Electronic Structure Modulation in an Exceptionally Stable Non-Heme Nitrosyl Iron(II) Spin-Crossover Complex

Abstract

The highly stable nitrosyl iron(II) mononuclear complex [Fe(bztpen)(NO)](PF6 )2 (bztpen=N-benzyl-N,N',N'-tris(2-pyridylmethyl)ethylenediamine) displays an S=1/2↔S=3/2 spin crossover (SCO) behavior (T1/2 =370 K, ΔH=12.48 kJ mol(-1) , ΔS=33 J K(-1) mol(-1) ) stemming from strong magnetic coupling between the NO radical (S=1/2) and thermally interconverted (S=0↔S=2) ferrous spin states. The crystal structure of this robust complex has been investigated in the temperature range 120-420 K affording a detailed picture of how the electronic distribution of the t2g -eg orbitals modulates the structure of the {FeNO}(7) bond, providing valuable magneto-structural and spectroscopic correlations and DFT analysis.

Keywords: antiferromagnetic coupling; iron; molecular structures; nitrosyl complexes; spin crossover.