Issue 21, 2021

The effect of tether groups on the spin states of iron(ii)/bis[2,6-di(pyrazol-1-yl)pyridine] complexes

Abstract

The synthesis of six 2,6-di(pyrazol-1-yl)pyridine derivatives bearing dithiolane or carboxylic acid tether groups is described: [2,6-di(pyrazol-1-yl)pyrid-4-yl]methyl (R)-lipoate (L1), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxamido]ethyl (R)-lipoate (L2), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxy]ethyl (R)-lipoate (L3), N-([2,6-di(pyrazol-1-yl)pyrid-4-ylsulfanyl]-2-aminoethyl (R)-lipoamide (L4), 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxamido]acetic acid (L5) and 2-[(2,6-di(pyrazol-1-yl)pyridine)-4-carboxamido]propionic acid (L6). The iron(II) perchlorate complexes of all the new ligands exhibit gradual thermal spin-crossover (SCO) in the solid state above room temperature, except L4 whose complex remains predominantly high-spin. Crystalline [Fe(L6)2][ClO4]2·2MeCN contains three unique cation sites which alternate within hydrogen-bonded chains, and undergo gradual SCO at different temperatures upon warming. The SCO midpoint temperature (T1/2) of the complexes in CD3CN solution ranges between 208–274 K, depending on the functional group linking the tether groups to the pyridyl ring. This could be useful for predicting how these complexes might behave when deposited on gold or silica surfaces.

Graphical abstract: The effect of tether groups on the spin states of iron(ii)/bis[2,6-di(pyrazol-1-yl)pyridine] complexes

Supplementary files

Article information

Article type
Paper
Submitted
31 Mar 2021
Accepted
04 May 2021
First published
04 May 2021

Dalton Trans., 2021,50, 7417-7426

The effect of tether groups on the spin states of iron(II)/bis[2,6-di(pyrazol-1-yl)pyridine] complexes

I. Capel Berdiell, V. García-López, M. J. Howard, M. Clemente-León and M. A. Halcrow, Dalton Trans., 2021, 50, 7417 DOI: 10.1039/D1DT01076J

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