TU LogoTechnische Universität Wien

Cooperativity in spin crossover materials as ligand’s responsibility – investigations of the Fe(II) – 1,3-bis((1H-tetrazol-1-yl)methyl)bicycle [1.1.1]pentane system

Magnetic susceptibility of [Fe(ppditz)3]X2, X = BF4−, ClO4−, and PF6− in the solid state between 10 K–300 K and its single crystal structure

Criteria for a technologically relevant spin crossover (SCO) material include temperature and abruptness. A series of Fe(II) – 1,3-bis((1H tetrazol-1-yl)methyl)bicyclo[1.1.1]pentane SCO complexes with various anions (BF4, ClO4, and PF6) designed using a structure–property based concept is reported. All complexes feature abrupt SCO-behavior with T1/2 between 170 K and 187 K. These materials demonstrate that without stabilizing the effects of incorporated solvents or a hydrogen bond-network, the observed cooperativity during high-spin–low-spin transition is anion independent and originates only from the rigidity and internal strain of the propellane-moiety in the ligand. Spectroscopy and structural investigations of these materials are supported by quantum chemical calculations.

 „Cooperativity in spin crossover materials as ligand’s responsibility – investigations of the Fe(II) – 1,3-bis((1H-tetrazol-1-yl)methyl)bicycle [1.1.1]pentane system“, C. Knoll, D. Müller, M. Seifried, G. Giester, J. Welch, W. Artner, K. Hradil, M. Reissner, P. Weinberger, Dalton Trans., 2018, 47, 5553–5557
http://dx.doi.org/10.1039/c8dt00781k

Halogenated Alkyltetrazoles for the Rational Design of FeII Spin-Crossover Materials: Fine-Tuning of the Ligand Size

Magnetic susceptibility of [Fe(2‐Cl‐2Tz)6](BF4)2 and its crystal structures throughout the magnetic transition

1-(3-Halopropyl)-1H-tetrazoles and their corresponding FeII spin-crossover complexes have been investigated in a combined experimental and theoretical study. Halogen substitution was found to positively influence the spin transition, shifting the transition temperature about 70 K towards room temperature. Halogens located at the w position were found to be too far away from the coordinating tetrazole moiety to have an electronic impact on the spin transition. The subtle variation of the steric demand of the ligand in a highly comparable series was found to have a comparatively large impact on the spin-transition behavior, which highlights the sensitivity of the effect to subtle structural changes.

„Halogenated Alkyltetrazoles for the Rational Design of FeII Spin-Crossover Materials: Fine-Tuning of the Ligand Size“, D. Müller, C. Knoll, M. Seifried, J. Welch, G. Giester, M. Reissner, P. Weinberger, Chem. Eur. J. 2018, 24, 5271–5280
https://doi.org/10.1002/chem.201704656