Bis[4-(salicylideneamino)phenyl]methane

Abstract

The crystal structure of the title Schiff base {systematic name: 2,2 H -[methylenedi-p-phenylenebis(nitrilomethylidyne)]-diphenol}, C 27 H 22 N 2 O 2 , consists of intramolecularly hydrogen-bonded molecules interlinked by CÐHÁ Á ÁO hydrogen bonds [CÁ Á ÁO = 3.426 (2) A Ê and CÐHÁ Á ÁO = 152.7 (17) ]. The molecule is in the enol form and is located on a twofold axis. The central methane C atom of the diphenylmethane motif is displaced from the aromatic ring planes. This effect is compared with previous results, which display an inverse correlation between the out-of-plane displacement and the CÐCÐC angle around the central methane C atom. In the title compound, the displacement is 0.124 (2) A Ê and the CÐ CÐC angle is 110.18 (19) . CommentBis-bidentate Schiff base ligands have attracted signi®cant interest as building blocks in metallo-supramolecular chemistry, especially in the synthesis of helicates (see, for example, Kruger et al., 2001;Yoshida & Ichikawa, 1997;Yoshida et al., 2000;Franceschi et al., 2001;Albrecht, 2001). The title compound, (I), has been shown to form helicate supramolecular complexes of the form [M 2 L 2 ] with transition metals (Yoshida & Ichikawa, 1997;Yoshida et al., 2000;Kruger et al., 2001). Free N-salicylideneanilines are often thermochromic (Ogawa et al., 1998;Filarowski et al., 2002;Popovic  et al., 2002;Ogawa & Harada, 2003) due to a temperature-dependent equilibrium between the keto±amine and enol±imino forms.The location of the H atoms showed unequivocally that (I) occurs in the enol±imino form in the crystalline state, in agreement with previous IR results ( Kruger et al., 2001;Pui et al., 2001). This is also the form found in CHCl 3 solution (Yoshida et al., 2000;Kruger et al., 2001). The factors determining whether a given molecule will occur in the keto±amine or enol±imino form are manifold. It has been shown to depend on the substitution on the benzene rings (Filarowski et al., 2002;Popovic  et al., 2002) and intermolecular hydrogen bonding (Ogawa et al., 1998;Ogawa & Harada, 2003), and aggregation (packing) of the molecules plays an important role for the equilibrium in solution (Ogawa et al., 2001;Ogawa & Harada, 2003). It has been reported that ( The molecular structure of (I), showing the atom-labelling scheme. Displacement ellipsoids are drawn at the 50% probability level and H atoms are shown as small spheres of arbitrary radii. Dashed lines indicate the intramolecular OÐHÁ Á ÁN hydrogen bonds. (a) A projection of (I) on to the mean plane. The molecule is situated on a twofold axis (through atom C14); unlabelled atoms are related to labelled atoms by the symmetry operator (1 À x, y, Àz + 3 2 ). (b) A view of (I) perpendicular to the least-squares plane of the C8±C13 aromatic ring. Note the twist of the molecule at the N atom.³ Present address:

2-[N-(4-{4-[(2-Hydroxy-5-methoxybenzylidene)amino]benzyl}phenyl)carboximidoyl]-4-methoxyphenol

“…There are two symmetry equivalent intramolecular O-H···N hydrogen bonds. The bond lengths and bond angles within the molecule agree well with those of the closely related compounds C 27 H 22 N 2 O 2 (CCDC refcode YEFWUC; Birkedal & Pattison, 2006) and C 26 H 20 N 2 O 3 (Shahverdizadeh & Tiekink, 2011). In the unit cell, the molecules are tightly stacked one above the other along the short b-axis (b = 4.5993 (3) Å) and are held together in this direction by slipped π-π stacking interactions between the phenyl rings and the iminomethylidene groups.…”

“…For related bis-bidentate Schiff base ligand structures, see: Birkedal & Pattison (2006); Shahverdizadeh & Tiekink (2011). For Schiff base ligands, see: Chu & Huang (2007); Yoshida & Ichikawa, (1997); Kruger et al (2001); Moutet & Ourari (1997).…”

“…, 1995); cell refinement: X-RED (Stoe & Cie, 1995); data reduction: X-RED; program(s) used to solve structure: SIR92 (Altomare et al, 1993); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997); software used to prepare material for publication: publCIF (Westrip, 2010). Bis-bidentate Schiff base ligands have been extensively studied and used as building blocks in metallo-supramolecular chemistry (Birkedal & Pattison, 2006;Shahverdizadeh & Tiekink, 2011;Chu & Huang, 2007;Yoshida & Ichikawa, 1997;Kruger et al, 2001). These compounds were also used as thermosetting resins (Lin et al, 2008) and in ion selective membranes for detecting traces of copper (Sadeghi et al, 2003).…”

Functional Organogel Based on a Salicylideneaniline Derivative with Enhanced Fluorescence Emission and Photochromism

“…As suggested by van Esch and Feringa,1b if an organic compound is expected to be a gelator for an organic solvent three important guidelines must be followed: 1) strong self‐complementary and unidirectional intermolecular interactions to induce one‐dimensional (1D) packing of the molecules need to be present; 2) control of the interfacial energy between the aggregation and the solvent to adjust the solubility of the gelator and to prevent crystallization is required; and 3) some factors that favor the cross‐linking of 1D fibers to form 3D networks should be considered. Recently, Birkedal and Pattison reported the crystal structure of bis(4‐[salicylideneamino]phenyl)methane ( 1′ ),12 which has a V‐shaped conformation and packs into 1D J aggregations along the b axis through strong π–π interactions among the aromatic rings (Figure 1). Such close stacking (the distance between the two adjacent parallel aromatic rings is 3.6 Å) of the salicylideneaniline groups leads to enhanced photoluminescence and non‐photochromism under UV‐light irradiation 7e.…”

Self‐assembly of Dinuclear Double‐stranded Copper(II) Helicates with 3‐Ethoxy‐2‐hydroxyphenyl Substituted Diimines. Synthesis, Molecular Structure, and Host‐guest Recognition of H2O

“…The ligand is arranged in the enol-imine form and has a typical characteristic V-shape similar to related diimine ligands with different linker functions (-S-, -O-, -CH 2 -) and changing substituents in 3-and 5-position. [19,20] It is interesting to note, that upon cooling of the solid ligand a color change is observed indicating a thermochromism between both tautomers as observed previously for similar ligands. [20,21] [5,[14][15][16]18] However, the Cu···Cu separation is with 11.53 Å significantly shorter as in the structure related helicates (the data are given in Table S11, Supporting Information).…”