title: Molecular structures and stability constants of gossypol and its aza-derivative complexes with silver(I) cations studied by potentiometric, ESI MS, NMR, and AM1d semiempirical methods.
abstract: Stability constants of complexes formed by gossypol and by ten of its Schiff bases with Ag (+) cations were determined by the potentiometric method. The potentiometric and ESI MS experiments indicate the formation of AgL (+) and Ag 2L (2+) complexes between the Schiff bases G1-G7 and Ag (+) cations as well as the formation of AgL (+), Ag 2L (2+), AgL 2 (+) and Ag 3L 2 (3+) complexes between the Schiff bases G8-G10 and Ag (+) cations. The highest stability constant was found for the AgL (+) complex of G8 Schiff base and the lowest one for the AgL (+) complex of G molecule. The (13)C NMR spectra of mixtures between G and AgClO 4 as well as G1-G10 and AgClO 4 indicate that the complexation of the Ag (+) cations is exclusively realized by the aldehyde-aldehyde tautomer of gossypol and by the enamine-enamine form of gossypol Schiff bases, respectively. We show that the main coordination sites for the Ag (+) metal cations are either the oxygen or the nitrogen atoms of the amine parts of the Schiff bases of gossypol. The energetically most favorable structures of the Ag (+) complexes with gossypol (G) or with the gossypol Schiff bases (G1-G10) were calculated and visualized by the AM1d method at an semiempirical level of theory.
authors.affiliation: Faculty of Chemistry, Adam Mickiewicz University, 60-780 Poznań, Grunwaldzka 6, Poland. piotrp@amu.edu.pl
authors.forename: Piotr
authors.initials: P
authors.lastname: Przybylski
authors.forename: Jaromir
authors.initials: J
authors.lastname: Kira
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Schroeder
authors.forename: Bogumił
authors.initials: B
authors.lastname: Brzezinski
authors.forename: Franz
authors.initials: F
authors.lastname: Bartl
mesh_terms: D001372:Aza Compounds / Q000737:chemistry*; D006072:Gossypol / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008956:Models, Chemical; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000737:chemistry*; D011199:Potentiometry; D012545:Schiff Bases / Q000737:chemistry*; D012834:Silver / Q000737:chemistry*; D021241:Spectrometry, Mass, Electrospray Ionization; D013816:Thermodynamics
chemical_list: D001372:Aza Compounds; D009942:Organometallic Compounds; D012545:Schiff Bases; D012834:Silver; D006072:Gossypol