Molecular and Crystal Structure of 1,2,3-Tribenzylthiobenzene and 1,2-Dibenzylthio-3-Fluorobenzene According to XRD Data and Density Functional Theory Computations
摘要
1,2,3-Tribenzylthiobenzene and 1,2-dibenzylthio-3-fluorobenzene are prepared and characterized by XRD. The crystals of both compounds feature intermolecular C–H⋯π interactions with 2.74-2.78 Å distances to the benzene ring planes. The 1,2-dibenzylthio-3-fluorobenzene crystal also displays inter- and intramolecular C–F⋯π interactions so that the distances to the planes are 3.42 Å and 3.44 Å, respectively. A conformational analysis of free molecules of these compounds was performed by the GOAT/XTB method, and the determined global minima were optimized by the B3LYP/def2-TZVPP method. In the identified minimum-energy conformations, all pairs of benzene rings adopt a gauche orientation with respect to the CH2–S bonds. These “folded” compact conformations differ strongly from those observed in crystals where one benzyl group of each conformation adopts a gauche orientation with respect to the central benzene ring. The energy differences between the conformations observed in crystals and the optimized ones are 60.7 kJ/mol for 1,2,3-tribenzylthiobenzene and 22.6 kJ/mol for 1,2-dibenzylthio-3-fluorobenzene, i.e. several times smaller than the energies of intermolecular interactions in crystals calculated by the same method (222.4 kJ/mol and 170.3 kJ/mol, respectively).