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Acta Crystallogr Sect E Struct Rep Online. 2009 May 1; 65(Pt 5): o1071–o1072.
Published online 2009 April 18. doi:  10.1107/S1600536809013804
PMCID: PMC2977751

4-{[3-(4-Hydroxy­benzyl­ideneamino)-2,2-dimethyl­propyl]iminiomethyl}phenolate dihydrate

Abstract

The asymmetric unit of the title compound, C19H22N2O2·2H2O, comprises a zwitterionic form of the Schiff base compound and two water mol­ecules of crystallization. Inter­molecular N—H(...)O, C—H(...)O and O—H(...)N hydrogen bonds involving one of the water mol­ecules in the asymmetric unit generate seven- and eight-membered rings, with R 2 1(7) and R 2 2(8) ring motifs, respectively. The dihedral angle beween the two aromatic rings is 86.5 (2)°. The imino and iminium groups are coplanar with the benzene rings to which they are attached, making dihedral angles (N—C—C—C) of −179.3 (5) and −179.2 (4)°, respectively. Validation software indicates the higher symmetry space group Pnma for this structure. However, this process ignores H atoms and the zwitterionic configuration of the main mol­ecule breaks the higher symmetry. Solution in Pna21 provides a chemically sensible zwitterionic compound with improved residuals. In the crystal structure, mol­ecules are linked together through inter­molecular O—H(...)O, O—H(...)N, N—H(...)O and C—H(...)O inter­actions, forming a three-dimensional network. The crystal structure is further stabilized by inter­molecular C—H(...)π inter­actions.

Related literature

For hydrogen-bond motifs, see: Bernstein et al. (1995 [triangle]). For information on Schiff base ligands and their complexes and applications, see: Calligaris & Randaccio (1987 [triangle]); Li et al. (2005 [triangle]); Bomfim et al. (2005 [triangle]); Glidewell et al. (2005 [triangle], 2006 [triangle]); Sun et al. (2004 [triangle]). For details of the synthesis, see: Fun et al. (2008 [triangle]). For the stability of the temperature controller used for data collection, see: Cosier & Glazer (1986 [triangle]).

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Object name is e-65-o1071-scheme1.jpg

Experimental

Crystal data

  • C19H22N2O2·2H2O
  • M r = 346.42
  • Orthorhombic, An external file that holds a picture, illustration, etc.
Object name is e-65-o1071-efi1.jpg
  • a = 13.0336 (4) Å
  • b = 11.5242 (3) Å
  • c = 12.4132 (4) Å
  • V = 1864.49 (10) Å3
  • Z = 4
  • Mo Kα radiation
  • μ = 0.09 mm−1
  • T = 100 K
  • 0.34 × 0.21 × 0.11 mm

Data collection

  • Bruker SMART APEXII CCD area-detector diffractometer
  • Absorption correction: multi-scan (SADABS; Bruker, 2005 [triangle]) T min = 0.971, T max = 0.991
  • 10183 measured reflections
  • 2237 independent reflections
  • 1753 reflections with I > 2σ(I)
  • R int = 0.056

Refinement

  • R[F 2 > 2σ(F 2)] = 0.047
  • wR(F 2) = 0.116
  • S = 1.05
  • 2237 reflections
  • 235 parameters
  • 3 restraints
  • H atoms treated by a mixture of independent and constrained refinement
  • Δρmax = 0.27 e Å−3
  • Δρmin = −0.20 e Å−3

Data collection: APEX2 (Bruker, 2005 [triangle]); cell refinement: APEX2; data reduction: SAINT (Bruker, 2005 [triangle]); program(s) used to solve structure: SHELXTL (Sheldrick, 2008 [triangle]); program(s) used to refine structure: SHELXTL; molecular graphics: SHELXTL; software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 [triangle]).

Table 1
Hydrogen-bond geometry (Å, °)

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809013804/sj2615sup1.cif

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809013804/sj2615Isup2.hkl

Additional supplementary materials: crystallographic information; 3D view; checkCIF report

Acknowledgments

HKF and RK thank the Malaysian Government and Universiti Sains Malaysia for the Science Fund (grant No. 305/PFIZIK/613312). RK thanks Universiti Sains Malaysia for the award of a postdoctoral research fellowship. HK thanks PNU for financial support. HKF also thanks Universiti Sains Malaysia for Research University Golden Goose Grant No. 1001/PFIZIK/811012.

supplementary crystallographic information

Comment

In the field of coordination chemistry, Schiff base compounds are among the most prevalent and versatile ligands. They have received much attention due to their important roles in the development of coordination chemistry related to catalysis and enzymatic reactions, magnetism, and supramolecular architectures. In comparison to the Schiff base metal complexes, only a relatively small number of free Schiff base ligands have been structurally characterized (Calligaris & Randaccio, 1987). Structures of Schiff bases derived from substituted benzaldehydes have been reported (Li et al., 2005; Bomfim et al., 2005; Glidewell et al., 2005, 2006; Sun et al., 2004).

The asymmetric unit of the title compound, Fig. 1, comprises a zwitterionic Schiff base compound and two water molecules of crystallization. The zwitterion results from protonation of the imine N2 atom with the O2 hydroxy group deprotonated resulting in the formation of iminium and phenolate groups. Intermolecular N—H···O and C—H···O hydrogen bonds involving the O2W O atom as a bifurcated acceptor generate an R21(7) ring motif (Bernstein et al., 1995). Intermolecular N—H···O and O—H···N hydrogen bonds, again involving O2W, generate an R22(8) ring motif. The dihedral angle beween the two phenyl rings is 86.5 (2)°. The imino and iminium groups are coplanar with the benzene rings to which they are attached making dihedral angles of -179.3 (5) and -179.2 (4)° for N1—C7—C6—C5 and N2—C11—C12—C13, respectively. This structure requires differentiating between the Pna21 and Pnma space groups to achieve a correct solution. The solution based on the higher symmetry space group (Pnma) gives a chemically nonsensible polymeric chain as the program PLATON/ADDSYM has not taken into account H atoms in determining the symmetry elements. The solution in Pna21 gives a chemically sensible zwitterionic compound with lower R values. In the crystal structure, the molecules are linked together through intermolecular O—H···O, O—H···N, N—H···O and C—H···O interactions, forming a three-dimensional network (Fig. 2). The crystal structure is further stabilized by intermolecular C—H···π interactions [Cg1 and Cg2 are the centroids of the C1–C6 and C12–C17 benzene rings] (Table 1).

Experimental

The synthetic method has been described earlier (Fun et al., 2008), except that 4-hydroxybenzaldehyde (2 mmol, 244 mg) and 2,2-dimethylpropane diamine (1 mmol, 102 mg) were used. Single crystals suitable for X-ray diffraction were obtained by evaporation of an ethanol solution at room temperature.

Refinement

The H atom of the hydroxy group was located from the difference Fourier map and refined freely. The H atoms of O2W were located from the difference Fourier map and constrained to refine with the carrier atom with Uiso(H) = 1.5Ueq(O) with distance restraint of 0.85 (1) Å. The H atoms of O1W were located from the difference Fourier map and constrained to refine with the carrier atom with Uiso(H) = 1.5Ueq(O). Other N-bound and O-bound H atoms were located from the difference Fourier map and refined freely, see Table 1. The rest of the H atoms were positioned geometrically and refined using a riding model with C—H = 0.93–0.97 Å and Uiso(H) = 1.2Ueq(C). In the absence of sufficient anomalous scattering, 904 Friedel pairs were merged.

Figures

Fig. 1.
The molecular structure of the title compound with atom labels and 50% probability ellipsoids for non-H atoms. Intermolecular interactions involving the O2W water molecule are shown as dashed lines.
Fig. 2.
The crystal packing of the title compound, viewed down the a axis showing three-dimensional network formation through intermolecular interactions, shown as dashed lines.

Crystal data

C19H22N2O2·2H2OF(000) = 744
Mr = 346.42Dx = 1.234 Mg m3
Orthorhombic, Pna21Mo Kα radiation, λ = 0.71073 Å
Hall symbol: P 2c -2nCell parameters from 1477 reflections
a = 13.0336 (4) Åθ = 2.4–29.9°
b = 11.5242 (3) ŵ = 0.09 mm1
c = 12.4132 (4) ÅT = 100 K
V = 1864.49 (10) Å3Block, orange
Z = 40.34 × 0.21 × 0.11 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer2237 independent reflections
Radiation source: fine-focus sealed tube1753 reflections with I > 2σ(I)
graphiteRint = 0.056
[var phi] and ω scansθmax = 27.5°, θmin = 2.4°
Absorption correction: multi-scan (SADABS; Bruker, 2005)h = −15→16
Tmin = 0.971, Tmax = 0.991k = −14→14
10183 measured reflectionsl = −16→7

Refinement

Refinement on F2Primary atom site location: structure-invariant direct methods
Least-squares matrix: fullSecondary atom site location: difference Fourier map
R[F2 > 2σ(F2)] = 0.047Hydrogen site location: inferred from neighbouring sites
wR(F2) = 0.116H atoms treated by a mixture of independent and constrained refinement
S = 1.05w = 1/[σ2(Fo2) + (0.0526P)2 + 0.5548P] where P = (Fo2 + 2Fc2)/3
2237 reflections(Δ/σ)max < 0.001
235 parametersΔρmax = 0.27 e Å3
3 restraintsΔρmin = −0.20 e Å3

Special details

Experimental. The crystal was placed in the cold stream of an Oxford Cyrosystems Cobra open-flow nitrogen cryostat (Cosier & Glazer, 1986) operating at 100.0 (1) K.
Geometry. All esds (except the esd in the dihedral angle between two l.s. planes) are estimated using the full covariance matrix. The cell esds are taken into account individually in the estimation of esds in distances, angles and torsion angles; correlations between esds in cell parameters are only used when they are defined by crystal symmetry. An approximate (isotropic) treatment of cell esds is used for estimating esds 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 > 2sigma(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)

xyzUiso*/Ueq
O10.0498 (3)0.5696 (3)1.0250 (3)0.0254 (8)
O20.0475 (3)0.5792 (3)0.4102 (2)0.0217 (7)
N10.5104 (3)0.5803 (3)0.8323 (3)0.0192 (8)
N20.5136 (3)0.5842 (3)0.5796 (3)0.0186 (8)
C10.2946 (4)0.5328 (4)0.8831 (4)0.0181 (10)
H1A0.32250.48950.82700.022*
C20.1925 (4)0.5165 (4)0.9112 (4)0.0178 (10)
H2A0.15280.46270.87410.021*
C30.1496 (4)0.5802 (4)0.9947 (4)0.0184 (10)
C40.2104 (4)0.6615 (4)1.0498 (4)0.0221 (10)
H4A0.18280.70501.10590.026*
C50.3115 (4)0.6764 (4)1.0197 (4)0.0211 (10)
H5A0.35100.73101.05600.025*
C60.3563 (4)0.6130 (4)0.9374 (4)0.0181 (10)
C70.4645 (4)0.6339 (4)0.9073 (4)0.0186 (10)
H7A0.50100.68960.94570.022*
C80.6178 (4)0.6143 (4)0.8131 (4)0.0172 (9)
H8A0.65940.54470.80920.021*
H8B0.64160.65930.87420.021*
C90.63477 (18)0.6854 (2)0.7101 (5)0.0166 (5)
C100.6196 (4)0.6143 (4)0.6059 (4)0.0207 (10)
H10A0.64810.65800.54630.025*
H10B0.65880.54310.61220.025*
C110.4577 (4)0.6396 (3)0.5096 (3)0.0173 (9)
H11A0.48910.70090.47370.021*
C120.3548 (4)0.6168 (4)0.4823 (4)0.0160 (9)
C130.3087 (4)0.6874 (4)0.4023 (4)0.0186 (10)
H13A0.34760.74320.36680.022*
C140.2061 (4)0.6736 (4)0.3767 (4)0.0183 (9)
H14A0.17680.72060.32410.022*
C150.1448 (4)0.5894 (4)0.4291 (4)0.0172 (9)
C160.1949 (4)0.5154 (3)0.5056 (4)0.0182 (10)
H16A0.15740.45640.53820.022*
C170.2949 (4)0.5287 (3)0.5318 (4)0.0181 (10)
H17A0.32460.47980.58260.022*
C180.56782 (19)0.7944 (2)0.7087 (5)0.0209 (6)
H18A0.57700.83640.77480.031*
H18B0.49710.77250.70140.031*
H18C0.58730.84260.64910.031*
C190.74958 (18)0.7180 (2)0.7099 (6)0.0230 (6)
H19A0.76590.75900.77500.034*
H19B0.76400.76660.64900.034*
H19C0.79030.64870.70570.034*
O1W0.02979 (14)0.33777 (16)0.7189 (3)0.0223 (5)
H1W10.00210.37540.65920.033*
H2W10.00120.37130.77310.033*
O2W0.45692 (15)0.38775 (16)0.7030 (3)0.0247 (5)
H1W20.49220.32790.69160.037*
H2W20.47350.40560.76810.037*
H1N20.487 (3)0.520 (3)0.618 (3)0.020 (9)*
H1O10.020 (3)0.524 (4)0.984 (4)0.040 (14)*

Atomic displacement parameters (Å2)

U11U22U33U12U13U23
O10.0152 (16)0.0329 (16)0.0281 (17)−0.0051 (14)0.0031 (13)−0.0086 (14)
O20.0171 (16)0.0261 (15)0.0219 (16)−0.0001 (13)−0.0042 (13)0.0062 (12)
N10.020 (2)0.0172 (18)0.0207 (18)−0.0025 (17)0.0044 (15)0.0045 (16)
N20.0145 (19)0.0181 (18)0.0231 (19)−0.0025 (16)0.0018 (15)−0.0003 (15)
C10.019 (2)0.019 (2)0.016 (2)0.001 (2)0.0061 (19)0.0063 (18)
C20.018 (3)0.020 (2)0.015 (2)−0.0032 (19)−0.0010 (19)0.0004 (17)
C30.012 (2)0.0189 (19)0.025 (2)−0.0004 (17)0.0006 (17)0.0025 (18)
C40.022 (2)0.0227 (19)0.022 (2)0.0024 (19)0.0011 (19)−0.0022 (18)
C50.026 (3)0.0182 (18)0.019 (2)−0.0060 (19)−0.004 (2)0.0028 (18)
C60.021 (2)0.0139 (18)0.019 (2)0.0006 (19)0.0014 (18)0.0042 (19)
C70.0090 (19)0.024 (2)0.023 (2)−0.0051 (17)−0.0087 (18)0.0076 (18)
C80.010 (2)0.017 (2)0.025 (2)0.0022 (19)−0.0017 (18)0.004 (2)
C90.0150 (11)0.0190 (11)0.0157 (13)−0.0035 (10)0.002 (2)−0.004 (2)
C100.021 (2)0.025 (2)0.016 (2)−0.004 (2)−0.0033 (19)0.000 (2)
C110.029 (2)0.0100 (16)0.013 (2)0.0029 (18)−0.0015 (18)−0.0009 (15)
C120.012 (2)0.0166 (18)0.020 (2)0.0025 (18)0.0026 (17)−0.0080 (19)
C130.018 (2)0.0142 (17)0.024 (2)−0.0012 (17)0.0025 (19)0.0039 (17)
C140.023 (2)0.0161 (18)0.016 (2)0.0023 (18)0.0008 (19)0.0027 (17)
C150.021 (2)0.0144 (16)0.017 (2)0.0029 (18)−0.0014 (18)−0.0027 (17)
C160.018 (3)0.0117 (18)0.025 (3)0.0003 (18)0.0044 (19)0.0002 (18)
C170.021 (2)0.0116 (17)0.022 (2)0.0041 (18)0.0054 (19)0.0051 (18)
C180.0220 (12)0.0170 (12)0.0238 (15)−0.0011 (10)−0.001 (3)−0.006 (2)
C190.0181 (12)0.0244 (13)0.0265 (16)−0.0061 (11)0.002 (3)0.001 (3)
O1W0.0244 (10)0.0209 (9)0.0216 (13)0.0046 (8)−0.0003 (16)−0.0010 (13)
O2W0.0286 (11)0.0201 (9)0.0255 (14)0.0002 (8)−0.0010 (18)−0.0041 (16)

Geometric parameters (Å, °)

O1—C31.359 (6)C9—C101.543 (7)
O1—H1O10.83 (4)C10—H10A0.9700
O2—C151.295 (6)C10—H10B0.9700
N1—C71.267 (6)C11—C121.407 (7)
N1—C81.473 (6)C11—H11A0.9300
N2—C111.302 (6)C12—C131.418 (6)
N2—C101.461 (6)C12—C171.421 (6)
N2—H1N20.95 (4)C13—C141.384 (8)
C1—C21.388 (7)C13—H13A0.9300
C1—C61.398 (7)C14—C151.415 (7)
C1—H1A0.9300C14—H14A0.9300
C2—C31.387 (6)C15—C161.434 (6)
C2—H2A0.9300C16—C171.352 (7)
C3—C41.405 (7)C16—H16A0.9300
C4—C51.380 (8)C17—H17A0.9300
C4—H4A0.9300C18—H18A0.9600
C5—C61.385 (7)C18—H18B0.9600
C5—H5A0.9300C18—H18C0.9600
C6—C71.480 (6)C19—H19A0.9600
C7—H7A0.9300C19—H19B0.9600
C8—C91.535 (7)C19—H19C0.9600
C8—H8A0.9700O1W—H1W10.9309
C8—H8B0.9700O1W—H2W10.8614
C9—C181.529 (3)O2W—H1W20.8404
C9—C191.543 (3)O2W—H2W20.8612
C3—O1—H1O1110 (4)C9—C10—H10A108.3
C7—N1—C8115.9 (4)N2—C10—H10B108.3
C11—N2—C10124.2 (4)C9—C10—H10B108.3
C11—N2—H1N2121 (2)H10A—C10—H10B107.4
C10—N2—H1N2115 (2)N2—C11—C12127.0 (4)
C2—C1—C6121.3 (4)N2—C11—H11A116.5
C2—C1—H1A119.4C12—C11—H11A116.5
C6—C1—H1A119.4C11—C12—C13117.7 (4)
C3—C2—C1120.2 (4)C11—C12—C17123.6 (4)
C3—C2—H2A119.9C13—C12—C17118.7 (4)
C1—C2—H2A119.9C14—C13—C12120.3 (4)
O1—C3—C2123.0 (4)C14—C13—H13A119.8
O1—C3—C4117.7 (4)C12—C13—H13A119.8
C2—C3—C4119.3 (4)C13—C14—C15121.3 (4)
C5—C4—C3119.3 (5)C13—C14—H14A119.4
C5—C4—H4A120.3C15—C14—H14A119.4
C3—C4—H4A120.3O2—C15—C14122.1 (4)
C4—C5—C6122.4 (4)O2—C15—C16120.8 (4)
C4—C5—H5A118.8C14—C15—C16117.1 (4)
C6—C5—H5A118.8C17—C16—C15122.0 (4)
C5—C6—C1117.5 (4)C17—C16—H16A119.0
C5—C6—C7120.1 (4)C15—C16—H16A119.0
C1—C6—C7122.3 (4)C16—C17—C12120.5 (4)
N1—C7—C6123.8 (4)C16—C17—H17A119.8
N1—C7—H7A118.1C12—C17—H17A119.8
C6—C7—H7A118.1C9—C18—H18A109.5
N1—C8—C9114.5 (3)C9—C18—H18B109.5
N1—C8—H8A108.6H18A—C18—H18B109.5
C9—C8—H8A108.6C9—C18—H18C109.5
N1—C8—H8B108.6H18A—C18—H18C109.5
C9—C8—H8B108.6H18B—C18—H18C109.5
H8A—C8—H8B107.6C9—C19—H19A109.5
C18—C9—C8111.4 (4)C9—C19—H19B109.5
C18—C9—C19110.7 (2)H19A—C19—H19B109.5
C8—C9—C19105.7 (4)C9—C19—H19C109.5
C18—C9—C10110.7 (4)H19A—C19—H19C109.5
C8—C9—C10113.3 (2)H19B—C19—H19C109.5
C19—C9—C10104.6 (4)H1W1—O1W—H2W1104.2
N2—C10—C9115.8 (4)H1W2—O2W—H2W2102.5
N2—C10—H10A108.3
C6—C1—C2—C3−0.1 (7)C11—N2—C10—C999.7 (5)
C1—C2—C3—O1178.9 (4)C18—C9—C10—N2−53.5 (5)
C1—C2—C3—C40.4 (7)C8—C9—C10—N272.5 (4)
O1—C3—C4—C5−178.6 (4)C19—C9—C10—N2−172.8 (4)
C2—C3—C4—C50.0 (7)C10—N2—C11—C12−178.4 (4)
C3—C4—C5—C6−0.7 (7)N2—C11—C12—C13−179.2 (4)
C4—C5—C6—C10.9 (7)N2—C11—C12—C171.9 (7)
C4—C5—C6—C7179.0 (4)C11—C12—C13—C14−176.2 (4)
C2—C1—C6—C5−0.6 (7)C17—C12—C13—C142.8 (7)
C2—C1—C6—C7−178.6 (4)C12—C13—C14—C15−0.1 (7)
C8—N1—C7—C6179.1 (4)C13—C14—C15—O2176.4 (4)
C5—C6—C7—N1−179.3 (4)C13—C14—C15—C16−3.1 (7)
C1—C6—C7—N1−1.3 (7)O2—C15—C16—C17−175.9 (5)
C7—N1—C8—C9−106.9 (4)C14—C15—C16—C173.6 (7)
N1—C8—C9—C1856.0 (4)C15—C16—C17—C12−1.0 (7)
N1—C8—C9—C19176.4 (4)C11—C12—C17—C16176.6 (4)
N1—C8—C9—C10−69.6 (4)C13—C12—C17—C16−2.3 (7)

Hydrogen-bond geometry (Å, °)

D—H···AD—HH···AD···AD—H···A
O1W—H1W1···O1i0.931.912.830 (5)171
O1W—H2W1···O2ii0.861.902.751 (4)168
O2W—H1W2···O1Wiii0.842.002.774 (3)153
O2W—H2W2···N10.862.222.826 (4)127
N2—H1N2···O2W0.95 (4)1.90 (4)2.832 (4)170 (3)
O1—H1O1···O2ii0.83 (4)1.74 (5)2.565 (5)174 (5)
C17—H17A···O2W0.932.523.408 (6)161
C10—H10B···Cg1iv0.972.693.422 (5)133
C8—H8A···Cg2v0.972.743.497 (5)136

Symmetry codes: (i) −x, −y+1, z−1/2; (ii) −x, −y+1, z+1/2; (iii) x+1/2, −y+1/2, z; (iv) −x+1, −y+1, z−1/2; (v) −x+1, −y+1, z+1/2.

Footnotes

Supplementary data and figures for this paper are available from the IUCr electronic archives (Reference: SJ2615).

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