We propose a ring substitution as a method of modulation of optoelectronic properties of organo-metal halide perovskites containing unsaturated heterocyclic cations. Periodic DFT calculations of tin trichloride perovskites with arizinium cation and its derivatives show that an introduction of the electron-withdrawing –C[tbnd]N and –F groups into azirinium ring stabilizes the materials' CBs formed from antibonding molecular π-orbitals of the ring. This leads to a decrease of the perovskite bandgaps as compared to that of the parent arizinium tin trichloride (1.06 eV). The effect of the electron-donating groups –CH₃ and –NH₂ on the materials’ CBs and bandgaps is opposite. The predicted bandgaps of the four perovskites cover the energy range of [0.52:1.93] eV. A combination of both electronic effects in one ring substituent allows for a finer tuning of the perovskite optoelectronic properties that is exemplified by fluorinated methylarizinium tin trichlorides. Bandgaps of these materials vary from 1.86 eV (R = -CH₃) to 1.17 eV (R = -CF₃). Thus, a ring substitution in unsaturated heterocyclic cations of organo-metal halide perovskites paves a way to modulating their optoelectronic properties in a wide energy range.