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Title: Experimental and Computational Studies of Alkali-Metal Coinage-Metal Clusters

Abstract

Coinage and alkali metal mixed clusters, M4Na- (M ) Cu, Au) have been investigated experimentally using photoelectron spectroscopy and computationally at correlated ab initio levels. The related Cu4Li-, Ag4 Li-, Ag4Na-, and Au4Li- clusters as well as the neutral Cu4Li2 and Cu4Na2 clusters have also been studied computationally. The calculations show that the two lowest isomers of the negatively charged clusters include a pyramidal C4V structure and a planar C2V species. For Cu4Li- and Cu4Na-, the C4V structure is calculated at correlated ab initio level to be 30.9 and 16.9 kJ/mol below the planar C2V isomer, whereas the planar isomers of Au4Li- and Au4Na- are found to be 29.7 and 49.4 kJ/mol below the pyramidal ones. For Ag4Li- and Ag4Na-, the pyramidal isomers are the lowest ones. Comparison of the calculated and measured photoelectron spectra of Cu4Na- and Au4Na- shows that the pyramidal Cu4Na- cluster of C4V symmetry and the planar Au4Na- of C2V symmetry are detected experimentally. Calculations of the magnetically induced current density in Cu4Li- and Cu4Li2 using the Gauge-Including Magnetically Induced Current (GIMIC) method show that strong ring currents are sustained mainly by the highest-occupied molecular orbital primarily derived from the Cu 4s. The GIMIC calculations thusmore » show that the Cu4 2- ring is ó-aromatic and that the d orbitals do not play any significant role for the electron delocalization effects. The present study does not support the notion that the square-planar Cu4 2- is the first example of d-orbital aromatic molecules.« less

Authors:
; ; ; ; ; ;
Publication Date:
Research Org.:
Pacific Northwest National Laboratory (PNNL), Richland, WA (US), Environmental Molecular Sciences Laboratory (EMSL)
Sponsoring Org.:
USDOE
OSTI Identifier:
882970
Report Number(s):
PNNL-SA-49550
3227a; KP1303000
DOE Contract Number:
AC05-76RL01830
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Physical Chemistry A, 110(12):4244-4250
Country of Publication:
United States
Language:
English
Subject:
Environmental Molecular Sciences Laboratory

Citation Formats

Lin, Ying-Chan, Sundholm, Dage, Juselius, Jonas, Cui, Lifeng, Li, Xi, Zhai, Hua-jin, and Wang, Lai S. Experimental and Computational Studies of Alkali-Metal Coinage-Metal Clusters. United States: N. p., 2006. Web. doi:10.1021/jp056789n.
Lin, Ying-Chan, Sundholm, Dage, Juselius, Jonas, Cui, Lifeng, Li, Xi, Zhai, Hua-jin, & Wang, Lai S. Experimental and Computational Studies of Alkali-Metal Coinage-Metal Clusters. United States. doi:10.1021/jp056789n.
Lin, Ying-Chan, Sundholm, Dage, Juselius, Jonas, Cui, Lifeng, Li, Xi, Zhai, Hua-jin, and Wang, Lai S. Thu . "Experimental and Computational Studies of Alkali-Metal Coinage-Metal Clusters". United States. doi:10.1021/jp056789n.
@article{osti_882970,
title = {Experimental and Computational Studies of Alkali-Metal Coinage-Metal Clusters},
author = {Lin, Ying-Chan and Sundholm, Dage and Juselius, Jonas and Cui, Lifeng and Li, Xi and Zhai, Hua-jin and Wang, Lai S.},
abstractNote = {Coinage and alkali metal mixed clusters, M4Na- (M ) Cu, Au) have been investigated experimentally using photoelectron spectroscopy and computationally at correlated ab initio levels. The related Cu4Li-, Ag4 Li-, Ag4Na-, and Au4Li- clusters as well as the neutral Cu4Li2 and Cu4Na2 clusters have also been studied computationally. The calculations show that the two lowest isomers of the negatively charged clusters include a pyramidal C4V structure and a planar C2V species. For Cu4Li- and Cu4Na-, the C4V structure is calculated at correlated ab initio level to be 30.9 and 16.9 kJ/mol below the planar C2V isomer, whereas the planar isomers of Au4Li- and Au4Na- are found to be 29.7 and 49.4 kJ/mol below the pyramidal ones. For Ag4Li- and Ag4Na-, the pyramidal isomers are the lowest ones. Comparison of the calculated and measured photoelectron spectra of Cu4Na- and Au4Na- shows that the pyramidal Cu4Na- cluster of C4V symmetry and the planar Au4Na- of C2V symmetry are detected experimentally. Calculations of the magnetically induced current density in Cu4Li- and Cu4Li2 using the Gauge-Including Magnetically Induced Current (GIMIC) method show that strong ring currents are sustained mainly by the highest-occupied molecular orbital primarily derived from the Cu 4s. The GIMIC calculations thus show that the Cu4 2- ring is ó-aromatic and that the d orbitals do not play any significant role for the electron delocalization effects. The present study does not support the notion that the square-planar Cu4 2- is the first example of d-orbital aromatic molecules.},
doi = {10.1021/jp056789n},
journal = {Journal of Physical Chemistry A, 110(12):4244-4250},
number = ,
volume = ,
place = {United States},
year = {Thu Mar 30 00:00:00 EST 2006},
month = {Thu Mar 30 00:00:00 EST 2006}
}
  • Ultraviolet photoelectron spectra (UPS) were recorded for mass-selected negative clusters of copper (1--411 atoms), silver (1--60 atoms), and gold (1--233 atoms), using photodetachment lasers at 6.4 and 7.9 eV photon energy. The results provide a direct estimate of the vertical electron affinity (EA) of these clusters and information on the evolution of the {ital d} bands of copper and gold as a function of cluster size. The large even/odd alternation of EA in small clusters of these metals in earlier work is found to largely disappear as the cluster size exceeds 40 atoms. The ellipsoidal shell model is shown tomore » be consistent with the observed EA behavior of all three metals, the predicted spherical shell closing at cluster 58 being evident for silver and gold. The UPS data show a smooth evolution of the {ital d} band toward that of the bulk metal.« less
  • The diphosphine ligand 1,2-bis(diphenylphosphino)benzene (dppbz) reacts with the activated cluster 1,2-Os{sub 3}(CO){sub 10}(MeCN){sub 2} (1) at room temperature to furnish a mixture of the triosmium clusters 1,2-Os{sub 3}(CO){sub 10}(dppbz) (2) and 1,1-Os{sub 3}(CO){sub 10}(dppbz) (3), along with a trace amount of the hydride cluster HOs{sub 3}(CO){sub 9}[{mu}-1,2-PhP(C{sub 6}H{sub 4}-{eta}{sup 1})C{sub 6}H{sub 4}PPh{sub 2}] (4). The dppbz-bridged cluster 2 forms as the kinetically controlled product and irreversibly transforms to the corresponding chelated isomer 3 at ambient temperature. The disposition of the dppbz ligand in 2 and 3 has been established by X-ray crystallography and {sup 31}P NMR spectroscopy, and the kineticsmore » for the conversion 2 {yields} 3 have been followed by UV-vis spectroscopy in toluene over the temperature range 318-343 K. The calculated activation parameters ({Delta}H{sub {+-}} = 21.6(3) kcal/mol; {Delta}S{sub {+-}} = -11(1) eu) and lack of CO inhibition support an intramolecular isomerization mechanism that involves the simultaneous migration of phosphine and CO groups about the cluster polyhedron. The reaction between 1 and the fluorinated diphosphine ligand 1,2-bis(diphenylphosphino)tetrafluorobenzene (dppbzF{sub 4}) was examined under similar reaction conditions and was found to afford the chelated cluster 1,1-Os{sub 3}(CO){sub 10}(dppbzF{sub 4}) (6) as the sole observable product. The absence of the expected bridged isomer 1,2-Os{sub 3}(CO){sub 10}(dppbzF{sub 4}) (5) suggests that the dppbzF{sub 4} ligand destabilizes 5, thus accounting for the rapid isomerization of 5 to 6. Near-UV irradiation of clusters 3 and 6 leads to CO loss and ortho metalation of an ancillary aryl group. The resulting hydride clusters 4 and HOs{sub 3}(CO){sub 9}[{mu}-1,2-PhP(C{sub 6}H{sub 4}-{eta}{sup 1})C{sub 6}F{sub 4}PPh{sub 2}] (7) have been isolated and fully characterized by spectroscopic and X-ray diffraction analyses. Both 4 and 7 react with added CO under mild conditions to regenerate 3 and 6, respectively, in quantitative yield. The rearrangements of bridged to chelated diphosphine complexes in this genre of decacarbonyl clusters have been investigated by DFT calculations. The computational results support a concerted process, involving the scrambling of equatorial CO and phosphine groups via a classical merry-go-round exchange scheme. The barriers computed for this mechanism agree well with those that have been measured, and steric compression within the bridged diphosphine groups of the reactants has been calculated to reduce the barrier heights for the rearrangement.« less
  • Here, computational studies of electrochemical reduction of CO 2 to CO, HCOOH and CH 4 were carried out using tetra-atomic transition metal clusters (Fe 4, Co 4, Ni 4, Cu 4 and Pt 4) at the B3LYP level of theory. Novel catalytic properties were discovered for these subnanometer clusters, suggesting that they may be good candidate materials for CO 2 reduction. The calculated overpotentials of producing CH 4 are in the order: Co 4 < Fe 4 < Ni 4 < Cu 4 < Pt 4 with both Co 4 and Fe 4 having overpotentials less than 1 V. Investigationmore » of the effects of supports found that a Cu 4 cluster on a graphene defect site has a limiting potential for producing CH 4 comparable to that of a Cu (111) surface. However, due to the strong electronic interaction with the Cu 4 cluster, the defective graphene support has the advantage of significantly increasing the limiting potentials for the reactions competing with CH 4, such as the hydrogen evolution reaction (HER), and CO production.« less