Intermolecular Interactions between Formaldehyde and
Dimethyl Ether and between Formaldehyde and Dimethyl
Sulfide in the Complex, Investigated by Fourier Transform
Microwave Spectroscopy and Ab Initio Calculations
Yoshiyuki Kawashima, Yoshio Tatamitani, and Yoshihiro Osamura
Department of Applied Chemistry, Faculty of Engineering, Kanagawa Institute of
Technology, Atsugi, Kanagawa 240-0292, Japan
Eizi Hirota
The Graduate University for Advanced Studies, Hayama, Kanagawa 240-0193, Japan
Intermolecular Interactions (1)
Hydrogen bond
Dipole-dipole interaction
Van der Waals force
strong
weak
(DME)2, DME-DFE, DME-TFE, and
DMS-DME have three weak
hydrogen bonds:
C-H---Y (Y = O, S, and F)
Attention is paid to the roles of
these weak hydrogen bonds in the
supramolecules and related
biomolecules.
Y. Tatamitani et. al. J. Am. Chem. Soc. 124 (2002) 2739
Intermolecular Interactions (2)
We have been applying FTMW spectroscopy in a systematic way to
complexes consisting of molecules which are playing important roles in the
Earth’s atmosphere. We focus attention on the differences in the roles of
the O and S atoms in the intermolecular interactions. Y. Kawashima et. al.
CO
CO2
Ar
CO-EO
X
Dimethyl ether (DME)
Dimethyl sulfide (DMS)
Ethylene oxide (EO)
Ethylene sulfide (ES)
CO-ES
CO2-EO
J. Phys. Chem. 116 (2012) 1224
We concluded that the C atom of the
CO2 in CO2-EO and CO2-ES is bound to
the lone pair of O of the EO or of S of
the ES.
CO2-ES
Our aim is to obtain information on intramolecular interactions in the
H2CO-DME and H2CO-DMS.
c
θ
θ
c
a
a
τ
τ
H2CO-DME
H2CO-DMS
Stable conformers of the H2CO-DME and H2CO-DMS
Optimized at MP2/6-311++G(d, p)
H2CO-DME
H2CO-DMS
Conformer I (0 cm-1)
(τ = 90, θ = 90)
Conformer III (285 cm-1)
(τ = 0, θ = 90)
Conformer II (160 cm-1)
(τ = 90, θ = 0)
Conformer IV
(τ = 0, θ = 0)
(381 cm-1)
Conformer I
(0 cm-1)
(τ = 90, θ = 90)
Conformer III
(365 cm-1)
(τ = 0, θ = 90)
Conformer II (709 cm-1)
transition state
(τ = 90, θ = 0)
Conformer IV (640 cm-1)
(τ = 0, θ = 30)
Conformer V
(1083 cm-1)
Conformer V
(979 cm-1)
Fourier transform microwave (FTMW) spectrometer
heated nozzle 70℃
buffer gas
Heated nozzle: 70C
Sample ： paraformaldehyde(99%)
Backing pressure : 3.0 atm
Carrier gas
: 0.5%DME diluted with Ar
0.5%DMS diluted with Ar
Averaging ： 30  1000 shots
Frequency region : 9  20 GHz
Step： 0.25 MHz
Observed spectra of the sample; H2CO and 0.5%DME/Ar
DME monomer
H2CO monomer
Ar-DME dimer
Ar- H2CO
DME dimer
H2CO dimer
H2CO-DME
J=3←2
a-type transitions
J=2←1
a-type transitions
frequency /MHz
Observed spectra of the H2CO-DME, D2CO-DME, H2CO-DMS, and D2CO-DMS
Doppler doublet
MHz
MHz
Small splitting was observed for the H2CO-DME complex.
MHz
MHz
Molecular constants of the H2CO-DME, D2CO-DME, H2CO-DMS, and
D2CO-DMSa
H2CO-DME
(l)
A /MHz
B /MHz
C /MHz
ΔJ /kHz
ΔJK /kHz
ΔK /kHz
δJ /kHz
δK /kHz
ΦJ /Hz
ΦJK /Hz
σb /kHz
N(a-type)c /N(c-type)c /a
7188.75826 (42)
2516.73942 (27)
2214.43751 (23)
8.1223 (32)
50.309 (10)
-52.139 (39)
0.8960 (19)
1.083 (69)
----2.7
23
36
D2CO-DME
H2CO-DMS
D2CO-DMS
6776.26841 (70)
2440.75645 (25)
2163.41720 (24)
7.1283 (34)
38.914 (30)
-40.904 (60)
0.7383 (19)
-11.606 (56)
---3.22 (38)
3.5
24
34
4969.02089 (18)
2034.05601 (11)
1830.73775 (12)
3.8450 (14)
9.7091 (51)
-11.842 (11)
0.36957 (81)
2.329 (25)
----2.0
30
53
4754.66489 (30)
1968.22148 (31)
1784.46020 (26)
3.4532 (24)
7.7124 (70)
-9.725 (17)
0.3011 (47)
-0.451 (40)
-0.102 (49)
--3.6
29
55
(h)
7188.75282 (54)
2516.76200 (21)
2214.43540 (23)
8.1247 (28)
50.111 (26)
-52.132 (44)
0.8971 (15)
1.255 (58)
---2.96 (33)
3.0
23
43
The number in parentheses denotes 1σ.
Standard deviations.
c Number of fitting transitions.
Only H2CO-DME complex shows very small splittings.
b
Planar moment of inertia, Pbb
Comparison of observed and expected Pbb values (in uÅ2)
Complex
H2CO-DME
D2CO-DME
H2CO-DMS
D2CO-DMS
observed
48.858178
50.562281
64.649656
66.366479
expected
48.867
50.657
64.982
66.772
c
a
b
c
a
c
Pbb(complex) = Paa(DME/DMS) + Pbb(H2CO/D2CO)
Planar moments of inertia of monomers (in uÅ2)
Paa
Pbb
DME
47.047
--DMS
63.162
--It is concluded that the H2CO-DME and
H2CO
--1.82
H2CO-DMS complexes are of Cs symmetry.
D2CO
--3.61
Comparison of the experimental and ab initio calculated molecular
parameters of the H2CO-DME and H2CO-DMS a Optimized at
Parameter
A / MHz
B / MHz
C / MHz
H2CO-DME
Obsd
7188.7528 (6)
2516.7620 (2)
2214.4354 (2)
Rcm / Å
θ1 / °
θ2 / °
r(O--C) / Å
r(S--C) / Å
r1 / Å
r2 / Å
Van der Waals radii
O : 1.40 Å
S : 1.85 Å
C : 1.70 Å
r(O--C) = 3.10 Å
r(S--C) = 3.55 Å
ab initioa
7182.38
2666.98
2343.49
3.100
89.0
71.2
2.90
--2.93
2.71
2.984
73.4
79.0
2.71
--2.84
2.82
r1
θ1
r2
H2CO-DMS
Obsd
4969.02088 (18)
2034.05602 (12)
1830.73775 (12)
3.197
90.3
72.5
--3.02
3.04
2.88
ab initioa
4962.32
2080.35
1879.39
3.167
98.1
80.0
--3.15
3.26
2.60
r1
θ2
MP2/6-3111++G(d, p)
θ1
r2
θ2
Obtained bond distance Rcm, estimated force constants ks, binding energy EB, corrected
dissociation energy D0 + 50% CP, calculated stabilized energy of the charge transfer CT
of the H2CO-DME, H2CO-DMS, and related complexes
Parameter
A-B complex
Rcm
ks
EB
Ar-DME
CO-DME
CO2-DME
DFE-DME
H2CO-DME
DME-DME
DMS-DME
TFE-DME
IPOHa-DME
Ar-DMS
CO-DMS
H2CO-DMS
H2CO-H2CO
3.583
3.682
3.255
4.00
3.102
3.837
3.970
4.01
4.087
3.80
3.789
3.200
3.04
2.3
1.4
10.9
3.6
6.5
5.3
5.7
4.5
7.5
2.0
2.7
7.9
7.0
2.5
1.6
9.7
4.8
5.2
4.7
7.6
6.0
10.4
2.4
3.3
6.7
5.3
a
D0+50%CP
CT
1.3
4.3
9.2
10.4
9.9
10.1
12.0
14.3
21.4
2.4
3.9
10.5
8.2
2.5
8.4
24.3
13.9
27.9
13.8
19.5
21.0
61.2
2.1
8.8
35.4
24.8
contributions of the CT
A→B B→A
0.6
4.0
8.0
1.4
4.2
6.4
4.1
8.6
4.7
0.8
2.2
6.4
5.3
1.9
4.4
16.2
12.5
23.8
7.5
16.9
10.9
56.6
1.3
6.6
28.9
19.5
IPOH denotes iso-propanol.
Ionization potential
Ip(DME) = 10.03 eV
Ip(DMS) = 8.69 eV
NBO analysis with its implications for molecular
structure and the stabilization energy through CT of
the H2CO-DME and H2CO-DMS
Relationship between the binding
energy EB and the stabilized energy
of the charge transfer CT of the
H2CO-DME, H2CO-DMS, and the
related complexes.
The blue line indicates the good
correlation between the complexes
which have small contributions of
the CT.
The red line shows that CT for
H2CO-DME, H2CO-DMS, and
(H2CO)2 are about five times larger
than EB.
V(τ) and V(θ) of the H2CO-DME and
H2CO-DMS against τ and θ
It is not easy to explain the observed
small splittings of the H2CO-DME.
H2CO-DME
H2CO-DMS
V(θ)
V(θ)
cm-1
cm-1
V(θ)
V(τ)
V(τ)
V(θ)
τ or θ /
τ or θ /
summary
1. H2CO-DME and H2CO-DMS complexes are detected using FTMW spectroscopy.
2. The binding energy of the H2CO-DMS is larger than that of the H2CO-DME.
3. DME is strongly hydrogen bonded to other molecule, while H2CO behaves as a strong
electron acceptor. The ionization potentials of the DME and DMS are 10.0 and 8.69 eV,
respectively, therefore CT is larger in the H2CO-DMS than in the H2CO-DME.
EB = 5.2 kJ/mol
CT = 27.9 kJ/mol
Rcm = 3.102 Å
H2CO-DME
EB = 6.7 kJ/mol
CT = 35.4 kJ/mol
Rcm = 3.200 Å
H2CO-DMS