Browsing by Author "Rohit Kumar Sinha"

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New heterometallic coordination polymers derived form chalcogenocyanates: Synthesis, characterization and electrical properties
(2004) Nanhai Singh; Rohit Kumar Sinha
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.
Preparation, characterization and electrical conductances of heterometallic coordination polymers and complex bimetallic salts derived from isomaleonitriledithiolate
(Elsevier, 2003) Nanhai Singh; Sunita Gupta; Rohit Kumar Sinha
The complex salts [M(N-N)3][Cu(i-mnt)2] [M = Fe(II), Co(II), Ni(II) or Cd(II); N-N = 1,10-phenanthroline (phen) or ethylenediamine (en); i-mnt2- = isomaleonitriledithiolate] and heterometallic coordination polymers M′Cu(i-mnt)2 [M′ = 2Ag(I), Cd(II), Hg(II) or Pb(II)] have been synthesized by stoichiometric reactions between K2[Cu(i-mnt)2] and [M(N-N)3]X2 or MX2 [X = C?-, NO3- or 1/2SO42-]. These have been characterized by elemental analyses, solution conductivity and magnetic susceptibility measurements, relevant spectroscopies (IR, UV-Visible and EPR) and solid phase conductivity techniques. Complete quenching of paramagnetism shows strong antiferromagnetically coupled Cu(II) ions in the bridged heterometallic complexes M′Cu(i-mnt)2 producing a polymeric array. The coordination polymers M′Cu(i-mnt)2 exhibit σrt = 10-9-10-6 S cm-1 and show semiconductivity in the 313-393 K range while complex salts [M(N-N)3][Cu(i-mnt)2] are insulators at room temperature and at higher temperature as well. Iodine-doped products of complex bimetallic salts and coordination polymers are conducting at room temperature and exhibit semiconducting behaviour over above temperature range. Conductivities of the coordination polymers are significantly higher compared to the bimetallic salts. © 2003 Elsevier Science B.V. All rights reserved.
Preparation, characterization and electrical conductivity of heterometallic complexes derived from 2-sulfanylbenzothiazolate
(2001) Nanhai Singh; Rohit Kumar Sinha
A complex salt (NMe4)2[Hg(C7H4NS2) 4] and eight heterometallics MM′(C7H4NS2)4[M = Co(II), Ni(II), Zn(II), 2Cu(I) or 2Ag(I); M′ = Zn(II) or Hg(II)] have been synthesized and characterized by elemental analyses, molar conductance and magnetic susceptibility measurements, relevant spectroscopy [IR, electronic, EPR, 1H and 13C NMR] and ES+ mass spectrometry. In general, their σrt ∼ 10-13 S cm-1 is low, however NiHg(C7H4NS2)4, CoZn(C7H4NS2)4 and Ag2Hg(C7H4NS2)4 show semiconductivity in the 303-523 K range. © 2001 Elsevier Science B.V. All rights reserved.
Preparation, characterization and molecular electrical conductivity of an ion-pair complex and mixed-metallic coordination polymers derived from maleonitriledithiolate
(2003) Nanhai Singh; Rohit Kumar Sinha
An ion-pair complex [Cd(en)3]22+ [Ag4(mnt)4]4- and three mixed metallic coordination polymers MNi(mnt)2 [M = Pd(II), 2Ag(I) or Hg(II); mnt2- = maleonitriledithiolate] have been prepared and characterized using IR, UV-Visible and conductivity techniques. All of the complexes exhibit pressed pellet σrt ≃ 10-5 S cm-1 and show electrical behaviour of semiconductors over 303-393 K range. © 2002 Elsevier Science B.V. All rights reserved.
Synthesis, characterization and conducting properties of complex salts and heterobimetallic coordination polymers of the cyanodithioimidocarbonato ligand
(2006) Nanhai Singh; Akhilesh Prasad; Rohit Kumar Sinha
The complex salts (NPr4n)2 [M′ (cdc)2] and the heterobimetallic coordination polymers [MM′(cdc)2] [M = Zn(II), Cd(II), Hg(II), 2Ag(I) or Pb(II); M′ = Ni(II) or Cu(II); cdc2- = cyanodithioimidocarbonate] have been prepared and characterized by elemental analysis, solution and solid state conductivity, magnetic susceptibility, IR, 1H and 13C NMR, UV-Vis, EPR and FAB-mass spectrometry. All of the compounds exhibited semiconducting behaviour. © 2006 Elsevier B.V. All rights reserved.
Synthesis, characterization and electrical conductivity of mixed-ligand heterobimetallic coordination polymers
(2002) Nanhai Singh; Rohit Kumar Sinha
A series of mixed-ligand heterobimetallic complexes of the form MM′(C7H4NS2 )4(py)2 and MM′(C7H4NS2)4(N-N) and complex heterobimetallic salts [M(N-N)3][M′ (C7H4NS2)4] [M = Co(II) or Ni(II); M′= Zn(II) or Hg(II); N-N = ethylenediamine(en) or 1,10-phenanthroline(phen)] has been prepared and characterized by IR and UV-visible spectroscopy, microanalysis and conductivity techniques. Except with NiZn(C7H4NS2)4(py)2 which is insulator all of the compounds exhibit σrt in the 10-12-10-5 S cm-1 range and semiconduct over 303-393 K. © 2002 Elsevier Science B.V. All rights reserved.