Structural, magnetic, high-frequency and high-field EPR investigation of double-stranded heterometallic [{Ni(en)2}2(micro-NCS)4Cd(NCS)2](n).nCH3CN polymer self-assembled from cadmium oxide, nickel thiocyanate and ethylenediamine

Dalton Trans. 2008 Mar 21:(11):1431-6. doi: 10.1039/b713252b. Epub 2008 Jan 22.

Abstract

A novel heterometallic 1D coordination polymer [{Ni(en)2}2(micro-NCS)4Cd(NCS)2](n) x nCH3CN (en = ethylenediamine) has been prepared using the self-assembly process in a one-pot reaction of cadmium oxide, nickel and ammonium thiocyanates with an acetonitrile solution of ethylenediamine. The complex consists of an uncommon cis-Cd(SCN)4(NCS)2(4-) fragment and a rare combination of cis-Ni(en)2(2+) and trans-Ni(en)2(2+) building blocks linked by micro(1,3)-NCS bridges into a double-stranded zigzag chain structure. Each chain is comprised of [Ni2Cd2(micro-NCS-N,S)4)] macrocycles with chair-like and rectangular-like shapes arrayed alternately. The shortest intrachain CdCd separations are 9.535(1) and 10.868(2) A, while the nearest NiNi distances are 5.418(1) and 6.612(2) A. A network of weak N-HS hydrogen bonds, involving the terminal NCS ligands and NH2-groups of en, links the infinite chains and results in the formation of an extended supramolecular three-dimensional framework. Variable-temperature (1.8-300 K) magnetic susceptibilities show a slight change of the micro(B) value at low temperature, indicative of weak antiferromagnetic interactions (J = 1.55 cm-1) between magnetic canters. High-field, high-frequency (100-400 GHz) EPR spectra were simulated using S = 1 ground state for separate Ni2+ ions with the spin Hamiltonian parameters g = 2.165, D = 0.45 cm-1 and E = 0.03 cm(-1). According to DFT calculations, the D and E parameters are -0.35 cm(-1) and 0.049 cm-1 for the cis arrangement of Ni2+ and 0.58 cm(-1) and 0.012 cm(-1) for trans.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Cadmium Compounds / chemistry*
  • Crystallography, X-Ray
  • Electron Spin Resonance Spectroscopy
  • Ethylenediamines / chemistry*
  • Hydrogen Bonding
  • Isomerism
  • Magnetics
  • Models, Molecular
  • Molecular Conformation
  • Oxides / chemistry*
  • Polymers / chemical synthesis
  • Polymers / chemistry*
  • Spectrophotometry, Infrared
  • Thiocyanates / chemistry*

Substances

  • Cadmium Compounds
  • Ethylenediamines
  • Oxides
  • Polymers
  • Thiocyanates
  • nickel thiocyanate
  • cadmium oxide
  • ethylenediamine