Synthesis, characterization and X-ray structures of the new dinucleating ligand 2,8-dimethyl-1,4,5,6,7,10,11,12-octahydroimidazo[4,5-h] imidazo[4,5-c][1,6]diazecine-5,11-diethanoic acid and its Cu(II) complex; an alternating chain of Cu(II) ions, cou