Preparation, characterization and electrical conductances of heterometallic coordination polymers and complex bimetallic salts derived from isomaleonitriledithiolate

The complex salts [M(N-N)3][Cu(i-mnt)2] [M = Fe(II), Co(II), Ni(II) or Cd(II); N-N = 1,10-phenanthroline (phen) or ethylenediamine (en); i-mnt2− = isomaleonitriledithiolate] and heterometallic coordination polymers M′Cu(i-mnt)2 [M′=2Ag(I), Cd(II), Hg(II) or Pb(II)] have been synthesized by stoichiometric reactions between K2[Cu(i-mnt)2] and [M(N-N)3]X2 or MX2 [X=Cl−, NO3− or 1/2SO42−]. These have been characterized by elemental analyses, solution conductivity and magnetic susceptibility measurements, relevant spectroscopies (IR, UV–Visible and EPR) and solid phase conductivity techniques. Complete quenching of paramagnetism shows strong antiferromagnetically coupled Cu(II) ions in the bridged heterometallic complexes M′Cu(i-mnt)2 producing a polymeric array. The coordination polymers M′Cu(i-mnt)2 exhibit σrt=10−9–10−6 S cm−1 and show semiconductivity in the 313–393 K range while complex salts [M(N-N)3][Cu(i-mnt)2] are insulators at room temperature and at higher temperature as well. Iodine-doped products of complex bimetallic salts and coordination polymers are conducting at room temperature and exhibit semiconducting behaviour over above temperature range. Conductivities of the coordination polymers are significantly higher compared to the bimetallic salts.