Structural studies of the [tris(midazolyl)phosphine]metal nitrate complexes {[Pim(Pr(i),Bu(t))]M(NO3)}+ (M = Co, Cu, Zn, Cd, Hg): Comparison of nitrate-binding modes in synthetic analogues of carbonic anhydrase

Clare Kimblin, Vincent J. Murphy, Tony Hascall, Brian M. Bridgewater, Jeffrey B. Bonanno, Gerard Parkin

Research output: Contribution to journalArticle

80 Scopus citations

Abstract

X-ray diffraction studies on a series of cationic divalent metal nitrate complexes supported by the tris(1-isopropyl-4-tert-butylimidazolyl)phosphine ligand, {[Pim(Pr(i),Bu(t))]M(NO3)}+ (M = Co, Cu, Zn, Cd, Hg), demonstrate that the nitrate ligand coordination mode is strongly dependent upon the metal. With the exception of that for the Hg(II) derivative, the nitrate ligand coordination modes correlate with the activities of metal-substituted carbonic anhydrases, such that the only M(II)-carbonic anhydrases which exhibit significant activity, i.e., the Zn and Co species, are those for which the {[Pim(Pr(i),Bu(t))]M(NO3)}+ complexes possess strongly asymmetric nitrate ligands. This trend supports the notion that access to a unidentate, rather than a bidentate, bicarbonate intermediate may be a critical requirement for significant carbonic anhydrase activity. Interestingly, the nitrate coordination modes in the series of group 12 complexes, {[Pim(Pr(i),Bu(t))]M(NO3)}+ (M = Zn, Cd, Hg), do not exhibit a monotonic periodic trend: the bidenticity is greater for the cadmium complex than for either the zinc or mercury complexes. Since Hg(II)-carbonic anhydrase is inactive, the correlation between nitrate coordination mode and enzyme activity is anomalous for the mercury complex. Therefore, it is suggested that the inactivity of Hg(II)-carbonic anhydrase may be a consequence of the reduced tendency of the mercury center in Hg(II)-carbonic anhydrase to bind water.

Original languageEnglish (US)
Pages (from-to)967-974
Number of pages8
JournalInorganic Chemistry
Volume39
Issue number5
DOIs
StatePublished - Mar 6 2000
Externally publishedYes

ASJC Scopus subject areas

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry

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