Research Papers in Physics and Astronomy

 

Date of this Version

1-1-2020

Citation

Paulo S Costa et al 2020 J. Phys.: Condens. Matter 32 034001

Comments

Copyright ©2019 IOP Publishing. Used by permission.

CC BY-NC-ND

Abstract

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)].

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