Diarylethenes provide light-controllable generation of reactive species (such as Brønsted and Lewis acids) to trigger various processes with high spatial and temporal resolution. At the same time, the opposite light-induced deactivation has not been developed yet. A promising way to achieve such controllable "removal" of acidity is the introduction of a carboxyl group at one of the reactive carbons. To address this issue, we studied the irreversible photoreactions of the corresponding substrates in the diphenylethene and phenyloxazolylethene series. Indeed, exposure to UV light led to the irreversible elimination of the carboxyl group during transformation to phenanthrene or naphthalene products. The efficiency of this reaction, competing processes, and the reactivity of the related esters and salts are discussed. Our results show that the carboxyl group (or its derivatives) can serve as the leaving group in the photochemical reactions of diarylethenes, thus providing "photoswitching-off" of acidity.

The crystal molecular structure of the co-crystal of boric acid (BA) with triphenylphosphine oxide (TPO) 1:2, H3BO3 center dot 2Ph3PO, was determined by single-crystal X-ray diffraction. In the crystal, pairs of the boric acid molecules are connected to each other by hydrogen bonds, and each acid molecule forms two hydrogen bonds with the oxygen atoms of two triphenylphosphine oxide molecules. The crystal packing of the new complex was compared with the crystal packings of the known 1:1 complex of boric acid and triphenylphosphine oxide, and boric acid and triphenylphosphine oxide themselves. Also, the energetic preferences and densities of the co-formers (BA and TPO) were compared for their pure forms and co-crystals. It is shown that more tight crystal packing is not necessarily accompanied by higher stability.

Novel cobalt bis(dicarbollide) based terminal alkynes with charge-compensated group in a spacer were synthesized by the nucleophilic ring-opening reactions of cyclic oxonium derivatives of cobalt bis(dicarbollide) with N,N-dimethylbut-3-yn-1-amine. A series of zwitterionic conjugates of cobalt bis(dicarbollide) with BODIPY were synthesized using the copper(I)-catalyzed azide-alkyne cycloaddition reaction. The absorption-emission spectra of the synthesized fluorescent conjugates of cobalt bis(dicarbollide) with BODIPY were obtained and it was shown that the conjugation with the metallacarborane moiety weakens the fluorescence of the BODIPY core, nevertheless the conjugates can be used to track boron in living systems. A spectroscopic study of the interaction of selected fluorescent conjugate with BSA in a stationary mode was carried out. Non-cytotoxic zwitterionic conjugate of cobalt bis(dicarbollide) with BODIPY retained fluorescence during cellular uptake, an effect attributable to its affinity for albumin. Laser confocal microscopy study demonstrated distributed perinuclear accumulation of the conjugate in cells and the absence of pronounced colocalization of the substance and early endosomes, which indicates a successful accumulation and distribution of conjugate inside the cell. This study creates prerequisites for further research in the development of methods for synthesizing fluorescent boron neutron capture therapy (BNCT) agents with the BODIPY moiety.

Crystals with more than one molecule in the asymmetric unit (Z ' > 1) present a longstanding challenge for understanding the balance between molecular conformation, intermolecular interactions, and crystal stability. This work reports a detailed investigation of a 3-((3,3-dinitroazetidin-1-yl)diazenyl)-5-(trifluoromethyl)-1H-1,2,4-triazole that crystallizes in the triclinic space group P-1 with two Z ' = 2. The two molecules are formally enantiomers differing in the inversion of the azetidine nitrogen atom and exhibit distinct orientations of the nitro groups, yet they display remarkably similar molecular volumes and Hirshfeld surface characteristics. Using a combination of periodic DFT calculations, topological analysis within the Quantum Theory of Atoms in Molecules, and energy decomposition via the Interacting Quantum Atoms method, we examine the structural and energetic differences between the two independent molecules. The analysis reveals that the similarity in volumetric properties arises from a compensation between electronic deformation and electrostatic stabilization, rather than from geometric identity. The results highlight the role of the triazole and azetidine fragments in determining the energetic balance, while the nitro groups contribute mainly to the rigidity of the crystal packing. This case study provides deeper insight into the Z ' = 2 phenomenon and demonstrates the value of real-space electronic structure methods for unraveling compensation mechanisms in molecular crystals.

Solid-state photochromism is often suppressed in organic crystals by packing constraints. Herein, we report the coordination-driven activation of pronounced photochromism in a series of zinc(ii) complexes with N-substituted 4-amino-1,2,4-triazole ligands. X-ray crystallography shows that coordination to Zn(ii) disrupts the ligands' inherent intermolecular hydrogen bonds, locking them into a conformation favorable for excited-state intramolecular proton transfer (ESIPT). Diffuse reflectance spectroscopy confirmed UV-induced photochromism in four of the five synthesized complexes. A quantitative energy analysis of intermolecular interactions, combining Hirshfeld surface analysis and QTAIM, identified pi-pi stacking as the key modulator: the only non-photochromic complex in the series served as a key example, exhibiting the strongest stacking interactions. We conclude that metal coordination provides the structural prerequisite for ESIPT, while the specific supramolecular packing, particularly the strength of pi-pi stacking, ultimately gates the photochromic response. This work illustrates the potential of metal coordination as a tool for engineering photochromic behavior in crystalline materials.

The titled relationship is considered in this paper in terms of the (de)localization phenomenon and its emanation in the positional coordinate space. The similarity between the strength of bonding of a topological atom (in the sense of the population of the corresponding atomic surface) and the delocalization index is discussed. Based on the hypervirial theorem, a scalar one-particle field is suggested to visualize the consequences of (de)localization for the formation of bonding.

The preparation of multipurpose high-energy materials for space technologies remains a challenging task and such materials usually require special precautions and fine tunability of their functional properties. To unveil new opportunities en route to high-performance energetic materials, novel potential melt-castable explosives and energetic plasticizers incorporating a (1,2,3-triazolyl)furazan scaffold enriched with nitro and nitratomethyl explosophoric functionalities were synthesized. The successful implementation of the regiodivergent approach enabled the preparation of regioisomeric (nitratomethyltriazolyl)furazans that possessed significantly different physicochemical properties classifying the target materials as melt-castable substances or energetic plasticizers. Hirshfeld surface calculations supported by energy framework plots were also performed to better understand the relationship between the molecular structure and sensitivity. All the prepared (1,2,3-triazolyl)furazans show high nitrogen-oxygen contents (76-77%), good experimental densities (up to 1.72 g cm-3) and high positive enthalpies of formation (180-318 kJ mol-1) resulting in good detonation performances (D = 7.1-8.0 km s-1; P = 21-29 GPa). Overall, this work unveils novel strategies for the construction of balanced energetic melt-castable substances or plasticizers for various applications.

It is shown that the electronic virial-based correlation should be used to estimate bonding contributions to the rigidity of molecular vibrations in crystals.

A new approach for obtaining interacting quantum atoms-defined components of binding energy of intermolecular interactions, which bypasses the use of standard six-dimensional integrals and two-particle reduced density matrix (2-RDM) reconstruction, is proposed. To examine this approach, three datasets calculated within the density functional theory framework using the def2-TZVP basis have been explored. The first two, containing 53 weakly bound bimolecular associates and 13 molecular clusters taken from the crystal, were used in protocol refinement, and the third one containing other 20 bimolecular and three cluster systems served as a validation reference. In addition, to verify the performance of the proposed approach on an exact 2-RDM, calculations within the coupled cluster formalism were performed for part of the first set systems using the cc-pVTZ basis set. The process of optimization of the proposed parametric model is considered, and the role of various energy contributions in the formation of non-covalent interactions is discussed with regard to the obtained trends.

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Two new polymorphic forms of Ph2Te2–1,4-C6F4I2 cocrystals feature an unusual packing of Ph2Te2 molecules, which is typical for native Ph2Se2 but not Ph2Te2. This suggests the existence the yet unknown, Ph2Se2-like polymorph of Ph2Te2.

Novel 7-azidofurazano[3,4-d ][1-3]triazine 5-oxide was synthesized from 3-amino-4-(tetrazol-5-yl)furazan and nitronium salt. Its characterization including energetic properties is described.

The conditions for bromination of the methyl groups of dimethylglyoxime were found, and the resulting product, a 1,4-dioxane solvate of bis(bromomethyl)glyoxime, was used as a precursor for heterocyclizations involving cyclodehydration or oxidative cyclization of the oxime groups leading to the formation of furazan and furoxan rings, respectively.

An unusual reactivity of 9-iodo-nido-carborane [9-I-7,8-C2B9H11]- towards nucleophiles under strong basic conditions was revealed. The nucleophilic substitution of iodine with O- and N-nucleophiles results in [9-RO-7,8-C2B9H11]- (R = H, CH2CH2OMe) and [9-L-7,8-C2B9H11] (L = Py, NEt3, Me2NCH2CH2NMe2), respectively. Reaction of [9-I-7,8-C2B9H11]- with CoCl2 in 1,2-dimethoxyethane in the presence of t-BuOK, depending on the order of addition of the reagents, leads either to a diastereomeric mixture of diiodo derivatives cobalt bis(dicarbollide) rac-[4,4'-I2-3,3'-Co(1,2-C2B9H10)2]- and meso-[4,7'-I2-3,3'-Co(1,2-C2B9H10)2]- or to the corresponding mixture of 2-methoxyethoxy derivatives rac-[4,4'-(MeOCH2CH2O)2-3,3'-Co(1,2-C2B9H10)2]- and meso-[4,7'-(MeOCH2CH2O)2-3,3'-Co(1,2-C2B9H10)2]-. In the presence of accidental admixture of sodium thiosulfate, the reactions of 9-iodo-nido-carborane and 9-(2'-methoxyethoxy)-nido-carborane with CoCl2 in 1,2-dimethoxyethane were found to produce additionally unprecedented tricobalt tris(dicarbollide) cluster Na[4,4',4''-(MeOCH2CH2O)3-3,3',3''-Co3(μ3-O)(μ3-S)(1,2-C2B9H10)3], the central fragment of which is a trigonal bipyramid with apical oxygen and sulfur atoms, and the base is formed by the Co3 triangle flanked by three dicarbollide ligands. In addition, the 2-methoxyethoxy substituents of the dicarbollide ligands chelate the sodium cation in such a way that they form a helix whose rotation direction depends on the enantiomer of the parent ligand. Thus, in this case, induction of the helical chirality of the complex occurs due to the point chirality of the initial inorganic ligand. It is worth noting that in the case of symmetrically substituted 2-methoxyethoxy derivative of nido-carborane [10-MeOCH2CH2O-7,8-C2B9H11]- only formation of the corresponding cobalt bis(dicarbollide) complex [8,8'-(MeOCH2CH2O)2-3,3'-Co(1,2-C2B9H10)2]- was observed.

Number of novel charge-compensated rhodacarboranes with pyridinium group was synthesized and characterized. Synthesis of 16-electron 3,3-mu-(1',2'-C2B10H10-1',2'-S-2-)-4-Py-3,1,2-RhC2B9H10 was accompanying by formation of several products. They were isolated and identified as two diastereomers of unusual dirhodacarboranes which contain two sigma-carboranyl and one s-dithiolate ligands 3,3-mu(3)-(1',2'-C2B10H10-1',2'-S-2-)-(4-Py-3,1,2-RhC2B9H10)(2). Structure of the DD/LL-isomer was determined by single crystal X-ray diffraction. Reaction the 16-electron complex with trimethylphosphine leads to corresponding 18-electron complex 3-PMe3-3,3-mu-(1',2'-C2B10H10-1',2'-S-2-)-4-Py-3,1,2-RhC2B9H10. Its structure was also confirmed by single crystal X-ray diffraction.

It is well known that the densest molecular crystals formed by molecules consisting of C, H, N, O, and F atoms are those of polynitro compounds that do not and cannot participate in strong intermolecular interactions. At the same time, many “typical” organic crystals are also stabilized by weak intermolecular contacts, such as C–H···O(N), O(N)···π, H···H, and so forth. However, the density of such crystals is significantly lower. In this work, we report the synthesis and properties of 1,3,5-triazine derivatives containing both trinitromethyl and/or trinitroethoxy, as well as isopropoxy groups. It was shown by X-ray structural analysis and quantum chemistry calculations that the crystal structures of the obtained 1,3,5-triazine derivatives were stabilized by weak interactions only, such as NO2···NO2, O···π, C–H···O, C–H···N, and H···H contacts. The effects from various types of weak intermolecular contacts on crystal density were evaluated. No strong correlation was found between the energy of interactions, decrease of system volume caused by such interactions, and an increase in crystal density. It was demonstrated that crystal packing can be studied effectively by a recently proposed method via the analysis of ΔOED criterion describing the density increase of molecule and its fragments upon crystal formation from isolated molecules.

Dihalogens readily interact with trimethylamine-N-oxide under ambient conditions. Accordingly, herein, stable 1 : 1 adducts were obtained in the case of iodine chloride and iodine bromide. The crystal and molecular structure of the trimethylamine-N-oxide-iodine chloride adduct was solved. Furthermore, the geometry and electronic structure of the trimethylamine-N-oxide-dihalogen complexes were studied computationally. Only molecular ensembles were found in the global minimum for the 1 : 1 stoichiometry. The OMIDLINE HORIZONTAL ELLIPSISX-Y halogen bond is the main factor for the thermodynamic stability of these complexes. Arguments for electrostatic interactions as the driving force for this noncovalent interaction were discussed. Also, the equilibrium structures are additionally stabilised by weak C-HMIDLINE HORIZONTAL ELLIPSISX hydrogen bonds. Consequently, formally monodentate ligands are bound in a polycentric manner.