Germanium Phthalocyanine, GePc, and the Reduced Complexes SiPc(pyridine)₂ and GePc(pyridine)₂ Containing Antiaromatic π-Electron Circuits

The reaction of GeCl2(dioxane) with K2Pc(DMF)4 yields germanium phthalocyanine, GePc. GePc dissolves in pyridine to form GePc(py)2. The 1H NMR spectrum of GePc(py)2 and nucleus-independent chemical shift (NICS) calculations on GePc(NMe3)2 both show the presence of a strong paratropic ring current. That ring current, along with the bond-length alternation in the crystal structure of GePc(tBuPy)2, indicates the presence of an antiaromatic π-electron circuit in GePc(py)2. SiPc(py)2 was synthesized, and its electronic structure is similar to that of GePc(py)2.