Axially Bonded 3‐Pyrrolyl BODIPY‐Zn ^II and Ru ^II Metalloporphyrin Triads: Synthesis and Properties

The 5,11‐dipyridyl 3‐pyrrolyl BODIPY building block was synthesized by coupling of 5,11‐dibromo 3‐pyrrolyl BODIPY with 4‐pyridine boronic acid under Pd(0) coupling conditions and used it for the synthesis of 3‐pyrrolyl BODIPY‐(Zn II porphyrin) 2 triad 4 and 3‐pyrrolyl BODIPY‐(Ru II porphyrin) 2 triad 5 by adopting “axial bonding strategy”. 1D and 2D NMR techniques have been used extensively to establish the molecular structures of both the triads. NMR studies indicated that the Ru(II)‐pyridine “N” bond was stronger in 3‐pyrrolyl BODIPY‐(Ru II porphyrin) 2 triad 5 compared to Zn(II)‐pyridine “N” bond in 3‐pyrrolyl BODIPY‐(Zn II porphyrin) 2 triad 4 . The absorption and electrochemical studies showed the features of both 3‐pyrrolyl BODIPY and metalloporphyrin units and steady state fluorescence studies indicated a possibility of energy transfer from donor metalloporphyrin unit to acceptor 3‐pyrrolyl BODIPY unit in 3‐pyrrolyl BODIPY‐(Zn II porphyrin) 2 in triad 4 . Furthermore, DFT studies supported the experimental observations and provided insights into the electronic structures and excited‐state properties of the triads.