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RESEARCH PRODUCT

Spin-State-Dependent Redox-Catalytic Activity of a Switchable Iron(II) Complex

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description

The spin state of catalytically active 3d metal centers plays a significant role for their activity in enzymatic processes and organometallic catalysis. Here we report on the catalytic activity of a Fe(II) coordination compound that can undergo a cooperative switch between low-spin (LS) and high-spin (HS) states. Catalytic measurements within 291 - 318 K temperature region reveal a drastic drop of the catalytic activity upon conversion of metallic centers from the LS to the HS form. For a thermoswitchable [Fe(NH2trz)3]Br2 complex (Tup = 305 K), an activation energy is found to be considerably lower for the LS state (158 kJ mol-1) comparing to the HS state (305 kJ mol-1). Mossbauer analysis reveals that this is related to a higher conversion of a LS complex upon oxidation. The comparisons with another polymorph of [Fe(NH2trz)3]Br2 (Tup = 301 K) and with [Fe(NH2trz)3](ClO4)2 (Tup = 240 K) are made. These results show the perspective of spin-crossover compounds to compare a catalytic activity of different spin states within the same material when other differentiations are minimized.