Bismepines are 3-fold unsaturated sevenmembered rings containing one bismuth atom. A set of dibenzobismepine complexes have been synthesized and isolated, among them a dinuclear bismepine, halobismepines, and cationic bismepines. They were investigated with respect to the structural properties, olefin-bismuth interactions, heteroaromaticity, and Lewis acidity (including a comparison with a range of simple bismuth and group 13 Lewis acids). Applied analytical techniques include NMR spectroscopy, single-crystal X-ray analysis, elemental analysis, and density functional theory calculations.