We are interested in discrete porous metal-organic materials
which may have potential applications in catalysis and hydrogen storage. To
generate these materials, we prepare organic linkers (ligands) and treat them
with metal ions. Most of our ligands are based on β-diketones, such as meta-phenylenebis(acetylacetone)
(m-pbaH2; 1a, R = Me in diagram) and its analog meta-phenylenebis(dipropanoylmethane)
(m-pbprH2; 1b, R = Et). When treated with Cu2+,
the two ligands yield molecular squares (3)
ca. 14 Å in diameter that are soluble only in CHCl3 and CH2Cl2.
The solubility of the complexes is slightly better with R = Et. To improve
solubility further, we have recently tested the ligand 1c with R = C5H11.
The new ligand yields a copper molecular square that is soluble in eight
non-polar organic solvents.
We have also converted m-pbaH2 and m-pbprH2 to the β-ketoenamines m-pbiH2 and m-pbpriH2 (2, R = Me, Et) through microwave assisted synthesis. Both ligands yield molecular squares (3) with Cu2+, and m-pbpriH2 affords a diamagnetic molecular square (3) with Ni2+.