Structure, DFT based investigations on vibrational and nonlinear optical behavior of a new guanidinium cobalt thiocyanate complex

This paper reports the crystal growth and structure of a newly synthesized hybrid organic-inorganic compound (CH 6 N 3 ) 2 [Co (NCS) 4 ].H 2 O by means of a joint experimental and theoretical study. Single-crystal X-ray diffraction reveals that this compound crystallizes in the noncentrosymmetric P2 1 2 1 2 space group. The 3D framework of the crystal structure is formed by hydrogen-bonded cations of (CH 6 N 3 ) + , [Co (NCS) 4 ] 2− anions and water molecules. UV-Visible reveals an indirect allowed optical transition with energy gap Eg = 3.41 eV. The optimized molecular structure, harmonic vibrational frequencies, static and frequency-dependent nonlinear optical (NLO) parameters were calculated by density functional theory with and without dispersion corrections. A good consistency for the structure, as well as IR and Raman spectra, is found between the calculated and experimental results. A detailed interpretation of the vibrational modes was carried out and a total assignment was performed on the basis of the potential energy distribution (PED) contribution. Moreover, the inter-ionic interaction energy was evaluated and a decomposition analysis was performed by localized molecular orbital energy decomposition analysis (LMO-EDA) method. The calculated NLO parameters compared to urea as a reference show that the title compound can be a good candidate for NLO applications.