Hydrogen Bond Acceptor Basicity Research Articles

Inhibition of thrombin by functionalized C60 nanoparticles revealed via in vitro assays and in silico studies

The studies on the human toxicity of nanoparticles (NPs) are far behind the rapid development of engineered functionalized NPs. Fullerene has been widely used as drug carrier skeleton due to its reported low risk. However, different from other kinds of NPs, fullerene-based NPs (C60 NPs) have been found to have an anticoagulation effect, although the potential target is still unknown. In the study, both experimental and computational methods were adopted to gain mechanistic insight into the modulation of thrombin activity by nine kinds of C60 NPs with diverse surface chemistry properties. In vitro enzyme activity assays showed that all tested surface-modified C60 NPs exhibited thrombin inhibition ability. Kinetic studies coupled with competitive testing using 3 known inhibitors indicated that six of the C60 NPs, of greater hydrophobicity and hydrogen bond (HB) donor acidity or acceptor basicity, acted as competitive inhibitors of thrombin by directly interacting with the active site of thrombin. A simple quantitative nanostructure-activity relationship model relating the surface substituent properties to the inhibition potential was then established for the six competitive inhibitors. Molecular docking analysis revealed that the intermolecular HB interactions were important for the specific binding of C60 NPs to the active site canyon, while the additional stability provided by the surface groups through van der Waals interaction also play a key role in the thrombin binding affinity of the NPs. Our results suggest that thrombin is a possible target of the surface-functionalized C60 NPs relevant to their anticoagulation effect.

Solubilities of formononetin and daidzein in organic solvents: Effect of molecular structure and interaction on solvation process

Abstract The solubilities of formononetin and daidzein in methanol, ethanol, n-propanol, isopropanol and acetone were measured by a static equilibrium method at temperatures range from 293.2 to 323.2 K. The solubilities of formononetin and daidzein increased with rising temperature. At a given temperature, the solubility expressed in mole fraction was recorded highest in acetone (e. g., 5.2735 × 10–4 for formononetin and 7.4678 × 10–4 for daidzein at T = 293.2 K, respectively.) followed by n-propanol, isopropanol , ethanol, and methanol, and the solubility in different solvents mainly depended on the polarity and hydrogen-bond acceptor (HBA) basicity of the solvents. Moreover, the experimental solubility data in all solvents could be reasonably correlated by ideal model, the modified Apelblat equation, λh equation and van't Hoff equation (the relative average deviations (RAD)were all

Spectroscopic behavior and equilibrium studies of some metallocephalosporins

The dissociation constants of cephradine, cefepime were evaluated at room temperature by spectrophotometric and potentiometric measurements. Also, the dissociation constants of their complexes with iron (III) nickel (II) and copper (II) in the presence of water and different percentages of ethanol–water media were calculated potentiometry. Regression analysis is applied for correlating the different parameters based on an equation that relates the wavenumbers of the absorption band maxima (υmax) to the solvent parameters; refractive index (n), dielectric constant (D), empirical Kamlet–Taft solvent parameters, π*(dipolarity/polarizability), α (solvent hydrogen-bond donor acidity) and β (solvent hydrogen-bond acceptor basicity) by using the SPSS program. The results help to assign the solute-solvent interactions and the solvatochromic potential of the investigated compounds.

The conformational analysis of push-pull enaminones using FTIR and NMR spectroscopy, and quantum chemical calculations. VI. β−N−Methyl-aminovinyl trifluoromethyl ketone and α−methyl−β−N−methylaminovinyl trifluoromethyl ketone

X-Ray analysis, NMR and IR Fourier spectra of two enaminoketones 4-(N-methylamino)-1,1,1-trifluorobut-3-en-2-one F3CCOCHCHNH(CH3) (1) 4-(N-methylamino)-1,1,1-trifluoro-3-methylbut-3-en-2-one F3CCOC(CH3)CHNH(CH3) (2) were studied in solid state and solutions. It was shown that the substitution of proton at α-position of vinyl moiety with methyl group changes significantly electronic and spatial structure of enaminoketone. In solid state enaminoketone 1 is found to be exclusively as Z-s-Z-ap isomer with intramolecular hydrogen bond. At the same time molecules of enaminoketone 2 have E-s-E-ap stereoisomeric structure forming dimers due to intermolecular NH⋯OC hydrogen bonds. Exposure of Ar-matrix isolated 1 to UV-radiation results in appearance of various E forms with free methylamino- and hydroxy groups. The same effect was observed for 2 in solutions in CCl4 under addition of polar HMPA or DMSO during spontaneous E ⇌ Z isomerization. For enaminoketone 1 under similar conditions we observed reverse process of Z ⇌ E isomerization, E stereoisomeric forms with hydroxy group being trace quantity only.Study of solvent influence on FTIR spectra revealed that introduction of methyl group as substituent at α-position of vinyl moiety increases electron population of CO double bond. Consequently, in contrast with enaminoketone 1 where the main contribution to the ν˜ (CO) band shift to lower wavenumbers in all three stereoisomeric structures makes solvent polarity/polarizability term (π*), influence of solvent's hydrogen bond acceptor (HBA) basicity (β) on ν˜ (CO) band shift of 2 predominates in the E-s-Z-ap and Z-s-Z-ap isomers. Similarly to enaminoketone 1, negative shift of the ν˜ (CC) band to lower wavenumbers occurs due to hydrogen bond formation between π system of vinyl moiety and hydrogen bond donor solvents in all stereoisomeric forms of enaminoketone 2.

Solvatochromic Parameters and Preferential Solvation Behavior for Binary Mixtures of 1,3-Dialkylimidazolium Ionic Liquids with Water

Binary mixtures of 1,3-dialkylimidazolium based ionic liquids (ILs) and water were selected as solvent systems to investigate the solute-solvent and solvent-solvent interactions on the preferential solvation of solvatochromic indicators at 25 °C. Empirical solvatochromic parameters, dipolarity/polarizability (π*), hydrogen-bond donor acidity (α), hydrogen-bond acceptor basicity (β), and Reichardt's polarity parameters (ENT) were measured from the ultraviolet-visible spectral shifts of 4-nitroaniline, 4-nitroanisole, and Reichardt's dye. The solvent properties of the IL-water mixtures were found to be influenced by IL type and IL mole fraction (xIL). All these studied systems showed the non-ideal behavior. The maximum deviation to ideality for the solvatochromic parameters can be obtained in the xIL range from 0.1 to 0.3. For most of the binary mixtures, the π* values showed the synergistic effects instead of the ENT, α and β values. The observed synergy extent was dependent on the studied systems, such as the dye indicator and IL type. A preferential solvation model was utilized to gather information on the molecular interactions in the mixtures. The dye indicator was preferentially solvated on the following trend: IL>IL-water complex>water.

Why physicochemical properties of aqueous solutions of various compounds are linearly interrelated

Analysis of physicochemical properties, such as water activity, osmotic coefficients, surface tension, viscosity, and relative permittivity, of aqueous solutions of different inorganic salts, organic compounds, and polymers shows that these properties are linearly interrelated and this interrelationship may be described as: Yi1(ci1)=k1+k2Yi2(ci2)+k3Yi3(ci3), where Yi1(ci1), Yi2(ci2), and Yi3(ci3) are properties of aqueous solutions of individual compounds 1, 2, and 3 at the same ith concentration i of each compound (ci1=ci2 = ci3); k1, k2, and k3 are constants. The relationship holds for various concentrations of compounds provided properties of aqueous solutions of the individual compounds are compared at the same concentration of each compound. Similar interrelationships are established also between different properties of aqueous solutions of any given compound. It is suggested that the reason for these relationships is that all physicochemical properties of aqueous solutions of any compound display different aspects and peculiarities of intermolecular water-water interactions affected by the presence of the compound, its nature, and concentration. The different types of water-water interactions in aqueous solutions may be quantified with the solvatochromic dyes. The solvent dipolarity/polarizability, π*, hydrogen bond donor acidity, α, and hydrogen bond acceptor basicity, β of water reported previously for aqueous solutions of organic compounds and polymers as well as those obtained for solutions of inorganic salts are linearly interrelated likely due to the cooperativity of intermolecular interactions in water. It is shown that any physicochemical property of aqueous solution of a given salt, organic compound, or polymer may be described by linear combination of two solvent features, π* and α, or in some cases by a single solvent feature. This fact explains the reason for the existence of the aforementioned linear interrelationships between the physicochemical properties of aqueous solutions of different compounds.

Effects of osmolytes on solvent features of water in aqueous solutions

The solvatochromic solvent features of water (dipolarity/polarizability, π*, hydrogen bond donor acidity, α, and hydrogen bond acceptor basicity, β) of water have been determined in aqueous solutions of erythritol, glucose, inositol, sarcosine, xylitol and urea with concentrations from 0 to ~3 M and higher. The concentration effects of the osmolytes on the solvent features of water were characterized and compared with those reported previously for sorbitol, sucrose, trimethylamine N-oxide (TMAO), and trehalose. The solvent features of water in solutions of all osmolytes except TMAO and sarcosine were established to be linearly interrelated. It is shown that the concentration effects of essentially all nonionic osmolytes depend on osmolytes’ lipophilicity, molecular polarizability, and polar surface area. It is demonstrated that solubility of various compounds in aqueous solutions of glucose, sucrose, sorbitol, and urea of varied concentrations may be described in terms of solvent dipolarity/polarizability of water in these solutions. Surface tension of aqueous solutions of sucrose and sorbitol may also be described in the same terms. The relative permittivity of aqueous solutions of glucose and sucrose may be described in terms of the solvent hydrogen bond donor acidity of water. It is suggested that the effects of nonionic osmolytes on behavior of proteins and nucleic acids in aqueous media may be considered in terms of the altered solvent features of water instead of “nano-molecular crowding” effect.

Effects of low urea concentrations on protein-water interactions

Solvent properties of aqueous media (dipolarity/polarizability, hydrogen bond donor acidity, and hydrogen bond acceptor basicity) were measured in the coexisting phases of Dextran–PEG aqueous two-phase systems (ATPSs) containing .5 and 2.0 M urea. The differences between the electrostatic and hydrophobic properties of the phases in the ATPSs were quantified by analysis of partitioning of the homologous series of sodium salts of dinitrophenylated amino acids with aliphatic alkyl side chains. Furthermore, partitioning of eleven different proteins in the ATPSs was studied. The analysis of protein partition behavior in a set of ATPSs with protective osmolytes (sorbitol, sucrose, trehalose, and TMAO) at the concentration of .5 M, in osmolyte-free ATPS, and in ATPSs with .5 or 2.0 M urea in terms of the solvent properties of the phases was performed. The results show unambiguously that even at the urea concentration of .5 M, this denaturant affects partitioning of all proteins (except concanavalin A) through direct urea–protein interactions and via its effect on the solvent properties of the media. The direct urea–protein interactions seem to prevail over the urea effects on the solvent properties of water at the concentration of .5 M urea and appear to be completely dominant at 2.0 M urea concentration.

Understanding positive and negative deviations in polarity of ionic liquid mixtures by pseudo-solvent approach.

Physico-chemical properties of liquid mixtures in general display large deviations from linear behaviour, arising out of complex specific and non-specific intermolecular interactions. The polarity of liquid mixtures displaying large positive and negative deviations can be minimized and linear mixing can be achieved in liquids using a pseudo-solvent methodology. The work described herein is designed to investigate the influence of different physical parameters on the linear pseudo-solvent composition in ionic liquid mixtures. For this purpose, we have determined the deviations from linearity, ΔE values (defined as given by ) for binary mixtures of a variety of ionic liquids, including two molecular solvents, DMSO and formamide. Firstly, the investigations were carried out in three 1-butyl-3-methylimidazolium cation based aprotic ionic liquids and the roles of anionic structure and hydrogen bond acceptor basicities (β values) of the ionic liquids were determined. The influence of the cationic structure, i.e., the hydrogen bond donor acidity (α values) and non-associative nature of the ionic liquids, was determined using C2-methylated analogs, 1-butyl-2,3-dimethylimidazolium cation based ionic liquids. The role of the protic nature of ionic liquids was studied in two protic ionic liquids, viz., 1-methylimidazolium formate and 1-methylimidazolium acetate. The effects of the temperature, pseudo-solvent structure and solvatochromic probe structure on the ΔE values were also explored.

Solvatochromic parameters of imidazolium-, hydroxyammonium-, pyridinium- and phosphonium-based room temperature ionic liquids

Solvatochromic solvent parameters of different room temperature ionic liquids based on the imidazolium, hydroxyammonium, pyridinium and phosphonium cations, namely 1-butyl-3-methyl imidazolium hexafluorophosphate, 1-hexyl-3-methyl imidazolium hexafluorophosphate, 1-octyl-3-methyl imidazolium hexafluorophosphate, 1-octyl-3-methyl imidazolium tetrafluoroborate, N-octylpyridinium tetrafluoroborate, 2-hydroxyethylammonium formate, 2-hydroxypropylammonium formate, trihexyl-(tetradecyl)phosphonium chloride, trihexyl-(tetradecyl)phosphonium bromide, trihexyl-(tetradecyl)phosphonium bis(trifluoromethylsulfonyl)imide and trihexyl-(tetradecyl)phosphonium dicyanamide were determined at 25°C using UV–Vis spectroscopy. Specifically, we have measured the Kamlet–Taft parameters: α (hydrogen-bond donor acidity), β (hydrogen-bond acceptor basicity), π* (dipolarity/polarizability) and the Reichardt's normalized polarity parameter, ETN.In previous works, we employed the Solvation Parameter Model to predict the partition coefficients for compounds of biological and pharmacological interest and to elucidate the chemical interactions involved in the partition process of different probe molecules between water and different types of ionic liquids. In this work, we have used the obtained solvatochromic solvent parameters to explain and understand the relative magnitudes of the chemical interactions obtained with the solvation parameter model.

Effect of sodium chloride on solute–solvent interactions in aqueous polyethylene glycol–sodium sulfate two-phase systems

Partition behavior of eight small organic compounds and six proteins was examined in poly(ethylene glycol)-8000–sodium sulfate aqueous two-phase systems containing 0.215M NaCl and 0.5M osmolyte (sorbitol, sucrose, TMAO) and poly(ethylene glycol)-10000–sodium sulfate–0.215M NaCl system, all in 0.01M sodium phosphate buffer, pH 6.8. The differences between the solvent properties of the coexisting phases (solvent dipolarity/polarizability, hydrogen bond donor acidity, and hydrogen bond acceptor basicity) were characterized with solvatochromic dyes using the solvatochromic comparison method. Differences between the electrostatic properties of the phases were determined by analysis of partitioning of sodium salts of dinitrophenylated (DNP-) amino acids with aliphatic alkyl side-chain. The partition coefficients of all compounds examined (including proteins) were described in terms of solute–solvent interactions. The results obtained in the study show that solute–solvent interactions of nonionic organic compounds and proteins in polyethylene glycol–sodium sulfate aqueous two-phase system change in the presence of NaCl additive.

Analysis of partitioning of organic compounds and proteins in aqueous polyethylene glycol-sodium sulfate aqueous two-phase systems in terms of solute–solvent interactions

Partition behavior of nine small organic compounds and six proteins was examined in poly(ethylene glycol)-8000-sodium sulfate aqueous two-phase systems containing 0.5M osmolyte (sorbitol, sucrose, trehalose, TMAO) and poly(ethylene glycol)-10000-sodium sulfate system, all in 0.01M sodium phosphate buffer, pH 6.8. The differences between the solvent properties of the coexisting phases (solvent dipolarity/polarizability, hydrogen bond donor acidity, and hydrogen bond acceptor basicity) were characterized with solvatochromic dyes using the solvatochromic comparison method. Differences between the electrostatic properties of the phases were determined by analysis of partitioning of sodium salts of dinitrophenylated (DNP-) amino acids with aliphatic alkyl side-chain. It was found out that the partition coefficient of all compounds examined (including proteins) may be described in terms of solute–solvent interactions. The results obtained in the study show that solute–solvent interactions of nonionic organic compounds and proteins in polyethylene glycol-sodium sulfate aqueous two-phase system differ from those in polyethylene glycol-dextran system.

Solvent Properties of Water in Aqueous Solutions of Elastin-Like Polypeptide.

The phase-transition temperatures of an elastin-like polypeptide (ELP) with the (GVGVP)40 sequence and solvent dipolarity/polarizability, hydrogen-bond donor acidity, and hydrogen-bond acceptor basicity in its aqueous solutions were quantified in the absence and presence of different salts (Na2SO4, NaCl, NaClO4, and NaSCN) and various osmolytes (sucrose, sorbitol, trehalose, and trimethylamine N-oxide (TMAO)). All osmolytes decreased the ELP phase-transition temperature, whereas NaCl and Na2SO4 decreased, and NaSCN and NaClO4 increased it. The determined phase-transition temperatures may be described as a linear combination of the solvent’s dipolarity/polarizability and hydrogen-bond donor acidity. The linear relationship established for the phase-transition temperature in the presence of salts differs quantitatively from that in the presence of osmolytes, in agreement with different (direct and indirect) mechanisms of the influence of salts and osmolytes on the ELP phase-transition temperature.

Dissociation of equimolar mixtures of aqueous carboxylic acids in ionic liquids: role of specific interactions.

Hammett acidity function observes the effect of protonation/deprotonation on the optical density/absorbance of spectrophotometric indicator. In this work, the Hammett acidity, H0, of equimolar mixtures of aqueous HCOOH, CH3COOH, and CH3CH2COOH was measured in 1-methylimidazolium-, 1-methylpyrrolidinium-, and 1-methylpiperidinium-based protic ionic liquids (PILs) and 1-butyl-3-methylimidazolium-based aprotic ionic liquid (AIL) with formate (HCOO(-)) anion. Higher H0 values were observed for the equimolar mixtures of aqueous carboxylic acids in protic ionic liquids compared with those of the aprotic ionic liquid because of the involvement of the stronger specific interactions between the conjugate acid of ionic liquid and conjugate base of carboxylic acids as suggested by the hard-soft acid base (HSAB) theory. The different H0 values for the equimolar mixtures of aqueous carboxylic acids in protic and aprotic ionic liquids were noted to depend on the activation energy of proton transfer (Ea,H(+)). The higher activation energy of proton transfer was obtained in AIL, indicating lower ability to form specific interactions with solute than that of PILs. Thermodynamic parameters determined by the "indicator overlapping method" further confirmed the involvement of the secondary interactions in the dissociation of carboxylic acids. On the basis of the thermodynamic parameter values, the potential of different ionic liquids in the dissociation of carboxylic acids was observed to depend on the hydrogen bond donor acidity (α) and hydrogen bond acceptor basicity (β), characteristics of specific interactions.

Role of solvent properties of aqueous media in macromolecular crowding effects

Analysis of the macromolecular crowding effects in polymer solutions show that the excluded volume effect is not the only factor affecting the behavior of biomolecules in a crowded environment. The observed inconsistencies are commonly explained by the so-called soft interactions, such as electrostatic, hydrophobic, and van der Waals interactions, between the crowding agent and the protein, in addition to the hard nonspecific steric interactions. We suggest that the changes in the solvent properties of aqueous media induced by the crowding agents may be the root of these “soft” interactions. To check this hypothesis, the solvatochromic comparison method was used to determine the solvent dipolarity/polarizability, hydrogen-bond donor acidity, and hydrogen-bond acceptor basicity of aqueous solutions of different polymers (dextran, poly(ethylene glycol), Ficoll, Ucon, and polyvinylpyrrolidone) with the polymer concentration up to 40% typically used as crowding agents. Polymer-induced changes in these features were found to be polymer type and concentration specific, and, in case of polyethylene glycol (PEG), molecular mass specific. Similarly sized polymers PEG and Ucon producing different changes in the solvent properties of water in their solutions induced morphologically different α-synuclein aggregates. It is shown that the crowding effects of some polymers on protein refolding and stability reported in the literature can be quantitatively described in terms of the established solvent features of the media in these polymers solutions. These results indicate that the crowding agents do induce changes in solvent properties of aqueous media in crowded environment. Therefore, these changes should be taken into account for crowding effect analysis.

Solvent effects on hydrolysis and complexation of diethyltin(IV) dichloride with guanosine-5′- and inosine-5′-monophosphates in different methanol–water mixtures

The complex formation of diethyltin(IV) cation with guanosine-5′-monophosphate (GMP) and inosine-5′-monophosphate (IMP) was investigated by spectrophotometric, potentiometric, 1H NMR, and 31P NMR in the pH range 1.5–10.5 at 25 °C, constant ionic strength 0.1 mol dm−3 (NaClO4), and in different aqueous solutions of methanol. The hydrolysis of the organotin was also studied in different water–methanol mixtures. The bonding sites of the ligands were determined and ruled out purine moiety (N7 and N1 in both GMP and IMP) while a bidentated coordination of the phosphate group is concluded in both cases. Least squares regression calculations are consistent with the formation of three hydrolytic species and Et2Sn(IV)HL+, Et2Sn(IV)L, and Et2Sn(IV)H−1L−, where L2− represents the fully dissociated ligands. The protonation of GMP and IMP, hydrolysis of the organotin, and the formed complex species in different aqueous solutions of methanol were analyzed in terms of Kamlet, Abboud, and Taft (KAT) parameters. A single-parameter correlation of the formation constants versus α (hydrogen bond donor acidity), β (hydrogen bond acceptor basicity), π* (dipolarity/polarizability) are relatively poor in all solutions, but dual-parameter correlations represent significant improvements with regard to the single- and multi-parameter models. Finally, the results are discussed in terms of the effect of solvent on protonation, hydrolysis, and complexation. .

Solvation of monatomic cations by polar solvents and the mean spherical approximation

The Gibbs solvation free energy ΔGisolv for monatomic cations of alkali metals and alkaline earth metals with a charge zi in six protic and ten aprotic dipolar solvents were analyzed in terms of the simplified Fawcett’s model based on the mean spherical approximation (MSA). Excellent linear relationships between −zi2/ΔGisolv and the ion radius ri were found resulting in the determination of fdd and δs correction terms from slopes and intercepts, respectively. It was shown that the fdd term increases with a dimensionless parameter describing dipole–dipole interactions and the δs term decreases with the empirical solvent parameter β describing the hydrogen-bond acceptor basicity. The role of these terms and their mutual relations are discussed.

Protonation Constants of Uridine 5′-Monophosphate in Different Aqueous Solutions of Methanol

The protonation equilibria of uridine 5′-monophosphate disodium salt (UMP) was determined in binary solvent mixtures of water–methanol containing 0, 10, 15, 20, 25, 30, 35, 40, 45, and 50 % (v/v) methanol, using a combination of spectrophotometric and potentiometric methods at 25 °C and constant ionic strength (0.1 mol·dm−3 NaClO4). The protonation constants were analyzed using Kamlet, Abboud, and Taft parameters. A good linear correlation of the protonation constants (on the logarithmic scale) was obtained. Dual-parameter correlation of log10K versus π* (dipolarity/polarizability) and α (hydrogen-bond donor acidity), as well as π* and β (hydrogen-bond acceptor basicity), gave good results in various aqueous solutions of methanol. Finally, the results are compared with CMP, a homolog of UMP, and are discussed in terms of the effect of the solvent on the protonation constants.

The synthesis of multiphasic ionic liquid-coated Pt/Al2O3catalysts: the selective synchronous hydrogenation of CC and CO bonds and the modeling of the ionic liquid and solvent effects

Various ionic liquids (ILs) and their mixtures were coated on the Pt/Al2O3 catalyst and the resulting IL-coated catalysts were used in the synchronous hydrogenation of cyclohexene and acetone. The rate constant (k) and selectivity (S) toward CO hydrogenation were determined for several catalysts in various solvents. The solvatochromic parameters (ETN, normalized polarity parameter; π*, dipolarity–polarizability; β, hydrogen-bond acceptor basicity; α, hydrogen-bond donor acidity) were determined for the used ILs and solvents and the obtained selectivities were modeled based on the solvatochromic parameters of the IL layer and bulk solvent while using the Multiparameter Linear Regression (MLR) method for the first time. Selectivity toward the CO bond increases by increasing the percentage of 2-hydroxy ethylammonium formate (HEAF) in the IL layer and decreasing the polarity of the solvents. The single-parameter correlations of lnS versus π* presented the best correlation for the prepared catalysts in all solvents.

Solvent and Structure Effects on Electronic Absorption Spectra of the Isomeric Pyridinecarboxylic Acids

Ultraviolet absorption spectra of three isomeric pyridinecarboxylic acids (picolinic, nicotinic, and isonicotinic acids) were measured in 18 various solvents, in the wavelength range from 200 to 400 nm. In order to analyze the solvent effect on the obtained absorption maxima, the ultraviolet absorption frequencies of the electronic transitions in the carbonyl group of the examined acids were correlated using a total solvatochromic equation in the forms νmax = ν0 + sπ* + aα + bβ and νmax = ν0 + sπ* + bβ, where νmax is the absorption frequency (1/νmax), π* is a measure of the solvent polarity, α represents a scale of the solvent hydrogen bond donor acidity, and β represents a scale of the solvent hydrogen bond acceptor basicity. Correlation of the spectroscopic data was carried out by means of multiple linear regression analysis. The effects of two different solvent types on the ultraviolet absorption maxima of the examined acids were compared and discussed.