Aqueous spectroscopic studies

Photoelectron spectroscopic studies show that the first ionization potential (lone pair electrons) for cyclic amines falls in the order aziridine (9.85 eV) > azetidine (9.04) > pyrrolidine (8.77) >piperidine (8.64), reflecting a decrease in lone pair 5-character in the series. This correlates well with the relative vapour phase basicities determined by ion cyclotron resonance, but not with basicity in aqueous solution, where azetidine (p/iTa 11.29) appears more basic than pyrrolidine (11.27) or piperidine (11.22). Clearly, solvation effects influence basicity (74JA288). 

In aqueous solutions at pH 7, there is little evidence of complex formation between [MesSnflV)] and Gly. Potentiometric determination of the formation constants for L-Cys, DL-Ala, and L-His with the same cation indicates that L-Cys binds more strongly than other two amino acids (pKi ca. 10,6, or 5, respectively). Equilibrium and spectroscopic studies on L-Cys and its derivatives (S-methyl-cystein (S-Me-Cys), N-Ac-Cys) and the [Et2Sn(IV)] system showed that these ligands coordinate the metal ion via carboxylic O and the thiolic 5 donor atoms in acidic media. In the case of S-Me-Cys, the formation of a protonated complex MLH was also detected, due to the stabilizing effect of additional thioether coordination. ... 

Crisp, S., Prosser, H. J. Wilson, A. D. (1976). An infra-red spectroscopic study of cement formation between metal oxides and aqueous solutions of poly(acrylic acid). Journal of Materials Science, 11, 36-48. 

Hoshi N, Bae IT, Scherson DA. 2000. In situ infrared reflection absorption spectroscopic studies of coadsorption of CO with underpotential-deposited lead on Pt(lll) in an aqueous acidic solution. J Phys Chem B 104 6049-6052. 

The phosphorescence of Pt2 (I OsKHq in aqueous solution is quenched by l,l-bis(2-sulfoethyl)-4,4f-bipyridinium inner salt (BSEP). Transient absorption attributable to BSEP ( nax 610 nn) is observed in flash kinetic spectroscopic studies of aqueous solutions containing Pt2( Os Hq and BSEP, thereby establishing an electron transfer quenching mechanism ... 

UV-VIS spectroscopic studies (9-11,16) establish that in aqueous solution TPPS (and its metal-substituted derivatives) is in equilibrium with [TPPS]2 Dimerization can be promoted by increasing the ionic strength of the solution or by addition of cation-18crown6 (9-11) The EPR spectrum of CuTPPS in frozen H20-glycerol establishes the presence of a mixture of monomers and dimers. The EPR spectrum of [CuTPPS]2 shows that the Cu-Cu distance is 0.56 nm. 

The existence of difluorochlorates of sodium, potassium, and barium was reported in 1965 by Mitra (19S). However, this claim was met by skepticism since the reported synthesis involved the use of 40% aqueous hydrofluoric acid. In a subsequent paper (J96), Mitra withdrew his claim. In 1969, Huggins and Fox reported (141,142) the synthesis of CSCIF2O2 from CsF and FCIO2, and a subsequent spectroscopic study by Christe and Curtis showed (54) that the vibrational spectrum of the adduct is consistent with a CIF202 anion of symmetry C2V... 

Music, S. Vertes, A. Simmons, G.W Czako-Nagy, I. Leidheiser, H.Jr. (1982) Mossbauer spectroscopic study of the formation of Fe(III) oxyhydroxides and oxides by hydrolysis of aqueous Fe(III) salt solutions. J. Colloid Interface Sd. 85 256—266... 

Similar to ketones, diketones also react readily with phosphine in aqueous, strong hydrochloric acid media Thus, 2,4-pentadione gives a colourless crystalline substance of composition CjoHiyOgP in good yield. On the basis of spectroscopic studies and the chemical properties of the compound the authors suggest the structure 11. 

Theoretical and spectroscopic studies of the protonation of tetrazoles have been discussed in Sections 4.17.2.2 and 4.17.3. Protonation of 5-substituted tetrazoles, 1,5-disubstituted tetrazoles and 2,5-disubstituted tetrazoles in aqueous H2SO4 at H2SO4 concentrations up to 96% occurs at N-4 <82KGS142l>. The tetrazoles are weak bases with basic pAl values of about —3 to —4 <87AHC(4i)i87>. A basic pXj value of —3.0 has been measured for tetrazole in aqueous H2SO4. Hammett relationships have been reported for the basic pX values of 5-substituted tetrazoles... 

Hemes encapsulated in aqueous detergent micelles find themselves in a large macromolecular cavity whose interaction is mainly hydrophobic. It has been suggested that such systems appear to simulate the electrostatic and hydrophobic interactions of the heme cavity in metalloproteins. The present article surveys reported studies on natural and synthetic hemes, both ferric and ferrous, incorporated inside micelles of different sizes and surface charges. The emphasis is laid on multinuclear NMR and optical spectroscopic studies. The effect of micellar interactions on the electronic properties of hemes is discussed and compared with that of the heme cavity in proteins. 

D. E. Sandstrom, O.N. Antzutkin, W. Forsling, A spectroscopic study of calcium surface sites and adsorbed iron species at aqueous fluorapatite by means of 1H and 31P MAS NMR, Langmuir 22 (2006) 11060-11064. 

Merlin, J.-C. et al.. Resonance Raman-spectroscopic studies of anthocyanins and anthocyanidins in aqueous-solutions. Phytochemistry, 35, 227, 1994. 

Electrochemical reductions of CO2 at a number of metal electrodes have been reported [12, 65, 66]. CO has been identified as the principal product for Ag and Au electrodes in aqueous bicarbonate solutions at current densities of 5.5 mA cm [67]. Different mechanisms for the formation of CO on metal electrodes have been proposed. It has been demonstrated for Au electrodes that the rate of CO production is proportional to the partial pressure of CO2. This is similar to the results observed for the formation of CO2 adducts of homogeneous catalysts discussed earlier. There are also a number of spectroscopic studies of CO2 bound to metal surfaces [68-70], and the formation of strongly bound CO from CO2 on Pt electrodes [71]. These results are consistent with the mechanism proposed for the reduction of CO2 to CO by homogeneous complexes described earlier and shown in Sch. 2. Alternative mechanistic pathways for the formation of CO on metal electrodes have proposed the formation of M—COOH species by (1) insertion of CO2 into M—H bonds on the surface or (2) by outer-sphere electron transfer to CO2 followed by protonation to form a COOH radical and then adsorption of the neutral radical [12]. Certainly, protonation of adsorbed CO2 by a proton on the surface or in solution would be reasonable. However, insertion of CO2 into a surface hydride would seem unlikely based on precedents in homogeneous catalysis. CO2 insertion into transition metal hydrides complexes invariably leads to formation of formate complexes in which C—H bonds rather than O—H bonds have been formed, as discussed in the next section. 

Thallium(I) oxide, T120, is a well-characterized compound and a useful source of Tl+ salts.1 Matrix isolation studies of the solid gave structural data in agreement with spectroscopic results.290,291 The so-called peroxide T102 is obtained electrochemically from aqueous T12S04, but the properties include insolubility in water, alkali and some dilute adds, and treatment with dilute HC1 yields oxygen. The stoichiometry suggests that the compound is in fact a superoxide, and this has been confirmed by spectroscopic studies on frozen matrices.292,293... 

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