Manipulation of the molecular spin crossover transition of Fe(H2B(pz)2)2(bipy) by addition of polar molecules

Paulo S. Costa, Guanhua Hao, Alpha T. N'Diaye, Lucie Routaboul, Pierre Braunstein, Xin Zhang, Jian Zhang, Thilini K. Ekanayaka, Qin Yin Shi, Vicki Schlegel, Bernard Doudin, Axel Enders, P. A. Dowben

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6 Scopus citations


The addition of various dipolar molecules is shown to affect the temperature dependence of the spin state occupancy of the much studied spin crossover Fe(II) complex, [Fe{H2B(pz)2}2(bipy)] (pz = pyrazol-1-yl, bipy = 2,2′-bipyridine). Specifically, the addition of benzimidazole results in a re-entrant spin crossover transition, i.e. the spin state starts in the mostly low spin state, then high spin state occupancy increases, and finally the high spin state occupancy decreases with increasing temperature. This behavior contrasts with that observed when the highly polar p -benzoquinonemonoimine zwitterion C6H2(..NH2)2(..O)2 was mixed with [Fe{H2B(pz)2}2(bipy)], which resulted in locking [Fe{H2B(pz)2}2(bipy)] largely into a low spin state while addition of the ethyl derivative C6H2(..NHC2H5)2(..O)2 did not appear to perturb the spin crossover transition of [Fe{H2B(pz)2}2(bipy)].

Original languageEnglish (US)
Article number034001
JournalJournal of Physics Condensed Matter
Issue number3
StatePublished - 2020


  • X-ray absorption spectroscopy
  • dipolar heteromolecular molecular interactions
  • re-entrant transition
  • spin crossover metal organic molecules

ASJC Scopus subject areas

  • General Materials Science
  • Condensed Matter Physics


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