A second tricilinc polymorph of 6,6′-dieth­oxy-2,2′-[propane-1,2-diylbis(nitrilo­methyl­idyne)]diphenol

Hoong-Kun Fun; Reza Kia; Hadi Kargar; Arezoo Jamshidvand

doi:10.1107/S1600536809008137

. 2009 Mar 11;65(Pt 4):o722–o723. doi: 10.1107/S1600536809008137

A second tricilinc polymorph of 6,6′-diethoxy-2,2′-[propane-1,2-diylbis(nitrilomethylidyne)]diphenol

Hoong-Kun Fun ^a,^*, Reza Kia ^a,^‡, Hadi Kargar ^b, Arezoo Jamshidvand ^b

PMCID: PMC2968989 PMID: 21582458

Abstract

The title Schiff base compound, C₂₁H₂₆N₂O₄, is a second triclinic polymorph of a previously reported room-temperature structure [Jia (2009 ▶). Acta Cryst. E65, o646]. Strong intramolecular O—H⋯N hydrogen bonds generate S(6) ring motifs. Intermolecular C—H⋯O interactions link neighbouring molecules into dimers with an R ₂ ²(16) ring motif. The mean planes of the two benzene rings are almost perpendicular to each other, making a dihedral angle of 88.24 (5)°. An interesting feature of the crystal structure is the intermolecular short C⋯O [3.1878 (13) Å] contact which is shorter than the sum of the van der Waals radii of the relevant atoms. The crystal structure is further stabilized by intermolecular C—H⋯π and π–π interactions [centroid–centroid distance = 3.7414 (6) Å]. The structure has a stereogenic centre but the space group is centrosymmetric, so the molecule exists as a racemate.

Related literature

For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶). For information on Schiff base ligands, complexes and their applications, see: Calligaris & Randaccio (1987 ▶). For the other polymorph, see: Jia, (2009 ▶). For related structures, see: Li et al. (2005 ▶); Bomfim et al. (2005 ▶); Glidewell et al. (2005, 2006 ▶); Sun et al. (2004 ▶); Fun et al. (2008 ▶). For bond-length data, see: Allen et al. (1987 ▶). For stability of the temperature controller used for data collection, see: Cosier & Glazer (1986 ▶).

Experimental

Crystal data

C₂₁H₂₆N₂O₄
M _r = 370.44
Triclinic,
a = 8.9729 (2) Å
b = 10.7008 (4) Å
c = 11.3633 (2) Å
α = 107.432 (1)°
β = 108.487 (1)°
γ = 95.979 (1)°
V = 963.03 (5) Å³
Z = 2
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 100 K
0.56 × 0.27 × 0.25 mm

Data collection

Bruker SMART APEXII CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Bruker, 2005 ▶) T _min = 0.952, T _max = 0.978
19581 measured reflections
5527 independent reflections
4721 reflections with I > 2σ(I)
R _int = 0.026

Refinement

R[F ² > 2σ(F ²)] = 0.045
wR(F ²) = 0.136
S = 1.05
5527 reflections
249 parameters
H-atom parameters constrained
Δρ_max = 0.53 e Å⁻³
Δρ_min = −0.23 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/S1600536809008137/at2736sup1.cif

e-65-0o722-sup1.cif^{(21.7KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536809008137/at2736Isup2.hkl

e-65-0o722-Isup2.hkl^{(270.6KB, 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	1.83	2.5752 (13)	146
O2—H2⋯N2	0.84	1.88	2.6178 (13)	147
C9—H9A⋯O1ⁱ	0.99	2.49	3.4293 (14)	159
C18—H18b⋯Cg1ⁱⁱ	0.99	2.98	3.8340 (12)	142
C7—H7A⋯Cg2ⁱⁱⁱ	0.96	2.72	3.5554 (12)	176

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) . Cg1 and Cg2 are the centroids of the C1–C6 and C11–C16 benzene rings, respectively.

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 a post-doctoral research fellowship. HK and AJ thank PNU for partial financial support. HKF also thanks Universiti Sains Malaysia for the Research University Golden Goose grant No. 1001/PFIZIK/ 811012.

supplementary crystallographic information

Comment

Schiff bases are one of the most prevalent mixed-donor ligands in the field of coordination chemistry. They play an important role in the development of coordination chemistry related to catalysis and enzymatic reactions, magnetism, and supramolecular architectures (Calligaris & Randaccio, 1987). Structures of Schiff bases derived from substituted benzaldehydes and closely related to the title compound have been reported earlier (Li et al., 2005; Bomfim et al., 2005; Glidewell et al., 2006; Sun et al., 2004; Fun et al., 2008).

The molecule of the title compound (Fig. 1), is a potentially tetradentate Schiff base ligand. The bond lengths (Allen et al., 1987) and angles are comparable to the earlier room-temperature polymorph which was published previously (Jia, 2009). Strong intramolecular O—H···N hydrogen bonds generate S(6) ring motifs (Bernstein et al., 1995). Intermolecular C—H···O interactions link neighbouring molecules into dimers with a R₂²(16) ring motif (Bernstein et al., 1995). The mean planes of the two benzene rings are almost perpendicular to each other making a dihedral angle of 88.24 (5)°. The interesting feature of the crystal structure is the short C18···O2 [3.1878 (13) Å, symmetry code: 1 - x, 1 - y, 1 - z] contact which is shorter than the sum of the van der Waals radii of the relevant atoms. The crystal structure, is further stabilizd by intermolecular C—H···π and π-π interactions [centroid to centroid distance of 3.7414 (6) Å]. The structure has a stereogenic centre but the space group is centrosymmetric, so the molecule exists as racemate.

Experimental

The synthetic method has been described earlier (Fun et al., 2008), except that 3-ethoxy salicylaldehyde and 2-methyl-2,3-propanediamine were used as starting materials. Single crystals suitable for X-ray diffraction were obtained by evaporation of an ethanol solution at room temperature.