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The structure and equilibrium of chromate, bichromate and dichromate in ambient aqueous solutions was investigated by both IR and X-ray absorption fine structure (XAFS) spectroscopy. The XAFS results confirm the IR band assignment for both the bi- and dichromate species by showing that the first-shell structure around the central chrome atom is nearly identical for the bi- and dichromate molecular ions.

X-ray absorption fine structure technique has been used to measure the coordination structure of Ni (super)2+ in water at temperatures up to 525 degrees Celsius. Experimental findings have been verified by means of molecular dynamics simulation.

Ethanol and methanol are likely substitutes of water as supercritical solvents. Scientific investigations examining the chemical shift and hydrogen bonding in methanol and ethanol were reviewed. Nuclear magnetic resonance spectroscopy, X-ray diffraction, infrared spectroscopy and other analytical techniques were utilized. The chemical structure of the alcohols upon dilution in an inert solvent were further analyzed. The findings demonstrate that temperature and pressure influence the chemical shift in both alcohols.

The pattern of proton nuclear magnetic resonance chemical shifts that were induced by hydrogen bond formation in water was analyzed to determine the molecular characteristics of hydrogen bonds in supercritical water. Analysis of the proton spectra of water indicated the role of temperature and density in inducing changes in hydrogen bonding. However, non-hydrogen bonding solute molecules exhibited constant chemical shift patterns in supercritical water.

The pulsed EPR technique of double electron electron resonance (DEER) is used for probing the distribution of intramolecular end-to-end distances. The results have shown that porphyrin-based molecular wires are shape-persistent, but their shapes can be deformed by binding to multivalent ligands.

Ultrafast transient photoluminescence spectroscopy was used to study the effect of nuclear geometric relaxation on the extent of the excited-state electronic delocalization in conjugated zinc porphyrin oligomers. The results showed that light absorption generates an excited state that is initially strongly delocalized along the oligomer but contracts rapidly following vibrational relaxation of the nuclei along C-C stretch coordinate on the subpicosecond time scale.

The synthesis and characterization of a series of porphyrin oligomers, bearing terminal thioacetates to promote attachment to gold, are described. The ultralow attenuation factors for porphyrin oligomers have shown that the electronic coupling between the contacts or terminal groups and the bridge is vital for the overall junction transmission.

The structure and speciation of bichromate, dichromate and chromate are analyzed at temperature upto 400 degree Celsius by means of infrared (IR) and X-ray absorption fine structure (XAFS) spectroscopy. Structural studies presented similar first-shell structure around the central chrome atom with equal Cr-O bond distance of three species with increasing temperature, whereas the chemical equilibria revealed thermodynamically more favorable conditions for bichromates at high temperature under acidic and near-neutral pH change than the dichromate species.

The colligative property freezing point depression is evaluated as a means for estimating the extent of aggregation for solutions of poly(ethylene oxide) alcohol (C10E6) nonionic surfactant in cyclohexane. Combined with additional measurements of self-diffusion coefficients, it is shown that both unaggregated C10E6 as well as reverse micelles are significantly present for the entire range of measured C10E6 concentration (0.048-2.35 mol kg-1). A change in speciation near 0.2 mol kg-1 is indicated by the results from both freezing point depression and self-diffusion coefficient measurements. It is shown that average reverse micelle radii and aggregation numbers obtained from the ratio of solvent and C10E6 self-diffusion coefficients are consistent with prior reported results. However, unreasonably small radii for the reverse micelles as well as for the cyclohexane were obtained from analysis of the results by the Stokes-Einstein equation using additional measured solution viscosities. The concentration of reverse micelles and unaggregated C10E6 was calculated from the freezing point depression results using the aggregation numbers obtained from ratio of self-diffusion coefficients. These concentrations indicate that the reverse micelles become smaller in average size and increase in number with increasing temperature without an increase in unaggregated C10E6. [ABSTRACT FROM AUTHOR]

The article presents a study and a quantitative analysis of nail polish remover using a nuclear magnetic resonance spectroscopy. The experiment was done by a group of students who used the method of standard addition, instead of internal standard, for the analytical procedure. The analytes of the study were ethyl acetate, 2-propanol, and acetone. Description and discussion of the experiment undertaken are provided in the article. Technical and logistical details are also offered along with the results of the study.

The article cites an experiment which involves calibration of the maximum magnetic field gradient strength through obtaining a series of projection images from several phantom objects as a function of applied field gradient strength to illustrate magnetic resonance imaging (MRI). A regular nuclear magnetic resonance (NMR) spectrum without gradients has been required to determine the effect of the gradients. From the same sample, an application of the magnetic field gradient gradient is also considered as part of the pulse program. The authors also shed light on the effect of linear gradients in NMR spectroscopy.

The application of supercritical (sc) fluid technology requires a thorough understanding of thermodynamic phase behavior. Therefore, an experiment in the physical chemistry laboratory that allows direct control and visual observation of P-V-T phase behavior has educational value for students. Students develop an experience-based understanding of how phase behavior can be manipulated. Laboratory experiments involving sc fluids also provide valuable training for students concerning the proper and safe handling of compressed fluids.

The objective of this article is to communicate and discuss a classroom exercise that engages students as a team to develop an intuitive understanding of the P- V- T phase behavior of a pure fluid. The classroom exercise requires the availability of four one-half hour periods. Since the exercise draws on the students' visualization and imagination skills, each period is actually a rather intense experience and should probably not exceed the half-hour period by too much. The author hopes to have stimulated the reader to further think about how to best confront the students with this challenging thermodynamic subject and how to best guide them through the learning process.

The article offers information about the experiment that incorporates nuclear magnetic resonance spectroscopy for measuring ternary phase diagrams. Prior to the formulation of this experiment was the growing need to additionally incorporate experiments that employ modern experimental techniques in the area of spectroscopy. In order keep the viability of the ternary phase diagram experiments, modifications were made to promote more safety. This experiment is a modification which employ the Hydrogen Nuclear Magnetic Resonance Spectroscopy in the ternary phase diagram experiment. This experiment supplements general phase behavior discussions in the undergraduate curriculum of physical chemistry.

Mutations in spike (S) protein epitopes allow SARS-CoV-2 variants to evade antibody responses induced by infection and/or vaccination. In contrast, mutations in glycosylation sites across SARS-CoV-2 variants are very rare, making glycans a potential robust target for developing antivirals. However, this target has not been adequately exploited for SARS-CoV-2, mostly due to intrinsically weak monovalent protein-glycan interactions. We hypothesize that polyvalent nano-lectins with flexibly linked carbohydrate recognition domains (CRDs) can adjust their relative positions and bind multivalently to S protein glycans, potentially exerting potent antiviral activity. Herein, we displayed the CRDs of DC-SIGN, a dendritic cell lectin known to bind to diverse viruses, polyvalently onto 13 nm gold nanoparticles (named G13-CRD). G13-CRD bound strongly and specifically to target glycan-coated quantum dots with sub-nM K d . Moreover, G13-CRD neutralized particles pseudotyped with the S proteins of Wuhan Hu-1, B.1, Delta variant and Omicron subvariant BA.1 with low nM EC 50 . In contrast, natural tetrameric DC-SIGN and its G13 conjugate were ineffective. Further, G13-CRD potently inhibited authentic SARS-CoV-2 B.1 and BA.1, with <10 pM and <10 nM EC 50 , respectively. These results identify G13-CRD as the 1st polyvalent nano-lectin with broad activity against SARS-CoV-2 variants that merits further exploration as a novel approach to antiviral therapy., Competing Interests: The authors declare no competing financial interest., (© 2023 The Authors. Published by American Chemical Society.)

An experimental study is presented for the reverse micellar system of 15% by mass polydisperse hexaethylene glycol monodecylether (C 10 E 6 ) in cyclohexane with varying amounts of added water up to 4% by mass. Measurements of viscosity and self-diffusion coefficients were taken as a function of temperature between 10 and 45 °C at varying sample water loads but fixed C 10 E 6 /cyclohexane composition. The results were used to inspect the validity of the Stokes-Einstein equation for this system. Unreasonably small reverse average micelle radii and aggregation numbers were obtained with the Stokes-Einstein equation, but reasonable values for these quantities were obtained using the ratio of surfactant-to-cyclohexane self-diffusion coefficients. While bulk viscosity increased with increasing water load, a concurrent expected decrease of self-diffusion coefficient was only observed for the surfactant and water but not for cyclohexane, which showed independence of water load. Moreover, a spread of self-diffusion coefficients was observed for the protons associated with the ethylene oxide repeat unit in samples with polydisperse C 10 E 6 but not in a sample with monodisperse C 10 E 6 . These findings were interpreted by the presence of reverse micelle to reverse micelle hopping motions that with higher water load become increasingly selective toward C 10 E 6 molecules with short ethylene oxide repeat units, while those with long ethylene oxide repeat units remain trapped within the reverse micelle because of the increased hydrogen bonding interactions with the water inside the growing core of the reverse micelle. Despite the observed breakdown of the Stokes-Einstein equation, the temperature dependence of the viscosities and self-diffusion coefficients was found to follow Arrhenius behavior over the investigated range of temperatures.

The radical cations of a family of π-conjugated porphyrin arrays have been investigated: linear chains of N = 1-6 porphyrins, a 6-porphyrin nanoring and a 12-porphyrin nanotube. The radical cations were generated in solution by chemical and electrochemical oxidation, and probed by vis-NIR-IR and EPR spectroscopies. The cations exhibit strong NIR bands at ∼1000 nm and 2000-5000 nm, which shift to longer wavelength with increasing oligomer length. Analysis of the NIR and IR spectra indicates that the polaron is delocalized over 2-3 porphyrin units in the linear oligomers. Some of the IR vibrational bands are strongly intensified on oxidation, and Fano-type antiresonances are observed when activated vibrations overlap with electronic transitions. The solution-phase EPR spectra of the radical cations have Gaussian lineshapes with linewidths proportional to N -0.5 , demonstrating that at room temperature the spin hops rapidly over the whole chain on the time scale of the hyperfine coupling (ca. 100 ns). Direct measurement of the hyperfine couplings through electron-nuclear double resonance (ENDOR) in frozen solution (80 K) indicates distribution of the spin over 2-3 porphyrin units for all the oligomers, except the 12-porphyrin nanotube, in which the spin is spread over about 4-6 porphyrins. These experimental studies of linear and cyclic cations give a consistent picture, which is supported by DFT calculations and multiparabolic modeling with a reorganization energy of 1400-2000 cm -1 and coupling of 2000 cm -1 for charge transfer between neighboring sites, placing the system in the Robin-Day class III.

The structural and dynamic behavior of the ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C(6)mim][NTf(2)]) in chloroform has been studied by experimental measurements of (1)H and (19)F self-diffusion coefficients, viscosity, and excess molar volume in the concentration range of 0.001-1.0 mol·kg(-1) and temperatures ranging from 15 to 45 °C. Within measurement uncertainty, the (1)H and (19)F self-diffusion coefficients are identical at the same experimental conditions of concentration and temperature, indicating that even to the lowest measured concentrations the cation and anion are not completely dissociated. The combined experimental data indicates a progression from ion pairing to aggregate formation as concentration increases where at concentrations near 0.1 mol·kg(-1) aggregate formation becomes dominant. Concurrently with the formation of the IL aggregates at higher concentrations, we also observe an apparent breakdown of the validity of the Stokes-Einstein equation, which we explain by translational motion to become dominated by individual ion pairs moving rapidly between IL aggregates.

We have investigated the influence of nuclear geometric relaxation on the extent of the excited-state electronic delocalization in conjugated zinc porphyrin oligomers using ultrafast transient photoluminescence spectroscopy. By use of metal-coordinating templates that force the oligomers into specific geometries in solution we are able to distinguish clearly between relaxation effects arising from the two vibrational modes that preferentially couple to the electronic transitions in such materials, i.e., carbon-carbon bond stretches and inter-ring torsions. We find that light absorption generates an excited state that is initially strongly delocalized along the oligomer but contracts rapidly following vibrational relaxation of the nuclei along C-C stretch coordinates on the subpicosecond time scale. We are able to monitor such excitonic self-trapping effects by observing the extent to which the concomitant ultrafast rotation of the transition dipole moment is found to correlate with the degree of bending induced in the molecular backbone. We further demonstrate that interporphyrin torsional relaxation leads to a subsequent increase in the excited-state electronic delocalization on a longer time scale (approximately 100 ps). Such dynamic planarization of the molecular backbone is evident from the time-dependent increase in the overall emission intensity and red-shift in the peak emission energy that can be observed for wormlike flexible porphyrin octamers but not for torsionally rigidified cyclic or double-strand octamer complexes. These results therefore indicate that, following excitation, the initially highly delocalized excited-state wave function first contracts and then expands again along the conjugated backbone in accordance with the time periods for the vibrational modes coupled to the electronic transition.