Synthesis and Photophysical Properties of λ5‑Phosphinines as a Tunable Fluorophore

A practical synthesis of a variety of λ5-phosphinines, which show distinct fluorescence both in solution and solid state, is described. Both C4-selective electrophilic substitutions and the following conversions realized an easy preparation of a wide range of derivatives having several substituents for electronic modification, which provides the potential for fine-tuning of the photophysical properties.