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Arsenic-containing conjugated polymers have recently attracted considerable attention, and dithieno[3,2-b:2′,3′-d]arsole is a typical monomer unit often used to construct them. In conventional polymer design, long alkyl chains, which improve the solubility of the resultant polymers in organic solvents, should be introduced on the coupling partner and/or at the 3-positions of the fused thiophene rings. The former strategy cannot be used for comonomers in which alkyl group substitution is difficult, and in the latter strategy, the steric hindrance of the alkyl chains may distort the planarity of the polymer chain. Therefore, we developed a novel monomer in which an alkoxyphenyl group is substituted on the arsenic atom. Polymers with high planarity and solubility were developed using benzothiadiazole and benzoxadiazole monomers. Most importantly, the polymers exhibited near-infrared emissions (emission maximum: up to 886 nm) owing to their planarity.

Four monocarborane anion-based compounds connected to a pyrene moiety were synthesized by combining two monocarborane anion scaffolds and two counter cations. The effects of the cage structure and the counter cation on the optical properties were investigated from UV‒vis absorption and photoluminescence (PL) measurements. The PL spectra in the solid state were unique for each compound, derived from the different shapes of the carborane cage and counter cation. These results suggest great potential for designing a monocarborane anion-based chromophore.Four monocarborane anion-based compounds connected to a pyrene moiety were synthesized by combining two monocarborane anion scaffolds and two counter cations. The PL spectra in the solid state were unique for each compound, derived from the different shapes of the carborane cage and counter cation. These results suggest great potential for designing a monocarborane anion-based chromophore.