Spin-crossover in cobalt(II) imine complexes

Abstract

Whereas there are hundreds of known iron(II) spin-crossover compounds, only a handful of cobalt(II) spin-crossover compounds have been discovered to date, and hardly an in depth study on any of them exists. This review begins with an introduction into the theoretical aspects to be considered when discussing spin-crossover compounds in general and cobalt(II) systems in particular. It is followed by case studies on [Co(bpy)3]2+ and [Co(terpy)2]2+ (bpy = 2,2'-bipyridine, terpy = 2,2':6',2″-terpyridine) presenting and discussing results from magnetic susceptibility measurements, X-ray crystallography, optical spectroscopy, and EPR spectroscopy

Influence of Guest−Host Interactions on the Structural, Energetic, and Mössbauer Spectroscopy Properties of Iron(II)tris(2,2′-bipyridine) in the Low-Spin and High-Spin States: A Density-Functional Theory Study of the Zeolite-Y Embedded Complex

“…However, although they perform quite well for the study of numerous properties of transition metal complexes, 59 they tend to dramatically fail when it comes to the accurate evaluation of the relative energies of the different spin-states of these systems. 6,7,[60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76] [L], respectively, where r Γ designates the average iron-nitrogen bond length in the Γ manifold (Γ ) LS, HS).…”

Spin-crossover, mesomorphic and thermoelectrical properties of cobalt(ii) complexes with alkylated N3-Schiff bases

“…2,3,[7][8][9] Among these, the most extensively studied SCO materials are complexes of iron(II) (d 6 ), 4,10,11 and cobalt(II) (d 7 ), 12,13 which have attracted the interest of many researchers as potential functional materials in fields such as molecular electronics, memory storage, thermochromic indicators and sensors. 14,15 However such applications require that the spin transition occurs abruptly at ambient temperature (ideally room temperature) and with wide thermal hysteresis (for memory effect).…”

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2 O (3), where L [12][13][14][15][16] are N 3 -Schiff bases appended with linear C 12-16 carbon chains at the nitrogen atoms, were obtained in good yields by facile one-pot reactions. The single crystal X-ray structure of complex 1 shows a tetragonally compressed CoN 6 coordination geometry.

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Spin-crossover and the LIESST effect in [Fe Co1‒(bpp)2][BF4]2 (1.00 ≤x≤ 0.77). Comparison with bifunctional solid solutions of iron and cobalt spin-crossover centers

“…The resultant change in lattice pressure on the [Co(terpy) 2 ] 2+ dopant induces it to change its own spin state in sympathy [33]. Notably, this allosteric behavior is observed during spin-state switching under both thermodynamic (thermal) and kinetic (LIESST effect [34]) conditions [26].…”