Synthesis, crystal structure, high-resolution l13Cd and 13C MAS NMR investigation and dielectric study of [C2H10N2]Cd (SCN)4

Abstract A new crystalline polymer compound [C2H10N2]Cd (SCN)4 was synthesized and analyzed using XRD single crystal, differential scanning calorimetry (DSC), thermal gravimetric analysis (TGA), complex impedance and solid state 13C and 113Cd CP/MAS NMR. The crystal structure shows that the cadmium atoms have a S4N2-hexa-coordination sphere, exhibiting pseudo-octahedral geometry. The Cd(II) atoms are bridged by two SCN− anions generating 1D polymeric chains. Crystal packing with significantly different interactions was determined by Hirshfeld surface analysis and discussed herein. The crystal packing was assured by mean of hydrogen bonds, Van der Waals and π-π interactions. Solid state 113Cd CP/MAS NMR shows that each distinct cadmium site in the cadmium thiocyanates exhibits multiplets that result from 113Cd,14N spin-spin coupling. Examination of the 13C CP/MAS NMR line shapes allows direct measurement of the indirect spin-spin coupling constants 1J(14N, 13C) = 28 Hz and 2J(111/113Cd,13C) = (75+8)Hz, for the unique N-bonded thiocyanate ligand. DSC analysis shows a phase transition at about 359 K. The temperature dependence of bulk conductivity σ(Rp) and relaxation frequency (fr) were described and discussed by the use of the Arrhenius relationship. The frequency dependence of the real part of the AC conductivity in both phases follows the Jonscher's universal dynamic law. The evolution of S(T) as function of temperatures suggests that the quantum mechanical tunneling QMT mechanism prevails in phases I and II.