Fluorinated Merophosphinine and Phosphinine Dyes: Synthesis and Evaluation of UV-Visible Light Absorption Properties

Merophosphinine and phosphinine dyes were reported as phosphorus atom equivalents of merocyanine and cyanine dyes in the 1960s. Although these dyes are excellent sensitizers for enhancing photographic performance, their development has been considerably retarded because of difficulties in the synthetic process. Previously, while investigating the reactivity of fluoroalkenes with various nucleophiles, we developed fluorinated merophosphinine and phosphinine scaffolds in a single reaction step; however, we did not investigate their ultraviolet-visible (UV-vis) light absorption properties further. Therefore, in this study, we synthesized fluorinated merophosphinines and phosphinine derivatives using triphenylphosphonium ylides with various R substituents [R = H, C6H5, 4-MeOC6H4, 4-PhC6H4, or C6F5] and octafluorocyclopentene to study their absorption characteristics. Thermogravimetric analyses (TGA) indicated that several synthesized derivatives were thermally stable at temperatures above 241 °C. Additionally, when studied in various solvents, the fluorinated merophosphinine and phosphinine dyes exhibited well-defined maximum absorption wavelengths (λabs) in the 364–375 and 420–474 nm ranges, respectively. Thus, fluorinated merophosphinine and phosphinine derivatives may serve as promising thermally stable functional dyes for future technical applications.