Electronic Structures and Reduction Potentials of Cu(II) Complexes of [N,N′-Alkyl-bis(ethyl-2-amino-1-cyclopentenecarbothioate)] (Alkyl=Ethyl, Propyl, and Butyl)

Abstract

Copper(II) complexes of N, [alkyl=ethyl (L2), propyl (L3), and butyl(L4)] ligands have been synthesized and characterized. Analytical data for all three complexes show 1:1 copper-ligand stoichiometry. Wellresolved EPR spectra were recorded in toluene, benzene, and methylene chloride solutions at room temperature and in glassy toluene or toluene-methylene chloride mixtures in the range 20-150 K. The superhyperfine pattern unambiguously demonstrates coordination of two nitrogen atoms to copper; and the spin-Hamiltonian parameters [CuL2, g ʈ =2.115, A ʈ =187¥10 -4 cm -1 ; CuL3, g ʈ =2.128, A ʈ =165¥10 -4 cm -1 ; CuL4, g ʈ =2.138, A ʈ =147¥10 -4 cm -1 ] are as expected for a CuN 2 S 2 coordination core. Quasi-reversible electrochemical behavior was observed in methylene chloride: the Cu(II)/Cu(I) reduction potentials increase from -1.17 V (E°vs Ag/AgNO 3 ) for CuL2 to -0.74 V for CuL4, indicating greater stabilization of Cu(I) in CuL4. Taken together, these data demonstrate that lengthening the N,N¢-alkyl chain distorts the planar CuN 2 S 2 core (CuL2) toward a flattened tetrahedral geometry (CuL4).

Electrochemical Behaviour and Electronic Absorption of the Metal β- Diketonates Complexes

“…The reduction peak corresponds to the first electron transfer of Cu(II) Cu(I) process, which is overlapped with the reduction peak of fluorinated β-diketone unit. The E pc and E pa values were observed in agreement with the reported results [15][16][17]. In compression, the reduction potentials of Cu(II) exhibits more negative potential value than Cu(OAc) 2 Figure 4).…”