Polarizability−Hyperpolarizability Influences upon Solvatochromism in Polychloroalkane and Polychloroalkene Media

Abstract

Molecular dipole moments for 24 haloalkanes were calculated from the solvatochromic responses of three well-established Kamlet-Taft probes. For polychloroalkanes, a simple MO model requires that the apparent dipole moment (µ i ) of the solvent be resolved into contributory terms assigned to an unperturbed dipolar component (µ i 0 ) and the composite polarizability-hyperpolarizabilities of the solvent species. The first term is related to the Kamlet-Taft π* number and the second to the Onsager reaction field parameter O(n 2 ) in the index of refraction. An approximately constant contribution from O(n 2 ) for most of the polychloroalkanes investigated, including three weak hydrogen bond donors (HBD), is in contrast to the regular trends in polarizability for the substituted benzenes accompanying changes in structure.

Influence of the Dielectric Medium on the Carbonyl Infrared Absorption Peak of Acetylferrocene

“…On the other hand, when the inductive polarization (or polarizability) of solvent is considered as dominant parameter, a completely scattered distribution of values without discernible pattern was observed in this work (graph omitted). This behavior coincides with the reported by others authors, and is consistent with a possible coupling between the dipolarity-polarizability influences in the reaction field [ 4 , 9 , 27 , 49 , 53 , 54 , 55 , 56 , 57 , 58 , 59 ]. It is noteworthy that this coupling differs among the specific f(µ, n 2 ) statements, for example, Brady-Carr [ 9 ], Marcus [ 51 ] and McRae [ 50 ] models are based on the distortional component acting in opposition to the orientational influence of the solvent and therefore the dipolar reaction field component is formally equivalent to an effective dipolar permittivity, ε , implicitly defined by eq.…”

“…This approximation is very reasonable since the polarizability-hyperpolarizability contribution was as much as 50% correction in polychloroalkanes and 30% for aromatic solvents to the components in the reaction field functions in solvatochromic effects studies [ 4 , 9 ]. For the 24 solvents in this study, the mean L ( n 2 ) of 0.212 was taken as polarizability-hyperpolarizability correction term as proposed by Kolling, and the London-Onsager function becomes L *( n 2 ) = L ( n 2 ) + 0.212 for aromatic, pseudoaromatic and polychloroalkane solvents [ 27 ]. With these alternative values for cross-term function a new trend is obtained [ 4 ].…”

“…Consequently, there is considerable interest in the study of solvent-induced perturbations on characteristic infrared absorption peaks and linear and nonlinear optical properties of organic compounds [ 1 , 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 ]. In effect, a number of semiempirical solvatochromic parameters representing “solvent polarity” have been applied to the quantification of medium effects on these properties [ 13 , 27 , 28 ]. It is known that vibrational frequencies for a molecule dissolved in a liquid depend principally on the dielectric nature of medium (solvent polarity-dipolarity) when specific local interactions are absent [ 1 , 3 , 4 , 23 , 27 ].…”

“…In effect, a number of semiempirical solvatochromic parameters representing “solvent polarity” have been applied to the quantification of medium effects on these properties [ 13 , 27 , 28 ]. It is known that vibrational frequencies for a molecule dissolved in a liquid depend principally on the dielectric nature of medium (solvent polarity-dipolarity) when specific local interactions are absent [ 1 , 3 , 4 , 23 , 27 ]. It was shown for solute molecules having large permanent dipole moments, that the solvent effect can be explained well by the Onsager reaction field model [ 16 , 24 ].…”

Characterization of solvent mixtures: preferential solvation of chemical probes in binary solvent mixtures of polar hydrogen-bond acceptor solvents with polychlorinated co-solvents

“…Moreover, the polarizability/hyperpolarizability characteristics can play a major role in the solvatochromic behavior of polar solutes for these highly polarizable co-solvent species. 17 The plots of the averaged p* values which, in our opinion, measure the property in a more useful manner for its application to any other similar solute as functions of the solvent composition, are presented in Fig. 1 for co-solvents CHCl 3 and CH 2 Cl 2 (including the values for the pure solvents determined from the same indicators).…”