title: Large Hexadecametallic {Mn(III) -Ln(III) } Wheels: Synthesis, Structural, Magnetic, and Theoretical Characterization.
abstract: The synthesis, gas sorption studies, magnetic properties, and theoretical studies of new molecular wheels of core type {Mn(III) 8 Ln(III) 8 } (Ln=Dy, Ho, Er, Y and Yb), using the ligand mdeaH2 , in the presence of ortho-toluic or benzoic acid are reported. From the seven wheels studied the {Mn8 Dy8 } and {Mn8 Y8 } analogues exhibit SMM behavior as determined from ac susceptibility experiments in a zero static magnetic field. From DFT calculations a S=16 ground state was determined for the {Mn8 Y8 } complex due to weak ferromagnetic Mn(III) -Mn(III) interactions. Ab initio CASSCF+RASSI-SO calculations on the {Mn8 Dy8 } wheel estimated the Mn(III) -Dy(III) exchange interaction as -0.1 cm(-1) . This weak exchange along with unfavorable single-ion anisotropy of Dy(III) /Mn(III) ions, however, led to the observation of SMM behavior with fast magnetic relaxation. The orientation of the g-anisotropy of the Dy(III) ions is found to be perpendicular to the plane of the wheel and this suggests the possibility of toroidal magnetic moments in the cluster. The {Mn8 Ln8 } clusters reported here are the largest heterometallic Mn(III) Ln(III) wheels and the largest {3d-4f} wheels to exhibit SMM behavior reported to date.
authors.affiliation: IITB-Monash Research Academy, IIT Bombay, Mumbai, 400076 (India).
authors.forename: Kuduva R
authors.initials: KR
authors.lastname: Vignesh
authors.affiliation: School of Chemistry, Monash University, Victoria, 3800 (Australia).
authors.forename: Stuart K
authors.initials: SK
authors.lastname: Langley
authors.affiliation: School of Chemistry, Monash University, Victoria, 3800 (Australia).
authors.forename: Boujemaa
authors.initials: B
authors.lastname: Moubaraki
authors.affiliation: School of Chemistry, Monash University, Victoria, 3800 (Australia). keith.murray@monash.edu.
authors.forename: Keith S
authors.initials: KS
authors.lastname: Murray
authors.affiliation: Department of Chemistry, Indian Institute of Technology Bombay, Powai, Mumbai, Maharashtra, 400 076 (India), Fax: (+91) 22-2576-7152. rajaraman@chem.iitb.ac.in.
authors.forename: Gopalan
authors.initials: G
authors.lastname: Rajaraman
keywords: Mn-Ln clusters; ab initio calculations; exchange-coupling; single-molecule magnets; wheel-shaped molecule