Electrical properties of complex bimetallic salts [M(N–N)3]2+[Cu(MNT)2]2− and heterobimetallic AgI–CuII/HgII–CuII bis(maleonitriledithiolato) bridged coordination polymers

Abstract

This paper presents the solid-state electrical conductance properties of a series of complex bimetallic salts of the form [M(N–N)3][Cu(MNT)2] (M=Fe(II), Co(II), Ni(II), or Cd(II); N–N=1,10-phenanthroline (phen) or ethylenediamine (en); MNT2−=maleonitriledithiolate) and bridged heterobimetallic complexes Ag2[Cu(MNT)2] and Hg[Cu(MNT)2] that have been prepared by treatment of complex salt Na2[Cu(MNT)2] (generated in situ) with one equivalent of cationic complexes [M(N–N)3]X2 or Hg(CH3COO)2 and two-equivalent of AgNO3 in aqueous–methanol mixture and characterised by relevant spectroscopies (IR, EPR, UV-Visible) as well as by powder XRD spectra. Solution conductivity measurements in 10−3 M DMSO solution revealed 1:1 electrolytic behaviour of the bimetallic salts. Diamagnetism together with powder EPR spectra for Ag2[Cu(MNT)2] and Hg[Cu(MNT)2] show strong antiferromagnetic interaction between two adjacent copper(II) centers at room temperature. Majority of the complexes exhibited compressed pellet σrt in 8.19×10−11 to 5.37×10−7 S cm−1 range and show semiconductivity over the 303–383 K temperature range. Conductivity of both coordination polymers are appreciably higher compared to the bimetallic salts. For the salts [Co(phen)3][Cu(MNT)2], [Ni(phen)3][Cu(MNT)2] and bridged complexes Ag2[Cu(MNT)2] and Hg[Cu(MNT)2] the conductivity remarkably increases, i.e., 102 to 103 order of magnitude at elevated temperature showing some sort of phase transformation producing S⋯S intermolecular contact.