Kinetic control is an upcoming method for producing a wide variety of desired functional structures [1, 2]. Thermodynamic assembly allows the reaction system to achieve equilibrium, thus forming thermodynamically stable compounds, whereas kinetic assembly traps metastable states via fast crystallization at low temperatures and at high concentrations. However, rapid crystallization causes difficulties with ab initio structure determination by X-ray diffraction, since the main products are crystalline powders rather than single crystals [1, 3].

We found that in the row of rare-earth cyamelurates three structural types exist. Room temperature synthesis (22 – 25 °C) leads to the formation of compounds [M(H₂O)₇C₆N₇O₃] (M = Y, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er), which we consider as a result of kinetic control. Synthesis with heating up to 100 °C yields thermodynamically more stable [M(H₂O)₄C₆N₇O₃]_n·nH₂O (M = Y, Ho, Er, Tm, Yb, Lu) and [M(H₂O)₅C₆N₇O₃]_n (M = Pr, Nd). Structures of erbium cyamelurates (Fig. 1) and neodymium cyamelurate were solved using data of the powder XRD.

Figure 1. Reaction pathway in formation of kinetic and thermodynamic product and structures of erbium cyamelurate, obtained at room temperature (left) and at 100 °C (right). Hydrogens are not shown.

Thermodynamic products have denser structures compared to kinetic products. In synthesized at increased temperature erbium and neodymium cyamelurates polymeric chains exist due to the fact that the cyamelurate anion acts as a bridging ligand (Fig.1, right). Kinetically trapped erbium cyamelurate, in contrast, consists of individual complex molecules [Er(H₂O)₇C₆N₇O₃] (Fig.1, left). Probably, steric difficulties caused a decrease in the coordination number of erbium from 9 to 8 in the thermodynamic product. The coordination number of neodymium remains equal to 9 in both types of compounds.

The statement that the most stable product also can form the fastest, indicating that the kinetic and the thermodynamic product is one and the same [4], is confirmed by synthesized at elevated temperatures Sm, Eu, Gd, Tb, Dy cyamelurates with a similar structure as in the case of products obtained at room temperature.

[1] Ohtsu, H., & Kawano, M. (2017). Chem. Commun. 53, 8818.

[2] Yan, Y., Huang, J. & Tang, B. Z. (2016). Chem. Commun. 52, 11870.

[3] Marti-Rujas, J. & Kawano, M. (2013). Acc. Chem. Res. 46, 493.

[4] Ji, Q., Lirag, R. C. & Miljanic, O. S. (2014). Chem. Soc. Rev . 43, 1873.

Keywords: IUCr2020; cyamelurates; crystal structure; kinetic control; thermodynamic control

This work is supported by grant 20-08-00097 from the Russian Foundation for Basic Research.

Carbon framework of graphite structure can host alkali metals between layers forming graphite intercalation compounds (GIC). In the case of GICs with multiple layers separated by metallic layer, one can imagine graphite-to diamond transformation in carbon framework, leading to “diamond intercalation compounds” (DIC). The design of such material(s) was the purpose of our work.

GIC with metals such as Li, Na and K form different compositions (and crystal structures) are produced by stacking along c-axis of metal (Me) and n carbon (A, B or C) layers. The n number indicate the stage of intercalation. Typically ordered compounds are obtained for n = 1 to 6 with various stacking sequences depending on metals: n = 1 for MeAMeB, n = 2 for MeABMeBAMeCA, n = 3 for MeABCMeBCAMeCAB, etc. Experiments show that both high pressure and high temperature leads to increasing n. We will discuss the structural features of GIC, the XRD, Raman and other structurally related data, as well as corresponding DIC structurally related to GIC. The pressure and temperature range of formation of DICs from GICs coincide with industrially accessible conditions, that allows considering them as new promising materials. We have also shown that powder XRD is a method o fchoice for study of such transformations.

Compounding of polystyrene (PS) with tetramethylsilyl cellulose (TMSi-Cell) and an organically modified montmorillonite (OMMMT) was carried out in two different ways. In the first way the PS of MW = 49000 and Mn = 32000 was solved in toluene, than mixed with the nanocomposite dispersion of TMSi-Cell/OM-MMT (10.5 %) in toluene and dried in an oven at 380 mbar/40°C for 20 hours. In the second way the bulk polymerization of PS was tried as a way to obtain PS/TMSi-Cell/OM-MMT nanocomposite. The polymerization followed in a mixture of styrene with TMSi-Cell/OM-MMT (10.5 %) in an oil bath at 80 °C for 4 hours and at 120 °C for 16 hours. Nanocomposites of TMSi-Cell/OM-MMT were firstly prepared by precipitation from toluene experimenting concentrations from 10.5 % to 29.35 % of OM-MMT to TMSi-Cell. The thermal properties of the nanocomposites, were investigated by thermogravimetry and the morphologies of these nanocomposites were evaluated through X-ray diffraction. The 10.50 % OMMMT/TMSi-Cell nanocomposite showed a completely exfoliated morphology. PS/TMSi-Cell/OM-MMT mixtures were characterized by X-Ray Diffraction, Thermogravimetry and Differential Scanning Calorimetry. Differences in the degradation temperature compared to pure PS show compounding.

Hybrid organic-inorganic compounds are receiving considerable attention in recent years due to the possibility of combining the different characteristics of the components to get unusual and enormous variety of interesting structural topologies and wide potential applications in the fields of catalysis, non-linear optics, sensors, magnetism and molecular recognition ^[1]. During our investigation, we synthesized three new hybrid organic-inorganic compounds of dapsone with antibacterial and second-order nonlinear optical properties ^[2]. The structural study and Hirshfeld surface analysis allowed us to establish the importance of hydrogen bond and intermolecular interaction in the crystal packing.and their role in the NLO properties.

In the porous material Science, Metal Organic framework (MOF) are intensely studied, among other qualities, for has the tailorable pores suitable for applications like gas separation and storage, catalysis and so on. . For definition the MOF’s are porous coordination networks, with void pores, formed by metallic sites organized in secondary building units (SBU) connected by organic linkers. The geometrical variety of the SBU’s result in different topologies and a variety of pores with different sizes (from micro- to mesopores). In particular, the MeMOF-74 (Me=Co, Zn, Mn, Mg e Ni) has a hexagonal structure with unidimensional porosity, where the metal cations are connected to 6 oxygens exhibiting a SBU with straight helical form. In this work, high quality powder X ray diffraction pattern of MeMOF74 (Me= Co, Ni, Zn, Mg e Mn) were investigated using the Rietveld refinement method. This analysis was used to compare the influence of metal on the local geometry of secondary building units (SBU) and to study the influence of bimetallic sites on the structure.

The propionic acid is the first simple carboxylic acid in the series of simple carboxylic acids starting from the formate where the hydrophobic character prevails. The propanoates make a text-book example of structures in which hydrophilic/cation-oxygen interactions and hydrophobic interactions (between the ethyl groups) are combined resulting in a rich variety of structures.

The structural motifs thus result in layer-like strutures, columnar structures or isolated clusters in which the inner part consists of a structural part where the hydrophilic interactions prevail in contrast to an outer part where the hydrophobic interaction dominate.

The structures are affected by the positional disorder of the ethyl chains.

Water inclusion into the structures is quite frequent which stabilizes the hydrophilic interactions in the structures.

Acknowledgments: This work was supported by the Czech Science Foundation (Project No. 19-28594X). Dr. Ivana Císařová from the Faculty of Science of the Charles University in Prague is thanked for the measurement of some samples

Porous coordination polymers (PCPs) with flexible framework have attracted much attention, because some of them have a high selective adsorption ability for specific gas molecules and a wide range of applications, e.g. gas separation, gas purification is expected. However, the mechanism of selective adsorption in PCPs is not unveiled. Crystal structure information of flexible framework and gas molecules is indispensable for clear understanding of the gas adsorption phenomena in PCPs.

In past decades, crystal structures of desorption and adsorption phases of PCPs were revealed by in-situ synchrotron powder diffraction measurements. Not only the framework but also the position and orientation of adsorbed gas molecules led to a deep understanding of the static gas adsorption state [1]. On the other hand, it is very interesting to know how the framework and/or pore surface of PCPs recognize gas molecules during the gas adsorption process. It will contribute to not only the development of PCPs with superior gas separation ability, but also the understanding of the whole gas adsorption process. However, there are few studies on the state at the beginning of gas adsorption process into PCPs. The dynamic structural information, which is the structural change of the gas molecules and framework in the overall gas adsorption process, will make it possible for us to gain the knowledge how gas molecules begin to interact with the pore surface and subsequently diffuse into the pores. In general, it is not so easy to elucidate the information on the early stage of the gas adsorption process by conventional measurement methods such as the adsorption isotherm. In order to obtain the dynamic structural information, we performed time-resolved synchrotron X-ray powder diffraction (XRPD) experiment in the gas adsorption process on PCPs.

In this study, XRPD measurements under gas pressure control were performed using the remote gas and vaper pressure control (RGVPC) system at beamline BL02B2 of SPring-8. The RGVPC system can control the gas and vaper pressure in online, and synchronize it with the powder diffraction data acquisition to obtain time-resolved data [2]. Using this system, a fixed amount of gas can immediately be introduced to a powder sample in a glass capillary (gas-shot mode). In the time-resolved XRPD measurement, the exposure time was set to be 1 s for each measurement. Previous to the measurement, powder samples are heated evacuating to remove guest molecules in the pore. After that, the temperature is lowered to 195 K and gas-shot measurement for CO₂ gas started. Such measurements were performed by changing gas pressure and temperature. Figure 1 shows one of the changes of XRPD pattern of gas-shot measurement for CO₂ gas adsorption in CPL-1 [3]. It was found that the CO₂ adsorption completed within a few tens of seconds after the introduction of gas. In order to investigate the change of crystal lattice during this adsorption process, Le Bail fitting was performed for each time-resolved XRPD data. The speed changes of the lattice parameters were slightly different for each axis. Furthermore, the transformed fraction from desorption to adsorption phase was derived from the change of integrated intensity of specific diffraction peak. The results show that the transformed fraction strongly depends on the gas pressure and temperature. Its fraction might be related with the dimensionality of gas diffusion into the pores. These data were analyzed using kinetic method such as the Kolmogorov-Johnson-Mehl-Avrami (KJMS) theory [4,5]. In the presentation, we will discuss the kinetics and the structural change in gas adsorption process in comparison with PCPs with different pore size and shape.

[1] Kitaura, R., Kitagawa, S., Kubota, Y., Kobayashi T.C., Kindo, K., Mita, Y., Matsuo, A., Kobayashi, M., Chang, H., Ozawa, T., Suzuki, M., Sakata, M. & Takata, M. (2002). Science 298, 2358-2361.

[2] Kawaguchi, S., Takemoto, M, Tanaka, H., Hiraide, S., Sugimoto, K., & Kubota, Y. (2020). J. Synchrotron Rad. 27, 616-624.

[3] Kondo, M., Okubo, T., Asami, A., Noro, S., Yoshitomi, T., Kitagawa, S., Ishii, T., Matsuzaka, H., & Seki, K. (1999). Angew. Chem. Int. Ed. 38, 140-143.

[4] Avrami, M. (1939). J. Chem. Phys. 7, 1103–1112.

[5] Kruger, P. (1993). J. Phys. Chem. Solids 54, 1549-1555.

We reported multi-interactive ligand, 2,5,8-tri(4’-pyridyl)-1,3,4,6,7,9-hexaazaphenalenate (4-TPHAP^-) with topologically isolated p-orbitals on an interactive HAP skeleton, can trap metastable states via intermolecular interactions during network formation. Kinetic assembly of porous coordination networks create interactive sites in the pore, which can trap guest molecules and visualize their structure, for example small reactive sulphur allotropes, and conversion.

In this study, a lower symmetry derivative of the HAP ligand containing 3-pyridyl groups (3-TPHAP^-) was developed. The purpose of this ligand was to obtain network structures with minimized dynamic motion compared to 4-TPHAP^- based networks. In 3-TPHAP^-, the pyridine ring rotation becomes suppressed after coordination to a metal centre. The lack of rotational motion may significantly influence the guest encapsulation behaviour in the resultant structures. This ligand was prepared by a one-pot condensation reaction. It was successfully reacted with a Co²⁺ salt and 1,4-benzenedicarboxylic acid co-ligand to give a porous coordination network. In the structure, HAP skeleton interacts with water to form an internal hydrogen bonding network, allowing to reveal the entire pore space by single crystal X-ray diffraction (SXRD). The network structure consists of dimeric Co clusters featuring labile sites occupied by solvent molecules. Several guest molecules, namely anthracene, triphenylene and iodine, were incorporated inside the network. The resultant encapsulated structures were elucidated by SXRD revealing unusual host-guest interactions with a subtle structure modulation.

The development of innovative environmentally friendly catalysts is of crucial importance for the establishment of a new sustainable chemical industry. The immobilization of the catalysts on a support can solve problems of selectivity and activity. We propose a scaffold based on Metal Organic Frameworks (MOFs). Under appropriate conditions they can be assembled into a porous material on which we can immobilize catalyst, making possible its recovery/reuse at the end of the process. The advantages of these scaffolds are clear: uniform, reproducible and controllable manufacture and the possibility to engineer the linkers. As a consequence, we can control and personalize the whole network structure. By using these networks as scaffolds for the immobilization of the catalysts, MOFs turn into actual nanoreactors. Our proposed nanoreactors will be designed and synthesized according to modular principles (based on isoreticular synthesis ^[1]). The desired MOFs will have to have some specific characteristics to be used as scaffold for catalyst: pore size in the range of mesopores (≥ 6nm), 1-D hexagonal structure (channel-like) to help the diffusion of reactants/products^[2] and easy/fast/cheap to synthesize in its organic components. In order to achieve the aim of the project, an easy and fast strategy has been optimized for the synthesis of novel tritopic and tetratopic organic linkers (Figure 1). Conventionally, the synthesis of organic linkers is based on the use of the well-known Suzuki coupling. This approach would require extra synthetic steps. Direct arylation ^[3], is the coupling of aryl halides with catalytically activated aryl C-H bonds. Therefore, the number of synthetic steps is reduced. The library of long star-shaped linkers is currently used for the synthesis of Zr-, La-, In- and Ga-based MOFs, and the first results will be presented here^[4].

[1] Deng, H.; et al. Science 2012, 336 (6084), 1018-1023

[2] Čejka, Morris, Nachtigall; RSC Catalysis Series No. 28 (2017)

[3] Yabo Li et al. J. Org. Chem. 2014, 79, 2890−2897

[4] Fucci, Vande Velde; Faraday Discussions, 2021, accepted.

Metal-organic frameworks (MOFs) have been used for many different applications over the last decades. Taking advantage of their resourcefulness, we have been exploring the possibility of designing MOFs using nalidixic acid as linker towards enhanced antibacterial activity. Nalidixic acid is a synthetic quinolone antibiotic used for the treatment of urinary tract infections caused by gram-negative microorganisms. We have already demonstrated that the direct coordination of this antibiotic to biocompatible metals, yielding what we call antibiotic coordination frameworks (ACFs), is a viable pathway to induce changes in important properties such as solubility. One further advantage is that synergistic effects of the metal often lead to an increase in the efficiency against different bacteria, including E. Coli.[1]

Herein we disclose a nalidixic acid-Ca(II) complex and a three new MOFs resulting from the coordination of nalidixic acid and other generally regarded as safe organic ligands (such as salicylic, nicotinic and isonicotinic acids) to Ca(II) centers. The novel compounds were synthesized by mechanochemistry,[2] ensuring the sustainability of the synthetic process. These new structures offer multiple possibilities for future applications arising from the combination of the antimicrobial activity of the ligand and the calcium important role in the human body.

Acknowledgements: Authors acknowledge Fundação para a Ciência e a Tecnologia (FCT, Portugal) (projects UID/QUI/00100/2019 and PTDC/QUI-OUT/30988/2017 and contracts under DL No. 57/2016 regulation and CEECIND/00283/2018) and FEDER, Portugal 2020 and Lisboa2020 for funding (project LISBOA-01-0145-FEDER-030988).

References:

1. a) V. André, F. Galego, M. Martins, Cryst. Growth Des. 2018, 18(4), 2067. b) V. André, A. Silva, A. Fernandes, R. Frade, P. Rijo, C. Garcia, A. M. M. Antunes, J. Rocha, M. T. Duarte, ACS Applied Bio Materials 2019, 2(6), 2347. c) C. Bravo, F. Galego, V. André, CrystEngComm 2019, 21, 7199-7203.

2. J. G. Hernández, I. Halasz, D. Crawford, M. Krupicka, M. Baláž, V. André, L. Vella-Zarb, A. Niidu, F. García, L. Maini, E. Colacino, European Journal of Organic Chemistry, 2020, 8-9.

Porous materials such as zeolites have made an indispensable impact in day-to-day life to commercial applications. The structural rigidity created by primary [SiO₄]^4- and [AlO₄]^3- units and associated with the framework stability are one of the prime criteria for its vast applications. At times the rigidity of the structure, difficulties in functional properties and nuances of the synthetic procedure.¹ Alternatively, materials made of coordination polymers (CPs) or metal-organic frameworks (MOFs) have gained enormous attention due to their simplicity in preparation, structural diversity, and the applications in gas-adsorption, separation of small molecules, catalysis, sensing of small molecules to hazardous materials, drug delivery, nonlinear optics, proton conductivity, and other biomedical related processes. These prominences of MOFs/CPs in the last three decades have stimulated a colossal amount of research interests in the study of frameworks having multifunctional properties. The diversity in applications is mainly attributed to the robustness of the MOFs against hydro- and thermal stability under different pH solutions besides maintaining the crystallinity and their porosity. In addition, in the presence of Lewis acidic/basic sites, these MOFs were potentially used as catalysts for various organic transformations.^1-3 In this talk, the preparations of some mixed metal oxides and CPs/MOFs derived imidazole-based carboxylic acid systems and metal substrates will be presented. In addition, the properties of these systems in the areas of gas adsorption, luminescence-based sensing/remediation of hazardous materials, and catalysis will be presented.⁴

Figure: SBU (left) and 3D cuboctahedral structure of Indium MOF

References:

1. (a) Kreno, L. E., Leong, K., Farha, O. K., Allendorf, M., Van Duyne, R. P., & Hupp, J. T. (2012) Chem. Rev. 112, 1105. (b) Kitagawa, S., & Kitaura, R.; Noro, S. (2004) Angew. Chem., Int. Ed. 43, 2334.

2. (a) Huang, Y.-B., Liang, J., Wang, X.-S., & Cao, R. (2017) Chem. Soc. Rev. 46, 126. (b) Zhou, H.-C., Long, J. R., & Yaghi, O. M. (2012) Chem. Rev. 112, 673.

3. (a) Wang, J., Liu, X., & Feng, X. (2011) Chem. Rev. 111, 6947. (b) Reinares-Fisac, D., Aguirre-Díaz, L. M., Iglesias, M., Snejko, N., Gutiérrez-Puebla, E., Monge, M. Á., & Gándara, F. A. (2016) J. Am. Chem. Soc. 138, 9089.

4. (a) Penke. Y. K., Anantharaman, G., Ramkumar, J., & Kar, K. K. (2019) J. Hazard. Mater. 354, 519. (b) Penke. Y. K., Anantharaman, G., Ramkumar, J., & Kar, K. K. (2017) ACS appl. Mater. Interfaces. 9, 11587. (c) Penke, Y. K., Anantharaman, G., Ramkumar, J., & Kar, K. K. (2015) RSC Adv., 6, 55608.

5. (a) Tripathi, S., & Anantharaman, G. (2015) CrystEngComm, 17, 2754. (b) Mohapatra, C., Tripathi, S., Chandrasekhar, V., & Anantharaman, G. (2014) Cryst. Growth. Des., 14, 3182. (c) Sachan, S. K., & Anantharaman, G. (2021) Inorg. Chem., 60, 9238.

Authors thank Science and Engineering Research Board (SERB, India, No. SB/S1/IC-49/2012), for funding. Authors also thank CSIR (SKS & ST), & IIT Kanpur (NS & RS) for the doctoral fellowship, and the infrastructural facilities (IITK).

The oxygen reduction reaction (ORR) is a common process in a variety of electrochemical devices, like fuel cells and metal air batteries. The sluggish kinetics of the ORR require an electrocatalyst to pass this bottleneck.^[1] Currently, the most used catalytical systems are platinum-based, with several drawbacks, such as the high cost, low availability, and deactivation by CO poisoning.^[2] Efforts are made to develop efficient, durable and low cost catalysts to promote the commercialization of fuel cells.

Non-precious metal catalysts are promising candidates for efficient ORR catalysis. It has been shown that pyrolyzing metal organic frameworks (MOFs) under inert conditions yields carbon-rich materials, with evenly distributed metal sites, which possess promising electrocatalytic activity.^[3] One widely used type of MOF as ORR catalyst precursors is the zeolitic imidazole framework (ZIF) where metal cations are linked through imidazole-based ligands. Their porous nature is partially retained after carbonization, making MOFs very suitable precursor materials.

Herein we report the mechanochemical synthesis and structural analysis of Co-doped ZIF-8 (Zn), as well as two polymorphs (dense and prorous) of fluorinated Co-doped CF₃-ZIF-8 (Zn). The samples showed electrochemical performance comparable to platinum after carbonization for 1 h at temperatures ranging between 850 – 1000°C.

Metal-organic frameworks (MOFs) have been recently known as novel precursors in nanomaterial synthesis. To understand the mechanism behind the phase transformation in atomic scale, we apply in-situ X-ray pair-distribution analysis to monitor the whole process, from distortion, destabilization, partial reduction, to the eventual nanoparticle formation and defect evolution of a series of bimetallic MOFs PCN-250. These MOFs with different trimeric node composition (Fe₃, Fe₂Co, and Fe₂Ni) allow us to control the structure, chemistry, and defect of resulting nanoparticles. Notably, we found selective reduction of Ni from the node with defect-rich frameworks retained. This can be a new route for future MOFs crystal engineering.