Synthesis, crystal structure, high-resolution 113Cd and 13C MAS NMR investigation and dielectric study of [C2H10N2]Cd (SCN)4

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 C-13 and Cd-113 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 pi-pi interactions. Solid state Cd-113 CP/MAS NMR shows that each distinct cadmium site in the cadmium thiocyanates exhibits multiplets that result from Cd-113, N-14 spin-spin coupling. Examination of the C-13 CP/MAS NMR line shapes allows direct measurement of the indirect spin-spin coupling constants (1)J(N-14, C-13) = 28 Hz and (2)J((111/113)cd, C-13) = (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 sigma((RP)) and relaxation frequency (f(r)) 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. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

A new crystalline polymer compound was synthesized and analyzed with various techniques, revealing unique structural and bonding characteristics. The compound exhibited phase transitions, temperature-dependent conductivity, and frequency-dependent AC conductivity following specific dynamic laws. Quantum mechanical tunneling mechanism was suggested to prevail in certain phases based on the temperature evolution of certain properties.