Triplet structure

A related finding appears for the dianions of the doubly layered system [14] their esr spectra taken in the glass provide evidence for a triplet structure, and from the D-value the inter-plane distance in the charged species can be readily determined (Irmen et al., 1984 Alexander et al, 1989). 

The EPR spectra of Cu(II)-doped /-alanine single crystals show a well resolved triplet structure which is due to a nitrogen ligand nucleus182. Moreover, in the partially... 

Besides a poorly resolved triplet structure in the EPR spectrum of 57Fe enriched two-iron ferredoxins266 at gz, no hf interactions are observed in all these iron-sulfur clusters. The distribution of principal axes of the g tensors gives rise to an inhomogeneous, field-dependent EPR linewidth, and obscures the resolution of ligand hfs265. This distribution, whose origin is not completely established, does not, however, prevent application of the ENDOR technique. 

We know that carbenes have either a singlet or triplet structure. The addition of singlet carbene gives a halogenium ion and is therefore stereospecific. 

Fig. 35. Part of the spectrum recorded at 3.0 T from TA (shown in Fig. 33b) demonstrating the line splitting caused by dipolar coupling. Triplet structure of Cr3 is resolved, Tau/TMA lead to 4 signal components. The frequency difference between the two Ct2 signals centred at 3.95 ppm is smaller compared to 1.5 T, but these signals are of higher amplitude than in Cr3.

In a study of 2,2 - and l,2 -biindenyl dilithium (6, 7, Scheme 1), C solid state NMR investigations were used, in combination with solution NMR studies and calculations, to obtain information about the existence of so-called triplet structures . Triplet structures are alkali metal complexes of dianions that arrange in a structure akin to dimers in Figure lb and were found by X-ray crystallography for the TMEDA complex of the dilithium salt of 9,9 -bifluorene (Figure 13) . This kind of structure has been proposed to account for the unexpected small difference in the first and second pXj value in some systems, where ApXa is found to be less than 1 pXa unit. ... 

The chemical shifts obtained in solution under different experimental conditions were compared to the shifts of the TMEDA complexes in the solid state. For 6, all data indicate a triplet structure of the CIP. The most compelling evidence for the triplet structure is the polarization of charge towards the two bridging carbons under CIP conditions. However, for 7, the charge distribution differs under CIP conditions in solution and in the solid state, as reflected by the chemical shifts. In solution, the shift data indicate again a triplet structure. In the solid state, however, the cations are not located at the bridging carbons, but shifted towards the five-membered ring systems. 

FIGURE 13. X-ray structure of the TMEDA complex of the dUithium salt of 9,9 -bifluorene, where a triplet structure is evident... 

Branching on the carbon atoms adjacent to the oxygen usually leads to splitting of the C—O—C band. Isopropyl ether shows a triplet structure in the 1170-1114-cm1 region, the principal band occurring at 1114 cm-1. 

Fig. 18.6. Exchange and magnetic energies of (a) the He 9d states, (b) the He 9f states, and (c) the He 9g states. In (a) the 9d states, the singlet triplet splitting is not shown to scale. The 9d states are good singlet and triplet states. The 9f states are approximately singlets and triplets, but the 3F3 state is below the 3F4 state. The 9g states do not display singlet-triplet structure. All intervals are given in MHz.

Fig. 7. Correlation analysis of the repetition of purine in tRNA. A tRNA sequence is divided into triplets, beginning at the S end and in phase with the anticodon. The frequency with which a purine (R) in the first position of the triplet occurs n positions later is counted and plotted against n. The period of three which emerges indicates clearly a triplet structure of the form RNY. The curves show values for the averaged sequences of E. coli and of all tRNAs investigated to date these are compared with that of the master sequence arising from the superposition of all tRNAs. The fact that the correlation is clearer in the master sequence suggests that this may represent a "memory of the earliest phase of evolution.

Recent experimental studies supports the existence of tetrahedral N4 in the nitrogen plasma as well as in liquid and solid nitrogen [9,10], whereas neutralization-reionization mass spectrometry study of N4 suggests that observed species is the open-chain triplet structure [11]. 

The 32-electron iron compound 11 is paramagnetic (19). This is ascribed to the ground state having a triplet structure with the HOMO rr (e", overlap of metal dxz and dyz orbitals) relative to FeFe bonding (79), and only half occupied by two electrons. 

The a, /3-, and N-H protons of indole (1) in carbon tetrachloride appear as triplets23 (Fig. 4A, p. 286), readily separable from each other and from the aromatic protons. The triplet structure shows that, like pyrrole,24-26... 

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