<p>The molecular geometry in the ground singlet S₀ and lowest triplet T₁ states was optimized, the energies of molecular orbitals were calculated, and the energy of the T₁ → S₀ transition was determined using density functional theory quantum-chemical calculations for two families of polysubstituted porphyrins and metalloporphyrins with various peripheral substitution architectures containing either NO₂ groups or NO₂ and NH₂ groups at the C_m-positions of the macrocycle to form an asymmetric electronic-density distribution in the macrocycle. A change in the number of attached NO₂ groups in poly-NO₂-substituted porphyrins was found to lead to a similar stabilization of the Gouterman orbitals, which, as a result, did not lead to fundamental changes in the magnitude of the energy gap ΔE(T₁–S₀). At the same time, a significant decrease in the ΔE(T₁–S₀) gap was found in poly-NO₂–NH₂-substituted porphyrins and was caused by substantial stabilization of the LUMO orbital. Conformers with an alternating arrangement of NO₂ and NH₂ groups had a smaller ΔE(T₁–S₀) gap than conformers with an adjacent arrangement of the same groups. The triplet one-electron configurations ³(e_gxa2_u) and ³(e_gya_1u) did not mix and the T₁ → S₀ transition had a one-electron e_gx → a_1u configuration in all studied porphyrins.</p>