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Abstract : The efficiency of the lanthanide ions to promote the hydrolysis of phosphate esters is amazing, particularly in comparison with biologically relevant transition metals or Lewis acids consisting of alkaline earth metals such as Ca (II) or Mg (II). Although several studies have demonstrated that the free lanthanide ions (hydrated) as efficient DNA cleaving agents, there are certain disadvantages in its use: salts solutions of LnIII become slightly unstable at pH above 7, tending to precipitate as hydroxides around pH 9, besides being toxic to biological systems, so, complexation of these ions become of extreme importance. Beyond the intrinsic characteristics of these metals, factors such as the coordination environment of these ions, contribute to form a thermodynamically stable system and highly efficient in catalysis of phosphate ester bonds of substrate model and hydrolysis of DNA, promoting lanthanide complexes to promising artificial nucleases. In this work we synthesized two new complexes of lanthanum with the ligand 2-bis[{(2-pyridylmethyl)-aminomethyl}-6-[N-(2-pyridylmethyl)aminomethyl)])-4-methyl-6-formylphenol) (H2L1), [La(L1)(NO3)2]. 0,25H2O (1A) and [La(L1)(NO3)2] .2CHCl3. 1,5H2O (1B) and a new terbium trinuclear complex with the ligand 2-[N-bis-(2-pyridylmethyl)aminomethyl]-4-methyl-6-[N-bis(2-hydroxy-2-oxoethyl)aminomethyl]phenol (H3L2), [Tb3(H3L2)2(NO3)2(H2O)4] NO3.3H2O.EtOH (2). The new complexes 1A, 1B and 2 were characterized by various techniques including, infrared spectroscopy, electron spectroscopy, potentiometric titration, ESI-MS, TGA, DSC and X-ray diffraction crystallography. The complexes were also tested in the activity of phosphatase front the hydrolysis of substrates: bis(2,4-dinitrophenyl)phosphate (2,4-bdnpp), 2,4-dinitrophenylphosphate and 2,4-dinitrophenyl phenyl phosphate - (2,4-bnppp) in homogeneous and in heterogeneous medium , with the immobilization of the complex 1A on silica 3-aminopropyl (Si3AP-1). These studies in homogeneous medium, revealed that complex 1A and 2 possess catalytic factors of about 19 thousand and 1,3 million times bigger compared to uncatalyzed reaction, respectively. We also emphasize that the complex 1A heterogeneous medium (Si3AP-1) presented an acceleration factor of 33 thousand times higher than the uncatalyzed reaction, can be considered a catalyst more efficient than the free complex and and with the advantage of being used several times without significant loss of its activity. |
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