Diastereomers of copper(II) complexes exhibiting difference in coordination geometry by R- or S-1-phenylethylamine ligands in the solid state and structural conversion of crystals into solutions

Crystal structures and electronic and circular dichroism (CD) spectra of copper(II) complexes, meso trans-[CuL2(R-phenea)(S-phenea)] (1) and optically actiue trans-[CuL2(S-phenea)(2)] (2) (L = 5,5-diphenylhydantoinate and phenea = 1-phenylethylamine), are reported. The present complexes are the first diastereomers that are different in the degree of tetrahedrally distorted square planar [CuN4] coordination geometries, depending on chirality of phenea ligands. In the solid states, the distortion angles theta(im) and theta(am) defined by the angles which Cu-N(L) and Cu-N(phenea) made with the mean coordination plane are theta(im) = 12.5degrees and theta(am) = 10.1degrees for 1 and theta(im) = 6.6degrees and theta(am) = 8.4degrees for 2, respectively. Considerably large distortion of the [CuN4] chromophore of I is attributed to alternate arrangement (methyl-phenyl-(Cu)-methyl-phenyl) of substituent groups in phenea ligands, in contrast with symmetric arrangement (methyl-phenyl-(Cu)-phenyl-methyl) for 2. The diffuse reflectance spectra of 1 and 2 in the solid states exhibit a peak at 17 500 and 18 500 cm (-1), respectively, and the lower wavenumber peak of 1 is consistent with larger distorted [CuN4] chromophore. In contrast, the absorption spectra of I and 2 in chloroform solutions exhibit a peak at 16 100 and 16 000 cm - 1, respectively. Then. the similar spectra reflect structural similarity between I and 2 in solutions. For the first time, we have successfully estimated the distortion angles in solution to be theta(im) = 13degrees and theta(am) = 11degrees by angular overlap model on the basis of analyses of the CD spectrum of 2. (C) 2003 Elsevier Science B.V. All rights reserved.