The title complexes [Al（Hcah）（H2O）2]·2H2O （A） and [Bi（Hcah）（H2O）]n （B）, where H4cah = 2-[N,N-bis（carboxymethyl）aminomethyl] hydroquinone, have been synthesized and characterized using X-ray single-crystal structure determination, IR and elemental analysis. Both complexes crystallize in the monoclinic system, space group P21/c with a = 7.8660（16）, b = 10.096（2）, c = 19.053（4） and β = 93.50（3）° for A; and those for B： a = 9.2348（18）, b = 7.9061（16）, c = 17.141（3） and β = 102.64（3）°. In addition, further investigation revealed that the central Al（III） ion in the mononuclear complex A is in a distorted octahedral coordination geometry, while structural analysis reveals that the Bi（III） ion is in a distorted pentagonal bipyramid, forming a 2-D polymeric complex B, and the coordination network is a 2D 4.82 net. The TG analyses of A indicate two steps of water loss.
Fluorescence spectroscopy, Fourier transform infrared （FT-IR） spectroscopy, circular dichroism （CD） and FT-Raman spectroscopy were employed to analyze the binding of the asiatic acid （AA） to bovine serum albumin （BSA） under simulative physiological conditions. Fluorescence data revealed that the fluorescence quenching of BSA by AA was the result of the formation of BSA-AA complex. The fluorescence quenching mechanism of BSA by AA was a static quenching procedure. According to the Van＇t Hoff equation, the thermodynamic parameters enthalpy change （△H0） and entropy change （△S0） for the reaction were evaluated to be --12.55 kJ·mol^-1 and 67.08 kJomol 1, respectively, indicating that hydrophobic and electrostatic interactions played a major role in stabilizing the complex. The influence of AA on the conformation of BSA has also been analyzed on the basis of FT-IR, CD and FT-Raman spectra.
Yao, Di Ni, Shouhai Wen, Maogui Bian, Hedong Yu, Qing Liang, Hong Chen, Zhenfeng
