Edward A. Boudreaux

An SC-MEH molecular orbital study of HCo (CO)4 and Co (CO)4

Abstract The Self Consistent Modified Extended Huckel (SC-MEH) molecular orbital method has been applied to the HCo(CO) 4 and Co(CO) 4 molecules. The results show that the highest occupied orbitals are predominantly ligand in character, which is at variance with other published calculations. Computation of the UV and photoelectron spectra, bond energy and some associated parameters, and magnetic hyperfine parameters of Co(CO) 4 have been carried out and found to be in exceptionally good agreement with experiment. The reported results also provide an acceptable rationalization for the observed photolysis and homolytic activity of the HCo(CO) 4 molecule.

Self consistent modified extended Hckel (SC-MEH) calculations on heavy metal systems. I. Platinum(II) tetragonal planar complexes with and without relativistic effects

The Self Consistent Modified Extended Hückel molecular orbital method had been applied to several square planar complexes of platinum (II). Calculations including both the limited 5d, 6s, 6p and extended 5s, 5p, 5d, 6s, 6p starting bases for platinum were made. It is shown that in PtCl42−both the nuclear quadrupole moment and minimum total energy vs. bond distance are calculated to be in good agreement with experiment, only with the extended platinum AO basis.Specific inclusion of relativistic parameters via a pseudo-relativistic approximation are shown to have a significant effect on the energy molecular energy levels, however no meaningful rationalization can be made without the simultaneous inclusion of ligand field parameters as well.

Charge transfer spectra in lanthanide-THD chelates

Abstract The near UV spectra of rare earth-THD chelates of the type, RE(THD)3 where THD = ButCOCHCOBut and RE = La, Pr, Nd, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb and Lu, have been measured and analyzed in terms of charge transfer. Observed spectra show a broad absorption maximum in the range of 33,000–36,000 cm−1 characteristic of all the chelates. Upon invoking an electrostatic charge-transfer model whereby the ligand non-bonding electrons are transferred to empty 5d orbitals of the RE, good agreement between observed and calculated spectra are obtained.

SCMEH-MO CALCULATIONS ON LANTHANIDE SYSTEMS V. A COMPARISON OF DFT AND SCMEH-MO METHODS ON ND(CO)6

Abstract Computations of electronic structure and bonding in the atypical lanthanide, Nd(CO) 6 , have been carried out via approximate SCMEH-MO and more sophisticated DFT methods. A comparison of these results shows SCMEH-MO data to be more consistent with chemical bonding of Nd and CO than are the DFT data. In fact, the DFT density matrix breaks symmetry during the execution of the routine. But it is not at all understood why the symmetry-breaking had occurred. Consequently, the DFT final MOs do not conform to those required by O h geometry. Over all, the NdCO bonding is weak and is not likely to promote pairing of four 4f electrons in one doubly degenerate MO, as shown in the DFT results.

MO calculations on extended clusters of YBa2Cu3O7

Molecular orbital studies of the electronic structure of bonding in Y Ba 2 Cu 8 O 26 + and Ba 2 Cu 8 O 26 − clusters of the high Tc superconductor, YBa 2 Cu 3 O 7 , have been carried out. The results show a distribution of single electrons and pairs over all occupied M.O.s. The single electrons are localized over O and Cu atoms in an approximate ratio of 19/4 respectively. An antiferromagnetic coupling of all spins to produce an open shell singlet state is anticipated