A three-coordinate cuprous complex exhibiting both photochromic and fluorescent sensing properties, and some TD-DFT calculations

Photo-functional materials with photochromic and fluorescent properties are very attractive because they have a wide range of applications. The design and research of fluorescent sensing materials for VOCs (volatile organic compounds) are also of great significance and challenge. Herein, we report a three-coordinate cuprous complex, XantphosCuI (1) (Xantphos is 4,5-bis(diphenylphosphino)-9,9-dimethylxanthene), and its reversible photochromism, photoluminescence, and fluorescent sensing for VOCs. The complex 1 was characterized by single-crystal X-ray diffraction as an isolated molecule with a triangle CuIP2 coordination geometry. In solution, complex 1 undergoes a reversible photochromic transition by alternating non-irradiation and irradiation with 365 nm UV light. Under UV light excitation, both the powder and doped thin film exhibit broadband photoluminescence emission. TD-DFT computational studies have been conducted to further understand the electronic transition properties of this compound. Based on 1, a fluorescent test strip was developed, and its fast and selective fluorescent sensing of pyridine vapor through enhanced mechanism was successfully realized. When exposed to vapor, the fluorescence of the test strip quickly becomes extremely bright. The fluorescent enhanced mechanism of the material was studied with the assistance of TD-DFT calculations, and it was proposed that the enhancement should be attributed to the charge transfer mechanism transition of the excited state after the coordination increase.