Synthesis of Near-Infrared Fluorescent 2,3-Dicyano-6H-1,4-diazepines

Abstract

Abstract A series of novel 5-(2-arylethenyl)-, 5-(4-arylbutadienyl)-, 5-(6-arylhexatrienyl)-, and 5-(8-octatetraenyl)-, 5-aryl-7-(2-arylethenyl)-, and 5,7-bis(2-arylethenyl)-2,3-dicyano-6H-1,4-diazepines were synthesized by the reactions of 2,3-dicyano-5-methyl-6H-1,4-diazepines with aromatic aldehydes. These compounds showed intramolecular charge-transfer chromophoric systems from the arylethenyl to the 2,3-dicyano-6H-diazepine moieties. The shifts in UV–vis absorption bands were estimated by calculating the HOMO and LUMO energy levels. 2-(9-Julolidyl)ethenyl derivative showed the most intense fluorescence. The 6-(9-julolidyl)-1,3,5-hexatrienyl and 8-(9-julolidyl)-1,3,5,7-octatetraenyl derivatives exhibited the fluorescence maxima (Fmax) at 780 and 842 nm, respectively.