7-[(3,5-Di-tert-butyl-2-hy­droxy­benzyl­idene)amino]-4-methyl-2H-chromen-2-one

Elham S Aazam; Orhan Büyükgüngör

doi:10.1107/S1600536810036743

. 2010 Sep 18;66(Pt 10):o2587–o2588. doi: 10.1107/S1600536810036743

7-[(3,5-Di-tert-butyl-2-hydroxybenzylidene)amino]-4-methyl-2H-chromen-2-one

Elham S Aazam ^a,^*, Orhan Büyükgüngör ^b

PMCID: PMC2983148 PMID: 21587568

Abstract

The title compound, C₂₅H₂₉NO₃, is a Schiff base derivative of coumarin 120. There are two structurally similar but crystallographically independent molecules in the asymmetric unit. Both molecules exist in E configurations with respect to the C=N double bonds. The dihedral angles between the coumarin and 3,5-di-tert-butyl-2-hydroxybenzylidene ring planes are 4.62 (7) and 14.62 (7)° for the two molecules. Intramolecular O—H⋯N hydrogen bonding involving the O—H groups and the azomethine N atoms generate S(6) rings. In the crystal structure, independent molecules are linked by C—H⋯π interactions, with groups of four molecules stacked along the c axis.

Related literature

For the chemistry and catalytic properties of coumarin-derived Schiff base complexes, see: Youssef et al. (2009 ▶). For their biological and pharmacological properties, see: Kulkarni et al. (2009 ▶); Youssef et al. (2009 ▶); Ronad et al. (2008 ▶). For their applications as dyes and fluorescent agents, see: Kachkovski et al. (2004 ▶); Creaven et al. (2009 ▶). For related structures, see: Honda et al. (1996 ▶); Aazam et al. (2006 ▶, 2008 ▶, 2010 ▶); El Husseiny et al. (2008 ▶). For hydrogen-bond motifs, see: Bernstein et al. (1995 ▶).

Experimental

Crystal data

C₂₅H₂₉NO₃
M _r = 391.49
Monoclinic,
a = 17.6067 (14) Å
b = 9.6853 (5) Å
c = 27.237 (3) Å
β = 109.832 (6)°
V = 4369.2 (6) Å³
Z = 8
Mo Kα radiation
μ = 0.08 mm⁻¹
T = 296 K
0.32 × 0.20 × 0.05 mm

Data collection

Stoe IPDS 2 diffractometer
29259 measured reflections
8242 independent reflections
3118 reflections with I > 2σ(I)
R _int = 0.072

Refinement

R[F ² > 2σ(F ²)] = 0.055
wR(F ²) = 0.146
S = 0.84
8242 reflections
524 parameters
84 restraints
H-atom parameters constrained
Δρ_max = 0.31 e Å⁻³
Δρ_min = −0.18 e Å⁻³

Data collection: X-AREA (Stoe & Cie, 2002 ▶); cell refinement: X-AREA; data reduction: X-RED (Stoe & Cie, 2002 ▶); program(s) used to solve structure: SHELXS97 (Sheldrick, 2008 ▶); program(s) used to refine structure: SHELXL97 (Sheldrick, 2008 ▶); molecular graphics: ORTEP-3 for Windows (Farrugia, 1997 ▶); software used to prepare material for publication: WinGX (Farrugia, 1999 ▶).

Supplementary Material

Crystal structure: contains datablocks I, global. DOI: 10.1107/S1600536810036743/sj5038sup1.cif

e-66-o2587-sup1.cif^{(34.3KB, cif)}

Structure factors: contains datablocks I. DOI: 10.1107/S1600536810036743/sj5038Isup2.hkl

e-66-o2587-Isup2.hkl^{(395.1KB, hkl)}

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

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

Cg1 and Cg2 are the centroids of the C26–C31 and C1–C6 rings, respectively.

D—H⋯A	D—H	H⋯A	D⋯A	D—H⋯A
O1—H1A⋯N1	0.82	1.80	2.538 (4)	149
O4—H4A⋯N2	0.82	1.80	2.537 (4)	149
C25—H25B⋯Cg1	0.96	2.73	3.536 (4)	143
C50—H50A⋯Cg2ⁱ	0.96	2.80	3.571 (4)	138
C50—H50B⋯Cg1ⁱⁱ	0.96	2.91	3.569 (4)	136

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

Acknowledgments

The authors acknowledge King Abdulaziz University for financial support and the Faculty of Arts and Sciences, Ondokuz Mayıs University, Turkey, for the use of the Stoe IPDS 2 diffractometer (purchased under grant F.279 of the University Research Fund).

supplementary crystallographic information

Comment

Coumarin-derived Schiff bases are regarded as "privileged ligands" due to their ability to form complexes with different transition metals that can act as catalysts for many different reactions (Youssef et al., 2009). They have been found to exhibit biological and plant regulating activities (Kulkarni et al., 2009; Youssef et al., 2009). They can also act as anti-inflammatory and analgesic agents (Ronad et al., 2008). Several reports of their applications as dyes and fluorescent agents have appeared (Kachkovski et al., 2004; Creaven et al., 2009).

In a continuation of our interest in the synthesis, crystal structure elucidation (Aazam et al., 2006, 2008, 2010), biological activity and photophysical properties of Schiff-base ligands incorporating a coumarin moiety and their metal complexes (El Husseiny et al., 2008), we report here the crystal structure of a newly synthesized coumarin Schiff base derived from 7-amino-4-methyl coumarin and 3,5-di-t-butyl-2-hydroxybenzaldehyde.

The asymmetric unit of the title compound (Fig. 1) consists of two crystallographically independent molecules, A and B (Honda et al. ,1996). The two independent molecules differ in planarity, where molecule A is more planar than molecule B, having dihedral angles between the coumarin and 3,5-di-tert-butyl- 2-hydroxybenzylidene ring planes of 4.64 (7)° and 14.62 (7)° for molecule A and B respectively. The planarity of both molecules is greater than that of the related 4-methyl-7-(salicylideneamino)coumarin Schiff base where the corresponding dihedral angle was 24.0 (1)° (Aazam et al., 2006). The greater planarity of the title compound may explain the higher fluorescence quantum yield of 0.53 observed (compared with Φ_f = 0.43 for 4-methyl-7-(salicylideneamino) coumarin in DMSO).

The terminal C=O bond distances of 1.203 (4)Å and 1.209 (4)Å agree with 1.2119 (15)Å found in the related compound 4-methyl-7-(salicylideneamino) coumarin (Aazam et al.2006), but are shorter than that of 1.3040 (17)Å found in 8-[(1E)-1-(2-Aminophenyliminio)ethyl]-2-oxo-2H-chromen-7-olate (Aazam et al., 2010). Intramolecular O—H···N hydrogen bonding involving the O–H groups and the azomethine N atoms generate S(6) rings (Bernstein et al., 1995). In the crystal structure, the independent molecules are linked by C—H···π interactions, with groups of four molecules stacked along the c axis (Fig. 2).

Experimental

3,5-di-tertbutyl-2-hydroxybenzaldehyde (0.26 g, 1.50 mmol) in 20 ml of absolute ethanol was added to a warm solution of 7-amino-4-methyl coumarin (0.35 g, 1.5 mmol) in 30 ml of absolute ethanol. The mixture was refluxed for 3 hrs upon which a yellow solution was formed. The solvent was pumped off by rotary evaporation leaving behind an orange solid shown to be pure by NMR spectroscopy. The product was recrystallized from chloroform by slow evaporation forming orange needles. Yield (68%, 0.4 g, 1.02 mmol).