SYNTHESIS AND ELECTRICAL PROPERTIES OF SOME NEW HETEROBIMETALLIC COORDINATION POLYMERS MPb(SCN)₄ (M = Co, Ni) AND THEIR REACTION PRODUCTS WITH LEWIS BASES

Abstract

This paper describes a study of the electrical conducting behaviour of some new heterobimetallics of the composition MPb(SCN)₄ (M = Co(II), Ni(II)) and their Lewis base products of the forms MPb(SCN)₄L₂ (L = pyridine (py) or triphenylphosphine (PPh₃)) and [M(phen)₃][Pb(SCN)₄] (M = Co(II) or Ni(II); phen = 1,10-phenanthroline). The properties of these were investigated by using spectroscopic (IR, UV-Visible) methods as well as powder XRD and conductivity techniques. The IR spectra showed the bridging nature of SCN⁻ in MPb(SCN)₄ and MPb(SCN)₄(py)₂, both terminal and bridging SCN⁻ in NiPb(SCN)₄(PPh₃)₂ and only terminal SCN⁻ groups in [M(phen)₃][Pb(SCN)₄]. The magnetic data and electronic absorptions are also compatible with these proposed arrangements. Based on these studies, polymeric, monomeric and ionic structures have been proposed for these compounds. All of the compounds exhibited solid state σ_rt values in the 10⁻¹² to 10⁻⁶ S cm⁻¹ range, and all showed semiconductivity from 303 to 363 K. A notable increase in conductivity, 10²–10³ increase, at higher temperatures suggested some type of phase transition/packing equilibrium changes which produce effective M…S/Pb…S/S…S intermolecular interactions in NiPb(SCN)₄ and [M(phen)₃][Pb(SCN)₄].

ACKNOWLEDGMENT

One of the authors, Vinay Kumar Singh, acknowledges Banaras Hindu University for financial assistance in the form of a scholarship.