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<p>Flavin–amine interactions are central to neurotransmitter metabolism, yet how H-bonding and amine structure govern excited-state pathways remains unclear. Using lumichrome (LC) as a biomimetic model, we examine interactions and photobehaviour with sympathomimetic amines, norephedrine (Neph), ephedrine (Eph), and pseudoephedrine (Peph). In water, LC with amines readily forms anions. In dichloromethane, H-bonding drives ultrafast single-proton transfer (SPT) in the LC–Neph complex (~800 fs), followed by population redistribution (~14 ps) and a long-lived anion (τ ~5.4 ns), while LC–Eph and LC–Peph complexes show shorter lifetimes (~4.3–4.8 ns). Control experiments with phenethylamine confirm that the amine group drives SPT-mediated anion formation. Computational calculations support excitation-induced charge redistribution and SPT-mediated zwitterionic stabilisation. Nanosecond-millisecond transient absorption shows minor triplet quenching by Neph (τ ~0.74 → 0.66 μs), but Eph and Peph enhance quenching (τ ~0.45-0.55 μs) and photoproduct formation. This study unravels LC–sympathomimetic amine interactions, offering an avenue to interrogate excited-state pathways in flavin photochemistry.</p><p></p>

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Exploring the photodynamical landscape of biomimetic lumichrome–ephedrine-class amine complexes across femtosecond to millisecond regimes

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月1日

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  • Subhrakant Jena,
  • Mario de la Hoz Tomás,
  • Juan Ángel Organero,
  • Miquel Moreno Ferrer,
  • Abderrazzak Douhal

摘要

Flavin–amine interactions are central to neurotransmitter metabolism, yet how H-bonding and amine structure govern excited-state pathways remains unclear. Using lumichrome (LC) as a biomimetic model, we examine interactions and photobehaviour with sympathomimetic amines, norephedrine (Neph), ephedrine (Eph), and pseudoephedrine (Peph). In water, LC with amines readily forms anions. In dichloromethane, H-bonding drives ultrafast single-proton transfer (SPT) in the LC–Neph complex (~800 fs), followed by population redistribution (~14 ps) and a long-lived anion (τ ~5.4 ns), while LC–Eph and LC–Peph complexes show shorter lifetimes (~4.3–4.8 ns). Control experiments with phenethylamine confirm that the amine group drives SPT-mediated anion formation. Computational calculations support excitation-induced charge redistribution and SPT-mediated zwitterionic stabilisation. Nanosecond-millisecond transient absorption shows minor triplet quenching by Neph (τ ~0.74 → 0.66 μs), but Eph and Peph enhance quenching (τ ~0.45-0.55 μs) and photoproduct formation. This study unravels LC–sympathomimetic amine interactions, offering an avenue to interrogate excited-state pathways in flavin photochemistry.