Design and synthesis of D‐π‐A fluorescent dyes based on nicotinonitrile and azobenzene derivatives

Abstract

AbstractStudy the synthesis and fluorescent properties of a new series of D‐π‐A fluorescent dyes based on nicotinonitrile and azobenzene is the main objective for this work. Reduction with Zn/HCl, diazotization with HCl/NaNO2, and coupling using catalytic NaOH or AcONa are simple applied methods. Where, nicotinonitrile 3 was synthesized via reduction of nitro derivative 1 followed by diazotization with HCl/NaNO2 in acetic acid. The formed benzene diazonium chloride was coupled with several activated phenols, aniline, and α‐CH acids to yield the respective azo dyes 4‐11 in moderate to good yield. Dyes 11a‐d subjected to intermolecular cyclization with hydrazine hydrate resulted in pyrazole dyes 12‐15 in moderate yield. Dyes containing pyrazole moiety or electron‐withdrawing groups at the sixth position of pyridine nucleus exhibit stronger blue‐green emission (λfl.max = 503, 507, 500, 501, 502, 493, and 514 nm) than that of the rest of compounds.