Structural and Vibrational Study On the Acid, Hexa-Hydrated and Anhydrous Trisodic Salts of Antiviral Drug Foscarnet

Volume 1 - Issue 3

Maximiliano A Iramain and Silvia A Brandan*

Received: May 01, 2018;   Published: May 09, 2018

DOI: 10.32474/DDIPIJ.2018.01.000114

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Abstract

The structural and vibrational properties of acid species, hexa-hydrated and anhydrous trisodic salts of antiviral drug foscarnet in gas phase and in aqueous solution have been studied in this work by using the hybrid B3LYP method with the 6-31G* and 6-311++G** basis sets. The properties in solution were carried out with the self consistent reaction force (SCRF) method by using the integral equation formalism variant polarised continuum (IEFPCM) and SD models while the complete vibrational assignments for those three species were performed in both media by using the experimental available infrared spectrum of hexa-hydrated trisodic salt and the scaled quantum mechanical force field (SQMFF) methodology. The natural bond orbital (NBO) studies suggest that the hexa-hydrated salt in solution is most stable than the anhydrous one in the same medium but in gas phases the anhydrous salt shows a higher stability in solution. The atoms in molecules (AIM) analyses have revealed the ionic characteristics of the O--- Na bonds in both salts supporting the higher stability of the hexa-hydrated salt in solution. The evaluation of the frontier orbitals show that the anhydrous salt is the most reactive species in solution, as supported by its higher solvation energy and volume variation. Apparently, the presences of phosphate group in foscarnet probably increase its activity when it is used as drug. The experimental infrared bands observed in the hexa-hydrated species at 1059 and 983 cm-1 are clearly attributed to the stretching modes of phosphate group while the strong bands at 1445 and 1333 cm-1 are associated to the stretching modes of carboxylate group. In addition, the force constants for the carboxylate and phosphate groups are reported.

Keywords: Foscarnet; Vibrational Spectra; Molecular Structure; Force Field; DFT Calculations

Abbrevations: SCRF: Self Consistent Reaction Force; IEFPCM: Integral Equation Formalism Variant Polarised Continuum; SQMFF: Scaled Quantum Mechanical Force Field; NBO: Natural Bond Orbital; AIM: Atoms In Molecules; HIV: Human Immunodeficiency Virus; PCM: Polarized Continuum Model; NPA: Atomic Natural Population; MK: Merz-Kollman; PED: Potential Energy Distribution Components; BO: Bond Orders; MEP: Molecular Electrostatic Potentials; AIM: Atoms in Molecules; RCPs: Ring Critical Point

Abstract| Introductiom| Methodology of calculations| Results and Discussion| Conclusions| Acknowledgement| Refernces|