Synthesis and properties of rhenium(I) bridged boron-dipyrromethene dyad

Abstract

We synthesized the hexa-coordinated Re(I) bridged BODIPY dyad 1 in decent yield by thermal reaction of benzimidazole substituted BODIPY 2 with Re(CO)5Cl. The dyad 1 was characterized by ¹H, ¹³C, ¹¹B, ¹⁹F NMR, ESI-MS, FTIR, UV-vis and electrochemical techniques. In Re(I) bridged dyad 1, the Re(I) ion is hexa-coordinated and coordinates with nitrogen atoms of two benzimidazole units, three axial carbonyl ligands and one chloride atom. The presence of three carbonyl groups in dyad 1 was verified by ¹³C NMR and IR spectroscopy. The absorption and steady-state fluorescence spectra of Re(I) bridged BODIPY dyad showed a slightly broad and hypsochromically shifted absorption and emission bands compared to BODIPY 2. The electrochemical studies indicated that, the Re(I) bridge BODIPY dyad 1 was easy to reduce compared to BODIPY 2 supporting the electron deficient nature dyad upon Re(I) ion binding. The molecular structure of dyad 1 was further elucidated by DFT computational studies.