CRYSTAL STRUCTURE AND PROPERTIES OF A COPPER(II) COMPLEX OF AN 18-MEMBERED MACROCYCLIC LIGAND WITH N,N' -DICARBOXYLIC ACID ARMS

Abstract

CuL 5H2O (H2L = 1, 15-diaza-3, 4; 12, 13-dibenzo-5, 8, 11 -trioxacyclo-octadecane-N,N′-diacetic acid) crystallized from water. Its crystal structure was determined by X-ray diffraction analysis and refined in space group Pnma, a = 20.1784(11), b = 15.8745(9), c = 8.9266(5)Å, V = 2859.4(3)Å3, Z = 4, ⋋(MOKα) = 0.71073, RW . = 0.0294 for 1822 observed reflection [I > 2[sgrave](I)]. The copper atom is surrounded by two nitrogen atoms, two oxygen atoms from the carboxyl groups in the ligand and one oxygen atom from a coordinated water to form a distorted square pyramidal arrangement. The three ether oxygen atoms in the cycle have no contact with the copper ion. The stability constant for the 1 :1 complex of copper(II) and protonation constants for the ligand have been determined by potentiometric titration in water (I = 0.1, KNO3) at 25°C. Electronic spectra, conductivity measurements, thermal analysis, and the EPR of the complex are discussed in terms of the crystal structure.