X-(Diiodoarsanyl)benzoic acid (X = 3 and 4)

The title compounds, 4-(diiodoarsanyl)benzoic acid, (I), and 3-(diiodoarsanyl)benzoic acid, (II), both [As(C(7)H(5)O(2))I(2)], which possess a -COOH coordinating group, form molecular crystal structures composed of hydrogen-bonded dimers, the packing differences of which are caused by the relative position of the diiodoarsanyl groups. The para isomer, with Z' = 1, crystallizes in a layered structure with shortened contacts of the As atoms to only the arene rings of adjacent molecules. In contrast, the meta isomer, with Z' = 3, forms separate rectangular blocks of three ribbons, each composed of dimeric molecular units positioned almost directly above each other and with the As atoms possessing only two As···I contacts to the I atoms of neighbouring molecules.