4,4′-Diiodo-3,3′-dimethoxybiphenyl

The molecules of the title compound, C14H12I2O2, lie on inversion centers and are linked by I⋯O interactions with intermolecular distances of 3.324 (3) Å. The aromatic rings display no significant intercalation or stacking interactions.

The molecules of the title compound, C 14 H 12 I 2 O 2 , lie on inversion centers and are linked by IÁ Á ÁO interactions with intermolecular distances of 3.324 (3) Å . The aromatic rings display no significant intercalation or stacking interactions.

Comment
Over the last 25 years, much attention has been focused on the synthesis of artificial ion channels due to their potential applications in biomedical and material sciences (Schwab & Levin, 1999;Mullen & Wegner, 1998;Fidzinski et al., 2003).
The title compound has been used as a precursor for the synthesis of oligo(p-phenylene)s (Baumeister et al., 2001) and as a source of hydrophobicity and rigidity (Sakai et al., 1997;Sakai & Matile, 2003) in artificial ion channels. When a macrocycles like porphyrin is attached to the oligo(p-phenylene)s, the π-π stacking of porphyrin and the antiperiplanar arrangement of the oligo(p-phenylene)s should result in cylindrical self-assembly process and ultimately lead to the formation of functionalized pores (Sisson et al., 2006). Furthermore, iodinated biphenyl has a bright prospect as X-ray contrast media (Anelli et al., 2001).
In this paper, we report the sysnthesis and crystal structure of the title compound, (I). The molecules of (I) lie on crystallographic inversion centers. The I1-O1 intermolecular distance is 3.324 (3) Å which is significantly shorter than 3.50 Å, the sum of the van der Waals radii for I and O, supporting the idea that oxygen atom of methoxy disturbs the electronic cloud surrounding the iodide, hence creating polarization over iodide and subsequently causes reduction in the I1-O1 intermolecular distance. The crystal structures of three hexaiododerivatives of biphenyl have been reported (Anelli et al., (2001).

Experimental
Fast Blue B salt (o-dianisidine bisdiazotated zinc double salt, 10.00 g, 21 mmol), was added to a solution of KI (28 g, 0.17 mmol) in water (200 ml). The mixture was stirred at room temperature for 14 h. After dilution with dichloromethane, the crude reaction mixture was concentrated in vacuo. Purification of the crude product on silica gel (dichloromethane:hexane 1:4) followed by evaporation of the solvent under in vacuo gave the pure desired product as a pale yellow solid in 70% yield. Single crystals suitable for X-ray crystallography were obtained by slow evaporation of a solution of pale yellow solid in ethanol at room temperature.

Refinement
All H atoms were geometrically positioned and were allowed to ride on the corresponding C-atoms with C-H = 0.96 Å and U iso (H) = 1.5U eq (C) of the attached C atom for methyl H atoms and 1.2U eq (C) for other H atoms. The highest peak in the final difference Fourier map corresponding to a residual electron density of 1.08 e/Å 3 was located at 1.2 Å from H5 and was deemed meaningless.
supplementary materials sup-2 Figures   Fig. 1. A thermal ellipsoid plot of the title compound drawn at 50% probability level. The symmetry related atoms have been identified by the letter A in atomic labels.

Special details
Experimental. 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 > 2sigma(F 2 ) is used only for calculating R-factors(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. Geometric parameters (Å, °)