title: [Fe(mu-btzmp)2(btzmp)2](ClO4)2: a doubly-bridged 1D spin-transition bistetrazole-based polymer showing thermal hysteresis behaviour.
abstract: The reaction of btzmp (1,2-bis(tetrazol-1-yl)-2-methylpropane) with Fe(ClO4)2 generates a 1D polymeric species, [Fe(mu-btzmp)2(btzmp)2](ClO4)2, showing a steep spin transition (T(1/2) / =136 K and T(1/2) / =133 K) with a 3 K thermal hysteresis. The crystal structure at 100 and 200 K reveals that, in contrast to other bistetrazole based spin-transition systems such as [Fe(endi)3](BF4)2 and [Fe(btzp)3](ClO4)2, the present compound has only two ligands bridging the metallic centres, while the other two coordination positions are occupied by two mono-coordinated (non-bridging) btzmp ligands. This peculiarity confers an unprecedented crystal packing in the series of 1D bistetrazole based polymers. The change in spin state is accompanied by an order/disorder transition of the ClO4* counterion. A careful examination of the structural changes occurring upon the spin transition indicates that this order/disorder is most likely affected by the modification of the [tetrazole-centroid]-ND-Fe angle (which is typical of bistetrazole spin-transition materials). Apart from X-ray analysis, also magnetic susceptibility, Mössbauer and UV-vis spectroscopies have been used to characterise the HS and the LS states of [Fe(mu-btzmp)2(btzmp)2](ClO4)2.
authors.affiliation: Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, PO Box 9502, 2300-RA, Leiden, The Netherlands.
authors.forename: Manuel
authors.initials: M
authors.lastname: Quesada
authors.forename: Huub
authors.initials: H
authors.lastname: Kooijman
authors.forename: Patrick
authors.initials: P
authors.lastname: Gamez
authors.forename: José
authors.initials: J
authors.lastname: Sánchez Costa
authors.forename: Petra J
authors.initials: PJ
authors.lastname: van Koningsbruggen
authors.forename: Peter
authors.initials: P
authors.lastname: Weinberger
authors.forename: Michael
authors.initials: M
authors.lastname: Reissner
authors.forename: Anthony L
authors.initials: AL
authors.lastname: Spek
authors.forename: Jaap G
authors.initials: JG
authors.lastname: Haasnoot
authors.forename: Jan
authors.initials: J
authors.lastname: Reedijk
mesh_terms: D018360:Crystallography, X-Ray; D005290:Ferric Compounds / Q000737:chemistry*; D008280:Magnetics; D008958:Models, Molecular; D010472:Perchlorates / Q000138:chemical synthesis / Q000737:chemistry; D011108:Polymers / Q000138:chemical synthesis / Q000737:chemistry; D011407:Propane / Q000031:analogs & derivatives* / Q000138:chemical synthesis; D013056:Spectrophotometry, Ultraviolet; D015204:Spectroscopy, Mossbauer; D013777:Tetrazoles / Q000138:chemical synthesis / Q000737:chemistry*
chemical_list: D005290:Ferric Compounds; D010472:Perchlorates; D011108:Polymers; D013777:Tetrazoles; D011407:Propane