Molecular Nanomagnets of Fe(III)
Date
2008Author
Gass, Ian Andrew
Metadata
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.