title: Effect of Ligand Substitution around the Dy(III) on the SMM Properties of Dual-Luminescent Zn-Dy and Zn-Dy-Zn Complexes with Large Anisotropy Energy Barriers: A Combined Theoretical and Experimental Magnetostructural Study.
abstract: The new dinuclear Zn(II)-Dy(III) and trinuclear Zn(II)-Dy(III)-Zn(II) complexes of formula [(LZnBrDy(ovan) (NO3)(H2O)](H2O)·0.5(MeOH) (1) and [(L(1)ZnBr)2Dy(MeOH)2](ClO4) (3) (L and L(1) are the dideprotonated forms of the N,N'-2,2-dimethylpropylenedi(3-methoxysalicylideneiminato and 2-{(E)-[(3-{[(2E,3E)-3-(hydroxyimino)butan-2-ylidene ]amino}-2,2-dimethylpropyl)imino]methyl}-6-methoxyphenol Schiff base compartmental ligands, respectively) have been prepared and magnetostructurally characterized. The X-ray structure of 1 indicates that the Dy(III) ion exhibits a DyO9 coordination sphere, which is made from four O atoms coming from the compartmental ligand (two methoxy terminal groups and two phenoxido bridging groups connecting Zn(II) and Dy(III) ions), other four atoms belonging to the chelating nitrato and ovanillin ligands, and the last one coming to the coordinated water molecule. The structure of 3 shows the central Dy(III) ion surrounded by two L(1)Zn units, so that the Dy(III) and Zn(II) ions are linked by phenoxido/oximato bridging groups. The Dy ion is eight-coordinated by the six O atoms afforded by two L(1) ligands and two O atoms coming from two methanol molecules. Alternating current (AC) dynamic magnetic measurements of 1, 3, and the previously reported dinuclear [LZnClDy(thd)2] (2) complex (where thd = 2,2,6,6-tetramethyl-3,5-heptanedionato ligand) indicate single molecule magnet (SMM) behavior for all these complexes with large thermal energy barriers for the reversal of the magnetization and butterfly-shaped hysteresis loops at 2 K. Ab initio calculations on 1-3 show a pure Ising ground state for all of them, which induces almost completely suppressed quantum tunnelling magnetization (QTM), and thermally assisted quantum tunnelling magnetization (TA-QTM) relaxations via the first excited Kramers doublet, leading to large energy barriers, thus supporting the observation of SMM behavior. The comparison between the experimental and theoretical magnetostructural data for 1-3 has allowed us to draw some conclusions about the influence of ligand substitution around the Dy(III) on the SMM properties. Finally, these SMMs exhibit metal- and ligand-centered dual emissions in the visible region, and, therefore, they can be considered as magnetoluminescent bifunctional molecular materials.
authors.affiliation: Laboratoire de Chimie de Coordination, 205, route de Narbonne, Toulouse, 31077, France.
authors.forename: Jean Pierre
authors.initials: JP
authors.lastname: Costes
authors.affiliation: Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada , Av. Fuentenueva S/N, 18071 Granada ( Spain ).
authors.forename: Silvia
authors.initials: S
authors.lastname: Titos-Padilla
authors.affiliation: Departamento de Química Aplicada, Facultad de Química, Universidad del País Vasco, UPV/EHU , Paseo Manuel Lardizabal, No. 3, 20018, Donostia-San Sebastián, Spain.
authors.forename: Itziar
authors.initials: I
authors.lastname: Oyarzabal
authors.affiliation: Department of Chemistry, Indian Institute of Technology-Bombay , Powai, Mumbai-400076, India.
authors.forename: Tulika
authors.initials: T
authors.lastname: Gupta
authors.affiliation: Laboratoire de Chimie de Coordination, 205, route de Narbonne, Toulouse, 31077, France.
authors.forename: Carine
authors.initials: C
authors.lastname: Duhayon
authors.affiliation: Department of Chemistry, Indian Institute of Technology-Bombay , Powai, Mumbai-400076, India.
authors.forename: Gopalan
authors.initials: G
authors.lastname: Rajaraman
authors.affiliation: Departamento de Química Inorgánica, Facultad de Ciencias, Universidad de Granada , Av. Fuentenueva S/N, 18071 Granada ( Spain ).
authors.forename: Enrique
authors.initials: E
authors.lastname: Colacio