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Title: Electronic Structure of a Metal-Organic Copper Spin-1/2 Molecule: Bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(ll)

Abstract

The metal-organic molecule bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (Cu(CNdpm){sub 2}) (C{sub 24}H{sub 36}N{sub 2}O{sub 4}Cu, Cu(II)) is a copper spin-1/2 system with a magnetic moment of 1.05 {+-} 0.04 {mu}{sub B}/molecule, slightly smaller than the 1.215 {+-} 0.02 {mu}{sub B}/molecule for the larger size copper spin-1/2 system C{sub 36}H{sub 48}N{sub 4}O{sub 4}Cu-C{sub 4}H{sub 8}O (bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) 4,4'-bipyridylethene-THF). There is generally good agreement between photoemission from vapor-deposited thin films of the C{sub 24}H{sub 36}N{sub 2}O{sub 4}Cu on Cu(111) and Co(111) and model calculations. Although this molecule is expected to have a gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, the molecule remains surprisingly well screened in the photoemission final state.

Authors:
; ; ; ; ; ; ; ; ;
Publication Date:
Research Org.:
Brookhaven National Laboratory (BNL) National Synchrotron Light Source
Sponsoring Org.:
Doe - Office Of Science
OSTI Identifier:
929887
Report Number(s):
BNL-80466-2008-JA
Journal ID: ISSN 0002-7863; JACSAT; TRN: US200822%%927
DOE Contract Number:
DE-AC02-98CH10886
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of the American Chemical Society; Journal Volume: 129
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; COPPER COMPOUNDS; ORGANOMETALLIC COMPOUNDS; ELECTRONIC STRUCTURE; MAGNETIC MOMENTS; THIN FILMS; national synchrotron light source

Citation Formats

Wisbey,D., Feng, D., Bremer, M., Borca, C., Caruso, A., Silvernail, C., Belot, J., Vescovo, E., Ranno, L., and Dowben, P. Electronic Structure of a Metal-Organic Copper Spin-1/2 Molecule: Bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(ll). United States: N. p., 2007. Web. doi:10.1021/ja069236e.
Wisbey,D., Feng, D., Bremer, M., Borca, C., Caruso, A., Silvernail, C., Belot, J., Vescovo, E., Ranno, L., & Dowben, P. Electronic Structure of a Metal-Organic Copper Spin-1/2 Molecule: Bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(ll). United States. doi:10.1021/ja069236e.
Wisbey,D., Feng, D., Bremer, M., Borca, C., Caruso, A., Silvernail, C., Belot, J., Vescovo, E., Ranno, L., and Dowben, P. Mon . "Electronic Structure of a Metal-Organic Copper Spin-1/2 Molecule: Bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(ll)". United States. doi:10.1021/ja069236e.
@article{osti_929887,
title = {Electronic Structure of a Metal-Organic Copper Spin-1/2 Molecule: Bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(ll)},
author = {Wisbey,D. and Feng, D. and Bremer, M. and Borca, C. and Caruso, A. and Silvernail, C. and Belot, J. and Vescovo, E. and Ranno, L. and Dowben, P.},
abstractNote = {The metal-organic molecule bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) (Cu(CNdpm){sub 2}) (C{sub 24}H{sub 36}N{sub 2}O{sub 4}Cu, Cu(II)) is a copper spin-1/2 system with a magnetic moment of 1.05 {+-} 0.04 {mu}{sub B}/molecule, slightly smaller than the 1.215 {+-} 0.02 {mu}{sub B}/molecule for the larger size copper spin-1/2 system C{sub 36}H{sub 48}N{sub 4}O{sub 4}Cu-C{sub 4}H{sub 8}O (bis(4-cyano-2,2,6,6-tetramethyl-3,5-heptanedionato)copper(II) 4,4'-bipyridylethene-THF). There is generally good agreement between photoemission from vapor-deposited thin films of the C{sub 24}H{sub 36}N{sub 2}O{sub 4}Cu on Cu(111) and Co(111) and model calculations. Although this molecule is expected to have a gap between the highest occupied molecular orbital and the lowest unoccupied molecular orbital, the molecule remains surprisingly well screened in the photoemission final state.},
doi = {10.1021/ja069236e},
journal = {Journal of the American Chemical Society},
number = ,
volume = 129,
place = {United States},
year = {Mon Jan 01 00:00:00 EST 2007},
month = {Mon Jan 01 00:00:00 EST 2007}
}
  • The title compounds (UO/sub 2/(HFA)/sub 2/ and UO/sub 2/(THD)/sub 2/) were found to exist in the gaseous phase as partly dissociated dimers, although UO/sub 2/(HFA)/sub 2/ has previously been shown to be trimeric in the solid state. The enthalpy and entropy changes associated with the dimerization equilibria were determined as ..delta..H/sup 0/ = -48.2 +- 0.6 kJ mol/sup -1/ and ..delta..S = -119 +- 13 J K/sup -1/ mol/sup -1/ for UO/sub 2/(HFA)/sub 2/ and ..delta..H/sup 0/ = -74.5 +- 0.5 kJ mol/sup -1/ and ..delta..S/sup 0/ = -176 +- 12 J K/sup -1/ mol/sup -1/ for UO/sub 2/(THD)/sub 2/.more » The heats of sublimation (..delta..H/sub sub/) were determined as 147 +- 4 kJ mol/sup -1/ for UO/sub 2/(HFA)/sub 2/ and 126 +- 9 kJ mol/sup -1/ for UO/sub 2/(THD)/sub 2/.« less
  • We report the growth of c-axis oriented ZnO films on silicon (100) single crystal substrates by MOCVD. A relatively uninvestigated precursor, Zn(TMHD)2, was used in a cold-wall MOCVD reactor. XPS and RBS analysis yielded a zinc-to-oxygen atom percent ratio of 0.98 and 1.00 at the surface and in the overall film, respectively indicative of stoichometric ZnO. Due to the presence of carbon at the surface, the excess oxygen at the surface was in the form of C-O bonding. The c-axis orientation was confirmed by HRTEM and XRD. We look at these results from a viewpoint of an ongoing effort tomore » ensure cleaner decompositions using Zn(TMHD)2.« less
  • We have used the relatively uninvestigated Zn(TMHD)2 precursor to grow highly c-axis oriented ZnO films on Si(100). X-ray photoelectron spectroscopy studies before and after Ar ion sputtering indicate that surface carbon was reduced from 21 at. % to much less than 1 at. % within the first 5 nm, indicating very clean Zn(TMHD)2 precursor decomposition. Microstructural and compositional analysis reveal columnar ZnO grains with domain widths of approximately half the total film thickness and a Zn-to-O atom percent ratio indicative of stoichometric ZnO.
  • Reactions of cis-(DTHp)W(CO)/sub 4/, in which DTHp forms a four-membered chelate ring, with L (DTHp = 2,2,6,6-tetramethyl-3,5-dithiaheptane; L = P(OMe)/sub 3/, P(O-i-Pr)/sub 3/, P(OCH/sub 2/)/sub 3/CCH/sub 3/, P(n-Bu)/sub 3/) in chlorobenzene (CB) proceed via displacement of DTHp according to cis-(DTHp)W(CO)/sub 4/ + 2L ..-->.. cis- and trans-(L)/sub 2/W(CO)/sub 4/ + DTHp. Kinetics data in CB indicate the reaction to be biphasic, with cis-(L)(/eta//sup 1/-DTHp)W(CO)/sub 4/ present as a predominant species during the reaction's course; this intermediate has been characterized for L = P(COH/sub 2/)/sub 3/ CCH/sub 3/. Evidence here suggests that significant L-W bond making takes place in the transitionmore » states leading to chelate ring opening and closing. The cis-(L)(/eta//sup 1/-DTHp)W(CO)/sub 4/ products produced via the first phase of the biphasic thermal process undergo unimolecular W-S bond fission. Rate constants for this process vary significantly and are largely influenced by the steric properties of coordinated L, increasing in the order of larger Tolan cone angles. This W-S bond dissociation is followed by solvation to afford cis-((CB)(L)W(CO)/sub 4/) intermediates, previously characterized, which then react via rapid reversible desolvation and attack at the five-coordinate, square-pyramidal ((L)W(CO)/sub 4/) intermediates by L, to afford cis-(L)/sub 2/W(CO)/sub 4/. Subsequent nondissociative isomerization of this species forms the equilibrium mixture of cis- and trans-(L)/sub 2/W(CO)/sub 4/ products ultimately obtained. These several steps involved in the overall chelate displacement process are discussed in detail. 25 references, 4 figures, 2 tables.« less