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Crystallographic elucidation of purely structural, thermal and light-induced spin transitions in an iron(ii) binuclear complex

Kaiba, A., Shepherd, H.J., Fedaoui, D., Rosa, P., Goeta, A.E., Rebbani, N., Létard, J.F., Guionneau, P. (2010) Crystallographic elucidation of purely structural, thermal and light-induced spin transitions in an iron(ii) binuclear complex. Dalton Transactions, 39 (11). pp. 2910-2918. ISSN 14779226 (ISSN). E-ISSN 1477-9234. (doi:10.1039/b914841h) (The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided) (KAR id:50840)

The full text of this publication is not currently available from this repository. You may be able to access a copy if URLs are provided. (Contact us about this Publication)
Official URL
https://doi.org/10.1039/b914841h

Abstract

The intricate phase diagram of the binuclear iron(ii) spin-crossover complex [{Fe(3-bpp)(NCS)2}2(4,4�-bypiridine)] ·2CH3OH where 3-bpp is 2,6-bis(pyrazol-3-yl)pyridine has been investigated by variable temperature single crystal X-ray diffraction including a study into the effect of photo-irradiation. This sample is known to exhibit an incomplete spin transition at low temperature. At room temperature, in phase I, iron ions are all crystallographically equivalent, adopting the high spin state (HS). X-Ray structural investigation has revealed two phase transitions in the range (300-30 K). The first transition (T�161 K) leading to phase II is of a purely structural nature and corresponds to a break in symmetry as a result of a twist of the two rings of 4,4�-bipyridine; the two iron sites of the binuclear unit becoming crystallographically independent but remaining all HS. The second structural transition corresponds to the spin crossover, one of the two Fe(ii) ions of the binuclear complex being in the low spin state (LS) in phase III. The crystal structure shows an ordered HS-LS crystal packing where HS and LS sites are clearly identified and not randomly distributed in the metal ion sites as often observed. Moreover, light irradiation of single crystals in phase III at 30 K, leading to phase III*, induces a light-induced spin-state trapping (LIESST) effect corresponding to the full conversion of all the iron sites to HS. The crystal packing in phase III* is closer to that of phase III than to those observed in the other HS phases, I and II. This reveals an unusual differentiation between the thermal and light-induced HS states. A deeper analysis of the structural properties first demonstrates the key role of the bipyridine bridge in the peculiar preliminary pure structural transition shown by the title compound. Elsewhere, it also shows that the molecular packing is strongly dependent on the nature of the external perturbation contrary to the iron coordination sphere geometry that appears to be only dependent on the spin state. Moreover, in the HS phase II, the distortion of the iron sites that will subsequently undergo a spin crossover demonstrates some differences with the distortion of the iron sites that remain HS. The predominant role of the iron environment distortion in the spin crossover phenomenon is thus clearly evidenced. © 2010 The Royal Society of Chemistry.

Item Type: Article
DOI/Identification number: 10.1039/b914841h
Additional information: Unmapped bibliographic data: LA - English [Field not mapped to EPrints] J2 - Dalton Trans. [Field not mapped to EPrints] AD - CNRS, Université de Bordeaux, ICMCB, 87 avenue du Dr A. Schweitzer, Pessac F-33608, France [Field not mapped to EPrints] AD - Université Annaba, BP 12, 23200 Sidi-Ammar, Algeria [Field not mapped to EPrints] AD - Chemistry Department, Durham University, South Road, Durham DH1 3LE, United Kingdom [Field not mapped to EPrints] DB - Scopus [Field not mapped to EPrints]
Uncontrolled keywords: Binuclear complexes, Bipyridine bridge, Bipyridines, Coordination sphere, Crystal packings, External perturbations, High spin state, In-phase, Iron ions, Light irradiations, Low temperatures, Molecular packings, Phase II, Photo-irradiation, Randomly distributed, Room temperature, Single crystal x-ray diffraction, Spin crossovers, Spin state, Spin transition, Spin-crossover complexes, Spin-crossover phenomena, Structural investigation, Structural transitions, Title compounds, Two phase, Variable temperature, Coordination reactions, Crystal structure, Hydraulic structures, Iron compounds, Irradiation, Light, Metal ions, Phase diagrams, Single crystals, Spin dynamics, X ray diffraction, X ray diffraction analysis, Phase transitions
Subjects: Q Science > QD Chemistry > QD473 Physical properties in relation to structure
Divisions: Faculties > Sciences > School of Physical Sciences > Functional Materials Group
Depositing User: Giles Tarver
Date Deposited: 22 Oct 2015 08:48 UTC
Last Modified: 23 Jan 2020 04:10 UTC
Resource URI: https://kar.kent.ac.uk/id/eprint/50840 (The current URI for this page, for reference purposes)
Shepherd, H.J.: https://orcid.org/0000-0003-0832-4475
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