Structural, electronic, and magnetoresponsive properties of triangular lanthanide clusters and their free-standing nitrides.
The molecular and electronic structures, stabilities, bonding features, and magnetoresponsive properties of three-membered [c-Ln(3)](+/0/-) (Ln = La, Ce, Pr, Nd, Gd, Lu) and heterocyclic six-membered [c-Ln(3)E(3)](q) (Ln = La, Ce, Pr, Nd, Gd, Lu; E = C, N; q = 0 or 1) rings have been investigated by means of electronic structure calculation methods at the DFT level. The [c-Ln(3)](+/0/-) clusters are predicted to be bound with respect to dissociation to their constituent atoms, the estimated binding energies ranging from 45.8 to 2056.4 kJ/mol. The [c-Ln(3)] rings capture easily a planar three-coordinated nitrogen atom at the center or above the center of the ring yielding the lanthanide nitride clusters [c-Ln(3)(μ(3)-N)] adopting a planar geometry, except [c-La(3)(μ(3)-N)] which exhibits pyramidal geometry. The [c-Ln(3)(μ(3)-N)] clusters are predicted to be bound, with respect to dissociation to N ((4)S) atom and [c-Ln(3)] clusters in their ground states, the binding energies ranging from 53.9 to 257.9 kcal/mol. The six-membered [c-Ln(3)E(3)](q) rings are predicted to be bound with respect to dissociation to LnE(q) monomers in their ground states with dissociation energies in the range of 173.8 to 318.0 kcal/mol. Calculation of the NICS(zz)-scan curves of the clusters predicted a "hermaphrodic" magnetic response of the [c-Ln(3)](+/0/-) and heterocyclic six-membered [c-Ln(3)E(3)](q) rings, manifested by the coexistence of successive diatropic (aromatic) and paratropic (antiaromatic) zones. The [c-La(3)](+/0/-) and [c-Lu(3)](-) are predicted to be weakly antiaromatic, the [c-Lu(3)](0/+), [c-Lu(3)C(3) ](+), and [c-Lu(3)N(3)] double (σ+π) aromatic, and the [c-Gd(3)C(3)] and [c-Gd(3)N(3)](+) rings (σ+δ)-aromatic systems.
Tsipis
Athanassios C
AC
Laboratory of Inorganic and General Chemistry, Department of Chemistry, University of Ioannina, 451 10 Ioannina, Greece. attsipis@uoi.gr
Stalikas
Alexandros V
AV