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The unit cell of the title compound, [Ni(C16H10ClN6)2]·2CH3OH, consists of a neutral complex and two methanol mol­ecules. In the complex, the two tridentate 2-(3-(4-chloro­phen­yl)-1H-1,2,4-triazol-5-yl)-6-(1H-pyrazol-1-yl)pyridine ligands coordinate to the central NiII ion through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo­octa­hedral coordination sphere. Neighbouring tapered mol­ecules are linked through weak C—H(pz)⋯π(ph) inter­actions into monoperiodic chains, which are further linked through weak C—H⋯N/C inter­actions into diperiodic layers. The inter­molecular contacts were qu­anti­fied using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative contributions of the contacts to the crystal packing to be H⋯H 32.8%, C⋯H/H⋯C 27.5%, N⋯H/H⋯N 15.1%, and Cl⋯H/H⋯Cl 14.0%. The average Ni—N bond distance is 2.095 Å. Energy framework analysis at the HF/3–21 G theory level was performed to qu­antify the inter­action energies in the crystal structure. [ABSTRACT FROM AUTHOR]

The reaction of cadmium iodide with 3-amino­pyrazole (3-apz) in ethano­lic solution leads to tautomerization of the ligand and the formation of crystals of the title compound, catena-poly[[di­iodido­cadmium(II)]-bis­(μ-3-amino-1H-pyrazole)-κ²N²:N³;κ²N³:N²], [CdI2(C3H5N3)2]n or [CdI2(3-apz)2]n. Its asymmetric unit consists of a half of a Cd2+ cation, an iodide anion and a 3-apz mol­ecule. The Cd2+ cations are coordinated by two iodide anions and two 3-apz ligands, generating trans-CdN4I2 octa­hedra, which are linked into chains by pairs of the bridging ligands. In the crystal, the ligand molecules and iodide anions of neighboring chains are linked through inter­chain hydrogen bonds into a di-periodic network. The inter­molecular contacts were qu­anti­fied using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative quantitative contributions of the weak inter­molecular contacts. [ABSTRACT FROM AUTHOR]

The reaction of cadmium iodide with 3-amino­pyrazole (3-apz) in ethano­lic solution leads to tautomerization of the ligand and the formation of crystals of the title compound, catena-poly[[di­iodido­cadmium(II)]-bis­(μ-3-amino-1H-pyrazole)-κ²N²:N³;κ²N³:N²], [CdI2(C3H5N3)2]n or [CdI2(3-apz)2]n. Its asymmetric unit consists of a half of a Cd2+ cation, an iodide anion and a 3-apz mol­ecule. The Cd2+ cations are coordinated by two iodide anions and two 3-apz ligands, generating trans-CdN4I2 octa­hedra, which are linked into chains by pairs of the bridging ligands. In the crystal, the ligand mol­ecules and iodide anions of neighboring chains are linked through inter­chain hydrogen bonds into a di-periodic network. The inter­molecular contacts were qu­anti­fied using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative qu­anti­tative contributions of the weak inter­molecular contacts. [ABSTRACT FROM AUTHOR]

Octahedrally coordinated spin crossover (SCO) FeII complexes represent an important class of switchable molecular materials. This study presents the synthesis and characterisation of a novel complex, [FeII(ppt-2Fph)2]0·2MeOH, where ppt-2Fph is a new asymmetric ionogenic tridentate planar ligand 2-(5-(2-fluorophenyl)-4H-1,2,4-triazol-3-yl)-6-(1H-pyrazol-1-yl)pyridine. The complex exhibits a hysteretic thermally induced SCO transition at 285 K on cooling and at 293 K on heating, as well as light induced excited spin state trapping (LIESST) at lower temperatures with a relaxation T(LIESST) temperature of 73 K. Single crystal analysis in both spin states shows that the compound undergoes an unusual partial (25%) reversible order–disorder of the asymmetrically substituted phenyl group coupled to the thermal SCO. The highly cooperative SCO transition, analysed by structural energy framework analysis at the B3LYP/6-31G(d,p) theory level, revealed the co-existence of stabilising and destabilising energy variations in the lattice. The observed antagonism of intermolecular interactions and synchronous rotational disorder, which contributes to the overall entropy change, is suggested to be at the origin of the cooperative SCO transition. [ABSTRACT FROM AUTHOR]

Chemical composition is leading among the numerous factors that determine the spin transition properties of coordination compounds. Classic dicyanometallic bridges {M(CN)2}− are commonly used to build Hofmann-like spin-crossover frameworks, but some extended bridges are also synthetically available. In this paper, we describe a successful synthesis of two very similar spin-crossover frameworks that differ in the cyanometallic bridges involved, namely [Fe(etpz)2{Ag(CN)2}2] (1) and {Fe(etpz)2[Ag2(CN)3][Ag(CN)2]} (2) (where etpz = 2-ethylpyrazine). Magnetic and Mössbauer studies demonstrated the occurrence of abrupt one-step high-spin (HS) ↔ low-spin (LS) transitions for both complexes. The spin transition temperatures are T1/2 ↓ = 233 K and T1/2 ↑ = 243 K for 1 and T1/2 ↓ = 188 K and T1/2 ↑ = 191 K for 2 with thermal hysteresis loops of 10 K for 1 and 3 K for 2. The bridging mononuclear [Ag(CN)2]− units and FeII cations assemble to form infinite 2D layers in the structure of 1. Interestingly, compound 2 forms 2D layers of FeII cations bridged by both binuclear [Ag2(CN)3]− and mononuclear [Ag(CN)2]− units. The structures of 1 and 2 comprise different types of intermolecular interactions including Ag⋯Ag and Ag⋯Netpz, which induce the creation of supramolecular 3D frameworks. The synergy between metallophilic interactions and the spin transition is also confirmed by the variation of Ag⋯Ag distances during spin crossover. The characterization of such analogues allowed us to analyze in detail the effect of the cyanometallic bridge on the structure of new frameworks and on the bistability in Hofmann-like complexes. [ABSTRACT FROM AUTHOR]

The synthetic availability of molecular water oxidation catalysts containing highvalent ions of 3d metals in the active site is a prerequisite to enabling photo- and electrochemical water splitting on a large scale. Herein, the synthesis and crystal structure of diammonium {μ-1,3,4,7,8,10,12,13,16,17,19,22-dodecaazatetracyclo[ 8.8.4.1³,17.18,12]tetracosane-5,6,14,15,20,21-hexaonato}ferrate(IV) acetic acid trisolvate, (NH4)2[FeIV(C12H12N12O6)]·3CH3COOH or (NH4)2[FeIV(L-6H)]·3CH3COOH is reported. The FeIV ion is encapsulated by the macropolycyclic ligand, which can be described as a dodeca-aza-quadricyclic cage with two capping triazacyclohexane fragments making three five- and six sixmembered alternating chelate rings with the central FeIV ion. The local coordination environment of FeIV is formed by six deprotonated hydrazide nitrogen atoms, which stabilize the unusual oxidation state. The FeIV ion lies on a twofold rotation axis (multiplicity 4, Wyckoff letter e) of the space group C2/c. Its coordination geometry is intermediate between a trigonal prism (distortion angle φ = 0°) and an antiprism (φ = 60°) with φ = 31.1°. The Fe--N bond lengths lie in the range 1.9376 (13)-1.9617 (13) Å, as expected for tetravalent iron. Structure analysis revealed that three acetic acid molecules additionally cocrystallize per one iron(IV) complex, and one of them is positionally disordered over four positions. In the crystal structure, the ammonium cations, complex dianions and acetic acid molecules are interconnected by an intricate system of hydrogen bonds, mainly via the oxamide oxygen atoms acting as acceptors. [ABSTRACT FROM AUTHOR]

The reaction of cadmium bromide tetra­hydrate with 3-amino­pyrazole (3-apz) in ethano­lic solution leads to tautomerization of the ligand and the formation of crystals of the title compound, catena-poly[[di­bromido­cadmium(II)]-bis­(μ-3-amino-1H-pyrazole)-κ²N³:N²;κ²N²:N³], [CdBr2(C3H5N3)2]n or [CdBr2(3-apz)2]n. Its asymmetric unit consists of a half of a Cd2+ cation, a bromide anion and a 3-apz mol­ecule. The Cd2+ cations are coordinated by two bromide anions and two 3-apz ligands, generating trans-CdN4Br2 octa­hedra, which are linked into chains by pairs of the bridging ligands. In the crystal, the ligand mol­ecules and bromide anions of neighboring chains are linked through inter­chain hydrogen bonds into a two-dimensional network. The inter­molecular contacts were qu­anti­fied using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative qu­anti­tative contributions of the weak inter­molecular contacts. [ABSTRACT FROM AUTHOR]

The title compound, [FeLi2(C12H12N12O6)(H2O)4]⋅4H2O, consists of iron complex anions, lithium cations and water molecules. The complex anion shows a clathrochelate topology. The coordination geometry of the FeIV centre is intermediate between a trigonal prism and a trigonal antiprism. In the crystal, the complex anions are connected through two Li cations into dimers, which are connected by Li--O bonds, forming infinite chains along the b-axis direction. [ABSTRACT FROM AUTHOR]

The unit cell of the title compound, [Fe(C18H15N6O2)2]•2CH3OH•2CHCl3, consists of a charge-neutral complex molecule, two methanol and two chloroform molecules. In the complex, the two tridentate 2-(5-(3,4-dimethoxyphenyl)-1,2,4-triazol-3-yl)-6-(pyrazol-1-yl)pyridine ligands coordinate to the central FeII ion through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo-octahedral coordination sphere. Neighbouring tapered molecules are linked through weak C--H(pz)• • •π(ph) interactions into one-dimensional chains, which are joined into two-dimensional layers through weak C--H• • •N/C/ O interactions. Furthermore, the layers stack in a three-dimensional network linked by weak interlayer C--H• • •π interactions of the methoxy and phenyl groups. The intermolecular contacts were quantified using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative contributions of the contacts to the crystal packing to be H• • •H 32.0%, H• • •C/C• • •H 26.3%, H• • •N/N• • •H 13.8%, and • • •O/O• • •H 7.5%. The average Fe--N bond distance is 2.185 Å, indicating the high-spin state of the FeII ion. Energy framework analysis at the HF/3-21 G theory level was performed to quantify the interaction energies in the crystal structure. [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]

Using the direct synthesis method, by oxidative dissolution of copper powder in the presence of CuBr2 and C5H8N2 (3,5-dimethyl-1H-pyrazole), three different types of crystals were formed, isolated, and identified. Three new coordination compounds, trinuclear [Cu3(µ3-OH)( µ2-C5H7N2Br)( µ2-Br)3(C5H8N2)5Br]⋅CHCh (where C5H7N2Br - 4-bromo-3,5-dimethylpyrazole) (1) (orthorhombic, Pnma), binuclear [Cu2(µ2-C5H7N2Br)( µ2-Br)( C5H7N2)4Br2]⋅2CHCl3 (2) (monoclinic, C2/c) and mononuclear [CuBr2( C5H7N2)3] (3) (triclinic, PI), have been obtained. According to the single-crystal X-ray diffraction analysis, the complex 1 is a trinuclear six-membered cycle, where copper atoms are connected by three types of bridges: µ2-bromide ions, µ2-4-bromo-3,5-dimethylpyrazole molecule, and µ3-hydroxo group. The binuclear complex 2 is formed due to a connection between two copper atoms by a bidentate-bridging bromide ion and a bridged 4-brominated 3,5-dimethylpyrazole molecule. Coordination compound 3 is a mono-nuclear trigonal-bipyramidal copper(II) complex. During the reaction, some part of 3,5-dimethylpyrazole molecules was brominated in the 4th position of the pyrazole ring. The Hirshfeld surface analysis reveals that the inter- molecular H⋯H contacts have the highest contribution to the crystal packing of all compounds: 66.9 % for 1, 54.4 % for 2, and 66.5 % for 3. [ABSTRACT FROM AUTHOR]

The asymmetric unit of the title compound, [FeII(C16H9Cl2N6)2]·2CH3OH, consists of half of a charge-neutral complex molecule and a discrete methanol molecule. The planar anionic tridentate ligand 2-[5-(3,5-dichlorophenyl)-4H-1,2,4-triazol-3-ato]-6-(1H-pyrazol-1-yl)pyridine coordinates to the FeII ion through the N atoms of the pyrazole, pyridine and triazole groups, forming a coordination sphere of the central ion that deviates moderately from an octahedral geometry. The average Fe--N bond distance is 1.953 A °, indicating the low-spin state of the FeII ion. The cone-like-shaped molecules, nested into each other, are linked through double weak C--H(pz)· · ·π(ph) interactions into mono-periodic columns, which are further linked through weak C--H· · ·N'/C' interactions into di-periodic layers. The layers interact through double weak C-H(ph)· · ·Cl bonds with neighbouring molecules. Energy framework analysis at the B3LYP/6-31 G(d,p) theory level reproduces the strong interaction within the layers and the weaker interlayer interactions. Intermolecular contacts were quantified using Hirshfeld surface analysis and two-dimensional fingerprint plots, the relative contributions of the contacts to the crystal packing being H· · ·H 26.1%, H· · ·C/C· · ·H 24.4%, H· · ·Cl/Cl· · ·H 18.9% and H· · ·N/N· · ·H 12.1%. [ABSTRACT FROM AUTHOR]

The unit cell of the title compound, [FeII(C17H12BrN6O)2].2MeOH, consists of a charge-neutral complex molecule and two independent molecules of methanol. In the complex molecule, the two tridentate ligand molecules 2-[5-(3-bromo-4-methoxyphenyl)-4H-1,2,4-triazol-3-yl]-6-(1H-pyrazol-1-yl)pyridine coordinate to the FeII ion through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudo-octahedral coordination sphere around the central ion. In the crystal, neighbouring asymmetric molecules are linked through weak C--H(pz)...π(ph) interactions into chains, which are then linked into layers by weak C-H···N/C interactions. Finally, the layers stack into a three-dimensional network linked by weak interlayer C--H...π interactions between the methoxy groups and the phenyl rings. The intermolecular contacts were quantified using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing the relative contributions of the contacts to the crystal packing to be H...H 34.2%, H...C/C...H 25.2%, H...Br/Br...H 13.2%, H....N/N....H 12.2% and H·O/O...H 4.0%. The average Fe--N bond distance is 1.949 A °, indicating the lowspin state of the FeII ion. Energy framework analysis at the HF/3-21 G theory level was performed to quantify the interaction energies in the crystal structure. [ABSTRACT FROM AUTHOR]

As a result of the high symmetry of the Aea2 structure, the asymmetric unit of the title compound, [FeII(C18H15N6)2]·2MeOH, consists of half of a chargeneutral complex molecule and a discrete methanol molecule. The planar anionic tridentate ligand 2-[5-(3,4-dimethylphenyl)-4H-1,2,4-triazol-3-ato]-6-(1Hpyrazol-1-yl)pyridine coordinates the FeII ion meridionally through the N atoms of the pyrazole, pyridine and triazole groups, forming a pseudooctahedral coordination sphere of the central ion. The average Fe--N bond distance is 1.955 A °, indicating a low-spin state of the FeII ion. Neighbouring cone-shaped molecules, nested into each other, are linked through double weak C--H(pz)····(ph') interactions into mono-periodic columns, which are further linked through weak C--H···N0/C0 interactions into di-periodic layers. No interactions shorter than the sum of the van der Waals radii of the neighbouring layers are observed. Energy framework analysis at the B3LYP/6-31 G(d,p) theory level, performed to quantify the intermolecular interaction energies, reproduces the weak interlayer interactions in contrast to the strong interaction within the layers. Intermolecular contacts were quantified using Hirshfeld surface analysis and two-dimensional fingerprint plots, showing the relative contributions of the contacts to the crystal packing to be H···H 48.5%, H···C/C···H 28.9%, H···N/N···H 16.2% and C···C 2.4%. [ABSTRACT FROM AUTHOR]

A series of new coordination compounds [MnL2·4H2O]n (1), [CoL2·4H2O]n (2), [NiL2·4H2O]n (3), [CuL2·4H2O]n (4), [ZnL2·4H2O]n (5) based on (3,5-dimethyl-1H-pyrazole-4-yl)-acetic acid (L) has been synthesized. The synthesis of L is also described. Binding mode of L in 1-5 was determined via IR spectroscopy. pH-dependent complex formation study between 3d-metal cations and L was carried out in solutions that allowed to determine optimal synthetic conditions and to approximately estimate the coordination environment of central atoms. Synthetic approaches to the preparation of coordination compounds were developed and crystalline compounds 1-5 were isolated. Isostructurality of 1-5 was identified by powder x-ray diffraction analysis. Structures 2 and 4 were determined via single crystal x-ray diffraction. Obtained compounds consist of tetranuclear fragments M4L4 and water molecules. The latter participate in the formation of intramolecular and intermolecular hydrogen bonds. Thereby, 1-5 possess the polymeric structure of 3D diamond framework type. Their frameworks contain cavities with a diameter of 412 Å. [ABSTRACT FROM AUTHOR]

9-Amino­acridinium chloride N,N-di­methyl­formamide monosolvate, C13H11N2+Cl−·C3H7NO, crystallizes in the monoclinic space group P21/c. The salt was crystallized from N,N-di­methyl­formamide. The asymmetric unit consists of two C13H11N2+Cl− formula units. The 9-amino­acridinium (9-AA) mol­ecules are protonated with the proton on the N atom of the central ring. This N atom is connected to an N,N-di­methyl­formamide mol­ecule 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 anti­parallel manner. The mol­ecules are linked via a network of multidirectional π–π inter­actions between the 9-AA rings, and the whole lattice is additionally stabilized by electrostatic inter­actions between ions. [ABSTRACT FROM AUTHOR]

Mn cage complexes are rare, and the ones successfully isolated in the solid state are not stable in water and organic solvents. Herein, we present the first report of mononuclear Mn clathrochelates, in which the encapsulated metal exists in the oxidation state +4. The complexes are extremely stable in the crystalline state and in solutions and show rich redox chemistry. [ABSTRACT FROM AUTHOR]

Chiral hybrid organic–inorganic perovskites (HOIPs) attract attention due to their potential for application in optoelectronic, spintronic and photovoltaic devices. However, to this day the range of available chiral HOIPs is still scarce. In this context, we synthesized and thoroughly characterized two pairs of enantiomeric HOIPs incorporating enantiopure α-alanine, the simplest chiral amino acid: (AlaH)PbX3 (Ala = R-alanine or S-alanine, X = Br or I). Single-crystal XRD measurements revealed an unusual 2D anionic motif, which consists of haloplumbate octahedra bonded together in an edge-sharing manner along the c axis and in a corner-sharing manner along the b axis. Four compounds undergo melting/crystallization at unusually low temperatures. New compounds also display photoluminescence in the visible range: 380–640 nm (X = Br) and 480–640 nm (X = I). Electronic spectroscopy reveals an optical response typical for semiconductive materials with optical band gaps of 3.12 eV (X = Br) and 2.48 eV (X = I). These results show that the incorporation of simple and easily accessible α-alanine (and other chiral amino acids) as a cationic part is an efficient way for obtaining highly demanding chiral HOIPs. [ABSTRACT FROM AUTHOR]

Hofmann-like cyanometallic complexes represent one of the biggest and well-known classes of FeII spin-crossover compounds. In this paper, we report on the first FeII Hofmann clathrate analogues with unsubstituted 1,2,3-triazole, which exhibit temperature induced spin transition. Two new coordination polymers with the general formula [FeII(1,2,3-triazole)2MII(CN)4] (M = Pt, Pd) undergo abrupt hysteretic spin crossover in the range of 190–225 K as revealed by magnetic susceptibility measurements. Two compounds are isostructural and are built of infinite cyanometallic layers which are supported by 1,2,3-triazole ligands. The thermal hysteresis loop is very stable at different scan rates from 0.5 to 10 K min−1. The compounds display strong thermochromic effect, changing their colour from pink in the low-spin state to white in the high-spin state. Our findings show that 1,2,3-triazole is suitable for elaboration of spin-crossover Hofmann clathrate analogues, and its use instead of more classical azines can advantageously expand this family of complexes. [ABSTRACT FROM AUTHOR]

Spin‐crossover complexes form one of the biggest families of switchable compounds. Here we show a new way to obtain spin‐crossover materials by direct synthesis from metallic iron. Four complexes of FeII with 4‐R‐1,2,4‐triazoles have been synthesized by a direct metal oxidation: [Fe(NH2trz)3]SO4, [Fe(NH2trz)3](BF4)2 and two polymorphs of [Fe(Htrz)2(trz)]BF4. Surprisingly high quality of PXRD pattern of [Fe(NH2trz)3]SO4 allowed to perform Rietveld refinement and obtain reliable crystal structure of the latter. All compounds have been studied by magnetic susceptibility measurements, optical reflectivity, differential scanning calorimetry and Raman spectroscopy. Importantly, spin‐crossover characteristics of the complexes obtained by this unusual method are preserved, thus revealing a new effective approach of "direct synthesis" towards switchable coordination compounds. [ABSTRACT FROM AUTHOR]

Two new 2D spin-crossover (SCO) analogues of Hofmann clathrates of composition [Fe(phth)2MII(CN)4] (where phth = phthalazine; MII = Pd, Pt) have been synthesized and their structures and switchable behaviour have been characterized. Single-crystal X-ray analysis reveals that the Pt and Pd derivatives contain FeII centres equatorially surrounded by four equivalent μ4-[MII(CN)4]2− groups. Two crystallographically equivalent phthalazine (phth) ligands occupy the axial positions of each FeII site, completing its octahedral coordination environment. The stabilization of these structures is realized via supramolecular C–H⋯M interactions and π–π stacking. Temperature-dependent magnetic susceptibility measurements showed that Pt (T1/2↓ = 211 K and T1/2↑ = 218 K) and Pd (T1/2↓ = 202 K and T1/2↑ = 207 K) derivatives display cooperative spin crossover with narrow thermal hysteresis loops. In addition, spin crossover in these complexes was characterized by optical measurements, differential scanning calorimetry, and IR and Raman spectroscopy. This research shows that the use of phthalazine leads to the production of new SCO systems with attractive transition characteristics and opens up new perspectives for the design of switchable complexes based on fused bicyclic azine ligands. [ABSTRACT FROM AUTHOR]

The unit cell of the title compound, [Zn(C17H18N3O4)2]·CH4O·C2H6O, contains two complex molecules related by an inversion centre, plus one methanol and one ethanol solvent molecule per complex molecule. In each complex, two deprotonated pyridine aroylhydrazone ligands {3,4,5-trimethoxy-N'-[1-(pyridin-2-yl)ethylidene]benzohydrazide} coordinate to the ZnII ion through the N atoms of the pyridine group and the ketamine, and, additionally, through the O atom of the enolate group. In the crystal, dimers are formed by π-π interactions between the planar ligand moieties, which are further connected by C···O and C···C interactions. The intermolecular interactions were investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots, revealing that the most important contributions for the crystal packing are from H···H (44.8%), H···C/C···H (22.2%), H···O/O···H (18.7%) and C···C (3.9%) interactions. [ABSTRACT FROM AUTHOR]

In the molecule of the title anthracene derivative, C22H17NO2, the benzene ring is inclined to the mean plane of the anthracene ring system (r.m.s. deviation = 0.024 Å) by 75.21 (9)°. In the crystal, molecules are linked by pairs of O--H ⋯O hydrogen bonds, forming classical carboxylic acid inversion dimers with an R²2(8) ring motif. The dimers are linked by C--H ⋯π interactions, forming a supramolecular framework. [ABSTRACT FROM AUTHOR]

The title compound, C14H12BrNO2, was synthesized by the condensation reaction of 2,3-di­hydroxy­benzaldehyde and 2-bromo-3-methyl­aniline. It crystallizes in the centrosymmetric triclinic space group P. The configuration about the C=N bond is E. The dihedral angle between the planes of the 5-(2-bromo-3-methyl­phenyl ring and the catechol ring is 2.80 (17)°. In the crystal, O—H···O hydrogen-bond inter­actions consolidate the crystal packing. [ABSTRACT FROM AUTHOR]

In the title com­plex, [Cu(C18H12F6N2O4)]·0.5C6H6O2, the CuII ion has a square-planar coordination geometry, being ligated by two N and two O atoms of the tetra­dentate open-chain Schiff base ligand 6,6′-{(1E,1′E)-[ethane-1,2-diylbis(aza­nylyl­idene)]bis­(methanylyl­idene)}bis­[2-(tri­fluoro­meth­oxy)phenol]. The crystal packing is stabilized by intra­molecular O—H∙∙∙O and inter­molecular C—H∙∙∙F, C—H∙∙∙O and C—H∙∙∙π hydrogen bonds. In addition, weak π–π inter­actions form a three-dimensional structure. Hirshfeld surface analysis and two-dimensional fingerprint plots were performed and created to analyze the inter­molecular inter­actions present in the crystal, indicating that the most important contributions for the crystal packing are from F∙∙∙H/H∙∙∙F (25.7%), H∙∙∙H (23.5%) and C∙∙∙H/H∙∙∙C (12.6%) inter­actions. [ABSTRACT FROM AUTHOR]

In the title compound, bis­(2-meth­oxy­ethyl xanthato-κS)(N,N,N′,N′-tetra­methyl­-ethylenedi­amine-κ²N,N′)zinc(II) acetone hemisolvate, [Zn(C4H7O2S2)2(C6H16N2)]·0.5C3H6O, the ZnII ion is coordinated by two N atoms of the N,N,N′,N′-tetra­methyl­ethylenedi­amine ligand and two S atoms from two 2-meth­oxy­ethyl xanthate ligands. The amine ligand is disordered over two orientations and was modelled with refined occupancies of 0.538 (6) and 0.462 (6). The mol­ecular structure features two C—H∙∙∙O and two C—H∙∙∙S intra­molecular inter­actions. In the crystal, mol­ecules are linked by weak C—H∙∙∙O and C—H∙∙∙S hydrogen bonds, forming a three-dimensional supra­molecular architecture. The mol­ecular structure was optimized using density functional theory (DFT) at the B3LYP/6–311 G(d,p) level. The smallest HOMO–LUMO energy gap (3.19 eV) indicates the suitability of this crystal for optoelectronic applications. The mol­ecular electrostatic potential (MEP) further identifies the positive, negative and neutral electrostatic potential regions of the mol­ecules. Half a mol­ecule of disordered acetone was removed with the solvent-mask procedure in OLEX2. [ABSTRACT FROM AUTHOR]

The asymmetric unit of the title compound, [Fe(C13H18BN6)2], contains two half independent complex molecules. In each complex, the FeII atom is located on an inversion center and is surrounded by two scorpionate ligand butyltris(1Hpyrazol- 1-yl)borate molecules that coordinate to the iron(II) ion through the N atoms of the pyrazole groups. The two independent complex molecules differ essentially in the conformation of the butyl substituents. In the crystal, the complex molecules are linked by a series of C—H···π interactions, which generate a supramolecular three-dimensional structure. At 120 K, the average Fe—N bond distance is 1.969 Å, indicating the low-spin state of the iron(II) atom, which does not change upon heating, as demonstrated by hightemperature magnetic susceptibility measurements. [ABSTRACT FROM AUTHOR]

The first example of a Cu(ii) 12-MC-4 hydroxamic metallacrown containing an ethylphosphonate group as an additional donor function in the β-position with respect to the hydroxamic group is described. The solution equilibrium of ethylphosphonoacetohydroxamic acid (PAHEt) with Cu(ii) was investigated in aqueous solution by a combination of potentiometry, mass spectrometry, UV-Vis and EPR spectroscopies, and isothermal titration calorimetry. A model containing mononuclear [CuL], [CuL2]2− and [CuL2H−1]3− and pentanuclear [Cu5(LH−1)4]2− species is proposed. The predominance of the [Cu5(LH−1)4]2− species in solution over the pH range 4–9 was confirmed by the signals present in the ESI-MS spectra, as well as the absence of the EPR signal. In addition, the results of isothermal titration calorimetry indicated the stoichiometry of the complex form at pH 5.5 as 1.25. Even if forming a less stable MC complex, PAHEt offers the formation of 12-MC-4 in a broad pH range, which distinguishes it especially from α-aminohydroxamic acids. The compound corresponding to the pentameric metallacrown complex was isolated in the solid state as {Na4(H2O)6(Ac)[Cu5(PAHEt-3H)4(Ac)]}2·3H2O (1), whose crystal structure was determined by X-ray analysis. The centrosymmetric decanuclear complex anion of (1) consists of two pentanuclear 12-MC-4 fragments formed by five Cu(ii) ions and four triply deprotonated residues of the phosphonoacetohydroxamate ligand, and is associated with eight sodium cations, two acetate anions and twelve water molecules taking part in sodium cation coordination, as well as solvate water molecules. The stability of MCs under conditions of competitive complex formation, as well as their reactivity with respect to a strong chelating agent, 2,2′-dipyridyl (dipy), was examined, and as a result a 1D coordination polymer featuring mixed-ligand mononuclear units {[Cu(dipy)(PAHEt-2H)]}n·1.86nH2O (2) was formed. In addition the chelating capacity of this ligand toward Ni(ii) and Zn(ii) ions was studied in solution. [ABSTRACT FROM AUTHOR]

An efficient water oxidation system is a prerequisite for developing solar energy conversion devices. Using advanced time-resolved spectroscopy, we study the initial catalytic relevant electron transfer events in the light-driven water oxidation system utilizing [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) as a light harvester, persulfate as a sacrificial electron acceptor, and a high-valent iron clathrochelate complex as a catalyst. Upon irradiation by visible light, the excited state of the ruthenium dye is quenched by persulfate to afford a [Ru(bpy)3]3+/SO4Ṗ− pair, showing a cage escape yield up to 75%. This is followed by the subsequent fast hole transfer from [Ru(bpy)3]3+ to the FeIV catalyst to give the long-lived FeV intermediate in aqueous solution. In the presence of excess photosensitizer, this process exhibits pseudo-first order kinetics with respect to the catalyst with a rate constant of 3.2(1) × 1010 s−1. Consequently, efficient hole scavenging activity of the high-valent iron complex is proposed to explain its high catalytic performance for water oxidation. [ABSTRACT FROM AUTHOR]

The asymmetric unit of the title compound, C15H12N2O2, contains two crystallographically independent mol­ecules in which the dihedral angles between the benzene rings in each are 13.26 (5) and 7.87 (5)°. An intra­molecular O—H···N hydrogen bonds results in the formation of an S(6) ring motif. In the crystal, mol­ecules are linked by weak C—H···O and C—H···N hydrogen bonds, forming layers parallel to (011). In addition, π–π stacking inter­actions with centroid–centroid distances in the range 3.693 (2)–3.931 (2) Å complete the three-dimensional network. [ABSTRACT FROM AUTHOR]

The title compound, C9H11NO2, was obtained as unexpected product from the reaction of (4-{2-benz­yloxy-5-[(E)-(3-chloro-4-methyl­phen­yl)diazen­yl]benzyl­idene}-2-phenyl­oxazol-5(4H)-one) with 2-meth­oxy­aniline in the presence of acetic acid as solvent. The amide group is not coplanar with the benzene ring, as shown by the C—N—C—O and C—N—C—C torsion angles of −2.5 (3) and 176.54 (19)°, respectively. Hirshfeld surface analysis and two-dimensional fingerprint plots indicate that the most important contributions to the crystal packing are from H⋯H (53.9%), C⋯H/H⋯C (21.4%), O⋯H/H⋯O (21.4%) and N⋯H/H⋯N (1.7%) inter­actions. [ABSTRACT FROM AUTHOR]

In the title compounds, 9-bromo-2,5-dimethyl-11,12-di­hydro-5H-5,11-methano­benzo[g][1,2,4]triazolo[1,5-c][1,3,5]oxa­diazo­cine, C13H13BrN4O (I), and 7-meth­oxy-5-methyl-2-(pyridin-4-yl)-11,12-di­hydro-5H-5,11-methano­benzo[g][1,2,4]tri­azolo[1,5-c][1,3,5]oxa­diazo­cine, C18H17N5O2 (II), the triazole ring is inclined to the benzene ring by 85.15 (9) and 76.98 (5)° in compounds I and II, respectively. In II, the pyridine ring is almost coplanar with the triazole ring, having a dihedral angle of 4.19 (8)°. In the crystal of I, pairs of N—HN hydrogen bonds link the mol­ecules to form inversion dimers with an R2²(8) ring motif. The dimers are linked by C—H...π and C—Br...π inter­actions forming layers parallel to the bc plane. In the crystal of II, mol­ecules are linked by N—H...N and C—H...O hydrogen bonds forming chains propagating along the b-axis direction. The inter­molecular inter­actions were investigated using Hirshfeld surface analysis and two-dimensional fingerprint plots, and the mol­ecular electrostatic potential surface was also analysed. The Hirshfeld surface analysis of I suggests that the most significant contributions to the crystal packing are H...H (42.4%) and O...H/H...O (17.9%) contacts. For compound II, the H...H (48.5%), C...H/H...C (19.6%) and N...H/H...N (16.9%) inter­actions are the most important contributions. [ABSTRACT FROM AUTHOR]

A water-stable FeIV clathrochelate complex catalyses fast and homogeneous photochemical oxidation of water to dioxygen with a turnover frequency of 2.27 s−1 and a maximum turnover number of 365. An FeV intermediate generated under catalytic conditions is trapped and characterised using EPR and Mössbauer spectroscopy. [ABSTRACT FROM AUTHOR]

A new iron(ii)-based spin-crossover compound with thermal hysteresis operating under ambient conditions is reported. This complex exhibits a high reproducibility of the spin transition in many successive thermal cycles, stability of both spin states at room temperature and an attractive operational temperature range. [ABSTRACT FROM AUTHOR]

The title compound, C14H12ClNO3, is a Schiff base that exists in the keto–enamine tautomeric form and adopts a Z configuration. In the crystal, the dihedral angle between the planes of the benzene rings is 5.34 (15)°. The roughly planar geometry of the mol­ecule is stabilized by a strong intra­molecular N—HO hydrogen bond. In the crystal, pairs of centrosymmetrically related mol­ecules are linked by O—H···O hydrogen bonds, forming R2²(10) rings. Besides this, the mol­ecules form stacks along the [001] direction with C—H···π and C—H···Cl contacts between the stacks. The inter­molecular inter­actions in the crystal were analysed using Hirshfeld surfaces. The most significant contribution to the crystal packing is from H···H contacts (30.8%). [ABSTRACT FROM AUTHOR]

In the title complex, (6,6′-{(1E,1′E)-[ethane-1,2-diylbis(aza­nylyl­idene)]bis(methanylyl­idene)}bis­[2-(tri­fluoro­meth­oxy)phenol]-κ4O,N,N′,O′)nickel(II), [Ni(C18H12F6N2O4)], the nickel(II) ion has a square-planar coordination sphere, being ligated by two N and two O atoms of the Schiff base ligand 6,6′-{(1E,1′E)-[ethane-1,2-diylbis(aza­nylyl­idene)]bis­(methanylyl­idene)}bis­[2-(tri­fluoro­meth­oxy)phenol] (L). Inversion-related mol­ecules are linked by a short Ni···Ni inter­action of 3.2945 (6) Å forming a dimer. In the crystal, the dimers stack up the a axis, with a closest Ni···Ni separation of ca 3.791 Å. There are no other significant inter­molecular inter­actions present. However, the Hirshfeld surface analysis and the two-dimensional fingerprint plots indicate that the packing is dominated by H···F/F···H, H···H, O···H/H···O and C···H/H···C contacts. [ABSTRACT FROM AUTHOR]

In the complex cation of the title compound, [Fe(C27H41N10O3)](PF6)2, the tripodal tris­{4-[1-(2-meth­oxy­eth­yl)imidazol-2-yl]-3-aza­but-3-en­yl}amine ligand is coordinated to an FeII ion through the nitro­gen atoms of three imidazole and three imino groups. The Fe atom exhibits a distorted octa­hedral geometry. In the crystal, L and D anti­podes are arranged in layers in the bc plane. Weak C···F and C—H···F/O contacts exist between the ligands of the complex cation and the PF6− anions, generating a three-dimensional network. At 120 K, the FeII ion is in a low-spin state, with an average Fe—N bond distance of 1.970 (2) Å. On heating, the FeII ion converts to the high-spin state, as demonstrated by magnetic susceptibility measurements [ABSTRACT FROM AUTHOR]

A high temperature spin crossover (Tup = 367 K) was detected in a metal–organic framework [Fe(pz){Ag(CN)2}2]·MeCN (pz = pyrazine). Upon heating, this solvate released acetonitrile guest molecules, which slightly shifted the transition temperature of the complex (Tup = 370 K and Tdown = 356 K). [ABSTRACT FROM AUTHOR]

Spin transitions are a spectacular example of molecular switching that can provoke extreme electronic and structural reorganizations in coordination compounds. A new 3D cyanoheterometallic framework, [Fe(pz){Au(CN)2}2], has been synthesized in which a highly cooperative spin crossover has been observed at 367 and 349 K in heating and cooling modes, respectively. Mössbauer spectroscopy revealed a complete transition between the diamagnetic and paramagnetic states of the iron centres. The low-spin-to-high-spin transition induced a drastic structural distortion involving a large one-directional expansion (ca. 10.6 %) and contraction (ca. 9.6 %) of the lattice. Negative thermal expansion along the c axis was detected below and above the transition temperature. [ABSTRACT FROM AUTHOR]

The diversity of spin crossover (SCO) complexes that, on the one hand, display variable temperature, abruptness and hysteresis of the spin transition, and on the other hand, are spin-sensitive to the various guest molecules, makes these materials unique for the detection of different organic and inorganic compounds. We have developed a homochiral SCO coordination polymer with a spin transition sensitive to the inclusion of the guest 2-butanol, and these solvates with ( R)- and ( S)-alcohols demonstrate different SCO behaviours depending on the chirality of the organic analyte. A stereoselective response to the guest inclusion is detected as a shift in the temperature of the transition both from dia- to para- and from para- to diamagnetic states in heating and cooling modes respectively. Furthermore, the Mössbauer spectroscopy directly visualizes how the metallic centres in a chiral coordination framework differently sense the interaction with guests of different chiralities. [ABSTRACT FROM AUTHOR]

Three complexes [Ca(ClO4)(H2O)Cu5(o-picHA-2H)5(H2O)]ClO4 ( 1), [Pr(NO3)2(py)Cu5(o-picHA-2H)5(py)5]ClO4 ( 2), and [Nd(NO3)(H2O)(py)Cu5(o-picHA-2H)5(py)5](ClO4)2 ·5py ( 3) ( o-picHA = 2-picolinehydroxamic acid) were synthesized in order to retrace structural trends caused by the change of the ionic radius of the central metal ion as well as to assess the effect of the axial ligands on the arrangement of metallacrowns. The complexes were characterized by elemental analysis, ESI-mass spectrometry, IR spectroscopy, and single-crystal X-ray analysis. The heterometallic complexes have 15-MC-5 molecular topology with CaII or LnIII ion in the center of the metallamacrocyclic cavity. The Ca-O and Ln-O bond lengths follow the trend of changes of the corresponding metal ionic radii. While the CaII complex cation (without axial ligands) in 1 is almost flat, the LnIII containing cations in 2 and 3 have a 'partially opened umbrella' environment. [ABSTRACT FROM AUTHOR]

Spin crossover complexes represent spectacular examples of molecular switchable materials. We describe a new approach towards homochiral coordination nanoparticles of [Fe(NH2trz)3](l-CSA)2 (NH2trz = 4-amino-1,2,4-triazole, l-CSA = l-camphorsulfonate) that display an abrupt switch of chiral properties associated with a cooperative spin transition. This is an original method that generates stable and additive-free colloidal solutions of nanoparticles with a spin transition around room temperature. The introduction of a chiral anion to the coordination framework makes these nanoparticles display specific chiro-optical (circular dichroism) properties that are different in high and low spin states. We also illustrate here an effect of the “chiral memory” which is caused by the hysteretic spin transition. In addition, a bistable chiral composite supramolecular system – a [Fe(NH2trz)3](l-CSA)2–CHCl3 gel – is described here. [ABSTRACT FROM AUTHOR]

A series of copper(II) complexes with 3- and 4-picolinehydroxamic acids has been synthesized and characterized by a variety of spectroscopic methods, X-ray structure analysis and magnetic susceptibility measurements. The ligands show the tendency to form 1D- and 2D-polymeric structures with copper(II) ions due to the chelating-and-bridging binding mode involving the (O,O')-hydroxamate chelate formation combined with N-coordination of the pyridine moiety. In some cases the (O, μ2-O') chelating-and-bridging modes are realized, in which either amide or hydroxamic oxygen atoms play a μ2-bridging role. Molecular and crystal structures of two discrete complexes: mononuclear [Cu(3-HPicHA)2(ClO4)2] (1) and binuclear [{Cu(4-HPicHA)(bpy)(ClO4)}2](ClO4)2 (4a), and five coordination polymers catena-[Cu(3-PicHA)(phen)]n(ClO4)n (7), catena-[Cu(4-PicHA)(bpy)]n(OH)n·3.25nH2O (8), catena-[Cu(4-PicHA)(DMSO)2]2n(ClO4)2n (9), [Cu(3-PicHA)(DMSO)(ClO4)]nm·nmDMSO (10), and [{Cu(4-PicHA)(phen)}2]n(ClO4)2n (11) were determined by single crystal X-ray analysis. In structures 1 and 4a the hydroxamate ligands exist in a zwitterionic form with the O-deprotonated hydroxamate groups and protonated pyridine rings. The following types of coordination polymers have been structurally characterized: (i) single-stranded zigzag-shaped 1D polymers (7 and 8); (ii) double-stranded 1D polymer comprising binuclear subunits formed on account of μ2(O)-carbonyl oxygen bridging coordination to the axial position of the copper(II) ion (9); (iii) 2D netted coordination polymers of two different types comprising μ2(O)-bridged binuclear subunits (10 and 11). Magnetic susceptibility measurements (2-300 K) of powdered samples revealed the presence of moderate antiferromagnetic interaction in the binuclear complex 4a (2J = -7.164(6) cm-1), while the coordination polymers exhibit weak antiferromagnetic interaction with a cryomagnetic behaviour obeying the Curie-Weiss law. [ABSTRACT FROM AUTHOR]

The synthesis and characterization of two new CuII complexes with pyrazole ligands formulated as [Cu3(μ-Pz)3(μ3-OH)(Pz)2Cl2][Cu3(μ-Pz)3(μ3-OH)(Pz)2Cl2(DMF)] ·2DMF ( 1) and [Cu3(μ-DMPz)3(DMF)4(OAc)(μ3-OH)(H2O)]+[Cu3(μ-DMPz)3(DMF)(NCS)3(μ3-OH)]- ( 2) (where Pz = 1 H-pyrazole and DMPz = 3, 5-dimethyl-1 H-pyrazole) are reported. The compounds were prepared by the reaction of zero valent copper metal and Pz or DMPz in the dimethylformamide solution in the presence of the different additional components (chloride or thiocyanate ligands). The crystal structures of both compounds were determined by single-crystal X-ray diffraction analysis. Both compounds 1 and 2 are hexanuclear clusters comprising from neutral ( 1) or charged ( 2) trinuclear triangular fragments Cu3(μ3-OH)(μ-Pz)3 of inverse azametallacrowns aza9-MCCuII-3 topology. Nevertheless, they exhibit relevant differences in their molecular structures. The magnetic measurement shows the isotropic antiferromagnetic interaction in 2 with J1 = -140 cm-1 for the cationic and J2 = -109 cm-1 (-2 JSi · Sj model) for the anionic part of the molecule above 100 K and significant influence of antisymmetric exchange at lower temperatures. [ABSTRACT FROM AUTHOR]

New methods are proposed for the synthesis of spin-crossover nano- and micro-objects. Several nano-objects that are based upon the spin-crossover complex [Fe(hptrz)3](OTs)2 (hptrz=4-heptyl-1,2,4-triazole, Ts= para-toluenesulfonyl) were prepared in homogeneous media. The use of various reagents (Triton X-100, PVP, TOPO, and PEGs of different molecular weights) as stabilizing agents yielded materials of different size (6 nm-2 μm) and morphology (nanorods, nanoplates, small spherical particles, and nano- and micro-crystals). In particular, when Triton X-100 was used, a variation in the morphology from nanorods to nanoplates was observed by changing the nature of the solvent. Interestingly, the preparation of the nanorods and nanoplates was always accompanied by the formation of small spherical particles. Alternatively, when PEG was used, 200-400 nm crystals of the complex were obtained. In addition, a very promising polymer-free synthetic method is discussed that was based on the preparation of relatively stable FeII-triazole oligomers in CHCl3. Their specific treatment led to micro-crystals, small nanoparticles, or gels. The size and morphology of all of these objects were characterized by TEM and by dynamic light scattering (DLS) where possible. Their spin-crossover behavior was studied by optical and magnetic measurements. The spin-transition features for large particles (>100 nm) were very similar to that of the bulk material, that is, close to room temperature with a hysteresis width of up to 8 K. The effects of the matrix and/or size-reduction led to modification of the transition temperature and an abruptness of the spin transition for oligomeric solutions and small nanoparticles of 6 nm in size. [ABSTRACT FROM AUTHOR]