STRUCTURE OF DIIODIDE SALTS OF N-HETEROAROMATIC DICATIONS

The structures of 2,2'-dimethyl-1,1'-biisoquinolinium diiodide monohyd rate (I) and 1, 1'-dimethyl-4,4'-biquinolinium diiodide (II) have been determined. Both biisoquinolinium and biquinolinium dications have a twofold rotation axis. The two N-heteroaromatic planes in (I) are twis ted from each other to a greater extent than those in (II); this can b e explained by steric repulsion of the N-methyl groups in (I). In both crystals each I- anion is in a relatively close contact with one of t he positively charged N atoms of the dications. These interionic inter actions seem to be responsible for the deep red color of the crystals.