Synthesis and characterization of enantiopure copper(II) complexes using chiral bidentate ligands.

Chiral copper(ii) complexes of the types [Cu(II)(R/S-ppme)(3)](ClO(4))(2) and [Cu(II)(R/S-ppme)(2)(SO(4))] have been synthesized by reactions of Cu(ClO(4))(2).6H(2)O and CuSO(4).5H(2)O with R/S-ppme in methanol under aerobic conditions (R/S-ppme = (R/S)-(+/-)-1-phenyl-N-(pyridine-2-ylmethylene)ethanamine). All complexes were isolated and characterized by X-ray crystallography and circular dichroism (CD): (Lambda)-[Cu(II)(R-ppme)(3)](ClO(4))(2) (1), (Delta)-[Cu(S-ppme)(3)](ClO(4))(2).H(2)O (2), (Delta)-[Cu(II)(R-ppme)(2)(SO(4))].4CH(3)OH (3), and (Lambda)-[Cu(II)(S-ppme)(2)(SO(4))].4CH(3)OH (4). 1 and 2 with ClO(4)(-) anions are formed as tris(R/S-ppme) copper(ii) complexes, while 3 and 4 with SO(4)(2-) are formed as bis(R/S-ppme) copper(ii) complexes. The structures of 1 with R-ppmes and 4 with S-ppmes show the same absolute configurations (Lambda). In contrast, 2 with S-ppmes and 3 with R-ppmes exhibit Delta configurations. In the electron paramagnetic resonance (EPR) spectra of 1 and 3, both compounds demonstrate z-axis elongated structures. The CD spectra of 1 and 2 show Cotton effects in an enantiomeric pattern; those of 3 and 4 also display the same effects.