Fused pyridazines: Rigid multidentates for designing and fine-tuning the structure of hybrid organic/inorganic frameworks

Fused pyridazines (1,2,3,6,7,8-hexahydro-cinnolino[5,4,3-cde]cinnoline, L and its 2,2,7,7-tetramethyl derivative, Me₄L) are designed as rigid multidentate ligands for the construction of framework solids. In combination with copper(I) bromide (iodide) they provide excellent structural examples for predictive engineering and the possibilities for further fine-tuning of the framework architectures facilitated by the tetradentate function of the ligands and effective cooperation of organic and inorganic bridges. This study features control over helical structures for (CuX)_n chains and homo/heterochiral combination of the helices in the lattice, the design of a range of channelled and tubular CuX networks and the structural significance of ligand shape complementarity. 3D tetragonal Cu₂X₂(L) frameworks exist either as chiral or achiral supramolecular isomers Cu ₂I₂(Me₄L) and Cu₁₂l ₁₂Cu(CH₃CN)}₃(L)₆-Cu ₃l₆-CH₃CN illustrate 3D hexagonal channelled and tubular arrays; Cu₂I₂(Me₄L)(CH ₃CN) and Cu₄I₄(L)(CH₃CN)₂ complexes are 1 D polymers.