Dinuclear metal phosphonates and -phosphates

摘要

The reaction of Cu(II) or Cd(II) salts with 2,4,6-iPr_3C _6H_2PO_3H_2, 2,4,6-iPr _3C_6H_2CH_2PO_3H_2 or 2,6-iPr_2C_6H_3OPO_3H_2 in the presence of strong chelating nitrogen ligands such as 2,2′-bipyridine (bpy), 1,10-phenanthroline (phen), 2-pyridylpyrazole (pypz) or 3,5-dimethyl pyrazole (dmpz) as the ancillary ligands afforded dinuclear copper or cadmium complexes [Cu_2(2,4,6-iPr_3C_6H_2PO _3H)_4(bpy)_2] (4), [Cu_2(2,6-iPr _2C_6H_3OPO_3H)_2(bpy) _2(OAc)_2(CH_3OH)_2]·(CH _3OH) (5), [Cd_2(2,6-iPr_2C_6H _3OPO_3H)_4 (bpy)_2(CH _3OH)_2]·2(CH_3OH) (6), [Cd _2(2,6-iPr_2C_6H_3OPO_3H) _4(phen)_2] (7), [Cu_2(2,6-iPr_2C _6H_3OPO_3H)_2(PyPz)_2(CH _3OH)_2] (8) and [Cu_2(2,4,6-iPr_3C _6H_2CH_2PO_3H)_2(DMPz) _2Cl_2]·(CH_3OH) (9) The molecular structures of 4-7 are grossly similar. The common structural features in these complexes are that the two metal centers are bridged by two bidentate [RPO _2(OH)]~- ligands generating a central eight-membered ring. Each of the metal centers also contains a chelating nitrogen ligand and a monodentate phosphonate or a phosphate ligand. In 5 and 6 other terminal ancillary ligands are also present. In compound 8, each of the two copper centers contains a monodentate [RPO_2(OH)]~- ligand along with a molecule of methanol. The two coppers are bridged by two monoanionic pyridylpyrazole ligands. The molecular structure of 9 is similar to that of 4-7. However, in 9 each of the two copper centers contain only terminal monodentate ligands in the form of two chlorides and a pyrazole. Magnetic studies on all of these copper complexes reveal an anti-ferromagnetic behavior at low temperatures. In addition, these complexes were found to be artificial nucleases and can convert supercoiled pBR322 DNA form I into nick form II in 1 min in the presence of an external oxidant through a hydrolytic and/or an oxidative pathway.