X-ray spectral data and self-consistent field-Xa-scattered wave (SCF-Xa-SW) calculations are presented for D4h and D u CuC12in order to evaluate specific contributions to the small hyperfine in distorted tetrahedral copper sites and to compare the mechanism of hyperfine reduction in these complexes with that for the blue copper site in plastocyanin. Comparison of the 2p3,2 XPS data for the two geometries indicates that the extent of delocalization of the d,z+ ground state in the D u salt is slightly less than in the D4h complex. Multiplet splitting of satellite structure from Cu 3s photoemission shows no change going from D4h to D u CuCIz-, indicating that the indirect Fermi contact contribution to the hyperfine from the core Cu 3s level does not change between the two complexes. Analysis of X-ray edge data for Cs2CuC14 ( D u ) indicates that there is at most 5.8% 4p, mixed into the ground-state wave function, an amount that is insufficient to explain the reduced hyperfine in this distorted Td complex. SCF-Xa-SW calculations performed with sphere radii adjusted so that the ground-state wave function fits the experimental g values indicate that -70% of the reduction in All between D4h and D2d comes from increased orbital angular momentum in the ground state of the Du salt arising from decreased ligand field transition energies. In contrast, increased delocalization relative to D4h CUCI,~accounts for most of the reduction in the blue copper proteins. The remaining 30% of the reduction in All is associated with a -50 X lo4 cm-I reduction in Fermi contact between the two salts. Xa calculations of a number of Cu complexes with < D u symmetry indicate that this reduction is not associated with direct 4s mixing into the half-occupied ground state but is most likely due to increased polarization of the filled totally symmetric valence levels in DZd CuCI," resulting from increased 4s mixing as compared with D,,, CuCIt-. These studies are then extended to include copper sites exhibiting rhombically split g and A values. Single-crystal optical and EPR studies on copper-doped bis( 1,2-dimethylimidazole)zinc(II) dichloride (Zn[Cu] (dmi),C12) combined with ligand field and SCF-Xa-SW calculations indicate that the rhombic features in these complexes can be explained through admixture of -3% d,z character in the ground-state wave function. Finally, the structurally uncharacterized blue copper protein stellacyanin, which also shows a rhombic EPR spectrum similar to that in Zn[C~](dmi)~Cl~, is considered. In contrast to the C, effective symmetry found in the structurally defined site in plastocyanin, stellacyanin is predicted to have C, effective symmetry. A ligand field calculation using the plastocyanin site as a starting point indicates that stellacyanin requires a stronger field ligand along the Cu-methionine coordinate to produce the observed dzz mixing.

Copper has been evaporated onto chemically different single-crystal surfaces of zinc oxide in ultrahigh vacuum to model Cu/ZnO methanol synthesis catalysts. The formation of the copper overlayers from less than 0.1 monolayer (ML) to several ML on the (0001), (0001), and (10 0) surface planes is followed with core-level X-ray photoelectron spectroscopy, valence band photoelectron spectroscopy with both resonance discharge sources and synchrotron radiation, and low-energy electron diffraction. At room temperature, the first monolayer grows in a two-dimensional fashion, with low coverage copper existing as isolated atoms/small islands on all surfaces. Surface perturbations show submonolayer copper supported on the Zn2+-terminated (0001) surface to be most prone to high-temperature clustering and reaction with molecular oxygen. Copper on the oxide-terminated (0001) surface is much less reactive, while copper on the (1010) dimer surface shows intermediate reactivity. Low-temperature carbon monoxide (CO) chemisorption experiments indicate that highly dispersed copper on the (0001) and (lOTO) surfaces chemisorb CO with approximately the same affinity as copper metal (A/fads = 15-16 kcal/mol), while chemisorption on Cu/(0001) was much weaker (A/7ads < 12 kcal/mol). High-affinity (A7/ads = 21 kcal/mol) CO chemisorption, often associated with the catalytic active site, is shown to occur at a coordinatively unsaturated tetrahedral Cu+ site created on the (0001) surface upon annealing in oxygen. Chemisorption to the Cu+ site perturbs the CO electronic structure to a much greater extent than chemisorption to either Cu°or Zn2+, with valence band PES indicating both strong and 7 interactions. The implications of these results with respect to CO activation and the catalytic activity of the Cu/ZnO system are discussed.with Cu/ZnO as compared to ~30 kcal/mol on ZnO.8 Metallic copper is reported to show no measurable activity.8,9 Additionally, a significant amount of CO chemisorbs to the Cu-promoted catalyst more strongly than to either Cu or ZnO, indicating that the Cu/ZnO combination contains a detectable number of surface

Low-temperature (7 K) polarized single-crystal absorption and room-temperature polarized specular reflectance spectra have been obtained of the chloride-to-copper charge-transfer region of the three known square-planar salts of CuCl42", bis(methadonium) tetrachlorocuprate(II), bis(TV-methylphenethylammonium) tetrachlorocuprate(II), and bis(creatinium) tetrachlorocuprate(II) and of the tetragonal monomer, bis(ethylammonium) tetrachlorocuprate(II). These spectra show two intense, x-y polarized, x-y split transitions in the regions 26000-28 000 and 37 000-39 000 cm"1. These bands are assigned to the allowed 2EU *-2Blg (4eu(ir) -3blg) and 2EU <-2Blg (3 "( ) -3blg) transitions, respectively. In addition, a weaker band is observed between 22000 and 25000 cm'1 and has been assigned to the 2A2g 2Blg (la2g(nb) -3blg) transition. These assignments are compared to the results of SCF-Xa-SW ground-and transition-state calculations; although the calculated transition energies are too low and there is overlap of the calculated d-d and charge-transfer manifolds of states (in contrast to the clean separations observed experimentally), the differences between the calculated energies of the three charge-transfer transitions agree well with those observed experimentally. The assignment is also supported by He(II) ultraviolet photoelectron spectroscopic data on single crystals of (C2H5NH3)2CuCl4 and (CH3NH3)2CuC14. In light of these assignments for the square planar (Dih) CuCl42" ion, the charge-transfer spectrum of the flattened tetrahedral (Om) CuCl42" ion has been reassigned (the tetrahedral parentage of the excited state is indicated in parentheses): 22 700 cm"1 (sh), 2A2(2Thnb) <-2B2(2T2); 24730 cm"1, 2E(2T,,nb) -2B2(2T2); 28 880 cm"1 (sh), 2E(2T2,t) -2B2(2T2); 33480 cm"1, 2E(2T2,

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The development of a group of 100 preterm infants, mean birth weight 1,877 grams, from a broad range of social class and ethnic backgrounds was followed from birth to age 5. Assessments in infancy were directed at medical problems and early perceptual, motor, social, and cognitive development. The child's performance on the Stanford-Binet test at age 5 could not be predicted from early hazardous events in the obstetrical or neonatal period. The results indicate that developmental outcome at age 5 could be predicted moderately from a single measure, infant visual attention, administered as early as term date. Prediction was improved by using a combination of assessments given during the first 9 months. Furthermore, prediction was significantly better for girls than for boys. Although moderate stability in performance was found for the group as a whole, prediction of an individual's performance resulted in a substantial number of children being misclassified. Social factors were more important than any other set of factors in relating to the child's mental performance at age 5.