Isostructural Zinc Research Articles

Syntheses and Crystal Structures of Two Isostructural Zinc(II) Complexes With Schiff-bases 2-Bromo-4-chloro-6-[(3-methylaminopropylimino)methyl]phenol and 2,4-Dichloro-6-[(3-methylaminopropylimino)methyl]phenol

Two new isostructural mononuclear zinc(II) complexes, [Zn(C11H14Cl2N2O)(NCS)(CH3COO)] and [Zn(C11H14BrClN2O) (NCS)(CH3COO)], have been synthesized from the Schiff-bases 2-bromo-4-chloro-6-[(3-methylaminopropylimino)methyl]phenol and 2,4-dichloro-6-[(3-methylaminopropylimino)methyl]phenol, respectively. Both complexes were characterized by elemental analysis, IR spectra and single-crystal X-ray diffraction. The Zn atom in each of the complexes is coordinated by one phenolic oxygen atom and one imine nitrogen atom of a Schiff-base ligand, one nitrogen atom of a thiocyanate anion, and one oxygen atom of an acetate ligand, giving a tetrahedral geometry.

Zinc 4-Carboxyphenylphosphonates with Pillared Layered Framework Structures Containing Large 12-Membered Rings Built Up from Tetranuclear Zn4 Clusters and CPO3 Linkages

Two isostructural zinc phosphonates [Zn(H2O)6][Zn8(OOCC6H4PO3)6(4,4′-bipy)] (1) and (dabcoH)2[Zn8(OOCC6H4PO3)6]·6H2O (2) (dabco = 1,4-diazabicyclo[2.2.2]octane) have been obtained by hydrothermal reactions of zinc sulfate and 4-carboxyphenylphosphonic acid in the presence of additional organic ligands 4,4′-bipyridine and 1,4-diazabicyclo[2.2.2]octane, respectively. Both show pillared layered open framework structures. The inorganic layers are of particular interest in which the highly symmetric tetranuclear clusters, composed of corner-sharing {ZnO4} and {ZnO3N} tetrahedra, are linked by {CPO3} tetrahedra through corner-sharing, forming an inorganic layer containing large 12-membered windows. The [Zn(H2O)6]2+ cations (for 1) or lattice water (for 2) reside in the cavities generated by the 12-membered windows and the organic pillars.

X-ray study of the light-induced metastable state of a spin-crossover compound

Iron(II) complexes exhibiting thermal spin crossover may be converted from the1A1low-spin (LS) state to the5T2high-spin (HS) state by irradiation with green light (light-induced excited spin-state trapping, LIESST). The lifetime of the metastable LIESST state may be sufficiently long for X-ray diffraction study. The lattice parameters of a single crystal of [Fe(ptz)6](BF4)2(ptz = propyltetrazole) were measured between 300 and 10 K, while the crystal changed from the HS to the LS state near 135 K. Using the green light (514 nm) of an argon-ion laser, the crystal was quantitatively converted to the metastable LIESST state at 10 K; its lattice parameters were measured up to 50 K, at which point the LIESST state begins to decay on a minute timescale. The change of the lattice parameters can be interpreted by a superposition of a normal temperature dependence, for which the isostructural zinc compound served as a reference, and an almost temperature-independent part which is proportional to the fraction of molecules in the HS state.

Kristallstruktur, Infrarot- und Ramanspektren sowie thermische Zersetzung von Magnesiumtetrahydrogendimesoperiodat, MgH4I2O10 · 6H2O

Crystal structure, DRIFT, infrared and Raman spectra, and the results of thermal analyses of the hitherto wrongly as Mg(H4IO6)2 · 4H20 and Mg(IO4) · 8H2O described dimesoperiodate MgH4I2O10 · 6H2O and of the isostructural zinc compound are presented. The compounds crystallize in the monoclinic space group P21 (Z = 2) with a = 1071.0(2), b = 547.0(1), c = 1194.9(2) pm, and β = 112.58(3)° and a = 1073.3(3), b = 545.3(2), c = 1188.3(5) pm, and β = 112.52(3)°, respectively. The structure, which was refined from X-ray single crystal data of the magnesium compound (R1 = 2.72%, 3824 independet reflections), is built up from isolated distorted M(H2O)6 2+ octahedra and dimesoperiodate ions H4I2O10 2- connected by a network of hydrogen bonds formed by the H4I2O10 2- ions and six crystallographically different hydrate H2O molecules. The strength of the hydrogen bonds ranges from unusually weak bonds corresponding to uncoupled (isotopically dilute samples) OD stretching modes of > 2600cm-1 and very strong ones (νOD: < 2200 cm-1). The IO stretching modes of the transconfigurated H4I2O10 2- ions are assigned to terminal I-O groups (816 cm-1), I-OH groups (746 and 762cm-1) and bridging I-O groups (618 and 647cm-1). On heating, MgH4I2O10 · 6H2O undergoes dehydration in the range of 373 - 485 K (Differential Scanning Calorimetry) to two different polymorphs of magnesium metaperiodate (H4I2O10 2-→2IO4 - + 2H2O). Anhydrous Mg(IO4)2 is instable. Above 423 K (high-temperature Raman data), it decomposes to magnesium iodates.

The crystal structures of Rb 2MgH 4 and Rb 3MgH 5 by neutron powder diffraction

The title compounds and corresponding deuterides were prepared by sintering stoichiometric mixtures of RbH and MgH 2 under a hydrogen (deuterium) pressure of 80 bar at 650 K. Neutron powder diffraction on the deuterides indicate that Rb 2MgH 4 adopts the β–K 2SO 4 structure type (space group Pnma, Z=4), while Rb 3MgH 5 crystallises with the Cs 3CoCl 5 structure type (space group I4/ mcm, Z=4). In both compounds magnesium is tetrahedrally co-ordinated by hydrogen with Mg–D bond distances in the range 1.79–1.87 Å and D–Mg–D bond angles in the range 104.7–114.9°. The cell dimensions and metal hydrogen tetrahedra are significantly bigger than those in the isostructural zinc analogues, thus underlining the difficulty of defining a consistent set of ionic radii (or partial atomic volumes) for metal hydride structures.

The cooperative spin transition in [FexZn1 − x(ptz)6](BF4)2: II. Structural properties and calculation of the elastic interaction

The cooperativity of the thermal spin transition in the Fe(II) spincrossover compound [Fe(ptz)6](BF4)2 (ptz = 1-propyltetrazole) and in isomorphous mixed crystals with the isostructural zinc complex is investigated. From powder X-ray measurements the lattice deformation (tensor e) accompanying the spin transition is determined. For diluted mixed crystals with x 0.44 a first order crystallographic phase transition (R3i → P1i) is observed on cooling, which is triggered by the spin transition and can be suppressed by cooling rapidly. The thermal spin transition is measured with UV/VIS optical absorption spectroscopy on mixed single crystals in the R3i structure. From this metal dilution experiment an interaction constant of 169 cm − 1 for the cooperativity of the spin transition is determined. Furtheron, this interaction constant is calculated on the grounds of elasticity theory: The lattice deformation due to the spin transition is traced back to anisotropic elastic point defects, which directly interact with each other via their stress fields and indirectly via the surface of the elastic crystal by an image pressure. The elastic properties of the crystalline matrix are taken in the isotropic approximation. They are derived from the complete sets of anisotropic elastic constants of the pure iron and zinc compounds, which have been measured previously by Brillouin spectroscopy. The contribution of elastic energy calculated this way is ≃ 80% of the experimental value of the interaction constant, i.e. the cooperativity in crystalline spincrossover compounds is quantitatively of elastic nature.

ChemInform Abstract: The First Determination of the Energy Difference Between Solid‐State Conformers by X‐Ray Diffraction: 1. The Crystal Structure of the Pseudo‐Jahn‐Teller Complex (Nitrito)bis(2,2′‐bipyridyl)copper(II) Nitrate at 20, 100, 165, and 296 K and of Its Isostructural Zinc(II) Analogue at 295 K. 2. The Possibility of Using X‐Ray Diffraction to Characterize Adiabatic Potential Energy Surfaces and Relative Ligand Strengths.

AbstractBoth title complexes crystallize in the space group P21/n with Z=4.

The first determination of the energy difference between solid-state conformers by x-ray diffraction. 1. The crystal structure of the pseudo-Jahn-Teller complex (nitrito)bis(2,2'-bipyridyl)copper(II) nitrate at 20, 100, 165 and 296 K and of its isostructural zinc(II) analog at 295 K. 2. The possibility of using x-ray diffraction to characterize adiabatic potential energy surfaces and relative ligand strengths

Les complexes de Cu et de Zn cristallisent dans le systeme monoclinique, groupe d'espace P2 1/n

Bimetallic compounds of trans-cyclohexane-1,2-diamine-NNN′N′-tetra-acetate(cdta): structural and magnetic characterization of [(H2O)4Cu(cdta)Ni]·3H2O and [(H2O)5Ni(cdta)Cu]·H2O

The crystal structure of the complex [(H2O)4Cu(cdta)Ni]·3H2O (1)(cdta =trans-cyclohexane-1,2-diamine-NNN′N′-tetra-acetate) has been determined by X-ray methods. It crystallizes in the triclinic space group P with Z= 2 in a cell of dimensions a= 8.685(4), b= 11.415(6), c= 12.841(4)Aα= 96.43(4), β= 96.60(3), γ= 102.23(6)°. Least-squares refinement of 2 368 reflections [I > 2.5σ(I)] and 316 parameters gave a final R= 0.036. The molecular structure consists of heterobimetallic units in which the CuII ion occupies a ‘hydrated’ octahedral site and the NiII ion a ‘chelated’ one. The two metal ions are linked through a bridging oxygen belonging to a carboxylate group. The molecular structure of [(H2O)5Ni(cdta)Cu]·H2O (2) is described, based on that determined previously for the isostructural zinc–copper compound. Magnetic properties of these compounds are analyzed in terms of isolated (CuII, NiII) ion pairs. Whereas there is no exchange coupling detected down to 4 K for the nickel–copper compound (2), an antiferromagnetic coupling (J=–30.6 cm–1) is found for the copper–nickel one, (1). This difference is discussed based on comparison of the structural features of the bridging network and co-ordination sites.

Structure determinations of the low-temperature phases of the copper pyridine N-oxide complexes, Cu(C5H5NO)6X2 by neutron diffraction and EPR: influence of solvent and anion on the nature of the cooperative Jahn-Teller coupling

The hexakis(pyridine N-oxide)copper fluoborate and perchlorate complexes have been examined by single-crystal neutron diffraction, electron paramagnetic resonance, and magnetic susceptibility measurements, in order to elucidate the nature of the cooperative Jahn-Teller effect (CJTE) exhibited by these salts and its dependence on the nature of the anion and the solvent used for crystal growing. Neutron diffraction studies between 298 and 20 K on crystals of the fluoborate salt and of the perchlorate salt grown from acetonitrile solution confirm the loss of the high-temperature 3 symmetry of the crystals and the formation of three domains associated with static Jahn-Teller-distorted structures at temperatures of ca. 60 K, as was earlier indicated by EPR results. The structure has been refined with use of 1938 neutron reflection intensities ((sin theta)/lambda less than or equal to 0.79 A/sup -1/) recorded at 20 K, the final R(F/sup 2/) and R/sub w/(F/sup 2/) values being 0.041 and 0.047, respectively. The analysis indicates that DMF molecules are incorporated statistically into the complex, to the extent of approximately 1 molecule to 40 pyridine N-oxide molecules. The DMF molecules occupy tetragonal distortion sites about the copper, with Cu-O distances of 2.67 A, and the presence of these tetragonally distorted complexes inmore » samples grown from DMF solution explains the appearance of the static sites in the earlier reported room-temperature EPR spectra of doped crystals containing Cu(C/sub 5/H/sub 5/NO/sub 6//sup 2 +/. Single crystals and powders of mixed salts with varying ClO/sub 4//sup -//BF/sub 4//sup -/ ratios and heavily doped single crystals of the isostructural zinc complexes have been examined by EPR techniques to assess the relative stabilities of the low-temperature ferrodistortive and antiferrodistortive forms characteristic respectively of the BF/sub 4//sup -/ and ClO/sub 4//sup -/ salts. 9 figures, 5 tables.« less

Magnetic properties of CsCl-type rare-earth cadmium compounds

The magnetic and crystallographic properties of rare-earth cadmium compounds of equiatomic composition were studied. All compounds were found to be ferromagnetic. Indications were obtained that the CsCl structure type is not stable at all temperatures. The magnetic properties of the rare-earth cadmium compounds are compared with the isostructural zinc and magnesium compounds. It is suggested that, apart from the RKKY interaction involving s -conduction electrons, there exists a second coupling mechanism which in some cases even predominates.