| Institution: | 1. Department of Chemistry and Biochemistry, Graduate School of Engineering, the Center for Molecular Systems, Kyushu University, Fukuoka, 819-0395 Japan
These authors contributed equally to this work.;2. Department of Chemistry and Biochemistry, Graduate School of Engineering, the Center for Molecular Systems, Kyushu University, Fukuoka, 819-0395 Japan;3. Department of Chemistry and Spectroscopy for Functional π-Electronic Systems, Yonsei University, Seoul, 03722 Korea;4. Graduate School of Advanced Health Sciences, Saga University, Saga, 840-8502 Japan;5. Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033 Japan;6. Cluster for Pioneering Research (CPR), Advanced Elements Chemistry Laboratory, RIKEN, Saitama, 351-0198 Japan;7. Advanced Research Support Center, Ehime University, Matsuyama, 790-8577 Japan;8. Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, 153-8902 Japan |
| Abstract: | The synthesis of organometallic complexes of modified 26π-conjugated hexaphyrins with absorption and emission capabilities in the third near-infrared region (NIR-III) is described. Symmetry alteration of the frontier molecular orbitals (MOs) of bis-PdII and bis-PtII complexes of hexaphyrin via N-confusion modification led to substantial metal dπ–pπ interactions. This MO mixing, in turn, resulted in a significantly narrower HOMO–LUMO energy gap. A remarkable long-wavelength shift of the lowest S0→S1 absorption beyond 1700 nm was achieved with the bis-PtII complex, t -Pt2-3 . The emergence of photoacoustic (PA) signals maximized at 1700 nm makes t -Pt2-3 potentially useful as a NIR-III PA contrast agent. The rigid bis-PdII complexes, t -Pd2-3 and c -Pd2-3 , are rare examples of NIR emitters beyond 1500 nm. The current study provides new insight into the design of stable, expanded porphyrinic dyes possessing NIR-III-emissive and photoacoustic-response capabilities. |
