Selective complexation of 3d metal(II) ions with multidentate and chiral isomers derived from condensation of 2-pyridinecarboxaldehyde with triethylenetetramine

Abstract

Condensation of 2-pyridinecarboxaldehyde with a stoichiometric amount of triethylenetetramine in isopropyl alcohol yields a mixture of at least two products, a Schiff dibase L1 and a cyclization product with two imidazolidine rings L2, and possibly a Schiff monobase with one imidazolidine ring L3. The 3d metal(ii) salts, Mn(SCN)2, MnCl2, CuBr2, MnI2 and ZnBr2, react selectively with L1 or L2 in this mixture solution to produce Mn(L2)(NCS)21, Mn(L2)Cl22, [Cu(L2)Br]Br·H2O 3, [Mn(L1)]I 24, and [Zn(L1)][ZnBr4] 5, respectively. The presence of the two imidazolidine rings in the coordinated ligand L2 of 1-3 generates two chiral carbon centers. The Mn(ii) ion coordinates stereo-selectively to the [R,R] or [S,S] form of the L2 in hexa-coordinate Mn(ii) compounds 1 and 2, whereas the Cu(ii) ion coordinates with the meso [R,S] form of L2 in 3. © The Royal Society of Chemistry 2009.