A new low temperature solid modification in 1-isothiocyanato-4-(trans 4-propylcyclohexyl)benzene (3CHBT) probed by Raman spectroscopy and quantum chemical calculations

Raman spectra of 1-isothiocyanato-4-(trans 4-propylcyclohexyl)benzene (3CHBT) were studied in the region, 1450-2300 cm(-1) at twenty two different temperatures in the range, 83-293 K in cooling and heating cycles. All bands in this region were critically evaluated in term of linewidth, peak position and relative intensity. Raman bands at similar to 2085 cm(-1) and similar to 2120 cm(-1) shows clear evidence of a solid modification through anomaly in temperature dependence peak positions and linewidths variation in the temperature range 173-203 K. A detailed analysis of the variation of the linewidth and peak position of the two component bands leads to the conclusion that the molecular/dimer arrangement in crystalline packing changed between 173 K and 203 K. This solid modification was also analyzed at the molecular level. The similar to 2085 cm(-1) and similar to 2120 cm(-1) bands were corresponded as parallel and anti-parallel dimers of 3CHBT, which are identified as dimer I (D-1) and dimer II (D-2), respectively. The structures of both the dimers have been optimized by quantum chemical calculations employing density functional theoretic (DFF) methods. (C) 2017 Elsevier B.V. All rights reserved