%0 Journal Article
%A Saalfrank, R. W.
%A Scheurer, A.
%A Bernt, I.
%A Heinemann, F. W.
%A Postnikov, A. V.
%A Schünemann, V.
%A Trautwein, A. X.
%A Alam, M. S.
%A Rupp, H.
%A Müller, P.
%T The FeIII[FeIII(L1)2]3 star-type single-molecule magnet
%J Dalton transactions
%V 23
%@ 1477-9226
%C London
%I Soc.
%M PreJuSER-51533
%P 2865 - 2874
%D 2006
%Z Record converted from VDB: 12.11.2012
%X Star-shaped complex [Fe(III)[Fe(III)(L1)2]3] (3) was synthesized starting from N-methyldiethanolamine H2L1 (1) and ferric chloride in the presence of sodium hydride. For 3, two different high-spin iron(III) ion sites were confirmed by Mössbauer spectroscopy at 77 K. Single-crystal X-ray structure determination revealed that 3 crystallizes with four molecules of chloroform, but, with only three molecules of dichloromethane. The unit cell of 3.4CHCl3 contains the enantiomers (delta)-[(S,S)(R,R)(R,R)] and (lambda)-[(R,R)(S,S)(S,S)], whereas in case of 3.3CH2Cl2 four independent molecules, forming pairs of the enantiomers [lambda-(R,R)(R,R)(R,R)]-3 and [lambda-(S,S)(S,S)(S,S)]-3, were observed in the unit cell. According to SQUID measurements, the antiferromagnetic intramolecular coupling of the iron(III) ions in 3 results in a S = 10/2 ground state multiplet. The anisotropy is of the easy-axis type. EPR measurements enabled an accurate determination of the ligand-field splitting parameters. The ferric star 3 is a single-molecule magnet (SMM) and shows hysteretic magnetization characteristics below a blocking temperature of about 1.2 K. However, weak intermolecular couplings, mediated in a chainlike fashion via solvent molecules, have a strong influence on the magnetic properties. Scanning tunneling microscopy (STM) and scanning tunneling spectroscopy (STS) were used to determine the structural and electronic properties of star-type tetranuclear iron(III) complex 3. The molecules were deposited onto highly ordered pyrolytic graphite (HOPG). Small, regular molecule clusters, two-dimensional monolayers as well as separated single molecules were observed. In our STS measurements we found a rather large contrast at the expected locations of the metal centers of the molecules. This direct addressing of the metal centers was confirmed by DFT calculations.
%K J (WoSType)
%F PUB:(DE-HGF)16
%9 Journal Article
%$ pmid:16751895
%U <Go to ISI:>//WOS:000238049000017
%R 10.1039/b515980f
%U https://juser.fz-juelich.de/record/51533