Constructing clusters with enhanced magnetic properties by assembling and distorting Mn-3 building blocks
Résumé
The reaction of Mn(ClO4)(2)center dot 6H(2)O with Naphth-saoH(2) (Naphth-saoH(2) = 2-hydroxy-1-napthaldoxime) in pyridine (py) forms the complex [(Mn3O)-O-III(Naphth-sao)(3)(py)(3)](ClO4)center dot 0.5py(1 center dot 0.5py) in very good yields. Reaction of 1 with NaO2CPh in EtOH produces the complex [(Mn6O2)-O-III(Naphth-sao) 6( O2CPh)(2)(EtOH)(6)]center dot[(Mn6O2)-O-III(Naphth-sao)(6)(O2CPh)(2)(EtOH)(4)]center dot 2.5Et(2)O center dot 0.5H(2)O(2 center dot 2.5Et(2)O center dot 0.5H(2)O). Further reaction of complex 2 with 1 equivalent of both NaN3 and Mn(ClO4)(2)center dot 6H(2)O in MeOH produces the complex [(Mn2Mn6O2)-Mn-II-O-III(Naphth-sao)(6)(N-3)(6)(MeOH)(8)]center dot 10MeOH (3 center dot 10MeOH) that displays an S approximate to 0 ground state. Ligand substitution of Naphth-saoH(2) with Me-saoH(2) in CH2Cl2-MeOH for the latter complex (Me-saoH(2)=2-hydroxyphenylethanone oxime) forms the complex[(Mn2Mn6O2)-Mn-II-O-III(Me-sao)(6)(N-3)(6)(MeOH)(8)]center dot 10MeOH (4 center dot 10MeOH) that displays an S = 7 ground state with U-eff=44.6 K. In all four complexes the main building block is the triangular {(Mn3O)-O-III(R-sao)(3)} unit (R = Naphth for 1, 2 and 3; R = Me for 4). The ligand substitution in 3 triggers a structural distortion in the [Mn-6] sub-core as observed by the increased (Mn-N-O-Mn) torsion angles in 4, switching the interactions from antiferro-to ferromagnetic, dramatically changing the ground-state of the octanuclear complexes from S = 0 to 7