Manipulating surface diffusion ability of single molecules by scanning tunneling microscopy.

The bonding of single diferrocene [Fc(CH(2))(14)Fc, Fc = ferrocenyl] molecules on a metal surface can be enhanced by partial decomposition of Fc groups induced by the tunneling current in scanning tunneling microscopy. Although the isolated intact molecule is mobile on the terrace of Cu(110) at 78 K, the modified molecule is immobilized on the terrace. Calculations based on density functional theory indicate that the hollow site of the Cu(110) surface is the energetically favorable adsorption site for both ferrocene and the Fe-cyclopentadienyl complex, but the latter one possesses a much higher binding energy with the substrate.

Patterned nucleation control in vacuum deposition of organic molecules.

We report a generally applicable method to pattern organic molecules on mesoscopic scales. In our method, organic molecular beam deposition was conducted on substrate surfaces prepatterned with materials to which the organic molecules have larger binding energies in comparison to the substrate. Fully uniform nucleation control at these predefined locations can be achieved by an appropriate selection of the growth parameters including temperature and deposition rate. The physical mechanisms involved are studied by Monte Carlo simulations and stand in good agreement with the experimental findings.

Homogeneous single-component betaine Ziegler-Natta catalysts derived from (butadiene)zirconocene precursors.

(Butadiene)zirconocene adds B(C(6)F(5))(3) at a terminal diene carbon atom to yield the zirconocene-(mu-hydrocarbyl)-borate betaine Cp(2)Zr[C(4)H(6)-B(C(6)F(5))(3)] (4). The dipolar complex 4 contains a distorted pi-allyl moiety and features an additional stabilizing Zr-F-C(arene) coordination. Under kinetic control, an isomeric betaine system is formed, characterized by an internal Zr(+).CH(2)[B](-) ion-pair interaction, that rearranges to 4 upon heating. A great variety of ansa-metallocene(butadiene) complexes and related systems cleanly form analogous metallocene-(mu-conjugated diene)-borate betaines upon treatment with B(C(6)F(5))(3) and related Lewis acids. Most of these systems represent very active homogeneous single-component Ziegler-Natta catalysts for alpha-olefin polymerization and copolymerization. In addition, these betaine catalysts are ideally suited for carrying out mechanistic studies in active Ziegler-Natta catalyst systems. They allow for an experimental observation of the first alkene insertion step at the active single-component catalyst. This feature has been used for studying the mechanism of transfer of the stereochemical information from the bent metallocene backbone and for an experimental characterization of the energy profile of the alkene addition/alkene insertion reaction sequence in active homogeneous Ziegler-Natta systems. The neutral dipolar single-component catalysts (e.g., 4) produce a polyolefin-modified R'-(CHR-CH(2))-C(4)H(6)-B(C(6)F(5))(3)(-) counterion at the end of the initiation period upon entering into the repetitive active catalytic cycle.

(N-pyrrolyl)B(C6F5)2--a new organometallic Lewis acid for the generation of group 4 metallocene cation complexes.

Treatment of the (C6F5)2BF x OEt2 (3) complex with N-pyrrolyl lithium gives bis(pentafluorophenyl)(N-pyrrolyl)borane (2), a strong organometallic Lewis acid, which was characterized by X-ray diffraction (B-N bond length: 1.401(5) A). It exhibits a columnar superstructure in the crystal and contains pi-stacks of pyrrolyl units. Compound 2 readily abstracts alkyl anions from a variety of alkyl Group 4 metallocene-type complexes and leads to the clean formation of the respective metallocene ions or ion pairs. For example, the treatment of Cp3ZrCH3 (9) with 2 transfers a methyl anion to yield the ion pair [Cp3Zr]+[(C4H4N)B(CH3)(C6F5)2]- (12). The X-ray crystal structure analysis of 12 shows a close contact between zirconium and the pyrrolyl-beta-carbon (2.641(2) A). The borane 2 adds to (butadiene)zirconocene (13) to yield the betaine system [Cp2Zr]+[(C4H6)B- (NC4H4)(C6F)2]- (15). Complex 15 contains a distorted eta3-allyl moiety inside the metallacyclic framework and it features an internal Zr+...(pyrrolyl)B- ion pair interaction with a Zr...pyrrolyl-alphacarbon separation of 2.723(3) A (determined by X-ray diffraction). From the dynamic NMR spectra of 15 the bond strength of the internal ion pair interaction was estimated to be deltaGdiss (223 K) approximately = to15 kcalmol(-1). Treatment of dimethylzirconocene (16) with 2 yields the metallocene borate salt [Cp2ZrCH3]+[(C4H4N)B(CH3)(C6F5)2]- (17), which is an active catalyst for the polymerization of ethene.

Treatment of Naphthols with B(C(6)F(5))(3): Formation and Characterization of the Lewis Acid Adducts of Their Keto Isomers.

With the strong Lewis acid B(C(6)F(5))(3), the keto tautomers from a variety of naphthol derivatives are obtained (e.g. alpha-naphthol, see scheme). The adducts of the tautomers were characterized by X-ray structure analysis, and the first attempts at hydrozirconation of the adducts were made.

Patterns of neuropsychological functioning among patients with multi-infarct and Alzheimer's dementia: a comparative analysis.

Cognitive and neuropsychological tests are often employed to help describe the functioning of patients with multi-infarct dementia (MID) or patients with dementia of the Alzheimer's type (DAT). In this study, the Halstead-Reitan Neuropsychological Battery (HRNB), Wechsler Adult Intelligence Scale-Revised (WAIS-R), and Wechsler Memory Scale (WMS) were completed by 20 MID patients and 62 patients with DAT. Total scores on these measures did not differentiate DAT and MID patients. Contrary to clinical observations, cognitive tasks assessing social judgment did not differentiate between the groups. However, MID patients demonstrated greater variability in test scores. Compared with DAT patients, the MID patients demonstrated better preserved memory as shown on the WMS in comparison to the WAIS-R IQ.

Residential versus day treatment for children: a long-term follow-up study.

Adults and adolescents, who as children, received day or residential treatment were followed up ten years after treatment completion. No differences were found between the two treatment modalities on follow-up ratings of personal and social adjustment. This pattern was not influenced by gender, IQ, or presenting problem. Overall, about two-thirds of the children demonstrated improvement at follow-up. As expected, individuals demonstrating higher levels of personal and social adjustment at initial assessment were functioning better at outcome. However, the magnitude of therapeutic gain was not significantly different for mild versus moderate-to-severe presenting problems. Suggestions for future research are included.

Application of the Trail Making Test in differentiating neuropsychological impairment of elderly persons.

This study investigated differences in Trail Making Test performance as a function of over-all level of neuropsychological impairment in a sample of elderly patients diagnosed as having various dementing diseases. Patients were classified as mildly, moderately, or severely impaired (ns = 19, 25, 26) based on the seven measures used to compute the Impairment Index of the Halstead-Reitan Neuropsychological Battery. The mean ages for the mildly, moderately, and severely impaired groups were 67.72, 71.56, and 71.16 yr., respectively. Using level of impairment as the grouping variable, subjects were compared on the mean number of seconds required to complete Trail Making Test A, B, and A + B. Three one-way analyses of variance indicated significant differences for Parts A, B, and A + B. As over-all level of impairment increased, time required to complete the Trail Making Test increased. Results are discussed and directions for further research are recommended.