[Fe(μ-btzmp)2(btzmp)2](ClO4)2: a doubly-bridged 1D spin-transition bistetrazole-based polymer showing thermal hysteresis behaviour

Manuel Quesada, Huub Kooijman, Patrick Gamez, José Sánchez Costa, Petra J. van Koningsbruggen, Peter Weinberger, Michael Reissner, Anthony L. Spek, Jaap G. Haasnoot, Jan Reedijk

Research output: Contribution to journalArticlepeer-review


The reaction of btzmp (1,2-bis(tetrazol-1-yl)-2-methylpropane) with Fe(ClO4)2 generates a 1D polymeric species, [Fe(μ-btzmp)2(btzmp)2](ClO4)2, showing a steep spin transition (T½↑ = 136 K and T ½↓ = 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(µ-btzmp)2(btzmp)2](ClO4)2.

Original languageEnglish
Pages (from-to)5434-5440
Number of pages7
JournalDalton Transactions
Issue number46
Early online date4 Oct 2007
Publication statusPublished - 4 Oct 2007


  • ClO4
  • bistetrazole
  • thermal hysteresis
  • spin-transition


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