6,6′-Dimeth­oxy-2,2′-[p-phenyl­ene­bis(nitrilo­methyl­idyne)]diphenol chloro­form disolvate

Mohammed H Al-Douh; Hasnah Osman; Shafida Abd Hamid; Reza Kia; Hoong-Kun Fun

doi:10.1107/S1600536809007302

. 2009 Mar 6;65(Pt 4):o680–o681. doi: 10.1107/S1600536809007302

6,6′-Dimethoxy-2,2′-[p-phenylenebis(nitrilomethylidyne)]diphenol chloroform disolvate

Mohammed H Al-Douh ^a, Hasnah Osman ^a,^*,^‡, Shafida Abd Hamid ^b, Reza Kia ^c, Hoong-Kun Fun ^c,^*

PMCID: PMC2969051 PMID: 21582424

Abstract

The title compound, C₂₂H₂₀N₂O₄·2CHCl₃, a new Schiff base compound, lies across a crystallographic inversion centre. An intramolecular O—H⋯N hydrogen bond generates a six-membered ring, producing an S(6) ring motif. Intermolecular bifurcated C—H⋯O hydrogen bonds involving the two O atoms of the Schiff base ligand and the H atom of the chloroform solvent of crystallization, generate an R ² ₁(5) ring motif. The crystal structure is stabilized by intermolecular C—H⋯π and π–π interactions [centroid to centroid distance = 3.6158 (10) Å]. In the crystal structure, molecules are stacked down the c axis.

Related literature

For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For the synthesis and applications of Schiff bases see, for example: Salem & Amer (1995 ▶); Teoh et al. (1997 ▶); Viswanathamurthi et al. (1998 ▶); Cohen et al. (1964 ▶); Kabak et al. (2000 ▶); Parra et al. (2007 ▶); Al-Douh et al. (2006 ▶, 2007 ▶, 2008 ▶); Liu et al. (2006 ▶); Shah et al. (2008 ▶). For the stability of the temperature controller used for the data collection, see: Cosier & Glazer (1986 ▶). For bond-length data, see: Allen et al. (1987 ▶).

Experimental

Crystal data

C₂₂H₂₀N₂O₄·2CHCl₃
M _r = 615.14
Monoclinic,
a = 10.4773 (2) Å
b = 21.3287 (5) Å
c = 6.2424 (2) Å
β = 105.669 (2)°
V = 1343.13 (6) Å³
Z = 2
Mo Kα radiation
μ = 0.67 mm⁻¹
T = 100 K
0.54 × 0.18 × 0.07 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.712, T _max = 0.958
10624 measured reflections
3069 independent reflections
2361 reflections with I > 2σ(I)
R _int = 0.033

Refinement

R[F ² > 2σ(F ²)] = 0.036
wR(F ²) = 0.090
S = 1.03
3069 reflections
165 parameters
H-atom parameters constrained
Δρ_max = 0.35 e Å⁻³
Δρ_min = −0.25 e Å⁻³

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

Supplementary Material

Crystal structure: contains datablocks global, I. DOI: 10.1107/S1600536809007302/at2731sup1.cif

e-65-0o680-sup1.cif^{(17.6KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809007302/at2731Isup2.hkl

e-65-0o680-Isup2.hkl^{(150.6KB, hkl)}

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

Table 1. Hydrogen-bond geometry (Å, °).

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1⋯N1	0.84	1.84	2.584 (2)	147
C12—H12A⋯O1ⁱ	1.00	2.21	3.120 (3)	150
C12—H12A⋯O2ⁱ	1.00	2.30	3.121 (3)	139
C3—H3A⋯Cg1ⁱⁱ	0.95	2.73	3.5221 (19)	142

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Symmetry codes: (i) Inline graphic ; (ii) . Cg1 is the centroid of the C1–C6 benzene ring.

Acknowledgments

We thank the Malaysian Government and Universiti Sains Malaysia for an FRGS grant [304/PKIMIA/638122] to conduct this work. MHAl-D thanks the Yemen Government and Hadhramout University of Science and Technology for financial scholarship support. 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 a post-doctoral research fellowship. HKF also thanks Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/811012.

supplementary crystallographic information

Comment

Bis-Schiff bases are a class of important compounds used as pharmaceutical, medicinal and industrial materials. Schiff bases have also been used extensively in coordination and inorganic chemistry. Salem and Amer used H₂O₂ to study the kinetics of the oxidation of a manganese complex with bis-Schiff base of salicyldehyde (Salem & Amer, 1995). Many of these Schiff bases were found to form suitable inner coordination spheres between tin atom with O and N atoms as quadridentate chelates (Teoh et al., 1997). Meanwhile, ruthenium complexes of bis-Schiff bases derived from o-vanillin and salicyldehyde were shown to exhibit dibasic tetradentate chelation (Viswanathamurthi et al., 1998). The intramolecular hydrogen bonds formed between O and N atoms in Schiff bases are responsible for the formation of these metal complexes (Cohen et al., 1964). Kabak et al. (2000) prepared the derivative of another isomer of the title compound and studied the photochromic conformational properties of this derivative, while Parra et al. (2007) examined the intercalation of another derivative of bis-Schiff bases with DNA by UV spectroscopy. Recently, we reported the crystal structure of the meta-isomer of the title compound (Al-Douh et al., 2007), while the single-crystal of the second isomer in the ortho-position was obtained and the data are consistent with the reported structure (Liu et al., 2006). The proton and carbon NMR spectroscopies of the title compound and its isomers were also studied (Al-Douh et al., 2008). Our group has been actively involved in synthesizing bis-Schiff bases and investigating their DNA binding ability using spectroscopic techniques employing calf thymus DNA (Shah et al., 2008). We have synthesized the third symmetric Schiff base by the condensation of o-vanillin with p-phenylenediamine and its X-ray crystal structure is presented here.

The title compound, (Fig. 1), lies across a crystallographic inversion centre [symmetry code of unlabelled atoms -x + 1, -y, -z + 2]. The bond lengths (Allen et al., 1987) and angles are within normal ranges. An intramolecular O—H···N hydrogen bond generates a six-membered ring, producing S(6) ring motif (Bernstein et al., 1995). Intermolecular bifurcated C—H···O hydrogen bonds involving the two oxygen atoms of the Schiff base ligand and the hydrogen atom of the chloroform solvent of crystallization generate a R²₁(5) ring motif. There are short contacts [C1–C9 = 3.267 (3) and C2–C9 = 3.399 (3) Å] which are shorter than the sum of the van der Waals radius of carbon atom. The crystal structure is stabilized by intermolecular C—H···π interaction (Cg1 is the centroid of the C1–C6 benzene ring) (Table 1) and intermolecular π-π interaction [Cg1···Cg2^{i, ii, iii, iv} = 3.6158 (10) Å; symmetry codes: (i) x, 1/2 - y, 1/2 + z (ii) x, y, -1 + z (iii) 1 - x, -y, 1 - z (iv) x, y, 1 + z, (Cg2 is the centroid of the benzene ring in the middle of the main molecule)]. In the crystal structure molecule are stacked down the c axis (Fig. 2).

Experimental

The synthetic method has been described earlier (Al-Douh et al., 2006, 2007). Single crystals suitable for X-ray diffraction were obtained by slow evaporation of chloroform at room temperature.