Crystal structure of catena-poly[[methanoldioxidouranium(VI)]-µ-2-[5-(2-oxidophen-yl)-1H-1,2,4-triazol-3-yl]acetato-κ2 O:O'].

In the title complex, [U(C10H7N3O3)O2(CH3OH)] n , the UVI cation has a typical penta-gonal-bipyramidal environment with the equatorial plane defined by one N and two O atoms of one doubly deprotonated 2-[5-(2-hy-droxy-phen-yl)-1H-1,2,4-triazol-3-yl]acetic acid ligand, a carboxyl-ate O atom of the symmetry-related ligand and the O atom of the methanol mol-ecule [U-N/Oeq 2.256 (4)-2.504 (5) Å]. The axial positions are occupied by two oxide O atoms. The equatorial atoms are almost coplanar, with the largest deviation from the mean plane being 0.121 Šfor one of the O atoms. The benzene and triazole rings of the tetra-dentate chelating-bridging ligand are twisted by approximately 21.6 (2)° with respect to each other. The carboxyl-ate group of the ligand bridges two uranyl cations, forming a neutral zigzag chain reinforced by a strong O-H⋯O hydrogen bond. In the crystal, adjacent chains are linked into two-dimensional sheets parallel to the ac plane by C/N-H⋯N/O hydrogen bonding and π-π inter-actions. Further weak C-H⋯O contacts consolidate the three-dimensional supra-molecular architecture. In the solid state, the compound shows a broad medium intensity LMCT transition centred around 463 nm, which is responsible for its red colour.

Crystal structure of bis-{2-[5-(3,4,5-tri-meth-oxyphenyl)-4H-1,2,4-triazol-3-yl]pyridine}palladium(II) bis-(tri-fluoro-acetate) tri-fluoro-acetic acid disolvate.

The new palladium(II) complex, [Pd(C16H16N4O3)2](CF3COO)2·2CF3COOH, crystallizes in the triclinic space group P with the asymmetric unit containing half the cation (PdII site symmetry Ci ), one tri-fluoro-actetate anion and one co-crystallized tri-fluoro-acetic acid mol-ecule. Two neutral chelating 2-[5-(3,4,5-tri-meth-oxy-phen-yl)-4H-1,2,4-triazol-3-yl]pyridine ligands coordinate to the PdII ion through the triazole-N and pyridine-N atoms in a distorted trans-PdN4 square-planar configuration [Pd-N 1.991 (2), 2.037 (2) Å; cis N-Pd-N 79.65 (8), 100.35 (8)°]. The complex cation is quite planar, except for the methoxo groups (δ = 0.117 Šfor one of the C atoms). The planar configuration is supported by two intra-molecular C-H⋯N hydrogen bonds. In the crystal, the π-π-stacked cations are arranged in sheets parallel to the ab plane that are flanked on both sides by the tri-fluoro-acetic acid-tri-fluoro-acetate anion pairs. Apart from classical N/O-H⋯O hydrogen-bonding inter-actions, weak C-H⋯F/N/O contacts consolidate the three-dimensional architecture. Both tri-fluoro-acetic moieties were found to be disordered over two resolvable positions with a refined occupancy ratio of 0.587 (1):0.413 (17) and 0.530 (6):0.470 (6) for the protonated and deprotonated forms, respectively.

Synthesis, crystal structure and Hirshfeld surface analysis of the hybrid salt bis-(2-methyl-imidazo[1,5-a]pyridin-2-ium) tetra-chlorido-manganate(II).

The 0-D hybrid salt bis-(2-methyl-imidazo[1,5-a]pyridin-2-ium) tetra-chlorido-manganate(II), (C8H9N2)2[MnCl4] or [L]2[MnCl4], consists of discrete L + cations and tetra-chlorido-manganate(II) anions. The fused heterocyclic rings in the two crystallographically non-equivalent monovalent organic cations are almost coplanar; the bond lengths are as expected. The tetra-hedral MnCl4 2- dianion is slightly distorted with the Mn-Cl bond lengths varying from 2.3577 (7) to 2.3777 (7) Šand the Cl-Mn-Cl angles falling in the range 105.81 (3)-115.23 (3)°. In the crystal, the compound demonstrates a pseudo-layered arrangement of separate organic and inorganic sheets alternating parallel to the bc plane. In the organic layer, pairs of centrosymmetrically related trans-oriented L + cations are π-stacked. Neighboring MnCl4 2- dianions in the inorganic sheet show no connectivity, with the minimal Mn⋯Mn distance exceeding 7 Å. The Hirshfeld surface analysis revealed the prevalence of the non-conventional C-H⋯Cl-Mn hydrogen bonding in the crystal packing.

Organic-inorganic hybrid hexa-chlorido-stannate(IV) with 2-methyl-imidazo[1,5-a]pyridin-2-ium cation.

The hybrid salt bis-(2-methyl-imidazo[1,5-a]pyridin-2-ium) hexa-chlorido-stannate(IV), (C8H9N2)2[SnCl6], crystallizes in the monoclinic space group P21/n with the asymmetric unit containing an Sn0.5Cl3 fragment (Sn site symmetry ) and one organic cation. The five- and six-membered rings in the cation are nearly coplanar; bond lengths in the pyridinium ring of the fused core are as expected; the C-N/C bond distances in the imidazolium entity fall in the range 1.337 (5)-1.401 (5) Å. The octa-hedral SnCl6 2- dianion is almost undistorted with the Sn-Cl distances varying from 2.4255 (9) to 2.4881 (8) Šand the cis Cl-Sn-Cl angles approaching 90°. In the crystal, π-stacked chains of cations and loosely packed SnCl6 2- dianions form separate sheets alternating parallel to (101). Most of the numerous C-H⋯Cl-Sn contacts between the organic and inorganic counterparts with the H⋯Cl distances above the van der Waals contact limit of 2.85 Šare considered a result of crystal packing.

Organic-inorganic hybrid mixed-halide ZnII and CdII tetra-halometallates with the 2-methyl-imidazo[1,5-a]pyridinium cation.

Three isomorphous 0-D hybrid salts, namely, 2-methyl-imidazo[1,5-a]pyridinium tri-chlorido-iodido-zincate(II), (C8H9N2)2[ZnCl3.19I0.81] or [L]2[ZnCl3.19I0.81], (I), 2-methyl-imidazo[1,5-a]pyridinium di-bromido-dichlorido-cadmate(II), (C8H9N2)2[CdBr2.42Cl1.58] or [L]2[CdBr2.42Cl1.58], (II), and 2-methyl-imidazo[1,5-a]pyridinium tri-chlorido-iodido-cadmate(II), (C8H9N2)2[CdCl3.90I0.10] or [L]2[CdCl3.90I0.10], (III), are assembled from discrete 2-methyl-imidazo[1,5-a]pyridinium cations, L +, and mixed-halide tetra-halometallate anions. In the three structures, there are two crystallographically non-equivalent cations that were modelled as being rotationally disordered by 180°. In the lattices of the three compounds, a disordered state exists involving partial substitution of Cl by I for sites 2-4 in (I), Br by Cl for all four sites in (II) and Cl by I for site 2 in (III). In the solid state, the organic and inorganic sheets alternate parallel to the bc plane in a pseudo-layered arrangement. In the organic layer, pairs of centrosymmetic-ally related trans-oriented cations form π-bonded chains. The adjacent tetra-halometallate anions in the inorganic layer show no connectivity with the shortest M⋯M separations being greater than 7 Å. A variety of C-H⋯X-M (X = Cl, Br, I) contacts between the organic and inorganic counterparts provide additional structural stabilization. The title structures are isomorphous with the previously reported structures of the chloride analogues, [L]2[ZnCl4] and [L]2[CdCl4].

NiII mol-ecular complex with a tetra-dentate amino-guanidine-derived Schiff base ligand: structural, spectroscopic and electrochemical studies and photoelectric response.

The new mol-ecular nickel(II) complex, namely, {4-bromo-2-[({N'-[(2-oxidobenzylidene)amino]carbamimidoyl}imino)methyl]phenolato}nickel(II) N,N-di-methyl-formamide solvate monohydrate, [Ni(C15H11BrN4O2)]·C3H7NO·H2O, (I), crystallizes in the triclinic space group P with one mol-ecule per asymmetric unit. The guanidine ligand is a product of Schiff base condensation between amino-guanidine, salicyl-aldehyde and 5-bromo-salicyl-aldehyde templated by Ni2+ ions. The chelating ligand mol-ecule is deprotonated at the phenol O atoms and coordinates the metal centre through the two azomethine N and two phenolate O atoms in a cis-NiN2O2 square-planar configuration [average(Ni-N/O) = 1.8489 Å, cis angles in the range 83.08 (5)-95.35 (5)°, trans angles of 177.80 (5) and 178.29 (5)°]. The complex mol-ecule adopts an almost planar conformation. In the crystal, a complicated hydrogen-bonded network is formed through N-H⋯N/O and O-H⋯O inter-molecular inter-actions. Complex (I) was also characterized by FT-IR and 1H NMR spectroscopy. It undergoes an NiII ↔ NiIII redox reaction at E 1/2 = +0.295 V (vs Ag/AgCl) in methanol solution. In a thin film with a free surface, complex (I) shows a fast photoelectric response upon exposure to visible light with a maximum photovoltage of ∼178 mV.

A novel o-vanillin Fe(III) complex catalytically active in C-H oxidation: exploring the magnetic exchange interactions and spectroscopic properties with different DFT functionals.

The novel complex [FeIIICl(L)2(H2O)] (1) was synthesized by interaction of iron(III) chloride with ethanol solution of o-vanillin (HL) and characterized by IR, UV/Vis spectroscopy, thermogravimetry and single crystal X-ray diffraction analysis. The molecules of 1 in the solid state are joined into supramolecular dimeric units, where a set of strong hydrogen bonds predefines the structure of the dimer according to the "key-lock" principle. From the Hirshfield surface analysis the contribution of π⋯π stacking to the overall stabilization of the dimer was found to be negligible. Broken symmetry DFT calculations suggested the presence of long-range antiferromagnetic interactions (J = -0.12 cm-1 for H = -JS1S2 formalism) occurring through the Fe-O⋯O-Fe pathway, as evidenced by the studies of the model dimers where the water molecules were substituted by acetonitrile and acetone ones. The benchmark studies using a set of literature examples and various DFT functionals revealed the hybrid-GGA B3LYP as the best one for prediction of FeIII⋯FeIII antiferromagnetic exchange couplings of small magnitude. Magnetic susceptibility measurements confirmed antiferromagnetic coupling between the metal atoms in 1 with a coupling constant of -0.35 cm-1. Catalytic studies demonstrated that 1 acts as an efficient catalyst in the oxidation of cyclohexane with hydrogen peroxide in the presence of nitric acid promoter and under mild conditions (yield up to 37% based on the substrate), while tert-butylhydroperoxide (TBHP) and m-chloroperoxybenzoic acid (m-CPBA) as oxidants exhibit less efficiency. Combined UV/TDDFT studies evidence the structural rearrangement of 1 in acetonitrile with the formation of [FeIIICl(L)2(CH3CN)] species. The TDDFT benchmark using nine common DFT functionals and two model compounds (o-vanillin and [FeIII(H2O)6]3+ ion) support the hybrid meta-GGA M06-2X functional as the one most correctly predicting the excited state structure for the Fe(III) complexes, under the conditions studied.

Crystal structure of hexa-kis-(N,N-di-methyl-form-amide-κO)iron(III) µ-chlorido-bis-(tri-chlorido-cadmium).

The title compound, [Fe(C3H7NO)6][Cd2Cl7], crystallizes in the trigonal space group R and is assembled from discrete [Fe(DMF)6]3+ cations (DMF = N,N-di-methyl-formamide) and [Cd2Cl7]3- anions. In the cation, the iron(III) atom, located on a special position of site symmetry, is coordinated by six oxygen atoms from DMF ligands with all Fe-O distances being equal [2.0072 (16) Å]. A slight distortion of the octa-hedral environment of the metal comes from the cis O-Fe-O angles deviating from the ideal value of 90° [86.85 (7) and 93.16 (7)°] whilst all the trans angles are strictly 180°. The central Cl atom of the [Cd2Cl7]3- anion is also located on a special position of site symmetry and bridges two corner sharing, tetra-hedrally coordinated CdII atoms. The two Cd atoms and the central Cl atom are colinear. The two sets of terminal chloride ligands on either side of the dumbbell-like anion are rotated relative to each other by 30°. In the crystal, the cations and anions, stacked one above the other along the c-axis direction, are held in place principally by electrostatic inter-actions. There are also C-H⋯Cl and C-H⋯O inter-actions, but these are rather weak. Of the six crystal structures reported to date for ionic salts of [Fe(DMF)6] n+ cations (n = 2, 3), five contain FeII ions. The title compound is the second example of a stable compound containing the [Fe(DMF)6]3+ cation. The existence of both [Fe(DMF)6]2+ and [Fe(DMF)6]3+ cations shows that the DMF ligand coordination sphere can accommodate changes in the charge and spin states of the metal centre.

Ferro- vs. antiferromagnetic exchange between two Ni(II) ions in a series of Schiff base heterometallic complexes: what makes the difference?

Three new NiII/ZnII heterometallics, [NiZnL'2(OMe)Cl]2 (1), [NiZnL''(Dea)Cl]2·2DMF (2) and [Ni2(H3L''')2(o-Van)(MeOH)2]Cl·[ZnCl2(H4L''')(MeOH)]·2MeOH (3), containing three-dentate Schiff bases as well as methanol or diethanolamine (H2Dea) or o-vanillin (o-VanH), all deprotonated, as bridging ligands were synthesized and structurally characterized. The Schiff base ligands were produced in situ from o-VanH and CH3NH2 (HL'), or NH2OH (HL"), or 2-amino-2-hydroxymethyl-propane-1,3-diol (H4L'''); a zerovalent metal (Ni and Zn in 1, Zn only in 2 and 3) was employed as a source of metal ions. The first two complexes are dimers with a Ni2Zn2O6 central core, while the third compound is a novel heterometallic cocrystal salt solvate built of a neutral zwitterionic ZnII Schiff base complex and of ionic salt containing dinuclear NiII complex cations. The crystal structures contain either centrosymmetric (1 and 2) or non-symmetric di-nickel fragment (3) with NiNi distances in the range 3.146-3.33 Å. The exchange coupling is antiferromagnetic for 1, J = 7.7 cm-1, and ferromagnetic for 2, J = -6.5 cm-1 (using the exchange Hamiltonian in a form H = Js1s2). The exchange interactions in 1 and 2 are comparable to the zero-field splitting (ZFS). High-field EPR revealed moderate magnetic anisotropy of opposite signs: D = 2.27 cm-1, E = 0.243 cm-1 (1) and D = -4.491 cm-1, E = -0.684 cm-1 (2). Compound 3 stands alone with very weak ferromagnetism (J = -0.6 cm-1) and much stronger magnetic anisotropy with D = -11.398 cm-1 and E = -1.151 cm-1. Attempts to calculate theoretically the exchange coupling (using the DFT "broken symmetry" method) and ZFS parameters (with the ab initio CASSCF method) were successful in predicting the trends of J and D among the three complexes, while the quantitative results were less good for 1 and 3.

Organic-inorganic hybrid tetrachlorocadmates as promising fluorescent agents for cross-linked polyurethanes: synthesis, crystal structures and extended performance analysis.

The aim of this work is to apply organic-inorganic hybrid salts made of imidazo[1,5-a]pyridinium-based cations and halometallate anions as fluorescent agents to modify cross-linked polyurethane (CPU) for the creation of flexible photoluminescent films. The use of ionic compounds ensures excellent dispersion of the luminescent components in the polymer matrix and prevents solid-state quenching. The absence of phase segregation makes it possible to fabricate uniformly luminescent films with a large area. To this, new tetrachlorocadmate salts [L]2[CdCl4] (1) and [L']2[CdCl4] (2), where L+ is 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium and [L']+ is 2-methylimidazo[1,5-a]pyridinium cations, have been prepared and characterized by IR, NMR, UV-Vis spectroscopy and single crystal X-ray diffraction. The organic cations resulted from the oxidative cyclization-condensation involving CH3NH2·HCl and 2-pyridinecarbaldehyde in methanol (1), and formaldehyde, CH3NH2·HCl and 2-pyridinecarbaldehyde in an aqueous media (2). In the crystal of 1, loosely packed tetrahedral cations and π-π stacked anions are arranged in separate columns parallel to the a-axis. The pseudo-layered structure of 2 is built of the organic and inorganic layers alternating along the a axis. The adjacent CdCl4 2- anions in the inorganic layer show no connectivity. The organic-inorganic hybrids 1 and 2 were immobilized in situ in the cross-linked polyurethane in low content (1 wt%). The photoluminescent properties of 1 and 2 in the solid state and in the polymer films were investigated. The semi-transparent CPU films, that remain stable for months, retain the photoluminescent ability of both hybrids in the blue region with a prominent red shift in their emission.

Crystal structure and characterization of a new copper(II) chloride dimer with meth-yl(pyridin-2-yl-methyl-idene)amine.

The new copper(II) complex, namely, di-µ-chlorido-bis-{chlorido-[meth-yl(pyri-din-2-yl-methyl-idene)amine-κ2 N,N']copper(II)}, [Cu2Cl4(C7H8N2)2], (I), with the ligand 2-pyridyl-methyl-N-methyl-imine (L, a product of Schiff base condensation between methyl-amine and 2-pyridine-carbaldehyde) is built of discrete centrosymmetric dimers. The coordination about the CuII ion can be described as distorted square pyramidal. The base of the pyramid consists of two nitro-gen atoms from the bidentate chelate L [Cu-N = 2.0241 (9), 2.0374 (8) Å] and two chlorine atoms [Cu-Cl = 2.2500 (3), 2.2835 (3) Å]. The apical position is occupied by another Cl atom with the apical bond being significantly elongated at 2.6112 (3) Å. The trans angles of the base are 155.16 (3) and 173.79 (2)°. The Cu⋯Cu separation in the dimer is 3.4346 (3) Å. In the crystal structure, the loosely packed dimers are arranged in stacks propagating along the a axis. The X-band polycrystalline 77 K EPR spectrum of (I) demonstrates a typical axial pattern characteristic of mononuclear CuII complexes. Compound (I) is redox active and shows a cyclic voltammetric response with E 1/2 = -0.037 V versus silver-silver chloride electrode (SSCE) assignable to the reduction peak of CuII/CuI in methanol as solvent.

Crystal structure of imidazo[1,5-a]pyridinium-based hybrid salt (C13H12N3)2[MnCl4].

A new organic-inorganic hybrid salt [L]2[MnCl4] (I) where L + is the 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, is built of discrete organic cations and tetra-chlorido-manganate(II) anions. The L + cation was formed in situ in the oxidative cyclo-condensation of 2-pyridine-carbaldehyde and CH3NH2·HCl in methanol. The structure was refined as a two-component twin using PLATON (Spek, 2020 ▸) to de-twin the data. The twin law (-1 0 0 0 - 1 0 0.5 0 1) was applied in the refinement where the twin component fraction refined to 0.155 (1). The compound crystallizes in the space group P21/c with two crystallographically non-equivalent cations in the asymmetric unit, which possess similar structural conformations. The fused pyridinium and imidazolium rings of the cations are virtually coplanar [dihedral angles are 0.89 (18) and 0.78 (17)°]; the pendant pyridyl rings are twisted by 36.83 (14) and 36.14 (13)° with respect to the planes of the remaining atoms of the cations. The tetra-hedral MnCl4 2- anion is slightly distorted with the Mn-Cl distances falling in the range 2.3469 (10)-2.3941 (9) Å. The distortion value of 0.044 relative to the ideal tetra-hedron was obtained by continuous shape measurement (CShM) analysis. In the crystal, the cations and anions form separate stacks propagating along the a-axis direction. The organic cations display weak π-π stacking. The anions, which are stacked identically one above the other, demonstrate loose packing; the minimum Mn⋯Mn separation in the cation stack is approximately 7.49 Å. The investigation of the fluorescent properties of a powdered sample of (I) showed no emission. X-band EPR data for (I) at 293 and 77 K revealed broad fine structure signals, indicating moderate zero-field splitting.

A binuclear CuII/CaII thio-cyanate complex with a Schiff base ligand derived from o-vanillin and ammonia.

The new heterometallic complex, aqua-1κO-bis-(µ2-2-imino-methyl-6-meth-oxy-phenolato-1κ2 O 1,O 6:2κ2 O 1,N)bis-(thio-cyanato-1κN)calcium(II)copper(II), [CaCu(C8H8NO2)2(NCS)2(H2O)], has been synthesized using a one-pot reaction of copper powder, calcium oxide, o-vanillin and ammonium thio-cyanate in methanol under ambient conditions. The Schiff base ligand (C8H9NO2) is generated in situ from the condensation of o-vanillin and ammonia, which is released from the initial NH4SCN. The title compound consists of a discrete binuclear mol-ecule with a {Cu(µ-O)2Ca} core, in which the Cu⋯Ca distance is 3.4275 (6) Å. The coordination geometries of the four-coordinate copper atom in the [CuN2O2] chromophore and the seven-coordinate calcium atom in the [CaO5N2] chromophore can be described as distorted square planar and penta-gonal bipyramidal, respectively. In the crystal, O-H⋯S hydrogen bonds between the coordinating water mol-ecules and thio-cyanate groups form a supra-molecular chain with a zigzag-shaped calcium skeleton.

Crystal structures of an imidazo[1,5-a]pyridinium-based ligand and its (C13H12N3)2[CdI4] hybrid salt.

The monocation product of the oxidative condensation-cyclization between two mol-ecules of pyridine-2-carbaldehyde and one mol-ecule of CH3NH2·HCl in methanol, 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium, was isolated in the presence of metal ions as bis-[2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridin-2-ium] tetra-iodo-cadmate, (C13H12N3)2[CdI4], (I), and the mixed chloride/nitrate salt, bis-[2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridin-2-ium] 1.5-chlor-ide 0.5-nitrate trihydrate, 2C13H12N3 +·1.5Cl-·0.5NO3 -·3H2O, (II). Hybrid salt (I) crystallizes in the space group P21/n with two [L]2[CdI4] mol-ecules in the asymmetric unit related by pseudosymmetry. In the crystal of (I), layers of organic cations and of tetra-halometallate anions are stacked parallel to the ab plane. Anti-parallel L + cations disposed in a herring-bone pattern form π-bonded chains through aromatic stacking. In the inorganic layer, adjacent tetra-hedral CdI4 units have no connectivity but demonstrate close packing of iodide anions. In the crystal lattice of (II), the cations are arranged in stacks propagating along the a axis; the one-dimensional hydrogen-bonded polymer built of chloride ions and water mol-ecules runs parallel to a column of stacked cations.

Long magnetic relaxation time of tetracoordinate Co2+ in imidazo[1,5-a]pyridinium-based (C13H12N3)2[CoCl4] hybrid salt and [Co(C13H12N3)Cl3] molecular complex.

The novel organic-inorganic hybrid salt [L]2[CoCl4] (1) and molecular complex [CoLCl3] (2), where L+ is 2-methyl-3-(pyridin-2-yl)imidazo[1,5-a]pyridinium cation, feature simple {CoCl4} and {CoCl3N} tetrahedral environments of negligible (1) and a slightly higher distortion (2) that are responsible for rather low positive magnetic anisotropy of CoII ion with D/hc = 12.1(6) (1) and 19.4(15) cm-1 (2). Both compounds exhibit field-induced slow magnetic relaxation with three relaxation channels [low- (LF), intermediate- and high-frequency (HF) modes] that is frequency and field dependent. With the increased DC field, the peaks referring to the LF relaxation path are moved to lower frequencies so that the applied DC field causes prolongation of the relaxation time. The opposite is true for the HF relaxation branch: the peak is moved to higher frequencies. Considering the simplicity of the coordination environment and moderate magnetic anisotropy of the metal ion in 1 and 2, the compounds are unique with respect to the remarkably long relaxation time for a given applied DC field and temperature: τLF = 0.54(4) s at BDC = 1.0 T and T = 2.0 K for 1, and τLF = 1.8(2) s at BDC = 1.2 T and T = 1.9 K for 2.

Crystal structure of bis-{µ-2-meth-oxy-6-[(methyl-imino)-meth-yl]phenolato}bis-({2-meth-oxy-6-[(methyl-imino)-meth-yl]phenolato}nickel(II)) involving different coordination modes of the same Schiff base ligand.

The structure of the title compound, [Ni2(C9H10NO2)4], is built up by discrete centrosymmetric dimers. Two nitro-gen and three oxygen atoms of two Schiff base ligands singly deprotonated at the phenolate site form a square-pyramidal environment for each metal atom. The ligands are bonded differently to the metal centre: one of the phenolic O atoms is bound to one nickel atom, whereas another bridges the two metal atoms to form the dimer. The Ni-N/O distances fall in the range 1.8965 (13)-1.9926 (15) Å, with the Ni-N bonds being slightly longer; the fifth contact of the metal to the bridging phenolate oxygen atom is substanti-ally elongated [2.533 (1) Å]. A similar coordination geometry was observed in the isomorphous Cu analogue previously reported by us [Sydoruk et al. (2013 ▸). Acta Cryst. E69, m551-m552]. In the crystal, the [Ni2 L 4] mol-ecules form sheets parallel to the ab plane with the polar meth-oxy groups protruding into the inter-sheet space and keeping the sheets apart. Within a sheet, the mol-ecules are stacked relative to each other in such a way that the Ni2O2 planes of neighbouring mol-ecules are orthogonal.

Crystal structure of di-chlorido-bis-{µ-2-meth-oxy-6-[(methyl-imino)-meth-yl]phenolato}{2-meth-oxy-6-[(methyl-imino)-meth-yl]phenolato}cadmium(II)cobalt(III) monohydrate.

The title compound, [CoCd(C9H10NO2)3Cl2]·H2O, is a solvatomorph of the corresponding hemihydrate recently published by us [Nesterova et al. (2018 ▸). Appl. Cat. A, 560, 171-184]. The current structure reveals different cell parameters and space group compared with the published one while both are monoclinic with almost the same cell volume. The title compound is formed of discrete neutral dinuclear mol-ecules with no crystallographically imposed symmetry and water mol-ecules of crystallization. The overall geometry about the cobalt(III) ion is octa-hedral with an N3O3 environment; each ligand acts as a meridional ONO donor. The CdII coordination sphere approximates an irregular square pyramid with a chlorine atom at the apex. There is significant shortening of a Cd-O bond length to the oxygen atom of the methoxo group on one of the ligands [2.459 (3) Å] compared to the corresponding distance in the published structure [2.724 (7) Å], while other Cd-Cl/N/O bonds remain roughly the same. In the crystal lattice, the heterometallic mol-ecules, which are related by the crystallographic n-glide plane and inter-linked by weak hydrogen bonds to solvent water mol-ecules, form columns along [101]. Adjacent columns lie anti-parallel to each other.

Formaldehyde-aminoguanidine condensation and aminoguanidine self-condensation products: syntheses, crystal structures and characterization.

Guanidine is the functional group on the side chain of arginine, one of the fundamental building blocks of life. In recent years, a number of compounds based on the aminoguanidine (AG) moiety have been described as presenting high anticancer activities. The product of condensation between two molecules of AG and one molecule of formaldehyde was isolated in the protonated form as the dinitrate salt (systematic name: 2,8-diamino-1,3,4,6,7,9-hexaazanona-1,8-diene-1,9-diium dinitrate), C3H14N82+·2NO3-, (I). The cation lacks crystallographically imposed symmetry and comprises two terminal planar guanidinium groups, which share an N-C-N unit. Each cation in (I) builds 14 N-H...O hydrogen bonds and is separated from adjacent cations by seven nitrate anions. The AG self-condensation reaction in the presence of copper(II) chloride and chloride anions led to the formation of the organic-inorganic hybrid 1,2-bis(diaminomethylidene)hydrazine-1,2-diium tetrachloridocuprate(II), (C2H10N6)[CuCl4], (II). Its asymmetric unit is composed of half a diprotonated 1,2-bis(diaminomethylidene)hydrazine-1,2-diium dication and half a tetrachloridocuprate(II) dianion, with the CuII atom situated on a twofold rotation axis. The planar guanidinium fragments in (II) have their planes twisted by approximately 77.64 (5)° with respect to each other. The tetrahedral [CuCl4]2- anion is severely distorted and its pronounced `planarity' must originate from its involvement in multiple N-H...Cl hydrogen bonds. It was reported that [CuCl4]2- anions, with a trans-Cl-Cu-Cl angle (Θ) of ∼140°, are yellow-green at room temperature, with the colour shifting to a deeper green as Θ increases and toward orange as Θ decreases. Brown salt (II), with a Θ value of 142.059 (8)°, does not fit the trend, which emphasizes the need to take other structural factors into consideration. In the crystal of salt (II), layers of cations and anions alternate along the b axis, with the minimum Cu...Cu distance being 7.5408 (3) Šinside a layer. The structures of salts (I) and (II) were substantiated via spectroscopic data. The endothermic reaction involved in the thermal decomposition of (I) requires additional oxygen. The title salts may be useful for the screening of new substances with biological activity.

Field-Assisted Slow Magnetic Relaxation in a Six-Coordinate Co(II)-Co(III) Complex with Large Negative Anisotropy.

The reaction of Co(CH3COO)2·4H2O with the Schiff base ligand LH4 derived from o-vanillin and tris(hydroxymethyl)aminomethane produces the dinuclear mixed-valence complex [CoIICoIII(LH2)2(CH3COO)(H2O)](H2O)3 (1), which has been investigated using IR spectroscopy, X-ray crystallography, temperature-dependent magnetic susceptibility, magnetization, HFEPR spectroscopy, and ac susceptibility measurements at various frequencies, temperatures, and external magnetic fields. The structure of 1 consists of neutral molecules in which two cobalt ions with distorted octahedral geometries, CoIIO6 and CoIIIN2O4, are bridged by two deprotonated -CH2O- groups of the two LH22- ligands. 1 completes a series with Cl, Br, NO3, and NCS anions published before by different authors. Low-temperature HFEPR measurements reveal that the ground electronic state of the Co(II) center in 1 is a highly anisotropic Kramers doublet; the effective g values of 7.18, 2.97, and 1.96 are frequency-independent over the frequency ranges 200-630, 200-406, and 200-300 GHz for the highest, intermediate, and lowest geff values, respectively. The two lower values were not seen at higher frequencies because the magnetic field was not high enough. Temperature-dependent magnetic susceptibility and field-dependent magnetization data confirm high magnetic anisotropy of the easy axis type. Complex 1 behaves as a single-ion magnet under a small applied external field and demonstrates two relaxation modes that strongly depend on the applied static dc field. The observation of multiple relaxation pathways clearly distinguishes 1 from the Cl and Br analogues.

Crystal structure of 4,10-dimeth-oxy-13-methyl-6H,12H-6,12-epimino-dibenzo[b,f][1,5]dioxocine.

The title compound, C17H17NO4, lacks crystallographic symmetry with one mol-ecule per asymmetric unit. The mol-ecule exists in a folded butterfly-like conformation; the benzene rings form a dihedral angle of 84.72 (7)°. The central eight-membered imino-bridged dioxocin ring adopts a twisted-boat conformation. In the crystal, inversion-related mol-ecules are linked by pairs of weak C-H⋯O hydrogen bonds, forming double-stranded chains parallel to the a axis.