Novel metal-organic frameworks derived from group II metal cations and aryldicarboxylate anionic ligands

Reaction of magnesium, calcium, strontium, and barium salts with a range of dicarboxylic acids [benzene-1,4-dicarboxyl ic acid (H2BDC), naphthalene-2,6-dicarboxylic acid (H2NDC), 4,5,9, 10-tetrahydropyrene-2,7-dicarboxylic acid (H-2)TPDC), pyrene-2,7-dicarboxylic acid (H2PDC), 5, 1 0-dihydroanthracene-2,7-dicarboxylic acid (H(2)DADC] in N,N'-dimethylformamide (DMF) or N,N'-diethylformamide (DEF) in Teflon-lined stainless steel autoclaves produces a range of metal-organic framework materials. Single crystal X-ray analysis has confirmed that the predominant building block in these materials is a chain of metal centers bridged either by carboxylate moieties alone as in [M(DMF)(mu-BDC](infinity) (M = Mg or Sr), [Ca-1.5(DEF)(mu-BDC](1.5)](infinity), and [Sr(DEF)(OH2)(mu-BDC](infinity) or bridged by both carboxylate ligands and DMF/DEF molecules as in [M(mu-DMF)(mu-NDQC](infinity) (M = Ca, Sr, or Ba), [M(mu-DEF)(mu-TPDC](infinity) (M = Ca or Sr), [M(mu-DMF)(mu-DADC](infinity) (M = Ca or Sr), and [Sr(mu-DEF)(mu-PDC)](infinity). In contrast, the isomorphous complexes [Mg-3(DMF)(4)(mu-NDC)(3)](infinity) and [Mg-3(DEF)(4)(mu-NDC](3)](infinity) contain centrosymmetric trinuclear moieties in which each pair of cations is bridged by three carboxylate anions with two pendant solvent molecules coordinated to each of the terminal Mg2+ cations. These trinuclear building blocks act as six-connected nodes and generate a tilted alpha-Po type structure. Eleven of the 12 structures based upon cationic chains adopt a common extended architecture in which the aryldicarboxylate anions link the chains to generate diamond-shaped channels. However, in the material [Sr(DMF)(mu-BDC)](infinity), the chains are linked to generate a hexagonal motif of triangular channels. In all 12 compounds based on cationic chains, the space within the channels is occupied by coordinated solvent molecules, leading to nonporous materials.