A new ligand H4Lox and its iron(III) complex as a platform for the development of heterotrimetallic complexes

The combination of multiple metal ions of different nature, in a single coordination compound, can provide a unique set of properties suitable for applications such as mimetization of the active site of enzymatic systems, development of new molecular magnetic materials and catalysts for photoinduced water splitting. Nonetheless, the preparation of heteromultimetallic complexes, in a controlled way, is a challenging task. In this work, we present a new ligand, H4Lox, designed as a platform for the synthesis of heterotrimetallic complexes. From H4Lox and its precursor H2L, two mononuclear iron(III) complexes, [Fe(L)]NO3·MeOH·2H2O (1) [Fe(H2Lox)]NO3·XH2O (2) were synthesized and fully characterized. The structure of 2 revealed a N2O2 vacant coordination site comprised by two phenolate oxygen atoms and two oxime nitrogen atoms. DFT calculations and ESI-MS data demonstrate that complex 2 can accommodate two additional metal ions, in a stable heterotrimetallic complex. The effect of the ortho substituents of the phenolate groups (CHO and CNOH) in the electronic states of 1 and 2, respectively, was evaluated by UV–Vis spectroscopy, cyclic voltammetry and DFT calculations. A free energy correlation was found between the calculated electrophilicity index ω and the experimental half wave potentials of 1, 2 and their analogous complex [Fe(bbpen-Me)]+ [33]. The electrophilicity index ω was used to estimate the FeIII/FeII redox potential of the hypothetical [FeZnCl2(Lox)Ga(tpa)]2+ complex.

From the new ligand H4Lox and its precursor H2L, two mononuclear iron(III) complexes, [Fe(L)]NO3·MeOH·2H2O (1) [Fe(H2Lox)]NO3·XH2O (2) were synthesized. The XRD structure of complex 2 revealed a N2O2 vacant coordination site. DFT calculations indicate that two additional metal ions can be accommodated by 2, in a stable heterotrimetallic complex [FeIIIZnIICl2(Lox)GaIII(tpa)]2+.Figure optionsDownload as PowerPoint slide