Functionalised 1,10-phenanthroline metallocatalysts as models for hydrolytic metalloenzymes

Abstract

The synthesis of three new 1,10-phenanthroline derivatives is reported: 2-(N-methyldodecylamino)methyl-9-(hydroxymethyl)-1,10-phenanthroline (1), 2-(N,N-dimethylamino)methyl-9-(hydroxymethyl)-1,10-phenanthroline (2), and 2-(N-methyldodecylamino)methyl-1,10-phenanthroline (3). The esterolytic activities of the complexes 1–M^II and 3–M^II in the presence of cationogenic micelles and of 2–M^II in pure buffer toward the substrates p-nitrophenyl picolinate (PNPP), p-nitrophenyl octanoate (PNPO), and p-nitrophenyl dodecanoate (PNPD) have been investigated. The lipophilic ligand 1 in mixed micelles forms only 1 : 1 complexes with bivalent metal ions and the order of ligand activation is Zn^II > Co^II > Cd^II > Ni^II, while its water soluble analogue 2 forms both 1 : 1 complexes and 2 : 1 complexes. The order of ligand activation for 2 is also different: Co^II > Ni^II≈ Zn^II > Cd^II. The metallosurfactant 3, lacking the nucleophilic hydroxy group, is 25 times less active than 1–Zn^II. For the hydrolysis of PNPP catalysed by 1–Zn^II, a detailed kinetic analysis is given.