Issue 46, 2018

Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands

Abstract

Trinuclear cobalt paddlewheel complexes, [Co3(dpa)4X2] (dpa = the anion of 2,2′-dipyridylamine, X = Cl, Br, –NCS, –CN, (NC)2N), are known to demonstrate a thermally-induced spin-crossover (SCO). Despite a wealth of structural and magnetic information about such complexes, the role of the axial ligand on the characteristic SCO temperature (T1/2) remains ambiguous. The situation is complicated by the observation that the solid state geometry of the complexes, symmetric or unsymmetric, with respect to the central cobalt ion, also appears to influence the SCO behavior. In order to seek trends in the relationship between the nature of the axial ligand, geometry and magnetic properties, we have prepared the first examples of tricobalt paddlewheel complexes with axial fluorido and iodido ligands, as well as two new chlorido and bromido solvates. Their SCO properties are discussed in the context of an examination of previously reported chlorido and bromido adducts. The main conclusions are: (1) T1/2 values follow the trend I < Br ≈ Cl < F; (2) while the molecular geometry is predominantly guided by crystal packing for the Cl, Br and I derivatives, the presence of an axial fluoride may favor a more symmetric core; (3) the magnetic characterization of a second example of an unsymmetric complex supports the observation that they display dramatically lower T1/2 values than their symmetric analogues; and (4) SCO in crystallographically symmetric compounds apparently occurs without loss of molecular or crystallographic symmetry, while a gradual geometric transformation linking the temperature dependence of quasi-symmetric to unsymmetric in crystallographically unconstrained compounds was found.

Graphical abstract: Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands

Supplementary files

Article information

Article type
Paper
Submitted
21 Sep 2018
Accepted
06 Nov 2018
First published
15 Nov 2018
This article is Open Access
Creative Commons BY-NC license

Dalton Trans., 2018,47, 16798-16806

Temperature dependence of the spin state and geometry in tricobalt paddlewheel complexes with halide axial ligands

A. Srinivasan, X. Wang, R. Clérac, M. Rouzières, L. R. Falvello, J. E. McGrady and E. A. Hillard, Dalton Trans., 2018, 47, 16798 DOI: 10.1039/C8DT03833C

This article is licensed under a Creative Commons Attribution-NonCommercial 3.0 Unported Licence. You can use material from this article in other publications, without requesting further permission from the RSC, provided that the correct acknowledgement is given and it is not used for commercial purposes.

To request permission to reproduce material from this article in a commercial publication, please go to the Copyright Clearance Center request page.

If you are an author contributing to an RSC publication, you do not need to request permission provided correct acknowledgement is given.

If you are the author of this article, you do not need to request permission to reproduce figures and diagrams provided correct acknowledgement is given. If you want to reproduce the whole article in a third-party commercial publication (excluding your thesis/dissertation for which permission is not required) please go to the Copyright Clearance Center request page.

Read more about how to correctly acknowledge RSC content.

Social activity

Spotlight

Advertisements