The First Characterized Coordination Compounds of Macrocyclic Ligands Including Incorporated Tetrazole Rings

The macrocyclic binuclear tetrazole, 2,2,5,5-tetramethyl-12-oxa-1,6,7,8,16,17,18,19-octaazatricyclo­[13.2.1.16,9]­nonadeca-7,9(19),15(18),16-tetraene (<b>L</b>), reacts with copper­(II) chloride or copper­(II) tetrafluoroborate hexahydrate to give complexes [Cu₃Cl₆L₂] (<b>1</b>) or [CuL₂(H₂O)₂]­(BF₄)₂(H₂O) (<b>2</b>), respectively. According to single crystal X-ray analysis, both complexes were found to be coordination polymers. In the crystal structure of complex <b>1</b>, there are neutral linear bibridged trinuclear units Cu₃Cl₆, in which the copper atoms are linked together by double chlorine bridges. Neighboring Cu₃Cl₆ units are bonded to each other by two bridging macrocyclic ligands L due to coordination bonds Cu–N between terminal copper atoms of Cu₃Cl₆ units and the tetrazole ring nitrogen atoms of ligands L to form polymeric chains. In complex <b>2</b>, the copper atom is bonded to three ligands L via the tetrazole ring nitrogen atoms, and to two water molecules, with formation of a square-pyramidal coordination of the metal. In this complex, one of two independent ligands L shows monodentate coordination, whereas another ligand plays the role of a bridge between two neighboring copper atoms being responsible for formation of polymeric cationic chains [CuL₂(H₂O)₂]_<i>n</i>^2<i>n</i>+. A complex system of hydrogen bonds connects the chains and the anions BF₄^– into a three-dimensional network. The temperature-dependent magnetic susceptibility measurements of complex <b>1</b> revealed that the copper­(II) ions were ferromagnetically coupled showing a coupling constant <i>J</i> of 50 cm^–1