Acta Crystallographica Section B

Structural Science

Volume 59, Part 4 (August 2003)

research papers

Acta Cryst. (2003). B59, 479-486 [ doi:10.1107/S0108768103011200 ]

Towards direct correlations between spin-crossover and structural features in iron(II) complexes

M. Marchivie, P. Guionneau, J.-F. Létard and D. Chasseau

Abstract: The [Fe(PM-BiA)₂(NCS)₂] complex, where PM is N-2-pyridylmethylene and BiA is 4-aminobiphenyl, crystallizes in two polymorphs. The two phases, denoted (I) and (II), undergo a spin-crossover when the sample is cooled and present distinct spin-transition features as (I) shows a very abrupt spin transition, while (II) exhibits a gradual transition. The two forms of the complex are used to investigate the correlations that exist between the spin-transition features and structural features. This article presents the crystal structures of polymorph (II) at room temperature (high spin) and at 120 K (low spin), including a comparison with those of polymorph (I). This study reveals that the packing, in a first approximation, is similar in both forms. In order to look at the crystal structures in more detail, a new angular parameter, denoted [bold theta] _NCS, as well as a particular type of intermolecular hydrogen-bond interaction, which involves the S atoms of the NCS ligands, are investigated. Interestingly, this angle and this intermolecular interaction can be directly connected to the cooperativity of the spin transition. Such a result is extended to all the SCO iron(II) complexes belonging to the same family of the general formula [Fe(PM-L)₂(NCS)₂].

Keywords: Spin-crossover; structural features; cooperativity; polymorphism.


	Structure factor file (CIF format) (299.5 kbytes) Contains datablock biamono

	Structure factor file (CIF format) (361.5 kbytes) Contains datablock bia120k

Notes:

To open or display or play some files, you may need to set your browser up to use the appropriate software. See the full list of file types for an explanation of the different file types and their related mime types and, where available links to sites from where the appropriate software may be obtained.

The download button will force most browsers to prompt for a file name to store the data on your hard disk.

Where possible, images are represented by thumbnails.