4,4′-Bipyridazine: a new twist for the synthesis of coordination polymersElectronic supplementary information (ESI) available: Detailed procedure for preparation of unsubstituted 1,2,4,5-tetrazine. See DOI: 10.1039/b703911e.

A new polydentate ligand 4,4′-bipyridazine (4,4′-bpdz) was prepared by employing inverse electron demand cycloaddition of 1,2,4,5-tetrazine. A unique combination of structural simplicity, ampolydentate character and efficient donor properties towards Cu(i), Cu(ii) and Zn(ii) provide wide new possibilities for the synthesis of coordination polymers incorporating the 4,4′-bpdz module either as a bi-, tri- or tetradentate connector between the metal ions. 1D coordination polymers Cu2(4,4′-bpdz)(CH3CO2)4·4H2O and Zn(4,4′-bpdz)(NO3)2, and interpenetrated (4,4)-nets in [Cu(4,4′-bpdz)2(H2O)2]S2O6 were closely related to 4,4′-bipyridine compounds. 1D “ladder-like” polymer Cu2(4,4′-bpdz)3(CF3CO2)4 and the unprecedented 3D binodal net ({86}{63;83}) in [Cu3(4,4′-bpdz)6(H2O)4](BF4)6·6H2O were based upon a combination of linear and angular organic bridges. Complex [Cu3(OH)2(4,4′-bpdz)3(H2O)2{CF3CO2}2](CF3CO2)2·2H2O has a “NbO-like” 3D topology incorporating discrete dihydroxotricopper(ii) clusters linked by tri- and tetradentate ligands. The tetradentate function of the 4,4′-bpdz ligand was especially relevant for copper(i) complexes, which adopt layered Cu2X2(4,4′-bpdz) (X = Cl, Br) or 3D chiral framework (X = I) structures based upon infinite (CuX)n chains. The electron deficient character of the ligand was manifested by short anion–π interactions (O–π 3.02–3.20; Cl–π 3.35 Å), which may be involved as a factor for controlling the supramolecular structure. [ABSTRACT FROM AUTHOR]