Hydration structure and dynamics, ultraviolet–visible and fluorescence spectra of caffeine in ambient liquid water. A combined classical molecular dynamics and quantum chemical study

The Role of Hydrogen Bonding in the Raman Spectral Signals of Caffeine in Aqueous Solution

“…Unsurprisingly, the five water molecules in the first solvation shell coincide with the average number of HBs between the caffeine and the solvent based on geometric criteria (d X•••O w ≤ 3.5 Å and θ H w −O w −X ≤ 30 • , X being N9, O10, and O12 atoms in caffeine), as can be inferred from Figure 2b. The hydration structure of caffeine in aqueous solution has been studied in earlier [65] and recent [66] works using classical MD simulations, and the same hydration patterns were found. Running Coordination Number To further pinpoint the source of the stabilization when caffeine is dissolved in an aqueous solution, more selective scrutiny is included by performing a quantitative analysis of intermolecular interactions with NBO and QTAIM approaches.…”

“…Beyond the fair agreement with the experimental spectrum, the computed UV-Vis absorption spectrum helps recognize potential excitation wavelengths for irradiating a solvated caffeine sample in RR spectroscopy (see below). Multiscale methodologies have also been employed by Skarmoutsos et al [66] to calculate absorption and emission spectra of caffeine in aqueous solution and the authors emphasized the need for an explicit inclusion of the solvent for the correct reproduction of the emission spectrum.…”