Coordination complexes with the redox active tetrathiafulvalene based imino-pyrazine ligand: syntheses, a radical cation salt, crystal structures and electrochemistry

Abstract

The tetrathiafulvalene based 2-immino-pyrazine derivative (TTF-CHN-2-pyz) (1) was synthesized and characterized. Its radical cation salt (1˙⁺PF₆⁻) was prepared as single crystals by electrocrystallisation. 1˙⁺PF₆⁻ crystallizes in the triclinic P space group. Four 1 : 2 bis(hexafluoroacetylacetonate)M(II) complexes coordinated with 1 were prepared (M = Mn for 2, M = Co for 3, M = Cu for 4 and M = Zn for 5). Complex 2 crystallizes in the monoclinic C2/c space group, complexes 4 and 5 crystallize in the triclinic space group P. Two pyrazine N atoms from two different donors are coordinated in cis configuration for 2 and trans configuration for 4 and 5 to the metallic ion of M(hfac)₂ (hfac⁻=hexafluoroacetylacetonate anion). The manganese atom adopts a pseudo-compressed octahedral geometry while the copper and the zinc ions adopt axially elongated octahedral geometries. Both crystal packing structures and electrochemical properties are appropriate for their potential use as starting molecular bricks for conducting and magnetic materials.