Supramolecular Polymer of Near-Infrared Luminescent Porphyrin Glass Mitsuhiko Morisue,* ,† Yuki Hoshino, † Masaki Shimizu, † Takayuki Nakanishi, § Yasuchika Hasegawa, § Md. Amran Hossain, ‡ Shinichi Sakurai, ‡ Sono Sasaki, ‡ Shinobu Uemura, ∥ and Jun Matsui ⊥ † Faculty of Molecular Chemistry and Engineering and ‡ Faculty of Fiber Science and Engineering, Kyoto Institute of Technology, Matsugasaki, Sakyo-ku, 606-8585 Kyoto, Japan § Graduate School of Engineering, Hokkaido University, North 13 West 8, Kita-ku, Sapporo 060-8628, Japan ∥ Department of Advanced Materials Science, Kagawa University, Hayashi-cho, Takamatsu 761-0396, Japan ⊥ Department of Material and Biological Chemistry, Faculty of Science, Yamagata University, Kojirakawa-cho, Yamagata 990-8560, Japan *S Supporting Information ABSTRACT: A comprehensive study of supramolecular polymer- ization 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-to- zinc 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. ■ INTRODUCTION The quest for solution-processable π-conjugated molecules that spontaneously order in thin films is the central subject in organic electronic materials because their geometric and energetic order/disorder in the π-stacked structures dominantly operates on the photoelectronic functionalities. 1−5 Recently, we found “porphyrin glass”; porphyrins bearing 3,4,5-tri((S)-3,7- dimethyloctyloxy)phenyl groups at the meso-positions form amorphous molecular glass and form intermolecular excimers which are luminescent at the near-infrared (NIR) wavelengths region (approximately 970 nm). 6 The results highlighted a new approach to surpass general obstacles for NIR emission, such as energy gap law; nonradiative decay becomes fast as the optical band gap narrows. 7,8 Our present challenge focuses on the supramolecular engineering π-system of porphyrin glass. Supramolecular interactions are advantageous in the direct fabrication of well-organized molecular assemblies and in the pursuit of excellent photoelectronic properties because one of the most distinct features of these reversible interactions lies in their ability to funnel thermodynamic structures to the most stable one. For instance, noncovalent interactions are possible implementation for the controlled the π-stacked morphology, as representatively exemplified by J-aggregates, 9 although strong π-stacked interaction is an intrinsic disturbance. In this context, supramolecular polymers, which have emerged as a novel type of polymeric materials, 10−13 could introduce a simple approach to solution-processable materials, including amorphous molecular glass. The current molecular design of supramolecular polymers introduces a slipped-cofacial stack of porphyrin planes by extracting the essential unit structure from natural photo- synthetic light-harvesting antenna complexes, wherein circularly arranged bacteriochlorophyll pigments in a successive slipped- cofacial stack efficiently capture sunlight and transport excitons quantitatively to the neighboring subunit. 14−18 Aimed at supramolecular polymerization of porphyrin glass, the present molecular design employed self-complementary methodology; two zinc (2-pyridylethynyl)porphyrin planes are held together Received: February 14, 2017 Revised: March 26, 2017 Article pubs.acs.org/Macromolecules © XXXX American Chemical Society A DOI: 10.1021/acs.macromol.7b00316 Macromolecules XXXX, XXX, XXX−XXX