 7, 1527-1534.

[7.] Park S. K. & Diao Y. (2020). Chem. Soc. Rev., 49, 8287-8314.

[8.] Dey S., Das S., Bhunia S., Chowdhury R., Mondal A., Bhattacharya B., Devarapalli R., Yasuda N., Moriwaki T., Mandal K., Mukherjee G. D. & Reddy C. M. (2019) Nat. Comm. 10, 3711.

With carbon dioxide (CO₂) reaching a peak concentration of 416 ppm in 2019 and still increasing yearly, there still has been no viable option to reduce the CO₂ concentrations in the atmosphere. This is in part due to the relatively inert nature of CO₂. However, the biomimetic investigation of plants, specifically CAM (Crassulacean Acid Metabolism) plants (Such as cacti and succulents), illustrate how CO₂ may be converted and stored [1]. The biomimetic approach can therefore aid in discovering an approach which may help overcome the energy and financial barrier for carbon capture and sequestration (CSS).

The amidines and guanidines are two classes of organic nitrogen bases that can activate CO₂ and have been used in switchable ionic liquids (SWILs) to store CO­₂ and as cocatalysts or ligands in metal catalyzed reactions [2]. Furthermore, 2,2’-bipyrdine ligands have also shown promise in catalytic reactions of CO₂ [3].

The focal points to be discussed in this presentation are CO₂ and its uptake cycle in crassula ovata succulents (Fig.1(a)). Thereafter, the synthesized rhodium metal complexes, which contain 1,5-cyclooctadiene (COD) and the nitrogen bases as ligands, will be discussed along with characterization by single-crystal x-ray diffraction (SC-XRD). Special focus will be given to the influence the ligands have on the coordinated COD which “mimics” the Venus fly-trap plant, illustrated in Fig. 1(b-d), and the related kinetic studies by a neutral ligand to replicate CO₂ [4]. Interestingly, the results from the kinetics showed that the forward reaction rate (k₁) for the amidine-containing rhodium complex was k₁ = 2.16 x 10³ M^-1s^-1 with a half-life of 321 ms and ten-times faster for the rhodium complex containing the guanidine ligand. This can be seen to correlate with the change in angles (Fig. 1(c,d)) of the COD.

In addition to the above, five–coordinate platinum group metal complexes containing COD, a methyl/ phenyl group and various 2,2’-bipyridine ligands that have been isolated and characterized will be discussed in a similar fashion to the Rh-COD complexes [5]. An evaluation and comparison of the COD angles will illustrate the importance that crystallography has on understanding molecular structures and kinetics.

The synthesis of transition metal complexes with central metals Ni(II), Co(II) and Zn(II) with thiocyanate or chloride anions and pyridine derivative co-ligands according to the formula of Werner complexes MX₂L₄ presented structural diversity. The ‘tunability’ of the crystal structures arises from the transformation of the nature and size of the inclusion cavities. In general, octahedral coordination complexes occur with nickel and cobalt. However, zinc showed a preference for tetrahedral coordination, resulting in MX₂L₂ crystals, where M is the central metal, X the anion and L the pyridine derivative ligand.

The effect of the position of derivatives on the pyridine ring (meta- or para-) altered the interaction between the host molecules forming a variety of frameworks. In the case of nickel and cobalt, the nicotinamide ligand (meta position amide) a linear arrangement of the ligands occurs resulting in a predictable and robust framework which shows hydrogen bonding of amide tetramers. Steric hindrance between the derivatives results in torsioning of the ligands if the derivative is para to the pyridine nitrogen. Hosts Ni(NCS)₂ and Co(NCS)₂ with four isonicotinamide ligands presented a variety of frameworks ranging from spiral format to herringbone arrangement. The trans ligands present a propeller arrangement which disables the predictability of the framework.

A further discovery was made with mixed ligand complexes. The prominence of amide dimer formation via hydrogen bonds between nicotinamide ligands was emphasised yet isonicotinamide ligands showed only discrete hydrogen bonds. Sulphur hydrogen bonds O-H···S in nickel clathrates resulted in better thermal stability. This case was observed with Ni(NCS)₂(nicotinamide)₄ clathrates with an alcohol guest compared with those with carbonyl guest.

Discrimination between two guests was shown by nickel complexes for a number of equimolar guests, notably the selection of 1-butanol from an equimolar mixture with 2-pentanol; 4-methylcyclohexanone from a mixture of 3- and 4-methylcyclohexanone; and propanol was selected over isopropanol. The host Ni(NCS)₂(4-phenylpyridine)₂(isoquinoline)₂ targets meta-xylene over ortho- and para-xylene in an equimolar mixture of the isomers. Stronger C-H···π intermolecular interactions were found in the Hirshfeld surface analysis between the host and meta-xylene than in the other two isomers.

The versatility of the central metal in these Werner complexes was investigated by measuring the thermal properties of the release of the guest from isotypic clathrates using differential scanning and thermogravimetric analysis. The diversity of the complexes and the versatility of the ligands in these Werner complexes demonstrates their importance in the discriminatory ability of guest mixtures.

The method of symmetry breaking potential and first order cluster expansion technique for the partition functions adopted for the theory of ordering in liquid crystals has been extended to symmetric and asymmetric molecules. The order parameter is calculated as a function of temperature and packing coefficient as a function of position of double bond in alkenyl chain length for homologous series of 4–alkenyl bicyclohexylnitrile Compounds [1-4]. The theoretical calculations adopted the method of Shivaprakash et al [5], account fairly well for the gradient differences in the order parameters of symmetric and asymmetric molecules and packing coefficients. Variation of order parameter with temperature for 1d₁CC is shown in Figure 1.

It is of interest to compare the molecular packing formula given by Kitaigorodsky [6] of the homologous series of 4–alkenyl bicyclohexylnitrile compounds. Compound 1d₁CC & 3d₁CC possess double bond after the first carbon chain from cyclohexyl ring and exhibit nearly same packing coefficient. On the other hand, compounds 1d₃CC & 0d₃CC possess double bond after the third carbon chain from cyclohexyl ring and exhibit nearly same packing coefficient.

Figure 1. Variation of order parameter with temperature for 1d₁CC

Keywords:

Order parameter; packing coefficients; structure-property relation.

References:

[1] Sakuntala Gupta, kinkini Bhattacharyya, S. P. Sengupta, Sukla Paul, Alajos Kalman and Laszlo Parkanyi, A mesogenic alkenyl compound, Acta Cryst., 1999, C55: 403-405.

[2] S. Gupta, A. Nath, S.Paul, H. Schenk and K. Goubitz, Structures and Properties of an Alkenyl Liquid Crystalline Compound, Mol. Cryst. Liq. Cryst., 1994, Vol. 257: pp. 1-8.

[3] Sakuntala Gupta, S. P. Sen Gupta, R. A. Palmer, B. S. Potter and M. Schadt, Crystal Structure of 4(1՛՛-butenyl) 4՛(cyano)1,1՛ bicyclohexane, Mol. Cryst. Liq. Cryst., 2002, Vol. 378: pp. 193-202.

[4] Sakuntala Gupta, R. A. Palmer, M. Schadt, S. P. Sen Gupta, Structural analysis of a mesogenic 4-alkenyl bicyclohexylnitrile, Liq. Cryst., 2001, Vol. 28, No. 9: 1309-1313.

[5] N. C. Shivaprakash & Jn. Shashidhara Prasad, A Theoretical Investigation of the Lattice of Symmetric and Asymmetric Rigid Rods with Anisotropic Dispersion Forces and Rigid Body Repulsions, Mol. Cryst. Liq. Cryst., 1981,74: 215-226.

[6] A. I. Kitaigorodsky, Molecular Crystals and Molecules, Academic Press, New York-London,1973

Diketopyrrolopyrrole (DPP) is an industrially important dye. It is also expected to be used as a functional dye, and a lot of research has been done on its various applicability. The introduction of flexible alkyl groups into the amino groups of DPP is reported to lead polymorph occurrence. [1][2] A derivative of DPP in which both amino groups are substituted with a butyl group are found to exhibit three differently-coloured polymorphs (red, orange, and yellow). All polymorphs could be obtained individually using the liquid-liquid diffusion method with chloroform as the good solvent and n-hexane as the poor solvent. The preparation of the red and yellow forms was easy, whereas the orange polymorphs was infrequently obtained. The results of the crystal structure analysis indicate that the asymmetric unit of the red and yellow polymorphs is one molecule, and that of the orange polymorph is two molecules. The molecular conformation of the three polymorphs is shown in Fig. 1. The red and orange polymorphs have butyl groups extending to both sides of the molecular plane. The two butyl groups of the yellow polymorph were found to project out from the molecular plane in the same direction. The crystal structures of the three polymorphs are shown in Fig. 2. The molecules in the red polymorph are stacked along the a-axis. The orange crystal has two asymmetric units (illustrated as green and yellow molecules in Fig. 2), and each asymmetric unit is stacked along the b-axis. The yellow crystals formed a chain-like structure with the π-conjugated planes facing each other. The detailed comparison of their crystal structures and their optical and thermal properties will be presented.

Prussian Blue Analogues (PBAs) are transition metal cyanides, widely investigated due to their catalytic and optical activity, ability to transport and store ions and small gas molecules. The later property is allowed by the presence of the large number of structural hexacyanometallate vacancies, which connect to form a porous network. These vacancies are filled with water: coordinated water molecules, which replace missing cyanide groups, and zeolitic water in the spherical cavities.

In this work we report a novel diffuse scattering signal, appearing after fast freezing of the PBA crystals. This signal emerges in the form of diffuse “clouds” around the Bragg peaks, which grow in intensity at higher Q, and are caused by the corrugation of the atomic lattice. We hypothesize that this corrugation is the response of the PBA lattice to the stress developed by water freezing in the nanopores. Furthermore, we discuss the effect of freezing on mechanical properties of Mn[Co] PBA.

RHODIUM (I) N,O HYDROXAMIC ACID COMPLEXES AS MODEL CATALYSTS

Mokete Motente^a, Johan Venter^b, and Alice Brink^c

Derparment of Chemistry, University of the Free State, Bloemfontein 9300, South Africa

Email: mokete.motente@gmail.com

Key words: Rhodium, catalysis, hydroformylation

Rhodium metal complexes are some of the key catalysts utilised in homogenous catalysis, and one of the most crucial considerations when forming a metal complex is the choice of ligand systems due to their influence on the reactivity of the metal atom,[1] hence hydroxamic acids were used for the purposes of this study due to their high metal affinity.[2] Phosphine ligands on the other hand were utilised due to their unique electronic and steric properties and it is known that the presence of phosphine ligands in rhodium systems also gives way to more active, highly selective catalysts which are reactive under milder reaction conditions.[3]

The overarching aim of this study was therefore to synthesise carbonyl phosphine Rhodium(I) complexes using O,O and N,O- hydroxomate bidentate ligands as model catalysts and they were successfully characterised with various characterisation techniques including single crystal X-ray diffraction (SCXRD). The study also focused on two important reactions, oxidative addition and migratory insertion which are the two crucial steps that take place during the Monsanto catalytic process.

1 P.W.N.M. Van Leeuwen, Homogenous Catalysis: Understanding the Art, Dordrecher: Kluwer Academic publishers, 2004.

2 P.M. Maitlis, A. Haynes, G.J. Sunley, M.J. Howard, J. Chem. Soc., Dalton Trans., 1996, 2187.

3 C.A. Tolman, Chem. Rev., 1977, 77, 313.

Syntheses and crystal structures of new ruthenium(II) organometallic compounds with NSAID type ligands M.Schoeller¹, J. Moncoľ¹¹Department of inorganic chemistry, Institute of inorganic chemistry, technology and materials, Faculty of chemical and food technology, Slovak University of Technology in Bratislava, Radlinského 9, 812 37 Bratislava, Slovakia Email of communicating martin.schoeller@stuba.sk

Ruthenium compounds play key role in development of new cytostatic agents in cancer therapy. Main features for choosing ruthenium are: a) possibility of existence at least in two oxidation states under physiological conditions (+II, +III), b) variable kinetic inertness with respect to the oxidation state which allows activation by reduction mechanism, c) ability to mimic iron in transport pathways [1-3]. NSAIDs as ligands introduce interesting strategy of cytostatic effect tuning. Complexes of NSAIDs with ruth enium can affect pathways of angiogenesis and production of metastases [4]. Increased cytotoxicity of some compounds can be explained by increased lipophilicity and therefore also with cellular input [4,5].

In order to prepare new ruthenium(II) compounds we chose [Ru₂(p-cymene)₂Cl₄] organometallic precursor and NSAIDs as ligands. Figure 1 shows new four-nuclear ruthenium(II) organometallic complex with new single bond between ruthenium(II) and 5-fluorosalicylate carbon. Single crystal diffraction data were collected with four-cycle Stoe StadiVari diffractometer with PILATUS3R 300K hybrid pixel array detector using microfocused X-ray source Xenocs Genix3D Cu HF (CuKα, λ = 1.54186Å). The crystal structures were solved by direct method using SHELXS [6]. The crystal structures were drawn with OLEX2 [7]. Supramolecular structures were analysed using CrystalExplorer [8].

Figure 1. Molecular structure of four-nuclear ruthenium(II) compound with formula [Ru₄(p-cymene)₄(5-Fluoro-SA)₂Cl₂].

[1] Housecroft, E. C., Sharpe, G. A. (2005). Inorganic chemistry. Essex: Pearson Education Limited. [2] Dabrowiak, J. C. (2017). Metals in Medicine. John Wiley & Sons. [3] Alessio, E. (2011). Bioinorganic Medicinal Chemistry. John Wiley & Sons. [4] Srivastava, P., Mishra, R., Verma, M., Sivakumar, M. Patra, K. A. (2019). Polyhedron, 172, 132-140. [5] Chen, J., Zhang, Y., Jie, X., She, J., Dongye, G., Zhong, Y. Deng, Y. Wang, J., Guo, B., Chen, L. (2019). J. Inorg. Biochem., 193, 112-123. [6] Sheldrick, G. M. (2015). Acta Crystalogr., A71, 3-8. [7] Dolomanov, O. V., Bourhis, L. J., Gildea, R. J., Howard, J. A. K., Puschmann, H. (2009). J. Appl. Cryst., 42, 339-341[8] Turner, M. J., McKinnon, J. J., Wolff, S. K., Gromwood, D. J., Spackman, P. R., Jayalitaka, D., Spackman, M. A. (2017) CrystalExplorer 17.5, University of Western Australia, Australia

Keywords: ruthenium(II); NSAID; cytostatic agents; p-cymene

This work has been created with the support of the Ministry of Education, Science, Research and Sport of SR within the Research and Development Operational Programme for the project “University Science Park of STU Bratislava, ITMS 26240220084, co-funded by the European Regional Development Found. Grand Agency of Slovak Republic (VEGA 1/0639/18, VEGA 1/0482/20, APVV 19-0087) is gratefully acknowledged for their financial support.

In an experiment to obtain single crystals of SmF₂ [1–3], a mixture of Sm, SmF₃ and NaCl (as flux) was heated up inside a sealed niobium capsule to 850 °C for four days and slowly cooled down with 5 K/h. In addition to dark red single crystals of the target compound SmF₂, also orange single crystals of SmFCl [4] were obtained. A PXRD experiment showed an additional phase, which was characterized as SmFO [5]. The ratio of them was determined via the Fullprof Suite by PXRD (Cu-K_α radiation) as about 70:5:25. By EDX analysis, the stoichiometry of all three named compounds was confirmed. SCXRD experiments (Mo-K_α radiation) were performed with single crystals (red SmF₂: CSD-2087284, orange SmFCl: CSD-2087285). While SmF₂ and SmFO crystallize with the CaF₂-type structure (cubic; Fm-3m; PXRD-data: a = 579.62(3) pm and a = 556.31(3) pm, CSD-2087286 for SmFO), SmFCl adopts the PbFCl-type structure (tetragonal, P4/nmm; a = 413.7(1) pm and c = 699.1(3) pm). The unit-cell parameters from the SCXRD measurements of SmF₂ (a = 580.31(4) pm) and SmFCl (a = 413.59(5) pm and c = 699.34(8) pm) show a good agreement to them of the PXRD experiment. The charge of the samarium cations in the named compounds was calculated by bond-valence calculations [6] and unambiguously led to Sm²⁺ in SmF₂ and SmFCl, but to Sm³⁺ in SmFO. The measured powder pattern of the three-component mixture can be seen in Figure 1 together with single crystals of SmF₂ and SmFCl and all three unit cells of the title compounds.

Figure 1. Rietveld refinement of a SmF₂–SmFCl–SmFO mixture (70:5:25) by using Cu-Kα radiation (bottom), unit cells of SmF₂, SmFO and SmFCl (left) and single crystals of SmF₂ and SmFCl (top right).

[1] E. Catalano, R. G. Bedford, V. G. Silveira, H. H. Wickman, (1969) J. Phys. Chem. Solids 30, 1613. [2] T. Petzel, O. Greis, (1973) Z. Anorg. Allg. Chem. 396, 95. [3] O. Greis, (1978) J. Solid State Chem. 24, 227. [4] H. P. Beck, (1979) Z. Anorg. Allg. Chem. 451, 73. [5] N. C. Baenziger, J. R. Holden, G. E. Knudson, A. I. Popov, (1950) Atti Accad. Ligur. Sci. 7, 44. [6] N. E. Brese, M. O'Keeffe, (1991) Acta Crystallogr. B47, 192.

Twinning prevents straightforward crystal structure analyses. Especially, for twinning by merohedry, the existence of the twinning can never be detected during the measurement. Although this kind of twinning is not a rare case for simpler crystals, a typical example of which is the Dauphine law twin of quartz, twinning by merohedry observed in the crystals of more complex compounds has been less commonly known. We have recently analyzed crystals of polyoxometalates and related compounds that show twinning by merohedry. Examples include a series of compounds of SiW₁₂O₄₀⁴⁻ with lanthanide elements that crystallize in the space group type P4₂/m. Another example is a crystal of a silver coordination compound that crystallizes in the space group type of I4₁/a. Details of the analyses of these crystal structures will be presented.

Acknowledgement: The work is supported by JSPS core-to-core program and JSPS KAKENHI 19K05510.

N,N’-diphenyl formamidines have E and Z isomers with either synperiplanar or antiperiplanar conformational combinations around the formamidine –N=C(H)–N(H)– backbone. The molecular isomerism of N,N’-diphenyl formamidines have been extensively studied in solution state [1]. However, no reports have been found regarding their preferred isomerism in the solid state. In this work, the steric and electronic effects on the molecular isomerism of eight N,N’-diphenyl formamidine derivatives in solid-state were evaluated using X-ray crystallography [2]. The eight compounds constitute of four symmetrical and four unsymmetrical N,N'-diphenyl formamidine derivatives having a general formula of [N-(Ar),N′-(Ar′)] where (Ar = Ar′) and (Ar ≠ Ar′), respectively. Five of the compounds were characterized using single crystal X-ray diffraction. Solid-state structure analysis showed two molecular isomers, E_syn and E_anti, and they form distinct classical hydrogen bonding patterns (Fig. 1). Correlations between molecular isomerism, pairwise interaction energies, infrared spectroscopy and thermal properties were established in this work. This provides a unique crystal engineering approach to predicting the isomerism of N,N’-diphenyl formamidines without crystal structure determination.

Salt and cocrystal have been reported as two main classes of the solid phase to modulate the physicochemical properties of the active pharmaceutical ingredient (API), such as increased solubility, dissolution rate, and stability. Structurally, cocrystals are composed of neutral compounds; meanwhile, salt combines the ionic components. Each solid form offers advantages and can be tailormade to gain a specific purpose. For example, cocrystals may enhance solubility and dissolution rate, but some may also decrease those parameters. On the other hand, alkaline–drug salt generally has a higher solubility than the parent drug. But how if the alkaline salt drug is combined with a similar coformer? Can it produce a salt cocrystal with superior performance?

This poster presents the development of the two most used NSAIDs (non-steroidal anti-inflammatory drugs): diclofenac acid and mefenamic acid, with a scheme shown in Fig. 1. Previously, we have found and developed neutral cocrystals of diclofenac-L-proline [1] and mefenamic - nicotinamide [2]. However, the solubility was still lower than their alkaline salt forms. Hereafter, we attempted to combine the alkaline salt with a similar coformer to modulate its performance. As a result, we successfully produced the new salt cocrystals of diclofenac and mefenamic, characterized using DSC/TG, PXRD, and structurally determined using SCXRD entirely.

First, sodium and potassium diclofenac proline (NDP/KDP) were isomorphous and had two hydrate forms, monohydrate and tetrahydrate phases [3,4]. Meanwhile, sodium mefenamate nicotinamide (SMN) constructed the hemihydrate and monohydrate forms [5]. The water's existence was crucial to stabilizing the lattice structure, coordinated with the alkaline elements and hydrogen-bonded with the other component. After that, all salt cocrystals were proven to modulate the physicochemical properties of the parent drugs, superior to the neutral cocrystals. The solubility and dissolution rate were increased by combining Na⁺ and the soluble coformer. Furthermore, the lower hydrate forms showed a higher solubility, dissolution rate, and stability than the counterpart phases. NDP monohydrate and SMN hemihydrate increased the solubility of the starting alkaline salts by 3.5 and 1.5 folds or ten to a hundred times the acid parent drug’s solubility, respectively. Finally, the powder properties of both new multi-components also were better than the parent and salt drugs. In conclusion, salt cocrystallization is a promising technique to improve the NSAIDs performance and can be developed further for the dosage form formulation.

Figure 1: Salt cocrystal development of diclofenac acid and mefenamic acid.

References:

[1] Nugrahani, I., Utami, D., Ibrahim, S., Nugraha, Y.P., Uekusa, H. (2018). Eur. J. Pharm. Sci. 117, 168.

[2] Utami, D.W.I., Nugrahani, I., Ibrahim, S. (2017). Asian J. Pharm. Clin. Res. 10, 135.

[3] Nugrahani, I., Kumalasari, R.A., Auli, W.N., Horikawa, A., Uekusa, H. (2020). Pharmaceutics 12, 690.

[4] Nugrahani, I., Komara, S.W., Horikawa, A., Uekusa, H. (2020). J. Pharm. Sci.109, 3423.

[5] Nugrahani, I., Fisandra, F., Horikawa, A., Uekusa, H. (2021). J. Pharm. Sci. available online 6 June 2021.

Keywords: salt cocrystal, solubility, dissolution, sodium/potassium diclofenac proline, sodium mefenamate nicotinamide.

We gratefully thank the Research and Innovation Institution, Educational Ministry of Republic Indonesia for the funding and Uekusa’s Laboratory Tokyo Institute of Technology for the research collaboration.

Copper (II) complexes with NSAIDs are interesting as potential drugs with different biological activity such as potential anticancer and antioxidant activities (superoxide dismutase mimicking, radical scavenging and soybean lipoxygenase inhibition).^1-3

A series of five copper(II) fenamate complexes with N,N-diethylnicotinamide ligand (den) of formula [Cu(nif)₂(den)₂] (flu = flufenamate) (1), [Cu(clo)₂(den)₂] (clo = clonixinate) (2), [Cu(flu)₂(den)₂(H₂O)₂] (flu = flufenamate) (3), [Cu(tol)₂(den)₂(H₂O)₂] (tol = tolfenamate) (4) and [Cu(mef)₂(den)₂(H₂O)₂] (mef = mefenamate) (5) have been synthesized and structural characterized. The crystal structures of five complexes (1-5) were refined using the Hirshfeld Atom Refinement model (HAR) and Hirshfeld surface analysis have been also made.

[1] J.E. Weder, et al., Coord. Chem. Rev. 2002, 232, 95.

[2] C.N. Banti, S.K. Hadjikakou, Eur. J. Inorg. Chem. 2016, 3048.

[3] G. Psomas, Coord. Chem. Rev. 2020, 412, 213259.