Tautomeric changes in guanfacine and its copper(II) complex as revealed by X-ray crystallography; synthesis and EPR

Obtention and crystal structure of guanfacine (guaH) together with synthesis and crystal structure of its copper complex [CuII(gua)2] · DMF were reported. The free molecule guaH exhibits one tautomeric form (B) in contrast to the form (A) which was reported in the Merck index. In the copper(II) complex, the anionic form gua− exhibits the third tautomeric form (C). This complex is characterized by a CuN2O2 coordination. The EPR spectrum is in agreement with a Cu(II) ion in a square planar configuration.