A p‐Quinodimethane‐Bridged Porphyrin Dimer. Issue 49 (22nd October 2013)

• Record Type: Journal Article
• Authors: Zeng, Wangdong; Ishida, Masatoshi; Lee, Sangsu; Sung, Young Mo; Zeng, Zebing; Ni, Yong; Chi, Chunyan; Kim, Dongho; Wu, Jishan
• Is Part Of: Chemistry. Volume 19:Issue 49(2013)
• Page Start: 16814
• Page End: 16824
• Publication Date: 2013-10-22
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201302023
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>A <italic>p</italic>‐quinodimethane (<italic>p</italic>‐QDM)‐bridged porphyrin dimer <bold>1</bold> has been prepared for the first time. An unexpected Michael addition reaction took place when we attempted to synthesize compound <bold>1</bold> by reaction of the cross‐conjugated keto‐linked porphyrin dimers <bold>8 a</bold> and <bold>8 b</bold> with alkynyl/aryl Grignard reagents. Alternatively, compound <bold>1</bold> could be successfully prepared by intramolecular Friedel–Crafts alkylation of the diol‐linked porphyrin dimer <bold>14</bold> with concomitant oxidation in air. Compound <bold>1</bold> shows intense one‐photon absorption (OPA, <italic>λ</italic><sub>max</sub>=955 nm, <italic>ε</italic>=45400 <sc>M</sc><sup>−1</sup> cm<sup>−1</sup>) and a large two‐photon absorption (TPA) cross‐section (<italic>σ</italic><sup>(2)</sup><sub>max</sub>=2080 GM at 1800 nm) in the near‐infrared (NIR) region due to its extended π‐conjugation and quinoidal character. It also exhibits a short singlet excited‐state lifetime of 25 ps. The cyclic voltammogram of <bold>1</bold> displays multiple redox waves with a small electrochemical energy gap of 0.86 eV. The ground‐state geometry, electronic structure, and optical properties of <bold>1</bold> have been further studied by density functional theory (DFT) calculations and compared with those of the keto‐linked dimer <bold>8 b</bold>. This research has revealed that incorporation of a <italic>p</italic>‐QDM unit into the porphyrin framework had a significant impact on its optical and electronic properties, leading to a novel NIR OPA and TPA chromophore.</p> </abstract>