Bonding Nature and Electron Delocalization of An(COT)₂, An = Th, Pa, U

Abstract

A systematic study of a series of An(COT)(2) compounds, where An = Th, Pa, U, and COT represents cyclooctatetraene, has been performed using relativistic density functional theory. The ZORA Hamiltonian was applied for the inclusion of relativistic effects, taking into account all of the electrons for the optimization and explicitly including spin-orbit coupling effects. Time-dependent density functional theory (TDDFT) was used to calculate the excitation energies with the GGA SAOP functional, and the electronic transitions were analyzed using double group irreducible representations. The calculated excitation energies are in perfect correlation with the increment of the ring delocalization as it increases along the actinide series. These results are sufficient to ensure that, for these complexes, the increment in delocalization, as indicated by ELF bifurcation and NICS analysis, leads to a shift in the maximum wavelength of absorption in the visible region. Also, delocalization in the COT ring increases along the actinide series, so the systems become more aromatic because of a modulation induced by the actinides.

Prediction of a Nine−Membered Aromatic Heterocyclic 1,4,7−triazacyclononatetraenyl anion and its Sandwich Complexes with Divalent Lanthanides

“…It is noteworthy to mention that although the planarity of the ligands decreases in their Ln@(tacn−TT) complexes but their HOMA value is increased from 0.83 to 0.83−0.89. In addition the significantly high NICS values (in the range of −18 to −42) show that the aromaticity of trans ligand is significantly high in these Ln@(tacn−TT) complexes similar to that observed in the Ln(COT) 2 complexes. The torsional angle between two ligands in Ln(tacn−CC) is calculated to be around 178−180 degree, while it is observed to be around 93−95 degree in Ln(tacn−TT) complexes.…”

“…Moreover, variation of ligand field can modify the optical properties of complexes by tuning 5d−4 f transition. A very few sandwich complexes with a nine member ring have been studied till date, however five, six or eight member ring ligands have been widely used to form various sandwich complexes In particular, neutral and linear sandwich complexes of lanthanides with a nine−membered ligand is very rare in the literature .…”

Advances in bonding and properties of inorganic systems from relativistic calculations in Latin America

“…The analysis of the bonding nature and electron delocalization of several lanthanides An(COT) 2 , An = Th, Pa, U, and [M(C 8 H 8 ) 2 ] and M(C 5 H 5 )(C 8 H 8 ); M = Ti, Zr, Hf, and Th . For the bis(dicyclooctatetraenyl)diuranium complex studied in two symmetries ( D 2h and C 2 ), the optical and magnetic properties have been accounted for by Paez‐Hernandez, showing that for both symmetries the preferred ground state of the complex is a quintuplet spin state denoting significant ferromagnetic coupling between the metal centers …”

RELATIVISTIC-DFT STUDY OF THE ELECTRONIC STRUCTURE, BONDING AND ENERGETIC OF THE [ReF8]־ AND [UF8]2- IONS

“…3 . Despite of this, some hepta-and octa-coordinated compounds were synthetized since 1940, we can cite some examples of these high coordination compounds, such as, the homoleptic hepta-coordinated systems of Zr, Tb and U reported by W. H. Zachariasen (1949 [4][5][6] , the lanthanide hepta-fluoride systems synthetized by R. Hoppe et.al. (1961) 7,8 and also some inorganic compounds with coordination number of eight obtained by K. Seppelt and co-workers.…”

“…[1][2][3][4][5][6] Under all considerations made before, we performed a systematic study of the octacoordinated compounds, [ [7][8][9] , in order to elucidate their electronic structure, the energetic and the nature of bonding between the fluoride ligands and the heavy transition metal or actinide center by taking into account the relevant importance of the relativistic effects (scalar and spin-orbit coupling). In this work we expect to contribute towards the understanding of the chemistry of heavy transition metal and actinide complexes.…”