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In the crystal structure of the title compound, [Cu(NO3)2(C3H5N3)4], the CuII atom is situated on an inversion center (Wyckoff position 2c of space group P21/n) and shows an octahedral [N4O2] coordination environment. The axial positions are occupied by O atoms of nitrate anions, while the equatorial positions are taken up by the N atoms of four 3-aminopyrazole ligands. As a result of the tautomerism of the latter, two coordinate with the N¹-atom of 3-aminopyrazole while the other two with the N²-atom. The presence of pyrrole-like N--H groups and amine substituents as donor groups leads to numerous intra- and intermolecular hydrogen-bonding interactions, which were quantified by Hirshfeld surface analysis. [ABSTRACT FROM AUTHOR]

Lead halide hybrid perovskites incorporating chiral organic cations attract considerable attention due to their promising application in multifarious optoelectronic devices. However, the examples of chiral hybrid perovskites are still limited, which greatly impedes their further studies in various optoelectronic fields. Herein, we report on new low-dimensional lead-halide hybrid perovskites incorporating the enantiopure chiral α-amino acid L -proline. Two hybrid perovskites (L -proH)PbBr3·H2O (Pro-PbBr3) and (L -proH)4Pb3Br10·4H2O (Pro-Pb3Br10) have been synthesized by employing different ratios of organic and inorganic precursors. According to structural analysis, the inorganic sublattice of compound Pro-PbBr3 is built of one-dimensional (1D) [PbX3]∞n− lead halide chains, whereas the inorganic sublattice of compound Pro-Pb3Br10 is built upon a rare two-dimensional (2D) [Pb3Br10]∞4n− honeycomb-type inorganic framework. Hirshfeld surface analysis revealed an important role of various hydrogen bonding interactions in providing the binding between organic and inorganic parts of these hybrid perovskites. The optical band gap values of new hybrid perovskites as estimated using the Tauc plot approach are 4.19 eV (Pro-PbBr3) and 4.13 eV (Pro-Pb3Br10). Also, new compounds display low-temperature broadband photoluminescence which can be attributed to the self-trapped excitons. These results show the potential of α-proline for constructing novel and highly demanded chiral hybrid perovskites, which will hold great promise for further optoelectronic applications. [ABSTRACT FROM AUTHOR]

We studied the spin-state dependence of the electrical conductivity of two nanocrystalline powder samples of the spin crossover complex [Fe(pyrazine){Au(CN)2}2]. By applying an external pressure (up to 3 kbar), we were able to tune the charge transport properties of the material from a more conductive low spin state to a crossover point toward a more conductive high spin state. We rationalize these results by taking into account the spin-state dependence of the activation parameters of the conductivity. [ABSTRACT FROM AUTHOR]

In the title metal-organic framework, [Fe(C6H8N2)2{Cu(CN)2}2]n, the low-spin FeII ion lies at an inversion centre and displays an elongated octahedral [FeN6] coordination environment. The axial positions are occupied by two symmetryrelated bridging 2-ethylpyrazine ligands, while the equatorial positions are occupied by four N atoms of two pairs of symmetry-related cyanide groups. The CuI centre is coordinated by three cyanide carbon atoms and one N atom of a bridging 2-ethylpyrazine molecule, which form a tetrahedral coordination environment. Two neighbouring Cu atoms have a short Cu···Cu contact [2.4662 (7) Å] and their coordination tetrahedra are connected through a common edge between two C atoms of cyanide groups. Each Cu2(CN)2 unit, formed by two neighbouring Cu atoms bridged by two carbons from a pair of μ-CN groups, is connected to six FeII centres via two bridging 2-ethylpyrazine molecules and four cyanide groups, resulting in the formation of a polymeric three-dimensional metal-organic coordination framework. [ABSTRACT FROM AUTHOR]

In the title metal-organic framework, [Fe(C4H3BrN2)2{Cu(CN)2}2]n, the FeII cation is located on an inversion center and has a slightly elongated octa­hedral coordination environment [FeN6], ligated by two pyrazine N atoms of symmetry-related bridging 2-bromo­pyrazine mol­ecules in the axial positions and by four N atoms of pairs of symmetry-related cyanido groups in the equatorial positions. The CuI center has a fourfold coordination environment [CuC3N], with an almost perfect trigonal–pyramidal geometry, formed by three cyanido C atoms and an N atom of a bridging 2-bromo­pyrazine mol­ecule. Copper(I) centers related by a twofold rotation axis are bridged by two carbon atoms from a pair of μ-CN groups, resulting in Cu2(CN)2 units. Each Cu2(CN)2 unit is linked to six FeII cations via a pair of linear CN units, the pair of μ-CN groups and two bridging 2-bromo­pyrazine ligands, resulting in the formation of a metal–organic framework, which is additionally stabilized by the short CuCu contacts of 2.4450 (7) Å. [ABSTRACT FROM AUTHOR]

In the title polymeric complex, [Au2Fe(CN)4(C4H3IN2)2(C2H6O)]n, the FeII cation is coordinated by two iodo­pyrazine mol­ecules, one ethanol mol­ecule and three di­cyano­aurate anions in a distorted N5O octa­hedral geometry. In the crystal, the di­cyano­aurate anions bridge the FeII cations to form polymeric chains propagating along the b-axis direction. Stabilization of the crystal structure is provided by O—H···N hydrogen bonds and π–π stacking between parallel iodo­pyrazine rings of neighbouring chains, the centroid–centroid distances being 3.654 (10) and 3.658 (9) Å. [ABSTRACT FROM AUTHOR]

In the title polymeric complex, [Fe{OS(CH3)2}2{Ag(CN)2}2], the FeII cation is located at an inversion centre and is coordinated by four cyanide (CN-) anions and two dimethyl sulfoxide molecules in a slightly compressed N4O2 octahedral geometry, the AgI cation is C-coordinated by two CN- anions in a nearly linear geometry. The CN- anions bridge the FeII and AgI cations to form a twodimensional polymeric structure extending parallel to (102). In the crystal, the NEAREST Ag...Ag distance between polymeric sheets is 3.8122 (12) Å. The crystal studied was a twin with a contribution of 0.2108 (12) for the minor component. [ABSTRACT FROM AUTHOR]

Hybrid halide perovskites form a promising class of light-absorbing materials. Among the numerous 3D semiconducting perovskites, there is a group of emerging aziridinium-based hybrids that are considered to be prospective materials for optoelectronic applications. In this work, we report the mixed halide aziridinium perovskites of (AzrH)PbBrxI3-x series (AzrH = aziridinium). Small changes in the composition of perovskites are shown to have a defining impact on the optoelectronic properties of the reported materials. Halogen substitution allowed a variation in band gap values of these compounds, ranging from 1.57 to 2.23 eV, as established using electronic spectroscopy. Crystal structures of (AzrH)PbBrxI3-x perovskites were studied using single crystal and powder X-ray diffraction analysis. The lattice constant had a linear dependence on the Br content in the structure, thus strictly following Vegards's law. Importantly, the reported compounds displayed a preferential inclusion of iodine upon synthesis, revealing that the mixed halide perovskite composition cannot be estimated based on the precursors' ratio only, and it should be post-synthetically checked. The reported results expand the range of hybrid perovskites with tuneable band gaps beyond the conventional methylammonium and formamidinium-based perovskites and offer a new series of metal-halide hybrids suitable for photovoltaic and other optoelectronic applications.

Spin-crossover complexes with multistep transitions attract much attention due to their potential applications as multi-switches and for data storage. A four-step spin crossover is observed in the new iron(II)-based cyanometallic guest-free framework compound Fe(2-ethoxypyrazine) 2 {Ag(CN) 2 } 2 during the transition from the low-spin to the high-spin state. A reverse process occurs in three steps. Crystallographic studies reveal an associated stepwise evolution of the crystal structures. Multiple transitions in the reported complex originate from distinct Fe II sites which exist due to the packing of the ligand with a bulky substituent., (© 2022 Wiley-VCH GmbH.)

9-Amino-acridinium chloride N , N -di-methyl-formamide monosolvate, C 13 H 11 N 2 + Cl - ·C 3 H 7 NO, crystallizes in the monoclinic space group P 2 1 / c. The salt was crystallized from N , N -di-methyl-formamide. The asymmetric unit consists of two C 13 H 11 N 2 + Cl - formula units. The 9-amino-acridinium (9-AA) mol-ecules are protonated with the proton on the N atom of the central ring. This N atom is connected to an N , N -di-methyl-formamide mol-ecule by a hydrogen bond. The H atoms of the amino groups create short contacts with two chloride ions. The 9-AA cations in adjacent layers are oriented in an anti-parallel manner. The mol-ecules are linked via a network of multidirectional π-π inter-actions between the 9-AA rings, and the whole lattice is additionally stabilized by electrostatic inter-actions between ions., (© Fritsky et al. 2021.)

The title compound, [Cu 2 Cl 4 (C 5 H 10 N 2 O 2 ) 2 (CH 3 CN) 2 ] or [Cu 2 (μ 2 -Cl) 2 (CH 3 -Pz-COOCH 2 CH 3 ) 2 Cl 2 (CH 3 CN) 2 ], was synthesized using a one-pot reaction of copper powder, copper(II) chloride dihydrate and ethyl 5-methyl-1 H -pyrazole-3-carboxyl-ate (CH 3 -Pz-COOCH 2 CH 3 ) in aceto-nitrile under ambient conditions. This complex consists of discrete binuclear mol-ecules with a {Cu 2 (μ 2 -Cl) 2 } core, in which the Cu⋯Cu distance is 3.8002 (7) Å. The pyrazole-based ligands are bidentate coordinated, leading to the formation of two five-membered chelate rings. The coordination geometry of both copper atoms (ON 2 Cl 3 ) can be described as distorted octa-hedral on account of the aceto-nitrile coordination. A Hirshfeld surface analysis suggests that the most important contributions to the surface contacts are from H⋯H (40%), H⋯Cl/Cl⋯H (24.3%), H⋯O/O⋯H (11.8%), H⋯C/C⋯H (9.2%) and H⋯N/N⋯H (8.3%) inter-actions., (© Vynohradov et al. 2021.)

Hofmann-like cyanometalates constitute a large class of spin-crossover iron(II) complexes with variable switching properties. However, it is not yet clearly understood how the temperature and cooperativity of a spin transition are influenced by their structure. In this paper, we report the synthesis and crystal structures of the metal-organic coordination polymers {Fe II (Mepz)[Au I (CN) 2 ] 2 } ( [Au] ) and {Fe II (Mepz) 2 [Ag I (CN) 2 ] 2 } ( [Ag] ), where Mepz = 2-methylpyrazine, along with characterization of their spin-state behavior by variable-temperature SQUID magnetometry and Mössbauer spectroscopy. The compounds are built of cyanoheterometallic layers, which are pillared by the bridging Mepz ligands in [Au] but separated in [Ag] . The complex [Au] exhibits an incomplete stepped spin transition as a function of the temperature with T SCO1 = 170 K and T SCO2 = 308 K for the two subsequent steps. In contrast, the complex [Ag] attains the high-spin state over the whole temperature range. In the crystal structure of [Ag] , weak interlayer contacts (Ag-π, Me-π, and Ag-N) are found that may be responsible for an unusual axial elongation of the FeN 6 polyhedra. We propose that this structural distortion contributes to the trapping of iron in its high-spin state.

In the title metal-organic framework, [Fe(C 6 H 8 N 2 ) 2 {Cu(CN) 2 } 2 ] n , the low-spin Fe II ion lies at an inversion centre and displays an elongated octa-hedral [FeN 6 ] coordination environment. The axial positions are occupied by two symmetry-related bridging 2-ethyl-pyrazine ligands, while the equatorial positions are occupied by four N atoms of two pairs of symmetry-related cyanide groups. The Cu I centre is coordinated by three cyanide carbon atoms and one N atom of a bridging 2-ethyl-pyrazine mol-ecule, which form a tetra-hedral coordination environment. Two neighbouring Cu atoms have a short Cu⋯Cu contact [2.4662 (7) Å] and their coordination tetra-hedra are connected through a common edge between two C atoms of cyanide groups. Each Cu 2 (CN) 2 unit, formed by two neighbouring Cu atoms bridged by two carbons from a pair of μ-CN groups, is connected to six Fe II centres via two bridging 2-ethyl-pyrazine mol-ecules and four cyanide groups, resulting in the formation of a polymeric three-dimensional metal-organic coordination framework.