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(CF(3)SO(3))(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)(CF(3)SO(3))(2) (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)(CF(3)SO(3))(2)] superset 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 (1)H 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.