A Relativistic DFT Probe of Thorium and Protactinium Complexes Supported by Heterocalix[4] arene and Redox Properties of Early-Middle Actinides

作者：Bi, Yan-Ting; Bao, Zhe; Li, Li; Shen, Zhong-Hui^*; Pan, Qing-Jiang^*

来源：ChemistrySelect, 2018, 3(17): 4804-4810.

DOI：10.1002/slct.201800328

• Electronic structures
• hybrid heterocalix[4] arene
• Low-valent thorium and protactinium complexes
• redox properties
• relativistic DFT

Thorium and protactinium complexes of trans-calix[2]benzene[2]pyrrolide (H2L) have been examined using a relativistic density functional theory, where the metal center has + IV and + III oxidation states and is saturated by a borohydride donor. Good agreement in geometry parameters has been achieved for the thorium(VI) complex compared with its experimentally obtained analogue. Three types of conformers, labeled as (L-Ar)(An(m))(B-2H), (L-Ar)(An(m))(B-3H) and (L-Pl)(An(m))(B-3H) (An = Th and Pa, m = VI and III), are energetically favored for each complex. The first and last configurations are found to be the most stable for tri- and tetravalent complexes, respectively. Intriguing delta(An-Ar) bonding(s) are revealed for trivalent complexes (L-Ar)(An(III))(B-2H); and (L-Pl)(Pa-IV)(B-3H) has a Pa(5f)-dominated HOMO, while (L-Pl)(Th-IV)(B-3H) displays a 5f(0)6d(0)7s(0) electronic configuration. Exothermic process was calculated for reactions starting from actinide borohydride sources and various macrocyclic ligands. From a thermodynamic perspective, this provides synthetically accessible possibility of these complexes. The mechanism of reducing tetra- to trivalent actinide complexes has been proposed. Reduction potentials were calculated to follow the order of Th < Pa < U < Np < Pu, which well reproduces reported results of aquo An(VI)/An(III) ions.

• 出版日期2018-5-8
• 单位黑龙江大学