Guest Inclusion and Interpenetration Tuning of Cd(II)/Mn(II) Coordination Grid Networks Assembled from a Rigid Linear Diimidazole Schiff Base Ligand

Cd(II)/Mn(II) coordination grid networks containing large meshes have been assembled from a long rigid ligand, 2,5-bis(4'-(imidazol-1-yl)benzyl)-3,4-diaza-2,4-hexadiene (ImBNN), and M(CF3SO3)(2) (M = Cd and Mn) salts, and their interpenetration change upon guest inclusion has been investigated with a series of aromatic molecules. Without guest molecules, the grid networks are triply interpenetrated to form closely packed layer structures [M(ImBNN)(2)(CF3SO3)(2)](n) (M = Cd (1) and Mn (2)), but when guest molecules are introduced, the triply interpenetrated frameworks are changed to doubly interpenetrated ones with the inclusion of various aromatic molecules, namely, {[M(ImBNN)(2)(CF3SO3)(2)]superset of guest}(n) (M = Cd, guest = o-xylene (3), naphthalene (4), phenanthrene (5), and pyrene (6); M = Mn, guest = benzene (7), p-xylene (8), naphthalene (9), phenanthrene (10), and pyrene (11)). These complexes have been characterized by means of single-crystal X-ray diffraction, X-ray powder diffraction, and IR spectra. The guest-inclusion/desorption behaviors of representative complexes have been studied by thermogravimetric analyses and H-1 NMR measurements. The grid networks display strong preference for aromatic guest inclusion, but less selectivity toward shape and size difference. Tuning of network interpenetration from 3-fold to 2-fold has been successfully achieved through the introduction of guest molecules, when the network displays flexibility to change cavity size to match the guest molecules.