Density functional theory and time-dependent density functional theory calculations provide pictures of the molecular orbitals involved in the ground and excited states of two cyano derivatives of 8′-apo-β-caroten-8′-al synthesized via an acid−base-catalyzed Knoevenagel condensation reaction. Population analysis shows that the symmetry-allowed transition, S0 (1Ag) → S2 (1Bu) based on the C2h symmetry is a HOMO (highest occupied molecular orbital) to LUMO (lowest unoccupied molecular orbital) π → π* transition with electron densities located mostly on the polyene chain. Calculated and actual steady-state absorption spectra show similar features with low-energy peak maxima between 550 and 600 nm.

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