Triphenylamine-Based Bis(β-Diketones) for Construction of Supramolecular Copper(II) Complexes

Two new bis(beta-diketone) ligands based on triphenylamine have been prepared and crystallized. Treatment of 4,4'-diformyltriphenylamine with two phospholenes (2,2,2-trimethoxy-4,5-dimethyl-1,3,2-dioxaphospholene and 2,2,2-trimethoxy4,5-diethyl-1,3,2-dioxaphospholene) afforded the bis(beta-diketones) triphenylaminebis(2,4-pentanedione) (tpbaH(2), 1); and triphenylaminebis(3,5-heptanedione) (tpbprH(2), 2) as white solids. X-ray analysis of 1 and 2 shows that they are in the enol form. Also, their triphenylamine moieties have a chiral "propeller" shape; the centrosymmetric structures contain equal numbers of the two enantiomeric propellers. Reaction of 1 and 2 with [Cu(NH3)(4)](2+)(aq) yielded dark-green solids. The Cu complex of 1 was insoluble in common solvents, but that of 2, Cu-4(tpbpr)(4) (3), is soluble in dichloromethane and chloroform. 3 is assigned the cyclic tetrameric structure Cu-4(tpbpr)(4) based on ESI-MS and microanalytical data. This is similar to the copper(II) beta-diketonate molecular squares reported previously from our group. Molecular modeling indicates that Cu-4(tpbpr)(4) has Cu center dot center dot center dot Cu distances of ca. 21 angstrom, as compared to ca. 14 angstrom in the previous molecular squares. [GRAPHICS] .