Molecular Nanomagnets of Fe(III)

Abstract

Two routes for preparing polymetallic clusters of iron have been investigated: the first strategy is to make molecular analogues of naturally occurring magnetic oxides using controlled hydrolysis and the second involves investigation of the coordination chemistry of salicylaldoxime (saoH2) and its derivatives R-saoH2 (where R=Me, Et, Ph). In total seventeen new complexes are reported. These are a family of heptadecametallic iron structures (1-6): Hpy[Fe17O16(OH)12(py)12Br4]Br4·8py·MeCN (1), (HPy)0.5[Fe17O16(OH)12(py)12Br4]Br3.5 (2), Hpy[Fe17O16(OH)12(py)12Br4]Br4·2(C3H6O)·1/2py·2H2O (3), [Fe17O16(OH)12(iso-quin)12Br3(H2O)3]Br4·6(iso-quin)·3(H2O) (4), [Fe17O16(OH)12(3,5-lut))12Br4]Br3·H2O (5), [Fe17O16(OH)12(beta-pic)12Br4]Br3 (6); dimetallic to octametallic cages stabilised with R-sao2- ligands: [HNEt3][Fe2(OMe)(Phsao) 2(Ph-saoH)2]·5MeOH (7), [Fe3O(Et-sao)(O2CPh)5(MeOH)2]·3MeOH (8), [Fe4(Mesao) 4(Me-saoH)4]·MeOH (9), [HNEt3]2[Fe6O2(Me-sao)4(SO4)2(OMe)4(MeOH)2] (10), [Fe8O3(Me-sao)3(tea)(teaH)3(O2CMe)3]·3MeOH (11), [Fe8O3(Et-sao)3(tea)(teaH)3(O2CMe)3]·3MeOH (12), [Fe8O3(Ph-sao)3(tea)(teaH)3(O2CMe)3]·4MeOH (13), [Fe6O2(OH)2(Et-sao)2(EtsaoH) 2(O2CPh)6].NEt3 (14), [HNEt3]2[Fe6O2(OH)2(O2CPh(Me)2)6(Et-sao)6]·2MeCN (15); a coordination polymer stablised with Me-sao2-: ([Fe6Na3O(OH)4(Mesao) 6(OMe)3(H2O)3(MeOH)6]·MeOH)n (16); a dodecamatallic cage stabilised with sao2-: [HNEt3]2[Fe12Na4O2(OH)8(sao)12(OMe)6(MeOH)10] (17); the first polymetallic transition metal cluster to be synthesised using microwave heating - an unusual octametallic cluster using saoH2, [Fe8O4(sao)8(py)4] (18). Studies of the magnetic properties of 1-18 show that 1-6 are high spin clusters with S=35/2, which can show long range magnetic order (LRMO) or super-paramagnetic blocking depending on their crystal symmetry; 7-17 exhibit spin ground states between S=0 and S=4; while 18 has a spin ground state of S=0 and represents an ideal Heisenberg antiferromagnet.