The permanent electric dipole moment of PtO, PtS, PtN, and PtC

Article abstract of DOI:10.1063/1.469750

The permanent electric dipole moments of the ground, and the low-lying excited electronic states of platinum monocarbide, PtC, platinum monoxide, PtO, and platinum monosulfide, PtS, were measured using a molecular beam optical Stark spectroscopic scheme.The determined values were (in Debye): PtO(X ³Σ^-) 2.77(2); PtO(A ¹Σ⁺) 1.15(4); PtS 1.78(2); PtS 0.54(6); PtC(X ¹Σ⁺) 0.99(5); and PtC(A ¹Π) 2.454(3).These results, along with the previous results for PtN(X ²Π_1/2) 1.977(9); PtN(d ⁴Π_1/2) 1.05(9) , are used as basis for a discussion of the nature of the electronic states.

Full text of DOI:10.1063/1.469750

The permanent electric dipole moment of PtO, PtS, PtN, and PtC
T. C. Steimle, K. Y. Jung, and B.Z. Li
Citation: The Journal of Chemical Physics 103, 1767 (1995); doi: 10.1063/1.469750
View online: http://dx.doi.org/10.1063/1.469750
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The permanent electric dipole moment of PtO, PtS, PtN, and PtC
T. C. Steimle, K. Y. Jung, and B.-Z. Li
Department of Chemistry and Biochemistry, Arizona State University, Tempe, Arizona 85287-1604
͑
Received 13 March 1995; accepted 24 April 1995͒
The permanent electric dipole moments of the ground, and the low-lying excited electronic states of
platinum monocarbide, PtC, platinum monoxide, PtO, and platinum monosulfide, PtS, were
measured using a molecular beam optical Stark spectroscopic scheme. The determined values were
3
Ϫ
1
ϩ
͑
0
in Debye͒: PtO(X ⌺ ) 2.77͑2͒; PtO(A ⌺ ) 1.15͑4͒; PtS[X(⍀ϭ0)] 1.78͑2͒; PtS[B(⍀ϭ0)]
1
ϩ
1
.54͑6͒; PtC(X ⌺ ) 0.99͑5͒; and PtC(A ⌸) 2.454͑3͒. These results, along with the previous
2
4
results for PtN(X ⌸1 ) 1.977͑9͒; PtN(d ⌸1/2) 1.05͑9͒ ͓J. Chem. Phys. 102, 643 ͑1995͔͒, are
/2
used as a basis for a discussion of the nature of the electronic states. © 1995 American Institute of
Physics.
I. INTRODUCTION
dipole moments for those molecular states with populated
s–d hybridized orbitals should be small since the nonbond-
ing Pt-centered hybrid orbital balances the charge donation
in the bonding orbitals. Therefore, a comparison of the di-
pole moments in various low-lying electronic states will
A knowledge of the permanent electric dipole moment,
, is the most direct probe of the ionic nature of a chemical
bond and enters into the description of numerous physical
phenomena. For example, a description of the light/matter
interaction requires a knowledge of ␮ or the dependence of
␮
9
1
10
readily reveal the relative importance of the 5d 6s , 5d ,
8
2
and 5d 6s configurations in bonding. The classical view of
electron donation at long internuclear distances from a C, O,
N, or S atom to Pt in the ␴ system, back-donation of Pt
electrons to the C, O, N, or S atom at short bond distances in
the ␲ system and Pt to C, O, N, or S charge transfer will also
be important in describing trends in dipole moments.
␮
on the geometric structure. In addition, the permanent
electric dipole moment should be among the most reliably
predicted properties calculated using ab initio or semiempir-
ical calculations because it depends primarily upon the va-
lence electrons and is described by a simple sum of one
electron operators. From a purely electrostatic perspective,
the relatively high ionization potential of Pt͑Х9.0 eV͒ sug-
gests that the dipole moment of diatomic platinum com-
pounds will be small and dominated by polarization effects
of the Pt-centered valence electrons. The polarizability of the
numerous atomic states of Pt will be quite varied depending
Here, we report the results of a molecular beam optical
Stark study of the ground and low-lying excited states of
platinum monoxide, PtO, platinum monosulfide, PtS and
platinum monocarbide, PtC. Recently the results of a mo-
lecular beam optical Stark study and a sophisticated ab initio
5
prediction of the physical properties of PtN were reported.
9
1
10
Other molecular beam work relevant to the current study
includes the first identification and analysis of the associated
upon the relative contributions from the 5d 6s , 5d and
8
2
5
d 6s configurations. The lowest terms from these three
6
optical spectra of PtS and the analysis of the magnetic hy-
configurations have approximately the same ͑J-averaged͒
7
1
3
9
1
1
10
perfine structure in the optical spectra of PtC. The conven-
energy Eϭ0.0 eV[ D(5d 6s )], EϷ0.7 eV[ S(5d )],
3
8
2
tional emission spectrum of PtO was analyzed some time
ago.8 Recently the FTIR spectrum of PtO was recorded and
analyzed.10 There are no published predictions of ␮ for PtO,
PtS, or PtC.
and EϷ0.85 eV[ F(5d 6s )].
,9
The description of bonding in Pt compounds is expected
to be complex because of the near degeneracy of the terms
arising from the three low-lying configurations and the large
spin–orbit interaction expected. Furthermore, unlike isova-
lent Ni compounds, where there is generally a significant
repulsive interaction between the 4s electrons and the bond-
II. EXPERIMENT
2
3
ing atom or ligand, the 6s electrons may be less repulsive
The laser ablation molecular beam spectrometer has
been described previously.5 The production schemes for
the generation of PtS and PtC were identical to those used
previously ͑PtS: Ref. 6; PtC: Ref. 7͒. An intense beam of Pt
containing compounds were generated by skimming the
products of a pulsed supersonic laser ablation source. In all
cases the third harmonic radiation from a Nd:YAG laser ͑355
nm, 5 mJ/pulse͒, running at 20 Hz, was focused onto a ro-
tating platinum tube situated in the throat of a commercial
solenoid type pulsed valve. The expanding gas consisted of a
N O, CH , H S, or NH ͑ϳ5%͒/argon mixture at a backing
–7
and possibly even participate in bond formation because the
difference in radial extent is not too severe:
͗ ͘
6s͉r͉6s /
͗
5d 5d Ϸ1.9 ͑Ref. 4͒. If there is a significant repulsive
͉
r
͉
͘
interaction as the 6s electrons are approached by a C, O, N,
or S atom then extensive s–d hybridization would be ex-
pected to occur for a Pt atom in a state arising from the
9
1
8
2
5
d 6s or 5d 6s configurations. The resulting s–d hybrid
orbital that has the electron density removed from the C, O,
N, or S atom will then become doubly occupied for enhanced
stability. The repulsive interaction is absent when the Pt atom
in a state arising from a 5d10 configuration is approached by
the C, O, N, or S atom and the resulting molecular states are
expected to have no occupied s–d hybridized orbitals. The
2
4
2
3
pressure of ϳ400 kPa. The molecular beam was crossed with
the output of a single mode ring cw-dye laser approximately
30 cm downstream from the source. Less than 1 mW of
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1768
Steimle, Jung, and Li: Dipole moment of PtO, PtS, PtN, and PtC
comparison with the absorption spectrum of I ͑Ref. 12͒. The
2
transmission of a calibrated 1 m confocal e´ talon ͑FSRϳ76.6
MHz͒ was simultaneously recorded to aid in the extrapola-
tion between I absorption features and used to measure the
2
shifts and splitting induced by the application of the static
electric field.
III. OBSERVATIONS
The R(1) branch features ͑␯ϭ16 934.350 cmϪ1͒ of the
1
ϩ
3
Ϫ
͑
0,0͒ A ⌺ –X ⌺ band system of PtO recorded in the
absence and presence of a perpendicular orientated static
electric field are presented in Fig. 1. The electric field causes
each of the spectral features associated with the three major
isotopomers to split into two features with a relative intensity
of approximately 3:1. The weaker feature is the MJЈ
FIG. 1. The R(1) branch features ͑␯ϭ16 934.350 cmϪ1͒ of the ͑0,0͒
ϭϮ1←MЉ ϭ 0 transition and the stronger one the
J
1
ϩ
3
Ϫ
A
⌺
–X
V/cm and ͑b͒ 2164 V/cm. ͑c͒ The transmission of a 1 m confocal etalon
FSRϭ76.6 MHz͒. The electric vector of the static field was orientated
⌺
band system of PtO recorded with a field strength of ͑a͒ 0
MЈϭϮ2←MЉ ϭ Ϯ1 transition. The shifting of the
J
J
weaker feature being significantly greater than that of the
intense feature indicates that the Stark effect is substantially
͑
perpendicular to the electric field of the linearly polarized laser radiation.
The three zero field features, from lower to higher frequency, are the
3
Ϫ
1
ϩ
larger in the X ⌺ state than it is in the A ⌺ state. The
observed and calculated shifts along with the assignments for
PtO are given in Table I.
1
94
195
196
PtO,
PtO, and
PtO isotopomers.
The R(1) branch features ͑␯ϭ15 924.790 cmϪ1͒ of the
unfocused radiation was used in order to avoid power broad-
ening. A set of calibrated parallel Stark plates,11 one being a
͑0,0͒ B(⍀ϭ0)–X(⍀ϭ0) band system of PtS recorded in
the absence and presence of a parallel orientated static elec-
tric field are presented in Fig. 2. Although the signal-to-noise
ratio is somewhat less than that of PtO given in Fig. 1, the
basic pattern is identical. Also note that the shifts in Fig. 1
and Fig. 2 are comparable although the rotational constant
for PtS is significantly less than that of PtO ͓PtS[X(⍀ϭ0)]:
90% transmissive neutral density filter, straddled the plane
defined by the laser and molecular beam. The signal was
viewed through a Ϯ10 nm bandpass filter, centered at the
laser excitation wavelength and detected with a cooled pho-
tomultiplier tube. The laser wavelength was calibrated by
TABLE I. The optical Stark data for the R(1) and P(2) branch features of the ͑0,0͒ A 1
⌺
ϩ
–X 3
⌺
Ϫ
transition
Diff.
Ϫ1
͑T00ϭ16 933.42 cm ͒ of platinum monoxide; PtO.
V/cm
P(2)Ќc
JЉMЉJЈMЈ
Obs. shifta
Diff.b
V/cm
R(1)
JЉMЉJЈMЈ
Obs. shift
J
J
J
J
ʈ
3534.0
3885.3
4187.0
2,0→1,Ϫ1
Ϫ65
29
Ϫ73
32
Ϫ64
32
Ϫ84
29
Ϫ81
39
Ϫ84
33
Ϫ106
43
Ϫ97
43
5
Ϫ2
Ϫ2
1
7
1
1
Ϫ8
4
1
1
3905.0
1,0→2,1
1,1→2,2
1,0→2,1
1,1→2,2
1,0→2,1
1,1→2,2
1,0→2,1
1,1→2,2
1,0→2,1
1,1→2,2
1,0→2,1
1,1→2,2
1,1→2,2
1,1→2,2
1,0→2,1
1,1→2,2
Ϫ244
123
Ϫ246
122
Ϫ181
76
Ϫ175
85
Ϫ174
89
4
4
1
2
2
2
2
2
,2→1,1
,0→1,Ϫ1
,2→1,1
4
,0→1,Ϫ1
,2→1,1
3293.0
Ϫ4
Ϫ8
2
1
3
5
Ϫ1
7
6
6
Ϫ6
0
Ϫ2
Ϫ2
0
2,0→1,Ϫ1
2
2
2
2
2
,2→1,1
,0→1,Ϫ1
,2→1,1
,0→1,Ϫ1
,2→1,1
2742.0
2164.0
Ϫ124
66
Ϫ4
Ϫ8
Ϫ1
2
2,0→1,Ϫ1
64
64
Ϫ83
37
Ϫ79
34
2,2→1,1
2,0→1,Ϫ1
2,2→1,1
0
1,0→2,1
1,1→2,2
1,0→2,1
1,1→2,2
Ϫ78
38
2
aThe difference between the optical transition frequency in the presence and absence of the applied external
electric field ͑in MHz͒. The multiple entries for a given electric field strength are associated with individual
isotopomers. Weak features blended with the strong transitions were omitted ͓e.g., the R(1)MЉ ϭ 0→MЈ
J
J
1
95
196
ϭ 1 transitions of the
PtO and
PtO isotopomers for a field strength of 2742 V/cm͔.
b
The difference between the observed and calculated shift in the optical transition frequencies ͑in MHz͒. The
transition frequencies were calculated using the fine structure constants of Ref. 9.
Branch designation and relative polarization orientation of laser radiation and static electric field.
c
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J. Chem. Phys., Vol. 103, No. 5, 1 August 1995
155.33.109.21 On: Fri, 05 Dec 2014 02:04:25

Steimle, Jung, and Li: Dipole moment of PtO, PtS, PtN, and PtC
1769
FIG. 2. The R(1) branch features ͑␯ϭ15 924.790 cmϪ1͒ of the ͑0,0͒ B(⍀
ϭ0))ϪX(⍀ϭ0) band system of PtS recorded with a field strength of ͑a͒ 0
V/cm and ͑b͒ 2834 V/cm. ͑c͒ The transmission of a 1 m confocal etalon
FIG. 3. ͑a͒ The R(0) branch feature ͑␯ϭ18 511.219 cmϪ1͒ of the ͑0,0͒
͑FSRϭ76.6 MHz͒. The electric vector of the static field was orientated
1
⌸–X 1
ϩ
194
parallel to the electric field of the linearly polarized laser radiation. The two
A
⌺
band system of
PtC. Both the shifted and zero field fea-
1
94
zero field features, from lower to higher frequency, are the
PtS isotopomers.
PtS and
tures were recorded in the same scan by turning on/off the applied electric
field. ͑b͒ The transmission of a 1 m confocal etalon ͑FSRϭ76.6 MHz͒.
Electric vector of the static field was orientated perpendicular to the electric
field of the linearly polarized laser radiation.
1
95
Ϫ1
3
Ϫ
B ϭ0.147 269
cm
͑Ref.
6͒;
PtO(X ⌺ ):
0
Ϫ1
B ϭ0.380 869 cm
͑Ref. 9͔͒ indicating that ␮ ͑PtS͒
1
ϩ
0
Stark shift of the JЉϭ0, MЉ ϭ 0 level of the X ⌺ state.
J
Ͻ␮͑PtO͒. The observed and calculated shifts and the quan-
The observed and calculated Stark frequency shifts along
with the quantum number assignments for PtC are given in
Table III.
tum number assignments for PtS are given in Table II.
Ϫ1
The R(0) branch feature ͑␯ϭ18 511.219 cm ͒ of the
1
1
ϩ
194
͑
0,0͒ A ⌸–X ⌺ band system of
PtC recorded in the
absence and presence of a perpendicular oriented static elec-
tric field is presented in Fig. 3. In this case both the shifted
and zero field features were recorded in the same scan by
turning the applied electric field on and off at the appropriate
wavelengths. A large first order Stark shift is expected due to
IV. ANALYSIS
The Stark shifts were modeled by adding the simple
electric field-dipole moment operator, H
effective Hamiltonian operator, H , that describes the fine
structure. The matrix representation of H inclusive of the
ˆ Stark
ϭϪ␮•E, to the
ˆ eff
1
7
ˆ eff
the near degeneracy of the ⌳ doublets in the A ⌸ state.
Thus the two shifted features are readily assigned as the
Stark operator is diagonal in M and of infinite dimension.
J
MЈ ϭ Ϯ1←MЉ ϭ 0 transition. The slight asymmetry that
The matrix representations were truncated at a finite size
commensurate with the experimental accuracy ͑Ϸ20 MHz͒.
J
J
is apparent in Fig. 3 is due to the small second order
TABLE II. The optical Stark data for the R(1) and P(2) branch features of the ͑0,0͒ B(⍀ϭ0)ϪX(⍀ϭ0)
Ϫ1
transition ͑T00ϭ15 924.25 cm ͒ of platinum monosulfide; PtS.
V/cm
JЉMЉJЈMЈ
Obs. shifta
Diff.b
V/cm
R(1)
JЉMЉJЈMЈ
Obs. shift
Diff.
J
J
J
J
P(2)Ќc
ʈ
4
478.0
2,0→1,Ϫ1
Ϫ105
69
Ϫ114
75
Ϫ75
45
Ϫ17
Ϫ90
51
0
0
Ϫ9
6
4
7
Ϫ11
Ϫ10
Ϫ1
2268.0
1,0→2,0
1,1→2,1
1,0→2,0
1,1→2,1
1,0→2,0
1,1→2,1
1,0→2,1
1,1→2,2
1,0→2,1
Ϫ78
47
Ϫ87
57
Ϫ91
55
Ϫ126
87
Ϫ132
75
Ϫ208
103
Ϫ198
103
10
4
1
2
2
2
,2→1,1
,0→1,Ϫ1
,2→1,1
2407.0
4
3912.0
2,0→1,Ϫ1
Ϫ4
Ϫ8
2
1
3
5
Ϫ1
7
6
6
2,2→1,1
2,1→1,0
2,0→1,Ϫ1
2,2→1,1
2834.0
1
,1→2,2
3404.0
1,0→2,1
1
1
1
,1→2,2
,0→2,1
,1→2,1
aThe difference between the optical transition frequency in the presence and absence of the applied external
electric field ͑in MHz͒. The multiple entries for a given electric field strength are associated with individual
1
94
195
isotopomers. Only the
PtS and
PtS isotopomers were measured.
b
The difference between the observed and calculated shift in the optical transition frequencies ͑in MHz͒. The
transition frequencies were calculated using the fine structure constants of Ref. 6.
Branch designation and relative polarization orientation of laser radiation and static electric field.
c
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J. Chem. Phys., Vol. 103, No. 5, 1 August 1995
155.33.109.21 On: Fri, 05 Dec 2014 02:04:25

1770
Steimle, Jung, and Li: Dipole moment of PtO, PtS, PtN, and PtC
TABLE III. The optical Stark data for the R(0) and Q(1) branch features of the ͑0,0͒ A 1⌸–X 1
⌺
ϩ
Ϫ1
͑T00ϭ18 510.73 cm ͒ of platinum monocarbide; PtC.
V/cm
JЉMЉJЈMЈ
Obs. shifta
Diff.b
V/cm
JЉMЉJЈMЈ
Obs. shift
Diff.
J
J
J
J
R(0)Ќc
Q(1)Ќ
2818.3
2959.9
7
8
1
1
1
1
1
2
2
2
2
3
3
15.9
0,0→1,1
431
Ϫ444
550
Ϫ552
926
Ϫ938
980
Ϫ1003
1058
Ϫ1078
1127
Ϫ1115
1219
Ϫ1230
1299
Ϫ1339
1458
Ϫ1495
1625
Ϫ1640
1785
Ϫ1823
1991
Ϫ2037
2008
Ϫ13
Ϫ3
Ϫ4
Ϫ1
7
Ϫ18
Ϫ12
Ϫ7
Ϫ7
Ϫ9
20
Ϫ5
Ϫ6
0
Ϫ11
Ϫ21
Ϫ21
Ϫ5
5
1,0 →1,Ϫ1
1,0 →1,1
Ϫ1786
1766
Ϫ1880
1905
Ϫ2005
1953
Ϫ2093
2017
Ϫ2147
2106
Ϫ2260
2173
Ϫ2324
2246
Ϫ2448
2345
Ϫ1
Ϫ10
Ϫ3
14
0
,0→1,Ϫ1
94.0
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
0,0→1,1
,0→1,Ϫ1
1,0 →1,Ϫ1
1,0 →1,1
0
3158.1
3282.7
3377.9
3537.6
3652.6
3803.8
3939.7
4042.8
4182.1
490.7
610.8
728.6
795.4
989.0
129.6
405.8
636.9
920.2
261.2
262.3
1,0 →1,Ϫ1
1,0 →1,1
2
0
Ϫ10
Ϫ5
Ϫ2
3
Ϫ5
Ϫ5
Ϫ4
6
Ϫ18
Ϫ18
3
Ϫ3
Ϫ6
Ϫ16
Ϫ2
Ϫ15
1,0 →1,Ϫ1
1,0 →1,1
0
1,0 →1,Ϫ1
1,0 →1,1
0
1,0 →1,Ϫ1
1,0 →1,1
0
1,0 →1,Ϫ1
1,0 →1,1
0
1,0 →1,Ϫ1
1,0 →1,1
0
1,0 →1,Ϫ1
1,0 →1,1
Ϫ2522
2395
Ϫ2604
2478
0
1,0 →1,Ϫ1
1,0 →1,1
0
Ϫ5
Ϫ8
Ϫ11
Ϫ9
Ϫ12
8
1,0 →1,Ϫ1
Ϫ2694
0
Q(1)
ʈ
596.6
1,1 →1,1
1,Ϫ1 →1,Ϫ1
1,1 →1,1
372
Ϫ369
441
Ϫ441
545
Ϫ554
695
Ϫ701
812
Ϫ805
917
Ϫ919
987
Ϫ1002
1243
Ϫ1289
1587
Ϫ1632
1831
Ϫ1899
2121
Ϫ2224
7
3
3
5
Ϫ2
3
0
715.8
0
Ϫ2029
Ϫ4
1,Ϫ1 →1,Ϫ1
1,1 →1,1
Q(1)Ќ
894.6
1
1
1
1
2
2
2
2
031.9
248.3
438.6
708.2
069.5
405.9
516.4
657.4
818.3
1,0→1,1
,0→1,Ϫ1
1,0→1,1
,0→1,Ϫ1
1,0→1,1
,0→1,Ϫ1
1,0→1,1
,0→1,Ϫ1
1,0→1,1
,0→1,Ϫ1
1,0→1,1
,0→1,Ϫ1
1,0→1,1
,0→1,Ϫ1
1,0→1,1
,0→1,Ϫ1
1,0→1,1
629
Ϫ643
763
Ϫ786
869
Ϫ907
1057
Ϫ1091
1264
Ϫ1304
1453
Ϫ1519
1516
Ϫ1592
1590
Ϫ1663
1684
1
1
3
1,Ϫ1 →1,Ϫ1
1,1 →1,1
1
1132.7
1311.6
1490.7
1609.4
2058.2
2596.3
3016.5
3526.3
3
5
1,Ϫ1 →1,Ϫ1
1,1 →1,1
1
Ϫ4
Ϫ4
Ϫ5
21
Ϫ18
13
Ϫ1
3
0
0
Ϫ1
Ϫ8
19
Ϫ8
10
12
7
10
4
1,Ϫ1 →1,Ϫ1
1,1 →1,1
1
1,Ϫ1 →1,Ϫ1
1,1 →1,1
1
1,Ϫ1 →1,Ϫ1
1,1 →1,1
2
1
Ϫ11
Ϫ3
9
Ϫ6
1
Ϫ7
Ϫ13
Ϫ6
1,Ϫ1 →1,Ϫ1
1,1 →1,1
1
1,Ϫ1 →1,Ϫ1
1,1 →1,1
1
1,Ϫ1 →1,Ϫ1
1,1 →1,1
1
2
1,Ϫ1 →1,Ϫ1
a
The difference between the optical transition frequency in the presence and absence of the applied external
1
94
electric field ͑in MHz͒. Only the
PtC isotopomer was measured.
b
The difference between the observed and calculated shift in the optical transition frequencies ͑in MHz͒. The
transition frequencies were calculated using the fine structure constants of Ref. 7.
Branch designation and relative polarization orientation of laser radiation and static electric field.
c
The energy levels of both the ground and excited states of
PtO and PtS and the ground state of PtC were modeled by
constructing a 4ϫ4 matrix appropriate for an ⍀ϭ0 state in a
case a basis set. This included the interaction between the
data. The determined dipole moments and associated errors
are given in Table IV along with the values for the equilib-
rium internuclear distance, r , and ␮/r . The values for
PtN are also given for comparison. The errors represent a
purely statistical estimate of a one standard deviation confi-
dence limit. In most cases ͑see Table IV͒ this is somewhat
smaller than the estimated systematic error of approximately
3% associated with the determination of the electric field
strength. Note that through a judicious choice of branch fea-
tures and the extensive range of field strengths the correla-
e
e
5
1
Jϭ0, 1, 2, and 3 levels. The energy levels for the A ⌸
1
94
levels of
PtC were modeled by numerical diagonalization
of a 6ϫ6 matrix in a case a basis set. This included all the
interaction between the Jϭ0, 1, and 2 levels.
A nonlinear least squares fitting procedure which incor-
porated the modeled energy levels was used to reduce the
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155.33.109.21 On: Fri, 05 Dec 2014 02:04:25

Steimle, Jung, and Li: Dipole moment of PtO, PtS, PtN, and PtC
1771
TABLE IV. Dipole moments of Pt-containing molecules.
only the valence Pt and C, N, O, and S atomic orbitals were
considered. The coarse character of these molecular orbitals
will be: 1␴ϳX(ns); 2␴ϳc Pt(5d )ϩc Pt(6s)ϩc X(np );
Molecule
PtO
State
re͑Å͒a ␮͑D͒b ␮͑D͒/r ͑Å͒ Correlation coefficientc
e
1
0
2
3
0
3
1
Ϫ
X
A
⌺
⌺
1.727 2.77͑2͒
1.795 1.15͑4͒
1.603
0.638
0.872
0.267
0.587
1.389
1.174
0.597
1␲ϳPt(5dϮ1)ϩX(npϮ1); 1␦ϳPt(5dϮ2); 3␴ϳcЈ Pt(5d )
0
1
ϩ
0.205
0.129
ϩcЈ Pt͑6s͒ϩcЈ X(np );
2␲ϳPt(5dϮ1)ϪX(npϮ1);
2
3
0
PtS
X(⍀ϭ0) 2.042 1.78͑2͒
B(⍀ϭ0) 2.108 0.54͑6͒
4
␴ϳPt(5d ϩ6s); with XϭC, N, O, or S and nϭ2 or 3. The
0
1
ϩ
calculations for PtN indicated that the composition of the 2␴
and 3␴ orbital ͑i.e., c and cЈ , etc.͒ strongly vary as a func-
PtC
PtNd
X
A
X
⌺
1.679 0.99͑5͒
1.766 2.454͑3͒
1.682 1.977͑9͒
1.756 1.05͑11͒
1
⌸
⌸
⌸
Ϫ0.105
Ϫ0.187
1
1
2
tion of electronic state. Evidently, these orbitals facilitate the
electron donation at long internuclear distances from the C,
O, N, or S atom to Pt. The 1␲ orbital facilitates backdonation
of Pt electrons to the C, O, N, or S atom at short bond
distances. The 4␴ molecular orbital is a hybrid orbital point-
ing away from the Pt–X bond. This molecular orbital corre-
lation diagram would then imply the following primary con-
figurations:
d 4
aCalculated using the previously determined fine rotational parameters: PtO:
Ref. 9; PtS: Ref. 6; PtC: Ref. 7, PtN: Ref. 5.
b
Experimental values of the dipole moment in Debye. The numbers in pa-
rentheses represent a one standard deviation error estimate in the last
quoted decimal point. Systematic error resulting from determination of the
field strength is estimated to produce an approximate 3% error in ␮.
c
The correlation coefficients as determined from a direct fit of the optical
Stark spectra.
Dipole from Ref. 5.
1
ϩ
2
2
2
4
4
d
PtC͑X ⌺ ͒:1␴ 2␴ 3␴ 1␲ 1␦ ,
͑1͒
͑2͒
͑3͒
͑4͒
͑5͒
͑6͒
͑7͒
͑8͒
1
2
2
2
4
1
3
PtC͑A ⌸͒:1␴ 2␴ 3␴ 1␲ 2␲ 1␦ ,
tion between the ground and excited state values of ␮ is
small. The final set of optimized values of ␮ were used to
calculate the differences between the observed and calcu-
lated shifts given in Tables I–III. The final root-mean-square
of the deviations was 4.1, 7.1, and 9.2 MHz for PtO, PtS, and
PtC, respectively.
3
Ϫ
2
2
2
4
2
4
PtO͑X ⌺ ͒:1␴ 2␴ 3␴ 1␲ 2␲ 1␦ ,
1
ϩ
2
2
1
1
4
2
4
PtO͑A ⌺ ͒:1␴ 2␴ 3␴ 4␴ 1␲ 2␲ 1␦ ,
2
2
2
2
4
1
4
PtN͑X ⌸͒:1␴ 2␴ 3␴ 1␲ 2␲ 1␦ ,
4
2
2
1
1
4
1
4
PtN͑d ⌸͒:1␴ 2␴ 3␴ 4␴ 1␲ 2␲ 1␦ ,
2
2
2
4
2
4
PtS͓X͑⍀ϭ0͔͒:1␴ 2␴ 3␴ 1␲ 2␲ 1␦ ,
V. DISCUSSION
2
2
1
1
4
2
4
A simple molecular orbital correlation diagram resulting
from the coupling of the Pt ͑5d , 5d 6s or 5d 6s ͒ elec-
PtS͓B͑⍀ϭ0͔͒:1␴ 2␴ 3␴ 4␴ 1␲ 2␲ 1␦ .
1
0
9
1
8
2
1
The value of ␮ ͓PtC(A ⌸)͔ is substantially greater than
2
2
2
3
2
4
trons with the C(2s 2p ), N(2s 2p ), O(2s 2p ), or
1
ϩ
the value of ␮ ͓PtC(X ⌺ )͔ because to a first approxima-
2
4
S(3s 3p ) electrons that predicts the observed trends in ␮ is
1
1
ϩ
tion the A ⌸ state differs from the X ⌺ state by the pro-
motion of an electron in a nonbonding Pt-centered ␦ orbital
to a C-centered antibonding 2␲ orbital. This is consistent
given in Fig. 4. This qualitative diagram is consistent with
the predicted nature of the molecular orbitals for PtN,
the observed hyperfine structure of PtC, and general consid-
5
7
1
1
ϩ
with the observation that r (A ⌸)Ͼr (X ⌺ ) ͑see Table
IV͒ and the sign of the magnetic hyperfine parameter. The
value ␮ ͓PtO(X ⌺ )͔ is substantially greater than ␮
PtN(X ⌸) because the O-centered antibonding 2␲ orbital is
e
e
erations for bonding in transition metal diatomic
7
1
3
molecules. In labeling the molecular orbitals in Fig. 4
3
Ϫ
2
doubly occupied in PtO and is only singly occupied in PtN.
This is also consistent with the observation that
3
Ϫ
2
r ͓PtO(X ⌺ )]Ͼr ͓PtN(X ⌸)͔. The excited state values
e
e
␮
for PtO, PtN, and PtS are substantially smaller than the
ground state values because the excited state configurations
differ from the ground state configurations by a promotion of
an electron from the bonding 3␴ orbital to the nonbonding
Pt-centered 4␴ ͓ϳPt(5d ϩ6s)͔ orbital which is polarized
0
away from the C, O, N, or S atom. Finally, it is interesting to
note that the ratio of ␮/r for PtS͑X(⍀ϭ0)͒ to ␮/r for
e
e
3
Ϫ
PtO(X ⌺ )(ϭ0.732) is nearly identical to the ratio of the
electronegativities14 of S to O ͑ϭ0.714͒.
There are no experimental determinations for the isova-
lent PdX and NiX ͑XϭC, O, N, or S͒ compounds but a
3
Ϫ
theoretical value for ␮/r ͓NiO(X ⌺ )͔ ͑ϭ6.25 D/1.67
e
2
Åϭ3.74 D/Å͒ has been reported. The lower IP of Ni ͑Ϸ7.6
FIG. 4. A plausible molecular orbital correlation diagram that describes the
qualitative trends in the observed dipole moments of PtO, PtS, PtC, and PtN.
eV͒ vs Pt ͑Ϸ9.2 eV͒ is partly responsible the difference be-
1
ϩ
2
2
2
4
4
3
Ϫ
3
Ϫ
The
primary
configurations
are
PtC(X ⌺ ):1␴ 2␴ 3␴ 1␲ 1␦ ;
Ϫ
tween ␮/r ͓NiO(X ⌺ )͔ and ␮/r ͓PtO(X ⌺ )͔ ͑ϭ1.603
e
e
1
2
2
2
4
1
3
3
2
2
2
4
2
4
PtC(A ⌸):1␴ 2␴ 3␴ 1␲ 2␲ 1␦ ; PtO(X ⌺ ): 1␴ 2␴ 3␴ 1␲ 2␲ 1␦ ;
PtO(A ⌺ ):1␴ 2␴ 3␴ 4␴ 1␲ 2␲ 1␦ ; PtN(X ⌸):1␴ 2␴ 3␴ 1␲ 2␲ 1␦ ;
PtN(d ⌸):1␴ 2␴ 3␴ 4␴ 1␲ 2␲ 1␦ ;PtS[X(⍀ϭ0)]:1␴ 2␴ 3␴ 1␲ 2␲ 1␦ ;
D/Å͒. More important is the relative participation of the
1
ϩ
2
2
1
1
4
2
4
2
2
2
2
4
1
4
8
2
9
1
10
4
2
2
1
1
4
1
4
2
2
2
4
2
4
nd (nϩ1)s , nd (nϩ1)s , and nd configurations in the
2
2
1
1
4
2
4
3
Ϫ
PtS[B(⍀ϭ0)]: 1␴ 2␴ 3␴ 4␴ 1␲ 2␲ 1␦ .
X ⌺ bonding. Although the energies of the lowest terms
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155.33.109.21 On: Fri, 05 Dec 2014 02:04:25

1772
Steimle, Jung, and Li: Dipole moment of PtO, PtS, PtN, and PtC
3
9
1
from the three low-lying configurations of Pt: ͑͑ D(5d 6s ):
ACKNOWLEDGMENTS
1
10
3
8
2
Eϭ0.0 eV; S(5d ): EϷ0.7 eV and F(5d 6s ):
The authors would like to thank Dr. Andrew Marr for his
helpful comments. This work was supported by a grant from
the Fundamental Interactions Branch, Division of Chemical
Sciences, Office of Basic Energy Sciences, Dept. of Energy
1
3
9
1
EϷ0.85 eV͒͒ are similar to those of Ni ͑ D(3d 4s ):
1
10
3
8
2
Eϭ0.0 eV; S(3d ): EϷ1.7 eV and F(3d 4s ):
1
EϷ0.03 eV͒͒, the ratio of the radial extent of the (nϩ1)s
and nd orbitals for Pt vs Ni are markedly different:
/ 5d͉r͉5d )Ϸ1.9 ͑Ref. 4͒ and Ni( 4s͉r͉4s /
͘ ͗ ͘ ͗ ͘
͉r͉3d )Ϸ3.22 ͑Ref. 15͒. The similarity in radial extent
of the 6s and 5d orbitals for Pt facilitates s–d hybridization
which can greatly reduce the expected value of ␮. The rela-
tively small values of ␮/r determined in the present study
indicates that the nd (nϩ1)s and nd (nϩ1)s configura-
tions are more important in describing the bond in PtX than
in NiX ͑XϭC, N, O, and S͒.
͑DE-FG02-94ER14468͒.
Pt(
3d
͗
6s
͉
r
͉
6s
͘
1
2
3
4
5
6
C. E. Moore, Tables of Atomic Energy Levels, Natl. Bur. Stand. ͑U.S.
GPO, Washington, DC, 1971͒.
C. W. Bauschlicher, Jr., C. J. Nelin, and P. S. Bagus, J. Chem. Phys. 82,
3265 ͑1985͒.
M. R. A. Blomberg, U. B. Brandemark, P. E. R. Siegbahn, K. B. Mathisen,
and G. Karlstr o¨ m, J. Phys. Chem. 89, 2171 ͑1985͒.
A. D. McLean and R. S. McLean, At. Data Nucl. Data Tables 26, 305
͗
e
8
2
9
1
͑
1981͒.
K. Y. Jung, T. C. Steimle, D. Dai, and K. Balasubramanian, J. Chem. Phys.
02, 643 ͑1995͒.
B.-Z. Li, K. Y. Jung, and T. C. Steimle, J. Mol. Spectrosc. 170, 310
1995͒.
1
VI. CONCLUSION
͑
7
8
T. C. Steimle, K. Y. Jung, and B.-Z. Li, J. Chem. Phys. 102, 5937 ͑1995͒.
C. Nilsson, R. Scullman, and N. Mehendale, J. Mol. Spectrosc. 35, 172
The permanent electric dipole moments of PtO, PtC, and
PtS have been determined and compared with previous val-
ues for PtN. A simple molecular orbital correlation diagram
has been proposed that is consistent with the trends in the
determined values of ␮/r and with the previously deter-
mined magnetic hyperfine and fine structure. The determined
values of ␮/r for PtO, PtC, PtS, and PtN are substantially
smaller than those for first row transition metal oxides
nitrides and sulfides. These differences can not be ex-
plained solely by differences in ionization potentials. The
very small magnitudes of ␮/r for the excited states of PtO
͑
1970͒.
9
0
U. Sassenberg and R. Scullman, Phys. Scr. 28, 139 ͑1983͒.
C. I. Frum, R. Engleman, Jr., and P. F. Bernath, J. Mol. Spectrosc. 150,
1
566 ͑1991͒.
e
11
T. C. Steimle, D. A. Fletcher, K. Y. Jung, and C. T. Scurlock, J. Chem.
Phys. 96, 2556 ͑1992͒.
S. Gerstenkorn and P. Luc, Atlas du Spectre d’Absorption de la Mol e´ cule
12
e
16
d’Iode ͑CNRS, Paris 1978͒; Rev. Phys. Appl. 14, 791 ͑1979͒.
A. J. Merer, Annu. Rev. Phys. Chem. 40, 407 ͑1989͒.
1
1
3
4
1
7
18
L. Pauling, General Chemistry ͑Dover, New York, 1971͒, p. 182.
S. P. Walch and C. W. Bauschlicher, in Comparison of Ab Initio Quantum
Chemistry with Experiment, edited by R. Bartlett ͑Reidel, Boston, 1985͒.
T. C. Steimle and J. E. Shirley, J. Chem. Phys. 92, 3292 ͑1990͒.
D. A. Fletcher, K. Y. Jung, and T. C. Steimle, J. Chem. Phys. 99, 901
15
e
1
1
6
7
and PtS may prove difficult to reproduce by ab initio meth-
ods because they arise from a subtle balance between Pt to
N, O, or S charge transfer and polarization of the Pt-centered
electron density.
͑
1993͒.
18
T. C. Steimle, W.-L. Chang, D. F. Nachman, and J. M. Brown, J. Chem.
Phys. 89, 7172 ͑1989͒.
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155.33.109.21 On: Fri, 05 Dec 2014 02:04:25