The impact of the molecular structure on aggregation and solid state luminescence of 2,3-diarylfumaronitriles

Abstract This work focuses on the substituent effect in 2,3-diarylfumaronitriles on the optical properties and intermolecular interactions in the solid state. 2,3-Diarylfumaronitriles show various luminescence behaviour in solution and in the solid state. Aggregation patterns of 2,3-diarylfumaronitriles govern their luminescent properties in the solid state. The weak intermolecular interactions N C···N C, C–H···Cl, and C–H···N C were detected in the X-ray structures of 2,3-diarylfumaronitriles and studied by DFT calculations at the M06–2X/6–311++G(d,p) level of theory and topological analysis of the electron density distribution within the framework of QTAIM method. The estimated strength of these non-covalent bonds is 0.8–1.3 kcal/mol. The orientation of molecules in crystals depends on the substituents in 2,3-diarylfumaronitriles. Distinct molecular orientation and packing arrangements in crystalline 2,3-diarylfumaronitriles ensured perturbed electronic communication amongst the nearest and non-nearest molecules through an interplay of excimer and dipole couplings. As a result, the intermolecular interactions govern the solid state luminescence of molecules.