"Schiff Bases of Pyridoxal 5'-phosphate and 5'-deoxypyridoxal with Phen" by Venkatesh M. Shanbhag and Arthur E. Martell

Chemistry and Physics Faculty Articles

Title

Schiff Bases of Pyridoxal 5'-phosphate and 5'-deoxypyridoxal with Phenylglycine Derivatives and Their Metal Complexes

Authors

Venkatesh M. Shanbhag, Texas A&M UniversityFollow
Arthur E. Martell, Texas A&M University

Document Type

Article

Publication Date

3-1-1990

Publication Title

Inorganic Chemistry

ISSN

0020-1669

Volume

Issue/No.

First Page

1023

Last Page

1031

Abstract

Potentiometric p[H] measurements are employed to evaluate protonation constants, metal complex stabilities, and Schiff base (SB) formation constants in solutions containing pyridoxal 5'-phosphate (PLP) 5'-deoxypyridoxal (DPL), phenylglycine and its derivatives, and divalent transition-metal ions at 25°C and at an ionic strength of 0.100M (KNO₃). Protonation constants for phenylglycine (PG), (4-methoxyphenyl)glycine (MPG), and (4-sulfophenyl)glycine (SPG) indicate that these synthetic amino acids are more acidic than glycine and other natural amino acids. Stability constants are reported for 1:1 and 1:2 complexes of Mn²⁺, Co²⁺, Ni²⁺, Cu²⁺ and Zn²⁺ with PG, MPG, and SPG. Hydrolysis of these metal ions complicates the study of the nature of the metal complex formed at high p[H]. The vitamin B₆derivatives, pyridoxal 5'-phosphate and 5'-deoxypyridoxal, were found to form only 1:1 metal complexes. The equilibrium constants for the formation of Schiff bases by PLP and DPL with PG, MPG and SPG are reported. The monoprotonated form of the Schiff base was found to be the most stable species in each of the systems studied. The equilibrium constants are reported for protonated 1:1 Cu(II)-Schiff base complexes, CuSBH_xⁿ⁺ and for 1:1 and 2:1 Schiff base complexes of Mn(II), Co(II), Ni(II), and Zn(II). The formation of a number of hydroxometal Schiff base chelates in alkaline solutions is observed. The equilibrium constants determined are employed to calculate the distribution of complex species as a function of p[H] in solutions containing these ligands and the metal ions identified above.

Comments

NSUWorks Citation

Shanbhag, V. M., & Martell, A. E. (1990). Schiff Bases of Pyridoxal 5'-phosphate and 5'-deoxypyridoxal with Phenylglycine Derivatives and Their Metal Complexes. Inorganic Chemistry, 29, (5), 1023 - 1031. https://doi.org/10.1021/ic00330a023. Retrieved from https://nsuworks.nova.edu/cnso_chemphys_facarticles/129

DOI

10.1021/ic00330a023

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