Weakening of the pi*-pi* dimerisation in 1,2,3,5-dithiadiazolyl radicals: structural, EPR, magnetic and computational studies of dichlorophenyl dithiadiazolyls, Cl2C6H3CNSSN

Constantinides, Christos P., Eisler, Dana J., Alberola, A., Carter, Emma ORCID: https://orcid.org/0000-0001-6691-2377, Murphy, Damien Martin ORCID: https://orcid.org/0000-0002-5941-4879 and Rawson, Jeremy M. 2014. Weakening of the pi*-pi* dimerisation in 1,2,3,5-dithiadiazolyl radicals: structural, EPR, magnetic and computational studies of dichlorophenyl dithiadiazolyls, Cl2C6H3CNSSN. Crystengcomm 16 (31) , pp. 7298-7312. 10.1039/C4CE00308J

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Abstract

A series of dichlorophenyl dithiadiazolyls (DCP-DTDA) have been prepared and structurally characterized by X-ray diffraction (1 = 2,3-DCP-DTDA; 2 = 2,4-DCP-DTDA; 3 = 2,5-DCP-DTDA, 4 = 3,4-DCP-DTDA and 5 = 3,5-DCP-DTDA). All the radicals adopt cis-cofacial π*–π* dimers with intra-dimer SS contacts in the range 3.119(8)–3.300(5) Å. The propensity for chloro-aromatics to adopt a β-sheet structure assists formation of lamellar structures in 1–5 with intra-stack ClCl contacts in the range 3.44(1)–3.82(1) Å. Perpendicular to the stacking direction, the packing is dominated by formation of intermolecular SCl contacts. Variable-temperature magnetic susceptibility measurements on 1–5 in the range 5–300 K reveal the onset of paramagnetism around ca. 200 K. Solid-state EPR studies reveal that this paramagnetism is associated with thermal population of a triplet excited state. A good fit to the Bleaney–Bowers model determined the exchange interactions (2J) between the radicals in the dimers to be in the range −904 to −1529 cm−1. Computational studies of the dimerisation process indicate that at intra-dimer SS distances in excess of 3.2 Å the closed-shell singlet becomes destabilized with respect to both the open-shell singlet and triplet state configurations.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Chemistry
Subjects:	Q Science > QD Chemistry
Additional Information:	First published online 11 April 2014
Publisher:	Royal Society of Chemistry
ISSN:	1466-8033
Date of Acceptance:	31 March 2014
Last Modified:	15 Nov 2022 12:20
URI:	https://orca.cardiff.ac.uk/id/eprint/73968

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