Crystallization induced enhanced emission in conformational polymorphs of a rotationally flexible molecule. Issue 14 (15th December 2015)

• Record Type: Journal Article
• Authors: Mallia, Ajith R.; Sethy, Ramarani; Bhat, Vinayak; Hariharan, Mahesh
• Is Part Of: Journal of materials chemistry. Volume 4:Issue 14(2016)
• Page Start: 2931
• Page End: 2935
• Publication Date: 2015-12-15
• Subjects: Materials -- Periodicals; Chemistry, Analytic -- Periodicals; Optical materials -- Research -- Periodicals; Electronics -- Materials -- Research -- Periodicals; 543.0284
• DOI: 10.1039/c5tc03188e
• Languages: English
• ISSNs: 2050-7526

Abstract

Abstract : The crystallization of weakly fluorescent 4-amino-2, 2′-bipyridine (AMBPY ) in solution phase under ambient conditions afforded three conformational polymorphs possessing enhanced emission. Abstract : The crystallization of weakly fluorescent 4-amino-2, 2′-bipyridine (AMBPY ) in solution phase under ambient conditions afforded three fluorescent conformational polymorphs. The marginal increase in the barrier to rotation observed inAMBPY as compared to unsubstituted 2, 2′-bipyridine could be attributed to the "buttressing effect" offered by the amino substituent at the meta position. A smaller yet significant difference in energy (0.1–2.6 kJ mol −1 ) with respect to the global minima facilitates the isolation ofAMBPY-I–III polymorphs. A unique nitrogen–nitrogen interaction is observed in two of the polymorphs, namely, AMBPY-I andAMBPY-III, promoted by cooperative C⋯H and N⋯H interactions. A crystallization-induced enhancement ( ca. 5–10 fold) in the fluorescence quantum yield ofAMBPY polymorphs is observed relative to the solution/amorphous state. Controlling the luminescence properties of molecular solids by tuning their packing arrangements via various interactions is an integral aspect in the construction of novel photo-functional materials.