Mimicking cellular phospholipid bilayer packing creates predictable crystalline molecular metal-organophosphonate macrocycles and cages

Abstract

We report a novel mechanism to create a predictable molecular metal-organophosphonate cage [Zn-2(2,2'-bpy)(2)(H2ODP)(2)(H4ODP)]center dot 2H(2)O (1 center dot 2H(2)O) (H4ODP = 1,8-octanediphosphonic acid) and a macrocycle [Cu-2(2,2'-bpy) 2(H-2-1,4-NDPA)(2)(H2O)(2)]center dot H2O (2) (H-4 -1,4-NDPA = 1,4-naphthalene diphosphonic acid). The structures were solved using single crystal X-ray diffraction. The photoluminescence properties of 1 center dot 2H(2)O, investigated both in solution and in the solid-state at room temperature, indicated that the tighter zinc binding in the solid state leads to the augmentation of fluorescence. The ORCA molecular structure optimization calculations for 1 center dot 2H(2)O suggest a slight opening of the cage structure in non-polar solvents while in polar solvents the cage is tightened. Toxicity analysis with Caco-2 cells indicates that the molecule is readily tolerated by intestinal cells.