1,4,5,8-Tetra-n-butylanthracene

The molecule of the title compound, C30H42, occupies a special position on an inversion center. The four butyl side chains have all-trans planar conformations, and the alkyl planes are nearly orthogonal to the anthracene plane [C—C—C—C torsion angles of 79.6 (2) and 78.2 (2)°]. The overall molecule has a stair-like shape with the n-butyl groups at the 1 and 8 positions extending towards the same side of the anthracene plane. In the crystal structure, molecules adopt a slipped–parallel arrangement without π–π stacking.


Related literature
For background to solid-state packing effects in electronic and photonic materials, see: Curtis et al. (2004). For the correlation betweenstacking and fluorescence quantum yields, see: Yoshida et al. (2002).  Solid-state packing effects play an important role in the performance of electronic and photonic materials (Curtis et al., 2004). However, there has been relatively little research on the correlation between solid-state packing patterns and fluorescence properties. Therefore, molecular design principles which could allow to control solid-state fluorescence are not fully understood.
We have recently found that the introduction of different alkyl side chains onto anthracene nucleus at the 1, 4, 5, and 8 positions brought about considerable variety in alkyl conformations, packing patterns, and solid-state fluorescence properties. As a part of systematic investigation of this phenomena, we report herein the structure of the title compound, namely, the anthracene tetra-n-butyl derivative (Fig.1).
The molecule occupies a special position in the inversion center. The bond lengths and bond angles are comparable to those of other 1,4,5,8-tetraalkylanthracenes (Kitamura, Abe et al., 2007). Four butyl side chains adopt all-trans planar conformations, and the alkyl planes are nearly orthogonal to the anthracene plane; the torsion angles of C6-C1-C8-C9 and C5-C4-C12-C13 are 79.6 (2) and 78.2 (2)°, respectively. Thus, the molecule of the title compound has a stair-like shape, and two butyl groups at the 1 and 8 positions extend towards the same side of the anthracene plane. This molecular structure is similar to that of 1,4,7,10-tetra-n-butyltetracene (Kitamura, Ohara et al., 2007;Kitamura et al., 2010).
In crystal the molecules show a slipped-parallel arrangement without π-π stacking (Fig. 2). Such packing, as has been shown (Yoshida et al., 2002), can enhance fluorescence quantum yields because of the same directions of transition dipole moments for all molecules as well as no concentration quenching (Kitamura, Abe et al., 2007).
To examine the influence of crystal packing on the solid-state fluorescence properties, the fluorescence spectrum and the absolute quantum yield of the title compound were measured with a Hamamatsu Photonics PMA11 calibrated optical multichannel analyzer with a solid-state blue laser (λ ex = 377 nm) and a Labsphere IS-040-SF integrating sphere. The crystals exhibited a broad fluorescence spectrum with a fluorescence maximum at 450 nm, a shoulder peak around 467 nm and very high quantum yield (Φ = 0.78). Among 1,4,5,8-tetraalkylanthracenes, only the propyl derivative had higher quantum yield of 0.85 (Kitamura, Abe et al., 2007), which is of course still quite comparable to that of the title compound.
Then the mixture was warmed up to room temperature over 2 h and stirred at room temperature for additional 18 h. After quenching with water, the aqueous layer was extracted with CHCl 3 . The combined organic layer was washed with brine and dried over Na 2 SO 4 . After evaporation, the residue was subjected to slica-gel chromatography with (2:1)-hexane/CHCl 3 to afford bis(furan)adduct as an orange solid (602 mg, 18°). The bis(furan)adduct (602 mg, 1.38 mmol) in EtOH (60 ml) was hydrogenated over 10° Pd/C (125 mg) under atmospheric pressure at room temperature for 3 h. The catalyst was removed by filtration, and the filtrate was evaporated under reduced pressure. To the residue, an ice-cooled solution of (1:5)-conc.
HCl/Ac 2 O (6 ml) was added. The mixture was stirred at room temperature for 3 h. After cooling with ice, water was added into the mixture. The resultant mixture was extracted with CHCl 3 , and the extract was washed with aqueous Na 2 CO 3 and brine, and dried over Na 2 SO 4 . After evaporation of the solvent, column chromatography on silica gel with (2:1)-hexane/

Refinement
All the H atoms were positioned geometrically and refined using a riding model with C-H bonds of 0.94 \%A, 0.98\%A, and 0.97\%A for aromatic, methylene, and methyl groups, respectively, and U iso (H) = 1.2U eq (C) [U iso (H) = 1.5U eq (C) for methyl H atoms]. Fig. 1. Molecular structure of the title compound; displacement ellipsoids are drawn at the 30°p robability level; the unlabelled atoms are derived by the symmetry transformation −x + 2, −y + 1, −z + 1.   Refinement. Refinement of F 2 against ALL reflections. The weighted R-factor wR and goodness of fit S are based on F 2 , conventional R-factors R are based on F, with F set to zero for negative F 2 . The threshold expression of F 2 > 2σ(F 2 ) is used only for calculating Rfactors(gt) etc. and is not relevant to the choice of reflections for refinement. R-factors based on F 2 are statistically about twice as large as those based on F, and R-factors based on ALL data will be even larger.