Quantum-Chemical and Solvatochromic analysis of solvent effects on the Electronic Absorption Spectra of Some Benzodiazepine Derivatives

Subject Areas : Journal of Physical & Theoretical Chemistry

Sikiru Ahmed ¹ , Banjo Semire ² , Abideen Adeogun ³

1 - Department of Chemical Sciences, Kwara State University, Malete. Nigeria.
2 - Department of Pure and Applied Chemistry, Ladoke Akintola University of Technology, Ogbomosho, Nigeria
3 - Federal University of Agriculture, Abeokuta. Nigeria

Received: 2018-04-07 Accepted : 2018-05-28 Published : 2018-01-01

Keywords: Solvatochromic, Linear solvation energy, Benzodiazepine, Frontier orbital calculations, solvent polarity,

Abstract :

ABSTRACT The solvatochromic behaviour of two ketonic derivatives of benzodiazepine namely 7-chloro-1-methyl-5-phenyl-1,5-benzodiazepine-2,4-dione (Clobazam®) and 5,(2-chlorophenyl)-7-nitro-2,3-dihydro-1,4-benzodiazepine-2-one (Clonazepam®) were analysed in some selected solvents of different polarities using UV-Visible spectroscopy and DFT computational techniques. The solute-solvent interactions were evaluated by means of Kamlet-Taft’s Linear Solvation Energy Relationship (LSER) concept. The results show that electronic absorption properties of the compounds depend on the solvent polarity and both specific and non-specific interactions between solute and solvent. Also, the spectral properties show satisfactory correlation with solvatochromic parameters (α, β and π). The plot of ῡmax calculated against ῡmax observed in the representative solvents gives a good linear regression value of R2=0.998.The results of Frontier Orbital calculations showing the differences between HOMO and LUMO of the ground states and various excited states of Clobazam® and Clonazepam® are -5.15eV and -4.20eV respectively and both are in good agreement with the most important transitions observed in the two compounds.