Heterometallic Zn(II)–Ln(III)–Zn(II) Schiff Base Complexes with Linear or Bent Conformation—Synthesis, Crystal Structures, Luminescent and Magnetic Characterization

A series of racemic, heteronuclear complexes [Zn(2)Nd(ac)(2)(HL)(2)]NO(3)·3H(2)O (1), [Zn(2)Sm(ac)(2)(HL)(2)]NO(3)·3CH(3)OH·0.3H(2)O (2), [Zn(2)Ln(ac)(2)(HL)(2)]NO(3)·5.33H(2)O (3–5) (where HL is the dideprotonated form of N,N′-bis(5-bromo-3-methoxysalicylidene)-1,3-diamino-2-propanol, ac = acetate ion, and Ln = Eu (3), Tb (4), Dy (5), respectively) with an achiral multisite coordination Schiff base ligand (H(3)L) were synthesized and characterized. The X-ray crystallography revealed that the chirality in complexes is centered at lanthanide(III) ions due to two vicinally located μ-acetato-bridging ligands. The presented crystals have isoskeletal coordination units but they crystallize in monoclinic (1, 2) or trigonal crystal systems (3–5) with slightly different conformation. In 1 and 2 the Zn(II)–Ln(III)–Zn(II) coordination core is linear, whereas in isostructural crystals 3–5 the chiral coordination cores are bent and lie on a two-fold axis. The complexes 1, 3–5 show a blue emission attributed to the emission of the ligand. For Zn(II)(2)Sm(III) complex (2) the characteristic emission bands of f-f* transitions were observed. The magnetic properties for compounds 1, 4 and 5 are characteristic for the paramagnetism of the corresponding lanthanide(III) ions.