Studies On Synthesis And The Interaction With DNA Of Salen Rare Earth Complexes

Four Salen ligands were synthesized through condensation by aldehyde with vary diamine:L1=N1,N2-bis(naphthalen-1-ylmethylene-2-hydroxy)Prop-ane-1,2-Diamine, L2= N1, N2-bis(naphthalen-1-ylmethylene-2-hydroxy)Propane-1,3-Diamine, L3=N1,N6-bis(naphthale n -1-ylmethylene-2-hydroxy)benzene-1,4-Diamine, L4=N1,N2-bis(naphthalen -1-ylmethylene -2-hydroxy)ethane-1,3-Diamine. Via reactions between the four ligands and four rare earth elements ( Ln= Ce(Ⅲ), Eu(Ⅲ), Tb(Ⅲ), Yb(Ⅲ)), 16 Ln-Salen complexes were synthesized as a result. The interactions of all the complexes with Calf Thymus DNA were investigated by UV titration spectroscopy and viscosity measurements. Fluorescent properties of DNA-complex products were studied by fluorescence spectroscopy. The results suggested:1. Twelve Ln-Salen complexes bound to DNA via an intercalative mode, which 12 complexes were synthesized by reacting Ln elements (Ce(Ⅲ), Eu(Ⅲ), Tb(Ⅲ), Yb(Ⅲ)) with L1, L2 and L4, respectively. The results revealed a general pattern that as the atomic number of rare earth elements increased, the intercalative force gradually weakened. This could be attributed to the structure change of extra-nuclear electrons of rare earth elements.2. Interactions between four L3-Ln(Ln=Ce(Ⅲ), Eu(Ⅲ), Tb(Ⅲ), Yb(Ⅲ)) complexes wiht Calf Thymus DNA were investigated by UV spectroscopy and viscosity measurements. Results suggested that the four complexes still bound to DNA in an intercalative fashion. However, the intercalative forces did not decrease as the extra-nuclear electronic structure of rare earth elements increased. The possible explanation was that the intercalation of the complexes was not only related to the structure of extra-nuclear electrons of rare earth element, but also to the bridge groups.3. Interactions of complexes, which were synthesized by the four ligands with the same rare earth ions, with Calf Thymus DNA were compared. Results suggest that the strength of the interaction followed this order of ligands from strong to weak: L3> L1 >L2 >L4. It could be accounted for the relationship with the rigid plane of bridging groups and the alkaline of bridging groups.