Excited state relaxation mechanisms of paracetamol and acetanilide.

The photochemical pathways of acetanilide and paracetamol were investigated using the XMS-CASPT2 quantum chemical method and the cc-pVDZ (correlation consistent polarized valence double- ) basis set. In both compounds, the bright state is the second excited state, designated as a L) state. Through a detailed exploration of the potential energy profile and the conical intersection structure between the L) and ground states, we gained a better understanding of how cleavage might occur in both molecules upon photoexcitation.

Photophysics of Adenine and Guanine fluorescent nucleobases embedded into DNA and RNA.

UV-VIS photoinduced events of A and G embedded into DNA and RNA are described by combining the Extended Multi-State Second-Order Perturbation Theory (XMS-CASPT2) and electrostatic embedding molecular mechanics methods (QM/MM). Our results point out that the S (ππ* L ) state is the bright state in both environments. After the photoexcitation to the S (ππ* L ) state, the electronic population evolves barrierless towards its minimum, from where the excess of energy can be dissipated by fluorescence.

Proton transfer in fluorescent secondary amines: synthesis, photophysics, theoretical calculation and preparation of photoactive phosphatidylcholine-based liposomes.

In this article, new fluorescent lipophilic based benzazoles were synthesized from the reaction between photoactive formyl derivatives and aliphatic amines followed by NaBH4 reduction with good yields. The photophysics of the benzazoles was investigated experimentally and theoretically. These compounds present absorption maxima in the UV region (∼339 nm) and fluorescence emission maxima in the cyan to green region with a large Stokes shift (∼175 nm) due to a proton transfer process in the excited state.