Multicoloured Thiophene Based AIEgens: Single Crystal Structure Elucidation, Spectral Behaviour and DFT Studies

Abstract

A series of Schiff base thiophene derivatives, D1 to D9, which exhibits a phenomenon of aggregation‐induced emission enhancement (AIEE) have been synthesised and characterized by standard spectroscopic techniques. Multicoloured emission enhancement has been achieved just by introduction of electron donating and withdrawing substituent on the thiophene moiety. Few of the molecules in the series exhibited enhanced fluorescence emission intensity in solvent mixture in comparison with that observed in pure solvent supportive of AIE. Single crystal x‐ray diffraction (SCXRD) studies on selected molecules, D6 and D7 of the series revealed the existence of planar structure and a herringbone type of crystal packing arrangement. In specific, molecules D6 and D7, possesses a larger π‐π stacking distance of around 4.866 Å and 4.636 Å, which curbs all the non‐radiative pathways, in turn leading to AIEE. DFT and TDDFT calculations confirm the structural planarity supportive of SCXRD analysis and the nature of electronic transition correlating well with the experimental results.

Theoretical Insights into Aggregation-Induced Emission with the Ionic π Fluorophore: The Importance of Choosing the Dimer QM Model in the ONIOM Study

“…So far, Trivedi et al have proven that the unfavorable π−π stacking can be prevented by increasing the distance between interacting π systems in the crystal. 20 Recently, it has been experimentally found that both anions and cations can form a noncovalent interaction with the π system to replace the unfavorable π−π interaction. 21,22 The pyridine cation−π interaction was used to generate luminescence responses in solution as early as 2011.…”

“…It is well known that the unfavorable π–π interaction in the solid state makes the organic luminescent systems in the excited state undergo a decay in energy, which leads to a decrease in the luminescence efficiency. , Obviously, the search for an alternative intermolecular interaction that can avoid harmful intermolecular π–π interactions will facilitate one to design AIE systems with excellent luminescence properties. So far, Trivedi et al have proven that the unfavorable π–π stacking can be prevented by increasing the distance between interacting π systems in the crystal . Recently, it has been experimentally found that both anions and cations can form a noncovalent interaction with the π system to replace the unfavorable π–π interaction. , The pyridine cation−π interaction was used to generate luminescence responses in solution as early as 2011 .…”