The X-ray crystal structures of two cation-distortion isomers of [Cu(dpyam)(2)(ONO)](NO3) (1) and [Cu(dpyaM)(2)(ONO)](ClO4) (2) complexes are reported and shown to contain an asymmetric cis-distorted CuN4O2 chromophore. In I the copper atom and the asymmetrically bonded nitrito group lie on a crystallographic C-2 axis. The nitrito group is clearly disordered about the C2 axis giving a square pyramidal cis-distorted octahedral (4+1+1*) chromophore rather than a pseudo regular cis-distorted octahedral chromphore. In 2 a distortion of the CuN4O2 chromophore towards a square pyramidal (4+1 +1*) geometry is also present, but with well-ordered and less asymmetric nitrito group. The polycrystalline ESR spectra of 1 and 2 are temperature independent suggesting that both complexes appear to be near the static distortion limit of the fluxional CuN4O2 chromophore geometry. The electronic reflectance spectra of I and 2 involve two bands at approximately 14 700 and 9800 cm (-1) for 1, and approximately 14 970 and 10000cm(-1) for 2 and relate to the underlying static CuN4O2 (4+1+1*) chromophore geometry. (C) 2002 Elsevier Science B.V. All rights reserved.