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

Abstract

A series of conducting mixed-metallic coordination polymers: Cu2Pb(SCN)4, CuPb(SeCN)4, CuII0.50CuIPb (SCN·SeCN)2, CuAg(SCN)2, CuAg(SeCN)2 and CuAg(SCN·SeCN) have been synthesized by the reaction of Cu and PbII or AgInitrates with KSCN or KSeCN, or both KSCN and KSeCN in H2O. Of significance are the aerobic reactions which yield heterometallic complexes viaoxidation 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 CuII0.50CuIPb(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(C≡N) vibrations in 2162–2087cm−1 and far i.r. bands (500–100cm−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, 10−9to 10−7Scm−1 with activation energies, Ea=0.19–0.25eV and increase in the conductivity with increase in temperature in the 305–423K, range and decrease in conductivity with decrease in temperature in the 295–200K range, show their semiconductor properties.