Study of charge transfer interaction modes in the mixed Donor-Acceptor cocrystals of pyrene derivatives and TCNQ: A combined structural, thermal, spectroscopic, and hirshfeld surfaces analysis

Abstract The role of charge-transfer (CT) interactions in the synthesis of charge-transfer (CT) complexes is of great significance, which has led to promising materials for a range of applications. Herein, we report the synthesis of three new binary mixed stack CT systems I , II , and III , grown by solvent evaporation technique involving, 1-(naphthalene-2-yl)− 3-(pyrene-1-yl)prop-2-en-1-one ( NPPO ), 3-(pyrene-1-yl)− 1-(thiophene-2-yl)prop-2-en-1-one ( PTPO ) and 2-phenyl-3-(pyrene-2-yl)acrylonitrile ( PPA ) as the donors and 7,7,8,8-tetracyanoquinodimethane (TCNQ) as an acceptor material. X-ray diffraction, thermal behavior, and spectroscopic analysis affirm the formation of CT complex and material purity. Based on the structural analysis the three CT complexes exhibit mixed stack arrangement (DAD--DAD) directed by the CT π–π interactions while the auxiliary hydrogen bonds (C-H--O, and C-H--N) stabilize and contribute to the overall packing of CT complexes. Remarkably, the complexes exhibit strong CT absorptions spreading to near infrared, making the crystals appear black. Not to mention, Hirshfeld surface analysis was employed to study the different intermolecular interactions and crystal packing in these materials. These results indicate that such a cocrystal design helps to explore new D-A systems, particularly with a mixed stack, that might have potential research values for applications in materials science.