3d-4f-3d trinuclear complexes with di-maltol-polyamine ligands. Solid state structure and solution behaviour

The properties of two Cu(II) and Co(II) complexes with two maltol derivative ligands [L1 = N,N0-bis[(3- hydroxy-4-pyron-2-yl)methyl]-N,N0-dimethylethylendiamine (Malten) and L2 = 4,10-bis[(3-hydroxy-4- pyron-2-yl)methyl]-1,7-dimethyl-1,4,7,10-tetraazacyclododecane (Maltonis)] as binders for lanthanide cations [Eu(III) and Dy(III)], were investigated by means of single crystal X-ray diffraction and by UV– Vis experiments. [M(II)(H-2L)] species [Cu(H-2L1)] and [Co(H-2L2)] are able to stabilize one hard metal ion such as Eu(III) and Dy(III), giving rise to the formation of hetero-trinuclear complexes of {Ln(III)[M(II)(H-2L)]2}3+ general formula. The crystal structures of all the studied hetero-trinuclear species highlight that such systems are formed thanks to the synergy between the different stereochemical requirement of the transition metal (Cu(II) or Co(II)) and the different donor atoms set of the ligands. The suitable transition metal ion preorganizes the maltol units in the [M(II)(H-2L)] complexes for the binding of the hard Ln(III) metal, otherwise difficult to bind in water.