Metalla-Carbaporphyrinoids Consisting of an Acyclic N-Confused Tetrapyrrole Analogue Served as Stable Near-Infrared-II Dyes

Biju Basumatary; Hidetoshi Tsuruda; Dariusz W Szczepanik; Jiyeon Lee; Jaehyeok Ryu; Shigeki Mori; Kyo Yamagata; Takayuki Tanaka; Atsuya Muranaka; Masanobu Uchiyama; Jiwon Kim; Masatoshi Ishida; Hiroyuki Furuta

doi:10.1002/anie.202405059

Metalla-Carbaporphyrinoids Consisting of an Acyclic N-Confused Tetrapyrrole Analogue Served as Stable Near-Infrared-II Dyes

Angew Chem Int Ed Engl. 2024 Jun 3;63(23):e202405059. doi: 10.1002/anie.202405059. Epub 2024 Apr 29.

Authors

Affiliations

¹ Department of Applied Chemistry, Graduate School of Engineering, Kyushu University, Fukuoka, 819-0395, Japan.
² Department of Theoretical Chemistry, Jagiellonian University, Faculty of Chemistry, Gronostajowa 2, 30-387, Krakow, Poland.
³ School of Integrated Technology, College of Computing, Integrated Science and Engineering Division, Underwood International College, Integrative Biotechnology and Translational Medicine, Graduate School, Yonsei University, Incheon, 21983, Korea.
⁴ Advanced Research Support Center, Ehime University, Matsuyama, 790-8577, Japan.
⁵ Department of Molecular Engineering, Graduate School of Engineering, Kyoto University, Nishikyo-ku, Kyoto, 615-8195, Japan.
⁶ Molecular Structure Characterization Unit, RIKEN Center for Sustainable Resource Science, 2-1 Hirosawa, Wako, Saitama, 351-0198, Japan.
⁷ Graduate School of Pharmaceutical Sciences, The University of Tokyo, Tokyo, 113-0033, Japan.
⁸ Department of Chemistry, Graduate School of Sciences, Tokyo Metropolitan University, Hachioji, 192-0397, Japan.

PMID: 38563771
DOI: 10.1002/anie.202405059

Abstract

We present herein the synthesis of novel pseudo-metalla-carbaporphyrinoid species (1M: M=Pd and Pt) achieved through the inner coordination of palladium(II) and platinum(II) with an acyclic N-confused tetrapyrrin analogue. Despite their tetrapyrrole frameworks being small, akin to well-known porphyrins, these species exhibit an unusually narrow HOMO-LUMO gap, resulting in an unprecedentedly low-energy absorption in the second near-infrared (NIR-II) region. Density functional theory (DFT) calculations revealed unique d_π-p_π-conjugated electronic structures involving the metal d_π-ligand p_π hybridized molecular orbitals of 1M. Magnetic circular dichroism (MCD) spectroscopy confirmed distinct electronic structures. Remarkably, the complexes feature an open-metal coordination site in the peripheral NN dipyrrin site, forming hetero-metal complexes (1Pd-BF₂ and 1Pt-BF₂) through boron difluoride complexation. The resulting hetero metalla-carbaporphyrinoid species displayed further redshifted NIR-II absorption, highly efficient photothermal conversion efficiencies (η; 62-65 %), and exceptional photostability. Despite the challenges associated with the theoretical and experimental assessment of d_π-p_π-conjugated metalla-aromaticity in relatively larger (more than 18π electrons) polycyclic ring systems, these organometallic planar tetrapyrrole systems could serve as potential molecular platforms for aromaticity-relevant NIR-II dyes.

Keywords: N-confusion; metalla-(anti)aromaticity; near-infrared; photothermal conversion; porphyrinoid.

Abstract

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