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Effects of Halo-substitution on 2'-Chloro-5'-halo-phenyl-1,2,3,5-dithiadiazolyl Radicals: A Crystallographic, Magnetic and EPR Case Study

Constantinides, Christos P., Carter, Emma, Eisler, Dana, Beldjoudi, Yassine, Murphy, Damien Martin and Rawson, Jeremy M. 2017. Effects of Halo-substitution on 2'-Chloro-5'-halo-phenyl-1,2,3,5-dithiadiazolyl Radicals: A Crystallographic, Magnetic and EPR Case Study. Crystal Growth and Design 17 (6) , pp. 3017-3029. 10.1021/acs.cgd.6b01700

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Abstract

The syntheses and characterization of the aryl-substituted dithiadiazolyls, 2ʹ-Cl-5ʹ- X-C6H3CNSSN• [1 (X = F), 2 (X = Cl), 3 (X = Br), 4 (X = I)] are described. In all four cases the radicals adopt distorted stacks of π*-π* dimers with inter-stack S···X contacts. In 1 (monoclinic P2/c) S···Cl contacts are manifested through a non-crystallographic 3-fold axis forming supramolecular trimers whereas the inter-stack S…X contacts in 2 (triclinic P-1), 3 and 4 (which form an isostructural pair, orthorhombic Pna21) form supramolecular chains. While all the structures adopt π*-π* cis-oid dimer motifs, tuning the halogen modifies the intra-dimer S···S distance. Variable temperature SQUID magnetometry and X-band CW-EPR studies revealed the presence of a thermally accessible triplet state in all cases, with the singlet-triplet separation appearing in the order 1 > 2 > 3 > 4, consistent with a reduction in the overlap integral with increasing intra-dimer S···S separation. Variable temperature structural studies on both 2 and 4 reveal a structural evolution from a distorted π-stack motif towards a regular π-stacked array on warming. This is particularly pronounced in 2 where the intermolecular S…S separations along the stacking direction converge on a regular 3.6 Å spacing at ambient temperature.

Item Type: Article
Date Type: Published Online
Status: Published
Schools: Chemistry
Additional Information: PDF uploaded in accordance with publisher's polices at http://www.sherpa.ac.uk/romeo/issn/1528-7483/ (accessed 24.3.17).
Publisher: American Chemical Society
ISSN: 1528-7483
Date of First Compliant Deposit: 21 March 2017
Date of Acceptance: 14 March 2017
Last Modified: 29 Jun 2019 02:05
URI: http://orca.cf.ac.uk/id/eprint/99239

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