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NO32…NO32 and NO32…p interactions in the crystal of urea
nitrate{{
Yulia V. Nelyubina, Konstantin A. Lyssenko,* Denis G. Golovanov and Mikhail Yu. Antipin
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Published on 30 August 2007 on http://pubs.rsc.org | doi:10.1039/B709180J
Received 18th June 2007, Accepted 23rd August 2007
First published as an Advance Article on the web 30th August 2007
DOI: 10.1039/b709180j
The geometrical and energy aspects of the NO32…NO32 and
NO32…p-system interactions were analyzed in the framework
of the charge density investigation in crystalline urea nitrate.
The results obtained have revealed that relatively weak anion–
anion and anion–p (cation) contacts contribute greatly to the
stabilization of the layered structure for this particular ionic
material.
It’s commonly assumed that in ionic materials the predominant
contacts are cation–anion ones due to the attractive electrostatic
component of these interactions. At the same time, there is a
number of both experimental and theoretical reports indicating the
occurrence in solids of short-range anion–anion contacts that can
occasionally be identified on the basis of some physico-chemical
data (see, e.g., ref. 1 and references therein). This bond formation
is not only a consequence of the geometry of neighboring ions,
namely, due to the forced shortened distance, but resulted from the
competition among them to attract electrons. The detailed analysis
of charge density in ionic crystals has revealed the presence of
anion–anion interactions for point-charge ions (such as halides in
rock-salts of NaCl type) as well as for rather bulky ones.2
Considering the formally repulsive character of the contacts
between two anions one can expect their energy to be extremely
small as compared to the cation–anion ones. However, in some
cases the crystal packing of the particular ionic material is
partly affected by such weak interactions. Thus, the importance
of anion–anion contacts in crystalline alkali halides has already
been discussed.3 Furthermore, as was recently reported, similar
Cl2…Cl2 interactions were found in the crystal of hydroxylammonium chloride.4
The anion–anion contacts playing a significant role in the crystal
packing, were also observed for the series of 1,3-dialkyl-4,5-bis(3amino-guanidino)imidazolidine-2-one salts where the formation
of centrosymmetric nitrate–nitrate dimers leads to a racemic
structure.5 It should be noted that according to the Cambridge
Structural Database (CSD) the occurrence of Cl2…Cl2 interactions on the basis of the geometrical criteria can be expected only
for 76 compounds, which is not comparable with total number of
chlorine salts.4 At the same time, nitrate…nitrate contacts (with a
O…O separation within the range of 2.7–3.3 Å) are observed for
A. N. Nesmeyanov Institute of Organoelemental Compounds of the
Russian Academy of Sciences, 119991, Vavilov Str., 28, Moscow,
Russia.. E-mail: kostya@xrlab.ineos.ac.ru; Fax: 495 135 5085;
Tel: 495 135 9214
{ CCDC reference number 651076. For crystallographic data in CIF or
other electronic format see DOI: 10.1039/b709180j
{ Electronic supplementary information (ESI) available: Additional
experimental details. See DOI: 10.1039/b709180j
This journal is ß The Royal Society of Chemistry 2007
23% (539 of 2324 ordered structures with the R-factor ,0.075) of
nitrate-containing crystals. As a result, based on rough analysis
of CSD we can suggest that consideration of NO32…NO32
interactions on both qualitative and quantitative levels is of great
importance for the description of the corresponding salts.
Apparently, the geometrical data alone cannot serve as an
unambigious indicator of chemical bonding. It is important to
indicate that earlier the interionic O…O bonds were reported
and analyzed in the crystal of danburite (CaB2Si2O8),6 where 11
bonding interactions for the O…O distance in the range of
2.32–3.36 Å were found. Moreover, the trinitromethanide
C(NO2)32 and dinitramide N(NO2)22 ions are known to exhibit
the intraionic O…O bonds between NO2-groups.7
In order to analyze whether the above NO32…NO32 contacts
are bonding or are repulsive in nature, in the current communication we performed a detailed charge density r(r) investigation in
the crystal of urea nitrate (1). The choice of 1 was due to the
presence in the solid state of NO32…NO32 interactions (the O…O
separation is close to the average value for the above distance
range) as well as the availability of the crystalline material.8 The
additional interest to 1 was caused by the close resemblance
of the cation under consideration and the guanidinium one in
corresponding salts, which was proven to be a very effective
receptor for anions.9 Another important point is the occurrence
of a nitrate…p-system of urea contacts in the crystalline 1.
Moreover, the latter is geometrically similar to an analogous
nitrate…guanidinium interaction found in the crystal of tetrakis(guanidinium) tris(3-sulfonatophenyl)phosphine nitrate.10 The
former is of interest as a model of an anion…p system (see ref. 11).
The fact that the nitrate anion in 1 simultaneously participates
in the formation of two different types of interactions gives us the
possibility to evaluate their energetics and analyze their role in the
crystal structure formation. To accomplish this we performed
the topological analysis of the r(r) function in 1 by means of
Bader’s Atoms in Molecule (AIM)12 theory on the basis of the
high-resolution X-ray diffraction (XRD) data.13
In accordance with previous investigations8 the crystal of 1 is
‘‘built’’ by NO32 anions and urea cations protonated via O(1)
atoms. The latter results in the elongation of the CLO bond up to
1.3077(3) Å as compared with crystalline urea (1.2565(5) Å).14 The
difference in bonding graphs of cation 1 and urea molecule also
affects the C–N separation, which is equal to 1.3173(4) and
1.3211(4) Å in the case of the former and 1.3384(4) Å for the latter.
The ions in the crystal of 1 are held together by the O–H/N–
H…O hydrogen bonds of intermediate strength (the O/N…O
distances are 2.6037(4)–2.9688(4) Å with the smallest value in the
case of the O(1)–H(1O)…O(4) one) thus forming the H-bonded
sheets in such a way that any ion is surrounded by 4 counter-ions
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Fig. 1 The fragment of the H-bonded sheet of 1 in the atom
representation by thermal ellipsoids at p = 80%. The additional O…N
contacts are drawn by green dash lines.
and 2 ones with the same charge (Fig. 1). The realization of the
former also leads to the occurrence of additional O(1)…N(1)
contacts (the N…O separation is 3.0312(4) Å). The above
supramolecular associates are assembled into a 3-D framework
through the nitrate…nitrate and nitrate…p-system interactions.
Analyzing the bonding pattern in 1 more closely one can bring up
the urea+…(NO32)2…urea+ ‘tetramers’ (Fig. 2A) each interlinking
four H-bonded sheets that leads to the layered structure where the
sheets are shifted relative to the neighboring ones (Fig. 2B).
It is important to indicate that the corresponding interatomic
distances O(3)…O(39) and O(3)…C(10) are very close to each
other and equal to 3.0273(4) and 3.0201(4) Å, respectively. For
comparison, the O…C separation in the crystal of tetrakis(guanidinium) tris(3-sulfonatophenyl)phosphine nitrate10 is 3.087 Å.
Therefore, based on the geometrical parameters of these contacts
and the fact that they play the same role in the formation of crystal
Fig. 2 The tetramer formed through the NO3…NO3 and
NO3…p-system contacts (A) and the fragment of the crystal packing for
1 representing the formation of layered structure (B).
992 | CrystEngComm, 2007, 9, 991–996
packing of 1, one can expect their strength to be very similar. As a
consequence, it was the point of interest to investigate whether the
NO32…NO32 and NO32…p-system contacts observed in the
solid correspond to attractive interactions or, in contrast, are
forced in nature.
To accomplish this, we have performed the search for bond
critical points CPs (3, 21) (hereinafter BCPs) in the interatomic
area. Thus, the values of the r(r) function in the BCPs for C–N/C–
O bonds (2.503–2.536/2.402 e Å23) in 1 as well as the ellipticity (e),
which serves as a measure of the p component, indicate the partial
double-bond character of the C–N ones (0.29–0.30) while the
C(1)–O(1) bond (0.14) is almost a single one. For comparison, the
C–N/C–O bonds in the urea molecule16 are characterized by nearly
equal values of both r(r) and e being 2.538/2.536 e Å23 and
0.19/0.15, respectively.
As was expected, the BCPs were localized for all of the above
H-bonds as well as for shortened O(3)…O(39) and O(3)…C(1)
contacts in the crystal of 1. The latter can be considered as an
O…p interaction because the CLN bonds in urea cation exhibit a
pronounced degree of double bond character and the lone pair of
oxygen is directed to the p-orbital of the carbon atom (see ref. 11).
In addition, a small number of BCPs attributed to the considerably
long cation–cation and anion–anion interactions was also found
(Table 1). In line with the topological parameters in the corresponding BCPs the interionic interactions are all of a closed-shell
type (the positive +2r(r) values vary in the broad range of
0.23–2.73 e Å25, and electron energy densities he(r) are 0.00069–
0.00567 a.u.) with the exception of the O(1)–H(1O)…O(4) H–bond
(+2r(r) = 5.75 e Å25, he(r) = 20.00227 a.u.) corresponding to the
intermediate type of interatomic interactions (Table 1). It is to be
mentioned that in the case of crystalline urea14,15 where the
molecules are assembled by N–H…O and weak N…N contacts
the absence of an acidic proton at the carbonyl group results in
predominantly electrostatic nature of the hydrogen bonds.
Along with the BCPs we have also located a number of ring CPs
(3, +1) in the centers of H-bonded cycles, such as those observed
for the cation–anion pair (Fig. 3), and cage CPs (3, +3) caused by
the three-dimensional framework in the solid of 1. The characteristic set of critical points satisfies the Morse equation.12
The chemical bonding pattern for 1, in particular, the formation
of the above ‘tetramer’ and occurrence of unusual nitrate…nitrate
and urea+…urea+ contacts, is also sustained by the ‘‘easy-to-see’’
description of the r(r) distribution provided by the qualitative
analysis of the deformation electron density (DED). Thus, the
DED distribution in the plane of the ionic H-bonded pair was
found to be characterized by the expected features (Fig. 3). The
DED peaks attributed to electron lone pairs (LPs) are located in
the vicinity of each oxygen atom and directed toward the
hydrogens of NH2-fragments that is common for the H-bonds.16
The depletion of the density between the interacting atoms is
indicative of the substantial contribution of the electrostatic
component.
The analogous trend is observed for the ‘tetramer’ in the plane
formed by N(3)O(3) groups of both nitrates. In this case the
corresponding contacts can be described in terms of the ‘‘peak-tohole’’ formalism, i.e. the DED peaks localized along the line of
the N–O bond (Fig. 4A) and LP of the O(3) atom (Fig. 4B) are
directed toward the areas of the electron density depletion near
the oxygen and the carbon atoms, respectively. As a result of such
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Table 1 Topological parameters of the r(r) in the CPs (3, 21) for the intermolecular contacts in the crystal of 1
Interaction
R/Å
r(r)/e Å23
+2r(r)/e Å25
2v(r)/a.u.
he (r)/a.u.
Econt/kcal mol21
O(2)…H(1NB)
O(3)…H(2NB)
O(4)…H(1OA)a
O(2)…H(1NAB)
O(3)…H(2NAC)
O(1)…N(1D)
O(3)…O(39)
O(3)…C(10)
O(4)…O(3B)
O(4)…O(2-)
O(1)…N(1E)
O(4)…H(2NBC)
O(4)…H(2NB9)
O(2)…H(2NAF)
N(1)…H(2NBF)
1.957(5)
1.905(4)
1.597(4)
1.959(5)
1.967(5)
3.0312(4)
3.0273(4)
3.0201(4)
3.0814(4)
3.4776(4)
3.2602(4)
2.677(5)
3.006(5)
3.095(5)
3.100(5)
0.126(1)
0.183(1)
0.364(1)
0.114(1)
0.140(1)
0.047(1)
0.048(1)
0.051(1)
0.027(2)
0.014(2)
0.037(2)
0.047(2)
0.028(2)
0.020(2)
0.035(2)
2.73(1)
2.53(1)
5.75(1)
2.69(1)
2.56(1)
0.89(1)
0.81(1)
0.73(1)
0.55(2)
0.23(2)
0.53(2)
0.68(1)
0.40(2)
0.35(2)
0.46(2)
0.01703
0.02278
0.06419
0.01570
0.01787
0.00450
0.00429
0.00418
0.00247
0.00098
0.00281
0.00385
0.00200
0.00155
0.00249
0.00567
0.00174
20.00227
0.00608
0.00433
0.00234
0.00203
0.00168
0.00160
0.00069
0.00136
0.00162
0.00105
0.00102
0.00112
5.3
7.2
20.1
4.9
5.6
1.4
1.4
1.3
0.8
0.3
0.9
1.2
0.6
0.5
0.8
a
The H(1AO) atom is obtained from the basic one by the symmetry operation x, y 2 2, z; H(1NAB) and O(3B) by 2x + 2, y 2 0.5, 2z +
1.5; H(2NAC) and H(2NBC) by 2x + 1, y 2 0.5, 2z + 0.5; N(1D) by 2x + 2, y + 0.5, 2z + 1.5; O(39) and H(2NB9) by 2x + 1, 2y, 2z + 1;
C(10) by x, 2y + 0.5, z 2 0.5; O(2-) by x, 2y 2 0.5, z 2 0.5; N(1E) by 2x + 2, 2y + 1, 2z + 1; H(2NAF) and H(2NBF) by x, 2y + 0.5,
z + 0.5.
Along with the anion–anion contact, nitrate participates in the
formation of the bifurcated interaction with the next-nearest NO32
neighbors (Fig. 5A). The O…O separations for O(4)…O(3B) and
O(4)…O(2-) contacts are equal to 3.0814(4) and 3.4776(4) Å. The
examination of the DED distribution in the region of the latter
(Fig. 5B) has revealed that both O…O contacts are, to some
Fig. 3 The static deformation electron density in the plane of the cation–
anion pair in the crystal of 1. Contours are drawn with a 0.1 e Å23
interval, the negative contours are dashed.
a similarity, the described supramolecular associate is an ideal
system for the comparative analysis of the analogous by nature but
different by charges nitrate…nitrate and nitrate…p-system types of
interactions at the quantitative level.
Fig. 4 The DED in the area of the O(3)…O(39) (A) and O(3)…p-system
(B) interactions. Contours are drawn with 0.1 e Å23 interval, the negative
contours are dashed.
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Fig. 5 The fragment of the crystal packing in 1 representing the
formation of additional nitrate…nitrate contacts (A) and the DED in the
plane formed by O(4), O(2-) and O(3B) atoms of NO2-groups (B)
(contours are drawn with 0.1 e Å23 interval, the negative contours are
dashed).
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extent, of a ‘‘peak-to-hole’’ type. However, since the degree of their
directionality is open to questions, one can assume that the
O(4)…O(2-) interaction is much weaker than the second one
which, in turn, should be extremely weak as compared to the
H-bonds in the crystal of 1. It is to be noted that the former
interlinks the H-bonded sheets and can thus be the consequence of
the layer structure of 1. Furthermore, it seems that even the
O(4)…O(3B) contact is resulted from the ‘‘constricting effect’’ of
the relatively strong H-bonds.
In addition to these interlayer contacts the BCP and its
associated bond path were located for the cation–cation
O(1)…N(1E) interaction with the O…N distance equal to
3.2602(4) Å. For comparison, see the above value in the case of
the similar O…N interaction between the urea fragments lying in
the plane of the sheet. Accordingly, the interatomic separation
for the O(4)…O(2-) contact is considerably smaller than for the
O(1)…N(1E) one. Moreover, in contrast to the described O…O
interaction, the DED distribution in the area of the latter (Fig. 6) is
attributed to the ‘‘peak-to-peak’’ type, i.e. overlap of two electron
lone pairs.
The possibility to estimate the integrated strength of the
interionic contacts can be provided by the evaluation of charge
transfer accompanying their formation. To accomplish this we
determined the atomic basins (V) surrounded by a zero-flux
surface and integrated r(r) over V to obtain atomic charges.
Although the integrated Langrangian (L(r) = 21/4+2r(r)) for
every V has to be zero,12 reasonably small numbers with an
average value of 0.8 6 1024 a.u. and maximum L(r) observed for
the C(1) atom (2.8 6 1024 a.u.) were obtained. The atomic
charges estimated according to this procedure lead to the value of
charge transfer 0.53 e with the charge leakage equal to 0.001 e.
Such redistribution of charge density indicates that the cation–
anion interactions are characterized by the relatively high energies.
It should be noted that the charge transfer in a recently analyzed
hydroxylammonium chloride4 was 0.72 e. The absolute values of
atomic charges for 1 in comparison with those for the crystalline
urea can give us more specific information about the bonded
pattern in 1. Thus, the obtained values in the case of the cation
1/urea molecule14 were found to be 20.97/21.18 e for oxygen;
1.38/1.67 e for carbon; 21.03 and 20.95/21.21 e for nitrogen and
0.36 4 0.43/0.4840.49 e for hydrogen atoms, respectively. The
hydrogen atom of the OH group is characterized by the maximum
positive value equal to 0.45 e.
Fig. 6 The DED in the area of the O(1)…N(1E) interaction. Contours
are drawn with 0.1 e Å23 interval, the negative contours are dashed.
994 | CrystEngComm, 2007, 9, 991–996
The difference for the O and N charges agrees well with the
occurrence of electrostatic O…N contacts, which can be described
as a transfer of the oxygen’s LP to the nitrogen, e.g. for the
O(1)…N(1E) contact the ONC angle is 78.1(2)u. A similar
tendency is observed for the C(1) atom due to the transfer of
electron density from the anion. The variation of charges in the
case of the N and H atoms apparently results from the formation
of N–H…O bonds surpassing those in an urea crystal by both
number and strength.14,15 For information, the values of the
atomic charges in the nitrate anion are +0.58 e in the case of N(3)
and 20.33, 20.35 and 20.37 e for O(4), O(2) and O(3) atoms. It
should be noted that the latter correlates with the difference in the
atomic energy values (Eat) obtained by integration of he(r)12 over V
for the corresponding oxygens (DEat between the O(2)/O(3) and
O(4) atoms is 20.096/20.183 a.u.).
In addition to the atomic charges in the crystal of 1, we also
estimated the atomic volumes according to an analogous
procedure. Since the integration was carried out numerically, it is
important to indicate that their sum in the crystal (117.02 Å3)
reproduces the unit cell volume per molecule (117.17 Å3) with the
relative error 0.1%. It is to be mentioned that the total volumes of
NH2 groups (22.13 and 21.96 Å3 for N(1) and N(2)) are smaller
than those of the urea molecule (25.4 Å3).14 This also proves the
multiplicity of contacts formed by the latter. However, drawing
any conclusion based on the comparison of the same values for the
CO fragment (20.40 Å3 in 1 and 21.93 Å3 in urea crystal) is
complicated by the protonated character of urea in the solid 1.
The energy of the above interionic contacts (Econt), in particular,
the nitrate…nitrate and urea+…urea+ ones, in the crystal of 1 was
estimated by means of Espinosa’s correlation scheme17—the
semiquantitive relationship between Econt and the value of the
v(r) function in the BCP. Thus, the Econt for N–H…O hydrogen
bonds varies in the range of 0.5–7.2 kcal mol21 (Table 1) with the
greatest one corresponding to the shortest contact. The maximal
Econt (20.1 kcal mol21) is observed in the case of the O(1)–
H(1)…O(4) interaction. It is to be mentioned that the energy
of intermolecular H-bonds in the crystalline urea amounts to
4.6 kcal mol21.14 The values of Econt for the additional anion–
anion (Fig. 5) and cation–cation (Fig. 6) interactions in 1 were
found to be 0.3–0.9 kcal mol21. As expected, the energies of the
O(3)…O(3) and O(3)…p-system contacts are very similar and
equal to 1.4 and 1.3 kcal mol21. For comparison, the Econt of
the O…O interactions in danburite6 is in the range of 1.1–
16.3 kcal mol21 with the maximum one for the shortest (2.32 Å)
distance. In the case of the crystalline MgO the corresponding
value (O…O separation is 2.98 Å)2 amounts to 3.2 kcal mol21.
Such a decrease of the O…O energy in 1 as compared to MgO and
danburite is clearly a consequence of the lower charge density on
oxygens in the NO32 moiety, i.e. a less effective overlap of valence
shells between the O atoms.
The obtained Econt values lead to the value of the total energy
for nitrate…nitrate, urea+…urea+ and nitrate…urea+ interactions
equal to 2.4, 3.1 and 46.8 kcal mol21 which is in good agreement
with the charge transfer accompanying the formation of interionic
H-bonds. An analogous tendency is observed for the strength of
the contacts which participate in the formation of the H-bonded
sheets (47.3 kcal mol21), and those interlinking the above
associates (5.0 kcal mol21). However, the latter amounts to 11%
of the overall Econt for the sheets and is thus independent of the
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charge of interacting species. It is to be mentioned that, due to the
ionic character of 1, the sum of estimated energies, in contrast to
the molecular crystals (see ref. 18), cannot be directly compared
with the lattice energy. The latter by definition includes the large
contribution from the charge redistribution upon the dissociation
of crystalline solids.19 Moreover, the other energy parameters—
those due to dispersion and repulsion—must also be taken into
consideration.
Thus, according to both the qualitative analysis of the charge
density distribution and the energetics of the chemical bonding in 1
the studied structure can be described as a layered one, with the
energy of the contacts in the sheets being 10 times greater than
those of the interlayer. Furthermore, the bonding between layers in
1 on the quantitative level is comparable with the graphite one. On
the other hand the ideal complementarity of urea+ and nitrate ions
in the layer allows us to expect the presence of such associates in
the corresponding solutions. As a result, one can assume that the
urea nitrate serves as a suitable model for investigation of the
graphite intercalation and/or forms cocrystals of graphite intercalate type.
Topological analysis of the electron density distribution in
the crystal of 1 indicates that the occurrence of NO32…NO32
bonds is not a manifestation of the ‘‘constricting effect’’ of the
strong cation…anion contacts but resulted from not fully
electrostatic nature of interaction between like-charged moieties.
At the same time, the statistical analysis of CSD performed has
revealed a more pronounced tendency of the nitrate salts to display
such type of contacts in comparison with chloride-containing
compounds.
Accordingly, the nitrate…nitrate and nitrate…p-system interactions affect the crystal packing of the particular ionic material
and even contribute greatly to the stabilization of its layered
structure. Therefore, in spite of the considerable weakness of
anion–anion interactions they may and do play an important role
in the formation of a particular crystal pattern and thus determine
the mutual disposition of strongly bounded supramolecular
entities.
Experimental
Crystals of 1 (CH5N3O4, M = 123.08) are monoclinic, space group
P21/c, at 100 K: a = 7.9761(1), b = 8.2004(1), c = 7.3668(1) Å,
b = 103.414(1)u, V = 468.697(10) Å3, Z = 4 (Z9 = 1), dcalc =
1.744 g cm23, m(Mo Ka) = 1.74 cm21, F(000) = 256. The
intensities of 33142 reflections were measured with a Bruker
SMART APEX2 CCD diffractometer [l(Mo Ka) = 0.71072 Å,
v-scans, 2h , 110u] and 5960 independent reflections [Rint =
0.0320] were used in further refinement. The structure was solved
by a direct method and refined by the full-matrix least-squares
technique against F2 in the anisotropic–isotropic approximation.
The hydrogen atoms were located using the Fourier synthesis of
electron density and refined in the isotropic approximation. For 1
the refinement converged to wR2 = 0.0985 and GOF = 1.000 for
all independent reflections (R1 = 0.0330 was calculated against F
for 4570 observed reflections with I . 2s(I)). All calculations were
performed using SHELXTL PLUS 5.0.
The multipole refinement was carried out within the Hansen–
Coppens formalism20 using the XD program package21 with
the core and valence electron density derived from wave functions
This journal is ß The Royal Society of Chemistry 2007
fitted to a relativistic Dirac–Fock solution.22 Before the refinement,
the O–H and N–H bond distances were normalised to the values
obtained from the neutron data.8 The refinement was carried out
against F and converged to R = 0.0229, Rw = 0.0221 and GOF =
0.68 for 4526 merged reflections with I . 3s(I). The total electron
density function was positive everywhere and the maxima of
residual electron density located in the vicinity of nuclei were not
more than 0.09 e Å23. Topological analysis of the experimental
r(r) function was carried out using the WINXPRO program
package.23
Acknowledgements
This study was financially supported by the Russian
Foundation for Basic Research (Project 06-03-32557), the
Foundation of the President of the Russian Federation
(Federal Program for the Support of Leading Scientific
Schools, Grant NSh 1060.2003.30, and Young Doctors,
Grant MK-1054.2005.3) and the Russian Science Support
Foundation.
Notes and references
1 M. A. Carvajal, I. Garcia-Yoldi and J. J. Novoa, J. Mol. Struct.
(THEOCHEM), 2005, 727, 181.
2 S. Gottlicher and A. Vegas, Acta Crystallogr., Sect. B, 1988, 44, 362;
V. Tsirelson, Yu. Abramov, V. Zavodnik, A. Stash, E. Belokoneva,
J. Stahn, U. Pietsch and D. Feil, Struct. Chem., 1998, 9, 249.
3 L. Pauling, The nature of the chemical bond, and the structure of
molecules and crystals, 3rd edn, Cornell University Press, Ithaca, NY,
1960; A. M. Pendás, A. Costales and V. Luaña, J. Phys. Chem., 1998,
102, 6937.
4 Yu. V. Nelyubina, M. Yu. Antipin and K. A. Lyssenko, J. Phys. Chem.
A, 2007, 111, 1091–1095.
5 Y. V. Nelyubina, K. A. Lyssenko, A. N. Kravchenko, M. Yu. Antipin
and A. S. Sigachev, Russ. Chem. Bull., 2006, 3, 387.
6 V. Luaña, A. Costales, P. Mori-Sánchez and A. M. Pendás, J. Phys.
Chem., 2003, 107, 4912.
7 J. Cioslowski, L. Edgington and B. B. Stefanov, J. Am. Chem. Soc.,
1995, 117, 10382; E. A. Zhurova, V. G. Tsirelson, A. I. Stash and
A. A. Pinkerton, J. Am. Chem. Soc., 2002, 124, 4574.
8 J. E. Worsham Junior and W. R. Busing, Acta Crystallogr., Sect. B,
1969, 25, 572.
9 M. D. Best, S. L. Tobey and E. V. Anslyn, Coord. Chem. Rev., 2003,
240, 3.
10 A. Katho, A. C. Benyei, F. Joo and M. Sagi, Adv. Synth. Catal., 2002,
344, 278.
11 M. Egli and S. Sarkhel, Acc. Chem. Res., 2007, 40, 197.
12 R. F. W. Bader, Atoms in molecules. A quantum theory, Clarendron
Press, Oxford, 1990; R. F. W. Bader, J. Chem. Phys. A, 1998, 102, 7314.
13 T. S. Koritsanszky and P. Coppens, Chem. Rev., 2001, 101, 1583;
C. Gatti, Z. Kristallogr., 2005, 220, 399; V. G. Tsirelson and
R. P. Ozerov, Electron density and Bonding in Crystals: Principles,
Theory and X-Ray Diffraction experiments in Solid State Physics And
Chemistry, IOP Publishing Ltd., Bristol, Philadelphia, 1996.
14 H. Birkedal, D. Madsen, R. H. Mathiesen, K. Knudsen, H. P. Weber,
P. Pattison and D. Schwarzenbach, Acta Crystallogr., Sect. A, 2004, 60,
371.
15 V. Zavodnik, A. Stash, V. Tsirelson, R. De Vries and D. Feil, Acta
Crystallogr., Sect. B, 1999, 55, 45.
16 K. A. Lyssenko and M. Y. Antipin, Russ. Chem. Bull., 2006, 55, 1.
17 E. Espinosa, E. Molins and C. Lecomte, Chem. Phys. Lett., 1998, 285,
170; E. Espinosa, I. Alkorta, I. Rozas, J. Elguero and E. Molins, Chem.
Phys. Lett., 2001, 336, 457.
18 K. A. Lyssenko, A. A. Korlyukov, D. G. Golovanov, S. Yu. Ketkov
and M. Yu. Antipin, J. Phys. Chem. A, 2006, 110, 6545; I. V. Glukhov,
K. A. Lyssenko, A. A. Korlyukov and M. Yu. Antipin, Russ. Chem.
Bull. Int. Ed., 2005, 54, 547; K. A. Lyssenko, A. A. Korlyukov and
M. Yu. Antipin, Mendeleev Commun., 2005, 90.
CrystEngComm, 2007, 9, 991–996 | 995
View Article Online
and Topological Analysis of Charge Densities from Diffraction Data,
2003.
22 Z. Su and N. K. Hansen, Acta Crystallogr., Sect. A, 1998, 54, 646.
23 A. Stash and V. Tsirelson, WinXrpo, A program for Calculation of the
Crystal and Molecular Properties Using the Model Electron Density,
2001; A. Stash and V. G. Tsirelson, Acta Crystallogr., 2002, 35, 371.
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Published on 30 August 2007 on http://pubs.rsc.org | doi:10.1039/B709180J
19 L. Glasser and H. D. B. Jenkins, J. Am. Chem. Soc., 2000, 122, 632;
L. Glasser and H. D. B. Jenkins, Chem. Soc. Rev., 2005, 34, 866.
20 N. K. Hansen and P. Coppens, Acta Crystallogr., Sect. A, 1978, 34, 909.
21 T. S. Koritsansky, S. T. Howard, T. Richter, P. Macchi, A. Volkov,
C. Gatti, P. R. Mallinson, L. J. Farrugia, Z. Su and N. K. Hansen,
XD – A Computer Program Package for Multipole Refinement
996 | CrystEngComm, 2007, 9, 991–996
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