(E)-2-{[2-(2-Hy­droxy­ethyl­amino)­ethyl­imino]­meth­yl}phenol

Juan M Germán-Acacio; Hugo Tlahuext; Herbert Höpfl

doi:10.1107/S1600536811039997

. 2011 Oct 5;67(Pt 11):o2849. doi: 10.1107/S1600536811039997

(E)-2-{[2-(2-Hydroxyethylamino)ethylimino]methyl}phenol

Juan M Germán-Acacio ^a, Hugo Tlahuext ^a, Herbert Höpfl ^a,^*

PMCID: PMC3247587 PMID: 22219892

Abstract

The asymmetric unit of the title compound, C₁₁H₁₆N₂O₂, contains two independent conformational isomers which show intramolecular aromatic–imine O—H⋯N hydrogen bonds. In the crystal, neighboring molecules are linked through intermolecular aliphatic–aliphatic O—H⋯N, aliphatic–aromatic N—H⋯O and C—H⋯O interactions into hydrogen-bonded layers parallel to the ab plane.

Related literature

For crystal structures of metal complexes with this ligand, see: Haber et al. (2003 ▶); Kenar et al. (2001 ▶); Li et al. (1988 ▶); Rajendiran et al. (2007 ▶). For supramolecular assemblies with structurally related ligands, see: Barba et al. (2000 ▶); Fujita et al. (2008 ▶); Höpfl (2002 ▶); Severin (2009 ▶). For the tautomerism of salicylideneimines, see: Domínguez et al. (2011 ▶); Fujiwara et al. (2009 ▶); Ogawa et al. (1998 ▶); Rodríguez et al. (2007 ▶).

Experimental

Crystal data

C₁₁H₁₆N₂O₂
M _r = 208.26
Orthorhombic,
a = 7.0047 (11) Å
b = 14.171 (2) Å
c = 21.681 (3) Å
V = 2152.1 (6) Å³
Z = 8
Mo Kα radiation
μ = 0.09 mm⁻¹
T = 100 K
0.45 × 0.08 × 0.07 mm

Data collection

Bruker SMART CCD area-detector diffractometer
Absorption correction: multi-scan (SADABS; Sheldrick, 2003 ▶) T _min = 0.786, T _max = 0.994
12054 measured reflections
2677 independent reflections
2311 reflections with I > 2σ(I)
R _int = 0.052

Refinement

R[F ² > 2σ(F ²)] = 0.052
wR(F ²) = 0.115
S = 1.14
2677 reflections
289 parameters
6 restraints
H atoms treated by a mixture of independent and constrained refinement
Δρ_max = 0.26 e Å⁻³
Δρ_min = −0.24 e Å⁻³

Data collection: SMART (Bruker, 2000 ▶); cell refinement: SAINT-Plus (Bruker, 2001 ▶); data reduction: SAINT-Plus; program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: SHELXTL (Sheldrick, 2008 ▶) and DIAMOND (Brandenburg, 2006 ▶); software used to prepare material for publication: SHELXTL and PLATON (Spek, 2009 ▶).

Supplementary Material

Crystal structure: contains datablock(s) I, global. DOI: 10.1107/S1600536811039997/pk2347sup1.cif

e-67-o2849-sup1.cif^{(22.6KB, cif)}

Structure factors: contains datablock(s) I. DOI: 10.1107/S1600536811039997/pk2347Isup2.hkl

e-67-o2849-Isup2.hkl^{(131.5KB, hkl)}

Supplementary material file. DOI: 10.1107/S1600536811039997/pk2347Isup3.cml

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 (2)	1.77 (2)	2.562 (3)	157 (3)
O2—H2⋯N32ⁱ	0.84 (1)	2.00 (1)	2.839 (3)	178 (4)
N2—H2A⋯O1ⁱ	0.86 (2)	2.27 (2)	3.106 (3)	165 (2)
O31—H31⋯N31	0.84 (2)	1.82 (2)	2.596 (3)	154 (3)
O32—H32⋯N2ⁱⁱ	0.84 (1)	2.00 (1)	2.795 (3)	158 (4)
N32—H32A⋯O31ⁱ	0.86 (2)	2.55 (3)	3.347 (3)	154 (2)
C39—H39A⋯O32ⁱⁱⁱ	0.99	2.49	3.443 (4)	161

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Symmetry codes: (i) Inline graphic ; (ii) ; (iii) .

Acknowledgments

This work was supported by the Consejo Nacional de Ciencia y Tecnología (CIAM-59213).

supplementary crystallographic information

Comment

The title compound (I) has been employed as a tri- and tetradentate ligand for the complexation of transition metal ions such as vanadium(IV), vanadium(V), copper(II) and cadmium(II) (Haber et al., 2003; Kenar et al., 2001; Li et al., 1988; Rajendiran et al., 2007). We are interested in this compound in the search for ligands capable of forming macrocyclic structures with boronic acids (Barba et al., 2000; Fujita et al., 2008; Höpfl, 2002; Severin, 2009).

The asymmetric unit of (I) contains two conformers (Ia, Ib) (Fig. 1) with similar bond lengths between equivalent non-H atoms (differences less than 3 s.u.). The torsion angles (C–C–N–C) in the fragments CH₂CH₂NHCH₂are +62.7 (3) and -177.5 (2)° for Ia and Ib, respectively, showing that Ia and Ib are conformational isomers. The dihedral angles in the NCH₂CH₂N ethylene fragments are -171.8 (2) and -176.1 (2)°, respectively.

From reports in the literature it is known that salicylidene imines form keto and enol tautomers, both in solution and the solid state (Domínguez et al., 2011; Fujiwara et al., 2009; Ogawa et al., 1998; Rodríguez et al., 2007). In the crystal structure both conformers correspond to the enol form. This is evidenced by the presence of an intramolecular O–H···N hydrogen bond formed between the phenolic OH group and the imine function, and a comparative analysis of the bond lengths within the salicylidene fragment. The values for the C_arom–O and C=N bond lengths with values of 1.349 (3) and 1.274 (3)–1.275 (4) Å, respectively, are within the range expected for enol tautomers. The same is true for the C_arom–C_arom bond lengths with values ranging from 1.374 (4)–1.417 (4) Å (Domínguez et al., 2011). From a careful crystallographic analysis of eight salicylidene aminoalcohols, Domínguez et al. concluded that the dominant hydrogen bonding pattern in the crystal structures of enol tautomers are intermolecular O–H···O interactions formed between the pendant NCH₂CH₂OH fragments of neighboring molecules. For keto tautomers, intermolecular O–H···O interactions typically involve the C_arom–O oxygen atom (Domínguez et al., 2011). In the crystal structure of the compound described herein, the crystallographically independent conformers are linked through O–H···N interactions between the pendant aliphatic NCH₂CH₂OH groups to give one-dimensional chains along axis b. Neighboring chains are further linked parallel to the a axis by N–H···O and C–H···O interactions involving as acceptor atoms the oxygen atoms of the phenolic and aliphatic O–H functions to form overall two-dimensional hydrogen bonded layers propagating parallel to the ab plane (Fig. 2).

Experimental

For the preparation of (I), salicylaldehyde (0.234 g, 1.92 mmol) and 2-(2-aminoethylamino)ethanol (0.200 g, 1.92 mmol) were dissolved in 20 ml of ethanol. After reflux for 1 h, 60 ml of chloroform were added and the resulting solution was dried over anhydrous MgSO₄. Evaporation of the solvent mixture under vacuum gave a yellow oil. Crystals suitable for X-ray diffraction analysis were grown from a solution in chloroform, which was overlayered with n-hexane. Yield: 0.310 g (77%). M.p. 358 K.