NEW MACROCYCLIC DIOXOTETRAAMINES BEARING 2-METHYLFURAN PENDANT(S) - SYNTHESIS, PROPERTIES AND CRYSTAL-STRUCTURE OF THE COPPER(II) COMPLEXES

A series of new macrocyclic dioxotetraamine ligands having 2-methylfur an pendent(s), 4-(2-methylfuran)-1 ,4,7,10-tetraazacyclotridecane-11,1 3-dione (H2L1), furan)-1,4,7,10-tetraazacyclotridecane-11,13-dione (H2 L2), furan)-1,4,8,11-tetraazacyclotetradecane-5,7-dione (H2L3) and fur an)-1,4,8,11-tetraazacyclotetradecane-5,7-dione (H2L4), have been synt hesized and characterized. The solution behaviours of the copper(II) c omplexes of the four ligands have been studied with ESR, cyclic voltam metry (CV) and UV-vis techniques. A red-shift has been observed for th e maximum absorption band of the electronic spectra of CuL1, CuL3 and CuL2, CuL4 in comparison to those of the corresponding unsubstituted c opper(II) complexes CuL01 and CuL02, respectively. Electrochemical stu dies suggest that the introduction of 2-methylfuran pendant(s) to the macrocyclic dioxotetraamines destabilizes the Cu-III ion comparing wit h the unsubstituted species for both of the two kinds of macrocycles ( 13-membered and 14-membered macrocycles). The copper(II) complex of H2 L2 has been isolated as a single crystal and the crystal structure det ermined by X-ray diffraction analysis. It is interesting that the comp lex has an N-meso chiral nitrogen configuration. The Cu-II atom is in five coordination environment with four basal nitrogen atoms and one a xial oxygen atom from H2O, and it adopts a distorted square pyramidal configuration. (C) 1997 Elsevier Science Ltd.