Neutron diffraction and 35Cl-NQR-T 1 measurements of N-[2,6-dichlorophenyl]-2,2,2-trichloroacetamide, 2,6-Cl2C6H3NHCOCCl3 1

Abstract

Abstract N-[2,6-dichlorophenyl]-2,2,2-trichloroacetamide (2,6-Cl2C6H3NHCOCCl3) shows a bleaching out of certain 35Cl-NQR frequencies at a temperature of 159 K. The 35Cl-NQR spin lattice relaxation time (T 1) was determined as function of temperature. The data of the trichloromethyl resonances lead to an activation energy of 23.7 kJ/mole for the bleaching out process. The chlorine atoms bonded to the phenyl ring show a normal temperature dependence of T 1. In addition crystal structure determinations were made at three temperatures using neutron diffraction (117 K, 195 K, 373 K). The space group of the compound is P21/c = C[unk]h with four molecules per unit cell. The cell parameters are a = 1007(1) pm, b = 1168(1) pm, c = 1002(1) pm, β = 101.79(7)° (117 K), a = 1017(3) pm, b = 1194(3) pm, c = 1007(3) pm, β = 101.9(2)° (295 K), a = 1018.5(9) pm, b = 1208(1) pm, c = 1009(1) pm, β = 101.63(8)° (373 K). The molecules form intermolecular hydrogen bonds of the N–H…O–C type along [001]. An anharmonic behaviour of two of the trichloromethyl chlorine atoms was observed and studied as a function of temperature. The intramolecular distances and angles show no significant temperature variations.