Key indicators: single-crystal X-ray study; T = 293 K; mean (C-C) = 0.005 Å; R factor = 0.059; wR factor = 0.185; data-to-parameter ratio = 14.1.The title zwitterion,, C 16 H 11 ClN 2 O, is approximately planar, the dihedral angle between the benzene ring and naphthalene ring system is 1.55 (13) ; an intramolecular N-HÁ Á ÁO hydrogen bond stabilizes the planar conformation. In the crystal, -stacking between the benzene ring and the naphthalene ring system of adjacent molecules links the molecules into supramolecular chains running along the b axis, the centroid-centroid distance being 3.765 (2) Å . Related literature

Key indicators: single-crystal X-ray study; T = 273 K; mean (C-C) = 0.004 Å; R factor = 0.034; wR factor = 0.082; data-to-parameter ratio = 12.3. The CuII atom in the title compound, [Cu(C 16 H 10 ClN 2 O) 2 ], is located on an inversion center and is tetracoordinated by two N and two O atoms from two bidentate 1-[(E)-(2-chlorophenyl)diazenyl]naphthalen-2-olate ligands, forming a squareplanar complex. In the crystal, molecules are linked via weak C-HÁ Á ÁO and C-HÁ Á ÁCl hydrogen bonds, forming chains propagating along [010]. There are also -interactions present involving adjacent naphthalene rings [centroidcentroid distance = 3.661 (13) Å ]. Related literature Data collectionBruker APEXII CCD diffractometer 7327 measured reflections 2299 independent reflections 1979 reflections with I > 2(I) R int = 0.030