Br...O contacts and π–π stacking dominate the packing in methyl 4-bromo-3,5-dimethoxybenzoate

Abstract

The title compound, C10H11BrO4, a useful precursor to pharmaceutically active isocoumarin and isochroman derivatives, crystallizes with two unique molecules in the asymmetric unit. A π-π stacking interaction links the planar molecules in the asymmetric unit. Additional π-π contacts stack pairs of molecules along the c axis. A feature of the crystal packing is the presence of a number of short Br···O contacts. A particularly unusual arrangement involves the formation of dimers, with pairs of Br···O contacts imposing a close Br···Br interaction and generating five-membered rings within an eight-membered ring formed by two Br···O contacts. Only two comparable arrangements have been reported previously. The Br···O contacts combine with weak C-H···O hydrogen bonds to form corrugated sheets of molecules approximately parallel to (001). These sheets are stacked along the c axis by π-π interactions to generate a three-dimensional network.