A Noninterpenetrated 1D Molecular Ladder and 2D Butterfly Network:  Effect of Positional Isomerism of Semirigid Bis(pyridylmethyl)pyromellitic Diimide Ligands on the Architecture of Their Metal(II) Complexes

Three new complexes [Cd(4-pmpmd)_1.5(NO₃)₂]·CHCl₃ (1), [Cd(3-pmpmd)_1.5(NO₃)₂]·EtOH (2), and [Zn(3-pmpmd)_1.5(NO₃)₂]·MeOH (3) (3- or 4-pmpmd = N,N‘-bis(3- or 4-pyridylmethyl)pyromellitic diimide) containing T-shaped building blocks have been obtained from reactions between the long semirigid ligands 3- or 4-pmpmd and either cadmium or zinc nitrate. 1 forms noninterpenetrated 1D molecular ladders that are linked via multiple, complementary intermolecular C−H···O hydrogen bonds that effect the 3D alignment. 2 and 3 are isostructural and feature a noninterpenetrated 2D butterfly-shaped network with (6,3) topology. Multiple intermolecular C−H···O hydrogen bonds exist between the 2D layers and generate the 3D framework. The structural differences between 1 and 2 or 3 are attributed to the different conformations adopted by the ligands, which illustrate the influence of positional isomerism on the resultant supramolecular architectures of metal complexes.