Azulenocyanine: a new family of phthalocyanines with intense near-IR absorption.

Azulenocyanine, having four azulene units fused to a tetraazaporphyrin skeleton, is a structural isomer of naphthalocyanine. We synthesized the first example of an azulenocyanine from 1,3-di-tert-butyl-5,6-dicyanoazulene. The macrocycle exhibits broad absorption over the visible and near-IR regions far beyond 1000 nm. Theoretical calculations and electrochemical experiments show the LUMO energy level is drastically lowered. Azulenocyanine represents a new type of oxidation-stable near-IR dye.