Crystal Structures and Magnetic Properties of Newly Synthesized Mono‐ and Dinuclear Cu II Schiff‐Base Complexes

Five Cu II Schiff‐base complexes, three mononuclear {[Cu( rslys H) · (H 2 O) 2 ] · 2H 2 O · ClO 4 ( 1 ); [Cu( rslys H)Cl] ( 2 ); [Cu( slys H)(H 2 O)Cl] ( 3 ) rslys and slys = 6‐amino‐2‐[(2‐hydroxybenzylidene)amino]hexanoate} and two dinuclear {[Cu 2 ( rslys H) 2 (CH 3 OH) 2 ] · (H 2 O) 2 (NO 3 ) 2 ( 4 ); [Cu 2 ( slys H) 2 (NO 3 ) 2 ] · (H 2 O) 3 ( 5 )}, are reported herein. These complexes have been synthesized via a facile “one‐pot” method in which the D / L ‐ and L ‐lysine Schiff‐base ligands are generated in situ. Various spectroscopic techniques and single‐crystal X‐ray diffraction were used in compound characterization. The X‐ray diffraction studies revealed that complexes 1 – 3 are mononuclear; further, 4 and 5 are dinuclear in which two Cu II centers are phenolate‐bridged. Complexes 1 , 2 and 3 are structurally similar, according to the nuclearity and the coordination environment around the metal center involving a tridentate D ‐ or L ‐lysine‐derived Schiff‐base ligand. But the crystallographic packing is different, owing to the different counterions and number of solvent molecules present in the crystals. Compounds 1 and 2 are racemic due to the co‐existence of chiral D ‐ and L ‐lysine‐based Schiff‐base ligands. These copper(II) complexes give 2‐D hydrogen‐bonded networks and are racemic overall. Compound 3 is chiral, containing only the L ‐lysine‐derived ligand in which a cylindrical 1‐D hydrogen‐bonded structure is observed in the solid state. Both 4 (achiral) and 5 (chiral) reveal 3‐D hydrogen‐bonded networks. A strong antiferromagnetic coupling interaction was observed by variable‐temperature magnetic susceptibility measurements; this interaction is likely mediated through the phenolate bridge between the two Cu II centers in 4 and 5 .