Spin Crossover in New Iron(II) Coordination Compounds with Tris(pyrazol-1-yl)Methane

Abstract

We review here new advances in the synthesis and investigation of iron(II) coordination compounds with tris(pyrazol-1-yl)methane and its derivatives as ligands. The complexes demonstrate thermally induced spin crossover accompanied by thermochromism. Factors that influence the nature and temperature of the spin crossover are discussed.

A DFT and Mössbauer spectroscopy investigation of spin‐crossover iron(II) complexes with 2,6‐bis(1H‐imidazol‐2‐yl)pyridines

“…The search for new coordination compounds with the central atom switching its spin state under external impacts is an important task. This issue has been commonly discussed in new publications [1–7]. Spin crossover (SCO) is exhibited by metal compounds with d 4 ‐d 7 electron configurations, most often by Fe(II) and Fe(III) complexes.…”

“…Ligands coordinated in the tridentate‐cyclic mode are a promising class of organic compounds for the synthesis of SCO complexes. The coordination of two such ligands most often causes the SCO effect [6, 7, 19–21]. One representative of this class of compounds is 2,6‐bis(1 H ‐imidazole‐2‐yl)pyridines [21].…”

Iron(ii) complexes of 2,6-bis(imidazo[1,2-a]pyridin-2-yl)pyridine and related ligands with annelated distal heterocyclic donors

“…43 Iron(II) complexes of tridentate tris-heterocyclic ligands are particularly fruitful for SCO chemistry. 44,45 Iron(II) complexes of ligands derived from trispyrazolylborate, 46 trispyrazolylmethane, 46,47 2,6-di(1H-benzimidazol-2-yl)pyridine (bimpy) 48 and regioisomers of 2,6-di( pyrazolyl)pyridine (bpp) [49][50][51][52] can all exhibit SCO at accessible temperatures. These ligand classes can be functionalised using appropriate synthetic starting materials or through functional group manipulations, giving steric and electronic control over the spin states of their iron complexes.…”

Spin Crossover and Thermochromism in Iron(II) Complexes with 2,6-Bis(1H-imidazol-2-yl)-4-methoxypyridine

“…Spin crossover in iron(II) complexes, in terms 1 A 1 (S = 0, low-spin, LS) 5 T 2 (S = 2, high-spin, HS), is always unique for each iron(II) complex. The transition can be abrupt or gradual, complete or incomplete, may have hysteresis or not on the eff (T) dependence curve, have one or two stages.…”