Determination of the stability constant of the ternary complex formed in the copper-bipyridyl-eriochrome cyanine R system, by an isosbestic point-spectrophotometric method

Importance of isosbestic point in spectroscopy: a review

“…[69] In another work, evaluate of equilibrium constants of two mutual competitive reactions by the method of isosbestic points. [70] Estimation of the molar absorption coefficient of hydrated electron. [71] The determination of the Reaction Rate for the first step in a consecutive reaction A → B → C by absorbance measurements using the wavelength of the isosbestic point of B and C. [72] The existence of isosbestic point in the spectrum of parallel or consecutive first order reaction at a certain wavelength lead to time-independent [73].…”

Ultraviolet and light absorption spectrometry

“…A new differential method for determining association constants, illustrated with 3,3'diethylselenocarbocyanine in ethanol, is described in another paper (524). Stability constants of metal complexes have been determined by using a least-squares algorithm in which the constant is refined by a numerical search method (illustrated with the copper-imidazole complex) (47), a factor analysis of the absorption curve (illustrated with o,o -dihydroxyphenylazo dye, solochrome violet, and 2-a-[(2-hydroxyphenyl)azo]-aacetonitrile complexes of nickel) (392), and measurements at the isosbestic points (illustrated with the copper-2,2/-bipyridine-eriochrome cyanine R ternary complex) (581). In another paper, a mathematical modeling method was used to define the criteria for the limits of applicability of linear approximations for calculating stability constants from absorbance data obtained at a wavelength at which only the complex absorbs (208).…”