Two mononuclear copper(II) complexes, [CuL(CH3CN)(ClO4)]ClO4(1) and cis-[CuL(NCS)(2)]center dot 0.5C(4)H(8)O(2)(2) (L=2-[N,N-di (2-pyridylmethyl)aminomethyl]-6-aldehydo-4-methylphenol) have been synthesized and characterized by UV-Vis, FTIR, ESI-MS, elemental analysis and single crystal X-ray crystallography. Both 1 and 2 crystallize in a monoclinic system. Each copper(II) ion locates in a distorted octahedron geometry. As a tetradentate chelating ligand, the L coordinates to copper(II) ion via two pyridyl N atoms, one N atom of tertiary amine, and one phenol O atom. In 1, an acetonitrile molecule and a perchlorate anion also take part in coordination; while there are two cis-disposed NCS- ions in 2. CCDC: 938954, 1; 938955, 2.