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Anionic cyclopentadienyl (Cp) and its pentamethyl-substituted derivative (Cp*) serve as crucial ligands for creating stable π-coordinated materials, including catalysts. From a structural perspective, the π-extended analog of Cp, known as an N-fused porphyrin (NFP), is recognized as an intriguing 18π aromatic chromophore, offering near-infrared (NIR) optical properties that can be fine-tuned through metal complexation. When coordinated with rhodium at the central NFP core, it forms a sandwich binuclear rhodium(III) complex along with terminal and bridging chloride ligands, denoted as Rh-1 , and its bromo derivative, Rh-1-Br. In contrast to the bis-NFP complex of iron(II) reported previously by our team, both Rh-1 and Rh-1-Br complexes exhibit strong NIR optical properties and narrow HOMO-LUMO energy gaps, attributed to minimal orbital interactions between the two co-facial NFP ligands. Leveraging these NIR absorption properties, we assessed the photothermal conversion properties of Rh-1 and ligand 1 , revealing high conversion efficiency. This suggests their potential application as photothermal agents for use in photothermal therapy. The reaction of an N-fused porphyrin with rhodium(III) chloride salt under microwave irradiation has afforded a unique bis- μ -chloride-bridged rhodium(III) dimer. The resulting sandwich metal complex exhibited exceptional low energy gap and efficient photothermal conversion capability under the laser irradiation at 940 nm. [Display omitted] • Established a facile approach to expand the π-system in functional complexes like [Cp*RhCl 2 ] 2 , employing the endocyclic fused porphyrin analog, namely N-fused porphyrin (NFP) derivative. • The novel coordination mode of the sandwich dinuclear rhodium(III) complex Rh-1 and the bromo derivative Rh-1-Br was achieved using NFP ligands. • The bimetallic rhodium chromophore Rh-1 is responsive to the near-infrared longer-wavelength region. • The high light-harvesting ability of Rh-1 provides an efficient photothermal conversion material. [ABSTRACT FROM AUTHOR]