5,5′-Selenobis(2-hydroxybenzaldehyde)

In the title molecule, C14H10O4Se, the dihedral angle between the two benzene rings is 74.6 (1)°. Both hydroxybenzaldehyde groups form intramolecular O—H⋯O hydrogen bonds. In the crystal, pairs of molecules are linked by pairs of weak C—H⋯π(arene) interactions, forming centrosymmetric dimers. In addition, molecules are linked by π–π stacking interactions, with a centroid–centroid distance of 3.785 (2) Å, forming chains along the c axis.

In the title molecule, C 14 H 10 O 4 Se, the dihedral angle between the two benzene rings is 74.6 (1) . Both hydroxybenzaldehyde groups form intramolecular O-HÁ Á ÁO hydrogen bonds. In the crystal, pairs of molecules are linked by pairs of weak C-HÁ Á Á(arene) interactions, forming centrosymmetric dimers. In addition, molecules are linked bystacking interactions, with a centroid-centroid distance of 3.785 (2) Å , forming chains along the c axis.

Comment
The organo-selenium nucleus is one of the most abundant structural nucleus found in natural products and biologically active molecules (e.g., seleno-carbohydrates,selenoamino acids,and seleno-peptides) (Mukherjee et al.,2006;Phadnis et al., 2005;Braga et al., 2005). Moreover, organoselenium compounds have emerged as an exceptional class of structures that exemplify a role in biochemical processes, serving as important therapeutic compounds ranging from antiviral and anticancer agents to a variety of situations where free radicals are involved (Mugesh et al., 2001). We are currently studing the synthesis of a new series of organoselenium compounds, such as selanes, diselenides and macrocyclic Schiff bases containing selenium atoms. Reported herein are the synthesis and X-ray structure of the title compound.
In the molecule ( Fig. 1), the dihedral angle between the two benzene rings is 74.6 (1)°. Two intramolecular O-H···O hydrogen bonds are present in the molecule. The Se1-C1 and Se1-C8 bond lengths are the same within experimental error.

Experimental
A mixture of salicylaldehyde (87.93 g, 0.72 mol), selenium dioxide (26.63 g, 0.24 mol)and concentrated hydrochloric acid (132 ml) was stirred for 0.5 h at room temperature. Then, the mixture was further stirred for 50 h at 353 K. The resulting reddish brown solid was filtered, washed with water and ethanol. The obtained yellowish solid was recrystallized with ethyl acetate and etanol (v:v=5:1) to give yellowish crystals of the title compound in yield 20.8%, which are suitable for X-ray analysis.

Refinement
All H atoms were placed in calculated positions (C-H = 0.93 Å, O-H = 0.82Å) and included in a riding-model approximation, with U iso (H) = 1.2U iso (C) or 1.5U iso (O) Figures   Fig. 1. The molecular structure of (I) with 50% probability displacement ellipsoids for non-H atoms.