Three dimensional framework structures of N,N′,N′- tricyclohexylguanidinium halides

Article abstract of DOI:10.1007/s10870-012-0352-3

The structures of two salts of N,N′,N′-tricyclohexylguanidinium with chloride (1) and bromide (2) have been determined at 201 K. Crystals of both 1 and 2 are in the cubic space group P213, with Z = 4 and cell dimensions a = 12.5940(18) A (1) and a = 12.7352(8) A (2). In the isomorphous structures of 1 and 2, the orientation of the cyclohexyl rings around the planar CN₃ ⁺ unit produces steric hindrance. As a consequence of this particular orientation of the tricyclohexylguanidinium cation (hereafter denoted CHGH ⁺), hydrogen bonding is restricted to classical N-H·X and non-classical (cyclohexyl) C-H·X hydrogen bonds. Consequently, each guanidinium cation (CHGH⁺) is connected to three surrounding X^- anions and each X^- anion is connected with three surrounding cations to form three-dimensional structures. Springer Science+Business Media, LLC 2012.

Full text of DOI:10.1007/s10870-012-0352-3

J Chem Crystallogr (2012) 42:1022–1028
DOI 10.1007/s10870-012-0352-3
ORIGINAL PAPER
Three Dimensional Framework Structures of N,N0,N00-
Tricyclohexylguanidinium Halides
•
Farouq F. Said Basem Fares Ali Darrin S. Richeson
•
•
•
Qutaiba Abusalem Tara Kell
Received: 3 February 2012 / Accepted: 4 August 2012 / Published online: 23 August 2012
Ó Springer Science+Business Media, LLC 2012
Abstract The structures of two salts of N,N0,N00-tricy-
clohexylguanidinium with chloride (1) and bromide (2)
have been determined at 201 K. Crystals of both 1 and 2
are in the cubic space group P213, with Z = 4 and cell
[2, 3], crystal engineering [4, 5] and material science [6, 7].
The interactions governing the crystal organization are
expected to affect the packing and ultimately the specific
properties of solids.
˚
˚
dimensions a = 12.5940(18) A (1) and a = 12.7352(8) A
(2). In the isomorphous structures of 1 and 2, the orienta-
On the other hand, guanidines are of special interest due to
their possible application in medicine [8, 9]. They are con-
sidered super bases that readily accept a proton to generate
guanidinium cations [10]. The structural features and
hydrogen bonding array provided by these cations suggest
that they are good building blocks for the formation of
supramolecular entities. However, their significance in the
generation of multi-dimensional networks has only recently
been appreciated [11–14]. Some of these studies were
focused on guanidinium derivatives, which are attempting to
analyze the influence of the different substituents of guan-
idinium and the variation of anion on the packing interac-
tions that govern the crystal organization and as
consequence, the properties of the resulting salts [15–17]. It
remains a difficult task to predict and control the crystal
structures of such compounds. Intermolecular interactions
are at the heart of supramolecular chemistry [1], and the field
of crystal supramolecularity seeks to understand intermo-
lecular interactions by analyses of crystal packing. Inter-
molecular interactions includes both classical and non-
classical hydrogen bonding (see for example references [18,
19]), halogenꢀꢀꢀhalogen interactions (see for example refer-
ences [20, 21]), arylꢀꢀꢀaryl interactions [22], Xꢀꢀꢀaryl [23] and
C–Hꢀꢀꢀaryl interactions [24].
?
tion of the cyclohexyl rings around the planar CN3 unit
produces steric hindrance. As a consequence of this par-
ticular orientation of the tricyclohexylguanidinium cation
(hereafter denoted CHGH?), hydrogen bonding is restric-
ted to classical N–HꢀꢀꢀX and non-classical (cyclohexyl)
C–HꢀꢀꢀX hydrogen bonds. Consequently, each guanidinium
cation (CHGH?) is connected to three surrounding
X- anions and each X- anion is connected with three
surrounding cations to form three-dimensional structures.
Keywords N–HꢀꢀꢀX and C–HꢀꢀꢀX hydrogen bonding ꢀ
Trisubstituted guanidinium cation ꢀ Supramolecular
structure
Introduction
Non-covalent interactions play an important role in orga-
nizing structural units in both natural and artificial systems
[1]. They exercise important effects on the organization
and properties of many materials in areas such as biology
In connection with ongoing studies [15–17, 25] of the
structural aspects of N,N0,N00-trisubstituted guanidinium
salts containing different anions, we herein report the
crystal structures of the compounds, N,N0,N00-tricy-
clohexylguanidinium with chloride (1) and bromide (2),
along with an analysis of the supramolecular aspects of
these crystal structures.
F. F. Said ꢀ B. F. Ali (&) ꢀ Q. Abusalem
Department of Chemistry, Al al-Bayt University, Mafraq 25113,
Jordan
e-mail: bfali@aabu.edu.jo
D. S. Richeson ꢀ T. Kell
Department of Chemistry, University of Ottawa, Ottawa,
ON KIN 6N5, Canada
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J Chem Crystallogr (2012) 42:1022–1028
1023
It is noteworthy that Cai and Hu [26] have reported the
structure of N,N0,N00-tricyclohexylguanidinium chloride at
298 K. While these researchers determined the chloride
structure at a higher temperature, they did not interpret the
crystal packing in terms of intermolecular interactions or
with respect to the supramolecular aspects of these crystals,
as is done in this work.
non-hydrogen atoms. All hydrogen atom positions were
either located from the difference Fourier Map or were
calculated geometrically and were riding on their respec-
tive carbon atoms. In 1, three atoms in the cyclohexyl
group were disordered and modeled over two positions
with relative occupancies of 85:15 %. In 2, two atoms in
the cyclohexyl group were disordered and modeled over
two positions with relative occupancies of 87:13 %.
With the exception of the minor component of the
cyclohexyl disorder, all non-hydrogen atoms were refined
with anisotropic thermal parameters. In 1, the largest
Experimental
3
˚
residual electron density peak (0.156 e/A ) was associated
Synthesis
with the disordered portion of the cyclohexyl ring,
Synthesis and crystallization of N,N0,N00-tricyclohexyl-
guanidinium chloride, (CHGH?)Cl- 1. In a round bottom
flask, a combination of 0.071 g (1.34 mmol) ammonium
chloride and 0.41 g (1.34 mmol) N,N0,N00-tricyclohexyl-
guanidine were dissolved in 10 mL of distilled water. A
white precipitate of (CHGH?)Cl- was deposited immedi-
ately from the solution (0.43 g, 94.1 % yield). The product
was crystallized from a mixture of methanol and distilled
water to give white cubic crystals. Anal. Calcd for
C19H36ClN3: C, 66.73; H, 10.61; N, 12.29. Found: C,
66.49; H, 10.33; N, 11.97.
whereas, the largest residual electron density peak in 2
3
˚
(0.322 e/A ) was associated with the Br1 atom. Full-matrix
least-squares refinement on F2 gave R1 = 0.0481 and
wR2 = 0.1081 and R1 = 0.0417 and wR2 = 0.1025 at
convergence for 1 and 2, respectively.
Results and Discussion
Molecular Structure
Synthesis and crystallization of N,N0,N00-tricyclohexyl-
guanidinium bromide, (CHGH)?Br-, 2. In a round bottom
flask, a combination of 0.131 g (1.34 mmol) ammonium
bromide and 0.41 g (1.34 mmol) N,N0,N00-tricyclohexyl-
guanidine were dissolved in 10 mL of distilled water. A
white precipitate of (CHGH)?Br- was deposited immedi-
ately from the solution (0.48 g, 92.3 % yield). The product
was crystallized from a mixture of methanol and distilled
water to give white cubic crystals. Anal. Calcd for
C19H36BrN3: C, 59.05; H, 9.39; N, 10.87. Found: C, 59.21;
H, 9.17; N, 10.67.
Structures of the title compounds 1 and 2, are presented in
Fig. 1 and are typical N,N0,N00 trisubstituted guanidinium
halide salts with normal geometric parameters [15–17, 25].
The central guanidinium fragment of the cation in both salts
is planar [sum of NCN angles is 360°] with bond lengths
and angles as expected for a central Csp2 hybridization,
accounting for charge delocalization between the three C–N
bonds. The bond length C1–N1 [in the range 1.337(3)–
˚
1.340(4) A] is comparable with literature averages for tri-
substituted guanidinium salts, for example, triphenylguan-
˚
idinium bromide (1.328(3), 1.330(3) and 1.336(3) A [29]),
N-benzoyl-N0,N00-diphenylguanidinium chloride [1.379(2),
0
00
˚
1.321(2), 1.326(2) A], bis(N,N ,N -triisopropylguanidini-
um) fumarate-fumaric acid (1/1) (1.331 (3), 1.334(3) and
X-Ray Crystallography
˚
1.335(3) A [30]) and unsubstituted guanidinium cations
˚
(1.321 and 1.328 A, respectively [31]). The cyclohexyl ring
Crystals of compounds 1 and 2 were grown from a solution
of methanol and water. Single colorless blocks of 1 and 2
suitable for X-ray diffraction measurements were each
mounted on individual glass fibres. Unit cell measurements
and intensity data collections were performed on a Bruker-
AXS SMART 1 k CCD diffractometer [27] at 202 K using
graphite monochromatized Mo Ka radiation (k = 0.71073
has the normal chair conformation with conventional bond
lengths and angles. Selected geometrical parameters for
both salts are listed in Table 2.
It is noteworthy that the disorder of three atoms in the
cyclohexyl group in 1 (relative occupancies of 85:15 %)
and three atoms in 2 (relative occupancies of 87:13 %).
This might be related to the size of the anion and how
efficient the packing is. With the chloride and bromide
anions the size is much smaller as compared to the iodide
anion (no disorder observed) [25]. Therefore, the bigger the
size the more efficient the packing as it well fill more
space, and well also interact more closely with the N–H
and C–H donors without lose in the packing preventing any
˚
A). The data reduction included a correction for Lorentz
and polarization effects, with an applied multi-scan
absorption correction SADABS [27]. The crystal data and
refinement parameters for 1 and 2 are listed in Table 1.
Interatomic distances and angles are listed in Table 2. The
reflection data were consistent with a cubic system; P213.
The crystal structures were solved and refined using the
SHELXTL program suite [28]. Direct methods yielded all
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J Chem Crystallogr (2012) 42:1022–1028
Table 1 Crystal data and structure refinement for 1 and 2
Identification code
CCDC 865452
CCDC 865451
Empirical formula; Formula weight
Temperature/(K)
C19H36ClN3; 341.45
201(2)
C19H36BrN3; 386.42
201(2)
˚
k/(A)
0.71073
0.71073
Crystal system; Space group
Unit cell dimensions
Cubic, P213
Cubic, P213
˚
a/(A)
12.5940 (18)
12.7352(8)
3
˚
Volume/(A )
1997.5 (5)
2065.5(2)
Z
4
4
Density (calculated)/(Mg/m3)
1.135
1.243
l/(mm-1
)
0.196
1.995
F(000)
Crystal size/(mm3)
750
824
0.10 9 0.10 9 0.10
2.29 to 26.27
0.10 9 0.10 9 0.08
3.20 to 25.67
Theta range for data collection
Index ranges
-15 B h B 15, -15 B k B 15, -15 B l B 15
14889
-15 B h B 15, -15 B k B 15, -15 B l B 13
17009
Reflections collected
Independent reflections
Completeness to theta = 25.0°
Absorption correction
Max. and min. transmission
Refinement method
1364 [R(int) = 0.1032]
99.6 %
1309 [R(int) = 0.0582]
99.3 %
Semi-empirical from equivalents
0.9807 and 0.9807
Full-matrix least-squares on F2
1364/36/91
Semi-empirical from equivalents
0.8567 and 0.8255
Full-matrix least-squares on F2
1309/59/87
Data/restraints/parameters
Goodness-of-fit on F2
Final R indices [I [ 2sigma (I)]
R indices (all data)
1.041
1.100
R1 = 0.0481, wR2 = 0.1081
R1 = 0.1054, wR2 = 0.1367
0.01(17)
R1 = 0.0417, wR2 = 0.1025
R1 = 0.0585, wR2 = 0.1137
0.03(3)
Absolute structure parameter
-3
)
˚
Largest diff. peak and hole/(e.A
0.156 and -0.171
0.322 and -0.220
disorder of cyclohexyl groups. The size of the counter supporting interaction ensures planarity of the guanidine CN3
anion and consequently the efficiency of intermolecular moiety and the hydrogen-bonded halide atoms as illustrated
N/C–HꢀꢀꢀN interactions in the structures allows for differ- by the low values for the C–N–HꢀꢀꢀX torsion angles. These
ent thermal motion of the molecules, most visible by the angles, together with other pertinent inter-atomic distances
thermal ellipsoids of the terminal cyclohexyl rings.
and angles are summarized in Table 3. The C–HꢀꢀꢀX inter-
action(Fig. 2) forms a classicalC–HꢀꢀꢀX contactwith a single
halide atom (Scheme 1; synthon b).
Supramolecular Hydrogen-Bonding Synthons
in [CHGH]?X-; X = Cl, Br
The Extended Structure of 1 and 2. Crystal Packing
The supramolecular hydrogen-bonding synthons (Scheme 1) and Supramolecular Structures
in [CHGH?]X-; X = Cl, Br are shown in Fig. 2. The
structural data for those contacts which are considered to be The 3-D network architecture of both 1 and 2 salts, can be
viable hydrogen-bonds are listed in Table 3. A particularly described in a number of ways. We consider the following
significant feature of the synthons (a and b) shown in Fig. 2 is to be the most appropriate. The crystallographically inde-
the fact that one of the cyclohexyl (1-positioned) C–H pendent CHGH? cations occur in chains, with the X-
˚
hydrogens form weak C–HꢀꢀꢀX contacts [2.767 and 2.887 A anions arranged parallel to the cation chains. The cations
in 1 and 2, respectively] to support the N–HꢀꢀꢀX [2.585 and and anions occur in a threefold array: three anions surround
˚
2.797 A in 1 and 2, respectively] hydrogen-bonds. When each cation (via its three N–HꢀꢀꢀX and C–HꢀꢀꢀX interac-
compared to the N,N0,N00-tricyclohexylguanidinium iodide tions, Fig. 3; Table 3), and three cations surround each
derivative [25], similar features were observed with the anion resulting in the formation of three-dimensional
interactions being with comparable geometrical parameters supramolecular structure. This packing is similar to that
[C/NꢀꢀꢀH distances of 3.027 and 2.856 A, respectively]. This observed in the iodide derivative [25], where The CHGH?
˚
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J Chem Crystallogr (2012) 42:1022–1028
1025
˚
Table 2 Selected geometrical parameters (A,°) for 1 and 2
Bond distances
Bond angles
Compound 1a
N1–C1
N1–C2
C2–C7
C2–C3
C3–C4
C4–C5
C5–C6
C6–C7
Compound 2b
N1–C1
N1–C2
C2–C7
C2–C3
C3–C4
C4–C5
C5–C6
C6–C7
a
1.337 (3)
1.461 (4)
1.519 (5)
1.525 (6)
1.590 (7)
1.542 (8)
1.490 (7)
1.520 (5)
C1–N1–C2
N1–C2–C7
N1i–C1–N1ii
N1i–C1–N1
N1ii–C1–N1
N1–C2–C3
C7–C2–C3
C2–C3–C4
125.6(3)
111.0(3)
119.984(9)
119.991(10)
119.989(10)
110.2(4)
108.3(4)
106.2(5)
1.340(4)
1.463(7)
1.502(8)
1.549(8)
1.571(9)
1.518(9)
1.506(8)
1.525(7)
C1–N1–C2
N1i–C1–N1
N1i–C1–N1ii
N1–C1–N1ii
N1–C2–C7
C2–C3–C4
C5–C4–C3
C6–C5–C4
126.1(4)
119.984(17)
119.986(17)
119.983(17)
110.9(5)
106.3(6)
108.8(6)
110.1(6)
Symmetry codes (i) z ? 1, x - 1, y; (ii)y ? 1, z, x - 1
b
Symmetry codes (i) z ? 1/2, -x ? 1/2, -y; (ii)-y ? 1/2, -z,
x - 1/2
ions occur in chains, with the I- anions arranged parallel to
the cation chains in a threefold array: three anions surround
˚
each cation [via its three N–HꢀꢀꢀI, 2.856 A; (165°) and
˚
C–HꢀꢀꢀI (3.027 A; 158°) interactions, Fig. 2], and three
cations surround each anion. These interactions and the
symmetry related ones in the structures of 1, 2 and the
iodide derivative [25], will result in the three-dimensional
overall packing diagram, Fig. 4, in which tetrameric
[(CHGH?)3X-]4 units translates in the three directions a,
b and c crystallographic axes to form the cubic lattice. In
such arrangement, the cation forms arrays, where the
anions are imprisoned in the cavities, and surrounded by
three cations in a six coordination arrangement, Fig. 5.
The guanidinium CHGH? cations in compounds 1 and 2
display hydrogen bonds to the halide anion through both the
N–H and the 1-position cyclohexyl C–H moieties to form a
supramolecular hydrogen-bonded network to the halide
anions. Although the supramolecular synthonsbased on C–H
donors are longer, and by inference, less strong, than those
based on N–H donors, they are nonetheless, structure
determining. These types of supramolecular synthons have
been observed in other related compounds. The stability of
this crystal lattice is evidenced by the crystallization of a
whole series of isomorphous compounds of this type, in
addition to the title compounds, the derivative N,N0,N00-tri-
cyclohexylguanidinium iodide derivative [25], even with
Fig. 1 Molecular structures of: a [CHGH?]Cl- (1); b [CHGH?]Br-
(2). Thermal ellipsoids drown at the 50 % probability level. Only one
orientation of the disordered cyclohexyl groups is displayed in the
figures
N
H
X
C
H
X
(a)
(b)
Scheme 1 Hydrogen-bonding synthons found in (1) and (2)
different substituents like N,N0,N00-triisopropylguanidinium
chloride [17]. When using another symmetrical derivative,
namely the N,N0,N00-triisopropylguanidinium chloride [17], a
similar highly symmetric lattice is reproduced, while the less
symmetric N,N0-diisopropyl-N00-2,6-dimethylguanidinium
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J Chem Crystallogr (2012) 42:1022–1028
b
0
a
c
Fig. 2 The diagram showing one guanidium cation and three anions
in order to emphasize the orientation of the supramolecular synthon
that results from hydrogen bonding array of three N–HꢀꢀꢀX and three
C–HꢀꢀꢀX interactions. The N/CꢀꢀꢀX distances are shown to aid the
visualization of H-bonding interactions. Similar arrangement is
applied for the iodide derivative (C/NꢀꢀꢀX distances of 3.950 and
Fig. 3 A partial packing diagram of 2, showing the CHGH? cations
and anions occur in a threefold array: three anions surround each
cation and three cations surround each anion. Different molecular
rendering is used to clarify the arrangement
˚
3.694 A, respectively)
˚
Table 3 Hydrogen bond parameters (A, °) for 1 and 2
D–HꢀꢀꢀA
D–H
HꢀꢀꢀA
DꢀꢀꢀA
D–HꢀꢀꢀA
Compound 1a
N1–H1ꢀꢀꢀCl1
C2–H2ꢀꢀꢀCl1i
Compound 2b
N1–H1ꢀꢀꢀBr1i
C2–H2ꢀꢀꢀBr1ii
a
0.94(3)
0.99(4)
2.585
2.767
3.515(4)
3.728(4)
171
164
0.78(4)
0.93(6)
2.797
2.887
3.572(5)
3.800(6)
170
168
Symmetry codes (i) 2 - x, -1/2 ? y, -1/2 ? z
b
Symmetry codes (i) 3/2 - x, 1 - y, -1/2 ? z; (ii)x, -1 ? y,
-1 ? z
chloride or bromide [17] produced a less symmetric lattice as
the cation has reduced symmetry and therefore produces a
less symmetric lattice [17]. Similar concepts apply whenever
less symmetric cations or anions are used [15, 16].
On the other hand, the moderate increase in the size of
the anions and most importantly the retention of spherically
symmetric Cl- and Br- anions did not lead to much change
in space group symmetry. This is consistent with the
arrangement of hydrogen bonding motifs discussed previ-
ously, Fig. 2. This preserved the orientation of the cations
and anions and favors formation of similar space groups.
Fig. 4 Overall packing diagram of 2. Halide ions appear as black
spheres. Similar packing is observed for (1). The first carbon (of the
cyclohexyl group) involved in attraction is presented, the other
omitted for clarity. Hydrogen atoms not involved in hydrogen
bonding deleted for clarity
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J Chem Crystallogr (2012) 42:1022–1028
1027
X = Cl, Br, I and the N,N0,N00-triisopropylguanidinium
chloride, which show the possibility of using
such supramolecular motifs as a crystal engineering
tools.
Supplementary Material
Crystallographic data have been deposited with the Cam-
bridge Crystallographic Data Center, CCDC 865451 &
865452 Copies of this information may be obtained from
the director, CCDC, 12 Union Road, Cambridge CB2 1EZ,
UK. Tel.: ?44 1223 762910; fax: ?44 1223 336 033;
e-mail: deposit@ccdc.cam.ac.uk or on the web www: http//
www.ccdc.cam.ac.uk/deposit.
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Fig. 5 The anion is surrounded by three cations in a six coordination
arrangement (view for 2)
The formation of this high symmetry lattice may be
understood in terms of the spherical shape and size of the
halide anion used in this study, as compared to the other
anionic salts that form the other lower symmetry lattices
[15–17]. Further, the less than spherical symmetry of other
anions will make it very unlikely to fit in such cubic lattice.
Moreover, the 1:1, cation:anion charge ratio in this lattice
type is another factor in the formation of such lattices.
Concluding Remarks
The crystal and molecular structures of the guanidinium
halides, [CHGH?]Cl (1) and [CHGH?]Br (2), have been
determined and compared with the iodide derivative [25]
and those of other derivatives. Some common features are:
1. The compounds [CHGH?]X-; X = Cl, Br, I and the
different substituted N,N0,N00-triisopropylguanidinium
chloride crystallize in cubic crystal structures.
2. Similar hydrogen bonding arrays are observed with
each cation in these structures having two hydro-
gen bonding (classical N–HꢀꢀꢀX and non-classical
C–HꢀꢀꢀX).
3. Each anion in these structures has two hydrogen
bonding and another four symmetrically related ones
in a total six intermolecular interactions leading to a
coordination number of six around each anion.
4. The stability of such lattice is evident by the crystal-
lization of an isomorphous series of [CHGH?]X-;
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