New heterometallic coordination polymers derived form chalcogenocyanates: Synthesis, characterization and electrical properties

Abstract

A series of conducting mixed-metallic coordination polymers: Cu 2Pb(SCN)4, CuPb(SeCN)4, Cu0.50 IICuIPb (SCN - SeCN)2, CuAg(SCN)2, CuAg(SeCN)2 and CuAg(SCN - SeCN) have been synthesized by the reaction of CuII and PbIII or AgI nitrates with KSCN or KSeCN, or both KSCN and KSeCN in H 2O. Of significance are the aerobic reactions which yield heterometallic complexes via oxidation of SCN- and SeCN- into (SCN)2 and (SeCN)2 followed by quantitative reduction of CuII into CuI; in the case of CuPb(SeCN)4 reduction of CuII into CuI is not observed, while in Cu0.50IICuIPb(SCN · SeCN)2, CuII is partially reduced to CuI. These compounds have been characterized by elemental (C, N, S and Se) analyses, magnetic moment measurements, relevant spectroscopies (i.r., far i.r., Raman, u.v.-vis. and e.p.r.), powder X-ray diffraction pattern and conductivity technique. The v(CΞN) vibrations in 2162-2087 cm-1 and far i.r. bands (500-100 cm-1) corroborated by Raman bands are conclusive of the bridging (N, S/Se) mode and metal-NCS and metal-SCN/SeCN- bonding respectively in the complexes. Room temperature magnetic moment, electronic absorption spectra and e.p.r. active/silent nature confirm the oxidation state of copper in these solids. Room temperature compressed pellet conductivities σrt, 10-9 to 10-7 S cm-1 with activation energies, Ea = 0.19-0.25 eV and increase in the conductivity with increase in temperature in the 305-423 K, range and decrease in conductivity with decrease in temperature in the 295-200 K range, show their semiconductor properties.