Interactions of organic halide and nitrate salts with meso-octamethylcalix[4]pyrrole

Proton NMR titrations have been performed with meso-octamethylcalix[4]pyrrole and a variety of organic chloride and bromide salts in dichloromethane-d2. The results show apparently increasing chloride stability constants within each set of anion salts (tetrabutylammonium < imidazolium < pyridinium). Addition of 1-ethyl-3-methylimidaolium (EMIM) nitrate to dichloromethane-d2 solutions of calix[4]pyrrole caused significantly larger downfield shifts of the pyrrole NH protons of calix[4]pyrrole than addition of equimolar quantities of tetrabutylammonium nitrate. The first crystal structure of a nitrate complex of a calix[4]pyrrole is also presented