Electrical properties of complex bimetallic salts [M(N-N)(3)](2+) [Cu(MNT)(2)](2-) and heterobimetallic Ag-I-Cu-II/Hg-II-Cu-II bis(maleonitriledithiolato) bridged coordination polymers

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=F e(II), Co(II), Ni(II), or Cd(II); N-N=1,10-phenanthroline (phen) or ethylen ediamine (en); MNT2-= maleonitriledithiolate) and bridged heterobimetallic complexes Ag-2[Cu(MNT)(2)] and Hg[Cu(MNT)(2)] that have been prepared by tr eatment of complex salt Na-2[Cu(MNT)(2)] (generated in situ) with one equiv alent of cationic complexes [M(N-N)(3)]X-2 or Hg(CH3COO)(2) and two-equival ent of AgNO3 in aqueous-methanol mixture and characterised by relevant spec troscopies (IR, EPR, UV-Visible) as well as by powder XRD spectra. Solution conductivity measurements in 10(-3) M DMSO solution revealed 1:1 electroly tic behaviour of the bimetallic salts. Diamagnetism together with powder EP R spectra for Ag-2[Cu(MNT)(2)] and Hg[Cu(MNT)(2)] show strong antiferromagn etic interaction between two adjacent copper(II) centers at room temperatur e. Majority of the complexes exhibited compressed pellet sigma(rt) in 8.19x 10(-11) to 5.37x10(-7) S cm(-1) range and show semiconductivity over the 30 3-383 K temperature range. Conductivity of both coordination polymers are a ppreciably higher compared to the bimetallic salts. For the salts [Co(phen) (3)] [Cu(MNT)(2)], [Ni(phen)(3)][Cu(MNT)(2)] and bridged complexes Ag-2[Cu( MNT)(2)] and Hg[Cu(MNT)(2)] the conductivity remarkably increases, i.e., 10 (2) to 10(3) order of magnitude at elevated temperature showing some sort o f phase transformation producing S ... S intermolecular contact. (C) 2000 E lsevier Science Ltd. All rights reserved.