Black hybrid iodobismuthate containing linear anionic chains
Three hybrid 1,1'-(1,n-alkanediyl)bis(4-methylpyridinium) iodobismuthates 1 - 3 were prepared by a facile solution route and showed thermal stability in air up to 230°C. The structures of solid 1 and 3 contain zero-dimensional anions, and the structure of 2 contains one-dimensional linear anionic chains [BiI5]n2n-. Photoluminescence (PL) in the spectral range between 600 and 750 nm was observed for 1 and 2. DFT calculations and optical studies confirmed that compounds 1−3 are semiconductors with band gaps of 1.73−2.10 eV, which corresponds with their intense black (for 2) or red (for 1 and 3) colors. The optical absorption of 2 in the red spectral range is primarily due to charge transfer from the I5p orbitals at the top of the valence band to the Bi6p orbitals at the bottom of the conduction band.