NEW 1,4,7,10-TETRAAZACYCLOTRIDECANE-11,13-DIONE LIGANDS APPENDED WITH ADDITIONAL DONOR(S) 8-METHYLQUINOLINE(S) - CRYSTAL-STRUCTURES AND CHARACTERIZATION OF THEIR COPPER(II) COMPLEXES

Two macrocyclic dioxotetraamine ligands 4-(quinolin-8-ylmethyl)-1,4,7,10-tetraazacyclotridecane-11,13-dione (H(2)L(1)) and 4,7-bis(quinolin-8-ylmethyl)-1,4,7,10-tetraazacyclotridecane-11,13-dione (H(2)L(2)) have been synthesized. The resulting dioxomacrocycles readily co-ordinate Cu2+ with concomitant double deprotonation of the ligands. The solution behaviour of the copper(II) complexes [CuL(1)] 1 and [CuL(2)] 2 has been studied by ESR, UV/VIS and cyclic voltammetric techniques. Remarkable red shifts were observed for the absorption band maxima of the electronic spectra of these copper(II) complexes (598 nm for 1 and 600 nm for 2) in comparison to that of unsubstituted (1,4,7,10-tetraazacyclotridecane-11,13-dione)copper(II) species (516 nm). The crystal structures of 1 and 2 (which crystallised in the form [(CuL(2))(2)]. 3H(2)O . MeCN) have been determined by X-ray diffraction analysis. Crystallographic data: 1, orthorhombic, space group Pcab. a = 16.260(3), b = 7.739(2), c = 27.530(9) Angstrom, Z = 8, R' = 0.061 for 2594 observed reflections with / > 3 sigma(/); 2, triclinic, space group <P(1)over bar>, a = 12.288(3), b = 14.734(4), c = 18.005(4) Angstrom, alpha = 102.26(2), beta = 104.26(2), gamma = 107.02(2)degrees, Z = 2, R' = 0.090 for 2284 observed reflections with / > 3 sigma(/). In complex 1, the Cu atom is five-co-ordinate and forms a distorted square pyramid in which N(11) of the quinoline pendant is at the apical site. The Cu-N(11) bond [2.266(3) Angstrom] is longer than the basal Cu-N bond lengths [average 1.985(3) Angstrom]. In complex 2, the Cu-II centre is also five-co-ordinate, with one of the quinoline pendants co-ordinating to (CuI)-I-I from the apical position and the other pendant remaining unco-ordinated.