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The magnetic interactions in Mn(II)(hfac)2{di(4-pyridyl)phenylcarbene}(1a) and Cu(II)(hfac)2{di(4-pyridyl)phenylcarbene}(2a) are studied. The two complexes are regarded as the new d-pi-p conjugated systems containing transition metal ion and carbene as spin sources.

Previously, we have performed the spin-polarized hybrid-density functional theory (HUDFT) calculations for elucidating magnetic properties of the two-dimensional (2D) K2NiF4 and K2CuF4 solids. In Part I, it has been concluded that the half-and-half-(HH-) type HUDFT method is one of the best calculation methods for these species. On the other hand, in Part II, we have demonstrated that potential curves for cluster models of K2CuF4 and KCuF3 are reasonably calculated by the HH-type HUDFT method under the approximate spin projection, and the lattice distortion resulted by Jahn-Teller effect is expressed as the second-order polynomial. In this study, we pay attention to the three-dimensional (3D) magnetic interactions in KNiF3. Our effective exchange integral Jab schemes for 3D cluster models such as KNi8F12 (4) with and without point charges have provided the reasonable Jab values (-30.24–34.48 cm-1), in comparison with the experimental one (-30.58 cm-1). The 3D magnetic interactions have been investigated from viewpoints of the Mulliken spin density and charge density populations, the natural orbital analysis, and chemical indices. Point charges located in positions of fluorine anion adjacent to cluster model have reproduced Jab values well. Roles of potassium as counter cation in KNiF3 solid were also investigated. It was concluded that potassium has a role of stabilizing the 3D magnetic structures. Finally, the mutual relationships between broken-symmetry and symmetry-adapted approaches are discussed on the basis of chemical indices. © 2004 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Previously, various symmetry-adapted (SA) and broken-symmetry (BS) computations have been performed for strongly correlated transition metal species so as to examine magnetic properties in simple cluster models such as binuclear transition metal oxides. Though SA computations such as the complete active space configuration interaction and CASSCF are desirable for estimating physical constants, these computations are heavy for larger cluster models with strongly correlated electrons. K[SUB2]NiF[SUB4] is known to be the two-dimensional perovskite-type antiferromagnet and to have the electronic configuration similar to that of La[SUB2]CuO[SUB4]. Here, we have examined the utility and applicability of the BS spin-polarized hybrid-density functional theory (HUDFT) for cluster models of K[SUB2]NiF[SUB4]. As the result, HUDFT calculation such as UB2LYP has provided the reasonable effective exchange integral (J[SUBab]) followed by our approximately spin projected scheme, in comparison to the experimental one. It was also found that the square planar tetranuclear model has provided the most reasonable J[SUBab] value by HUDFT. In addition, external effects such as putting point charges around cluster models and changing distances between nickel and fluorine have been also examined. The natural orbital analysis by HUDFT has been carried out to obtain natural orbitals and their occupation numbers. Charge density, spin density, and chemical indices expressed by the occupation numbers have been also obtained to elucidate the nature of the chemical bonds in the K[SUB2]NiF[SUB4]-type solids. [ABSTRACT FROM AUTHOR]

Helium Covalency Chemical bonding rule Dimer Cubic structure In order to investigate the helium covalency, molecular orbital calculations were performed for helium dimer and helium-containing La2/3-xLi3xTiO3 perovskite and HeC8 cube. There were orbital overlap between helium 1s orbitals in helium dimer. In HeTi8O12 and HeC8 models, helium had orbital overlap with oxygen and carbon, respectively. From chemical bonding rule, it was concluded that helium can form covalent bonding with oxygen and carbon. [ABSTRACT FROM AUTHOR]