Hollow molecular structures capable of guest inclusion represent an area of raising interest and lie at the forefront of the modern supramolecular chemistry.[1,2] Originally studied in solution, this concept has been extended in the solid-state, after the pioneering work on the “crystalline sponge method” (CSM). [3] The CSM primary application has been the unambiguous structural determination via SC-XRD of a single analyte encapsulated inside a porous MOF. However, as the host-guest systems often show severe disorder, their reliable crystallographic determination is very demanding [1,2] thus the dynamics of the guest entering and the formation of nanoconfined molecular aggregates has not been in the spotlight yet.

We extended the concept of the CSM stepwisely monitoring the structural evolution of nanoconfined supramolecular aggregates of guest molecules with the concomitant displacement of pristine DMF inside the cavities of a novel flexible MOF, PUM168. Furthermore, we correlated this phenomenon to the structural reorganization of the host framework, elucidating the dynamic interplay between the container and the content. [4] In order to deeply understand the “physiology” of PUM168 breathing during the guest uptake, we focused our attention on the three main actors involved in the play: i) the MOF structure, ii) the leaving DMF molecules trapped during the synthesis of the MOF and iii) the incoming guest molecules uptaken during the soaking process. [5]

The fate of each actor influences and is influenced by the other two characters, in a play that shows how the structure of the framework changes in the response of the guest positioning and composition. [5]

Interactive pores in porous coordination networks play a key role in trapping unstable species, chemical transformation, and so on . We reported porous coordination networks prepared by kinetic assembly which can be used to produce interactive pores. The interactive pore can be used for I₂ chemisorption and chemical transformation of small sulfur allotropes, from S₂ to bent-S₃ via cyclo-S₃. We performed selective formation of porous coordination networks kinetically/thermodynamically from CuI cluster and rigid T_d symmetry ligand, 4-TPPM (tetra-4-(4-pyridyl)phenylmethane), by changing cooling ratio of the hot DMSO solution of the mixture. Because the interactive pore is the key component to create functionality, it is required to extend the availability of interactive pores. Such interactive pores can be modified by changing metal source (clusters) and ligand coordination geometry. Here we report the kinetic assembly of porous coordination using Cu-Halide clusters and several pyridine-type ligands (Figure 1) to generate several interactive pore sites; we report new kinetic network formation using 4-TPPM and CuX cluster and the dynamic structural change of the kinetic network to produce highly luminescence coordination networks and flexible network formation using 3-TPPM and CuI cluster to show dual interactive sites showing iodide interactive pore sites and Cu pseudo-open metal sites.

When we performed kinetic/thermodynamic assembly using [Cu₄Br₄(PPh₃)₄] and 4-TPPM, we obtained coordination network composed of Cu₂Br₂ dimer and 4-TPPM as kinetic network and that composed of CuBr helical chain and 4-TPPM as thermodynamic network. When we heat the kinetic network at 573 K, it turned to luminescent crystalline powder. Both single crystal analysis and Rietveld refinement of PXRD indicates the transformation to the network composed of Cu⁺ connectors and 4-TPPM linkers with CuBr₂^- guests. The high quantum yield was obtained for this network (13%). We clarified that the electronic transitions in this network include TSCT in addition to the typical metal–ligand charge transfer (MLCT) observed in conventional Cu complexes. The atomic coordinates of the molecules determined from X-ray structure analysis enabled a clear understanding of the nature of the TSCT transitions.

When we performed kinetic/thermodynamic assembly using [Cu₄I₄(PPh₃)₄] and 3-TPPM, we obtained coordination network composed of Cu₂I₂ dimer and 3-TPPM as kinetic network and that composed of CuI helical chain and 3-TPPM as thermodynamic network. Using 3-TPPM, rotation motion of pyridine ring was restricted. Interestingly the thermodynamic network, CuI helical network shows 2I₂ chemisorption to make chemical bond with iodide in the interactive pore and Cu in the network so that Cu act as pseudo-open metal sites.

Iron fluoride (FeF₃.nH₂O) shows high capacity as cathode material for lithium-ion batteries combined to low toxicity and low cost. The water content of iron fluoride has been shown to be of prime importance in the performances of the cathode. So far, the various synthesis route doesn’t allow for a precise water content control, especially on the low amount regime which is the most interesting range of composition [1]. In addition, CrF₃ has been shown to increase significantly the conductivity of LiF film [2]. Consequently, it is of interest to look for the in-situ formation of the various MF_3-x(OH)_x.nH₂O phases (M = Cr, Fe).

In this contribution, we report on the in-situ formation of MF_3-x(OH)_x.nH₂O (M = Fe, Cr) phases using self-generated atmosphere. Traditionally, the heating MF₃.3H₂O in open air results in the full oxidation and decomposition of the fluorides giving rise to nano based oxides. Here, we make use of self-generated atmosphere to control the precise crystal chemistry of those phases upon heating preventing full oxidation at mild temperatures while stabilizing new phases relevant for battery applications.

Some of the results are presented in Figure 1 about the FeF_3-x(OH)_x.nH₂O phases. Precise controlled of the water content of the FeF_3-x(OH)_x.nH₂O series could be reached with n ranging from 1/3 to 0 with about 10 new pure phases. We demonstrate experimentally the initial assumption on the role played by the water in the stabilisation of the FeF₃.1/3H₂O phase, phase which is relevant for battery application [1]. In addition, the controlled in-situ decomposition of CrF₃.3H₂O led to the formation of a new CrF_3-x(OH)_x pyrochlore which was characterized structurally and magnetically. This work demonstrates the added value of in-situ experiment using self-generated atmosphere for synthetising new phases.

[1] Kim et al., (2010) Adv. Mater. 22, 5260; Ma et al. (2012), Energy Environ. Sci. 5, 8538.

[2] Tetsu O. (1984), Materials Research Bulletin 19, 451.

Investigations of long-lived reaction intermediates and metastable species generated upon external stimuli, such as light or heat, in chemical and biological systems are of upmost importance in the context of our understanding of the processes’ mechanisms and related phenomena. Linkage isomers can be formed by coordination compounds that contain ambidentate ligands capable of binding to a metal centre through various donor atoms. Such metastable species may exhibit lifetimes as long as hours or days and revert back to the ground state at elevated temperature. Thanks to their properties, photoswitchable materials may find various technological applications, including renewable energy solutions, biosensors or data storage.

The aim of this project was to thoroughly and systematically investigate conditions and dynamics of light-induced nitro group isomerisation reactions which occur in crystals of either designed or literature-reported 4th-row transition-metal complexes. The examined series of compounds consists of coordination compounds of nickel(II), copper(II) and cobalt(III). Metal centres in these systems are coordinated by the nitrite ligand and either (N,N,O) chelating species, NHC group, or amino ligands.

The studied complexes were thoroughly examined crystallographically, spectroscopically and computationally. In the case of Ni(II) and Co(III) nitro complexes partial conversion to metastable endo-nitrito isomers is achieved after irradiation of respective single crystal samples with adjusted UV-Vis LED light at temperatures above 100 K. The metastable-state form is usually stable up to relatively high temperatures, e.g. 240 K, while the maximum conversion may reach 100% for powder samples as indicated by solid-state IR measurements. Instead, copper systems analogous to the above-described nickel coordination compounds exist as the nitrito form in the ground state and work best at 10 K, whereas the metastable nitro form is usually stable only up to 60 K. Such behaviour makes them more difficult to be experimentally analysed and less applicable as functional photoactive materials.

In turn, a very significant 90% nitro-to-nitrito conversion was reported for single-crystals of the Ni(II) nitrite system [Ni(η⁵Cp)(IMes)(η¹-NO₂)]. The studied compound crystallizes with two symmetry-independent molecules comprising the asymmetric unit. Although the two moieties are geometrically very much alike, their behaviour upon irradiation or temperature appeared to be somewhat different depending on the exact experimental conditions. At 190 K the metastable species reverted back to their ground state.

Trinitrocobalt(III) coordination compounds constitute another interesting group of photoswitchable systems. For instance, Co(Me-dpt)(NO₂)₃ complex contains three different NO₂ groups in its molecule, which form different intermolecular interactions in the crystal structure, including hydrogen bonds (one is strongly bound, the second one moderately, whereas the third group does not participate in any hydrogen-bond-type contacts). After irradiating of the sample with the UV-Vis light only one of them switches to the nitrito linkage isomer, which shows the importance of crystal packing and intermolecular interactions effects.

X-ray acoustic interactions allowing to implement the control of X-ray parameters are widely studied. Among the numerous researches, it is possible to highlight the ability of controlling the spatial and energy spectrum of X-ray radiation [1] and the effect of redistribution of intensity between transmitted and diffracted beam [2]. This paper describes the implementation of a combination of these two possibilities.

Fast control of X-ray parameters, including scanning diffraction conditions and controlling by times much shorter than possibilities of traditional approaches, is a very relevant scientific task. It will be shown that overcoming of limitation of traditional approach, such as complex goniometric systems, possible by using of non-mechanical adaptive X-ray optic elements, such as X-ray acoustic resonators of longitudinal oscillations or bimorph piezo-actuators. It allows fast and precise variation of X-ray diffraction parameters, varying the angular position of the X-ray beam and controlling its wavelength. Description of schemes and elements for fast tuning of beam parameters will be given.

The effects of the redistribution of intensities between the diffracted and transmitted X-ray beams under the conditions of excitation of resonant acoustic thickness oscillations in quartz crystals were investigated. It has been established that the effect of increasing the intensity of a diffracted beam almost linearly depends on the amplitude of ultrasound (the FWHM of the rocking curves does not change at the same time) and is observed for all the studied reflexes.

The time characteristics of the observed effects upon excitation and relaxation of ultrasonic oscillations were investigated for the first time: the process of increasing intensity takes about 250 microseconds, then its oscillation is observed for about 1 millisecond, and the process of complete relaxation takes about 1.5 milliseconds.

Design of elements combining thickness and longitudinal oscillations are considered, several schemes of implementation are proposed. For the first time, the distributions of the FWHM and peak intensities of the rocking curves in a quartz resonator in case of the simultaneous excitation of longitudinal and thickness oscillations were measured. It is shown that these two types of oscillations do not have a significant mutual influence. Therefore, this combination can be used to create universal adaptive elements of x-ray optics, which allow controlling the angular position and intensity of the diffracted beam simultaneously. The effect of intensity redistribution in Potassium and Rubidium hydrogen phthalate crystals, which are emerging materials for creating a two-frequency element, was studied for the first time.

Some results and prospects of implementation of such methods and elements at synchrotron radiation as well as laboratory sources will be discussed.

[1] A.E. Blagov, M.V. Kovalchuk et al. JETP letters, t.128, 5 (11) (2005). P.893

[2] A.P. Mkrtchyan, M.A. Navasardyan, V.K. Mirzoyan. JTP letters, 8, 677 (1982)

The reported study was partially supported in the framework of the joint programs of the Russian Foundation for Basic Research (project № 18-52-05024 Arm_a and №18-32-20108 mol_a_ved) and Science Committee of Ministry of Education and Science of Armenia (project №18RF-142).

Photochromic compounds that change color reversibly by light irradiation are not only chemically interesting but are also expected to be applied to light control materials and optical storage media. So far, we have been investigating the reactivity and photochromism of salicylideneaniline derivatives and clarified that the factor that determines the photochromic characteristics is the crystal structure [1]. The cyanoalkyl cobaloxime complex crystal is a soft crystal that undergoes crystalline state photoisomerization by irradiation with visible light. This crystalline state reaction can be used to change the molecular packing, including the intermolecular interactions and the environment around the molecule, to control the reactivity of molecules in the crystal. According to this strategy, we synthesized cyanoalkyl cobaloxime complexes coordinated by photochromic compounds such as salicylideneaniline or spiropyran derivatives, which became a “dual photoreactive” complex crystal showing photoisomerization by visible light and photochromism with ultraviolet light irradiation (Fig.1). We achieved in situ control of the fading rate of these crystals by utilizing changes in the crystalline environment due to the isomerization reaction.

In this study, we synthesized three different g-cyanopropyl cobaloximes with N-(3,5-di-tert-butylsalicylidene)-3-aminopyridine(a), N-(3,5-dibromosalicylidene)-3-aminopyridine(b). and N-(5-methoxysalicylidene)-3-aminopyridine(c), and one b-cyanoethyl cobaloxime with (2-(3,3’-dimethyl-6-nitrospiro[chromene-2,2’-indolin]-l’yl)ethyl isonicotinate)(d). When the photoreactivity in the solid-state was investigated, it was confirmed that the photochromic reaction of the salicylideneaniline derivatives(a,b,c) proceeded by UV light irradiation while the photoisomerization of the g-cyanopropyl cobaloxime complex proceeded by visible light irradiation. Thus, we succeeded in obtaining a novel dual photoreactive complex crystal. After the photochromic reaction, the crystal showed colour fading to the original colour. The fading rate was found to become slower for a, c, or faster for b after the g-a isomerization reaction of the cyanopropyl group by visible light irradiation. To elucidate the fading rate change mechanism, we calculated the reaction cavity around the central part of the salicylideneaniline moiety, which would show the largest molecular shape change. For a and c, the cavity volume was reduced by the g-a isomerization, which made the movement of the atoms in the cavity more difficult, and as a result, the fading rate slowed down. In contrast, in b, the cavity volume and the fading rate increased by g-a isomerization [2]. Similarly, in the spiropyran complexes (d), we succeeded in the in situ control of the colour fading rate by visible light irradiation. For this case, the fading rate change mechanism was again rationalized by the cavity size around the spiropyran moiety [3].