Solid-State 67Zn NMR spectroscopic studies and ab initio molecular orbital calculations on a synthetic analogue of carbonic anhydrase

The tris(pyrazolyl)hydroborato zinc complexes Tp(But,Me)]ZnX (where X = Br, Cl, and OH) have been examined by low-temperature solid-state (67)Zn NMR spectroscopy. The value of the quadrupole coupling constant, Cq, for the zinc increased monotonically with the electronegativity of the bound substituent X, e.g., Br < Cl < OH. Calculations on the methylimidazole complex (MeImH)(3)Zn(OH)](+) as a model for the active site of carbonic anhydrase indicate that the computed electric field gradient tensor is in good agreement with the experimental and calculated values for Tp(But,Me)]ZnOH.