Crystal structures of dimethyl 5-iodo-iso-phthal-ate and dimethyl 5-ethynyl-iso-phthal-ate

In dimethyl 5-iodo-isophthalate, C₁₀H₉IO₄, (I), the planes through the methyl carboxyl-ate moieties are tilted with respect to the benzene ring, whereas the mol-ecular framework of dimethyl 5-ethynylisophthalate, C₁₂H₁₀O₄, (II), is perfectly planar. The crystal structure of (I) is stabilized by a three-dimensional supra-molecular network comprising C-H⋯O=C hydrogen bonds, as well as I⋯O=C inter-actions. In the crystal of (II), the mol-ecules are connected via C-H_ethyn-yl⋯O=C hydrogen bonds to infinite strands. Moreover, π-π arene stacking inter-actions connect the mol-ecular chains into two-dimensional supra-molecular aggregates.