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

Abstract

A series of conducting mixed-metallic coordination polymers: Cu 2 Pb(SCN) 4 , CuPb(SeCN) 4 , Cu II 0:50 Cu I Pb (SCN AE SeCN) 2 , CuAg(SCN) 2 , CuAg(SeCN) 2 and CuAg(SCN AE SeCN) have been synthesized by the reaction of Cu II and Pb II or Ag I nitrates with KSCN or KSeCN, or both KSCN and KSeCN in H 2 O. 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 Cu II into Cu I ; in the case of CuPb(SeCN) 4 reduction of Cu II into Cu I is not observed, while in Cu II 0:50 Cu I Pb(SCN AE SeCN) 2 , Cu II is partially reduced to Cu I . 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(CBN) 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 r rt , 10 )9 to 10 )7 S cm )1 with activation energies, E a ¼ 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.

Towards the chemical control of molecular packing: syntheses and crystal structures of threetrans-[NiL4(NCS)2] complexes

“…Nickel(II) thiocyanate complexes with N-donor ligands are of interest for several, often related, reasons. Noteworthy are their ability to occur in cis and trans isomeric forms (Ðaković et al, 2011), the existence of coordination polymers in which thiocyanate is a linear bridging ligand (Quan et al, 2009) and their potential for development as optical, porous, electrical, magnetic or conductive materials (Fafarman et al, 2011;Zhang et al, 1999;Soldatov et al, 2004;Sinha & Singh, 2004). Particularly relevant to the present work is that nickel(II) thiocyanate complexes have the details of their crystal architectures controlled by relatively weak forces such as hydrogen bonding (Ðaković et al, 2008) orstacking interactions.…”