Abstract
Due to the presence of the carbonyl and imide groups in the structure of 5,5-diphenylhydantoin (DPH), the possibility for this com- pound to be involved in hydrogen bonding intermolecular interactions is obvious. Even though such interactions are presumably responsible for the mechanism of action of this drug, however, to the best of our knowledge, the self-hydrogen bonding interactions between the DPH monomers have not been addressed till now. Furthermore, studies reporting on the spectroscopic characteristics of this molecule are scarcely reported in the literature. Here we report on the possible dimers of DPH, investigated by quantum chemical calculations at B3LYP/6-31+G(2d,2p) level of theory. Twelve unique DPH dimers were structurally optimized in gas-phase, as well as in ethanol and DMSO and then were used to compute the population-averaged UV-Vis and NMR spectra using Boltzmann statistics. UV-Vis and NMR techniques were employed to assess experimentally the spectroscopical response of this compound. DFT calculations are also used to investigate the structural transformations between the solid and liquid phase, as well as for describing the electronic transitions and for the assignment of NMR spectra of DPH.
Highlights
P HENYTOIN (DPH), with the IUPAC name 5,5-diphenylimidazolidine-2,4-dione and its general chemical formula C15H12N2O2, is the oldest non-sedative antiepileptic drug[1] indicated for the treatment of epilepsy,[2] decreasing excitatory neurotransmission and enhancing γ-aminobutyric acid - mediated inhibition
For conformer A, the left (C8-C9) ring is almost coplanar with the C4-C5 bond of the hydantoin unit, while the second phenyl ring (C14-C15) is approximately coplanar with the C5-N1 bond
Calculated relative ZPE-corrected energies for the DPH dimers show that the same two dimers (2AA and 2AB) are most stable in gas-phase and in solution, as well, but an important change in relative stabilities is noted for the remaining set of 10 dimers
Summary
P HENYTOIN (DPH), with the IUPAC name 5,5-diphenylimidazolidine-2,4-dione (see Figure 1) and its general chemical formula C15H12N2O2, is the oldest non-sedative antiepileptic drug[1] indicated for the treatment of epilepsy,[2] decreasing excitatory neurotransmission and enhancing γ-aminobutyric acid - mediated inhibition. We shall first briefly discuss the structural characteristics of the monomer for which geometrical parameters have been reported by Camerman et al.[1] and discussed by Tamir et al.[22] As seen, for the gas-phase molecule, the calculated angles which define the relative orientation of the two phenyl rings with respect to the hydantoin unit (Φ1 = C4C5C8C9, Φ2 = C4C5C14C19) are in qualitative agreement with the experimental data, as already observed by Tamir et al.[22] Even a quantitative agreement is observed for Φ2, while Φ1 is slightly worse reproduced.
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