Dependence of the excited-state manifold of lutein on polarisability

Lutein is a xanthophyll carotenoid with a conjugated system terminated by two ionone rings, one of which extends the π-conjugation. Its photophysical behaviour in different environments is poorly understood. Here, we report room-temperature excited-state characterisation of lutein in two solvents with strongly different polarisabilities, THF and CS₂, combining femtosecond transient absorption and femtosecond stimulated resonance Raman spectroscopy. In both environments, we resolve the same set of excited states, including a hot S₁ state, relaxed S₁, a weak ICT contribution coupled to S₁, and a longer-lived dark state with triplet-pair character, S*. Despite this shared state manifold, the two solvents produce markedly different behaviours. In CS₂, the S₁ absorption band is substantially red-shifted and broadened relative to THF, and the vibrational dynamics of the excited-state manifold evolve much less over time, indicating that highly polarisable environments suppress relaxation-driven spectral evolution. The S* dark state lifetime of ∼16 ps in THF increases to approximately 29 ps in CS₂, and its vibrational frequency shifts upward by 8 cm^-1, deviating from the scaling observed for linear carotenoids of comparable conjugation length.