Toward a magnetostructural correlation for a family of Mn6 SMMs |
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Authors: | Milios Constantinos J Inglis Ross Vinslava Alina Bagai Rashmi Wernsdorfer Wolfgang Parsons Simon Perlepes Spyros P Christou George Brechin Euan K |
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Institution: | School of Chemistry, The University of Edinburgh, West Mains Road, Edinburgh, EH9 3JJ, UK. |
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Abstract: | We have structurally and magnetically characterized a total of 12 complexes based on the Single-Molecule Magnet (SMM) MnIII6O2(sao)6(O2CH)2(MeOH) 4] (1) (where sao2- is the dianion of salicylaldoxime or 2-hydroxybenzaldeyhyde oxime) that display analogous structural cores but remarkably different magnetic behaviors. Via the use of derivatized oxime ligands and bulky carboxylates we show that it is possible to deliberately increase the value of the spin ground state of the complexes Mn6O2(Me-sao)6(O2CCPh3)2(EtOH)4] (2), Mn6O2(Et-sao)6(O2CCMe3)2(EtOH)5] (3), Mn6O2(Et-sao)6(O2CPh2OPh)2(EtOH)4] (4), Mn6O2(Et-sao)6(O2CPh4OPh)2(EtOH)4(H2O)2] (5), Mn6O2(Me-sao)6(O2CPhBr)2(EtOH)6] (6), Mn6O2(Et-sao)6(O2CPh)2(EtOH)4(H2O)2] (7), Mn6O2(Et-sao)6{O2CPh(Me)2}2(EtOH)6] (8), Mn6O2(Et-sao)6(O2C11H15)2(EtOH)6] (9), Mn6O2(Me-sao)6(O2C-th)2(EtOH)4(H2O)2] (10), Mn6O2(Et-sao)6(O2CPhMe)2(EtOH)4(H2O)2] (11), and Mn6O2(Et-sao)6(O2C12H17)2(EtOH)4(H2O)2] (12) (Et-saoH2 = 2-hydroxypropiophenone oxime, Me-saoH2 = 2-hydroxyethanone oxime, HO2CCPh3 = triphenylacetic acid, HO2CCMe3 = pivalic acid, HO2CPh2OPh = 2-phenoxybenzoic acid, HO2CPh4OPh = 4-phenoxybenzoic acid, HO2CPhBr = 4-bromobenzoic acid, HO2CPh(Me)2 = 3,5-dimethylbenzoic acid, HO2C11H15 = adamantane carboxylic acid, HO2C-th = 3-thiophene carboxylic acid, HO2CPhMe = 4-methylbenzoic acid, and HO2C12H17 = adamantane acetic acid) in a stepwise fashion from S = 4 to S = 12 and, in-so-doing, enhance the energy barrier for magnetization reorientation to record levels. The change from antiferromagnetic to ferromagnetic exchange stems from the "twisting" or "puckering" of the (-Mn-N-O-)3 ring, as evidenced by the changes in the Mn-N-O-Mn torsion angles. |
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