Hydrogen bonding and dipolar interactions between quinolines and organic solvents. Nuclear magnetic resonance and ultraviolet-visible spectroscopic studies

Interaction energy in pairs of phthalazinium dibenzoylmethylid (PDBM)-protic solvent molecules estimated in the limits of the cell ternary solution model, by spectral means

The dipolar compound Phthalazinium-dibenzoylmethylid (PDBM) was used as spectrally active molecule in order to analyze the molecular interactions in ternary solutions containing at least one protic solvent. In PDBM+protic solvent (1)+aprotic solvent (2) ternary solutions, PDBM can be involved both in universal and specific interactions reflected in solvatochromic effects. The protic solvent (or the solvent with the higher electric permittivity) was considered as being active from the interactions point of view. The content of the first solvation sphere of the studied ylid has been established on the basis of the statistical cell model of ternary solutions. The active solvent molecules are dominant in the first solvation sphere of the PDBM molecules. The difference between the interaction energies in the PDBM-active solvent (1) and PDBM-inactive solvent (2) molecular pairs has been determined for three binary solvents water+ethanol (W+E), propionic acid+chloroform (PA+C) and octanol+1,2 dichloroethane (O+DCE). The hydrogen bond formation energy of the PDBM-protic solvent complex has been estimated in the binary solvents PA+C and O+DCE containing one protic (PA and O, respectively) and one aprotic solvent with close electro-optical parameters refractive index and electric permittivity of the components.

FT-IR study on interactions between medroxyprogesterone acetate and solvent in CHCl₃/cyclo-C6H₁₂ and CCl₄/cyclo-C6H₁₂ binary solvent systems

The intermolecular interactions between medroxyprogesterone acetate (MPA) and CHCl(3) and CCl(4) solvent in CHCl(3)/cyclo-C(6)H(12) and CCl(4)/cyclo-C(6)H(12) binary solvent systems have been studied by Fourier transform infrared spectroscopy (FT-IR). The experimental results showed that there are hydrogen bonding interactions between oxygen atoms of all carbonyl groups in MPA and hydrogen atom of CHCl(3) so as to form 1:3 complex of MPA with CHCl(3) and produce three new absorption bands at 1728.9-1736.1, 1712.7-1717.4 and 1661.9-1673.8 cm(-1), respectively. And, 1:1 complex of MPA with CCl(4) is formed in CCl(4)/cyclo-C(6)H(12) binary solvent as a result of hydrogen bonding interaction between C3 carbonyl group and empty d-orbital in chlorine atom of CCl(4) leading to producing new absorption band at 1673.2-1674.2 cm(-1). However, all free carbonyl and associated carbonyl stretching vibrations of MPA in CHCl(3)/cyclo-C(6)H(12) and CCl(4)/cyclo-C(6)H(12) binary solvent systems shift to lower wavenumbers with the increasing of volume fraction of CHCl(3) and CCl(4) in binary solvent systems owing to the dipole-dipole interaction and the dipole-induced dipole interaction between MPA and solvents.

Solvatochromism and preferential solvation of 1,4-dihydroxy-2,3-dimethyl-9,10-anthraquinone by UV-vis absorption and laser-induced fluorescence measurements

Solvation characteristics of 1,4-dihydroxy-2,3-dimethyl-9,10-anthraquinone (1) in pure and binary solvent mixtures have been studied by UV-vis absorption spectroscopy and laser-induced fluorescence techniques. The binary solvent mixtures used as CCl(4) (tetrachloromethane)-DMF (N,N-dimethylformamide), AN (acetonitrile)-DMSO (dimethylsulfoxide), CHCl(3) (chloroform)-DMSO, CHCl(3)-MeOH (methanol), and MeOH-DMSO. The longest wavelength band of 1 has been studied in pure solvents as well as in binary solvent mixtures as a function of the bulk mole fraction. The Vis absorption band maxima show an unusual blue shift with increasing solvent polarity. The emission maxima of 1 show changes with varying the pure solvents and the composition in the case of binary solvent mixtures. Non-ideal solvation characteristics are observed in all binary solvent mixtures. It has been observed that the quantity [nu (12)-(X(1)nu (1)+X(2)nu (2))] serves as a measure of the extent of preferential solvation, where nu and X are the position of band maximum in wavenumbers (cm(-1)) and the bulk mole fraction values, respectively. The preferential solvation parameters local mole fraction (X(2)(L)), solvation index (delta(s2)), and exchange constant (k(12)) are evaluated.

Solvatochromic study of 1,2-dihydroxyanthraquinone in neat and binary solvent mixtures

Preferential solvation of a solvatochromic probe has been studied in binary mixtures comprising of a non-protic and a protic solvent. The non-protic solvents employed are carbon tetrachloride (CCl(4)), acetonitrile (AcN) and N,N-dimethyl formamide (DMF) and the protic solvents are methanol (MeOH) and ethanol (EtOH). The probe molecule exhibits different spectroscopic characteristics depending upon the properties of the solubilizing media. The observed spectral features provide an indication of the microenvironment immediately surrounding the probe. Solvatochromic shifts of the ground and excited states of the probe were analysed by monitoring the charge transfer absorption band and the fluorescence emission spectra in terms of the solute-solvent and solvent-solvent interactions. Fluorescence emission spectra show the dual emission due to excited state proton transfer nature of the probe molecule. The effect of solvent and the excitation energy on dual emission are also studied. The observed magnitude of the Stokes shift in the above solvents has been used to deduce experimentally the dipole moment ratio of the probe molecule for the excited state to the ground state. The dipole moment of excited state is higher than the ground state.