Structural properties and FTIR-Raman spectra of the anti-hypertensive clonidine hydrochloride agent and their dimeric species

E. ROMANO; LILIAN DAVIES; SILVIA A. BRANDÁN

JOURNAL OF MOLECULAR STRUCTURE

ELSEVIER SCIENCE BV

Lugar: Amsterdam; Año: 2017 vol. 1133 p. 226 - 235

0022-2860

The structural and vibrational properties of the a-adrenergic agonist clonidine hydrochloride agent andtheir anionic and dimeric species were studied combining the experimental FT-IR and Raman spectra insolid phase with ab-initio calculations based on the density functional theory (DFT). All the calculationswere performed by using the hybrid B3LYP with the 6-31G* and 6-311þþG** basis sets. The structuralproperties for those species were studied employing the Natural Bond Orbital (NBO), Atoms in Moleculestheory (AIM) and frontier orbitals calculations. The complete assignments of the FTIR and Raman spectrawere performed combining the DFT calculations with the Pulay´s Scaled Quantum Mechanics Force Field(SQMFF) methodology. Very good concordances between the theoretical and experimental spectra werefound. In addition, the force constants for those three species were computed and compared with thevalues reported for similar antihypertensive agents. The ionic nature of the H/Cl bond and the highvalue of the LP(1)N4 / LP*(1)H18 charge transfer could explain the high reactivity of clonidine hydrochloridein relation to other antihypertensive agent and the strong shifthing of the band assigned to theNeH stretching mode linked to the HeCl bond toward lower wavenumbers.