FTIR studies of the CH3CN-BF3 complex in solid Ar, N2, and Xe: Matrix effects on vibrational spectra

Article abstract of DOI:10.1016/j.molstruc.2005.04.016

FTIR spectra of the four isotopically substituted 1:1 complexes of acetonitrile and boron trifluoride were recorded in Ar, N₂ and Xe matrices. In Ar, previously unreported three vibrational modes of the complex were clearly observed. Several si

Full text of DOI:10.1016/j.molstruc.2005.04.016

Journal of Molecular Structure 750 (2005) 123–134
www.elsevier.com/locate/molstruc
FTIR studies of the CH CN–BF complex in solid
3
3
Ar, N , and Xe: Matrix effects on vibrational spectra
2
Ryuichi Hattori, Eiichi Suzuki , Kenji Shimizu
*
Department of Chemical Engineering, Iwate University, 020-8551 Morioka, Japan
Received 30 January 2005; revised 22 April 2005; accepted 24 April 2005
Available online 14 June 2005
Abstract
FTIR spectra of the four isotopically substituted 1:1 complexes of acetonitrile and boron trifluoride were recorded in Ar, N and Xe
2
matrices. In Ar, previously unreported three vibrational modes of the complex were clearly observed. Several significant vibrational bands
were also observed in N and Xe. The observed frequency shifts on complexation, Dn, were qualitatively in good agreement with the
2
computational results, which were calculated at the B3LYP/6-311CCG(d,p) level using the optimized geometry of the C3v eclipsed
conformation. The observed magnitudes of Dn for most of the complex bands were larger than the calculated values. The BF symmetric
3
deformation mode is an exception. The observed frequency shits for this mode were smaller than the calculated values, especially in N
suggests that even an inert matrix can significantly affect the vibrational spectrum of the complex.
q 2005 Elsevier B.V. All rights reserved.
2
. This
Keywords: Matrix isolation; Infrared spectroscopy; Matrix effects; Acetonitrile; Boron trifluoride
1
. Introduction
a reasonable basis set [28] showed the B–N bond length of
˚
.8008 A and the FBN bond angle of 101.208, both of which
1
Structures and bondings of the electron donor-acceptor
are intermediate between the crystalline and the gas phase
values.
(
EDA) complexes containing boron trifluoride have been
the subject of many experimental [1–11] and theoretical
12–15] studies. After the first preparation of the 1:1 adduct
Recently, Giesen et al. precisely studied the structure of
the CH CN–BF complex, especially the difference
[
3
3
of boron trifluoride with acetonitrile [16], it has attracted
attention for its significant difference of the B–N bond
lengths between the crystalline and the gas phases [17–23].
X-ray crystallography showed that the B–N bond length and
the FBN bond angle of CH CN–BF in the crystalline solid
between the gas phase and the theoretical results, and the
characteristics of the BN bond by the MP2 and B3LYP
levels of calculations with larger basis sets [29]. According
to their results, two local minima along with the B–N
distance were obtained at the B3LYP level using sufficiently
3
3
˚
were 1.630 A and 105.68, respectively [19]. On the other
hand, Dvorak et al. investigated the microwave spectra of
the complex in the gas phase [21]. They reported that the
B–N bond length and the FBN bond angle in the gas phase
˚
large basis sets. The longer B–N length of 2.315 A was the
global minimum for the largest aug-cc-pVQZ basis.
However, the energy difference between the two minima
is lower than 0.2 kcal/mol and the potential curve along with
˚
were 2.011 A and 95.68, respectively, based on the analysis
˚
the B–N coordinate is extremely flat from 1.8 to 2.5 A. They
in which other structural parameters were constrained to the
values of the component monomers. Theoretical studies on
the structure of the complex including medium effects have
also been published [24–29]. The MP2 calculation with
suggested that the difference between the B–N distance
averaged over this flat potential and the equilibrium bond
length is responsible for the discrepancy between the gas
phase and the theoretical structures.
The vibrational spectra of the CH CN–BF complex
3
3
*
Corresponding author. Tel./fax.: C81 19 621 6344.
E-mail address: esuzuki@iwate-u.ac.jp (E. Suzuki).
were also observed in the solid phase [18,20] and the Ar
matrix [22,23]. The blue shift of the CN stretching mode on
complexation and the characteristics of the BN bond have
been the matters of interest. Comparisons of the calculated
0
022-2860/$ - see front matter q 2005 Elsevier B.V. All rights reserved.
doi:10.1016/j.molstruc.2005.04.016

124
R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
and the experimental vibrational frequencies were also
reported [28,29]. Roughly speaking, the vibrational fre-
quencies of the complex in an Ar matrix are similar to the
calculated values rather than the frequencies in the crystal-
line phase. This seems to indicate the structural similarity
between the calculated and the matrix isolated complexes.
Giesen et al. [29], however, suggested that the B–N bond
length of the complex in an Ar matrix is somewhat shorter
Gaussian03 program [31]. Geometry optimizations were
performed using the ‘optZverytight’ option. Harmonic
vibrational frequencies were calculated numerically for
MP2 and analytically for B3LYP.
3. Results and discussion
˚
than that of the short minimum geometry (1.919 A)
3.1. Optimized geometry and harmonic frequencies
of the CH CN–BF complex
optimized at the B3LYP/aug-cc-pVQZ level. They inves-
tigated the effect of Ar matrix environment on the
equilibrium geometry of the complex using the SCRF
CPCM model, and showed the significant shortening of the
B–N bond length, which indicates that even a very low
dielectric medium can dramatically change the shape of the
B–N potential surface.
3
3
Several computational studies on the structure and the
vibrational frequencies of the CH CN–BF complex have
3
3
been published previously [24–29]. However, we had to
know the calculated harmonic frequencies of some iso-
topically substituted species, which can be used for the
vibrational assignment of all the observed frequencies.
Therefore, we also calculated the optimized geometry and
the harmonic frequencies of the complex at the MP2 and
B3LYP levels with some standard basis sets. According to
the previous studies [28,29], the eclipsed conformation with
C3v symmetry was assumed during the geometry optimiz-
ation. The important geometrical parameters of the 1:1
CH CN–BF complex are presented in Fig. 1. The optimized
Vibrational spectroscopic studies of the CH CN–BF3
3
complex in matrices other than Ar are expected to give more
information about the matrix effects on the structure and
vibrational frequencies of the complex. In this paper, we
present the FTIR spectra of the CH CN–BF complex
3
3
including its isotopically substituted species in solid N and
2
Xe, together with some previously unreported vibrational
modes in Ar. Matrix effects on the vibrational spectra,
especially the frequency shift on complexation are also
discussed.
3
3
values of these parameters and the harmonic frequencies for
1
the CH CN– BF species are compared with previously
1
3
3
reported results in Tables 1 and 2. Note that the mode
numbering scheme in Table 2 is that from Cho et al. [28].
Table 1 shows that the B–N bond length and the FBN
bond angle have somewhat large dependence on the level of
calculation. A significant shortening of the B–N bond length
on introducing the diffuse functions [29] was also found for
our basis sets. For B3LYP, most of the geometrical
parameters calculated with the 6-311CCG(d,p) and
6-311G(d,p) basis sets are similar to those calculated with
the larger aug-cc-pVTZ and aug-cc-pVQZ basis sets,
respectively. However, the B–N bond length at the
B3LYP/6-311CCG(d,p) level is somewhat shorter than
that at the B3LYP/aug-cc-pVTZ, and closer to the value at
the MP2/6-31CG(2d,p) level. The B–N, CN and CC bond
lengths at the B3LYP level are slightly shorter than those at
the MP2 level with the same basis set. The CN and CC bond
2
. Experimental and computational methods
BF (99.99%) was purchased from Takachiho Chemical
3
1
0
10
Industrial Co., Ltd BF was prepared from B O
2 3
3
1
0
(
mixing of HF (Morita Chemical Industries Co., Ltd.),
Aldrich, 99%) and Na BF [30], which was prepared by
4
1
3
0
H BO (Aldrich, 99%) and Na CO (Kanto Kagaku,
3
2
3
9
9.5%). CH CN (99.5%) and CD CN (99.8%) were
3 3
purchased from Wako Pure Chemical Industries, Ltd. and
Aldrich, respectively. All samples were purified by the
trap-to-trap method in an all-glass vacuum line. Matrix
gases, Ar (Nippon Sanso, 99.9995%), N (Nippon Sanso,
2
9
without further purification. The mixtures of CH CN and
9.9995%) and Xe (Takachiho, 99.99%), were used
3
BF with excess matrix gases were prepared using standard
3
lengths of the CH CN monomer in the gas phase are 1.1572
3
˚
and 1.4596 A, respectively [32]. Since the shortenings
of these bonds are expected on complexation, the B3LYP
manometric techniques. CH CN/M and BF /M (MZAr,
N ) were co-deposited on a CsI plate maintained at 20 or
2
3
3
1
3
2 K. Subsequent annealing procedures were carried out at
3 K. For CH CN/Xe and BF /Xe, co-deposition and
3
3
annealing temperatures were 30 and 60 K, respectively.
The cryostat used was CTI Cryogenics LT-21, coupled
with Tristan Technologies, Inc. LTC-20 temperature
controller. Reagent/matrix ratios (R/M) were in the range
of 1/200–1/400. All spectra were recorded on a Nicolet
Magna 750 FTIR spectrometer, in the wavenumber range
K1
K1
from 4000 to 400 cm at 1 cm resolution.
The MP2 and B3LYP calculations were carried out with
several basis sets of valence triple-zeta level using
Fig. 1. Optimized geometry of the 1:1 CH
3 3
CN–BF complex. Determined
values of geometrical parameters are listed in Table 1.

R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
125
Table 1
3 3
Geometrical parameters of the 1:1 CH CN–BF complex optimized at various levels of calculation
Parameter
B3LYP/6-
B3LYP/6-
311G(d,p)
MP2/6-311CC
a
G(d,p)
MP2/6-
MP2/6-31C
b
G(2d,p)
B3LYP/aug-cc-
c
pVTZ
B3LYP/aug-cc-
c
pVQZ
311CCG(d,p)
311G(d,p)
˚
Bond length [A]
R(CC)
1.450
1.092
1.144
1.796
1.359
1.454
1.092
1.149
2.327
1.326
1.458
1.091
1.164
1.804
1.356
1.461
1.091
1.170
2.381
1.324
1.459
1.089
1.164
1.801
1.356
1.449
1.089
1.142
1.868
1.349
1.452
1.089
1.145
2.315
1.323
R(CH)
R(CN)
R(BN)
R(BF)
Bond angle [8]
q (HCC)
109.7
101.8
110.0
94.7
109.4
101.4
109.7
93.9
109.5
101.2
109.7
100.8
110.0
95.1
q (FBN)
a
One imaginary frequency associated with torsional mode was obtained.
b
c
Ref. [28].
Ref. [29].
results for the complex seem to be more reliable. The MP2/
-311CCG(d,p) level of calculation for the C3v eclipsed
complexation, Dn. On the other hand, Dn of the CN
stretching and BF degenerate stretching calculated at the
6
3
conformation gave one imaginary frequency corresponding
to the torsional mode. Similar imaginary frequencies were
also obtained for the C3v staggered and C conformations.
B3LYP/6-311CCG(d,p) are obviously different from those
˚
at the long minimum (R(BN)Z2.315 A, the global mini-
mum) of the B3LYP/aug-cc-pVQZ. Giesen et al. predicted
that the B–N bond length of the complex in an Ar matrix is
˚
shorter than 1.919 A [29]. Therefore, the harmonic
3
These results suggest that the torsional motion of the
complex is almost free rotation.
The harmonic frequencies calculated at the B3LYP/
frequencies calculated at the optimized geometry of the
˚
6-311CCG(d,p) level in Table 2 are qualitatively corre-
sponding to those at the MP2/6-31CG(2d,p) and those at
B3LYP/6-311CCG(d,p) level (R(BN)Z1.796 A) are
expected to be sufficiently useful for the vibrational
assignment of the complexes observed in low temperature
matrices.
˚
the short minimum (R(BN)Z1.919 A) of the B3LYP/aug-cc-
pVQZ, especially in terms of the frequency shift on
Table 2
K1
Comparison of calculated harmonic frequencies (cm ) of CH
11
CN– BF
3
3
complex
a
b
c
Mode
B3LYP/6-311CCG(d,p)
MP2/6-31CG(2d,p)
B3LYP/aug-cc-pVQZ
Approximate
d
description
˚
˚
˚
˚
R(BN)Z1.796 A
R(BN)Z1.801 A
R(BN)Z1.919 A
R(BN)Z2.315 A
e
Dn
e
e
e
Dn
n
monomer
n
complex
n
monomer
n
complex
Dn
n
monomer
n
complex
Dn
n
complex
a
1
n
n
n
n
n
n
n
n
n
n
n
n
1
3046.2
2362.6
1411.5
929.8
–
3050.6
2435.6
1409.3
958.7
174.1
809.8
578.9
14.7
C4.4 3125.2
C73.0 2206.4
K2.2 1437.6
3128.1
2301.8
1435.2
958.0
178.9
812.5
573.8
11.0
C2.9 3047
C95.4 2363
K2.4 1415
3051
2421
1413
951
47
C4
C58
K2
C23
–
3050 C3
2391 C28
1414 K1
938 C10
CH
CN str
CH sym def
CC str
3
sym str
2
3
3
4
C28.9
–
926.1
–
C31.9
–
928
–
11
11
11
5
63
859
–
BN str
6
869.0
682.0
–
K59.2
K103.1
–
868.0
721.4
–
K55.5
K147.6
–
884
684
830
564
22
K54
K120
–
K25
K97
–
BF
BF
3
sym str
sym def
7
587
3
a
e
2
8
–
20
Torsion
9
3116.1
1474.9
1061.3
381.9
3126.5
1464.8
1059.7
416.1
C10.4 3222.6
K10.1 1513.2
K1.6 1074.2
3230.6
1503.8
1073.3
404.5
C8.0
K9.4
K0.9
C44.4
3116 3125
1475 1468
1063 1062
C9
K7
K1
C32
3121
1472
1063
396
C5 CH
K3 CH
3
3
3
deg str
deg def
rock
10
11
12
0
CH
C34.2
360.1
380
412
C16 CCN
1
1
bendC BF
deg def
3
11
n
n
13
14
1417.1
465.8
1242.4
494.2
K174.7 1426.6
C28.4
1260.4
490.5
K166.2
C8.7
1441 1306
K135
C12
1395
474
K46
K1
BF
BF
3
deg str
11
481.8
475
487
3
deg defC
CCN bend
1
1
n
n
15
16
–
–
285.9
70.1
–
–
–
–
279.5
69.3
–
–
–
266
59
–
–
187
42
–
–
BF
3
rock
11
–
BNC bend
a
Mode-numbering scheme is taken from Cho et al. [28].
b
c
d
e
Cho et al. [28] calculated frequencies by GAMESS package. Listed values in the table were calculated by Gaussian 03.
K1
Frequencies higher than 2000 cm in Ref. [29] were scaled by 0.96. Listed frequencies are converted unscaled values.
Abbreviations used: sym, symmetric; deg, degenerate; str, stretch; def, deformation.
DnZncomplexKnmonomer
.

126
R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
3.2. Observed vibrational frequencies in Ar, N2
and Xe matrices
0
.5
The FTIR spectra of CH CN and BF co-deposited in
3
(a)
3
low temperature Ar, N and Xe matrices are shown in
2
Figs. 2–4. The absorptions that can be assigned to the
CH CN–BF complex, which were absent in the spectra
1
.0
3
3
10
of free monomers, are indicated with arrows. In addition
to the previously reported three major absorptions [23],
several new features were observed near the CH CN
(b)
3
monomer bands in the Ar matrix spectra. Fewer
vibrational modes of the complexes were observed in
N2 and Xe than in Ar. Some significant frequency
differences among the matrices are observed in these
bands. The vibrational assignment of the complex bands
was carried out using the calculated harmonic frequencies
at the B3LYP/6-311CCG(d,p) level. The fundamental
0
.5
(c)
1
600
1500
1400
Wavenumber /cm–1
1300
1200
1100
Fig. 3. FTIR spectra of acetonitrile and boron trifluoride co-
K1
deposited in low temperature matrices, in the 1600–1100 cm
frequencies of the CH CN–BF3 complexes including
3
isotopically substituted species together with the
calculated values are summarized in Tables 3–6. Detailed
descriptions on the absorptions assigned to the complexes
in each characteristic frequency region are presented in
the following sections. In reference to the component
monomers, the vibrational frequencies of CD CN in N ,
3 3 3 3 2
region. (a) CH CN/BF /ArZ1/1/400, 20 K; (b) CH CN/BF /N Z
1/1/400, 20 K; (c) CH CN/BF /XeZ1/1/400, 30 K. The bands
3
3
assigned to the CH CN–BF
3
3
complex are indicated with arrows.
3
.2.1. CH(D) degenerate stretching (n ) and CH(D)
3 9 3
3
2
symmetric stretching (n1)
In the spectrum of CH CN/BF /Ar, the CH degenerate
CH CN, CD CN and BF in Xe have not been previously
3
3
3
3
3
3
reported. Therefore, the assignments of these monomer
absorptions, which were made by comparison with the
reported frequencies in the gas phase and in other
matrices [11,33–39], are also described.
stretching (n ) absorptions assigned to the complex were
9
K1
observed as a slightly split band at 3022.0/3021.0 cm and
K1
a shoulder at 3018.8 cm , which are in the higher
frequency region of the CH CN monomer absorption
3
K1
at 3007.2 cm . The corresponding absorptions for
0
.05
0
.1
(a)
(a)
0
.1
0.4
6
(b)
(b)
0
.1
0
.05
(c)
(c)
3
000
2900
Wavenumber /cm–1
2300
2200
900
800
700
Wavenumber /cm–1
600
500
Fig. 2. FTIR spectra of acetonitrile and boron trifluoride co-deposited in
K1
low temperature matrices, in the 3050–2900 and 2400–2200 cm regions.
Fig. 4. FTIR spectra of acetonitrile and boron trifluoride co-deposited in
K1
low temperature matrices, in the 900–450 cm region. (a) CH
ArZ1/1/400, 20 K; (b) CH CN/BF /N Z1/1/400, 20 K; (c) CH
3
CN/BF
CN/BF
3
/
/
(a) CH
c) CH
3
CN/BF
CN/BF
3
/ArZ1/1/400, 20 K; (b) CH
3
CN/BF
3
/N
2
Z1/1/400, 20 K;
CN–
3
3
2
3
3
(
3
3
/XeZ1/1/400, 30 K. The bands assigned to the CH
3
3 3
XeZ1/1/400, 30 K. The bands assigned to the CH CN–BF complex are
BF
3
complex are indicated with arrows.
indicated with arrows.

R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
127
Table 3
K1
Calculated and experimental fundamental frequencies (cm ) of CH
11
CN– BF
3
3
complex
a
Mode
Calculated
Experimental
in Ar
Approximate
b
description
B3LYP/6-311CCG(d,p)
in N
2
in Xe
n
complex
n
monom- Dn
n
complex
n
monom- Dn
n
complex
nmonom- Dn
n
complex
nmonom- Dn
er
er
er
er
a
1
n
n
n
n
n
n
n
1
2
3
4
5
6
7
3050.6 3046.2
2435.6 2362.6
1409.3 1411.5
C4.4 2953.6 2950.4
C73.0 2365.6 2258.3 C107.3 2367.0 2257.2 C109.8 2357.6 2262.3
C3.2
–
2949.6
–
–
2939.4
–
CH
C95.3 CN str
K3.4 CH sym def
CC str
3
sym str
c
K2.2 1374.3 1375.7
c
K1.4 1377.4 1378.6
K1.2 1368.2 1371.6
3
958.7
174.1
809.8
578.9
929.8
–
C28.9
–
–
–
916.5
–
–
–
–
–
917.5
–
–
–
–
–
927.1
–
–
11
–
K71.6
K73.7
K44.3
–
BN str
c
c
c
11
869.0 K59.2 811.7
682.0 K103.1 601.2
876.0
675.9
K64.3 835.8
K74.7 625.3
K44.1 617.1
879.9
657.6
K44.1 809.0
K32.3 601.7
K40.5 631.1
880.6
675.4
BF
BF
3
sym str
sym def
1
1
3
d
d
d
6
31.8
–
a
2
n
n
n
n
n
8
14.7
–
–
–
–
C14.8
–
–
–
–
–
–
–
3009.7
1446.5
1041.0
–
–
–
–
–
–
–
–
–
–
Torsion
9
3126.5 3116.1
C10.4 3022.0 3007.2
K10.1 1445.4
K1.6 1036.8 1038.2
C34.2
2997.5
1437.7
–
CH
CH
3
3
3
deg str
deg def
rock
10 1464.8 1474.9
11 1059.7 1061.3
–
–
c
K1.4
–
1033.2 1036.1
K2.9 CH
–
1
1
12
416.1
381.9
–
–
–
–
CCN bendC BF
3
deg def
1
1
n13 1242.4 1417.1 K174.7 1248.7 1447.2 K198.5 1235.0 1443.2 K208.2 1239.0 1440.1 K201.1
BF
BF
3
deg str
11
n
14
494.2
465.8
C28.4 502.9
479.7
C23.2
–
479.2
–
502.5
477.8
C24.7
3
deg defC
CCN bend
1
1
n
n
15
285.9
70.1
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
BF
3
rock
11
16
BNC bend
a
Mode-numbering scheme is taken from Cho et al. [28].
b
c
d
Abbreviations used: sym, symmetric; deg, degenerate; str, stretch; def, deformation.
Tentative assignment.
Minor site.
Table 4
K1
10
3 3
Calculated and experimental fundamental frequencies (cm ) of CH CN– BF complex
a
Mode
Calculated
Experimental
in Ar
Approximate
b
description
B3LYP/6-311CCG(d,p)
in N
2
in Xe
n
complex
n
monom-
Dn
n
complex
n
monom-
Dn
n
complex
n
monom-
Dn
n
complex
n
monom-
Dn
er
er
er
er
a
1
n
n
n
n
n
n
n
1
2
3
4
5
6
7
3050.6
2435.6
1409.3
958.9
175.6
814.5
595.6
3046.2
2362.6
1411.5
929.8
–
C4.4 2953.4
C73.0 2365.7
K2.2 1374.3
2950.4
2258.3
1375.7
916.5
–
C3.0
–
2949.6
2257.2
1378.6
917.5
–
–
–
2939.4
2262.3
1371.6
927.1
–
–
CH
C95.3 CN str
K3.3 CH sym def
CC str
3
sym str
C107.4 2367.0
K1.4 1377.4
C109.8 2357.6
K1.2 1368.3
c
c
3
C29.1
–
–
–
–
–
–
–
–
–
–
–
–
10
–
BN str
c
c
c
10
869.0
709.9
K54.5
813.5
618.0
876.0
703.1
K62.5
K85.1
K56.8
–
843.5
879.9
683.6
K36.4
810.8
616.9
645.6
–
880.6
702.4
K69.8
BF
3
3
sym str
sym def
10
K114.3
640.6
K43.0
K85.5
BF
d
d
d
6
46.3
–
633.0
K50.6
K56.8
a
e
2
n
n
n
n
n
8
14.7
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
Torsion
9
3126.5
3116.1
1474.9
1061.3
381.9
C10.4 3022.2
K10.1
K1.6 1036.9
C34.6
3007.2
1445.4
1038.2
–
C15.0
–
3009.7
1446.5
1041.0
–
–
2997.5
1437.7
1036.1
–
CH
CH
3
3
3
deg str
deg def
rock
10 1464.8
11 1059.7
–
–
c
K1.3
–
1033.2
–
K2.9 CH
–
1
0
12
416.5
–
CCN bendC BF
3
deg def
1
0
n
n
13 1288.8
1469.1
467.7
K180.3 1293.3
1498.4
481.2
K205.1 1277.8
–
1494.5
481.1
K216.7 1284.8
–
1491.2
479.7
K206.4
C23.8
BF
BF
3
deg str
10
14
495.8
C28.1
504.5
C23.3
503.5
3
deg defC
CCN bend
1
0
n
15
16
286.0
70.1
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
BF
3
rock
10
n
BNC bend
a
Mode-numbering scheme is taken from Cho et al. [28].
Abbreviations used: sym, symmetric; deg, degenerate; str, stretch; def, deformation.
b
c
d
Tentative assignment.
Minor site.

128
R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
Table 5
K1
11
3 3
Calculated and experimental fundamental frequencies (cm ) of CD CN– BF complex
a
Mode
Calculated
Experimental
in Ar
Approximate
b
description
B3LYP/6-311CCG(d,p)
in N
2
in Xe
n
complex
n
monomer Dn
n
complex
nmonomer Dn
n
complex
n
monomer Dn
n
complex
nmonomer Dn
c
a
1
n
n
n
n
1
2
3
4
2189.9
2435.3
1130.9
874.5
2187.2
2362.3
1128.4
839.9
C2.7 2124.0
C73.0 2362.0
2121.9
2267.0
1104.4
828.9
C2.1 2129.0
C95.0 2365.3
2127.1
2266.4
1105.9
830.2
C1.9
–
2115.4
2269.9
1103.8
835.4
–
CD
3
sym str
C98.9 2356.1
C86.2 CN str
C2.5
–
–
–
–
–
–
–
–
3
CD sym def
11
CC strC BF
sym str
c
C34.6
875.6
C46.7
875.5
C45.3
3
1
1
n
n
5
6
169.8
802.2
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
BN str
c
11
869.0
K66.8
808.1
876.0
K67.9
879.9
880.6
BF
strCCC str
3
sym
11
n
7
578.3
682.0
K103.7
601.5
675.9
K74.4
K46.4
–
623.7
657.6
K33.9
599.7
675.4
K75.7
BF
3
sym def
d
c
d
d
6
29.5
–
616.0
K41.6
628.6
K46.8
a
e
2
n
n
n
n
n
8
10.6
2315.9
1051.3
865.7
–
–
–
2253.5
1040.0
845.5
–
–
–
–
–
–
–
2255.8
1041.4
850.9
–
–
–
–
–
–
–
–
–
–
–
–
2247.0
1034.7
845.0
–
–
–
–
–
–
Torsion
9
2307.8
1059.3
862.8
350.6
C8.1 2257.8
K8.0 1031.2
C4.3
K8.8
–
CD
CD
CD
3
3
3
deg str
deg def
rock
10
11
12
C2.9
–
–
397.7
C47.1
–
CCN
bendC BF
deg def
11
3
1
1
n
n
13
14
1242.4
489.8
1417.1
465.8
K174.7 1250.2
1447.2
479.7
K197.0 1233.2
1443.2
479.2
K210.0 1241.3
1440.1
477.8
K198.8
C19.8
BF
BF
3
deg str
deg
c
11
C24.0
498.0
C18.3
–
–
497.6
3
defCCCN
bend
1
1
n
n
15
16
274.6
67.1
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
BF
3
rock
11
BNC bend
a
Mode-numbering scheme is taken from Cho et al. [28]
Abbreviations used: sym, symmetric; deg, degenerate; str, stretch; def, deformation.
b
c
d
Tentative assignment.
Minor site.
Table 6
K1
10
3 3
Calculated and experimental fundamental frequencies (cm ) of CD CN– BF complex
a
Mode
Calculated
Experimental
in Ar
Approximate
b
description
B3LYP/6-311CCG(d,p)
in N
2
in Xe
n
complex
n
monomer Dn
n
complex
n
monomer Dn
n
complex
n
monomer Dn
n
complex
n
monomer Dn
c
a
1
n
n
n
n
1
2
3
4
2189.9
2435.3
1131.0
875.6
2187.2
2362.3
1128.4
839.9
C2.7 2124.1
C73.0 2361.9
2121.9
2267.0
1104.4
828.9
C2.2 2129.0
C94.9 2365.2
2127.1
2266.4
1105.9
830.2
C1.9
–
2115.4
2269.9
1103.8
835.4
–
CD
3
sym str
C98.8 2355.4
C85.5 CN str
–
–
C2.6
–
–
–
–
–
–
3
CD sym def
10
CC strC BF
3
sym str
c
C35.7
878.5
C49.6
877.3
C47.1
1
0
n
n
5
6
171.3
806.0
–
–
–
–
–
–
–
–
–
–
–
–
–
–
BN str
c
10
869.0
K63.0
814.9
876.0
K61.1
879.9
880.6
–
BF
CC str
3
sym strC
10
n
7
595.1
709.9
K114.8
621.4
703.1
K81.7
K59.0
–
639.1
683.6
K44.5
614.5
702.4
K87.9
BF
3
sym def
d
c
d
d
6
44.1
–
631.9
K51.7
643.1
K59.3
a
e
2
n
n
n
n
n
8
10.6
2315.9
1051.3
865.7
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
–
Torsion
9
2307.8
1059.3
862.8
350.6
C8.1 2257.8
K8.0 1031.2
2253.5
1040.0
845.5
–
C4.3
K8.8
–
2255.8
1041.4
850.9
–
2247.0
1034.7
845.0
–
CD
CD
CD
3
3
3
deg str
deg def
rock
10
11
12
C2.9
–
–
398.0
C47.4
–
CCN
bendC BF
deg def
10
3
1
0
n
n
13
14
1288.7
491.6
1469.1
467.7
K180.4 1291.5
1498.4
481.2
K206.9 1278.8
–
1494.5
481.1
K215.7 1282.7
–
1491.2
479.7
K208.5
–
BF
BF
3
deg str
10
C23.9
500.1
C18.9
–
3
deg defC
CCN bend
10
n
15
274.7
–
–
–
–
–
–
–
–
–
–
–
3
BF rock
a
Mode-numbering scheme is taken from Cho et al. [28].
Abbreviations used: sym, symmetric; deg, degenerate; str, stretch; def, deformation.
b
c
d
Tentative assignment.
Minor site.

R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
129
1
CH CN/ BF /Ar were observed at almost the same
0
listed in Tables 3–6 are, at least qualitatively, in good
agreement.
3
3
K1
frequencies of 3022.2/3021.0 and 3019.0 cm . The
bands at the highest frequencies among these absorptions
would be corresponding to a major matrix site. For
CD CN/BF /Ar, a very weak absorption was observed at
3.2.2. CN stretching (n2)
In the spectrum of CH CN/BF /Ar, the CN stretching
3
3
K1
3
3
2
degenerate stretching absorption of the CD CN monomer,
257.8 cm
in the higher frequency region of the CD3
(n ) absorption of the complex was observed at
2
K1
2365.6/2364.6 cm as a slightly split band. The additional
3
K1
which appeared at 2253.5/2251.5 cm as a site-split band.
The corresponding absorption was observed at the same
K1
broad absorptions observed at 2373.8 and 2371.8 cm
could not be assigned to the 1:1 complex because of their
dependence on R/M ratios. The corresponding absorption
1
0
frequency for CD CN/ BF /Ar. Therefore, the band at
3
3
K1
10
for CH CN/ BF /Ar was observed at essentially the same
2257.8 cm
erate stretching (n ) of the complex.
was tentatively assigned to the CD degen-
3
3
3
K1
frequency of 2365.7/2364.4 cm . We adopted the higher
frequency bands of the matrix-split absorptions for a major
9
In the spectrum of CH CN/BF /Ar, the CH sym-
3
3
3
1
0
metric stretching (n ) absorptions of the complex were
1
site. In the spectra of CD CN/BF /Ar and CD CN/ BF /Ar,
3 3 3 3
K1
observed at 2956.5 cm
as a shoulder and at
as a weak but distinct peak. The
corresponding absorptions were observed at 2956.0
the n2 absorptions of the complexes were observed at
K1
2363.6/2362.0 and 2363.7/2361.9 cm , respectively. In
K1
2
953.6 cm
these cases, we adopted the lower frequency bands for a
major site because of their stronger intensities in contrast to
the cases of CH CN.
K1
10
and 2953.4 cm
was observed at 2950.4 cm
for CH CN/ BF /Ar. This mode
3
K1
3
for the CH CN monomer
3
3
1
0
in Ar. The CD3 symmetric stretching (n ) absorption
1
In the spectra of both CH CN/BF /N and CH CN/ BF /
3 3 2 3 3
K1
of the complex was observed at 2124.0 cm
CD CN/BF /Ar, which is slightly higher in frequency
for
N , the n2 absorption of the complex was
2
K1
observed at 2367.0 cm . The corresponding frequencies
3
3
K1
than the CD CN monomer band at 2121.9 cm . The
10
for CD CN/BF /N and CD CN/ BF /N were 2365.3 and
3
3
3
2
3
3
2
K1
K1
2365.2 cm , respectively. The absorptions observed at
corresponding absorption appeared at 2124.1 cm
for
1
CD CN/ BF /Ar.
0
K1
2266.4, 2275.6 and 2264.0 cm
CD CN in N were assigned to the major site monomer, the
in the spectrum of free
3
3
10
In the spectra of CH CN/BF /N and CH CN/ BF /
3
3
3
2
3
3
2
N , no new absorptions that can be assigned to the n
2
minor site monomer and the dimer, respectively.
1
9
0
and n of the complex were observed partly because of the
1
For CH CN/BF /Xe and CH CN/ BF /Xe, the n
3 3 3 3 2
K1
poor isolation quality of matrices. Similarly, no new
absorptions were observed for both CD CN/BF /N and
absorption of the complex was observed at 2357.6 cm
In the spectrum of free CH CN in Xe, the absorptions of the
.
3
3
2
3
1
0
CD CN/ BF / N in the n region besides the slightly
K1
CH CN monomer at 2262.3 cm , those of the dimer or
3
3
2
9
3
K1
broadened band at 2255.8 cm of the CD CN monomer.
K1
polymer at 2258.5 and 2253.8 cm
were observed. The
3
However, a very weak absorption, which was not
observed for free CD CN, was observed as a shoulder
combination bands (n Cn ) of the monomer, dimer and
3 7
polymer, which are enhanced by Fermi resonance, were
K1
observed at 2299.9, 2298.3, 2293.0 cm , respectively. For
3
K1
at 2129.0 cm
spectrum. The corresponding absorption was observed at
in the n region of the CD CN/BF /N
2
1
3
3
CD CN/BF /Xe, the sharp absorption due to the n of the
3
3
2
1
0
the same frequency for CD CN/ BF /N . We tentatively
K1
complex was observed at 2356.1 cm . The corresponding
3
3
2
1
absorption for CD CN/ BF /Xe appeared at 2355.4 cm
0
K1
assigned this absorption to the n of the complex. Three
1
,
though its frequency is less reliable because of its low
3
3
absorptions were observed at 2127.1, 2124.2 and
K1
2
the spectrum of the CD CN monomer. We assigned the
120.9 cm
in the CD symmetric stretching region of
intensity. The CN stretching of the CD CN monomer was
3
K1
observed at 2269.9 cm in Xe.
3
3
K1
sharp band at the highest frequency of 2127.1 cm to the
The CN stretching frequencies predicted by the
B3LYP/6-311CCG(d,p) calculations for all isotopically
CD CN monomer.
3
10
K1
In the spectra of CH CN/BF /Xe and CH CN/ BF /
3
substituted species reveal blue shifts of 73.0 cm
on
3
3
3
Xe, no absorptions attributable to the complex were
observed in the n9 and n1 regions. Two absorptions
K1
observed at 2997.5 and 2939.4 cm were assigned to the
complexation. The experimental large blue shifts observed
in all matrices qualitatively agree with the predictions.
The frequency shifts in Xe are somewhat smaller than
CH degenerate and symmetric stretchings of the CH CN
3
those in Ar and N because of the higher frequencies of
2
3
monomer in Xe, respectively. No new absorptions
were observed in the CD3 stretching region of the
the acetonitrile monomers as well as the lower frequencies
of the complexes.
1
CD CN/BF /Xe and CD CN/ BF /Xe spectra. The
0
3
3
3
3
CD degenerate and symmetric stretching absorptions of
3
3.2.3. CH(D) degenerate deformation (n )
3
10
1
0
the CD CN monomer were observed at 2247.0 and
3
In the spectra of CH CN/BF /Ar and CH CN/ BF /Ar,
3 3 3 3
K1
115.4 cm , respectively.
2
no absorptions attributable to the complex were observed in
this region partly because of the overlap with the strong and
complicated absorptions of the BF degenerate stretchings
For the CH3 and CD3 stretching modes described
above, the observed and the calculated frequency shifts
3

130
R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
K1
of the BF polymers. The CH degenerate deformation of
3
above. The bands at 1278.8 and 1233.2 cm
correspond to a major site.
would
3
the CH CN monomer in Ar, which was not precisely
3
described in the literature [34], was probably observed at
1
Ar, the CD degenerate deformation (n ) absorptions of the
In the spectrum of CH
absorptions were observed at 1284.8 and 1239.0 cm
CN/BF /Xe, two significant
3 3
K1 10
445.4 cm . For both CD CN/BF /Ar and CD CN/ BF /
K1
.
and
3
3
3
3
1
CN– BF
0
These bands should be assigned to n13 of CH
11
3
10
K1
complexes were observed at 1031.2 cm . The calculated
3
3
CH CN– BF , respectively, though their intensity ratio was
slightly different from 1:4. The corresponding absorption
3 3
K1
red shifts on complexation, which are less than 10 cm
correspond to the experimental results.
In all co-deposited spectra of N and Xe matrices, no
,
K1
was observed at 1284.8 cm for CH
new absorptions were observed at 1282.9, 1241.3 and
10
CN/ BF /Xe. Three
3
3
2
K1
absorptions attributable to n10 of the complexes were
observed. The absorptions of the CH CN and CD CN
1235.2 cm
band was assigned to n13 of CD
problem. The lower two bands were interpreted as n13 of
for CD CN/BF /Xe. The highest frequency
3 3
1
0
CN– BF with no
3 3
3
3
K1
monomers were observed at 1446.5 and 1041.4 cm in N2,
1
1
respectively. The corresponding bands were observed at
1
CD CN– BF with site splitting. Although there is no clear
3 3
K1
437.7 and 1034.7 cm in Xe, respectively.
explanation for this specific site splitting, we adopted the
K1
slightly stronger absorption at 1241.3 cm for a major site.
K1
The corresponding absorption was observed at 1282.7 cm
3
.2.4. BF degenerate stretching (n )
3 13
10
for CD CN/ BF /Xe. The BF degenerate stretching
3
3
3
In the spectrum of CH CN/BF /Ar, as reported in the
3
10
absorptions of the BF and BF monomers in Xe were
11
3
3
3
K1
literature [23], several new absorptions appeared at
considerably lower frequencies from the BF degenerate
observed at 1491.2 and 1440.1 cm , respectively.
.2.5. CH(D) symmetric deformation (n )
3
stretching region of the free species. The two characteristic
features, which had the intensity ratio of 1:4 and similar
K1
shape, were observed at 1293.3 and 1248.7 cm . These
3
3
3
No distinctive peak attributable to the complex was
observed in this region for CH CN/BF /Ar. However, a
3
3
bands have been assigned to the BF degenerate stretchings
3
K1
weak absorption was observed at 1374.3 cm as the lower
frequency shoulder of the CH3 symmetric deformation
1
0
11
(
[
n ) of CH CN– BF and CH CN– BF , respectively
13 3 3 3 3
23]. The additional weaker absorptions were observed at
K1
307.9 and 1265.1 cm , which were tentatively assigned
K1
absorption of the CH CN monomer at 1375.7 cm . Since
3
1
to n13 of CH CN– BF and CH CN– BF in a minor site,
the calculated frequency for this mode reveals a small red
shift on complexation, we tentatively assigned this
absorption to the CH symmetric deformation (n ) of the
1
0
11
3
3
3
3
1
respectively. For CH CN/ BF /Ar, n of CH CN– BF in
0
10
3
3
13
3
3
3
3
minor and major sites was observed at 1307.9 and
K1
CH CN–BF complex. The corresponding shoulder was
3
3
1
0
1
BF /Ar, n of CD CN– BF and CD CN– BF were
293.3 cm , respectively. In the spectrum of CD CN/
3
observed at the same frequency for CH CN/ BF /Ar. In
3 3
1
0
11
1
0
3
13
3
3
3
3
the spectra of CD CN/BF /Ar and CD CN/ BF /Ar, no
3 3 3 3
K1
observed at 1291.4 and 1250.2 cm , respectively. The
absorptions attributable to a minor site could not be clearly
new absorptions attributable to the complexes were
observed around the CD symmetric deformation of the
3
1
observed. For CD CN/ BF /Ar, the only absorption at
0
K1
3
3
CD CN monomer at 1104.4 cm
.
In the spectra of CH CN/BF /N and CH CN/ BF /N ,
3
K1
1
0
1
291.5 cm was observed.
In the spectrum of CH CN/BF /N , several weak absorp-
tions were newly observed at considerably lower frequencies
3
3
2
3
3
2
3
3
2
no new distinctive peaks were observed around the CH CN
3
K1
monomer absorption at 1378.6 cm . However, a weak
K1
from the BF degenerate stretching region of the free species.
3
shoulder at 1377.4 cm
tentatively assigned this absorption to n of the complex. For
was found in both spectra. We
The significant features appeared at 1280.8, 1277.9, 1269.9,
10
3
K1
1
0
1
similar new absorptions were observed at 1280.9, 1277.8 and
235.0, 1227.6 and 1220.7 cm . For CH CN/ BF /N ,
3 3 2
CD CN/BF /N and CD CN– BF /N , no absorptions
3 3 2 3 3 2
attributable to the complex were observed around the
K1
K1
270.3 cm . Since the BF degenerate stretchings of the
1
free species reveal matrix-split features in N [11,37], we
CD CN monomer absorption at 1105.9 cm
3
.
3
2
In the spectrum of CH CN/BF /Xe, n of the complex was
3 3 3
K1
assigned the bands at 1280.9, 1277.8 and 1270.3 cm to n13
K1
observed at 1368.2 cm as well as the CH CN monomer
3
1
of CH CN– BF as well as the bands at 1235.0, 1227.6 and
0
K1
absorption at 1371.6 cm . The corresponding absorption
3
3
K1
220.7 cm to that of CH CN– BF . It is reasonable to
11
K1
10
1
was observed at 1368.3 cm
both CD CN/BF /Xe and CD CN/ BF /Xe, no new absorp-
for CH CN/ BF /Xe. For
3 3
3
3
K1
10
associate the bands at 1277.8 and 1235.0 cm to major site.
Several new absorptions were also observed in the spectrum
of CD CN/BF /N . The significant features were at 1278.7,
3
3
3
3
tions were observed around the CD symmetric deformation
3
K1
3
3
2
absorption of the CD CN monomer at 1103.8 cm
3
.
K1
1
For CD CN/ BF /N , new absorptions were observed at
271.8, 1266.3, 1236.1, 1233.2, 1227.7 and 1218.0 cm
1
.
0
3
3
2
3.2.6. CH(D) rocking (n )
3
11
K1
278.8, 1272.1 and 1266.3 cm . We assigned the bands at
10
In the spectra of CH CN/BF /Ar and CH CN/ BF /Ar,
3 3 3 3
1
1
K1
278.8, 1272.1 and 1266.3 cm to n13 of CD CN– BF as
10
3
3
K1
no distinctive peaks were observed around the CH rocking
3
K1
well as the bands at 1236.1, 1233.2, 1227.7 and 1218.0 cm
1
to that of CD CN– BF for the same reason mentioned
absorption of the CH CN monomer at 1038.2 cm
3
.
K1
1
However, the intensities of the shoulders at 1036.8 cm
3
3

R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
131
K1 10
for CH CN/BF /Ar and at 1036.9 cm for CH CN/ BF /
Therefore, we only tentatively assigned the absorptions
K1
3
3
3
3
10
to n4 of CD CN– BF and
3 3
Ar were obviously stronger than those of free CH CN. We
3
at 877.3 and 875.5 cm
1
1
tentatively assigned these weak shoulders to the CH3
rocking (n ) of the complexes based on the agreement
CD CN– BF , respectively. The CC stretching absorption
3 3
K1
of the CD CN monomer in N was observed at 830.2 cm
3 2
1
1
K1
for a major site and at 836.4 cm for a minor site.
with the calculated small red shift. No absorptions
attributable to the complexes were observed around the
1
For CH CN/BF /Xe and CH CN/ BF /Xe, no new
0
3
3
3
3
K1
CD rocking of the CD CN monomer at 845.5 cm in the
absorptions were observed in the n4 region. The CC
stretching absorptions of the CH CN monomer and the
3
3
1
spectra of CD CN/BF /Ar and CD CN/ BF /Ar.
0
3
3
3
3
3
K1
polymer were observed at 927.1 and 917.7 cm , respect-
ively. Two new absorptions were observed at 875.5 and
The n11 absorptions for all isotopically substituted
complexes could not be observed in N2 matrices. The
absorptions of the CH CN and CD CN monomers were
K1
872.0 cm in the spectrum of CD CN/BF /Xe. However,
3
3
3
3
K1
observed at 1041.0 and 850.9 cm , respectively.
these bands had similar intensities, i.e. their intensity ratio
was far from 1:4. Thus, we could not conclude whether the
above two absorptions should be assigned to the complexes.
No absorption was observed in this region of the spectrum
1
In the spectra of CH CN/BF /Xe and CH CN/ BF /Xe,
0
3
3
3
3
the absorptions assigned to n of the complexes were
1
1
K1
observed at 1033.2 cm . Two partly overlapping absorp-
K1
10
tions were observed at 1038.1 and 1036.1 cm
comparable intensities in the spectrum of free CH CN in Xe.
with
of CD CN/ BF /Xe because of its poor spectral quality.
3
3
The CC stretching absorption of the CD CN monomer in Xe
3
3
K1
We assigned the latter band to the CH rocking of the
3
was observed at 835.4 cm
.
CH CN monomer based on the results with different R/M
3
ratios. The former band was tentatively assigned to the
3.2.8. BF symmetric stretching (n )
3
6
1
dimer. For CD CN/BF /Xe and CD CN/ BF /Xe, no
0
3
3
3
3
In the spectrum of CH CN/BF /Ar, several new absorp-
3 3
absorptions attributable to the complexes were observed
around the CD rocking of the CD CN monomer at
tions were observed in this region, together with the bands
of the BF monomer and the polymers. The significant
3
3
3
K1
K1
bands were located at 856.7, 841.4 and 811.7 cm , which
8
45.0 cm
.
would correspond to the three features previously reported
by Wells et al. [23]. They tentatively assigned the highest
frequency band to the BF3 symmetric stretching (n )
3
.2.7. CC stretching (n4)
In the spectra of CH CN/BF /Ar and CH CN/ BF /Ar,
no new absorptions attributable to the CC stretchings (n ) of
1
0
3
3
3
3
6
1
0
activated by complexation. For CH CN/ BF /Ar, new
3 3
4
the complexes were observed. Although the calculated
frequency for this mode reveals a distinguishable blue shift
absorptions were observed at 876.0, 870.8 842.3, 827.7
K1
seems to be
K1
and 813.5 cm . The band at 870.8 cm
K1
K1
of about 30 cm on complexation, the extremely weak
infrared intensity prevents the observation of this mode. Two
absorptions attributable to the complex were observed at
corresponding to that at 856.7 cm in the CH CN/BF /Ar
3 3
spectrum in view of the similarity between their band
shapes. However, the pair of absorptions at 813.5 and
K1
78.6 and 875.6 cm in the spectrum of CD CN/BF / Ar.
K1
8
The lower frequency band was stronger though their intensity
811.7 cm
weak absorption was observed at 876.0 cm
would be the alternative candidate. A very
K1
3
3
in the
spectrum of free BF in Ar, which can be assigned to the
1
ratio was rather different from 1:4. For CD CN/ BF /Ar,
0
3
3
3
only the higher frequency absorption was observed at
K1
78.5 cm . According to the B3LYP calculations, the CC
BF symmetric stretching absorption of the BF monomer
3
3
8
stretching (n ) and the BF3 symmetric stretching (n6)
activated in a matrix environment. The calculated frequen-
cies for the BF symmetric stretchings reveal red shifts of
4
3
K1 10 11
larger than 50 cm and B/ B splittings of about 5 cm
K1
absorptions are expected in this region. The predicted n6
bands reveal considerable red shifts on complexation,
whereas the observed frequencies are higher than that of
on complexation. Therefore, we tentatively adopted the
K1
absorptions at 813.5 and 811.7 cm as the first candidates
1
0
11
the BF monomer described in the next section. Therefore,
3
for n of CH CN– BF and CH CN– BF , respectively. In
6 3 3 3 3
K1
we assigned the absorptions at 878.5 and 875.6 cm to n of
the spectrum of CD CN/BF /Ar, a new absorption was
3 3
4
1
0
11
CD CN– BF and CD CN– BF , respectively.
K1
observed at 808.1 cm , together with several bands due
to free BF and CD CN. The corresponding absorption
3
3
3
3
No absorptions that can be assigned to n4 of the
complexes were observed in the spectra of CH CN/BF /
3
3
K1
10
was observed at 814.9 cm
Although the intensity of the band in CD CN/BF /Ar was
for CD CN/ BF /Ar.
3 3
3
3
1
N and CH CN/ BF /N . In the spectrum of CD CN/BF /
0
2
3
3
2
3
3
3
3
N , new absorptions were observed at 877.2 and
2
rather weak, we tentatively assigned the bands at 814.9 and
K1
75.5 cm . Their intensities are, however, rather weak
K1
10
11
8
808.1 cm
respectively.
Two new absorptions were observed at 843.5
to n of CD CN– BF and CD CN– BF ,
6 3 3 3 3
compared to the corresponding bands in Ar. Although the
exact comparison of the band intensities was difficult
because of their weak intensities, the higher frequency band
was a little stronger. However, only the absorption
corresponding to the above stronger band was observed at
K1
and 835.8 cm
in the spectrum of CH CN/BF /N . For
3 3 2
1
0
CH CN/ BF /N , only the band at 843.5 cm
K1
was
observed. The matrix-activated BF symmetric stretching
3
3
2
3
K1
10
K1
absorption [8] was observed at 879.9 cm in the spectrum
8
77.3 cm
in the spectrum of CD CN/ BF /N .
3
3
2

132
R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
of free BF . Thus, we assigned the absorptions at 843.5 and
N , respectively. The other two bands at 633.0 and
2
K1
617.1 cm were assigned to the corresponding species in
3
K1
10
11
to n of CH CN– BF and CH CN– BF ,
8
35.8 cm
6
3
3
3
3
respectively, though the observed red shifts were smaller
than the predicted values. No absorptions attributable to the
complexes were observed in the spectra of CD CN/BF /N
2
a minor site. The intensities of these bands of the complexes
in N are rather weak compared to those in Ar. Furthermore,
2
the magnitudes of the frequency shifts on complexation for
major and minor sites are altered. In the spectrum of
CD CN/BF /N , several absorptions were observed at
3
3
1
0
and CD CN/ BF /N .
3
3
2
In the spectrum of CH CN/BF /Xe, several new absorp-
3
3
3
3
2
K1
K1
tions were observed at 873.3, 858.2, 838.4 and 809.0 cm
1
.
For CH CN/ BF /Xe, the observed absorptions were
639.0, 632.0, 623.7 and 616.0 cm with a spectral pattern
similar to CH CN/BF /N . The only two corresponding
0
3
3
3
3
2
K1
located at 873.1, 827.2 and 810.8 cm . Two pairs of
K1
absorptions were observed at 639.1 and 631.9 cm
10
for
CD CN/ BF /N . Thus, the absorptions at 639.1 and
K1 K1
absorptions, 873.1/858.2 cm and 810.8/809.0 cm , are
3
3
2
K1
10
considered to be candidates for n of the complexes. We
6
623.7 cm
were assigned to n7 of CD CN– BF and
3 3
1
1
tentatively adopted the latter pair according to the same
reason explained for the results in Ar. A very weak
K1
absorption observed at 880.6 cm in the spectrum of free
CD CN– BF , respectively. The other two bands at 631.9
3 3
K1
and 616.0 cm were assigned to the corresponding species
in a minor site. The BF symmetric deformations of the
3
1
0
11
BF and BF monomers were observed at 683.6 and
3 3
BF3 in Xe was assigned to the matrix-activated BF3
symmetric stretching of the BF monomer. In the spectra
K1
K1
657.6 cm , respectively, which are about 20 cm lower
than those in Ar.
In the spectrum of CH CN/BF /Xe, new absorptions were
3
1
of CD CN/BF /Xe and CD CN/ BF /Xe, no new absorp-
0
3
3
3
3
tions attributable to the complexes were observed.
3
3
observed at considerably lower frequencies from the BF3
symmetric deformation region of free BF . The significant
features appeared at 645.7, 631.1, 616.9 and 601.7 cm
3
.2.9. BF symmetric deformation (n )
7
3
3
K1
Several new absorptions were observed at considerably
lower frequencies from the BF symmetric deformation
.
The intensity ratio between the bands at 645.7 and
K1
631.1 cm as well as the ratio between the bands at 616.9
K1
and 601.7 cm were about 1:4. The only two absorptions
3
region of free BF in the spectrum of CH CN/BF /Ar. The
3
3
3
significant features appeared at 646.4, 631.8, 617.1 and
6
K1
01.2 cm . The intensity ratio between the former two
K1
10
were observed at 645.6 and 616.9 cm for CH
Xe. Thus, we assigned the absorptions at 616.9 and
CN/ BF /
3 3
bands, as well as that between the latter two, were about 1:4.
The corresponding absorptions were observed at 646.3
K1
10
11
601.7 cm to n of CH CN– BF and CH CN– BF in
7 3 3 3 3
K1
10
and 618.0 cm
reported, the absorptions at 618.0 and 601.2 cm are the
for CH CN/ BF /Ar. As previously
K1
Xe, respectively. The other two absorptions at 645.6 and
K1
631.1 cm were assigned to the corresponding species in
3
3
1
BF symmetric deformations (n ) of CH CN– BF and
0
a minor site. Relative intensities of the minor site absorptions
in Xe were much weaker than those in Ar. The BF
3
7
3
3
1
CH CN– BF , respectively. The other two absorptions at
1
3
3
3
K1
10
symmetric deformations of the BF
11
and BF
K1
646.3 and 631.8 cm were assigned to the corresponding
species in a minor site. Somewhat large site splittings of
3
3
monomers
in Xe were observed at 702.4 and 675.4 cm , respectively.
K1
about 30 cm
suggest that this vibrational mode is
The associated weak absorptions observed at 697.4 and
K1
sensitive to a microscopic environment around the complex.
In the spectrum of CD CN/BF /Ar, the absorptions at 629.5
670.2 cm
were assigned to BF dimers. A lot of
3
new absorptions were observed in this region of the
CD CN/BF /Xe spectrum. We assigned the absorptions
observed at 614.5 and 599.7 cm to n CN– BF
3 3
3
3
K1
and 601.5 cm
absorptions of the BF3 polymers. The corresponding
were distinguished from a number of
3
3
K1
10
of CD
and CD CN– BF , respectively. The corresponding bands
3 3
7
K1
11
absorptions were observed at 644.1 and 621.4 cm for
K1
CD CN/ BF / Ar. The bands at 621.4 and 601.5 cm
1
0
K1
for a minor site were observed at 643.1 and 628.6 cm
.
3
3
1
0
11
were assigned to n of CD CN– BF and CD CN– BF ,
7
3
3
3
3
K1
respectively. The other two bands at 644.1 and 629.5 cm
3.2.10. BF degenerate deformation (n )
3 14
were assigned to the corresponding species in a minor site.
In the spectrum of CH CN/BF /N , several new absorp-
In the spectrum of CH CN/BF /Ar, a weak new
3 3
K1
absorption was observed at 502.9 cm , which can be
clearly distinguished from the complicated absorptions of
3
3
2
tions were observed at somewhat lower frequencies from
the BF3 symmetric deformation region of free BF3.
The significant features appeared at 640.5, 632.8, 625.3
K1
the BF3 polymers in a region of 510–520 cm . The
K1
corresponding absorption was observed at 504.5 cm for
K1
10
CH CN/ BF /Ar. The calculated frequencies of the BF
3
and 617.1 cm . The intensity ratio between the bands at
K1
3
3
6
between the bands at 640.5 and 625.3 cm
32.8 and 617.1 cm
was about 1:4. However, the ratio
K1
degenerate deformations reveal medium blue shifts on
complexation. Thus, we assigned the absorptions at 504.5
was slightly
K1
and 502.9 cm to the BF degenerate deformations (n ) of
different from 1:4 probably because of the overlapping with
other absorptions. The only two corresponding absorptions
3
14
1
CH CN– BF and CH CN– BF in Ar, respectively.
0
11
3
3
3
3
K1 10
were observed at 640.6 and 633.0 cm for CH CN/ BF /
K1
Similar new absorptions were observed at 498.0 cm
K1
3
3
10
N . Therefore, we assigned the absorptions at 640.6 and
2
for CD CN/BF /Ar and at 500.1 cm for CD CN/ BF /
3 3 3 3
11
K1
10
11
25.3 cm to n of CH CN– BF and CH CN– BF in
6
Ar, which were assigned to n14 of CD CN– BF
3 3
7
3
3
3
3

R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
133
1
and CD CN– BF , respectively. The BF degenerate
0
were also recognized. As can be seen in Figs. 2–4, the
absorptions of the complexes in N are weaker than those in
3
3
3
1
deformations of the BF3 and BF monomers in Ar
0
11
3
K1
2
were observed at 481.2 and 479.7 cm , respectively.
Ar and Xe. Because of the stronger interaction of the lone-
pair electron in N molecule with the boron atom in free
No absorptions attributable to the complexes were
observed in this region of the spectra for all isotopically
substituted species in N . The BF degenerate deformations
2
BF , it is expected that N and BF form a weak van der
3
2
3
2
3
Waals complex [14] during the co-deposition of N2
matrices. Although the interaction of CH CN with BF is
1
0
11
of the BF and BF monomers in N were observed as
3
3
2
3
3
K1
matrix-split bands at 481.1/479.7 and 479.2/477.8 cm
respectively.
In the spectrum of CH CN/BF /Xe, a new absorption
,
stronger than that of N , a great number of N molecules
2 2
would prevent the formation of the CH CN–BF complex to
3
3
3
K1
3
a certain extent. As a result, the percentage of BF that
3
was observed at 502.5 cm . The corresponding absorption
K1 10
was observed at 503.5 cm for CH CN/ BF /Xe, though
forms the complex with CH CN, therefore the infrared
3
3
3
intensities of the complex, would have decreased in N2
matrices.
its intensity was quite weak. Thus, the absorptions at 503.5
K1
and 502.5 cm were assigned to n14 of CH CN– BF and
10
3
3
10
The Dn of the selected vibrations of the complexes in Ar,
N and Xe matrices are compared in Table 7. The Dn of
1
1
CH CN– BF , respectively. The absorptions of the BF3
3
3
2
1
and BF monomers in Xe were observed at 479.7 and
1
3
K1
the BF degenerate stretchings and symmetric deformations
3
4
77.8 cm , respectively. For CD CN/BF Xe, a less
3 3
K1
reveal comparable magnitudes in Ar and Xe matrices.
However, the Dn of the CN stretchings are somewhat
reliable broad absorption was observed at 497.6 cm
1
,
which was tentatively assigned to n14 of CD CN– BF in
1
3
3
smaller in Xe. The CN stretching frequency of the CH CN
3
Xe.
monomer is slightly different from that in Ar or N2.
This suggests that a particular vibrational mode is more
affected by a matrix environment than others.
3
.3. Matrix effects on vibrational spectra
The structures of the 1:1 complexes of acetonitrile and
boron trifluoride trapped in Ar, N and Xe matrices are
The magnitudes of the observed Dn for most of the
vibrational modes that reveal remarkable shifts are larger
than the calculated values at the B3LYP/6-311CCG(d,p)
level. This seems to indicate that the interaction between
acetonitrile and boron trifluoride in low temperature matrices
is stronger than that predicted by calculation. However, the
2
thought to be essentially the same as the optimized
geometry obtained at the B3LYP/6-311CCG(d,p) level
by considering the observed and the calculated vibrational
frequencies, especially the frequency shifts on complexa-
tion Dn, described in the above sections. However, some
matrix effects on the vibrational spectra of the complexes
BF symmetric deformation mode is an exception. The
3
observed magnitudes of Dn for this mode are obviously
smaller than the calculated values. As one reason for this,
Table 7
K1
Comparison of the frequency shift Dn (cm ) of the acetonitrile-boron trifluoride complexes in different matrices
Species
Mode
Calculated
Experimental
in Ar
Approximate
a
description
B3LYP/6-311CCG(d,p)
in N
2
in Xe
1
1
CH
CH
CD
CD
3
3
3
3
CN– BF
3
3
3
3
n
n
2
C73.0
K103.1
C107.3
K74.7
K44.1
K198.5
C109.8
K32.3
K40.5
K208.2
C95.3
K73.7
K44.3
K201.1
CN str
11
7
BF sym def
3
Minor site
11
BF
3
n
13
K174.7
deg str
10
CN– BF
n
n
2
C73.0
K114.3
C107.4
K85.1
K56.8
K205.1
C109.8
K43.0
K50.6
K216.7
C95.3
K85.5
K56.8
K206.4
CN str
10
7
BF
3
sym def
Minor site
10
BF
3
n
13
K180.3
deg str
11
CN– BF
n
n
2
C73.0
K103.7
C95.0
K74.4
K46.4
K197.0
C98.9
K33.9
K41.6
K210.0
C86.2
K75.7
K46.8
K198.8
CN str
11
7
BF
3
sym def
Minor site
11
BF
3
n
13
K174.7
deg str
10
CN– BF
n
n
2
C73.0
K114.8
C94.9
K81.7
K59.0
K206.9
C98.8
K44.5
K51.7
K215.7
C85.5
K87.9
K59.3
K208.5
CN str
10
7
BF
3
sym def
Minor site
10
n
13
K180.4
3
BF deg str
a
Abbreviations used: sym, symmetric; deg, degenerate; str, stretch; def, deformation.

134
R. Hattori et al. / Journal of Molecular Structure 750 (2005) 123–134
coordination of the matrix atom or molecule to the BF3
moiety of the complex from the opposite side of the CH CN
[7] L.M. Nxumalo, M. Andrzejak, T.A. Ford, Vib. Spectrosc. 12 (1996)
21.
2
3
[
[
8] L.M. Nxumalo, T.A. Ford, Spectrochim. Acta Part A 53 (1997) 2511.
9] L.M. Nxumalo, T.A. Ford, J. Mol. Struct. 436-437 (1997) 69.
moiety seems to be important. This weak interaction with a
matrix environment would reduce the red shift of the BF3
symmetric deformation of the complex. Particularly small
[
[
10] L.M. Nxumalo, T.A. Ford, S. Afr, J. Chem. 48 (1995) 30.
11] L.M. Nxumalo, T.A. Ford, J. Mol. Struct. 656 (2003) 303.
magnitudes of Dn in N seem to support this explanation.
2
[12] S. Fau, G. Frenking, Mol. Phys. 96 (1999) 519.
[
[
[
13] L.M. Nxumalo, M. Andrzejak, T.A. Ford, J. Chem. Inf. Comput. Sci.
6 (1996) 377.
14] L.M. Nxumalo, M. Andrzejak, T.A. Ford, J. Mol. Struct. 509 (1999)
87.
15] T.A. Ford, D. Steele, J. Phys. Chem. 100 (1996) 19336.
The frequency differences between the BF symmetric
3
3
deformations of the major and minor site species are
remarkably large in Ar and Xe matrices. A large site
splitting suggests that even a low dielectric matrix can affect
the nature of the vibrations or bondings of the complex.
Furthermore, this matrix effect is mode specific for the
vibrational spectra. A similar consideration of the theoreti-
cal study on the B–N bond length of the complex was
reported in the literature [29].
2
[16] A.W. Laubengayer, D.S. Sears, J. Am. Chem. Soc. 67 (1945) 164.
[17] J.L. Hoard, T.B. Owen, A. Buzzell, O.N. Salmon, Acta Crystallogr. 3
(
1950) 130.
[
[
[
[
18] K.F. Purcell, R.S. Drago, J. Am. Chem. Soc. 88 (1966) 919.
19] B. Swanson, D.F. Shriver, J.A. Ibers, Inorg. Chem. 8 (1969) 2182.
20] B. Swanson, D.F. Shriver, Inorg. Chem. 9 (1970) 1406.
21] M.A. Dvorak, R.S. Ford, R.D. Suenram, F.J. Lovas, K.R. Leopold,
J. Am. Chem. Soc. 114 (1992) 108.
4
. Conclusions
[22] R. Beattie, P.J. Jones, Angew. Chem. Int. Ed. Engl. 35 (1996) 1527.
[
[
[
23] N.P. Wells, J.A. Phillips, J. Phys. Chem. A 106 (2002) 1518.
24] R. Jurgens, J. Alml o¨ f, Chem. Phys. Lett. 176 (1991) 263.
25] M.A. Ablaeva, G.M. Zsidomirov, A.G. Pelmenshchikov, E.B. Burgina,
V.P. Baltakhinov, React. Kinet. Catal. Lett. 48 (1992) 569.
The FTIR spectra of CH CN–BF3 including its iso-
3
topically substituted species were observed in Ar, N and Xe
2
matrices, and matrix effects on the vibrational spectra of the
complexes were investigated. Several previously unreported
new absorptions were observed in Ar. The vibrational
[
26] V. Jonas, G. Frenking, M.T. Reetz, J. Am. Chem. Soc. 116 (1994) 8741.
[27] H. Jiao, P. von R, Schleyer, J. Am. Chem. Soc. 116 (1996) 7429.
[28] H.-G. Cho, B.-S. Cheong, J. Mol. Struct. (Theochem) 496 (2000) 185.
[
[
[
29] D.J. Giesen, J.A. Phillips, J. Phys. Chem. A 107 (2003) 4009.
30] H.S. Booth, K.S. Wilson, Inorg. Syn. 1 (1939) 21.
spectra in N and Xe were recorded for the first time. The
2
observed frequency shifts on complexation, Dn, were
qualitatively in good agreement with the results calculated
at the C3v eclipsed optimized geometry at the B3LYP/6-
31] M.J. Frisch, G.W. Trucks, H.B. Schlegel, G.E. Scuseria, M.A. Robb,
J.R. Cheeseman, J.A. Montgomery, Jr., T. Vreven, K.N. Kudin, J.C.
Burant, J.M. Millam, S.S. Iyengar, J. Tomasi, V. Barone, B.
Mennucci, M. Cossi, G. Scalmani, N. Rega, G.A. Petersson, H.
Nakatsuji, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M.
Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, M. Klene, X. Li,
J.E. Knox, H.P. Hratchian, J.B. Cross, C. Adamo, J. Jaramillo, R.
Gomperts, R.E. Stratmann, O. Yazyev, A.J. Austin, R. Cammi, C.
Pomelli, J.W. Ochterski, P.Y. Ayala, K. Morokuma, G.A. Voth, P.
Salvador, J.J. Dannenberg, V.G. Zakrzewski, S. Dapprich, A.D.
Daniels, M.C. Strain, O. Farkas, D.K. Malick, A.D. Rabuck, K.
Raghavachari, J.B. Foresman, J.V. Ortiz, Q. Cui, A.G. Baboul, S.
Clifford, J. Cioslowski, B.B. Stefanov, G. Liu, A. Liashenko, P.
Piskorz, I. Komaromi, R.L. Martin, D.J. Fox, T. Keith, M.A. Al-
Laham, C.Y. Peng, A. Nanayakkara, M. Challacombe, P.M.W. Gill,
B. Johnson, W. Chen, M.W. Wong, C. Gonzalez and J.A. Pople,
GAUSSIAN 03, Revision B.05, Gaussian, Inc., Pittsburgh, PA, 2003.
3
11CCG(d,p) level. For most of the vibrational modes that
reveal remarkable frequency shifts, the observed magni-
tudes of Dn were larger than the calculated values.
Therefore, the interaction that is responsible for the complex
formation in low temperature matrices is considered to be
stronger than that predicted by calculation. However, the
observed frequency shits for the BF symmetric defor-
3
mations were smaller than the calculated values, especially
in N . This suggests that even an inert matrix like rare gas or
2
N has a significant effect on a particular vibrational mode.
2
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