The differences in the role of O and S atoms in the
molecular structure and dynamics of some
complexes
Yoshiyuki Kawashima,1 Akinori Sato,1 Yoshio Tatamitani,1
Nobuyuki Ohashi,2 James M. Lobue,3 and Eizi Hirota4
1Kanagawa
Institute of Technology
2Kanazawa University
3Georgia Southern University
4The Graduate University for Advanced Studies
Purpose
We have investigated van der Waals complexes containing of either one of a
rare gas atom, CO, N2, or CO2 combined with one of the two pair
molecules: DME/DMS and EO/ES by using a FTMW spectrometer,
in order to examine how different the role of the O and S atoms is in
molecular properties of the complex.
The present talk reports the results on Ar-DMS and CO-EO, in comparison
with those on Ar-DME and CO-ES, respectively.
Ar–dimethyl sulfide (DMS)
CO–ethylene oxide (EO)
Potential of the tunneling motion for Rg-DME complexes；Rg = Ne, Ar and Kr
The large amplitude motion is expected in the weak van der Waals complex.
C2v
Rg
E / cm–1
Rc.m.
a
Binv
1–
v= +
1
0+–
v= 0
1
R  L
 
2

1
R  L
2

 
L
Ne–DME: 16 cm–1
Ar–DME: 58 cm–1
Kr–DME: 112 cm–1
Binv:
Barrier to inversion
DE
0
R
807.2(9) MHz
0.9980(6) MHz
0.26 (5) MHz
a / deg
CO-dimethyl ether (DME) complex1)

Heavy-atom skeleton of CO-DME was
essentially planar. The carbon atom of CO is
closer to DME than the O atom.

The splitting between the two sets of the same
transition varied from 2 to 15 MHz, and the
two components were assigned to the two
lowest states of the internal rotation of CO
with respect to DME governed by a twofold
potential.

The bond distance between the center of mass
is 3.68 Å. The van der Waals bonding of CODME is weak and is between those of NeDME and Ar-DME.
75.7°
Rc.m. = 3.68 Å
1)
Y. Kawashima et al, J. Chem. Phys. 127, 194302 (2007)
Experimental
Instrument: Fourier transform microwave spectrometer
Sample : 1% DMS diluted with Ar
or 0.5% EO and 1.5% CO diluted with Ar
Backing pressure : 1.0 atm
Shots : 20
Frequency region : 3.7~25 GHz
Step : 0.25 MHz
Vacuum chamber
Mirror (fixed)
Supersonic molecular
beam injection
Molecular beam injection nozzle
MW
Mirror (mobile)
sample
Diffusion pump
Rotary pump
Observed spectra of Ar-DMS
Ar–DMS (normal)
221 – 111
c(vdW)
b(DMS)
Spectrum of Ar–DME
212(+) – 202(–)
212(–) – 202(+)
220 – 110
111(+) – 101(–)
a
111(–) – 101(+) (vdW
)
DE ≈ 1 MHz
7050
7100
7150
7200
7250
7300
220 – 110
220 – 110
221 – 111
221 – 111
18200
No splitting due to
the large amplitude
motion is found!
Ar–DMS (34S)
Ar–DMS (13C)
18000
7350
18400
18600
Frequency / MHz
18800
19000
Observed spectra of the a-type and c-type transitions of Ar-DMS
a-type transition
c-type transition
EE
505–404
211–101
AE
EA
AE
EA
AA
EE
AA
12665.8 9823.9
12665.3
Frequency / MHz
9824.4
Frequency / MHz
V3 = 736.17 (32) cm-1
(V3 = 752.7 cm-1 for DMS monomer)
Observed spectra of the forbidden transitions of Ar-DMS
Forbidden transitions
Forbidden transitions
Phenomenological Hamiltonian
H   hk Rk  iqJ z
The first-order Coriolis term
k
h R
k
k
 AJ z  BJ x  CJ y  D J J  D JK J J z  D K J z
2
2
2
4
2
2
4
k
  J 2J ( J x  J y )   K [ J z ( J x  J y )  ( J x  J y ) J z ]   K J z .
2
2
2
2
2
2
2
2
2
6
| 3  1 | q | 2 || 2 F a1 EE | p1 | EE  2 F a 2  EE | p 2 | EE 
 2 F12  a 2  EE | p1 | EE  2 F12  a1 EE | p 2 | EE |,
H internal-rotation
where
1
1
 F ( p1  p 2 )  2 F12 p1 p 2  V3 (1  cos 31 )  V3 (1  cos 3 2 ),
2
2
 a1  a1
2
2
I CH 3 ( top1)
Ia
,  a 2  a 2
I CH 3 ( top 2)
Ia
Molecular constants and the substituted coordinates of the S and C atoms in Ar-DMS
Ar–DMS (normal)
Ar–(CH3)234S
Ar–13CH3SCH3
A / MHz
5819.71216(22)
5778.88622(20)
5677.33741(42)
B
/ MHz
1334.991997(71)
1315.99190(11)
1327.59112(24)
C
/ MHz
1209.047917(10)
1195.23069(12)
1198.51825(27)
DJ / kHz
DJK / kHz
DK / kHz
J / kHz
K / kHz
5.80475(46)
40.9120(45)
–39.911(19)
0.52885(16)
25.669(24)
5.67154(48)
39.210(7)
–38.075(24)
0.50346(17)
24.52(5)
5.6862(11)
40.275(15)
–39.77(8)
0.53750(32)
25.15(12)
K / kHz
0.0962(24)
–
–
<1|q|2> / MHz
0.03556(11)
–
–
Na-type / -
43
16
0
Nc-type / -
79
39
25
s / kHz
3.8
0.6
0.6
as (S or C) / Å
1.5713
1.3420
bs (S or C) / Å
0.0715 i
cs (S or C) / Å
0.5684
rs coordinates
±1.3707
0.5713
Observed rotational spectra of CO-EO in Ar
J = 5←4
CO-EO complex
J = 1←0
EO monomer
Ar-EO complex
a-type R-branch transitons
c-type R-branch transitions
c-type Q-branch transitions
J = 4 ←3
J = 2←1
J = 3←2
8000
10000
12000
14000
16000
5
18000
20000
J=1
CO-EO complex
C-type Q-branch transitions(Ka=1←0)
8000
8000
8000
10000
11200 10000
10000
12000
11300
12000
12000
14000
16000 11500 18000
18000
11400
14000
16000
14000
16000
18000
Frequency / MHz
20000
11600
20000
20000
Observed rotational spectra and obtained molecular constants of CO-EO complex
The a-type and strong c-type transitions of CO-EO
complex were observed, however, no b-type transition
was found.
404–303
(a-type transition)
•The rotational and centrifugal distortion constants of
CO-EO were determined using an asymmetric top
Hamiltonian.
16033.6379 MHz
normal
16033.2
Frequency / MHz
16034.0
B /MHz
C /MHz
DJ /kHz
DJK /kHz
DK /kHz
d1 /Hz
d2 /Hz
N (a-type)
N (c-type)
s /kHz
110–000
(c-type transition)
15567.4151 MHz
15567.0
15567.8
Frequency / MHz
A /MHz
13556.4299(7)
2011.19621(8)
1997.86910(9)
9.7986(10)
44.185(5)
83.41(13)
–3.04(7)
46.2(7)
33
34
1.98
Molecular constants and the substituted coordinates of the O and C atoms of
five isotopomers of CO–EO complex
normal
A /MHz
13556.4299(7)
CO–EO(13C)
13337.9534(4)
CO–EO(18O)
13CO–EO
C18O–EO
13184.7208(26)
13437.5762(11)
13506.9965(4)
B /MHz
2011.19621(8)
1990.28772(9)
1989.1126(4)
1984.01857(31)
1917.24067(6)
C /MHz
1997.86910(9)
1973.41181(11)
1984.4680(7)
1973.64698(18)
1906.08012(6)
DJ /kHz
9.7986(10)
9.5212(16)
9.686(11)
9.4950(24)
9.0345(9)
DJK /kHz
44.185(5)
44.183(13)
43.96(14)
40.326(11)
38.9515(33)
DK /kHz
83.41(13)
[83.41] a
[83.41] a
86.76(23)
90.96(9)
d1 /Hz
–3.04(7)
15.2(5)
–3.04(7)
20.95(20)
10.01(5)
d2 /Hz
46.2(7)
38.8(13)
46.2(7)
48.9(12)
40.2(4)
Pbb /uÅ2
19.4779
20.0309
19.4627
19.4740
19.4798
N (a-type)
33
16
11
31
33
N (c-type)
34
14
12
19
21
s /kHz
rS coordinates
|C(a)| or |O(a)/Å
|C(b)| or |O(b)/Å
|C(c)| or |O(c)/Å
1.98
1.03
5.59
3.12
1.613
0.739
0.280
1.613
0.054 i
0.739
1.771
0.057
0.584
1.20
2.498
0.030
0.270
Observed and ab initio calculated two structural parameters, stretching force constants, and
binding energy or Ar-DMS and related molecules
Experimental
ab initio
ab initio
Experimental
Molecule
R cm /Å
α/°
R cm /Å
α /°
k S /Nm-1
E B / kJmol-1
k S /Nm-1
E B / kJmol-1
Ne-DME
3.449
53.4
3.398
75.3
1.0
1.0
0.89
1.48
3.449
3.457
47.0
53.4
Ar-DME
3.578
3.578
3.581
64.8
60.1
64.8
3.508
74.1
2.3
2.5
2.49
3.67
Ne-DMS
3.715
3.175
3.712
109.7
108.7
109.7
3.624
102.0
0.573(3)
0.66(15)
0.97
1.33
Ar-DMS
3.796
3.796
3.796
104.9
104.6
104.9
3.797
101.9
2.0
2.4
2.38
3.15
[I aa(vdW) and Ibb(vdW)]
[Ibb(vdW) and Icc (vdW)]
[Iaa(vdW) and Icc(vdW)]
Ne
a
Rcm
Ne–DME
a
Ar
Rcm
Ar–DME
a
a
Rcm
Ne–DMS
Rcm
Ne
Ar–DMS
Ar
t / degrees
cm–1
Rc.m.
t
a / degrees
a
Summary
Ar
CO
R(O-Ar)=3.382Å
DME
R(O-C)=3.047Å
106.8 °
ks=2.30 Nm-1
R(S-Ar)=3.989Å
DMS
66.9 °
ks=1.40 Nm-1
R(S-C)=3.49Å
75.7 °
ks=2.70 Nm-1
ks=2.00 Nm-1
R(O-Ar)=3.476Å
EO
93.0 °
ks=2.20
Nm-1
R(O-Ar)=3.974Å
ES
R(O-C)=3.00Å
97.7 °
ks=3.30 Nm-1
R(S-C)=3.47Å
74.6 °
70.7 °
ks=2.10 Nm-1
ks=3.20 Nm-1
Summary
CO
HF
7.2 º
DME
R(O-C)=3.047Å
137.1 °
ks=1.40 Nm-1
R(S-C)=3.49Å
DMS
75.7 °
ks=2.70 Nm-1
16.5 °
R(O-C)=3.00Å
EO
108.0 °
97.7 °
ks=3.30 Nm-1
R(S-C)=3.47Å
ES
86.5 °
74.6 °
ks=3.20 Nm-1
16.8 °
Conclusion
1) In the case of the CO-DMS and CO-ES, the CO moiety is located
closer to the CH3 and CH2 end of DMS and ES, respectively,
whereas to the O end in the cases of CO-DME and CO-EO.
2) Similar differences were found for Rg complexes. Because of the
larger atomic radius and lower electronegativity of S than those
of O, S behaves as a much weaker nucleophile than O.
3) The structures of Rg-DMS and Rg-ES thus considerably deviate
from that of the n-type complex proposed by Legon.
A.C. Legon, Angew. Chem. Int. Ed. 38 (1999) 2686.