Low pH constructed Co(ii) and Ni(ii) 1D coordination polymers based on Cα-substituted analogues of zoledronic acid: structural characterization, and spectroscopic and magnetic properties.

Three novel coordination compounds based on α,α-disubstituted analogues of zoledronic acid with a cyclopropane (cpp) or cyclobutane (cbt) ring on the Cα carbon, isomorphous [Co(H2cppZol)(H2O)]·H2O (1a), [Ni(H2cppZol)(H2O)]·H2O (1b) and [Co(H2cbtZol)(H2O)]·H2O (2a), were synthesized under hydrothermal conditions at low pH. Single-crystal X-ray diffraction analysis revealed that all the compounds had a 1D double zig-zag chain architecture with an 8 + 8 ring motif formed by alternately arranged symmetrical (-O-P-O-)2 bridges linking equivalent octahedral metal centres. Both the ligand coordination mode and chain architecture displayed by 1a, 1b and 2a are unique among 1D [M(H2L)(H2O) x ]·yH2O coordination polymers based on nitrogen-containing bisphosphonates reported so far. All the compounds exhibit similar decomposition pathways upon heating with thermal stabilities decreasing in the order 1b > 1a > 2a. The IR spectra revealed that lattice water release above 227, 178 and 97 °C, respectively, does not change the chain architecture leaving them intact up to ca. 320, 280 and 240 °C. Magnetic behaviour investigations indicated that 1a, 2a and 1b exhibit weak alternating antiferromagnetic-ferromagnetic exchange interactions propagated between the magnetic centres through double (-O-P-O-)2 bridges. The boundary between antiferro- and ferromagnetic couplings for the Co-O⋯O-Co angle in 1a and 2a was estimated to be ca. 80°. This value is also applicable for recently reported [M3(HL)2(H2O)6]·6H2O (M = Co, Ni) complexes based on α,α-disubstituted analogues of zoledronic acid and can be used to the explain magnetic behaviour of 1b.

Two isomorphous Co(ii) coordination polymers based on new α,α-disubstituted derivatives of zoledronic acid: synthesis, structures and properties.

Two novel α,α-disubstituted derivatives of zoledronic acid, namely 1-hydroxy-2-(1H-imidazol-1-yl)-2-methylpropylidene-1,1-diphosphonic acid (H4L1) and 1-hydroxy-2-[1-(1H-imidazol-1-yl)cyclopropyl]ethylidene-1,1-diphosphonic acid (H4L2) were synthesized and structurally characterized by single-crystal X-ray diffraction. The reaction of cobalt acetate with H4L1 and H4L2 carried out under hydrothermal conditions afforded two isomorphous Co3(HL1)2(H2O)6·6H2O (1a) and Co3(HL2)2(H2O)6·6H2O (2a) complexes. Both compounds are characterized by means of X-ray crystallography, IR and NIR-Vis-UV spectroscopic methods. Furthermore, their magnetic properties and thermal stabilities are reported. The crystals of 1a and 2a feature infinite 1D polymeric chains built from alternately arranged dinuclear [Co2(HL1/HL2)(H2O)2]2 units and {Co1O6} octahedra running along the [1[combining macron]10] crystallographic direction. In both compounds, crystallographically distinct Co1 and Co2 atoms are six-coordinated. As is reflected in T values (T - index of tetragonality), the coordination environment of Co1 generates a slightly elongated octahedron (T = 0.94), whereas a slightly compressed octahedron (T = 1.06 for 1a and 1.05 for 2a) is formed around Co2. An assumption that the d-d type absorption is mainly attributed to the inversion related Co2 centers, whose population is two times higher than that of Co1, afforded a good correlation between calculated transition energies and experimental NIR-Vis-UV spectra. The magnetic susceptibility measurements analyzed in terms of a spin-3/2 Heisenberg trimer chain revealed that Co1Co2 interactions within the trimer are antiferromagnetic whereas Co2Co2 intertrimer interactions are ferromagnetic.

L-tyrosinatonickel(II) complex: synthesis and structural, spectroscopic, magnetic, and biological properties of 2{[Ni(L-Tyr)2(bpy)]}·3H2O·CH3OH.

The complex 2{[Ni(L-Tyr)2(bpy)]}·3H2O·CH3OH [1, where L-Tyr = L-tyrosine; bpy = 2,2'-bipyridine (2,2'-bpy)] was obtained in crystalline form and characterized by X-ray and spectroscopic (FT-IR, NIR-vis-UV, and HFEPR) and magnetic methods. The complex crystallized in the hexagonal system with a = b = 12.8116(18) Å, c = 30.035(6) Å, and space group P3221. The six-coordination sphere around the Ni(2+) ion is formed by two N and two O L-tyrosinato atoms and completed by two N atoms of the 2,2'-bpy molecule. Neighboring [Ni(L-Tyr)2(bpy)] units are joined via weak hydrogen bonds, which create a helical polymeric chain. The coordinated atoms form a strongly distorted cis-NiN2N2'O2 octahedral chromophore. The solid-state electronic spectrum of complex 1 was analyzed assuming D2h symmetry, and the observed bands were assigned to (3)B1g → (3)Ag, (3)B1g → (3)B3g, (3)B1g → (3)B2g, (3)B1g → (3)B3g, (3)B1g → (3)B1g, and (3)B1g → (3)B2g transitions for the I and II d-d bands, respectively. The crystal-field parameters found for D2h symmetry are Dq = 1066 cm(-1), Ds = 617 cm(-1), Dt = -93 cm(-1), B22 = 7000 cm(-1), and Racah B = 812 cm(-1). Magnetic studies revealed the occurrence of hydrogen-bonded metal pairs. The spin Hamiltonian parameters D = -3.262 cm(-1) and E = -0.1094 cm(-1), determined from high-field, high-frequency electron paramagnetic resonance spectra, together with a weak antiferromagnetic exchange parameter J = -0.477 cm(-1), allowed us to reproduce the powder magnetic susceptibility and field-dependent magnetization of the complex. The biological activity of 1 has been tested by using the Fusarium solani, Penicillium verrucosum, and Aspergillus flavus fungi strains and Escherichia coli, Pseudomonas fluorescens, Serratia marcescens, and Bacillus subtilis bacterial strains.

Titanocene as a precursor for a cyclopentadienyl-free titanium(III)-manganese(II) cluster: a new approach for nano-size materials.

A simple and unique route to access the heterometallic cluster [Mn4Ti4(micro-Cl)2(micro3,eta2-L)2(micro,eta2-L)10Cl6] (1) with two Mn2Ti2 butterfly core motifs is reported. This method comprises elimination of the Cp ring from Cp2TiCl2 as CpH in the presence of metallic Mn in 2-methoxoethanol (LH) as a proton source. Complex 1 belongs to a group of magnetic clusters, which consists of two weakly interacting M4 subunits.

Cyclopentadienyl/alkoxo ligand exchange in group 4 metallocenes: a convenient route to heterometallic species.

A simple and efficient strategy for the synthesis of nonorganometallic heterometallic clusters from cheap organometallic precursors is reported. This unique synthetic method involves elimination of the cyclopentadienyl ring from Cp(2)MCl(2) (M = Ti, Zr, Hf) as CpH in the presence of M'L(2) or M'L'(2) (M' = Ca, Sr, Mn; CH(3)OCH(2)CH(2)OH = LH or (CH(3))(2)NCH(2)CH(2)OH = L'H) in an alcohol as a source of protons. In the reactions presented, a series of compounds, [Ca(4)Ti(2)(mu(6)-O)(mu(3),eta(2)-L)(8)(eta-L)(2)Cl(4)] (1), [Sr(4)Hf(2)(mu(6)-O)(mu(3),eta(2)-L)(8)(eta-L)(2)(eta-LH)(4)Cl(4)] (2), [Ca(4)Zr(2)(mu(6)-O)(mu-Cl)(4)(mu,eta(2)-L)(8)Cl(2)] (3), [Sr(4)Ti(2)(mu(6)-O)(mu(3),eta(2)-L)(8)(eta-L)(2)(eta-LH)(2)Cl(4)] (4), [Ca(4)Zr(2)Cp(2)(mu(4)-Cl)(mu-Cl)(3)(mu(3),eta(2)-L)(4)(mu,eta(2)-L)(4)Cl(2)] (5), [CaTiCl(2)(mu,eta(2)-L')(3)(eta-L'H)(3)][L'] (6), [Ca(2)Ti(mu,eta(2)-L')(6)Cl(2)] (7), [Mn(4)Ti(4)(mu-Cl)(2)(mu(3),eta(2)-L)(2)(mu,eta(2)-L)(10)Cl(6)] (8), and [Mn(10)Zr(10)(mu(4)-O)(10)(mu(3)-O)(4)(mu(3),eta(2)-L)(2)(mu,eta(2)-L)(16)(mu,eta-L)(4)(eta-L)(2)Cl(8)] (9), were obtained in good yield. All of the complexes were characterized by elemental analysis, IR and NMR spectroscopy, and single-crystal X-ray structural analysis. Complex 8 belongs to a group of magnetic clusters that consists of Mn(4) subunits held together by two mu-Cl bridges. Compounds 6 and 7 underwent thermal decomposition, yielding an alternative source for some heterometallic oxides, which were analyzed by X-ray powder diffraction.

Titanium-manganese compound with a chiral Mn3Ti center.

We have shown here for the first time a facile route to the molecular compound [Mn3Ti(mu3-OCH2CH2OCH3)2(mu-OCH2CH2OCH3)3(mu-Cl)Cl2(OiPr)2] with a Mn3Ti motif, where the Ti atom is in the chiral position and the Mn atoms occupy nonchiral sites.

Syntheses, structure, and properties of a manganese-calcium cluster containing a Mn4Ca2 core.

We describe here a novel, simple, efficient self-assembly method for the in situ generation of [Mn4Cl4(micro-OCH2CH2OMe)4(EtOH)4] and [Mn4(micro-Cl)Cl3(micro-OCH2CH2OMe)4(HOCH2CH2OMe)3]2 cubane-type compounds which react readily with calcium species to form cluster [Mn4Ca2Cl4(micro-OCH2CH2OMe)8], the calcium atoms attached to the Mn4 unit of flatten out the cubane inducing significant conformational changes.

Structural, spectroscopic, and magnetic study of bis(9,10-dihydro-9-oxo-10-acridineacetate)bis(imidazole)bis(methanol) nickel(II).

The mixed ligand complex [Ni(CMA)2(im)2(MeOH)2] (where CMA = 9,10-dihydro-9-oxo-10-acridineacetate ion, im = imidazole) was prepared, and its crystal and molecular structure were determined. The nickel ions are hexa-coordinated by four oxygen atoms of the carboxylate and hydroxyl groups and by two imidazole nitrogen atoms, to form a distorted octahedral arrangement. The structure consists of a one-dimensional network of the complex molecules connected by strong intermolecular hydrogen bonds. The weak intermolecular C-H...X hydrogen bonds and stacking interactions make up the 2-D structure. Very strong intramolecular hydrogen bonds significantly affect the geometry and vibrational characteristics of the carboxylate group. The UV-vis-NIR electronic spectrum was deconvoluted into Gaussian components. Electronic bands of the Ni(II) ion were assigned to suitable spin-allowed transitions in the D4h symmetry environment. The single ion zero-field splitting (ZFS) parameters for the S = 1 state of Ni(II), as well as the g components, have been determined by high-field and high-frequency EPR (HF-HFEPR) spectroscopy over the frequency range of 52-432 GHz and with the magnetic fields up to 14.5 T: D = 5.77(1) cm-1, E = 1.636(2) cm-1, gx = 2.29(1), gy = 2.18(1), and gz = 2.13(1). These values allowed us to simulate the powder magnetic susceptibility and field-dependent magnetization of the complex.