This work reports on electronic structures of hybrid quasi 2D lead iodide perovskites with linear unsaturated organic diamine cations containing six carbon atoms. Based on an actual structure of 1,6-diaminium lead iodide, a series of seven compounds with organic diamines ranging from 3-hexene-1,6-diamine to 1,3,5-hexatriyne-1,6-diamine was constructed. DFT calculations reveal domains in electronic structures of all the studied 2D compounds which are probably due to quantum-size effects. Electronic band structures of the considered species with π-conjugated organic cations possess flat unoccupied energy levels just like quasi low-dimensional hybrid metal halide perovskites with aromatic organic cations do. Energies of the flat unoccupied levels are tunable via electron-withdrawing/donating substituents at carbon-carbon double bonds. Owing to a similarity between the studied compounds with π-conjugated organic cations and quasi low-dimensional hybrid metal halide perovskites with aromatic organic cations the former are expected to be luminophores. © 2024 Elsevier Inc.