the study of noble gas – noble metal halide interactions: fourier transform microwave spectroscopy...
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The Study of Noble Gas – Noble Metal Halide Interactions: Fourier Transform Microwave Spectroscopy of XeCuCl
Julie M. Michaud and Michael C. L. GerryUniversity of British Columbia, Vancouver, BC Canada
June 2005
International Symposium on Molecular Spectroscopy
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XeCuClAnticipated properties: Short Xe-Cu bond length; Small centrifugal distortion constant; Large changes in nuclear quadrupole
coupling constants (131Xe, Cu and Cl) on bond formation;
Significant theoretical evidence of strong interactions between the Xe and Cu atoms in XeCuCl.
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132Xe63Cu35Cl Spectrum
Natural abundance:14.1%
I(63Cu) = 3/2
I(35Cl) = 3/2
Total of 10 transitionsin this one spectrum
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131Xe63Cu35Cl Spectrum
Natural abundance: 11.1%
I(131Xe) = 3/2
I(63Cu) = 3/2
I(35Cl) = 3/2
Total of 15 transitionsin this one spectrum
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Representative Spectroscopic Constants
Parameter 129Xe63Cu35Cl 131Xe63Cu35Cl 132Xe63Cu35Cl
Bo /MHz 757.30669(9) 753.0300(2) 750.93467(5)
DJ /kHz 0.0794(7) 0.104(2) 0.0782(4)
eQq(Cu) /MHz 41.81(9) 41.6(1) 41.57(6)
eQq(Cl) /MHz -26.10(6) -26.4(1) -26.01(4)
eQq(131Xe) /MHz - -81.4(2) -
eQq(63Cu) /MHz = 16.17 eQq(35Cl) /MHz = -32.1
Nuclear quadrupole coupling constants of the CuCl monomer:
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Xe-Cu bond lengths in XeCuCl
Experimental rm(2)(Xe-Cu) = 2.4669(4) Å
MP2 results r(Xe-Cu) = 2.497 Å a
van der Waals limit:
Covalent limit:
a Lovallo, C. C.; Klobukowski, M. Chem. Phys. Lett. 2002, 368, 589.b Pyykkö, P. Chem. Rev. 1997, 97, 597.c Huheey, J. E. et al. Inorganic Chemistry, Principles of Structure and Reactivity, 4th Ed.; Harper-Collins: New York, 1993.d Bartlett, N et al. In Comprehensive Inorganic Chemistry; Bailar, J. C. et al. Eds.;Pergamon:Oxford, 1973; 213-330.e Pyykkö, P. Chem. Rev. 1988, 88, 579.
(rvdW(Xe)b + rion(Cu+)c) = 2.78 Å
(rcov(Xe)d + rcov(Cu(I))e) = 2.36 Å
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Centrifugal Distortion Constants
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o
J
BD
k
2
1
Small centrifugal distortion constants Highly rigid molecules
DJ
/kHz X 102
k(Ng-M) /Nm-1
XeCuF 20 94
XeAuF 7 137
ArAgCl 35 34
Ar-NaCla 900 0.6
a Mizoguchi, A.; Endo, Y.; Ohshima, Y. J. Chem. Phys. 1998, 109, 10539.
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Nuclear Quadrupole Coupling Constants (MHz) for 131Xe
131Xe 0131Xe-Ara 0.723
131Xe-HClb -4.9131Xe63CuX -81.4 to -87.8
131Xe107AgXc -78.1 to -82.8131XeAuFd -134.5131XeH+ e -369.5
131Xe [Kr]5s24d105p56s1 f -505
a Xu, Y. et al. JCP, 1993, 99, 919. b Keenan, M. R. et al. JCP, 1980, 73(8), 3523.c Cooke, S.A. et al. PCCP, 2004, 6, 3248. d Cooke S.A. et al. JACS, 2004, 126, 17000. e Kellö, V. et al. Chem. Phys. Lett., 2001, 346, 155. f Faust, W. L. et al. Phys. Rev., 1961, 123, 198.
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Ab initio calculations A large dissociation energy was
calculated for XeCuCl (55 kJ mol-1); Charge-induced dipole induction energy for
XeCuCl: 21 kJ mol-1;
Mulliken and NBO populations show significant donation of electron density from the Xe to the Cu;
Donation of ~0.1-0.2 of an elementary charge donated from Xe to Cu.
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0
20
40
60
80
100
20 40 60 80 100 120 140
Force constant, k (N/m)
Dis
soci
atio
nE
ner
gy,D
e(k
J/m
ol)
ArMX
KrMX
XeMX
ArMX
KrMX
XeMXArAgCl
ArAgFKrAgCl
KrAgF
XeAgClXeAgF
ArCuCl
KrCuClArAuCl
ArCuF
KrCuF
KrAuCl
KrAuF
ArAuF
XeAuF
XeCuClXeCuF
From the Morse Potential:k = 2D âe
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Plots of dissociation energy vs. force constant for all studied NgMX molecules
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Local Energy Densitiesa
H(r) = G(r) + V(r)
Values are calculated at the bond critical point of the maximum electron density (MED) path between bonded atoms.
Negative H(r) implies … V(r) dominates … e- density accumulates
at rB
… a covalent bond forms!!a Cremer, D.; Kraka, E. Angew. Chem. 1984, 96, 612; see also Angew. Chem. Int. Ed. Engl., 1984, 23, 627.
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Local Energy Densities
Local Energy Densities at rB
(Hartree Å-3) for several NgMX molecules
ArCuF -0.0151
ArCuCl -0.0148
KrCuF -0.0400
KrCuCl -0.0390
XeCuF -0.0699
XeCuCl -0.0667
XeAgF -0.0542
XeAgCl -0.0457
XeAuF -0.1799
!All negative values
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Conclusion
First preparation and characterization XeCuCl;
Very strong Xe-Cu interactions observed; Strong Ng-M interactions similar to those
expected from previous NgMX studies; XeCuCl shows convincing evidence of
covalent Xe-Cu bonding.