Przybylski Piotr, Kira Jaromir, Schroeder Grzegorz, Brzezinski Bogumił, Bartl Franz
Faculty of Chemistry, Adam Mickiewicz University, 60-780 Poznań, Grunwaldzka 6, Poland.
J Phys Chem A. 2008 Sep 4;112(35):8061-9. doi: 10.1021/jp8043434. Epub 2008 Aug 13.
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.
通过电位滴定法测定了棉酚及其十种席夫碱与银（+）阳离子形成的配合物的稳定常数。电位滴定和电喷雾电离质谱实验表明，席夫碱G1-G7与银（+）阳离子之间形成了AgL（+）和Ag₂L（2+）配合物，席夫碱G8-G10与银（+）阳离子之间形成了AgL（+）、Ag₂L（2+）、AgL₂（+）和Ag₃L₂（3+）配合物。发现G8席夫碱的AgL（+）配合物的稳定常数最高，而G分子的AgL（+）配合物的稳定常数最低。G与高氯酸银以及G1-G10与高氯酸银混合物的（13）C NMR光谱表明，银（+）阳离子的络合分别由棉酚的醛-醛互变异构体和棉酚席夫碱的烯胺-烯胺形式单独实现。我们表明，银（+）金属阳离子的主要配位位点是棉酚席夫碱胺部分的氧原子或氮原子。通过AM1d方法在半经验理论水平上计算并可视化了银（+）与棉酚（G）或棉酚席夫碱（G1-G10）形成的配合物的能量上最有利的结构。
