A New Soluble Copper Phthalocyanine Derivative as a Smart Material

Copper phthalocyanine (CuPc) and its derivatives are considered as candidate materials in many applications. Particularly, easy and sensitive film-forming ability, commercial availability, chemical stability, and ease in tailoring its molecular structure make CuPc a versatile material. On the other hand, main challenge that Pcs often exhibit is their poor solubility in organic solvents. In this sense, this work involves designing of new CuPc derivatives by introducing suitable substitutions to improve the solubility in organic solvents. Specifically, [2,9,16,23-tetra{(4,5-Diphenyl-1H-imidazole)-2-yl-thio}phthalocyaninato-copper(II)] (1) and [2,9,16,23-tetra{(4,5-Diphenyl-1-methyl-1H-imidazole)-2-yl-thio}phthalocyaninato-copper(II)] (2) were prepared. The results show that compound 1 is soluble in tetrahydrofuran (THF), dimethylformamide (DMF), and dimethyl sulfoxide (DMSO), and compound 2 is soluble in chloroform, acetone, methanol, THF, DMF, and DMSO. Optical and spectroscopic properties of the synthesized compounds were also investigated, and it was determined that the energy bang gaps of compounds 1 and 2 are 1.70 eV and 1.56 eV, respectively. Strikingly, we demonstrate that compound 1 is exhibiting a rapid and reversible color change behavior upon altering pH in the entire pH spectrum. As it is known, materials that respond reversibly to chemical and/or physical stimuli in a controllable fashion are regarded as smart materials. Hence, we report that compound 1 is actually a smart material that can be used as a simple yet efficient pH sensor.