Spectroscopic Studies and X-ray Structural of Dinuclear Lanthanide (III) Complexes Derived from N'-(2-hydroxy-3-methoxybenzylidene) Nicotinohydrazide

Abstract

Two Schiff bases (H₂L), derived from o-vanillin and nicotinic hydrazide, and its complexes with some lanthanides (Y, Ce, Yb, Pr, Gd and Tb) have been synthesized. These compounds have been characterized by means of elemental analysis, UV–Vis spectroscopy, FTIR spectroscopy, ¹H and ¹³C NMR (for H₂L), molar conductance and room temperature magnetic measurements. The compounds are found isostructural and are formulated as {[(Z)(<i>η</i>²-OOCH₃)Ln](<i></i>-L)₂[Ln(<i>η</i>²-OOCH₃)(Z)]} (Z = H₂O for Ln = Y, Ce, Pr, Gd or Tb and Z = OS(CH₃)₂for Ln =Yb). The two ligand molecules act in their dideprotonated forms through one azomethine nitrogen atom, one phenoxo oxygen atom and one iminolate oxygen atom. The two Ln (III) ions are bridged by two phenoxo oxygen atoms, forming a dinuclear complex. Single crystal X-ray analysis of the ytterbium complex has revealed the nature of the structure {[(OS(CH₃)₂)(<i>η</i>²-OOCH₃)Yb](<i></i>-L)₂[Yb(<i>η</i>²-OOCH₃)(OS(CH₃)₂)]} (3). The complex crystallizes in the monoclinic space group C2/c with cell parameters of <i>a</i> = 13.0391(6) Å, <i>b</i> = 15.1199(6) Å, <i>c</i> = 20.7239(7) Å, <i>β</i> = 105.671(2)°, <I>V</I> = 3933.8(3) ų, <I>Z</I> = 4, <I>R</I>₁ = 0.025, <i>wR</i>₂ = 0.65. The ytterbium atoms are eight-coordinated, and their coordination polyhedron are best described as a square antiprismatic geometry. The aromatic rings of the ligand molecule are twisted with dihedral angle of 29.23 (1)° between their mean planes.