Search

• Ultrafast photo-physical properties of DASPA are studied by the TA spectra. • Simulated results suggest multiple binding locations between DASPA and protons. • TA results indicate a solvation relaxation rather than a state-to-state transition. • An energy model is proposed to demonstrate the relaxation mechanism. The ultrafast photophysical properties of dimethyl amino styryl pyridine acetonitrile (DASPA) were studied by the femtosecond transient absorption spectra (TA). The results show no evidence of state-to-state relaxation. The excited energy is released by the interaction between DASPA and solvent molecules. The solvation relaxation in protic solutions is faster than that in aprotic solutions, which results in a rapid decay of fluorescence. An energy diagram is finally proposed to interpret the relaxation mechanism. [ABSTRACT FROM AUTHOR]

[Display omitted] • The intermolecular hydrogen bonds in uric acid aqueous solution were studied. • The configuration search and geometry optimization of uric acid–water cluster were carried out. • Position and intensity of interaction are discussed by AIM and RDG analyses. Cluster structures that may be associated between uric acid molecules and different numbers of water molecules were studied in detail using density functional theory (DFT) at the B3LYP-D3(BJ)/6–31 + G (d, p) level. When the number of water molecules increases from one to three, the cluster configuration changes from planar single-ring structure to double-ring structure. At the same time, the weak interactions were analyzed by atomic analysis (AIM) and reduced density gradient (RDG) methods. Finally, the theoretical Raman spectra show that the N–H Raman peak in the uric acid molecule is redshifted and the hydrogen bond interaction is enhanced. [ABSTRACT FROM AUTHOR]