Synthesis, photophysical behavior in solution, aggregates, solid state and computational study of new derivatives of 2,2'-bis(indolyl)methane-triphenylamine

A series of new 2,2'-bis(indolyl)methane-triphenylamine (2,2'-BIM-TPA) derivatives were synthesized and characterized. TPA units were inserted in the indole fragment, as well as in the methylene position of the BIM to obtain systems with a high degree of torsion and intramolecular rotation. Phenyl and phenylethynyl linkers between TPA and BIM units were included in the BIM-Ph-TPA and BIM-Ph-E-TPA derivatives to extend the conjugation of the methylene substituted BIMs. The absorption and emission behavior in solution, aggregates and solid state of five 2,2'-BIM-TPA derivatives was studied. Only BIM-Ph-TPA and BIM-Ph-E-TPA showed a slight solvatochromic behavior. In THF-water mixtures, non-emissive aggregates were produced, but the concentrated solutions (10 0 0 mu M) of each compound favored the for-mation of emissive aggregates. It was found that water acts as a fluorescence quencher of the aggregates. Additionally, the 2,2'-BIM-TPA derivatives showed fluorescence in the solid state. The DFT computational studies allowed to confirm the highly twisted molecular geometries, to elucidate the distribution and energy of the frontier molecular orbitals (HOMO-LUMO), as well as the nature of the main electronic transitions (UV-Vis).(C) 2022 Elsevier B.V. All rights reserved.

Automated summary

A series of new 2,2'-bis(indolyl)methane-triphenylamine derivatives were synthesized and characterized. These derivatives showed high torsion and intramolecular rotation due to the incorporation of TPA units in the indole fragment and the methylene position of the BIM. Some of the derivatives exhibited solvatochromic behavior and fluorescence in the solid state.