Computational investigation of the perylene-TCNQ complex: effects of chalcogen and fluorine substitutions

Donor-acceptor (D-A) complexes, formed between two or more molecules held together by intermolecular forces, show interesting tunable properties and found applications in diverse fields, including semiconductors, catalysis, and sensors. In this study, we investigated the D-A complexes formed between perylene and 7,7,8,8-tetracyanoquinodimethane (TCNQ) and their chalcogen (S, Se) and fluorine derivatives. It was observed that interaction energies due to complex formation increase while the HOMO-LUMO gaps decrease with chalcogen substitutions. A redshift in the electronic absorption spectra of the complexes was observed with chalcogen substitutions. The substitution of fluorine further enhanced these changes without altering the trend. These changes were found to be more for substitution with selenium compared to that of sulfur.

The ωB97X-D/6-311+G(2df,p) level of theory was used to optimize the individual geometries, complexes, and for the frequency calculation. Atoms-in-molecule and reduced density gradient analyses were employed for the interaction study. Time-dependent density functional theory with the same level was used to analyze the electronic excitation for complexes.