Copper(I) complexes bases on a new indazol-4,7-dione ligand

Two new isomeric ligands, 1-(1-((2,6-diisopropylphenyl)imino)ethyl)-1H- benzo[f]indazole-4,9-dione (L_a) and 2-(1-((2,6-diisopropylphenyl) imino)ethyl)-2H-benzo[f]indazole-4,9-dione (Lb), were synthesized and fully characterized as well the derivative copper complexes; [CuI(Lb)2] (ClO ₄) (1) homoleptic and [CuI(Lb(PPh₃)₂] (ClO ₄) (2) heteroleptic copper(I) complexes. The X-ray diffraction shows an irregular tetrahedral coordination around of metal in both monometallic complexes with little differences in Cu-N distances and N-Cu-N bite angles than involved the indazole ligand between two complexes. The proton spectra show a different variation in chemical shift relative to free ligand, which was discussed by steric and magnetic current effects of another coordinated ligand. The differences in the energy of metal-to ligand-charge-transfer (MLCT) and in redox potentials to Cu^II/CuI process in both complexes show the notorious influence of the phosphine which by back-donating effect, modified the energy of HOMO orbital centered in Cu atom. The coordinative and redox stability in solution was established for several days in non-coordinating solvent. However in acetonitrile the ligand substitution is very fast.