Synthesis, properties and structure of a novel macrocyclic ligand

A new ligand, 1,12,15-triaza-3,4:9,10-dibenzo-5,8-dioxacyclopentane, has be en synthesized and characterized as the hydrobromide salt, on the bases of analytical data, H-1 NMR, IR and FAB mass spectra. An X ray crystal structu re shows the ligand crystallizes in the rhombohedral system, space group R (3) over bar, with a = 35.194(1), b = 35.194(1), c = 10.397(1)Angstrom, gam ma = 120 degrees, V = 11152.6(1) Angstrom(3), Z = 18, refined to R = 0.061 for [120 observed reflections with I > 3 sigma(I) from 3392 independent ref lections. Stability constants for 1:1 complexes of transition metals and pr otonation constants for the ligand have been determined by potentiometric t itration in 95% ethanol (I = 0.1, (CH3)(4)NCl) at 25 degrees C.