Graphical methods for determining the number of species in solution from spectrophotometric data

Coleman, James S.; Varga, L.; Mastin, Stephen H.

doi:10.1021/ic50087a003

Cited by 176 publications

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“…All spectra were recorded on a Perkin-Elmer Hitachi Model 340 microprocessor spectrometer. The graphical method 4 for determining the number of species in solution requires large absorbance changes to reduce error to a minimum. Where possible, an isosbestic point for a given protonation step was chosen as an origin and the spectra run with the absorbance scale expanded.…”

Section: +mentioning

confidence: 99%

“…Therefore, we expect, using equation (2) Ru(RBPZ)(H2BPZ)7+ also overlap as shown in Figures 10(b) and 11(a). Because of this, it is not possible to calculate pKa 4 and pKa 5 without a more detailed analysis of both the ground and excited state protonation data. Nevertheless, the emission maxima and excited state lifetimes are reported in Table 4.…”

Section: +mentioning

confidence: 99%

“…We have also undertaken protonation experiments with the complexes M(CO) 4 BPZ 31 (M Mo, W) where the presence of only one BPZ ligand provides for an easier analysis.…”

Section: Regiamentioning

confidence: 99%

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Protonation equilibria in excited-state tris(bipyrazine)ruthenium(II)

Crutchley¹,

Kress²,

Lever³

1983

J. Am. Chem. Soc.

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Section: +mentioning

confidence: 99%

Section: +mentioning

confidence: 99%

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Protonation equilibria in excited-state tris(bipyrazine)ruthenium(II)

Crutchley¹,

Kress²,

Lever³

1983

J. Am. Chem. Soc.

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“…applied to spectrophotometric data by a number of authors (4)(5)(6). The combination of these two techniques can reveal information not easily obtained by other methods.…”

Section: Introductionmentioning

confidence: 99%

Factor Analysis as a Complement to Band Resolution Techniques. III. Self Association in Trichloroacetic Acid

Bulmer¹,

Shurvell²

1975

Can. J. Chem.

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Digitized infrared spectra of nine solutions of trichloroacetic acid in CCl4 have been studied in the carbonyl stretching region. At all concentrations only two bands are visually apparent. However, factor analysis indicates the presence of four absorbing components. The contour resolution technique gives a monomer band at 1786 cm−1, a dimer band at 1749 cm−1, and a third band close to the dimer frequency at approximately 1735 cm−1. Examination of the changes in Cauchy–Gauss shape ratio of the monomer band with increasing concentration indicates the presence of an unresolved component. The band at 1735 cm−1 and the unresolved band near the monomer peak at 1786 cm−1 are assigned to absorption of carbonyl groups in linear polymers of trichloroaceticacid. The monomer–dimer equilibrium constant was calculated from the molar absorption coefficients and absorbances of monomer and dimer bands. The average value over the concentration range 0.305 × 10−3 to 0.1603 M was 287 l/mol at 33.9 ± 0.5 °C.

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“…Determination of the number of absorbance species using Coleman's method The study of the reactions using the changes in the absorption spectra is facilitated by applying Coleman's matrix procedure (12) for the assignment of species that cause the absorption. Coleman's method is the first step in a systematic spectrophotometric study and allows for the rigorous determination of the number of absorption species beginning from the absorbance values of a group of solutions at different wavelengths.…”

Section: The Influence Of Temperature and Time On The Reactionsmentioning

confidence: 99%

Associations of ajmaline and homatropine with bromocresol green and bromophenol blue in dichloromethane: thermodynamic and kinetic parameters

Gainza¹

1987

Can. J. Chem.

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. Ajmaline (AJ) and homatropine (HM) react with bromocresol green (BCG) and bromophenol blue (BPB) in dichloromethane forming 1: 1 and 1:2 ion pairs clearly in a chemical equilibrium. Thermodynamic parameters AGO, AH', and ASQ are calculated using the Van't Hoff equation. In a large excess of HM a product P is formed from the 1:2 ion pair in a pseudo-first order kinetic process which fits Arrhenius' equation. The P product has been identified as a type of charge transfer complex. The thermodynamic parameters corresponding to the formation of the ion pairs BPB-(AJ), , BCG-(AJ),, BPB-(HM), , and BCG-(HM), are, respectively: AGO at 294 K, -26, -21, -26, and -19 kJ/mol; AH O, -63, -39, -63, and -61 kJ/mol; AS', -125, -62, -125, and -138 J/K mol (AH' and AS0 determined in a 288 to 3 13 K range). The values of the activation energy, E,, for the reaction of HM (in large excess) with BCG and BPB are 58 and 91 kJ/mol. IntroductionThe two phase photometric titration of amines with sulphonphthaleinic dyes is an important method for the analysis of pharmacologically active substances.The most widely proposed dye is bromothymol blue (BTB) because of its high hydrophobicity and exclusive extraction as 1:l associates in the complete pH range (1-6).The reaction, however, is unspecific. This is a disadvantage and a number of studies have been dedicated to this aspect (7,8). More recently, Sakai (9, 10) has proposed a method of selective extraction for a number of quaternary ammonium ions using the 1:2 associates of bromocresol green (BCG) and bromophenol blue (BPB) and quinine as a favourable substance for quantitative extraction of the complex. The stoichiometry assigned to the complex is 1: 1: 1 (quinine:dye:ammonium ion) and it is the quinine which is responsible for the specificity of the extraction of the'quaternary ammonium ion. The dye is extracted as divalent anion, X2-, associated at the same time with protonated quinine, QH+, and the quaternary ammonium compound, B' .In this study the formation of ion pairs of the divalent anion, X2-, of BCG and BPB with the alkaloids ajmaline (AJ) and homatropine (HM) is investigated. The changes in the visibleultraviolet absorption spectra of mixed solutions of BCG and BPB with variable quantities of AJ and HM in dichloromethane are elucidated. The formation of 1: 1 and 1:2 ion pairs in a clear chemical equilibrium is established and the variations in the thermodynamic variables, AGO, AH', and AS' are calculated from the spectrophotometric measurements.With a large excess of HM there appear new changes in the visible absorption spectrum of BCG and BPB; changes which cannot be attributed to the formation of ion pairs. The formation of a third product, P, in a pseudo-first order kinetic process is established, and the kinetic parameters are calculated from the spectrophotometric measurements.

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Graphical methods for determining the number of species in solution from spectrophotometric data

Cited by 176 publications

References 0 publications

Protonation equilibria in excited-state tris(bipyrazine)ruthenium(II)

Protonation equilibria in excited-state tris(bipyrazine)ruthenium(II)

Factor Analysis as a Complement to Band Resolution Techniques. III. Self Association in Trichloroacetic Acid

Associations of ajmaline and homatropine with bromocresol green and bromophenol blue in dichloromethane: thermodynamic and kinetic parameters

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