Synthesis, Structural, Electrochemical and Energy Transfer Studies of π‐Extended Mono‐β‐Functionalized Porphyrin Dyads

摘要： A series of π-conjugated mono-β-functionalized donor-acceptor porphyrin dyads (1-4) with various (phenyl, naphthyl, anthracenyl and pyrenyl) donors and their metal complexes (M = Zn(1a-4a), Cu(1b-4b), Co(1c-4c) and Ni(1d-4d)) were synthesized and characterized by various spectroscopic and electrochemical techniques. Modified one-step Horner-Wadsworth-Emmons reaction was performed on monoformyl porphyrin to get ethenyl linked mono-β-porphyrin dyads in good to excellent yields (70-90%). Red shifted absorption and emission spectra were observed as compared to unsubstituted pristine tetraphenylporphyrins due to π-extended donors. Time resolved fluorescence studies confirmed the effective intramolecular F?rster energy transfer from donor moiety to porphyrin core in anthracene and pyrene appended porphyrin dyads. DFT and TD-DFT optimization signified the orientation of donor and acceptor plays a vital role in energy transfer as co-planarity of donor with porphyrin core increases the energy transfer efficiency. The distribution of electron density on HOMOs and LUMOs indicated the EET mechanism from donor moiety to porphyrin acceptor core. All porphyrin dyads exhibited cathodic shift in their oxidation potential suggesting facile oxidation of porphyrin core due to π-extension and the presence of electron donating moieties. Finally, femtosecond transient absorption spectral studies were performed to secure evidence of excitation transfer and kinetic information of the energy transfer event in the dyads.