In the present study, the water-oxidizing activity of nickel(II) phthalocyanine-tetrasulfonate tetrasodium (1), which is a stable Ni(II) complex under moderate conditions, was investigated. The role of Ni oxide in water oxidation as a true catalyst was investigated. The electrodes after water oxidation by both the complex and Ni salt were analyzed and a relation was proposed between the decomposition of the Ni complex and water oxidation. On the surface of the electrode, there are some areas without any detectable nanoparticles; thus, the detection of such Ni oxides on the surface of the electrode is not easy in the first seconds of the reaction, even using some of the usual methods such as Scanning Electron Microscopy or electrochemical analysis. Such experiments indicated that a precise analysis is necessary to reject the role of nanoparticles in the presence of Ni phthalocyanine under water oxidation. The findings also showed that under water-oxidation conditions and in the presence of the complex, Ni oxide is a good candidate for a true catalyst.
Two butterfly-shaped Dy 4 and Zn 2 Dy 2 complexes displaying slow relaxation of magnetization have been synthesized from a new methyl substituted o -vanillin based ligand, enlarging the scope for finding better SMMs.
This paper describes the synthesis, and structural and spectroscopic characterizations of two doubly bridged dicopper(II) complexes, [Cu2(μ-H2L)(μ-OMe)](ClO4)4·2H2O (1) and [Cu2(μ-L)(μ-OH)](ClO4)2 (2), with a binucleating ligand (HL) derived from the Schiff base condensation of DFMP and N,N-dimethyldipropylenetriamine, and their biomimetic catalytic activities were related to CAO and phenoxazinone synthase using 3,5-di-tert-butylcatechol and o-aminophenol (OAPH), respectively, as model substrates. Structural studies reveal that the major differences in these structures appear to be from the distinct roles of the tertiary amine groups of the ligands, which are protonated in 1, whereas it coordinates the metal centers in 2. Magnetic studies disclose that two copper(II) centers are strongly antiferromagnetically coupled with slightly different J values, which is further interpreted and discussed. They exhibited very different biomimetic catalytic activities; whereas 2 is an efficient catalyst, complex 1 showed somewhat lower substrate oxidation. The higher reactivity in 2 is rationalized by the strong involvement of the tertiary amine group of the Schiff base ligand, where the substrate oxidation is favored because of the transfer of protons from the substrate to the tertiary amine group, showing the importance of the functional groups in proximity to the bimetallic active site. Emphasis was also given to probing the binding mode of the substrate using an electronically deficient tetrabromomocatechol (Br4CatH2) and the isolated compound [Cu6(μ-HL)2(μ-OH)2(Br4Cat)4](NO3)2·4H2O (3) which suggests that monodentate asymmetric binding of 3,5-di-tert-butylcatechol and OAPH occurs during the course of the catalytic reaction.