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[email protected] Current Inorganic Chemistry, 2014, 4, 59-67 59 Pseudo Photochromism Induced Halochromism: Reversible Color Change for Porphyrin Derivatives and their Molecular Recognition Towards Hydrochlorides Ya Hong Wu1, Lin Lin Qin1, Yan Yan1,*, Shan Ling Tong1, Yan Wang1, Jing Zhang2, Ling Ling Hu1 1 and Jian Yu 1College of Light Industry & Chemical Engineering, Guangdong University of Technology, Guangzhou 510006, P.R. China; 2College of Chemical Engineering, Zhuhai Campus, Beijing Institute of Technology, Zhuhai 519085, P.R. China Abstract: A series of meso-substituted phenyl porphyrin derivatives were selected for investigating their photochromic behavior in several aryl chloride solutions. After ultraviolet irradiation (UVI, = 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, > 500 nm) or placed around diffused light at ambient conditions. Notably this pho- tochromic 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. Keywords: Halochromism, molecular recognition, photochromism, ultraviolet irradiation, visible radiation. INTRODUCTION Both porphyrin and phthalocyanine components acted as assistant chromospheres to enhance the chromic phenomena Photochromism (phototropy) had been attracting research of the covalently linked groups, but the chromism from these attention for a long time [1, 2]. Phytochromes as signal- macrocyclic molecules themselves were seldom discussed.