Examination of cobalt, nickel, copper and zinc(II) complex geometry and binding affinity in aqueous media using simple pyridylsulfonamide ligands

Congreve, A.; Kataky, R.; Knell, M.; Parker, D.; Puschmann, H.; Senanayake, K.; Wylie, L.

Abstract

The sixteen neutral ML2 complexes of Co, Ni, Cu and Zn(II) with the p-toluenesulfonamide and trifluoromethylsulfonamide derivatives of 2-aminomethylpyridine (L-1, L-2) and its 6-Me homologue (L-3, L-4) have been characterised by low temperature X-ray crystallography (100-120 K). Complexes of Co and Zn invariantly adopted a distorted tetrahedral geometry and whilst Cu(II) complexes of L-2, L-3 and L-4 also took up a distorted tetrahedral geometry, that with L-1 was square planar. A database survey of the distortion from limiting tetrahedral/square planar geometry has been carried out, aided by a simple geometric analysis. The trifluoromethylsulfonamide ligands (L-2 and L-3) were less basic, e.g. log K-1 7.51(3) for L-2 vs. 12.23(6) for L-1 (80% MeOH/H2O) and afforded a weaker ligand field, exemplified by the position of the visible d-d transition in Cu(II) complexes and the ease of reduction of the Cu(II) centre: E-1/2 values (MeCN vs. Ag/AgCl) are -430, -137, + 55 and -240 mV for Cu(L-1)(2), Cu(L-2)(2), Cu(L-3)(2) and Cu(L-4)(2). Ligand protonation and stepwise formation constants have been measured for L-1-L-3 and derived species distribution diagrams reveal that for complexes with L-2 and L-3, the predominant species present at pH 7.4 when zinc was in the nanomolar range was ZnL2.

Citation

Congreve, A., Kataky, R., Knell, M., Parker, D., Puschmann, H., Senanayake, K., & Wylie, L. (2003). Examination of cobalt, nickel, copper and zinc(II) complex geometry and binding affinity in aqueous media using simple pyridylsulfonamide ligands. New Journal of Chemistry, 27(1), 98-106

• Journal Article Type: Article
• Publication Date: 2003
• Journal: New Journal of Chemistry
• Print ISSN: 1144-0546
• Electronic ISSN: 1369-9261
• Publisher: Royal Society of Chemistry
• Peer Reviewed: Peer Reviewed
• Volume: 27
• Issue: 1
• Pages: 98-106
• Public URL: https://durham-repository.worktribe.com/output/1595161