Xiong Zhixin, Hu Jingwen, Chen Xiuting
Department of Radiochemistry, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai, China.
School of Chemical Sciences, School of Nuclear Science and Technology, University of Chinese Academy of Sciences, Beijing, China.
Rapid Commun Mass Spectrom. 2021 Oct 15;35(19):e9168. doi: 10.1002/rcm.9168.
Pyridine-2,6-dicarboxamides (PDCAMs) exhibit a certain extraction ability for tetravalent actinide ions, but quite limited information regarding the structures and reactivities of the corresponding An -PDCAMs complexes is available. Neutral diamides can form multiply charged complexes with lanthanide and actinide cations, which are well suited for gas-phase investigations using electrospray ionization (ESI) mass spectrometry in conjunction with theoretical calculation.
Binary Th (TMPDCAM) /U (TMPDCAM) (TMPDCAM = N,N,N',N'-tetramethylpyridine-2,6-dicarboxamide) complexes were generated in the gas phase via ES) of Th (ClO ) /U (ClO ) and TMPDCAM mixtures in acetonitrile; collision-induced dissociation (CID) was employed to reveal their fragmentation behaviors; the structure and bonding were investigated by density functional theory (DFT) calculation.
An (TMPDCAM) (An = Th and U) tetracations dominated the ESI mass spectra of An (ClO ) and TMPDCAM mixtures in acetonitrile. DFT calculations indicate that the two An (TMPDCAM) complexes have C geometry, and the bonding analyses demonstrate that the thorium or uranium center interacts with both O and N , but the latter is weaker. CID of Th (TMPDCAM) generated a series of multiply charged thorium-containing products via bond cleavages of the TMPDCAM ligand, whereas U (TMPDCAM) yielded only oxygen extraction product UO (TMPDCAM) and hydrolysis product UO (OH) .
An (An = Th and U) can form stable tetrapositive complexes in the gas phase on coordination of three neutral TMPDCAM ligands. The structure and bonding analyses indicate that the two An (TMPDCAM) complexes possess twisted tricapped trigonal prismatic geometry and the An centers are coordinated by six O and three N atoms while the interactions between An and O are stronger. The fragmentation chemistry of Th (TMPDCAM) and U (TMPDCAM) is quite different from each other, which reveals that the gas-phase chemistry of quadruply charged actinide-diamide complexes is affected by the metal centers with distinct properties.
吡啶 - 2,6 - 二甲酰胺（PDCAMs）对四价锕系离子具有一定的萃取能力，但关于相应的An - PDCAM配合物的结构和反应性的信息相当有限。中性二酰胺可与镧系和锕系阳离子形成多电荷配合物，这非常适合使用电喷雾电离（ESI）质谱结合理论计算进行气相研究。
通过在乙腈中对Th(ClO₄)₄/U(ClO₄)₄和TMPDCAM混合物进行电喷雾电离（ESI）在气相中生成二元Th(TMPDCAM)₄/U(TMPDCAM)₄（TMPDCAM = N,N,N',N'-四甲基吡啶 - 2,6 - 二甲酰胺）配合物；采用碰撞诱导解离（CID）揭示其碎片化行为；通过密度泛函理论（DFT）计算研究结构和键合。
An(TMPDCAM)₄（An = Th和U）四价阳离子在乙腈中An(ClO₄)₄和TMPDCAM混合物的ESI质谱中占主导地位。DFT计算表明，两种An(TMPDCAM)₄配合物具有C₃对称几何结构，键合分析表明钍或铀中心与O和N原子都相互作用，但与后者的作用较弱。Th(TMPDCAM)₄的CID通过TMPDCAM配体的键裂解产生了一系列多电荷含钍产物，而U(TMPDCAM)₄仅产生氧提取产物UO₂(TMPDCAM)₂和水解产物UO₂(OH)₂。
An（An = Th和U）在与三个中性TMPDCAM配体配位时可在气相中形成稳定的四价配合物。结构和键合分析表明，两种An(TMPDCAM)₄配合物具有扭曲的三棱柱几何结构，An中心由六个O和三个N原子配位，而An与O之间的相互作用更强。Th(TMPDCAM)₄和U(TMPDCAM)₄ 的碎片化化学彼此有很大不同，这表明四价锕系 - 二酰胺配合物的气相化学受具有不同性质的金属中心影响。
