Crystallographic and quantum-chemical analysis of parallel interaction in tetrathiafulvalene dimer

In this work, interactions between two parallel unsubstituted TTF molecules were investigated using statistical analysis of data obtained by searching the Cambridge Structural DataBase (CSD) and DFT-D3 calculations. Results of analysis of contacts found in the CSD show that TTF molecules in crystal structures tend towards the formation of parallel interactions. In most of the contacts molecules have slipped geometry along the long C2 axis of the one molecule with the offset value of 1.5 to 2.0 A. In order to estimate interaction energies between two neutral molecules, as well as optimal values of offsets and normal distances at which they occur, we performed quantum chemical calculations at B2PLYP-D3/6-311-H-G** and M06L-D3/6-311.G** levels of theory. The calculations are in good agreement with crystallographic data. The most stable interaction corresponds to the most frequent geometry which is found by searching CSD and has the energy value of -9.27 kcal/mol