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].

Hybrid Cu-Containing Compounds Based on Lacunary Strandberg Anions: Synthesis under Mild Conditions, Crystal Structure, and Magnetic Properties.

A one-pot reaction of a copper source (metallic powder Cu0 or Cu2+ salts) and bpy (bpy = 2,2'-bipyridine) in the presence of (NH4)2HPO4 and (NH4)6Mo7O24·4H2O yields heterometallic hybrid compounds of the general type {[Cu(bpy)n(H2O)m]p[P2MoxOy]}. The structures exhibit a number of phosphomolybdate POMs including not only a common Strandberg anion [P2Mo5O23]6- but also its unprecedented bi- and trilacunary derivatives [P2Mo3O18]8- and [P2Mo2O15]8-. The structural determinants including the metal source (copper powder vs copper salts), counterion of the salts, and stoichiometry of the reagents were examined. An ex situ EPR study revealed the formation of different CuII complexes in the reaction mixture depending on the copper precursor. The obtained compounds have been found to possess selectivity toward the sorption of methylene blue in a mixture of organic dyes. DC magnetic measurements of 1-3 indicate rather strong antiferromagnetic metal-metal exchange interactions. Compound 1 exhibits field-induced slow magnetic relaxation in AC magnetic measurements, which is a rarely observed phenomenon among Cu(II) complexes.

Field-induced mononuclear cobalt(II) single-molecule magnet (SMM) based on a benzothiadiazole-ortho-vanillin ligand.

A unique π-conjugated benzothiadiazole-ortho-vanillin ligand (HL), characterized by single crystal X-ray diffraction and DFT calculations, has been prepared by condensation between 4-amino-benzothiadiazole (BTD) and ortho-vanillin. Its reaction with cobalt(II) acetate afforded the complex of formula [CoL2]·CH2Cl2 (1), for which the coordination environment of the cobalt centre is a distorted octahedron and the ligand acts as a monoanionic tridentate NNO chelate in its phenolate form. Intermolecular π-π stacking interactions between the π-conjugated BTD units provide an antiferromagnetic coupling pathway, as indicated by the analysis of the dc magnetic measurements of a crystalline sample of the complex and supported by DFT type calculations. The static magnetic behaviour of 1 is analysed according to spin-orbit coupling and zero-field splitting models. Remarkably, the complex exhibits slow relaxation of the magnetization under dc applied magnetic fields being thus a new example of field-induced mononuclear single-molecule magnet (SMM).

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 bis-chelate o-vanillin-2-ethano-lamine copper(II) complex bearing both imine and amine forms of the ligand.

The mol-ecular bis-chelate complex (2-{[(2-hy-droxy-ethyl-κO)amino-κN]meth-yl}-6-meth-oxy-phenolato-κO)(2-{[(2-hy-droxy-eth-yl)imino-κN]meth-yl}-6-meth-oxy-phenolato-κO)copper(II), [Cu(C10H14NO3)(C10H12NO3)] or [Cu(HL im)(HL am); HL im = C10H14NO3; HL am = C10H12NO3, represents the first compound containing a salicyl-idene-2-ethano-lamine type ligand in both imino HL im (Schiff base) and amino HL am (reduced Schiff base) forms that has been structurally characterized on the basis of X-ray data. Two mol-ecules of the monodeprotonated ligands coordinate the CuII ion in an (N,O phen)-bidentate and an (N,O phen,O alc)-tridentate fashion in the case of the imino and amino forms, respectively. The shape of the CuN2O3 coordination polyhedron is a distorted square-pyramid (geometry index τ5 = 0.26). Inter-molecular N-H⋯O and O-H⋯O hydrogen bonds, involving H atoms of the amino and hy-droxy-ethyl groups, create a two-dimensional supra-molecular array extending parallel to (010).

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.

Hybrid compound based on diethylenetriaminecopper(ii) cations and scarce V-monosubstituted ß-octamolybdate as water oxidation catalyst.

Herein, we report on a new hybrid compound (NH4){[Cu(dien)(H2O)2]2[ß-VMo7O26]}·1.5H2O (1), where dien = diethylenetriamine, containing an extremely rare mixed-metal pseudo-octamolybdate cluster. An ex situ EPR spectroscopy provided insights into the formation of paramagnetic species in reaction mixture and in solution of 1. The magneto-structural correlations revealed weak antiferromagnetic exchange interactions between the [Cu(dien)]2+ cations transmitted by intermolecular pathways. The cyclic voltammetry showed the one-electron process associated with the Cu3+/Cu2+ oxidation followed by the multi-electron catalytic wave due to water oxidation with a faradaic yield of 86%. The title compound was thus employed in homogeneous water oxidation catalysis using tris(bipyridine)ruthenium photosensitizer. At pH 8.0, efficiency of the catalytic system attained 0.19 turnovers per second supported by the relatively mild water oxidation overpotential of 0.54 V.

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 structure of bis(µ-{2-[(5-bromo-2-oxido-benzyl-idene)amino]-eth-yl}sulfanido-κ3 N,O,S){2,2'-[(3,4-di-thia-hexane-1,6-di-yl)bis-(nitrilo-methanylyl-idene)]bis-(4-bromo-phenolato)-κ4 O,N,N',O'}dicobalt(III) di-methyl-formamide monosolvate.

The title binuclear CoIII complex, [Co2(C9H8BrNOS)2(C18H16Br2N2O2S2)]·C3H7NO, with a Schiff base ligand formed in situ from cyste-amine (2-amino-ethane-thiol) and 5-bromo-salicyl-aldehyde crystallizes in the space group P21. It was found that during the synthesis the ligand undergoes spontaneous oxidation, forming the new ligand H2 L' having an S-S bond. Thus, the asymmetric unit consists of one Co2(L)2(L') mol-ecule and one DMF solvent mol-ecule. Each CoIII ion has a slightly distorted octa-hedral S2N2O2 coordination geometry. In the crystal, the components are linked into a three-dimensional network by several S⋯ Br, C⋯ Br, C-H⋯Br, short S⋯C (essentially shorter than the sum of the van der Waals radii for the atoms involved) contacts as well by weak C-H⋯O hydrogen bonds. The crystal studied was refined as an inversion twin.

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.

Versatile coordination behaviour of the chloro-tetrazine-picolylamine ligand: mixed-valence binuclear Cu(i)/Cu(ii) complexes.

The 3-Cl-6-amino-(2'-picolyl)-1,2,4,5-tetrazine ligand HL1 has been synthesized and structurally characterized. Its versatile coordination behavior has been evidenced through reactions with Cu(Hfac)2 and Cu(triflate)2 precursors, which provided mixed-valence bimetallic Cu1.5Cu1.5 complexes [Cu2(µ-Cl)(L1)2] 2 and [Cu2(µ-triflate)(L1)2] 5. Changing the Cu(ii) precursor and the solvent leads to the formation of mononuclear octahedral Cu(ii) complexes [CuCl2(HL1)2]·2CH3CN 3 and [Cu(Hfac)2(HL1)] 4, in which only the amino-pyridine unit is involved in the coordination of the metal center. In contrast, in complexes 2 and 5, the ligands are deprotonated and bridge the metal centers as pyridine-amido-tetrazine fragments, while a bridging chloride or triflate ligand completes the coordination sphere of the metal ions. The Cu-Cu distances of 2.4313(4) Å in 2 and 2.5198(10) Å in 5 lie among the shorter values within mixed-valence bimetallic Cu complexes. Mixed-valence character is strongly supported by DFT calculations, showing the equal repartition of the unpaired electron between the two metal centers.

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.

Co-existence of ferro- and antiferromagnetic interactions in a hexanuclear mixed-valence CoMnMn cluster sustained by a multidentate Schiff base ligand.

The successful utilization of the "direct synthesis" approach yielded the unprecedented hexanuclear complex of formula [Co2MnMn(L1)4Cl2(µ3-O)2(dmf)4]·2dmf (1) (H3L is the Schiff base derived from the condensation of salicylaldehyde and 3-aminopropane-1,2-diol). Single crystal X-ray analysis revealed that 1 crystallizes in the monoclinic system P21/c and it contains a rare mixed-valence {CoMnMn(µ2-O)8(µ3-O)2} core where all metal ions are linked through the phenolato and alkoxo groups of the L3- ligand. Besides the charge balance resulting from the X-ray structure, the oxidation state of the metal ions has been confirmed by XPS spectroscopy. Cryomagnetic studies indicate the coexistence of ferro- (MnIV-MnII, J2 = +1.10(3) cm-1, J3 = +2.19(3) cm-1; MnII-MnII, j = +0.283(3) cm-1) and antiferromagnetic interactions (MnIV-MnIV, J1 = -17.31(4) cm-1), with the six-coordinate CoIII ions being diamagnetic. DFT type calculations were carried out to substantiate these values. The energy diagram for the different spin states using the best-fit parameters shows the occurrence of six low-lying spin states (S = 0-5) which are close in energy but clearly separated from the remaining ones, with the ground spin state being S = 5. Complex 1 is found to be the first example where weak ferromagnetic exchange between MnII ions through the long -O-MnIV-O- pathway takes place.

Tris(µ2-2-meth-oxy-6-{[(2-sulfido-eth-yl)imino]meth-yl}phenolato)trinickel(II) di-methyl-formamide monosolvate: crystal structure, spectroscopic characterization and anti-bacterial activity.

The title trinuclear nickel(II) complex, [Ni3(C10H11NO2S)3]·C3H7NO, with a Schiff base ligand formed in situ from 2-amino-ethane-thiol and o-vanillin crystallizes in the ortho-rhom-bic space group Pbca. Its asymmetric unit consists of one neutral Ni3 L 3 mol-ecule and one DMF solvent mol-ecule. The solid-state organization of the complex can be described as an insertion of the solvent mol-ecules within the crystallographically independent trinuclear NiII species. Several C-H⋯π edge-to-face inter-actions and π-π stacking inter-actions link the components in the crystal. A first example of a short inter-molecular C-H⋯Ni contact is found. Anti-bacterial in vitro screening revealed that the title compound has anti-bacterial activity, the best effect being against Acinetobacter baumannii.