Halochromic Switch from the 1st to 2nd Near-Infrared Window of Diazapentalene–Dithienosilole Copolymers

Abstract

Halochromic switch from the 1st to 2nd near-infrared window of diazapentalene–dithienosilole copolymers is reported. The diazapentalene repeat unit presents an imine group that can be either protonated by a Brønsted acid or coordinated with a Lewis acid. As a consequence, the wavelength of maximum absorbance was switched from 840 to 1070 nm. Experimental data obtained by spectrophotometry and cyclic voltammetry were combined with theoretical density functional theory calculations to explain the reversible halochromic behavior of these copolymers and the adducts that are formed during the reactions. As they can undergo analyte-induced absorption shifts in the near-infrared, these materials should prove useful as biological/chemical sensors.