Synthesis of the {Co[(6-amino-6-(4-aminobenzyl)-1,4,8, 11-tetra-azacyclotetradecane)]-[PO4]}, a potential phosphate-binding site for molecular recognition

The preparation of Co(NH3)(5)(PO4) and Co(L-0)(PO4) [L-0: 6-amino-6-(4-amin obenzyl)-1,4,8,11-tetra-azacyclotetradecane] is reported. P-31 NMR resonanc es for the two complexes are pH dependent, and are shifted downfield compar ed to that of unbound phosphate at the same pH. Co(NH3)(5)(PO4): pH 12.0, d elta(p) 8.17 ppm; pH 7.2, delta(p) 7.50 ppm; Co(L-0)(PO4): pH 7.2, delta(p) 7.20 ppm. Co(L-0)(PO4) is a remarkable robust complex. Over a period of fi ve weeks at 25 degrees C, pH 7.2, less than 1% hydrolysis (aquation) occurr ed, so that k(1) < 2E - 15 s(-1). (C) 1998 Elsevier Science S.A. All rights reserved.