supplementary materials


qm2085 scheme

Acta Cryst. (2012). E68, o3083    [ doi:10.1107/S1600536812041219 ]

4-Methoxybenzamidinium chloride monohydrate

S. Irrera and G. Portalone

Abstract top

In the cation of the title compound, C8H11N2O+·Cl-·H2O, the C-N bonds of the amidinium group are identical within experiemental error [1.305 (2) and 1.304 (2) Å], and its plane forms a dihedral angle of 25.83 (8)° with the phenyl ring. The ionic components are associated in the crystal into polymeric hydrogen-bonded supramolecular tapes stabilized by N-H+...Cl- and N-H+...Ow intermolecular hydrogen bonds, and by Ow-H...Cl- interactions.

Comment top

This Laboratory is currently engaged in systematic structural analysis of proton-transfer adducts containing molecules of biological interest (Portalone, 2011a; Portalone & Irrera, 2011). In this context benzamidine derivatives, which have shown strong biological and pharmacological activity (Powers & Harper, 1999; Grzesiak et al., 2000), are being used in our group as bricks for supramolecular construction (Portalone, 2010, 2011b, 2012). Indeed, these molecules are strong Lewis bases and their cations can be easily anchored onto numerous inorganic and organic anions and polyanions, largely because of the presence of four potential donor sites for hydrogen-bonding. Benzamidinium ions have also been included in a number of protein structures (Marquart et al., 1983; Sprang et al., 1987; Bode et al., 1990).

The asymmetric unit of (I) comprises one non-planar 4-methoxybenzamidinium cation, one chloride anion and one water molecule of crystallization (Fig. 1).

In the cation the amidinium group forms a dihedral angle of 25.83 (8)° with the mean plane of the phenyl ring, which agrees with the values observed in protonated benzamidinium ions (23.2 - 30.4°, Portalone, 2010, 2012). The lack of planarity in all these systems is obviously caused by steric hindrances between the H atoms of the aromatic ring and the amidine moiety. This conformation is rather common in benzamidinium-containing small-molecule crystal structures, with the exception of benzamidinium diliturate, where the benzamidinium cation is planar (Portalone, 2010). The pattern of bond lengths and bond angles of the 4-methoxybenzamidinium cation agrees with that reported in previous structural investigations (Portalone, 2010, 2012). In particular the amidinium group, true to one's expectations, features similar C—N bonds [1.305 (2) and 1.304 (2) Å], evidencing the delocalization of the π electrons and their double-bond character.

Analysis of the crystal packing of (I), (Fig. 2), shows that the ions are associated in the crystal by six distinct N—H+···Cl-, N—H+···Ow and Ow—H···Cl- intermolecular hydrogen bonds (Table 1). Each amidinium unit is bound to two chloride anions by three weak hydrogen bonds (N+···Cl- = 3.185 (2) - 3.552 (2) Å) and to one water molecule by one N—H+···Ow interaction, just forming two R35(10) and one R12(6) supramolecular synthons (Bernstein et al., 1995). Both of these R35(10) and R12(6) motifs lead to the formation of one dimensional polymeric hydrogen-bonded supramolecular tapes approximately along the crystallographic b axis. The water molecule, which plays a dual role as both donor and acceptor in hydrogen bonding interactions, acts as a bridge between tapes through the remaining two Ow—H···Cl- intermolecular interactions.

Related literature top

For the biological and pharmacological relevance of benzamidine, see: Marquart et al. (1983); Sprang et al. (1987); Bode et al. (1990); Powers & Harper (1999); Grzesiak et al. (2000). For structural analysis of proton-transfer adducts containing molecules of biological interest, see: Portalone (2011a); Portalone & Irrera (2011). For the supramolecular association in proton-transfer adducts containing benzamidinium cations, see; Portalone (2010, 2011b, 2012). For hydrogen-bond motifs, see: Bernstein et al. (1995).

Experimental top

4-methoxybenzamidine (1 mmol, Fluka at 96% purity) was dissolved without further purification in 6 ml of hot water and heated under reflux for 3 h. While stirring, HCl (6 mol L-1) was added dropwise until the pH reached 2. After cooling the solution to ambient temperature, colourless crystals suitable for single-crystal X-ray diffraction were grown by slow evaporation of the solvent over two weeks.

Refinement top

All H atoms were identified in difference Fourier maps, but for refinement all C-bound H atoms were placed in calculated positions, with C—H = 0.93 Å (phenyl) and 0.96 Å (methyl), and refined as riding on their carrier atoms. The Uiso values were kept equal to 1.2Ueq(C, phenyl). and to 1.5Ueq(C, methyl). Positional and thermal parameters of H atoms of the amidinium group and of water molecule were freely refined, giving N—H distances in the range 0.75 (2) - 0.96 (2) Å and O—H distances in the range 0.82 (3) - 0.87 (2) Å

Computing details top

Data collection: CrysAlis CCD (Oxford Diffraction, 2006); cell refinement: CrysAlis CCD (Oxford Diffraction, 2006); data reduction: CrysAlis RED (Oxford Diffraction, 2006); program(s) used to solve structure: SIR97 (Altomare et al., 1999); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: WinGX (Farrugia, 1999).

Figures top
[Figure 1] Fig. 1. The asymmetric unit of (I), showing the atom-labelling scheme. Displacements ellipsoids are at the 50% probability level. H atoms are shown as small spheres of arbitrary radii.
[Figure 2] Fig. 2. Crystal packing diagram for (I), viewed approximately down a. Displacements ellipsoids are at the 50% probability level. H atoms are shown as small spheres of arbitrary radii. For the sake of clarity, H atoms not involved in hydrogen bonding have been omitted. Hydrogen bonding is indicated by dashed lines.
4-Methoxybenzamidinium chloride monohydrate top
Crystal data top
C8H11N2O+·Cl·H2OF(000) = 432
Mr = 204.65Dx = 1.311 Mg m3
Monoclinic, P21/cMo Kα radiation, λ = 0.71069 Å
Hall symbol: -P 2ybcCell parameters from 3182 reflections
a = 11.3029 (7) Åθ = 2.8–32.2°
b = 9.3142 (5) ŵ = 0.34 mm1
c = 9.9983 (6) ÅT = 298 K
β = 99.820 (6)°Tablets, colourless
V = 1037.17 (11) Å30.30 × 0.27 × 0.25 mm
Z = 4
Data collection top
Oxford Diffraction Xcalibur S CCD
diffractometer
2989 independent reflections
Radiation source: Enhance (Mo) X-ray Source1947 reflections with I > 2σ(I)
Graphite monochromatorRint = 0.018
Detector resolution: 16.0696 pixels mm-1θmax = 30.0°, θmin = 2.9°
ω and φ scansh = 1513
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2006)
k = 1313
Tmin = 0.905, Tmax = 0.968l = 1414
7158 measured reflections
Refinement top
Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.043Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.113H atoms treated by a mixture of independent and constrained refinement
S = 0.97 w = 1/[σ2(Fo2) + (0.0667P)2]
where P = (Fo2 + 2Fc2)/3
2989 reflections(Δ/σ)max < 0.001
144 parametersΔρmax = 0.22 e Å3
0 restraintsΔρmin = 0.15 e Å3
Crystal data top
C8H11N2O+·Cl·H2OV = 1037.17 (11) Å3
Mr = 204.65Z = 4
Monoclinic, P21/cMo Kα radiation
a = 11.3029 (7) ŵ = 0.34 mm1
b = 9.3142 (5) ÅT = 298 K
c = 9.9983 (6) Å0.30 × 0.27 × 0.25 mm
β = 99.820 (6)°
Data collection top
Oxford Diffraction Xcalibur S CCD
diffractometer
2989 independent reflections
Absorption correction: multi-scan
(CrysAlis RED; Oxford Diffraction, 2006)
1947 reflections with I > 2σ(I)
Tmin = 0.905, Tmax = 0.968Rint = 0.018
7158 measured reflectionsθmax = 30.0°
Refinement top
R[F2 > 2σ(F2)] = 0.043H atoms treated by a mixture of independent and constrained refinement
wR(F2) = 0.113Δρmax = 0.22 e Å3
S = 0.97Δρmin = 0.15 e Å3
2989 reflectionsAbsolute structure: ?
144 parametersFlack parameter: ?
0 restraintsRogers parameter: ?
Special details top

Geometry. All s.u.'s (except the s.u. in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell s.u.'s are taken into account individually in the estimation of s.u.'s in distances, angles and torsion angles; correlations between s.u.'s in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell s.u.'s is used for estimating s.u.'s involving l.s. planes.

Refinement. Refinement of F2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F2, conventional R-factors R are based on F, with F set to zero for negative F2. The threshold expression of F2 > 2σ(F2) is used only for calculating R-factors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F2 are statistically about twice as large as those based on F, and R- factors based on ALL data will be even larger.

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Å2) top
xyzUiso*/Ueq
Cl10.59874 (3)0.29686 (5)0.19860 (4)0.06143 (17)
O10.02187 (9)0.02872 (12)0.72746 (11)0.0585 (3)
N10.37553 (14)0.36637 (18)0.40096 (17)0.0577 (4)
H1A0.4215 (18)0.391 (3)0.351 (2)0.087 (7)*
H1B0.3457 (16)0.424 (2)0.4357 (19)0.070 (7)*
N20.40806 (13)0.1372 (2)0.34687 (16)0.0609 (4)
H2A0.4716 (18)0.167 (2)0.300 (2)0.082 (6)*
H2B0.3898 (16)0.052 (3)0.3475 (19)0.077 (7)*
C10.26509 (11)0.18152 (15)0.49586 (13)0.0400 (3)
C20.17291 (12)0.26955 (17)0.52024 (16)0.0499 (4)
H20.16690.36200.48470.060*
C30.08913 (12)0.22277 (17)0.59666 (16)0.0497 (4)
H30.02730.28320.61200.060*
C40.09816 (11)0.08562 (16)0.64994 (14)0.0425 (3)
C50.19078 (12)0.00346 (17)0.62752 (15)0.0489 (4)
H50.19740.09530.66450.059*
C60.27322 (12)0.04365 (16)0.55054 (14)0.0460 (3)
H60.33480.01710.53500.055*
C70.35238 (11)0.22994 (17)0.41160 (14)0.0460 (4)
C80.07725 (14)0.1140 (2)0.75071 (19)0.0684 (5)
H8A0.0482 (3)0.2006 (11)0.7969 (13)0.103*
H8B0.1241 (9)0.0612 (8)0.8055 (12)0.103*
H8C0.1263 (8)0.1375 (12)0.6654 (9)0.103*
O2W0.27853 (14)0.61140 (16)0.50438 (18)0.0783 (4)
HWA0.319 (3)0.631 (4)0.579 (3)0.155 (14)*
HWB0.3124 (17)0.667 (2)0.452 (2)0.077 (6)*
Atomic displacement parameters (Å2) top
U11U22U33U12U13U23
Cl10.0604 (3)0.0699 (3)0.0594 (3)0.00364 (19)0.02536 (19)0.0085 (2)
O10.0518 (6)0.0581 (7)0.0737 (7)0.0039 (5)0.0337 (5)0.0110 (6)
N10.0595 (8)0.0550 (9)0.0642 (9)0.0047 (7)0.0267 (7)0.0125 (8)
N20.0583 (8)0.0688 (11)0.0628 (9)0.0090 (8)0.0311 (7)0.0027 (8)
C10.0358 (6)0.0472 (8)0.0373 (7)0.0039 (6)0.0072 (5)0.0001 (6)
C20.0510 (8)0.0403 (8)0.0604 (9)0.0036 (6)0.0156 (7)0.0089 (7)
C30.0437 (7)0.0463 (9)0.0629 (9)0.0077 (6)0.0195 (6)0.0020 (7)
C40.0384 (6)0.0464 (8)0.0443 (7)0.0017 (6)0.0117 (5)0.0002 (6)
C50.0496 (7)0.0421 (8)0.0584 (9)0.0047 (7)0.0191 (6)0.0082 (7)
C60.0420 (7)0.0449 (8)0.0541 (8)0.0078 (6)0.0167 (6)0.0032 (7)
C70.0405 (7)0.0559 (10)0.0420 (7)0.0040 (6)0.0084 (6)0.0045 (7)
C80.0503 (8)0.0838 (13)0.0787 (12)0.0101 (8)0.0329 (8)0.0039 (10)
O2W0.1035 (11)0.0605 (8)0.0747 (10)0.0175 (8)0.0258 (9)0.0015 (7)
Geometric parameters (Å, º) top
O1—C41.3613 (16)C2—H20.9300
O1—C81.4243 (18)C3—C41.381 (2)
N1—C71.305 (2)C3—H30.9300
N1—H1A0.81 (2)C4—C51.3837 (19)
N1—H1B0.75 (2)C5—C61.3776 (19)
N2—C71.304 (2)C5—H50.9300
N2—H2A0.96 (2)C6—H60.9300
N2—H2B0.82 (2)C8—H8A0.9596
C1—C21.3798 (19)C8—H8B0.9596
C1—C61.3926 (19)C8—H8C0.9596
C1—C71.4731 (18)O2W—HWA0.82 (3)
C2—C31.385 (2)O2W—HWB0.87 (2)
C4—O1—C8117.92 (13)C3—C4—C5120.02 (12)
C7—N1—H1A119.0 (17)C6—C5—C4120.14 (14)
C7—N1—H1B123.3 (15)C6—C5—H5119.9
H1A—N1—H1B118 (2)C4—C5—H5119.9
C7—N2—H2A120.7 (11)C5—C6—C1120.49 (12)
C7—N2—H2B119.6 (14)C5—C6—H6119.8
H2A—N2—H2B119.7 (18)C1—C6—H6119.8
C2—C1—C6118.68 (12)N2—C7—N1118.95 (15)
C2—C1—C7121.24 (13)N2—C7—C1120.53 (15)
C6—C1—C7120.07 (12)N1—C7—C1120.52 (15)
C1—C2—C3121.24 (14)O1—C8—H8A109.5
C1—C2—H2119.4O1—C8—H8B109.5
C3—C2—H2119.4H8A—C8—H8B109.5
C4—C3—C2119.43 (13)O1—C8—H8C109.5
C4—C3—H3120.3H8A—C8—H8C109.5
C2—C3—H3120.3H8B—C8—H8C109.5
O1—C4—C3124.57 (12)HWA—O2W—HWB100 (3)
O1—C4—C5115.41 (13)
C6—C1—C2—C30.4 (2)C3—C4—C5—C60.9 (2)
C7—C1—C2—C3178.39 (14)C4—C5—C6—C10.7 (2)
C1—C2—C3—C40.2 (2)C2—C1—C6—C50.1 (2)
C8—O1—C4—C32.8 (2)C7—C1—C6—C5178.88 (14)
C8—O1—C4—C5178.22 (14)C2—C1—C7—N2153.81 (15)
C2—C3—C4—O1179.33 (14)C6—C1—C7—N225.0 (2)
C2—C3—C4—C50.4 (2)C2—C1—C7—N126.4 (2)
O1—C4—C5—C6179.90 (14)C6—C1—C7—N1154.78 (15)
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···Cl10.81 (2)2.85 (2)3.5523 (18)145 (2)
N1—H1B···O2W0.75 (2)2.06 (2)2.805 (2)168 (2)
N2—H2A···Cl10.96 (2)2.25 (2)3.1850 (16)164.4 (16)
N2—H2B···Cl1i0.82 (2)2.43 (2)3.201 (2)157.5 (18)
O2W—HWA···Cl1ii0.82 (3)2.36 (3)3.1731 (18)170 (3)
O2W—HWB···Cl1iii0.87 (2)2.29 (2)3.1603 (17)174.8 (19)
Symmetry codes: (i) x+1, y1/2, z+1/2; (ii) x+1, y+1, z+1; (iii) x+1, y+1/2, z+1/2.
Hydrogen-bond geometry (Å, º) top
D—H···AD—HH···AD···AD—H···A
N1—H1A···Cl10.81 (2)2.85 (2)3.5523 (18)145 (2)
N1—H1B···O2W0.75 (2)2.06 (2)2.805 (2)168 (2)
N2—H2A···Cl10.96 (2)2.25 (2)3.1850 (16)164.4 (16)
N2—H2B···Cl1i0.82 (2)2.43 (2)3.201 (2)157.5 (18)
O2W—HWA···Cl1ii0.82 (3)2.36 (3)3.1731 (18)170 (3)
O2W—HWB···Cl1iii0.87 (2)2.29 (2)3.1603 (17)174.8 (19)
Symmetry codes: (i) x+1, y1/2, z+1/2; (ii) x+1, y+1, z+1; (iii) x+1, y+1/2, z+1/2.
references
References top

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