Helical dinuclear 3d metal complexes with bis(bidentate) [S,N] ligands: synthesis, structural and computational...

Area of Science:

• Coordination Chemistry
• Supramolecular Chemistry
• Materials Science

Background:

• Development of novel ligands for metal complex synthesis.
• Exploration of metal-ligand bonding and structural motifs.
• Investigation of magnetic and electronic properties of transition metal complexes.

Purpose of the Study:

• Synthesize and characterize novel diprotic bis(β-thioketoimine) ligands and their metal complexes.
• Investigate the structural, electronic, and magnetic properties of dinuclear and monometallic complexes.
• Elucidate the nature of metal-sulfur and metal-nitrogen bonding using computational methods.

Main Methods:

• Synthesis of a bis(β-thioketoimine) ligand precursor (H₂2) using Lawesson's reagent.
• Coordination chemistry involving lithiation and reaction with metal(II) chlorides (Fe, Co, Zn).
• Structural characterization by X-ray diffraction, and electronic/magnetic properties by DFT, magnetic studies, and cyclic voltammetry.

Main Results:

• Formation of homoleptic dinuclear complexes [M₂(μ-2)₂] with a double-stranded helicate structure and tetrahedral metal centers.
• Observation of significant inter-strand face-face π-stacking leading to a helical twist of ~70°.
• DFT calculations indicate stronger, more covalent M-S bonds than M-N bonds; Fe(II) and Co(II) complexes exhibit high-spin tetrahedral centers with accessible redox activity.

Conclusions:

• Successful synthesis of novel dinuclear and monometallic β-thioketoiminate complexes.
• The dinuclear complexes adopt a unique double-stranded helicate structure stabilized by π-stacking.
• Stronger M-S bonding and accessible redox properties highlight the potential of these complexes in coordination chemistry and materials science.