Pseudo Photochromism Induced Halochromism: Reversible Color Change for Porphyrin Derivatives and their Molecular Recognition Towards Hydrochlorides

A series of meso-substituted phenyl porphyrin derivatives were selected for investigating their photochromic behavior in several aryl chloride solutions. After ultraviolet irradiation (UVI, λ = 360 nm), the solutions’ color changed rapidly and sensitively from pink to bright green; and their pink color can be recovered gradually when the green samples are radiated under visible light (VR, λ > 500 nm) or placed around diffused light at ambient conditions. Notably this photochromic behavior can be completely stimulated by a halochromic method. A porphyrin H2TMPP 3 was selected as a typical sample for revealing this chromic mechanism, and molecular configuration for the green porphyrin chromophores was proposed based on crystal assembly of H2TPP 1. Finally the sensitive molecular recognition of H2TMPP 3 towards hydrochlorides was examined.