Spin density studies onp-O2NC6F4CNSSN: A heavyp-block organic ferromagnet

Abstract

A complete picture of the spin density distribution in the organic radical p-O2NC6F4CNSSN has been obtained by a combination of polarized neutron diffraction, electron paramagnetic resonance (EPR), and electron-nuclear double resonance (ENDOR) spectroscopies, and ab initio density-functional theory (DFT) calculations. Polarized neutron diffraction revealed that the spin distribution is predominantly localized on the N and S atoms (+0.25μB and +0.28μB, respectively) of the heterocyclic ring with a small negative spin density on the heterocyclic C atom (−0.06μB). These spin populations are in excellent agreement with both ab initio DFT calculations (spin populations on the C, N, and S sites of −0.07, 0.22 and 0.31, respectively) and cw-EPR studies which estimated the spin population on the N site as 0.24. The DFT calculated spin density revealed less than 1% spin delocalization onto the perfluoroaryl ring, several orders of magnitude lower than the density on the heterocyclic ring. cw-ENDOR studies at both X-band (9 GHz) and Q-band (34 GHz) frequencies probed the spin populations on the two chemically distinct F atoms. These spin populations on the F atoms ortho and meta to the dithiadiazolyl ring are of magnitude 10−3 and 10−4, respectively.