Three new hybrid two-dimensional (2D) organic–inorganic semiconductors are presented, which contain lead halides and a mixture of hexanediamine-based isomers in the stoichiometry [2,2,4 (2,4,4)- trimethyl-1,6-hexanediamine]PbX 4 (X = I, Br, Cl). These hexanediamine derivatives, with attached methyl groups at the carbon backbone of both isomers, determine the packing of the organic layers between the inorganic 2D sheets, while the optical absorption and photoluminescence spectra reveal excitonic peaks at T = 77 K and room temperature. The as-synthesized semiconductors were stored for three years in the dark and under low humidity and were examined again and the results were compared to those of the fresh materials. The chloride analogue, after the three year storage, displays white-like luminescence. The use of non-equivalent isomer and racemic mixtures in the organic component to form hybrid organic–inorganic semiconductors is an efficient method to alter the properties of 2D perovskites by tuning the isomers’ chemical functionalities. Finally, a comparison of the observed excitonic absorption and photoluminescence signals to that of analogous 2D compounds is discussed.