Butterfly‐like Tetraazaacenequinodimethane Derivatives: Synthesis, Structure and Halochromic Properties

Two novel molecules TAP and TAH with pronounced reversible halochromic properties have been synthesized and fully characterized. Their butterfly-like structures have been confirmed through single-crystal X-ray diffraction. Their UV-Vis absorption after protonation dramatically red-shifted with naked-eye-visible color change in a very dilute concentration of 10-5 M. Note that the original color of the solution can be recovered after the neutralization with a base.Ministry of Education (MOE)Q.Z. acknowledges financial support from AcRF Tier 1 (RG 111/17,RG 2/17, RG 114/16,RG 113/18)and Tier 2 (MOE2017-T2-1-021and MOE 2018-T2-1-070),Singapore.X.L. thank the support from the National Natural Science Foundation of China(21676188) and the Science and Technology Plan Project of Tianjin(19ZXNCGX00020).J.Z. acknowledges financial support from Na-tional Natural Science Foundation of China, Grant Nos. 21773016.QZ also thanks the support from State Key Laboratory of Supramolecular Structure and Materials, Jilin University (sklssm2020041