Infrared spectra and theoretical calculations of HCl complexed with NO

Article abstract of DOI:10.1016/S0301-0104(98)00283-3

The vibrational spectra of NO:HCl trapped in argon matrix have been reinvestigated. In the high frequency region, two stretching modes of N-O and H-Cl have been observed in agreement with a recent paper [Chem. Phys. 185 (1994) 365]. In the low frequency region, two bands (N-H stretch and out of plane bend) have been identified. From a theoretical study, it has been shown that the four experimental frequencies of the complex are well reproduced only for a bent structure in which H-bonding takes place between the nitrogen atom of NO and the hydrogen atom of HCl. The calculated frequency shifts of the N-O and H-Cl stretching modes upon complexation agree well with the experimental values.

Full text of DOI:10.1016/S0301-0104(98)00283-3

Chemical Physics 237 Ž1998. 265–271
Infrared spectra and theoretical calculations of HCl complexed
with NO
L. Krim, M.E. Alikhani
Laboratoire de Spectrochimie Mol e´ culaire (UMR CNRS 7614), UniÕersit e´ P. et M. Curie, Bo iˆt e 49, b aˆ timent F74, 4 Place Jussieu, Paris
Cedex 05, France
Received 3 March 1998; revised 13 July 1998
Abstract
The vibrational spectra of NO:HCl trapped in argon matrix have been reinvestigated. In the high frequency region, two
stretching modes of N-O and H-Cl have been observed in agreement with a recent paper wChem. Phys. 185 Ž1994. 365x. In
the low frequency region, two bands ŽN-H stretch and out of plane bend. have been identified. From a theoretical study, it
has been shown that the four experimental frequencies of the complex are well reproduced only for a bent structure in which
H-bonding takes place between the nitrogen atom of NO and the hydrogen atom of HCl. The calculated frequency shifts of
the N-O and H-Cl stretching modes upon complexation agree well with the experimental values. q 1998 Elsevier Science
B.V. All rights reserved.
1
. Introduction
sponds to a transition state structure. The calculated
frequency shifts of both donor and acceptor Žwith
CASSCF method. are not in satisfactory agreement
Recently, Saxce et al. w1x reported a combined
experimental and theoretical investigation of hydro-
gen chloride and hydrogen bromide complexed with
nitric oxide monomer. They experimentally identi-
fied two bands corresponding to H-X and N-O
stretching modes of the NO:HX complexes ŽXsCl
or Br. isolated in argon matrix. They showed that,
upon complexation the H-Cl stretching mode is red
shifted, while the N-O one is blue shifted. In the
theoretical calculations, performed at the UHF-SCF
Žunrestricted Hartree-Fock self consistent field.,
UMP2 Žsecond order Møller-Plesset perturbation
method., and CASSCF Žmulticonfiguartion method.
levels of theory, they studied three different geome-
tries, one linear with H-bonding between N and H
ŽON...HCl. and two bents with H-bonding between
O and H ŽNO...HCl.. A vibrational analysis Žwith
UMP2. indicated that the linear geometry corre-
with the experimental data.
In order to complete the analysis of vibrational
frequencies of the NO:HCl complex particularly in
the low frequency region, an experimental investiga-
tion in solid argon was performed. The structural and
vibrational study of the complex has also been car-
ried out using the density functional theory approach
ŽDFT..
2
. Experimental techniques
1
4
NO gas was provided by ‘‘L’Air Liquide’’ with
1
5
a stated chemical purity of 99.9%, NO gas by
‘‘Isotec’’ with an isotopical purity of 97.8%, HCl
gas by Matheson Ž99.9%.. DCl gas was prepared in
the laboratory by addition of D O onto solid PCl .
2
5
0
301-0104r98r$ - see front matter q 1998 Elsevier Science B.V. All rights reserved.
PII: S0301-0104Ž98.00283-3

2
66
L. Krim, M.E. AlikhanirChemical Physics 237 (1998) 265–271
Argon gas, was also furnished by ‘‘L’Air Liquide’’
with a purity of 99.9995%.
in Table 1. Spectra of NO and ŽNO. w2–4x, HCl and
2
ŽHCl. w5–10x isolated in argon matrix are well
2
The NO Žor HCl. gas was first trapped in a liquid
known, and therefore their IR bands can easily be
nitrogen, then a small amount was allowed to evapo-
rate and the partial pressure so obtained was mixed
with argon gas in order to obtain the desired concen-
tration ratios NOrAr, HClrAr and NO: HCl rAr. In
the present work different values of these ratios were
used :
identified ŽTable 1.. Some vibrational frequencies of
NO:HCl and ŽNO. :HCl have been measured from
2
spectra of the mixture of NO and HCl in argon
matrix .
In our spectra, two regions can be distinguished
as following : low frequency region and high fre-
quency region.
Pure NOrAr and pure HClrAr: 1r3000, 1r1000,
1
r400, 1r300, 1r100 ;
3.1. Low frequency region (20–500 cmy 1
)
Mixture NO:HClrAr: 1:1r3000, 1:1r300, 1:1r
00, 1r2r400, 2r1r400, 5r1r1000, 1r5r1000.
Typically, 35 mMole of the gaseous mixture were
1
Two bands with frequencies lower than 100 cmy1
deposited onto a window cooled down to 20 K.
Deposition took around 90 min. In order to check the
pressure effect, spectra were recorded every de-
posited 5 mMole.
have been detected. The lowest one located at 32.4
y1
cm
is as a strong signal ŽFig. 1.. This frequency
can not be assigned to a mode of an NO:HCl com-
plex, because it depends on neither NO nor HCl gas
concentrations. On the other hand, it has the same
behaviour that two other observed bands assigned to
Spectra were recorded using a FTIR Bruker spec-
y1
trometer ŽIFS 120HR. at resolutions of 0.5 cm in
y1
y1
y1
the 20–500 cm
range and 0.1 cm
in the 500–
the water molecule located at 1590 cm and 3727
y1
y1
y1
6
000 cm
range. An Hg lamp was used for the
cm
regions. Therefore, the band at 32.4 cm
y1
domain located below 100 cm
and Globar lamp
may be attributed to water molecule w11,12x. The
y1
above 100 cm
.
A bolometer detector was used for the low fre-
y1
Table 1
quency region, typically from 20 to 500 cm and a
y1
Žrelative intensities a in
y1
All the observed frequencies in cm
parentheses. in argon matrix, for NO and HCl
MCT detector from 500 to 6000 cm . No signal
1
4
y1
was observed beyond 3750 cm
conditions.
under the present
Frequency
Žrelative intensity.
Species
Mode
Three kinds of spectra were recorded at a series of
different temperatures and pressures:
3
7
1
1
2.4 Ž0.13.
2.8 Ž0.23.
46.5 Ž0.09.
H O
Rotation
Translation
2
HCl
Ø spectra recorded for pure NO in argon matrix
NOrAr.
NO:HCl
NO:HCl
ŽHCl.2
ŽNO.2
ŽNO.2
79.6 0.08
Ž
.
Ø spectra recorded for pure HCl in argon matrix
HClrAr.
231 Ž0.1.
Bending
Bending
N-O asymm. stretch
N-O asymm. stretch
N-O symm. stretch
N-O symm. stretch
2
1
1
1
1
43.5 Ž0.08.
776.5 Ž0.73.
802.8 Ž0.01.
Ø spectra recorded for mixtures of NO and HCl in
argon matrix NO:HCl rAr.
ŽNO. :HCl
2
863.5, 1865.5 Ž0.28. ŽNO.2
All spectra presented in this paper were recorded at
the temperature of deposition, 20 K. But in order to
study the temperature effect on complex formation,
some annealing of the matrix at several temperatures
up to 35 K were performed.
Ž
.
Ž
NO 2:HCl
.
867.4 0.11
1872.2, 1874.5 Ž0.30. NO in two sites
1
2
2
2
2
2
2
2
880.3 Ž0.10.
816.1 Ž0.02.
818.0 Ž0.013.
827.5 Ž0.49.
854.5 Ž0.19.
863.6
870.7 Ž0.05.
888.1 Ž1.
NO:HCl
N-O stretch
H-Cl stretch
H-Cl stretch
H-Cl stretch
PŽ1. line
H-Cl stretch
Q branch
RŽ0. line
ŽNO. :HCl
2
ŽHCl.2
NO:HCl
HCl
N :HCl
2
HCl
HCl
3
. Experimental results
The frequencies of all the absorptions measured
with NO:HCl, pure NO, and pure HCl are listed
a
The relative IR intensity are calculated with respect to the RŽ0.
1
4
14
band intensity of HCl.

L. Krim, M.E. AlikhanirChemical Physics 237 (1998) 265–271
267
y1
Fig. 1. NO and HCl trapped in argon matrix at 20 K. 0–100 cm
Fig. 2. NO and HCl trapped in argon matrix at 20 K. 100–300
1
4
y1
14
region Ža. NO in Ar, 1r200, Žb. HCl in Ar, 1r400, Žc.
cm
region Ža. NO in Ar, 1r200, Žb. HCl in Ar, 1r400, Žc.
1
4
14
NO:HClrAr , 2:1r400.
NO:HClrAr, 2:1r400.
bands were located at 96.0 and 125.0 cmy1 which
correspond to two modes of the NO:DCl complex.
presence of this band probably does not allow the
lowest fundamental mode of NO:HCl to be observed.
y1
.2. High frequency region (1700–3000 cmy 1
3
3
)
The second band located at 72.8 cm
is relatively
y1
wide Žfwhm s 5.4 cm ., and its intensity depends
.2.1. NO region (1700–2000 cmy 1)
only on the HCl concentration ŽFig. 1.. It can easily
1
4
be attributed to the translation of HCl monomer in
As it is shown in Fig. 4, NO molecule perturbed
argon matrix w13x. It could also hide a fundamental
by HCl presents a strong band located at 1880.3
mode of NO:HCl complex.
y1
In the 100–200 cm
region, two bands with
y1
same intensity, separated by 30 cm , were ob-
served. The first one located at 146.5 cm is rela-
y1
y1
tively wide Žfwhm s 17 cm ., and its intensity
depends on both NO and HCl concentrations ŽFig.
2
.. It is also sensitive to a change in the isotopic
composition of HClrDCl ŽFig. 3.. Its infrared inten-
sity remains constant after a warming of the matrix.
It can then be attributed to a mode of the NO:HCl
complex. The second band was observed at 179.6
y1
cm , with a width as large as that of the first one
y1
Žfwhms 16 cm .. Its dependence on both NO and
HCl concentrations and also on the isotopic composi-
tion of HCl indicates that it should be attributed to
another fundamental mode of the NO:HCl complex.
Spectra obtained with the NO:HCl:DClrArrr
2
cm
:1:1r400 mixture exhibit four bands in 100-200
Fig. 3. NO, HCl and DCl trapped in argon matrix at 20 K. Far
infrared region Ža. NO:HClrAr, 2:1r400, Žb. NO:HCl:DClr
Ar, 2:1:1r400.
y1
region ŽFig. 3.. In addition of the two bands
14
14
y1
located at 146.5 and 179.6 cm , the two other

2
68
L. Krim, M.E. AlikhanirChemical Physics 237 (1998) 265–271
Fig. 4. NO and HCl trapped in argon matrix at 20 K. NO region
Fig. 6. NO and HCl trapped in argon matrix at 20 K. HCl region
Ža. NO in Ar, 1r200, Žb. HCl in Ar, 1r400, Žc. NO:HClrAr,
2:1r400.
1
4
14
Ža. HCl in Ar, 1r400, Žb. NO in Ar, 1r200, Žc. NO:HClrAr,
2
:1r400.
cmy1. Its infrared intensity remains constant after
matrix warming. In agreement with Ref. w1x, this
band can be attributed to the N-O stretching mode of
The n and n modes of ŽNO. perturbed by HCl
are also observed at 1867.4 and 1802.3 cm , re-
1
5
2
y1
spectively w1x. The isotopic effects of the n1 mode
1
4
NO:HCl. The bands located at 1847.1 and 1882.8
y1
are observed at 1871.0, 1854.0, and 1834.5 cm
,
y1
15
cm
ŽFig. 5. correspond to
NO:DCl, respectively.
NO:HCl, and
14
14
15
15
for Ž NO. :DCl, Ž NO- NO.:HCl, and Ž NO. :
1
4
2
2
HCl, respectively.
Fig. 5. NO, HCl and DCl trapped in argon matrix at 20 K. NO
1
4
14
region Ža.
:1:1r400.
NO:HClrAr, 2:1r400, Žb.
NO:HCl:DClrAr,
Fig. 7. NO, HCl and DCl trapped in argon matrix at 20 K. DCl
region NO:HCl:DClrAr, 2:1:1r400.
2

L. Krim, M.E. AlikhanirChemical Physics 237 (1998) 265–271
269
.2.2. HCl region (2000–3000 cmy 1
Two bands which depend on both NO and HCl
concentrations as well as on the HCl isotopic substi-
)
3
Table 3
Geometrical and vibrational properties of NO:HCl using B3LYP
Parameters
Linear ClH...NO
Bent ClH...NO
tution are observed in this region ŽFig. 6.. For the
strongest one located at 2827.5 cm , there is no
rHCl
rNO
rHN
Ž ˚.
A
1.2824
1.1452
2.4802
0.0
1.2874
1.1444
2.2963
177.5
124.8
y590.775429
1.2
1.73
2826 Ž298.
1966 Ž57.
y1
1
4
15
change when NO is substituted by NO, while it
y1
/ŽClHN. Ždeg..
ŽHNO.
E Žau.
is observed at 2046.8 cm
topic effect ŽFig. 7.. In agreement with Ref. w1x, this
band can be assigned to the H-Cl stretching mode of
for the DClrHCl iso-
/
0.0
y590.774637
0.7
1.59
2908 Ž127.
1968 Ž44.
14
y1 . a
De kcal.mol
m ŽD.
Ž
1
4
y1
NO:HCl. The second band located at 2816.1 cm
vHCl Žcmy1
.
depends on the ŽNO.2 concentration, and its IR
intensity increases when the matrix is warmed. There
is no change on the frequency of this band after an
NO isotopic substitution, while it is largely red
vNO
dvHCl
dvNO
b
96
b
y15
y13
2
2 X
Elec. state
S
A
y1
shifted Ž777 cm . after the DClrHCl isotopic
a
D s E Žsubmolecules. – E Žcomplex..
change ŽFig. 7.. This band can be assigned to the
e
b
d
v
s v Žisolated molecule. – v Žcomplexated molecule..
1
4
H-Cl stretching mode of Ž NO. :HCl w1x.
2
4
. Theoretical study of the NO...HCl complex
tained from the new parametrized hybrid functional
are very close to those calculated from sophisticated
approaches as MP4 Žfourth-order. and QCISDŽT.
Žquadratic CI calculations.. The reparametrized func-
tional is denoted as B3LYPŽM.. In the present paper,
we use both hybride functionals ŽB3LYPŽM. and
B3LYP. to study the NO:HCl complex and their
submolecules. All calculations have been performed
using the Gaussian94 quantum chemical package
w24x. As it has already been shown w22,23x, the
6-311qqGŽ2d,2p. basis set of Pople et al. w25x is
suitable to study the H-bonded systems. Here, this
basis set is used for all atoms.
Several extensive studies on hydrogen-bonded
complexes, using DFT theory, have shown that, in
contrast to the local density approximation ŽLDA.
which is incapable of describing the properties of the
hydrogen bond, the nonlocal functionals Žparticularly
the hybride functional B3LYP w14,15x. have been
noted to result in a closer agreement with experimen-
tal and traditional ab-initio results w16–21x. Re-
cently, Latajka et al. w22,23x have evidenced that an
increase of the exact exchange part of B3LYP from
0
.20 to 0.35 improves the agreement between the
DFT results and the experimental ones. They have
shown that the energetic and structural results ob-
As shown in Table 2, the geometrical and vibra-
tional properties of isolated HCl and NO obtained
Table 2
Geometrical and vibrational properties of HCl and NO
Parameters
HCl
NO
B3LYP
B3LYPŽM.
B3LYP
B3LYPŽM.
r Ž A˚ .
1.2811
1.2739
1.1472
1.151
1.1391
a
a
1
.274
E Žau.
m ŽD.
y460.837686
y461.161413
y129.935841
y130.137637
1.17
1.17
0.13
0.08
a
a
1
.09
0.15
vŽcmy1
nexp
.
2922 Ž42.
2982 Ž43.
1953 Ž43.
2018 Ž50.
2885.98 Ž2870.7 b
a
.
1876 Ž1872.2 b
a
.
a
b
Ref. w26x. This work.

2
70
L. Krim, M.E. AlikhanirChemical Physics 237 (1998) 265–271
Table 4
Optimized geometrical properties of NO:HCl using B3LYPŽM.
the ClH...ON one. A similar energetic property has
been found for the XY:HF ŽXYsCO or NO. com-
Parameters
Bent ClH...NO
Bent ClH...ON
w x
plexes 27 . One can see that the H-O distance in the
ClH...ON complex is calculated larger than the H-N
distance in the ClH...NO isomer. The same trend was
rHCl Ž A˚ .
rNO
rHN
1.2769
1.1372
2.5000
177.3
1.2753
1.1397
2.5315
seen for the FH...ON and FH...NO complexes 27 .
The calculated vibrational frequencies using
B3LYPŽM. for both bent isomers as well as the
w x
/
/
/
/
ŽClHN. Ždeg..
ŽClHO.
ŽHNO.
177.1
127.4
ŽHON.
128.2
experimental values are presented in Table 5. The
calculated vibrational analysis has been performed in
the harmonic approximation. One can readily note
that the experimental frequencies are well repro-
duced by the B3LYPŽM. techniques. The frequency
shifts of the H-Cl and N-O stretching modes upon
complexation, denoted as dn1 and dn 2 respectively,
are listed in Table 5. It should be noted that the
experimental value of dn1 is positive Žred shift.,
while that of dn2 is negative Žblue shift.. The theoret-
E Žau.
y591.300175
0.7
y590.299712
0.4
D Žkcal.mol . a
y1
e
m ŽD.
Elec. state
1.54
A
1.35
A
2
X
2 X
a
D s E Žsubmolecules. – E Žcomplex..
e
from both functionals are in a satisfactory agreement
with the experimental data w26x. In Table 3 are listed
the geometrical and some vibrational properties of
two structures of NO:HCl obtained using the B3LYP
functional. In concordance with some recent calcula-
tions w1x, the linear geometry appears to be a transi-
tion structure with one imaginary frequency Ž75i
ical value of dn1 is positive for both isomers, but
only its value for the bent ClH...NO structure agrees
well with the experimental one. Furthermore, the dn2
value is negative for the ClH...NO structure and
positive for the ClH...ON one. As shown in Tables 3
and 5, the agreement between the theoretical dn1 and
dn2 values and the experimental ones is well im-
proved in going from B3LYP to B3LYPŽM..
y1
cm . corresponding to the inversion isomerization
of the bent structure. The bent geometry of the
ClH...NO isomer is found to be very slightly bound,
whose inversion barrier height is about 0.5 kcalrmol.
Only the bent structures of the two possible isomers
ŽClH...NO and ClH...ON. have been studied with the
B3LYPŽM. functional ŽTables 4 and 5.. It has been
Inspecting the calculated infrared intensities ŽTa-
ble 5. shows that the experimental detection of the
two n4 and n5 bands should be difficult because
they are found to be very weak. Moreover, if we
calculate the relative IR intensities of the fundamen-
shown that the ClH...NO isomer is more stable than
Table 5
Vibrational properties of the NO:HCl complex using B3LYPŽM. a
Symm. mode
Bent ClH...NO
Bent ClH...ON
Exp.
X
2827.5 Ž0.49 d
b
A
n1 ŽHCl str..
n2 ŽNO str..
n3 ŽNH str..
2937.2 Ž170.
2029.0 Ž56.
204.8 Ž8.
69.4 Ž3.
36.1 Ž0.5.
165.9 Ž32.
44.7
2963.7 Ž115.
2012.0 Ž56.
169.9 Ž29.
58.6 Ž2.
33.2 Ž0.5.
132.0 Ž33.
18
.
.
c
d
1880.3 Ž0.10
d
179.6 Ž0.08
.
n4 ŽHNO bend.
n5 ŽClHN bend.
n6 ŽO.P. bend.
XX
146.5 Ž0.09 d
43.2
A
.
e
dn1
dn2
e
y10.6
q6.4
y8.1
a
b
c
d
e
y1
y1
Frequencies are in cm . Calculated IR intensities are the absolute intensities and are given in km.mol
.
y1
Located at 2827.0 cm
Located at 1880.5 cm
in Ref. w1x.
y1
in Ref. w1x.
The relative IR intensities Žsee Table 1..
dn s n Žisolated molecule. – n Žcomplexated molecule..

L. Krim, M.E. AlikhanirChemical Physics 237 (1998) 265–271
271
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n1 band intensity, we obtain a good agreement
between the theoretical and experimental values.
We can thus deduce that the experimentally ob-
served species is a bent structure in which the H-
bonding takes place between the nitrogen and hydro-
gen atoms. In order to verify the reability of this
conclusion, a calculation has been performed for the
NO:FH complex at the same level of theory as the
NO:HCl complex. It has been shown that the experi-
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y1
y1
cm . and blue shift of the N-O subunit Ž84 cm
.
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w8x are only well calculated for a bent structure of the
FH...NO isomer, while for the NO...HF bent isomer,
the two frequencies are calculated to be red shifted.
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5
. Conclusions
From a codeposition of HCl with nitric oxide in
w17x C. Mijoule, Z. Latajka, D. Borgis, Chem. Phys. Lett. 210
an argon matrix, the NO:HCl hydrogen bonded com-
plex has been isolated. Two bands in the far infrared
region were experimentally observed. The NO:HCl
Ž1993. 279.
w18x Z. Latajka, Y. Bouteiller, J. Chem. Phys. 101 Ž1994. 9793.
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1
5
1
4
and NO:DCl isotopic bands were also recorded.
Using DFT aproach, four geometries Žtwo linear
and two bent structures. have been optimized for the
NO:HCl complex. It was shown that the experimen-
tal data are well reproduced only for the ClH...NO
bent structure in which the H-bonding occurs be-
tween the hydrogen atom of HCl and the nitrogen
atom of nitric oxide. It has been shown that the same
feature holds for the NO:HF complex.
1315.
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234 Ž1995. 159.
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Acknowledgements
One of us ŽL.K.. thanks D. Carr e` re for her help
during the experiments. We thank Prof. N. Lacome
for corrections to the English text.
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