Synthesis, Structure, Spectral, Electrochemical, and Theoretical Studies of Ru(II) Complexes of 3-Pyrrolyl BODIPY-Based Ligands
Pinky Chauhan, Kanhu Charan Behera, Mangalampalli Ravikanth
Abstract
3-Pyrrolyl BODIPY having an appended pyrrolyl group at the 3-position of BODIPY (4,4-difluoro-4-bora-3a,4a-diaza-s-indacene) and its functionalized derivatives have been used as ligands to prepare one example of Ru(II) complex of pyrrolyl dipyrrin and three unique examples of bichromophoric BODIPY-Ru(II) complexes in good yields. The complexes were characterized by HR-MS, 1D and 2D NMR, X-ray analysis for two complexes, absorption, cyclic voltammetry, and DFT/TD-DFT techniques. The X-ray structure of the Ru(II) complex of pyrrolyl dipyrrin revealed that the geometry around the Ru(II) ion was pseudo-octahedral with an arene unit occupying three coordination sites in η 6 -fashion and two nitrogen atoms of the dipyrrin ring and one chloro group adopting the “three legs piano-stool” structure. The X-ray structure of the bichromophoric BODIPY-Ru(II) complex revealed that the BODIPY core was planar and the central B(III) was coordinated with two pyrrole nitrogens of the dipyrrin unit and two axial fluoride ions in a tetrahedral geometry, and Ru(II) was bonded to appended pyrrole “N” and “N” of benzimidazole substituent present at the α-position of appended pyrrole, one chloro group, and one arene ring in a pseudo-octahedral geometry. The spectral studies revealed that the electronic properties of the BODIPY unit in BODIPY-Ru(II) complexes were significantly altered, and electrochemical studies indicated that the BODIPY-Ru(II) complexes exhibit one oxidation corresponding to Ru(II) to Ru(III) and one reduction corresponding to the BODIPY unit. The DFT/TD-DFT studies corroborated the experimental observations.