Study On The Synthesis And Properties Of Pyridylene-Bridged Subporphyrin Arrays And Porphyrin-Subporphyrin Hybrids

Subporphyrin is a type of macrocyclic compound consisting of three pyrrole units and three methine groups(=CH)in sequence.Subporphyrin has played a unique role in the chemistry of porphyrin as a ring-contracted porphyrin,owing to its 14π aromaticity and bowl-shaped structure.In recent years,cyclic porphyrin arrays have received considerable attention because of their unique properties and potential applications in two-photon absorption.However,there are only limited reports on subporphyrin arrays.Research on subporphyrin arrays is expected to improve their optical and electronic properties,so that they can be better applied to nonlinear optical materials and dyes for photodynamic therapy.In addition,the compounds formed by the fusion of aromatic rings to porphyrin cores are highly conjugated.They have small HOMO-LUMO gaps,and have potential application in two-photon absorption,nonlinear optics and organic semiconductors.Direct double linkages of porphyrin and subporphyrin are expected to obtain functional molecules with strong near-IR absorption properties.In this thesis,pyridylene-bridged subporphyrin arrays and porphyrin-subporphyrin hybrids were successfully prepared.The structures of these compounds were characterized by 1H NMR and High-Resolution MALDI-TOF MS spectrometry.The structures of typical compounds were further confirmed by 13C NMR and X-ray diffraction analysis.The target products were studied based on their UV/Vis absorption,fluorescence quantum yield and electrochemical properties.The main work of this paper is listed as follows:(1)The linear bromopyridyl-terminated oligomers were synthesized by Suzuki-Miyaura coupling reaction between β,β’-diborylsubporphyrins and 2,6-dibromopyridine.With the linear precursors in hand,pyridylene-bridged subporphyrin dimer,trimer and tetramer were successfully synthesized by Suzuki cross-coupling reaction of bromopyridine-terminated linear oligosubporphyrins withβ,β’-diborylsubporphyrins.1H NMR spectra of these cyclic compounds indicated that they had a relatively symmetric structure in solution,and their UV/Vis absorption spectra showed a strong electronic interaction existed between pyridine and subporphyrin unit.(2)Using meso-brominated subporphyrin and meso-borylated porphrin as raw materials,meso-meso-linked subporphyrin-porphyrin oligomers were obtained by Suzuki-Miyaura cross coupling reaction,and meso-meso,β-β conjugates were obtained by oxidation reaction.The photophysical properties and electrochemistry of the target compounds were studied.The results showed that compared with meso-meso-linked porphyrin-subporphyrin arrays,the absorption spectrum of meso-meso,β-β conjugates exhibited remarkably red-shifted absorption bands.Furthermore,the electrochemical HOMO-LUMO gap of fused porphyrin-subporphyrin hybrids were distinctly smaller than those of unfused porphyrin-subporphyrin hybrids,suggesting their effectively conjugated π-electronic network.