Electron spin resonance line shapes of randomly oriented molecules in septet and nonet states by a perturbation approach

Abstract

The electron spin resonance line shapes of randomly oriented molecules in septet and nonet states are analyzed in terms of the formulas derived from a perturbation treatment to third-order in the fine-structure energy. The method is applied to a ground-state septet hydrocarbon, 3, 3'diphenylmethylenebis (phenylmethylene), and a ground-state nonet hydrocarbon, mphenylenebis[(diphenylmethylen-3-yl)methylene], randomly oriented in mixed polycrystalline powders of benzophenone. It is shown that the g factor and the fine-structure parameters are determined from the line shapes of a K-band spectrum with nearly the same accuracy as in a single-crystal experiment. Extra lines have been observed in addition to the canonical lines corresponding to the external magnetic field along the principal axes of the fine-structure tensor. The appearance of extra lines in the spectra of septet and nonet molecules is discussed relative to the third-order perturbation theory.

Density functional study of intramolecular ferromagnetic interaction through m-phenylene coupling unit (I): UBLYP, UB3LYP, and UHF calculations

“…11 and 12 are investigated here, are well established on experimental grounds. [17][18][19][20][21][22][23][24][25][26][27][28] Similarly, Schlenk hydrocarbon biradicals with m-phenylene bridged biradicals have the triplet ground states, 64 supporting the computational results for 2. On the other hand, DFT results indicate that the stabilities of highspin states are lower for charged molecules 4 and 5 than for neutral molecules 1-3.…”

“…From experimental [17][18][19][20][21][22][23][24][25][26][27][28] and theoretical 11,13,14,[29][30][31] studies of magnetic interactions, well-known organic magnetic molecules with the ferro͑antiferro͒magnetic ground state are m-͑p-or o-͒ phenylene-bridged organic polyradicals. The meta-isomers have usually more stable high-spin states with a parallel spin configuration than low-spin states with an antiparallel spin configuration between radical sites.…”

General Simulation of Transient ESR and Continuous‐Wave ESR Spectra for High‐Spin States Using a Density Matrix Formalism

“…Figure 1 shows the simulated spectrum of the quartet photoexcited state of the p-radical 1 [8b] (the inset of Figure 1) as well as the one observed at 800 ns after laser excitation. X, Y, and Z are assigned to the X, Y, and Z principal-axis canonical transitions and A is an off-axis extra line [17,26] (n = 9.0935 GHz, 2B 1 = 0.012 mT and T = 30 K). The spin Hamiltonian parameters used in this simulation are g = 2.0043, D = 0.0225 cm À1 and E = 0.0 cm À1 .…”

Approaches to Organic Ferro- And Ferrimagnets

“…with g = 2.002, D = +0.03161 and E = -0.00394 em-', and S = 4, confirming the tetracarbene to be in the nonet state. Temperature dependence of the total signal intensity in the range 1.8-56 K showed that the observed nonet state is the ground state, while the other states are located at least 300 cm-I above the ground state [9]. The effective exchange energy between the carbenic centers are estimated by a theoretical study based on the periodic Kondo-Hubbard model to be ca.…”