Department of Chemistry, Idaho National Laboratory, Idaho Falls, Idaho 83415-2208, USA.
J Am Soc Mass Spectrom. 2010 May;21(5):719-27. doi: 10.1016/j.jasms.2010.01.021. Epub 2010 Jan 28.
Tris-carboxylate complexes of uranyl UO(2) with acetate and benzoate were generated using electrospray ionization mass spectrometry, and then isolated in a Fourier transform ion cyclotron resonance mass spectrometer. Wavelength-selective infrared multiple photon dissociation (IRMPD) of the tris-acetato uranyl anion resulted in a redox elimination of an acetate radical, which was used to generate an IR spectrum that consisted of six prominent absorption bands. These were interpreted with the aid of density functional theory calculations in terms of symmetric and antisymmetric -CO(2) stretches of the monodentate and bidentate acetate, CH(3) bending and umbrella vibrations, and a uranyl O-U-O asymmetric stretch. The comparison of the calculated and measured IR spectra indicated that the predominant conformer of the tris-acetate complex contained two acetate ligands bound in a bidentate fashion, while the third acetate was monodentate. In similar fashion, the tris-benzoate uranyl anion was formed and photodissociated by loss of a benzoate radical, enabling measurement of the infrared spectrum that was in close agreement with that calculated for a structure containing one monodentate and two bidentate benzoate ligands.
采用电喷雾电离质谱生成了铀酰UO(2)与乙酸盐和苯甲酸盐的三羧酸配合物，然后在傅里叶变换离子回旋共振质谱仪中进行了分离。三乙酸铀酰阴离子的波长选择性红外多光子解离（IRMPD）导致乙酸根自由基的氧化还原消除，用于生成包含六个显著吸收带的红外光谱。借助密度泛函理论计算，这些带被解释为单齿和双齿乙酸盐的对称和反对称-CO(2)伸展、CH(3)弯曲和伞式振动以及铀酰 O-U-O 不对称伸展。计算和测量的红外光谱的比较表明，三乙酸盐配合物的主要构象包含两个以双齿方式结合的乙酸盐配体，而第三个乙酸盐是单齿的。以类似的方式形成了三苯甲酸盐铀酰阴离子，并通过失去苯甲酸盐自由基进行光解，从而能够测量与计算的包含一个单齿和两个双齿苯甲酸盐配体的结构非常吻合的红外光谱。
