A new macrocyclic tetraamine (cyclen) having a strategically appended alcohol group, 1-(2-hydroxyethyl)1,4,7,10-tetraazacyclododecane (8), has been synthesized. The functionalized cyclen (8) forms a 1:1 ZnL complex (5) at pH ca. 6. The X-ray crystal study has disclosed a five-coordinate structure with the undeprotonated alcohol OH coordinating at an apical position. Crystals of 5.(ClO4)(2) (C10H24N4O9Cl2Zn) are monoclinic, space group P2(1/n) with a = 8.813 (2) Angstrom, b = 23.662 (2) Angstrom, c = 8.814 (2) Angstrom, beta = 90.21 (1)degrees, V = 1838.0 (5) Angstrom(3), Z = 4, R = 0.073, and R(w) = 0.125. The potentiometric pH titration of 5 showed dissociation of a proton with a pK(a) value of 7.60 +/- 0.02 at 25 degrees C and I = 0.10 (NaClO4). From the NMR and competitive anion-binding studies, the structure of the deprotonated species was assigned to be a OH--bound ZnL-OH- complex (11). During unsuccessful attempts to isolate the deprotonated species, we have obtained a trimeric phosphate complex, (ZnL-O-)(3)P=O, as its PF6- salts (15.(PF6)(3)(H2O)(1.5)) from pH 9.5 aqueous solution containing 5.(ClO4)(2), K2HPO4, and NH4PF6. ermined as the trimer of C10H25N4O17/6P4/3F6Zn) are trigonal, space group R ($) over bar 3 with a = 23.353 (3) Angstrom, c = 17.527 (5) Angstrom, V = 8278 (2) Angstrom(3), Z = 18, R = 0.070, and R(w) = 0.112.