Reaction of Cu(ClO 4 ) 2 .6H 2 O with l-glutamic acid (l-glu) in 1:1 or 1:2 molar ratio at pH 5 gave only the complex [Cu(l-glu)-(H 2 O)].H 2 O, whose crystal structure revealed that the copper atom was coordinated in square-planar geometry, with the amino nitrogen and the carboxylate oxygen of l-glu, the side-chain carboxylate oxygen of a neighboring l-glu, and the oxygen of a water molecule in the equatorial positions. Weak coordination of two additional glutamate oxygens to both axial positions complete a distorted octahedron. The [Cu(l-glu)(H 2 O)] units linked by coordination of the side-chain carboxylate group form an infinite left-handed single helix; the use of d-glu in place of l-glu gives a right-handed helix, indicating that the glu enantiomerism determines the helicity. Thermogravimetric and differential thermal analyses of the complex showed reversible desorption of just two water molecules at 95-130 o C, whose behavior was examined by ESR and circular dichroism spectral and powder X-ray diffraction methods in solid state. The crystals obtained from the reaction of Cu(II) ion with dl-glu showed spontaneous resolution.