A new hexadentate, tripodal 8-hydroxyquinoline based ligand (QH3) and its gadolinium(III) tris-chelated (GdQ) complex with hemicage structure was investigated by using high resolution Fourier-transform ion cyclotron resonance mass spectrometry (FTICRMS). The protonated adduct of the free ligand and its hemicage tripodal Gd(III) complex, [GdQ + H]+, were first observed in experiments of electrospray ionization (ESI) with a linear ion trap (LTQ) mass spectrometer and further investigated by using high resolution FTICRMS. Gas-phase dissociation of the protonated Gd(III) complex, by infrared multiphoton dissociation (IRMPD) FTICR MS, demonstrated a fragmentation pattern with six main product cluster ions labeled as [Fn]+ (n = 1 up to 6). These product ions suggest the elimination of 7-amino-alkyl or 7-alkyl chains of the hemicage moiety. High resolution MS conditions allowed the elucidation of the fragmentation pattern and product ion structures along with the determination, among the isotopic pattern of Gd, of the chemical compositions of closely related species, which differ in terms of hydrogen content. Among the Gd six naturally stable isotopes, 158Gd is the most abundant, and its peak within each cluster was used as a reference for distinguishing each product ions. Computational DFT investigations were applied to give support to some hypothesis of fragmentation pathways, which could not have been easily justified on the basis of the experimental work. Furthermore, computational studies suggested the coordination geometry of the protonated parent complex and the five- and four-coordinated complexes, which derive from its fragmentation. Furthermore, experimental and computational evidences were collected about the octet spin state of the parent compound.
通过高分辨傅里叶变换离子回旋共振质谱法(FTICRMS)研究了一种新型六齿三足
8-羟基喹啉配体(QH3)及其具有半笼结构的
镧系元素(III)三配位(GdQ)配合物。在电喷雾电离(ESI)实验中,使用线性离子阱(LTQ)质谱仪首次观察到自由
配体的质子化加合物及其半笼三足Gd(III)配合物[GdQ + H]+,并进一步通过高分辨FTICRMS进行研究。通过红外多光子解离(IR
MPD)FTICR MS对质子化Gd(III)配合物的气相解离进行了研究,显示了带有六个主要产物簇离子的碎裂模式,标记为[Fn]+(n=1至6)。这些产物离子表明半笼部分的7-
氨基烷基或7-烷基链的消除。在高质量分辨率MS条件下,阐明了碎裂模式和产物离子结构,并根据Gd的同位素模式确定了
化学组成,这些
化学组成在氢含量方面存在差异。在Gd的六种天然稳定同位素中,158Gd最丰富,其峰值用于区分离子。计算DFT研究应用于支持一些无法仅根据实验工作轻易证实的碎裂途径假设。此外,计算研究提出了质子化的母体配合物、五配位和四配位配合物的配位几何结构,这些配合物来自其碎裂过程。此外,实验和计算证据也支持了母体化合物的八重自旋态。