Synthesis, structure, and physicochemical properties of dinuclear NiII complexes as highly efficient functional models of phosphohydrolases.
As metal ions are present in the catalytic sites of several enzymes, attention has been focused on the synthesis and characterization of metal complexes able to act as biomimetic functional and structural models for these systems. In this study, a novel dinuclear NiII complex was synthesized, [Ni2(L2)(OAc)2(CH3CN)]BPh4 (2) (HL2=2-[N-(2-(pyridyl-2-yl)ethyl)(1-methylimidazol-2-yl)amin omethyl]-4-methyl-6-[N-(2-(imidazol-4-yl)ethyl)amino methyl]phenol), employing a new unsymmetrical dinucleating ligand containing N,O-donor groups as a model for hydrolases. Complex 2 was characterized by a variety of techniques including: elemental analysis, infrared and UV-vis spectroscopies, molar conductivity, electrochemistry, potentiometric titration, magnetochemistry, and single-crystal X-ray diffractometry. The structural and magnetochemical data of 2 allow us to consider this complex as a structural model for the active site of the ureases, as previously reported for [Ni2(L1)(OAc)2(H2O)]ClO4.H2O (1) (HL1=2-[N-bis-(2-pyridylmethyl)aminomethyl]-4-methyl-6-[N-(2-pyridylmethyl)aminomethyl] phenol). The characterization of complexes 1 and 2 (mainly by X-ray diffraction and potentiometric titration) led us to study their reactivities toward the hydrolysis of the substrate bis(2,4-dinitrophenyl)phosphate (2,4-BDNPP). These studies revealed that complexes 1 and 2 show the best catalytic activity reported so far, with acceleration rates 8.8x10(4) and 9.95x10(5) times faster, respectively, than the uncatalyzed hydrolysis of 2,4-BDNPP. Catalytic activity of 2 on 2,4-DNPP showed that the monoester is hydrolyzed 27 times slower than the 2,4-BDNPP diester under identical experimental conditions. Therefore, 1 and 2 can undoubtedly be considered highly efficient functional models of the phosphohydrolases.
Greatti
Alessandra
A
Laboratório de Bioinorgânica e Cristalografia (LABINC), Departamento de Química, Universidade Federal de Santa Catarina, 88040-900 Florianópolis, Santa Catarina, Brazil.
Scarpellini
Marciela
M
Peralta
Rosely A
RA
Casellato
Annelise
A
Bortoluzzi
Adailton J
AJ
Xavier
Fernanado R
FR
Jovito
Rafael
R
de Brito
Marcos Aires
MA
Szpoganicz
Bruno
B
Tomkowicz
Zbigniew
Z
Rams
Michal
M
Haase
Wolfgang
W
Neves
Ademir
A
D018360:Crystallography, X-Ray; D009682:Magnetic Resonance Spectroscopy; D008958:Models, Molecular; D015394:Molecular Structure; D009532:Nickel / Q000737:chemistry*; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry*
D009532:Nickel; D010744:Phosphoric Monoester Hydrolases