Spin-crossover (SC) can be observed in transition-metal complexes with d4�d7 electron configuration. Spin-crossover is a representative example of molecular bistability, in which the high spin (HS) and low spin (LS) states are inter-convertible by physical perturbations such as temperature, pressure, or light. The conditions under which SC occurs can be modulated by the organic ligand(s) coordinated to the metal center. Strong-field ligands tend to reinforces LS complexes while weak-field ligands afford HS complexes. Modulation of ligand strength allows fine-tuning of the SC phenomenon. In this work we plan to investigate the magnetic properties associated with iron(III) bis-triazamacrocyclic complexes. Temperature-dependent magnetic data on systems supported by all aliphatic triazamacrocycles is scarce. The ease with which the triazamacrocyclic ligands can be symmetrically and asymmetrically functionalized allows for systematic structure-magnetic studies. Ligand systems to be presented include 1,4,7-triazacyclononane (tacn), 1,4,7-triazacyclodecane (tacd), and 1,4,8-triazacycloundecane (tacud). We currently observe thermochromic behavior in [Fe(tacn)2](OTf)3  and [Fe(tacd)2](OTf)3 while no thermochromic change is seen for [Fe(tacn)2](OTf)3.                                                 

Structural, spectroscopic, and magnetic properties of iron triazamacrocyclic complexes

246th National Meeting (2013)

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