Temperature Dependence Of ESR Signal Research Articles

High-Spin Nitrenes with s-Triazine Skeleton

Heteroatomic high-spin molecules are suitable for a model study of room-temperature stable molecular based magnetics. We studied high-spin nitrenes (S = 1 and 2) with s-triazine skeleton, which were generated by the photolysis of the polyazide precursor. We identified mononitrene 1 (S = 1) and bisnitrene 2 (S = 2) for the first time by single-crystal ESR measurements. The fine-structure parameters were determined by the angular dependence of resonance fields. The determined fine-structure parameters were |D| = 1.402 cm−1 and |D| = 0.280 cm−1 for mononitrene 1 and bisnitrene 2, respectively. The large D values indicate that π-spin delocalization effects were hampered by introducing heteroatoms to π-spin systems. The hyperfine splittings due to the monovalent nitrogen nucleus of 1 were observed with magnetic field along the principal axis of the fine structure tensor. The hyperfine splitting constant was about 0.0018 cm−1. The temperature dependence of ESR signals showed that 1 and 2 were triplet and quintet in the ground state, respectively.

ESR and ENDOR Studies of Functional LB Films

Abstract Role of ESR and ENDOR spectroscopies in the characterization of functional LB films is discussed. Two illustrative examples are shown. In the first case, the detailed study of in-plane molecular orientation is discussed from the analysis of the ESR and ENDOR spectra of the stable radicals detected in LB films of a merocyanine dye. By identifying a nitrogen hyperfine structure, computer simulation of the ESR spectra yields a characteristic orientation of radicals with respect to the dipping direction of the substrate. The results strongly suggest a flow orientation of J-aggregates from which radicals may originate. The observed orientation is well described by the recent theory of flow orientation. In the second case, study of the temperature dependence of ESR signal, in particular the spin susceptibility, is shown to provide the microscopic evidence for the development of columnar structures in conducting LB films composed of amphiphilic charge-transfer complexes.

Effective Electron Correlation Energy in Amorphous Ge–S

Anomalous temperature dependence of ESR signal has been observed in amorphous Ge–S near the composition of Ge 42 S 58 . The result is interpreted by assuming the presence of Ge dangling bonds with negative ( U 0). The density of the defects with U 0 are ∼10 17 and ∼10 15 cm -3 respectively. In Ge 30 S 70 glass, both S dangling bonds with U 0 are likely to exist although the normal temperature dependence of ESR signal is observed. Difference between bulk and film samples, and the effect of Ag doping are also studied. The magnitude of the negative U in various samples is correlated with the slope of the Urbach tail in the optical absorption edge.