This paper reports a methodology for analyzing the solvent effect from empirical measurements of solvent acidity (SA), basicity (SB), dipolarity (SdP), and polarizability (SP). The proposed methodology departs from the traditional single-parameter procedures for estimating nonspecific solvent effects by splitting them into a polarizability term and a dipolarity term. In this work, we examined the SA, SB, SP, and SdP values for 160 solvents, the gas phase (the absence of solvent) being the origin of these scales. As shown in this paper, this information allows one not only to accurately describe the solvent effect experienced by any solute whether polar or nonpolar and exhibiting some or no specific interaction with the solvent but also to understand the nature of the well-known solvent parameters E(T)(30), pi, S', and SPP, which are frequently used to describe the overall nonspecific contribution of solvents in terms of a single parameter. The high potential of the proposed empirical methodology is illustrated with its application to the solvatochromic analysis of the spectroscopic behavior of molecular chromophores, thus explaining, for example, the influence of solvent effects in the twist intramolecular charge transfer (TICT), the excited-state intramolecular proton transfer (ESIPT), or LASER (light amplification by stimulated emission of radiation) emissions. Also, this methodology is applied to understanding for the indole chromophore the feasible inversion of the electronic nature for the first electronic excited state due to solvent effects.

More than 100 solvents and the gas phase were used to develop a solvent dipolarity‐polarizability scale that combines the medium dipolarity and polarizability into a single parameter (SPP) calculated from the UV‐visible spectra of 2‐(dimethyl‐amino)‐7‐nitrofluorene (DMANF) and its homomorph 2‐fluoro‐7‐nitrofuorene (FNF). The proposed scale compares favourably for nonprotic solvents with existing solvent polarity scales including Kosower's Z, Dimroth and Reichardt's ET(30), Brooker's χR, Dong and Winnick's Py; Kamlet, Abboud, and Taft's π*, and Drago's S′ scale. When data are derived from electronic transitions, they provide an accurate description for the solvent effect in UV‐Vis, IR, NMR, and fluorescence spectroscopy as well as in other chemical areas including thermodynamics and kinetics.

A total of 202 organic solvents and the gas phase were placed on a solvent basicity scale for hydrogen bond acceptor based on parameter SB. The value of such a parameter can readily be determined from the UV/Vis spectrum for an appropriate acid probe (5‐nitroindoline) (NI) and its non‐acid homomorph (1‐methyl‐5‐nitroindoline) (MNI). The proposed scale can advantageously substitute the more widely used solvent scales such as Gutmann's donor number (DN), the Koppel‐Palm B(MeOD) scale, and the Taft‐Kamlet β scale. While data for the proposed scale are derived only from electronic transitions, they are accurately descriptive of solvent basicity in both spectroscopy (UV/Vis, IR and NMR) and miscellaneous chemical areas (thermodynamic, kinetics, and electrochemistry).

Binary mixtures of DMSO with nine different cosolvents were characterized in light of the pure solvent scales, using suitable probe/homomorph couples. Various physical (vapor pressure, surface tension, viscosity, and enthalpy of mixing) and spectroscopic (IR and NMR) properties of the DMSO/water mixtures are described in terms of their polarity, acidity, and basicity, and the descriptions are examined with a view to establishing their potential physical significance.

OBJECTIVE:To report a case of a patient infected with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) who acutely developed a hypokinetic-rigid syndrome.METHODS:Patient data were obtained from medical records from the “Hospital Universitario 12 de Octubre” in Madrid, Spain. [123I]-ioflupane dopamine transporter single-photon emission CT (DaT-SPECT) images were acquired 4 hours after a single dose of 185 MBq of 123I-FP-CIT. Quantitative analysis was performed using DaTQUANTTM software providing the specific binding ratio (SBR) and z-score values of the striatum.RESULTS:We report a previously healthy 58-year-old man who developed hyposmia, generalized myoclonus, fluctuating and transient changes in level of consciousness, opsoclonus and an asymmetric hypokinetic-rigid syndrome with ocular abnormalities after a severe SARS-CoV-2 infection. DaT-SPECT confirmed a bilateral decrease in presynaptic dopamine uptake asymmetrically involving both putamina. Significant improvement in the parkinsonian symptoms was observed without any specific treatment.CONCLUSION:This case study provides clinical and functional neuroimaging evidence to support that SARS-CoV-2 can gain access to the central nervous system, affecting midbrain structures and leading to neurological signs and symptoms.

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A total of 121 organic solvents were studied and classified by means of the solvatochromic comparison method of Kamlet and Taft, to give a solvent acidity scale for hydrogen-bond donor solvents based on the parameter SA. This parameter can readily be evaluated from the visible spectrum of a suitable basic probe (0-tert-butylstilbazolium betaine dye, TBSB) and its non-basic homomorph (o,o'-di-tert-butylstilbazolium betaine dye, DTBSB). The proposed scale has many advantages when compared to the more widely used acidity scales such as that based on Gutmann's acceptor number (AN) and the Taft-Kamlet c1 scale. Whilst data for the proposed scale are derived from electronic transitions only, they do provide an accurate description for solvent acidity effects in spectroscopy and other chemical areas, including thermodynamics and kinetics.The solvent in which a physicochemical process takes place is a non-inert medium that plays a major role in solution chemistry. For this reason, chemists are particularly interested in increasing the amount of available knowledge on solvent properties. Roughly, the solvent effect can be resolved into non-specific, and specific, solute/solvent interactions"].In non-specific interactions, the solvent is assumed to act as a continuous dielectric medium. The early attempts of Kirkwood[21 and Onsaged31 at modelling this type of interaction were followed by approaches, aimed at characterizing solvent polarity and polarizability by means of an appropriate empirical parameter. A variety of scales have been developed for this According to Drago et al.17], specific interactions can be described, in terms of localized donor-acceptor interactions involving specific orbitals, by using electrostatic (E) and covalent parameters (C). On the other hand, Kamlet and Taftr'l used acidlbase hydrogen bonding interactions, as represented by their parameters a and p, to describe this type of interaction.Chemists have long been confronted with the challenge to find a single quantifiable property of solvents that can be used as a general basicity or acidity indicator. In this work, we address the solvent acidity issue by using an appropriate probe-homomorph couple, the UVNis spectroscopic behaviour of which was examined in a wide variety of solvents, in order to develop a broad, empirical solvent acidity scale: the SA scale. Data from this scale are compared with reported evidence ascribed to the effect of solvent acidity, obtained not only from spectroscopy, but also from other types (kinetic and thermodynamic) of chemical data. Our results are also compared with data from some pure solvent scales including the +[141, AN[12], dXh], Acity[lsI and EE scales[16]. Results and Discussion Formulation of the SA ScaleIn previous we showed that the extremely strong negative solvatochromism of the chromophore stilbazolium betaine dye (SB), at about 6500 cmP', is a result not of a change in the non-specific effect of the solvent but rather of a change in acidity. This was by a study of the solvatochromic effect of the SB...

The absorption and emission spectroscopic properties of 6-propionyl-2-(dimethylamino)naphthalene (PRODAN) have been studied in a large number of protogenic, nonprotogenic, and amphiprotic solvents. The data obtained can be explained by the inclussion of a new term in the Lippert equation which takes into account the acidity of the solvent. This finding indicates that some precaution should be taken when using PRODAN as an indicator of the polarity of protein cavities if the environments involved include acid sites.