Design, Synthesis, and Characterization of Organometallic BODIPY-Ru(II) Dyads: Redox and Photophysical Properties with Singlet Oxygen Generation Capability†.

A series of Ru(II)-acetylide complexes ( Ru 1 , Ru 2 , and Ru 1 m ) with alkynyl-functionalized borondipyrromethene (BODIPY) conjugates were designed by varying the position of the linker that connects the BODIPY unit to the Ru(II) metal center through acetylide linkage at either the 2-( Ru 1 ) and 2,6-( Ru 2 ) or the meso -phenyl ( Ru 1 m ) position of the BODIPY scaffold. The Ru(II) organometallic complexes were characterized by various spectroscopic methods, including nuclear magnetic resonance (NMR) spectroscopy, infrared (IR) spectroscopy, CHN, and high-resolution mass spectrometry (HRMS) analyses. The Ru(II)-BODIPY conjugates exhibit fascinating electrochemical and photophysical properties. All BODIPY-Ru(II) complexes exhibit strong absorption (ε max = 29,000-72,000 M -1 cm -1 ) in the visible region (λ max = 502-709 nm). Fluorescence is almost quenched for Ru 1 and Ru 2 , whereas Ru 1 m shows the residual fluorescence of the corresponding BODIPY core at 517 nm. The application of the BODIPY-Ru(II) dyads as nonporphyrin-based triplet photosensitizers was explored by a method involving the singlet oxygen ( 1 O 2 )-mediated photo-oxidation of diphenylisobenzofuran. Effective π-conjugation between the BODIPY chromophore and Ru(II) center in the case of Ru 1 and Ru 2 was found to be necessary to improve intersystem crossing (ISC) and hence the 1 O 2 -sensitizing ability. In addition, electrochemical studies indicate electronic interplay between the metal center and the redox-active BODIPY in the BODIPY-Ru(II) dyads.