Porous Inorganic-Organic Materials Based on Beta-Diketone Ligands

Synthesis and characterization of porous inorganic-organic materials have been studied mainly on two linear β-diketone multifunctional ligands: pyridine based pyacH and isocyanide based HacphNC. As a known ligand, the preparation of pyacH has been improved with higher yield. When pyacH reacts with Fe and Al metal salts, trigonal metal β-diketonate building blocks M(pyac)3 are produced. When pyacH reacts with zinc acetate, both trans and cis Zn(pyac)2 are produced, both isomers were isolated and characterized by single-crystal X-ray crystallography. Solutions of the trigonal building block Fe(pyac)3 generate various crystal structures on reaction with AgNO3 in CH3CN. When the concentration of AgNO3 is low, porous 2D honeycomb structures (Fe:Ag 1:1) are generated. Higher concentrations of AgNO3 result in 1D ladder structures (Fe:Ag 2:3). 1D ladder structures are generated when Fe(pyac)3 is dissolved in 1,2-dichlorobenzene, bromobenzene, or toluene. In porous 1D ladder structure, guest solvents can be exchanged by other solvents without destruction of metal-organic framework. The guests can be exchanged from bromobenzene to 1,2-dichlorobenzene, benzene, trichloroethylene and naphthalene. The exchange between bromobenzene and 1,2-dichlorobenzene has been studied by single-crystal X-ray diffraction and GC-MS. Al(pyac)3 can also generate a porous material with similar 1D ladder framework and guest molecules. 3-(4-isocyanophenyl)-2,4-pentanedione (HacphNC) was synthesized for the first time starting from 4-nitrobenzaldehyde. The synthesis was done by initial reduction/formylation to produce OHC-C6H4-NHCHO. The resulting 4-formylamino-benzaldehyde was converted to 3-(4-formylaminophenyl)-2,4-pentanedione by reaction with the biacetyl-trimethyl phosphate adduct. The β-diketone was protected by complexation to Al3+, Zn2+ and Cu2+. The metal complexes were then dehydrated by phosphorus oxychloride in the presence of diisopropylamine to generate M(acphNC)n metal complexes. The Al and Zn complexes were acidified to give the target ligand HacphNC. Cu(I), Mn(I), and Au(I) C-bound complexes of the isocyanide-β-dikektone ligand HacphNC were prepared on a small scale. NMR and IR indicate the formation of the expected products