title: Grafting derivatives of Mn6 single-molecule magnets with high anisotropy energy barrier on Au111 surface.
abstract: We study the magnetic properties of two new functionalized single-molecule magnets belonging to the Mn 6 family (general formula [Mn (III)6O2(R-sao)6(O2C-th)2L(4-6)], where R=H (1) or Et (2), HO2C-th=3-thiophene carboxylic acid, L=EtOH, H2O and saoH2 is salicylaldoxime) and their grafting on the Au(111) surface. Complex 1 exhibits spin ground-state S=4, as the result of ferromagnetic coupling between the two antiferromagnetic Mn (III) 3 triangles, while slight structural changes in complex 2, switch the dominant magnetic exchange interactions from anti- to ferromagnetic, enhancing the spin ground-state to S=12 and, consequently, the effective energy barrier for the relaxation of magnetization. Direct-current and alternating-current magnetic susceptibility measurements show that the functionalized complexes preserve the main magnetic properties of the corresponding not-functionalized Mn 6 clusters (i.e., total spin value and magnetic behavior as a function of temperature), though a reduction of the anisotropy barrier is observed in complex 2. For both complexes, the -O2C-th functionalization allows the direct grafting on Au(111) surface by liquid-phase deposition. X-ray photoemission spectroscopy demonstrates that the stoichiometry of the molecular cores is preserved after grafting. Scanning tunneling microscopy (STM) reveals a sub-monolayer distribution of isolated clusters with a slightly higher coverage for complex 1. The cluster stability in the STM images and the S-2p energy positions demonstrate, for both derivatives, the strength of the grafting with the gold surface.
authors.affiliation: Dipartimento di Fisica, Universita di Modena e Reggio Emilia, Modena, Italy. moro.fabrizio@unimore.it
authors.forename: F
authors.initials: F
authors.lastname: Moro
authors.forename: V
authors.initials: V
authors.lastname: Corradini
authors.forename: M
authors.initials: M
authors.lastname: Evangelisti
authors.forename: V
authors.initials: V
authors.lastname: De Renzi
authors.forename: R
authors.initials: R
authors.lastname: Biagi
authors.forename: U
authors.initials: U
authors.lastname: del Pennino
authors.forename: C J
authors.initials: CJ
authors.lastname: Milios
authors.forename: L F
authors.initials: LF
authors.lastname: Jones
authors.forename: E K
authors.initials: EK
authors.lastname: Brechin