Chemistry of azopyrimidines - Synthesis, spectral characterization, electrochemistry and X-ray crystal structure of bis[2-(arylazo)pyrimidine] complexes of copper(I)

2-(Arylazo)pyrimidines (aapm, 3) have been synthesized by condensing nitros oaromatics with 2-aminopyrimidine. They yield cationic bis-chelated complex es with copper(I), Cu(aapm)(2)(+) and are isolated as perchlorate salts. Th e complexes are 1:1 electrolytes in MeOH and exhibit intense MLCT transitio ns in the visible region. The N=N stretch in copper(I) complexes shows a la rge shift to lower frequency (approx. 1315 cm(-1)) from the free ligand val ue (approx. 1425 cm(-1)) due to d(Cu)-->pi*(aapm) back bonding. The complex es show highly resolved symmetrical H-1 NMR spectra. In MeOH the Cu(aapm)(2 )(2+)/Cu(aapm)(2)(+) couple appears at E-1/2 at approx. 0.7 V versus SCE at 298 K. The structure has been confirmed by X-ray crystallography. (C) 1999 Elsevier Science Ltd. All rights reserved.