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Structural Variations and Formation Constants of First‐Row Transition Metal Complexes of Biologically Active Aroylhydrazones
Author(s) -
Armstrong Claire M.,
Bernhardt Paul V.,
Chin Piao,
Richardson Des R.
Publication year - 2003
Publication title -
european journal of inorganic chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.667
H-Index - 136
eISSN - 1099-0682
pISSN - 1434-1948
DOI - 10.1002/ejic.200390146
Subject(s) - chemistry , ligand (biochemistry) , potentiometric titration , transition metal , metal , pyridine , octahedron , titration , divalent , crystallography , chelation , stereochemistry , imine , metal ions in aqueous solution , hydrazone , inorganic chemistry , medicinal chemistry , crystal structure , ion , organic chemistry , biochemistry , receptor , catalysis
Iron chelators of the 2‐pyridinecarbaldehyde isonicotinoylhydrazone (HPCIH) class show high potential for the treatment of iron overload diseases. In the present study, selected first‐row transition metal (from Mn to Zn) complexes with HPCIH and 2‐pyridinecarbaldehyde (4′‐aminobenzoyl)hydrazone (HPCAH) were synthesised and characterised. Crystallography reveals that HPCAH exclusively forms bis complexes with divalent transition metals, with each ligand coordinating meridionally through its pyridine‐N, imine‐N and carbonyl‐O atoms, forming distorted octahedral cis ‐MN 4 O 2 complexes. Complexes of HPCIH were more varied and unpredictable, with metal/ligand ratios of 1:1, 1:2, 2:2 and 3:2 obtained with different metal ions. The isonicotinoyl ring N‐atom in HPCIH was found to be an effective ligand, and this resulted in the varied metal/ligand ratios observed. The formation constants of divalent metal complexes with HPCIH were determined by potentiometric titrations and the values obtained were consistent with similar tridentate ligands and with the Irving−Williams order. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003)