NBN unit functionalized pyrene derivatives with different photophysical and anti-counterfeiting properties

Pyrene derivatives 1 and 2, containing a five or six-membered diazaborole moiety (NBN unit), have been designed and prepared by the reaction of the corresponding pyrene-boronic acids with diamines unit. Spectroscopic properties of dyes 1 and 2 in three solvents and solid-state were well investigated. Dye 1 had cyan emission with moderate quantum yield in THF. Almost no solvatochromism in absorption spectra are observed for dyes 1 and 2, whilst a remarkable solvatochromic emission is found for 1. Both dyes exhibited fluorescence with absolute quantum yields of 0.30 for 1, 0.09 for 2 in the solid-state. The relationships between structure and property, especially the electronic effect between the pyrene and five or six-membered NBN moiety, were systematically studied based on optical spectroscopy, X-ray analysis, and theoretical calculations. The solid-emissive dyes 1 and 2 could be applicable as anti-counterfeiting ink by the experiment of fluorescent labeling for writing pattern and banknote.