Potassium Phthalocyanine, KPc: one-dimensional molecular stacks bridged by K+ ions.

We report the synthesis of potassium phthalocyanine (KPc) and its structural characterization by synchrotron X-ray powder diffraction. We find that while KPc adopts the beta-polymorphic structural type (monoclinic space group P21/a) common for many MPc solids, its structure is characterized by unique features. The K+ ions, which are statistically disordered over two symmetry-equivalent positions, reside in the intrastack spacing of the rodlike molecular assemblies and strongly bond equidistantly to selected N atoms of the two neighboring Pc rings along the chain direction with an unusual 5-fold coordination. The K+-stuffed slipped stacks of Pc units display much greater intrastack and slippage distances than those of other beta-MPc polymorphs. They may be thought as comprising disordered dimeric (Pc)22- units; this leads to electron pairing and is consistent with the observed nonmagnetic response of the system.