Study On Synthesis, Structure And Properties Of Rare Earth Complexes With Bis-schiff Base Acyclic Polyether

Over the last few years, the rational design and prepare of rare earth coordination complexeshave attracted enormous attention for their distinctive architectures and possible applicationas functional materials. Particularly, lanthanide coordination complexes have potentpharmacological applications as anticancer, antiviral, anti-inflammatory, vasodilator andantimicrobial pharmaceuticals. One of the most studied applications is usage of the lanthanidemolecule complexes to address DNA/RNA by non-covalent binding and/or cleavage.The Schiff base compounds form a significant category of ligands that have beenuniversally discussed in coordination chemistry mostly because of their facile preparation andeasily adjustable steric, electronic, and catalytic properties. Many of compounds containingSchiff bases exhibit good physiological activity and pharmacological activity. The metalcomplexes with Schiff base bind to DNA would may be beneficial in the devise of such newcompounds, which can recognize specific sites or conformations of DNA. Hence, discusseson the interplay of small molecules, for instance the metal complexes, with DNA have been apet subject of researchers in the area of biological-inorganic chemistry.In this paper, a pentadentate Schiff base ligandbis(N-salicylidene)-3-oxapentane-1,5-diamine (H2L) has been prepared. Reaction of theshape-specific designed ligand with Ln(NO3)3·6H2O afforded eleven novel complexes,namely, Pr(L)(NO3)(DMF)(H2O)(1)，Sm(L)(NO3)(DMF)(H2O)(2)，[Eu(H2L)2(NO3)3]n(3)，Gd(L)(NO3)(DMF)(H2O)(4)， Tb2L2(NO3)2·2H2O (5)， Dy2L2(NO3)2·2H2O (6)，Ho2L2(NO3)2·2H2O (7)，Er2L2(NO3)2·2H2O (8)，Yb2L2(NO3)2·2H2O (9)，Lu2L2(NO3)2·2H2O(10)，Y2L2(NO3)2·2H2O (11). All ligand and complexes were characterized by elementalanalysis, IR, UV-Vis, NMR spectroscopy and X-ray crystallography. Single-crystal X-rayrevealed that: for complexes1to11, complex1,2and4are discrete mononuclear species thatlanthanide ion is nine-coordinated in the structure and forming a distorted tricapped trigonalprism geometry. Complex3is possessed a1-D ribbon framework constructed from anextended array of ten-coordinated Eu3+centers and the Schiff base ligands. Complex5to11are revealed as a centrosymmetric binuclear neutral entity, in which Ln(III) ion iseight-coordinated with the coordination surround of distorted square antiprism geometry.For the purpose of investigate the connection of the conformation and properties, thebiological properties of all Ln(III) complexes with the pentadentate ligand have beendiscussed. The DNA-binding properties have been studied by electronic absorption,fluorescence, and viscosity measurements. The results evidenced that both ligand andcomplexes bind to DNA via groove modes, and the affinities for DNA are more strongly in case of complexes when compared with ligands, which may due to:(i) the electrostatics ofpositively charged Ln3+ions cause an interaction with polyanionic DNA.(ii) The chargetransfer of coordinated ligands caused by the complexation of the central Ln3+ion, lead to thedecrease of the charge density of the plane conjugate system, that is conduce to insert.Moreover, the antioxidation of complexes also have been investigated. In antioxidant activityexperiments hydroxyl radicals (OH·) were generated in aqueous media through theFenton-type reaction and the superoxide radicals (O2·) were produced by the systemMET/VitB2/NBT. The results show that the data of IC50are all at10-5M level for the ligandand all Ln(III) complexes, accordingly. We compared the abilities of one present compoundsto scavenge radical with those of the classic natural antioxidants vitamin C and mannitol. Thedata of IC50are all at10-3M level for mannitol and vitamin C. The results imply that theLn(III) complexes have the preferable ability to scavenge hydroxyl radical (OH·) andsuperoxide radicals (O2·) than mannitol and vitamin C.