Facile access to a series of large polycondensed pyridazines and their utility for the supramolecular synthesis of coordination polymers.

Domino cyclization of ketoenols and hydrazine leads to a series of polycondensed pyridazines, which reveal potential as rigid N-donor multidentate ligands for supramolecular synthesis of open coordination polymers.

Hydrate frameworks involving the pyridazino[4,5-d]pyridazine unit as a multiple hydrogen-bond acceptor.

1,4,5,8-Tetramethylpyridazino[4,5-d]pyridazine trihydrate, C(10)H(12)N(4) x 3 H(2)O, (I), and 1,2,3,6,7,8-hexahydrocinnolino[5,4,3-cde]cinnoline tetrahydrate, C(12)H(12)N(4) x 4 H(2)O, (II), exhibit exceptional functionality of the condensed N(4)-heteroaromatic frame as a symmetric acceptor of four hydrogen bonds [N...O = 2.843 (2)-2.8716 (10) A]. Thus, all the N atoms of the electron-deficient and highly pi-acidic polynitrogen heterocycles function as lone-pair donors. In (I), all the molecular components lie on or across special positions; the site symmetry is 2/m for the organic and m2m and m for the two water molecules. In (II), the organic polycycle lies across a crystallographic inversion center. Both structures involve a hydrogen-bonded centrosymmetric water-pyridazine dimer as the basic supramolecular unit, which is integrated into two-dimensional [in (I)] and three-dimensional [in (II)] hydrate frameworks by hydrogen bonding with the additional water molecules [O...O = 2.744 (2)-2.8827 (19) A]. The hydrate connectivity exists in the form of an (H(2)O)(3) trimer in (I) and as a one-dimensional zigzag (H(2)O)(n) chain in (II).