Theoretical studies of uracil–(H2O)n (n=1–7) clusters by ab initio and ABEEMσπ/MM fluctuating charge model

Uracil–water interaction revisited – in search of single H-bonded secondary minima

“…As predicted in all previous studies, 21,23,24,49,57,58,66 the present study also found that UW-4 is the least stable structure, stabilized by the O⋯HO w hydrogen bond (for the corresponding structures see Fig. S7, ESI†).…”

“…These complexes have already been reported in the literature. 21,23,24,26,27,48–50,57–65 However, information on the single H-bonded (either O⋯HO w or NH⋯O w ), most likely local minimum structures of uracil–water, is not available in the H-bond literature. Ramondo and co-workers 27 reported IR spectra of four double H-bonded UW structures.…”

Clustering of Uracil Molecules on Ice Nanoparticles

“…Using microwave and infrared laser spectroscopy only the keto-form of uracil was observed in the U·H 2 O complex. Several computational studies of small U·(H 2 O) n complexes − have reported on the character of these clusters up to the formation of the first hydration shell around uracil. The relative stabilities of keto and enol forms in the water environment have been studied as well. , The dissociation energies of water molecule bound to N1 and O2, O2 and N3, and N3 and O4 atoms (for numbering see Figure ) were estimated in the range of 7–9 kcal/mol .…”

Is Uracil Aromatic? The Enthalpies of Hydrogenation in the Gaseous and Crystalline Phases, and in Aqueous Solution, as Tools to Obtain an Answer

“…To verify the results obtained with the PCM model, four explicit water molecules were also added to the same relative positions of both uracil and 5,6-dihydrouracil. These molecules were placed considering the most stable conformation of previous literature studies. , According to the conformational analysis of Bachrach and Dzierlenga, four water molecules should be enough, since with a number of water molecules beyond this, the extra water molecule interacts only with other water molecules and do not form any extra hydrogen bonds with uracil. As a result, the effect on the enthalpy of hydrogenation of a higher number of explicit water molecules should be negligible.…”

“…The computations will be extended to the aqueous solution, where the zwitterionic resonance forms are expected to play a more important role and, hence, influence the aromaticity of uracil. Other authors have investigated the role of solvation on the physical–chemical properties of uracil such as hydrogen bond patterns, − tautomeric equilibrium, , charge transfer, electron affinities, − acidity, , and electronic spectra . In this work, implicit, explicit, and hybrid solvation methods will be used to evaluate the influence of polarity effects and hydrogen bonds on the aromaticity of uracil.…”