Spectroscopic investigation and theoretical modeling of benzothiadiazole-based charge-transfer chromophores: From solution to nanoaggregates
Résumé
Experimental and theoretical investigations are presented on four quadrupolar molecules constituted of a central electron-acceptor 2,1,3-benzothiadiazole conjugated at both sides with electron-donating thiophene (or 2,2′-bithiophene) substituted groups. Previous investigation of their physicochemical properties demonstrated that thermally induced self-organization might be achieved for one of them. In this study, we further explore the structure–properties relationships for these quadrupolar chromophores also examining their aggregation behavior in organic nanoparticles. Strong spectroscopic evidence of J-aggregates formation is obtained, favored by the presence of branched terminal alkyl chains. The surprisingly low fluorescence quantum yield of these J-aggregates is rationalized within the essential-state model approach.