Correction: Zinc(II) hydration in aqueous solution. A Raman spectroscopic investigation and an ab initio molecular orbital study.

Correction for 'Zinc(II) hydration in aqueous solution. A Raman spectroscopic investigation and an ab initio molecular orbital study' by Wolfram W. Rudolph et al., Phys. Chem. Chem. Phys., 1999, 1, 4583-4593, https://doi.org/10.1039/A904051J.

Comparison of VITEK 2, MALDI-TOF MS, 16S rRNA gene sequencing, and whole-genome sequencing for identification of Roseomonas mucosa.

The bacterial species Roseomonas mucosa is pathogenic in humans, and although it is rarely detected during routine diagnostics, it is becoming increasingly important clinically. For a long time, R. mucosa was regarded as a classic environmental bacterium. Recent studies, however, revealed that it is part of the physiological human skin flora and mainly affects immunocompromised patients. Furthermore, the use of catheter systems may increase the risk of contracting R. mucosa infections. The bacterium has been linked to severe infections, such as bacteraemia, osteomyelitis and cellulitis. Therefore, it is important to discern the best method of identifying R. mucosa in routine laboratory testing. To facilitate this testing, we compared three suitable methods for routine bacterial identification in the laboratory: VITEK 2, MALDI-TOF MS and 16S rRNA gene sequencing. Additionally, we conducted whole-genome sequencing (WGS) and calculated the average nucleotide identity (ANI). ANI is seen as the gold standard of strain identification; therefore, we decided to use it as a reference method. Both MALDI-TOF MS and 16S rRNA gene sequencing confidently identified the species. However, when using the VITEK 2 technique, isolates were misidentified as Roseomonas gilardii, Rhizobium radiobacter, or Sphingomonas paucimobilis. When conducting WGS and determining the ANI, it became obvious that one isolate belonged to the species R. gilardii rather than R. mucosa. Therefore (although not yet applicable in routine diagnostics), we suggest that WGS is presently the most appropriate technique to reliably identify Roseomonas mucosa. However, after expanding the Biotyper database, MALDI-TOF MS could also be an applicable method.

Detection of Robinsoniella peoriensis in multiple bone samples of a trauma patient.

We report a case of a 58-year-old male patient who underwent several surgeries following an accident. The bacterium Robinsoniella peoriensis was detected independently in multiple samples from both the right talus and tibia. The bacterium could only be identified using 16S rRNA gene sequencing.

On the Hydration of Heavy Rare Earth Ions: Ho3+, Er3+, Tm3+, Yb3+ and Lu3+-A Raman Study.

Raman spectra of aqueous Ho3+, Er3+, Tm3+, Yb3+, and Lu3+-perchlorate solutions were measured over a large wavenumber range from 50-4180 cm-1. In the low wavenumber range (terahertz region), strongly polarized Raman bands were detected at 387 cm-1, 389 cm-1, 391 cm-1, 394 cm-1, and 396 cm-1, respectively, which are fairly broad (full widths at half height at ~52 cm-1). These isotropic Raman bands were assigned to the breathing modes, ν1 Ln-O of the heavy rare earth (HRE) octaaqua ions, [Ln(H2O)8]3+. The strong polarization of these bands (depolarization degree ~0) reveals their totally symmetric character. The vibrational isotope effect was measured in Yb(ClO4)3 solutions in H2O and D2O and the shift of the ν1 mode in changing from H2O to D2O further supports the character of the band. The Ln-O bond distances of these HRE ions (Ho3+, Er3+, Tm3+, Yb3+, and Lu3+) follow the order of Ho-O > Er-O > Tm-O > Yb-O > Lu-O which correlates inversely with the band positions of the breathing modes of their corresponding octaaqua ions [Ln(OH2)8]3+. Furthermore, the force constants, kLn-O, were calculated for these symmetric stretching modes. Ytterbium perchlorate solutions were measured over a broad concentration range, from 0.240 mol·L-1 to 2.423 mol·L-1, and it was shown that with increasing solute concentration outer-sphere ion pairs and contact ion pairs were formed. At the dilute solution state (~0.3 mol·L-1), the fully hydrated ions [Yb(H2O)8]3+ exist, while at higher concentrations (CT > 2 mol·L-1), ion pairs are formed. The concentration behavior of Yb(ClO4)3 (aq) shows similar behavior to the one observed for La(ClO4)3(aq), Ce(ClO4)3(aq) and Lu(ClO4)3(aq) solutions. In ytterbium chloride solutions in water and heavy water, representative for the behavior of the other HRE ions, 1:1 chloro-complex formation was detected over the concentration range from 0.422-3.224 mol·L-1. The 1:1 chloro-complex in YbCl3(aq) is very weak, diminishing rapidly with dilution and vanishing at a concentration < 0.4 mol·L-1.

Hydration and Ion Pair Formation in Aqueous Lu3+- Solution.

Aqueous solutions of Lu3+- perchlorate, triflate and chloride were measured by Raman spectroscopy. A weak, isotropic mode at 396 cm-1 (full width at half height (fwhh) at 50 cm-1) was observed in perchlorate and triflate solutions. This mode was assigned to the totally symmetric stretching mode of [Lu(OH2)8]3+, ν1LuO8. In Lu(ClO4)3 solutions in heavy water, the ν1LuO8 symmetric stretch of [Lu(OD2)8]3+ appears at 376.5 cm-1. The shift confirms the theoretical isotopic effect of this mode. In the anisotropic scattering of aqueous Lu(ClO4)3, five bands of very low intensity were observed at 113 cm-1, 161.6 cm-1, 231 cm-1, 261.3 cm-1 and 344 cm-1. In LuCl3 (aq) solutions measured over a concentration range from 0.105⁻3.199 mol·L-1 a 1:1 chloro-complex was detected. Its equilibrium concentration, however, disappeared rapidly with dilution and vanished at a concentration < 0.5 mol·L-1. Quantitative Raman spectroscopy allowed the detection of the fractions of [Lu(OH2)8]3+, the fully hydrated species and the mono-chloro complex, [Lu(OH2)7Cl]2+. In a ternary LuCl3/HCl solution, a mixtrure of chloro-complex species of the type [Lu(OH2)8-nCln]+3-n (n = 1 and 2) were detected. DFT geometry optimization and frequency calculations are reported for Lu3+- water cluster in vacuo and with a polarizable dielectric continuum (PC) model including the bulk solvent implicitly. The bond distance and angle for [Lu(OH2)8]3+ within the PC are in good agreement with data from structural experiments. The DFT frequencies for the Lu-O modes of [Lu(OH2)8]3+ and its deuterated analog [Lu(OD2)8]3+ in a PC are in fair agreement with the experimental ones. The calculated hydration enthalpy of Lu3+ (aq) is slightly lower than the experimental value.

First report on sepsis caused by Porphyromonas pogonae.

We report on a 62 year old patient who developed sepsis due to an infection caused by Porphyromonas pogonae, a recently described species of the bacterial genus Porphyromonas. This is the first case of an invasive infection with this pathogen.

Design of a covalently linked human interleukin-10 fusion protein and its secretory expression in Escherichia coli.

Wild-type human interleukin-10 (hIL-10) is a non-covalent homodimer with a short half-life, thus limiting its therapeutic applications in vivo. To avoid loss of function due to dimer dissociation, we designed a synthetic hIL-10 analog by bridging both monomers via a 15 amino acid-long peptide spacer in a C-terminal to N-terminal fashion. For secretory expression in Escherichia coli, a 1156 bp fragment was generated from template vector pAZ1 by fusion PCR encoding a T7 promoter region and the signal sequence of the E. coli outer membrane protein F fused in frame to two tandem E. coli codon-optimized mature hIL-10 genes connected via a 45 nucleotide linker sequence. The construct was cloned into pUC19 for high-level expression in E. coli BL21 (DE3). The mean concentrations of hIL-10 fusion protein in the periplasm and supernatant of E. coli at 37 °C growth temperature were 130 ± 40 and 2 ± 1 ng/ml, respectively. The molecular mass of the recombinant protein was assessed via matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) analysis, indicating correct processing of the signaling sequence in E. coli. In vitro biological activity was shown by phosphorylation of signal transducer and activator of transcription protein 3 and suppression of tumor necrosis factor α secretion in lipopolysaccharide-stimulated macrophages.

Comparative Study of Different Diagnostic Routine Methods for the Identification of Acinetobacter radioresistens.

Recent publications indicate that A. radioresistens can cause infections in humans, even though it is rarely reported in routine diagnostics. However, the fact that it is infrequently detected may be explained by the misidentification of the species by conventional methods. It is also likely that A. radioresistens is not considered clinically relevant and therefore not consistently included in diagnostic results. To elucidate the medical significance of this probably clinically underestimated bacterial species, we created a well-documented reference strain collection of 21 strains collected in routine diagnostics. For further analysis of A. radioresistens, it is essential to know which methods can be used to achieve a trustworthy identification. We, therefore, compared three methods widely used in routine diagnostics (MALDI-TOF MS, VITEK 2, and sequencing of housekeeping genes) in terms of secure and reliable identification of A. radioresistens. As reference methods, whole genome-based approaches were applied. VITEK 2 led to misidentification for four strains. However, MALDI-TOF MS and sequencing of housekeeping genes led to reliable and robust identifications.

Hydration and Ion-Pair Formation of NaNO3(aq): A Vibrational Spectroscopic and Density Functional Theory Study.

Qualitative and quantitative Raman and infrared measurements on sodium nitrate (NaNO3) solutions have been carried out over a wide concentration range (5.56 × 10-6-7.946 mol/L) in water and heavy water. The Raman spectra were measured from 4000 cm-1 to low wavenumbers at 45 cm-1. Band fit analysis on the profile of the 1047 cm-1 band, ν1(a1') NO3- measured at high resolution at 0.90 cm-1 produced a small contribution at 1027 cm-1 of the isotopomer N16O218O(aq). The effect of solute concentration on the Raman and infrared bands has been systematically recorded. Extrapolation of the experimental data resulted in values for all the nitrate bands of the "free", i.e., fully hydrated NO3-(aq). However, even in dilute solutions, the vibrational symmetry of the hydrated NO3-(aq) is broken and the antisymmetric N-O stretch, which is degenerate for the isolated anion, is split by 56 cm-1. At concentrations >2.5 mol/L, direct contact between Na+ and NO3- was observed and accompanied by large band parameter changes. DFT calculations on NO3-(H2O)n (n = 1-3) led to optimized geometries and vibrational frequencies which reproduced the measured ones within an accuracy of 1%. A hydrated gas phase species Na+(H2O)10NO3- was optimized resulting in the geometry and symmetry of the nitrate, which is bound in an antisymmetric bidentate fashion with the nitrate possessing C1. The ν1 Na+(OH2) breathing mode in aqueous solution appears at 189 cm-1, whereas in heavy water, ν1 Na+(OD2) is shifted to 175.6 cm-1 due to the isotope effect. DFT calculations on hydrated Na+(OH2)n gas phase clusters provided realistic Na+ hydrate structures with n = 4 and 5, which resembled the measured frequency of ν1 Na+ OH2 mode quite well. Quantitative Raman analysis employing the symmetric stretching band, ν1(a1') NO3-, has been carried out down to concentrations as low as 5.56 × 10-6 mol/L. The in-plane deformation mode ν4(e') in the Raman scattering at higher concentrations has been used as an indicator band for directly coordinated NO3-.

Whole-genome sequencing of a large collection of Myroides odoratimimus and Myroides odoratus isolates and antimicrobial susceptibility studies.

The genus Myroides comprises several species of Gram-negative, non-motile, and non-fermenting bacteria, which have been regarded as non-pathogenic for decades. Multiple recent reports, however, underscore the pathogenic potential that Myroides sp. possesses for humans. These bacteria seem to be resistant to a wide range of antibiotics (including ß-lactams and aminoglycosides). Therefore, treatment options are limited. Knowledge of antimicrobial resistance, however, is based on only one meaningful comprehensive study and on data published from case reports. This lack of data motivated us to test 59 strains from our Myroides collection (43 M. odoratimimus and 16 M. odoratus) for resistance against 20 commonly used antibiotics. We also performed molecular analyses to reveal whether our bacteria harbor the genus-specific M. odoratimimus metallo-ß-lactamase (MUS-1) or the M. odoratus metallo ß-lactamase (TUS-1), and other ß-lactamases, which may provide an explanation for the extended antimicrobial resistance.

Modeling Hemolytic-Uremic Syndrome: In-Depth Characterization of Distinct Murine Models Reflecting Different Features of Human Disease.

Diarrhea-positive hemolytic-uremic syndrome (HUS) is a renal disorder that results from infections with Shiga-toxin (Stx)-producing Escherichia coli. The aim of this study was to establish well-defined refined murine models of HUS that can serve as preclinical tools to elucidate molecular mechanisms of disease development. C57BL/6J mice were subjected to different doses of Stx2 purified from an E. coli O157:H7 patient isolate. Animals received 300 ng/kg Stx2 and were sacrificed on day 3 to establish an acute model with fast disease progression. Alternatively, mice received 25 ng/kg Stx2 on days 0, 3, and 6, and were sacrificed on day 7 to establish a subacute model with moderate disease progression. Indicated by a rise in hematocrit, we observed dehydration despite volume substitution in both models, which was less pronounced in mice that underwent the 7-day regime. Compared with sham-treated animals, mice subjected to Stx2 developed profound weight loss, kidney dysfunction (elevation of plasma urea, creatinine, and neutrophil gelatinase-associated lipocalin), kidney injury (tubular injury and loss of endothelial cells), thrombotic microangiopathy (arteriolar microthrombi), and hemolysis (elevation of plasma bilirubin, lactate dehydrogenase, and free hemoglobin). The degree of complement activation (C3c deposition), immune cell invasion (macrophages and T lymphocytes), apoptosis, and proliferation were significantly increased in kidneys of mice subjected to the 7-day but not in kidneys of mice subjected to the 3-day regime. However, glomerular and kidney volume remained mainly unchanged, as assessed by 3D analysis of whole mount kidneys using CD31 staining with light sheet fluorescence microscopy. Gene expression analysis of kidneys revealed a total of only 91 overlapping genes altered in both Stx2 models. In conclusion, we have developed two refined mouse models with different disease progression, both leading to hemolysis, thrombotic microangiopathy, and acute kidney dysfunction and damage as key clinical features of human HUS. While intrarenal changes (apoptosis, proliferation, complement deposition, and immune cell invasion) mainly contribute to the pathophysiology of the subacute model, prerenal pathomechanisms (hypovolemia) play a predominant role in the acute model. Both models allow the further study of the pathomechanisms of most aspects of human HUS and the testing of distinct novel treatment strategies.

Raman and infrared spectroscopic investigations on aqueous alkali metal phosphate solutions and density functional theory calculations of phosphate-water clusters.

Phosphate (PO(4)(3-)) solutions in water and heavy water have been studied by Raman and infrared spectroscopy over a broad concentration range (0.0091-5.280 mol/L) including a hydrate melt at 23 degrees C. In the low wavenumber range, spectra in R-format have been constructed and the R normalization procedure has been briefly discussed. The vibrational modes of the tetrahedral PO(4)(3-)(aq) (T(d) symmetry) have been assigned and compared to the calculated values derived from the density functional theory (DFT) method for the unhydrated PO(4)(3-)(T(d)) and phosphate-water clusters: PO(4)(3-).H(2)O (C(2v)), PO(4)(3-).2H(2)O (D(2d)), PO(4)(3-).4H(2)O (D(2d)), PO(4)(3-).6H(2)O (T(d)), and PO(4)(3-).12H(2)O (T), a cluster with a complete first hydration sphere of water molecules. A cluster with a second hydration sphere of 12 water molecules and 6 in the first sphere, PO(4)(3-).18H(2)O (T), has also been calculated. Agreement between measured and calculated vibrational modes is best in the case of the PO(4)(3-).12H(2)O cluster and the PO(4)(3-).18H(2)O cluster but far less so in the case of the unhydrated PO(4)(3-) or phosphate-water cluster with a lower number of water molecules than 12. The asymmetric, broad band shape of v(1)(a(1)) PO(4)(3-) in aqueous solutions has been measured as a function of concentration and the asymmetric and broad band shape was explained. However, the same mode in heavy water has only half the full width at half-height compared to the mode in normal water. The PO(4)(3-) is strongly hydrated in aqueous solutions. This has been verified by Raman spectroscopy comparing v(2)(H(2)O), the deformation mode of water, and the stretching modes, the v(1)OH and v(3)OH of water, in K(3)PO(4) solutions as a function of concentration and comparison with the same modes in pure water. A mode at approximately 240 cm(-1) (isotropic R spectrum) has been detected and assigned to the restricted translational mode of the strong hydrogen bonds formed between phosphate and water, P-O...HOH. In very concentrated K(3)PO(4) solutions (C(0) > or = 3.70 mol/L) and in the hydrate melt, formation of contact ion pairs (CIPs) could be detected. The phosphate in the CIPs shows a symmetry lowering of the T(d) symmetry to C(3v). In the less concentrated solutions, PO(4)(3-)(aq) solvent separated ion pairs and doubly solvent separated ion pairs exist, while in very dilute solutions fully hydrated ions are present (C(0) < or = 0.005 mol/L). Quantitative Raman measurements have been carried out to follow the hydrolysis of PO(4)(3-)(aq) over a very broad concentration range. From the hydrolysis data, the pK(3) value for H(3)PO(4) has been determined to be 12.45 at 23 degrees C.

Raman spectroscopic characterization of light rare earth ions: La3+, Ce3+, Pr3+, Nd3+ and Sm3+ - hydration and ion pair formation.

Raman spectra of aqueous La3+, Ce3+, Pr3+, Nd3+ and Sm3+ - perchlorate solutions were measured and weak strongly polarized Raman bands were detected at 343 cm-1, 344 cm-1, 347 cm-1, 352 cm-1 and 363 cm-1, respectively. The full width at half height for these bands is quite broad (∼50 cm-1) in the isotropic spectrum and the band width increases with increasing solute concentration. The polarized Raman bands were assigned to the breathing modes of the nona-aqua ions of the mentioned rare earth ions. Published structural results confirmed that these ions exist as nona-hydrates in aqueous solutions [Ln(H2O)9]3+. The Ln-O bond distances of these rare earth ions correlate well with the band positions of the nona-aqua ions [Ln(OH2)9]+3 (Ln = La3+, Ce3+, Pr3+, Nd3+ and Sm3+) and the force constants were calculated for these breathing modes. The strength of the force constants increase with decreasing the Ln-O bond distances (La-O > Ce-O > Pr-O > Nd-O > Sm-O). While the fully hydrated ions are stable in dilute perchlorate solutions (∼0.2 mol L-1), in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed (C > 1.5 mol L-1). In a hydrate melt at 161 °C of Ce(ClO4)3 plus 6H2O, the contact ion pairs are the dominate species. The Raman bands of the ligated perchlorate and the Ce-O breathing mode of the partially hydrated ion pair at 326 cm-1 were measured and characterized. In cerium chloride solutions chloro-complex formation was detected over the measured concentration range from 0.270-2.167 mol L-1. The chloro-complexes in CeCl3(aq) are weak and diminish rapidly with dilution and disappear at a concentration <0.1 mol L-1. In a CeCl3 solution, with additional HCl, a series of chloro-complex species of the type [Ce(OH2)9-nCln]+3-n (n = 1, 2) were detected.

Vibrational spectroscopic studies and density functional theory calculations of speciation in the CO2-water system.

Raman spectra of CO(2) dissolved in water and heavy water were measured at 22 degrees C, and the Fermi doublet of CO(2), normally at 1285.45 and 1388.15 cm(-1) in the gaseous state, revealed differences in normal water and heavy water, although no symmetry lowering of the hydrated CO(2) could be detected. Raman spectra of crystalline KHCO(3) and KDCO(3) were measured at 22 degrees C and compared with the infrared data from the literature. In these solids, (H(D)CO(3))(2)(2-) dimers exist and the spectra reveal strong intramolecular coupling. The vibrational data of the dimer (C(2h) symmetry) were compared with the values from density functional theory (DFT) calculations and the agreement is fair. Careful measurements were made of the Raman spectra of aqueous KHCO(3), and KDCO(3) solutions in D(2)O down to 50 cm(-1) and, in some cases, down to very low concentrations (> or =0.0026 mol/kg). In order to complement the spectroscopic assignments, infrared solution spectra were also measured. The vibrational spectra of HCO(3)(-)(aq) and DCO(3)(-)(D(2)O) were assigned, and the measured data compared well with data derived from DFT calculations. The symmetry for HCO(3)(-)(aq) is C(1), while the gas-phase structure of HCO(3)(-) possesses Cs symmetry. No dimers could be found in aqueous solutions, but at the highest KHCO(3) concentration (3.270 mol/kg) intermolecular coupling between HCO(3)(-)(aq) anions could be detected. KHCO(3) solutions do not dissolve congruently, and with increasing concentrations of the salt increasing amounts of carbonate could be detected. Raman and infrared spectra of aqueous Na(2) -, K(2) -, and Cs(2)CO(3) solutions in water and heavy water were measured down to 50 cm(-1) and in some cases down to extremely low concentrations (0.002 mol/kg) and up to the saturation state. For carbonate in aqueous solution a symmetry breaking of the D(3h) symmetry could be detected similar to the situation in aqueous nitrate solutions. Strong hydration of carbonate in aqueous solution could be detected by Raman spectroscopy. The hydrogen bonds between carbonate in heavy water are stronger than the ones in normal water. In sodium and potassium carbonate solutions no contact ion pairs could be detected even up to the saturated solutions. However, solvent separated ion pairs were inferred in concentrated solutions in accordance with recent dielectric relaxation spectroscopy (DRS) measurements. Quantitative Raman measurements of the hydrolysis of carbonate in aqueous K(2)CO(3) solutions were carried out and the hydrolysis degree a was determined as a function of concentration at 22 degrees C. The second dissociation constant, pK(2), of the carbonic acid was determined to be equal to 10.38 at 22 degrees C.

Identification of Rare Bacterial Pathogens by 16S rRNA Gene Sequencing and MALDI-TOF MS.

There are a number of rare and, therefore, insufficiently described bacterial pathogens which are reported to cause severe infections especially in immunocompromised patients. In most cases only few data, mostly published as case reports, are available which investigate the role of such pathogens as an infectious agent. Therefore, in order to clarify the pathogenic character of such microorganisms, it is necessary to conduct epidemiologic studies which include large numbers of these bacteria. The methods used in such a surveillance study have to meet the following criteria: the identification of the strains has to be accurate according to the valid nomenclature, they should be easy to handle (robustness), economical in routine diagnostics and they have to generate comparable results among different laboratories. Generally, there are three strategies for identifying bacterial strains in a routine setting: 1) phenotypic identification characterizing the biochemical and metabolic properties of the bacteria, 2) molecular techniques such as 16S rRNA gene sequencing and 3) mass spectrometry as a novel proteome based approach. Since mass spectrometry and molecular approaches are the most promising tools for identifying a large variety of bacterial species, these two methods are described. Advances, limitations and potential problems when using these techniques are discussed.

Determination of the relative amounts of Gag and Pol proteins in foamy virus particles.

We determined the relative ratios of Gag and Pol molecules in highly purified virions of spumaretroviruses or foamy viruses (FVs) using monoclonal antibodies and bacterially expressed reference proteins. We found that the cleaved p68Gag moiety dominates in infectious FVs. Furthermore, approximate mean ratios in FV are 16:1 (pr71Gag plus p68Gag:p85RT),12:1 (p68Gag:p85RT), and 10:1 (pr71Gag plus p68Gag:p40IN). Thus, the results indicate that FVs have found a way to incorporate approximately as much Pol protein into their capsids as orthoretroviruses, despite a completely different Pol expression strategy.

Hydration and ion pair formation in aqueous Y(3+)-salt solutions.

Raman spectra of aqueous yttrium perchlorate, triflate (trifluoromethanesulfonate), chloride and nitrate solutions were measured over a broad concentration range (0.198-3.252 mol L(-1)). The spectra range from low wavenumbers to 4200 cm(-1). A very weak mode at 384 cm(-1) with a full width at half height at 50 cm(-1) in the isotropic spectrum suggests that the Y(3+)- octa-aqua ion is thermodynamically stable in dilute perchlorate solutions (∼0.5 mol L(-1)) while in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed. The octa-hydrate, [Y(OH2)8](3+) was also detected in a 1.10 mol L(-1) aqueous Y(CF3SO3)3 solution. Furthermore, very weak and broad depolarized modes could be detected which are assigned to [Y(OH2)8](3+)(aq) at 100, 166, 234 and 320 cm(-1) confirming that a hexa-hydrate is not compatible with the hydrated species in solution. In yttrium chloride solutions contact ion pair formation was detected over the measured concentration range from 0.479-3.212 mol L(-1). The contact ion pairs in YCl3(aq) are fairly weak and disappear with dilution. At a concentration <0.2 mol L(-1) almost all complexes have disappeared. In YCl3 solutions, with additional HCl, chloro-complexes of the type [Y(OH2)8-nCln](+3-n) (n = 1,2) are formed. The Y(NO3)3(aq) spectra were compared with a spectrum of a dilute NaNO3 solution and it was concluded that in Y(NO3)3(aq) over the concentration range from 2.035-0.198 mol L(-1) nitrato-complexes [Y(OH2)8-n(NO3)ln](+3-n) (n = 1,2) are formed. The nitrato-complexes are weak and disappear with dilution <0.1 mol L(-1). DFT geometry optimizations and frequency calculations are reported for both the yttrium-water cluster in the gas phase and the cluster within a polarizable continuum model in order to implicitly describe the presence of the bulk solvent. The bond distance and angle for the square antiprismatic cluster geometry of [Y(OH2)8](3+) with the polarizable dielectric continuum is in good agreement with data from recent structural experimental measurements. The DFT frequency of the Y-O stretching mode of the [Y(OH2)8](3+) cluster, in a polarizable continuum, is at 372 cm(-1) in satisfactory agreement with the experimental value.

Hydration and ion pair formation in common aqueous La(III) salt solutions--a Raman scattering and DFT study.

Raman spectra of aqueous lanthanum perchlorate, triflate (trifluorosulfonate), chloride and nitrate solutions were measured over a broad concentration (0.121-3.050 mol L(-1)) range at room temperature (23 °C). A very weak mode at 343 cm(-1) with a full width at half height at 49 cm(-1) in the isotropic spectrum suggests that the nona-aqua La(III) ion is thermodynamically stable in dilute perchlorate solutions (∼0.2 mol L(-1)) while in concentrated perchlorate solutions outer-sphere ion pairs and contact ion pairs are formed. The La(3+) nona-hydrate was also detected in a 1.2 mol L(-1) La(CF3SO3)3(aq). In lanthanum chloride solutions chloro-complex formation was detected over the measured concentration range from 0.5-3.050 mol L(-1). The chloro-complexes in LaCl3(aq) are fairly weak and disappear with dilution. At a concentration <0.1 mol L(-1) almost all complexes disappeared. In LaCl3 solutions, with additional HCl, a series of chloro-complexes of the type [La(OH2)(9-n)Cln](+3-n) (n = 1-3) were formed. The La(NO3)3(aq) spectra were compared with a spectrum of a 0.409 mol L(-1) NaNO3(aq) and it was concluded that in La(NO3)3(aq) over the concentration range from 0.121-1.844 mol L(-1), nitrato-complexes, [La(OH2)(9-n)(NO3)n](+3-n) (n = 1, 2) were formed. These nitrato-complexes are quite weak and disappear with dilution <0.01 mol L(-1). DFT geometry optimizations and frequency calculations are reported for a lanthanum-nona-hydrate with a polarizable dielectric continuum in order to take the solvent into account. The bond distances and angles for the cluster geometry of [La(OH2)9](3+) with the polarizable dielectric continuum are in good agreement with data from recent structural experimental measurements and high quality simulations. The DFT frequency of the La-O stretching mode at 328.2 cm(-1), is only slightly smaller than the experimental one.

Zinc(II) hydration in aqueous solution. A Raman spectroscopic investigation and an ab-initio molecular orbital study.

Raman spectra of aqueous Zn(II) perchlorate solutions were measured over a broad concentration (0.50-3.54 mol L-1) and temperature (25-120°C) range. The weak polarized band at 390 cm-1 and two depolarized modes at 270 and 214 cm-1 have been assigned to ν1(a1g), ν2(eg) and ν5(f2g) of the hexaaquazinc(II) ion, respectively. The infrared active mode at 365 cm-1 has been assigned to ν3(f1u). The vibrational analysis of the species [Zn(OH2)62+] was done on the basis of Oh symmetry (OH2 as point mass). The polarized mode ν1(a1g) ZnO6 has been followed over the full temperature range and band parameters (band maximum, full width of half height and band intensity) have been examined. The position of the ν1(a1g) ZnO6 mode shifts only about 4 cm-1 to lower frequencies and broadens about 32 cm-1 for a 95°C temperature increase. The Raman spectroscopic data suggest that the hexaaquazinc(II) ion is thermodynamically stable in perchlorate solution over the temperature and concentration range measured. Abinitio geometry optimizations and frequency calculations of [Zn(OH2)62+] were carried out at the Hartree-Fock and second order Møller-Plesset levels of theory, using various basis sets up to 6-31+G*. The global minimum structure of the hexaaqua Zn(II) species corresponds with symmetry Th. The unscaled vibrational frequencies of the [Zn(OH2)62+] were reported. The unscaled vibrational frequencies of the ZnO6 unit are lower than the experimental frequencies (ca. 15%), but scaling the frequencies reproduces the measured frequencies. The theoretical binding enthalpy for [Zn(OH2)62+] was calculated and accounts for ca. 64% of the experimental single ion hydration enthalpy for Zn(II). Abinitio geometry optimizations and frequency calculations are also reported for a [Zn(OH2)182+] (Zn[6+12]) cluster with 6 water molecules in the first sphere and 12 water molecules in the second sphere. The global minimum corresponds with T symmetry. Calculated frequencies of the zinc [6+12] cluster correspond well with the observed frequencies in solution. The ν1 ZnO6 (unscaled) mode occurs at 389 cm-1 in good agreement with the experimental value. The theoretical binding enthalpy for [Zn(OH2)182+] was calculated and is very close to the experimental single ion hydration enthalpy for Zn(II). The water molecules of the first sphere form strong H-bonds with water molecules in the second hydration shell because of the strong polarizing effect of the Zn(II) ion. The importance of the second hydration sphere is discussed.

Vibrational spectroscopic studies and DFT calculations on NaCH3CO2(aq) and CH3COOH(aq).

Aqueous solutions of sodium acetate, NaCH3CO2, and acetic acid, CH3COOH, were studied using Raman and infrared spectroscopy. The spectra were recorded over a large concentration range, in the terahertz region and up to 4000 cm(-1). In the isotropic Raman spectrum in R-format, a polarized band at 189 cm(-1) was assigned to the ν1Na-O stretch of the hydrated Na(+)-ion and a shoulder at 245 cm(-1) to the restricted translation band, νsO-H···O* of the hydrated acetate ion, CH3CO2(-)(aq). The CH3CO2(-)(aq) and the hydrated acetic acid, CH3COOH(aq), possess pseudo Cs symmetry. Geometrical parameters for the species in the gas phase and for CH3CO2(-)(aq) and CH3COOH(aq) are reported. Characteristic bands for CH3CO2(-)(aq) and CH3COOH(aq) were assigned under the guidance of the DFT vibrational frequency calculations and discussed in detail. In aqueous NaCH3CO2 solutions, at high concentrations, no contact ion pairs could be detected, but instead solvent separated ion pairs were found. In LiCH3CO2(aq), however, contact ion pairs are formed which is indicated by the appearance of a shoulder at 939 cm(-1) and the shift of the symmetric stretching mode of the -CO2(-) group to higher wavenumbers.