title: Amending the anisotropy barrier and luminescence behavior of heterometallic trinuclear linear [M(II) -Ln(III) -M(II) ] (Ln(III) =Gd, Tb, Dy; M(II) =Mg/Zn) complexes by change from divalent paramagnetic to diamagnetic metal ions.
abstract: The sequential reaction of a multisite coordinating compartmental ligand [2-(2-hydroxy-3-(hydroxymethyl)-5-methylbenzylideneamino)-2-methylpropane-1,3-diol] (LH4 ) with appropriate lanthanide salts followed by the addition of [Mg(NO3 )2 ]⋅6 H2 O or [Zn(NO3 )2 ]⋅6 H2 O in a 4:1:2 stoichiometric ratio in the presence of triethylamine affords a series of isostructural heterometallic trinuclear complexes containing [Mg2 Ln](3+) (Ln=Dy, Gd, and Tb) and [Zn2 Ln](3+) (Ln=Dy, Gd, and Tb) cores. The formation of these complexes is demonstrated by X-ray crystallography as well as ESI-MS spectra. All complexes are isostructural possessing a linear trimetallic core with a central lanthanide ion. The comprehensive studies discussed involve the synthesis, structure, magnetism, and photophysical properties on this family of trinuclear [Mg2 Ln](3+) and [Zn2 Ln](3+) heterometallic complexes. [Mg2 Dy](3+) and [Zn2 Dy](3+) show slow relaxation of the magnetization below 12 K under zero applied direct current (dc) field, but without reaching a neat maximum, which is due to the overlapping with a faster quantum tunneling relaxation mediated through dipole-dipole and hyperfine interactions. Under a small applied dc field of 1000 Oe, the quantum tunneling is almost suppressed and temperature and frequency dependent peaks are observed, thus confirming the single-molecule magnet behavior of complexes [Mg2 Dy](3+) and [Zn2 Dy](3+) .
authors.affiliation: Department of Chemistry, Indian Institute of Technology Kanpur, Kanpur-208016 (India) http://www.iitk.ac.in.
authors.forename: Sourav
authors.initials: S
authors.lastname: Das
authors.forename: K S
authors.initials: KS
authors.lastname: Bejoymohandas
authors.forename: Atanu
authors.initials: A
authors.lastname: Dey
authors.forename: Sourav
authors.initials: S
authors.lastname: Biswas
authors.forename: M L P
authors.initials: ML
authors.lastname: Reddy
authors.forename: Roser
authors.initials: R
authors.lastname: Morales
authors.forename: Eliseo
authors.initials: E
authors.lastname: Ruiz
authors.forename: Silvia
authors.initials: S
authors.lastname: Titos-Padilla
authors.forename: Enrique
authors.initials: E
authors.lastname: Colacio
authors.forename: Vadapalli
authors.initials: V
authors.lastname: Chandrasekhar
keywords: coordination chemistry; heterometallic complexes; luminescence; magnetic properties; photochemistry; single-molecule magnets