A new kind of low molecular-mass organic gelator (LMOG) π-electron-deficient N,N-octyl-7,7′-diazaisoindigo (1) with aggregation-induced enhanced emission (AIEE) phenomenon is described. This organogel is capable of self-assembling through intermolecular H-bonding and π-π interactions between diazaisoindigo molecules. Its rheological properties, X-ray diffraction pattern, optical properties and theoretical calculations were investigated. The AIEE effect is exhibited in fluorescence during the formation of the supramolecular organogel, which persisted in the xerogel state, and the spectral red-shifts suggest the formation of J-type aggregates during the gelation process via π-π interactions in microbelts or 3D networks. Fluorescence lifetime and quantum yield significantly increase from dilute solution to the aggregate state. From a theoretical perspective, the effect of the aggregation of 1 on the photophysical properties was also studied by means of the density functional theory (DFT). In this sense, the lowest energy electronic transitions were calculated for both the single molecule and different size aggregates in order to predict spectral shifts. In addition, the geometry and molecular properties of the excited state were analyzed in different material states.

This work was financially supported by the MICINN of Spain (Grant CTQ2013-40562-R), by Consejería de Economia y Conocimiento, Junta de Andalucía (Grant FQM-337), Consejería de Educación y Ciencia de la Junta de Comunidades de Castilla-La Mancha (Project PEII11-0279-8538), and Diputación de Albacete (DIPUAB-16-GARZONRUIZ). The authors thank Centro de Servicios de Informática y Redes de Comunicaciones (CSIRC), Universidad de Granada (Spain),and Servicio de Supercomputación de la Universidad de Castilla-La Mancha for providing the omputing time. J.P. thanks Dr. M. Ramírez for his help in the PXRD pattern representation and interpretation and E. Rodríguez and P. Ciriafor their support. The authors thank Prof. J. Reimers, University of Technology Sydney, for allowing us to use the DUSHIN program.

Peer Reviewed