Rhodamine Salicylaldehyde Hydrazone Dy(Iii) Complexes: Fluorescence And Magnetism

Three new dysprosium(III) complexes [Dy-2(HL1-o)(2)(L-1)(NO3)(3)] [Dy(NO3)(5)]center dot 1.5ACE center dot 0.5Et(2)O (1) [Dy(L-1)(3)]center dot 2.5MeOH center dot MeCN (2), and [Dy(L-2)(3)]center dot MeOH center dot MeCN (3) (HL1 = rhodamine B salicylaldehyde hydrazine, HL2 = rhodamine B 3-methylsalicylaldehyde hydrazine) were synthesized and characterized. Purple complex 1 contains two ring-open ligands HL1-o and shows fluorescence of the rhodamine amide moiety, whereas yellow complexes 2 and 3 are comprised of ring-dose ligands (L-1/2)(-) and display fluorescence of the salicylaldehyde Schiff base part. For 2 and 3, Dy(III) ions are nine coordinated by the six oxygen and three nitrogen atoms of three chelate (L-1/2)(-) ligands, but the arrangements of the three ligands are different owing to the methyl substituent on HL2. There are three short Predominant DY-O-phenoxy bonds in 2 and 3. The largest O-phenoxy-DY-O-phenoxy angle is 148.64(17)degrees for 2 and 89.63(13)degrees for 3. Magnetic studies reveal that complex 2 is a field-induced single-molecule magnet (U-eff = 104.2 K under a dc magnetic field of 2000 Oe), and 3 exhibits only a magnetic relaxation behavior owing to the quantum tunneling of magnetization (QTM). Furthermore, ab initio calculations illustrate that the disposition of predominant DY-O-phenoxy bonds affects the magnetic anisotropy of the Dy(III) ions and relaxation processes of complexes 2 and 3.