Non-covalent interactions in small thiophene clusters

Theoretical understanding of the thiophene solvent is subjected to the knowledge of the structures and the interactions taking place in thiophene clusters. Despite the importance of the thiophene clusters in understanding the thiophene solvent, there are not many reported studies on thiophene clusters. In this work, we have performed quantum chemical computations to understand the nature and number of non-covalent interactions that stabilize the structures of the thiophene clusters. For this purpose, we have started by exploring the potential energy surfaces (PESs) of the thiophene dimer, trimer, and tetramer, using classical molecular dynamics in order to generate initial guessed structures. These generated structures were then optimized at the MP2/aug-cc-pVDZ level of theory. As a result, it is found that the thiophene dimer prefers the sandwich/stacking configuration over the T-shaped configuration while for the thiophene trimer, only the cyclic configuration has been located. After locating the stable structures of the thiophene dimer, trimer and tetramer, we have performed a quantum theory of atoms in molecules (QTAIM) analysis on the investigated structures. The results show that six different non-covalent interactions have been identified in thiophene clusters: C center dot center dot center dot C (or pi center dot center dot center dot pi) bonding, CH center dot center dot center dot C (or CH center dot center dot center dot pi) hydrogen bonding, CH center dot center dot center dot S hydrogen bonding, C center dot center dot center dot S (or pi center dot center dot center dot S) bonding, S center dot center dot center dot S bonding and H center dot center dot center dot H bonding interactions. In addition, we have assessed the performance of eleven functionals of the density functional theory (DFT) in calculating the binding energies of the thiophene clusters. It is found that the functionals M052X and M06 showed the best performance with DLPNO-CCSD(T)/CBS used as reference. (C) 2021 Elsevier B.V. All rights reserved.