Synthesis and properties of benzothiadiazole-pyridine system: The modulation of optical feature

Abstract

In this work, two new benzothiadiazole (BTD)-based compounds 1 and 2 were elaborately designed and synthesized, to explore the modulation on the interesting optical properties. Briefly, bipyridine-substituted compound 1 was synthesized via a modified Buchwald-Hartwig amination reaction with relatively high yield, and then derivative 2 was prepared by a following dehydrogenation reaction. The result in steady-state spectroscopic analysis and DFT/TDDFT calculation suggest the readily polarized nature of 1. In contrast, the readily polarized nature was declined in π-conjugated molecule 2, indicating the blue-shifted absorption and emission. Interestingly, negative cubic nonlinear refraction behavior in 1 is greater than that in π-conjugated system 2. Furthermore, in case 1 or 2, the photophycal property was considerably influenced by the external transition metal ion (M = Ag+, Cu2+ or Fe3+). Especially, because of the existence of external Fe3+ in case 1, initially negative nonlinear refraction signal became a positive one. Such exciting result is quietly useful for the design and synthesis of new functional BTD-based dye material.