Supramolecular Polymer of Near-Infrared Luminescent Porphyrin Glass

A comprehensive study of supramolecular polymerization of ditopic zinc (2-pyridylethynyl)porphyrin dimer 1 in toluene and thin films was performed. A glass-forming porphyrin bearing 3,4,5-tri((S)-3,7-dimethyloctyloxy)phenyl groups, named "porphyrin glass", was introduced with the 2-pyridylethynyl group as a supramolecular organizing unit; two zinc (2-pyridylethynyl)porphyrins were held together by self-complementary pyridyl-tozinc coordination bonds to form a slipped-cofacial stack. Then, ditopic zinc (2-pyridylethynyl)porphyrin could be extended to a linear supramolecular polymer. The small binding constant limited the degree of supramolecular polymerization of 1 in toluene solution. In spin-cast film, on the other hand, 1 adopted a form of supramolecular polymer of porphyrin glass, which was effective enough to display a large bathochromic shift of the absorption bands exceeding the narrowest limit of the optical band gap extrapolated from the electronic structures in solution. The supramolecularly polymerized porphyrin glass formed excimer,which exhibited solid-state near-infrared (NIR) luminescence at approximately 1025 nm.