Structure and Other Molecular Properties of Actinide Trichlorides AnCl₃ (An = Th–Cm)

Abstract

The ground-state molecular properties of the trichlorides of light actinides (An = Th-Cm) have been predicted by state-of-the-art quantum chemical calculations. The ground electronic states have been determined by multireference calculations at the CASPT2 level including both scalar and spin-orbit relativistic effects. These studies supported the expected single-configuration character of ThCl3 and CmCl3 with their well-defined 6dσ/7s hybrid and 5f(7) configurations, respectively. In contrast, the intermediate actinides (PaCl3-AmCl3) with partly filled 5f shells have numerous very low-lying excited states and consequently a mixed character of the spin-orbit ground states. Apart from the planar ThCl3 the ground-state molecular geometries proved to be pyramidal with C(3v) symmetry. The gradually decreasing An-Cl bond distances reveal the actinide contraction known for the atomic and ionic radii of these actinide atoms. Other ground-state molecular properties as vibrational frequencies and natural charges have been obtained by density functional theory calculations using the B3LYP exchange-correlation functional in conjunction with small-core relativistic energy-consistent pseudopotentials for the actinides.

Covalency in AnCl3 (An = Th–No)

“…In this contribution, we use computational quantum chemistry to study the bonding in AnCl 3 , surveying the actinide series from Th to No. Very little is known about these systems experimentally (the geometry of UCl 3 is an exception 21 ), although Kovács et al have studied them computationally, 22,23 and there have been other investigations of actinide halides. In 2013, Kovács et al used density functional theory (DFT) to study the geometries and vibrational frequencies of AnCl 3 (An = Th-Cm), and CASPT2 calculations to examine their ground and low-lying excited states, 22 and used solely DFT to study the later AnCl 3 (An = Bk-Lr) the following year.…”

“…Very little is known about these systems experimentally (the geometry of UCl 3 is an exception 21 ), although Kovács et al have studied them computationally, 22,23 and there have been other investigations of actinide halides. In 2013, Kovács et al used density functional theory (DFT) to study the geometries and vibrational frequencies of AnCl 3 (An = Th-Cm), and CASPT2 calculations to examine their ground and low-lying excited states, 22 and used solely DFT to study the later AnCl 3 (An = Bk-Lr) the following year. 23 Here we also use DFT to study AnCl 3 (An = Th-No), focusing on Natural Bond Orbital (NBO) and Quantum Theory of Atoms in Molecules (QTAIM) analysis of metal-chlorine covalency.…”

Chirality and Polarity in the f‐Block Borates M4[B16O26(OH)4(H2O)3Cl4] (M=Sm, Eu, Gd, Pu, Am, Cm, and Cf)

“…In fact, it is only in the halides, [11][12][13][14][15][16] iodate, [17][18][19] triflate, [20][21][22][23] and borate [24][25][26][27][28] series that single-crystal X-ray diffraction data and complementary spectroscopy and theory span from thorium to californium. When the discussion is restricted to actinides in the + 3 oxidation state, the halides, iodates, and triflates are isomorphous with lanthanide analogues, and any changes in structure ostensibly correlates with changes in ionic radii.…”

“…This series represents only the third example spanning to californium for which single-crystal structures are known; the others being the aqua complexes and the chlorides. [11][12][13][14][15][16][20][21][22][23] The nine-coordination ionic radii for Nd III 3 Cl 4 ] crystallizes in the polar and chiral, cubic space group, P2 1 3, and contains two crystallographically unique, nine-coordinate f-element centers with tricapped trigonal prismatic geometries (Figure 1 a). [33] Compound M 4 [B 16 O 26 (OH) 4 (H 2 O) 3 Cl 4 ] is a dense, three-dimensional framework structure (Figure 2 a) composed of corner-sharing BO 3 triangles and BO 4 tetrahedra that bind the f-element ion centers.…”

Theoretical study of the electronic spectra of neutral and cationic NpO and NpO2

“…The above described multireference methods and the ANO-RCC basis set were successfully applied in a number of studies on actinide-containing systems. 12,13,[51][52][53][54][55][56][57][58][59][60][61][62][63][64][65][66][67][68][69][70] The electronic spectra have been evaluated from the Einstein coefficient values (being directly related to the spectral intensities) computed at the SO-CASPT2 level. 71 The spectra were evaluated utilizing the relative populations of all computed SO states obtained by the Boltzmann equation.…”