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New Iron(II) Spin-crossover Complexes with Heterocyclic Amine-derived Ligands and STEPS Experiments on Photogenerated Metastable High-spin States

DOI: 10.1039/DT9870002621

Source and publish data:

Journal of the Chemical Society, Dalton Transactions p. 2621 - 2630 (1987)

Update date:2022-08-11

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Authors:

Addison, Anthony W.Addison, Anthony W.

Burman, SudhirBurman, Sudhir

Wahlgren, Curtis G.Wahlgren, Curtis G.

Rajan, Odatt A.Rajan, Odatt A.

Rowe, Teresa M.Rowe, Teresa M.

Sinn, EkkehardSinn, Ekkehard

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Article abstract of DOI:10.1039/DT9870002621

Cationic complexes of the type NN)3>2+ and NNN)2>2+ have been isolated as Cl-, ClO4-, or BF4- salts, where LNN and LNNN represent bidentate and tridentate nitrogen-donor ligands respectively.The bidentate ligands were 2-(2'pyridyl)benzimidazole (pybzim), 2-(2'-pyridyl)-N-methylbenzimidazole (mpybzim); 2-(2'-pyridyl)benzothiazole (pybzt), 2,2'-dipyridylamine (dpya), and the tridentates di(2-pyridylmethyl)amine (dpyma), 2,6-bis(benzimidazol-2'-yl)pyridine (bzimpy), 2,6-bis(N-methylbenzimidazol-2'-yl)pyridine (mbzimpy), and 2,6-bis(benzothiazol-2'-yl)pyridine (bztpy).Except for , all these FeN6 chromophores exhibit strong absorption in the 550 nm region, which is assigned as a metal-to-ligand charge-transfer transition.Between 4 and 320 K, the iron(II) is in the low-spin form in the majority of these compounds; high-spin exceptions are 2 and Cl2.Other complexes show evidence of the onset of a spin transition near 40 deg C, while the salt *CHCl3 is a well defined spin-crossover system.The low-spin complex 2 was excited by irradiation with visible light, and the generation and decay of resulting high-spin form was observed under cryogenic conditions.In solution, 2+ acts as a weak diprotic acid and also exhibits quintet ->/<- singlet spin crossover (ΔHo = -42.7 kJmol-1, ΔSo = -140.9 JK-1mol-1).The complexes are all electrochemically oxidizable to their iron(III) forms in non-aqueous solution, but the dpyma, bztpy, pybtz, and dpya chelates thus formed are unstable.The iron(III) complex -2bzimpy)2>- containing the doubly deprotonated ligand was obtained as its low-spin triethylammonium salt.The high-spin chloro complexes . , Fe(mbzimpy)Cl2, and the mixed-spin iron(II) complex salt were also isolated.

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Product name:2, 6-Bis(N-methylbenzimidazol-2-yl)pyridine

Cas No:112362-30-8

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