Structural confirmation of the 3,5-dinitrosalicylato anion coordination ability to metal ion: crystal structure, spectral and magnetic properties of the [Cu-3{3,5-(NO2)(2)sal(2-)}(2){3,5-(NO2)(2)sal(1-)}(2)(H2O)(4)]center dot 4H(2)O

摘要

Reaction of copper(II) salts with 3,5-dinitrosalicylic acid yields to the complex formation of the composition [Cu-3{3,5-(NO2)(2)sal(2-)}(2){3,5-(NO2)(2)sal(1-)}(2)(H2O)(4)](.)4H(2)O (3,5-(NO2)(2)sal(x) = 3,5-dinitrosalicylate anion). The complex was characterized, by elemental microanalysis, electronic, IR and EPR spectra and magnetic susceptibility measurements. The crystal structure of the complex has been determined and refined to R = 0.0482, and wR = 0. 1206 for 2980 reflections with I > 2sigma(I) (R = 0.0724, and wR = 0.1283 for all 4124 reflections. The complex crystallizes in monoclinic system, space group P2(1)/c, a = 10.873(2), b = 14.726(3), and c = 13.167(3) Angstrom, beta = 94.11(3)degrees, V = 2102.8(8) Angstrom(3), and Z = 4. Structure of the complex comprises of the centrosymmetric [Cu-3{3,5-(NO2)(2)sal(2-)}(2){3,5-(NO2)(2)sal(1-)}(2)(H2O)(4)] molecules and the water molecules which are held together by system of different types of hydrogen bonds and van der Waals interactions. The Cu(1) atom is centrosymmetrically coordinated by two 3,5-dinitrosalicylato dianions, thus forming the square planar CuO4 chromophore. Each of the satellite Cu(2) atoms are coordinated by one oxygen atom of bridging 3,5-dinitrosalicylato dianion, two oxygen atoms of chelating 3,5-dinitrosalicylato monoamon (in the phenolato form), and by two water oxygen atoms in the square pyramidal coordination polyhedron. Variable-temperature magnetic susceptibility measurements (1.9-300 K) show occurrence of significant ferromagnetic interactions caused by syn-anti conformation of carboxylato bridges within the trimer (J(12) = 4.31, J(13) = 0 cm(-1)). Bellow 3 K, anti ferromagnetic intermolecular interaction between trimeric molecules in the crystal lattice was observed (zJ' = -0.29 cm(-1)). The EPR spectroscopy is in agreement with the molecular structure of the complex and magnetic properties, indicates superposition spectra of copper centres (S = 1/2) with square-planar and square pyramidal coordination polyhedrons (g(parallel to) = 2.32, g(perpendicular to) = 2.05). (C) 2004 Elsevier Ltd. All rights reserved.