Magnetic exchange interactions in perfluorophenyl dithiadiazolyl radicals

✍ Scribed by Jeremy M. Rawson; Javier Luzon; Fernando Palacio

• Publisher: Elsevier Science
• Year: 2005
• Tongue: English
• Weight: 562 KB
• Volume: 249
• Category: Article
• ISSN: 0010-8545
• DOI: 10.1016/j.ccr.2005.04.020

✦ Synopsis

EPR, electrochemical studies and neutron diffraction studies on a large range of 1,2,3,5-dithiadiazolyl radicals have shown that the spin density distribution is essentially unaffected by substituent effects. The variation of magnetic properties previously reported for a series of perfluorophenyl-dithiadiazolyl radicals p-XC 6 F 4 CNSSN (X = CN, Br, NO 2 and NCC 6 F 4 ) is therefore due to differences in molecular packing. The nearest-neighbour magnetic exchange interactions in these radicals are probed through DFT studies (B3LYP/6-311G**) and are shown to exhibit a variety of both ferromagnetic and antiferromagnetic interactions. All exchange interactions with |J| > 1 cm -1 coincide with close heterocyclic contacts between dithiadiazolyl rings (3.18-4.00 Å) and produce |J| values up to 40 K. An analysis of these interactions indicates that the dominant exchange pathway would appear to be a direct exchange mechanism between radical centres, with orthogonality of the singly-occupied molecular orbitals (SOMOs) favouring ferromagnetic interactions.