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A systematic approach to obtain bromobismuthates with various bismuth/halide ratios stabilised by 2,6-diisopropylanilinium cations [ArNH3] (Ar = 2,6-diisopropylphenyl) is presented. New bromobismuthate compounds [(ArNH3)(BiBr4)]∞ (1), [(ArNH3)3(Bi2Br9)]∞ (2), [(ArNH3)3(BiBr6)] (3) and [(ArNH3)4(BiBr6)(Br)] (4) with Bi/Br ratios of 1:4, 1:4.5, 1:6 and 1:7 have been isolated and structurally characterised. [Bi2Br9]∞ is a new structural motif in halobismuthate chemistry. In all the compounds, extensive hydrogen bonding is observed between the bromobismuthate moiety and the 2,6-diiosopropylanilinium cation, thus stabilising the inorganic–organic hybrid structures. Preliminary optical spectroscopic studies indicate that the optical band gap can be tuned by controlling the bismuth/halide ratio, which results in different dimensionalities in the halobismuthate structure. The compounds exhibit thermal stability up to 250 °C. [ABSTRACT FROM AUTHOR]

Synthesis of iodobismuthates and tuning their properties attracted a lots of attention due to their contribution in developing opto-electronic devices. Two 1-D polymeric iodobismuthate compounds, {[2,6-(NH 2) 2 PyH][BiI 4 ]} n (1), {[4-NMe 2 PyH][BiI 4 ]} n (2), [Py: Pyridine] have been reported, where structurally similar polymeric anionic iodobismuthate is stabilised by two different pyridinium cations namely 2,6-bis(amino)pyridine and 4-(N , N -dimethylamino)pyridine derivatives. The compounds have been characterised by single crystal XRD, IR and elemental analysis. It is interesting to observe that the structurally similar compounds differ drastically in their optical properties because of slight variation in the cations. Comparison in structural features and their thermal, optical properties (band gap: 1.91 eV (1); 2.10 eV (2)) have been discussed. Thermochromism is exhibited by 1. DFT studies of compound 1 has been performed considering the crystal structure measured at two different temperature and the role of cation in tuning the optical properties of iodobismuthates has been established. [ABSTRACT FROM AUTHOR]