Metallohydrolase biomimetics with catalytic and structural flexibility.
The structural and functional properties of zinc(ii) complexes of two nitrogen rich polydentate ligands, HTPDP = 1,3-bis(bis-pyridin-2-ylmethylamino)propan-2-ol and HTPPNOL = N,N,N'-tris-(2-pyridylmethyl)-1,3-diaminopropan-2-ol, are compared. HTPDP is a hepta-dentate ligand with four pyridyl groups attached to a 1,3-diaminopropan-2-ol backbone while HTPPNOL contains only three pyridyl groups. In reactions with Zn(ClO4)2, HTPDP forms a dinuclear zinc compound [Zn2(TPDP)(OAc)](ClO4)2, 1. On the other hand, mononuclear [Zn(HTPPNOL)](ClO4)2, 2, and tetranuclear [Zn4(TPPNOL)2(OAc)3](ClO4)3, 3, complexes were isolated with the ligand HTPPNOL. Kinetic measurements with the substrate bis(2,4-dinitrophenyl)phosphate (BDNPP) revealed that compound 1 (kcat= 31.4 × 10-3min-1) is more reactive than 3 (kcat= 7.7 × 10-3min-1) at pH = 8.5, whilst the mononuclear compound 2 is inactive. Compound 1 displays a typical steady-state kinetic behaviour, while compound 3 exhibits steady-state behaviour only ∼120 s after starting the reaction, preceded by a burst-phase.31P NMR studies confirm that 1 can promote the hydrolysis of both ester bonds in BDNPP, generating the monoester DNPP and inorganic phosphate in the process. In contrast, DNPP is not a substrate for 3. The crystal structure of the complex formed by 3 and DNPP reveals the formation of a tetranuclear zinc complex [Zn4(TPPNOL)2(DNPP)2](ClO4)2, 4, in which the phosphate moiety of DNPP adopts an unusual tridentate μ-η1:η1:η1coordination mode.
Laboratório de Ciências Químicas, Universidade Estadual do Norte Fluminense, 28013-602, Campos dos Goytacazes/RJ, Brazil. adolfo@uenf.br.
Luisa L
LL
Mendes
Anorganisch-Chemisches Institut, Universität Heidelberg, Im Neuenheimer Feld 270, 69120 Heidelberg, Germany.
Daniel
D
Englert
Laboratório de Ciências Químicas, Universidade Estadual do Norte Fluminense, 28013-602, Campos dos Goytacazes/RJ, Brazil. adolfo@uenf.br.
Christiane
C
Fernandes
School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia. schenk@uq.edu.au.
Lawrence R
LR
Gahan
School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD 4072, Australia. schenk@uq.edu.au.
Gerhard
G
Schenk
Laboratório de Ciências Químicas, Universidade Estadual do Norte Fluminense, 28013-602, Campos dos Goytacazes/RJ, Brazil. adolfo@uenf.br.
Adolfo
A
Horn
D040761:Biomimetic Materials / Q000737:chemistry*; D032701:Biomimetics; D002384:Catalysis; D056831:Coordination Complexes / Q000737:chemistry*; D018360:Crystallography, X-Ray; D006868:Hydrolysis; D007700:Kinetics; D008024:Ligands; D008958:Models, Molecular; D010755:Organophosphates / Q000737:chemistry*; D010744:Phosphoric Monoester Hydrolases / Q000737:chemistry*; D020005:Propanols / Q000737:chemistry; D011725:Pyridines / Q000737:chemistry; D015032:Zinc / Q000737:chemistry*
D056831:Coordination Complexes; D008024:Ligands; D010755:Organophosphates; D020005:Propanols; D011725:Pyridines; C546103:bis(2,4-dinitrophenyl) phosphate; D010744:Phosphoric Monoester Hydrolases; D015032:Zinc