Ferrocene functionalized enantiomerically pure Schiff bases and their Zn(II) and Pd(II) complexes: a spectroscopic, crystallographic, electrochemical and computational investigation

Salvador Celedon (1) , Paul Hamon (2) , Vania Artigas (1) , Mauricio Fuentealba (1) , Samia Kahlal (2) , David Carrillo (1) , Jean-Yves Saillard (2) , Jean-René Hamon (2) , Carolina Manzur (1)

1 PUCV - Pontificia Universidad Católica de Valparaíso
2 ISCR - Institut des Sciences Chimiques de Rennes

In this contribution, we describe the synthesis, spectroscopic and structural characterization, as well as the electrochemical behavior of a series of four chiral ferrocene-functionalized Schiff base compounds derived from enantiomerically pure (1R,2R)-(-)-1,2-diaminocyclohexane. The ferrocene enaminones 3 and 4 were obtained upon monocondensation of ferrocenoylacetone Fc-C(= O)CH2C(QO)R (R = CH3, 1; 4-C6H4OH, 2; Fc = (eta(5)-C5H5)Fe(eta(5)-C5H4)) with one amino group of the primary diamine. The two bimetallic complexes 5 and 6 were prepared via a one-pot three-components template procedure involving half-unit 3, 4-methoxysalicylaldehyde and tetrahydrated zinc(II) nitrate for 5, and half-unit 4, 4-formyl-3-hydroxybenzoic acid and palladium(II) acetate for 6. All the syntheses were carried out in refluxing ethanol and compounds 3-6 were isolated as thermally stable, air and moisture compatible colored solids in 71-83% yields. They were characterized by several analytical (EA, ESI-MS) and spectroscopic methods (H-1/C-13 NMR, FT-IR, UV-vis), including the molecular structures of 3 and 4 that were unequivocally established by single crystal X-ray diffraction analyses. Both crystallize in the orthorhombic non-centrosymmetric space group P2(1)2(1)2(1) with two (R,R)-(-)-chiral carbon atoms in the structures. Cyclic voltammetry showed that the greatest anodic shifts (270 mV) of the ferrocenyl Fe(II)/Fe(III) redox potentials are observed for the D-pi-A push-pull derivative 6. Beyond experimental characterization, DFT- and TDDFT-based theoretical analyses of the new chiral ferrocene-containing Schiff base complexes allow interpretation of their observed spectroscopic, structural and electronic features.

Domaines: Chimie

Salvador Celedon, Paul Hamon, Vania Artigas, Mauricio Fuentealba, Samia Kahlal, et al.. Ferrocene functionalized enantiomerically pure Schiff bases and their Zn(II) and Pd(II) complexes: a spectroscopic, crystallographic, electrochemical and computational investigation. New Journal of Chemistry, 2022, 46 (8), pp.3948-3960. ⟨10.1039/d1nj06106b⟩. ⟨hal-03592739⟩