Multiplet spectra

The non-relativistic version of DVME method was developed in 1998 and was applied to the analysis of multiplet spectra of ruby [6-8]. This method was later applied to the analysis of a variety of TM-doped solid-state-laser materials [9-11]. The relativistic version of DVME method was developed in 2000. However, at that time, it was still difficult to calculate multiplet spectra of RE ions due to the limited performance of available computers. On the other hand, the relativistic... 

Thanks to the rapid development of high-performance computers, the relativistic DVME method can now be applied to the analysis of multiplet spectra of RE ions. We have recently performed a systematic calculations of multiplet energy levels arising from 4f and 4f 15d configurations as well as the 4f —4f 15d transition spectra. 

The analysis of complicated NMR multiplet spectra (AB, A2B, where A and B have relatively close chemical shifts and AX, A2X, etc., where the A and B nuclei are well separated by chemical shift) is done by perturbation theory, involving nuclear spin eigenfunctions. 

Jorgensen elsewhere in this volume discusses how the Slater parameters appropriate to the multiplet splitting deviate from those associated with the optical multiplet spectra of the 4fn 1 ions in salts. 

Many free radicals generated in lignin have been studied Because of the structural complexity of lignin, multiplet spectra are obtained The analysis and interpretation of the spectrum can be performed by different techniques depending on the experimental conditions (Hon 1982, 1987, Zavoiskn 1945)... 

Figure 2 shows XPS data for dioxides of neptunium, plutonium, and americum compared to the appropriate fn multiplet calculations (8). These multiplet spectra do not represent the multiplet structure of either the fn or the fn l configurations. They are, instead, the final state multiplet structure of the fn l configuration modulated by the transition probability from the fn ground state to the fn l multiplets. 

Figure 2. XPS spectra of localized 5f states in three actinide oxides compared with calculated final-state multiplet spectra. The calculated multiplets are broadened to simulate experiment.

In fig. 10 we show a BIS spectrum for divalent, semiconducting SmS (Oh and Allen 1984). The BIS spectrum of divalent Sm should be analogous to that of trivalent Eu (4f initial-state configuration). The agreement with calculated f - f multiplet spectra is however poor, and more work is needed to establish experimentally whether all the features seen in the spectrum are 4f related. Oxidation yields Sm2 03 (trivalent Sm). The shape of the BIS spectrum of oxidized SmS is again only in fair agreement with that of trivalent Sm metal. 

A seven-line like signal was detected from carboxymethyl cellulose irradiated with ultraviolet light of 254 nm (Figure 7). When this sample was warmed to ambient temperature for 60 seconds, this multiplet spectrum was transformed rapidly into a prominent doublet signal with a hyperfine splitting constant of 20 gauss. This indicated that the primary free radicals... 

SO the results of the calculations given below refer to specific situations with definite restrictions on the structure of a ground multiplet spectrum or on the magnitude of an applied magnetic field. 

Figure Bl.11.3. 400 MHz H NMR spectrum of paracetamol (structure shown) with added integrals for each singlet or multiplet arising from the paracetamol molecule.

Homonuclear teclmiques such as J-resolved spectroscopy also exist for rotatmg all multiplets tlirough 90°, to resolve overlaps and also give a ID spectrum from which all homonuclear couplings have been removed [26]. 

Figure Bl.16.8. Example of CIDNP multiplet effect for a syimnetric radical pair with two hyperfme interactions on each radical. Part A is the radical pair. Part B shows the spin levels with relative Q values indicated on each level. Part C shows the spm levels with relative populations indicated by the thickness of each level and the schematic NMR spectrum of the recombination product.

While the stick plot examples already presented show net and multiplet effects as separate phenomena, the two can be observed in the same spectrum or even in the same NMR signal. The following examples from the literature will illustrate real life uses of CIDNP and demonstrate the variety of structural, mechanistic, and spin physics questions which CIDNP can answer. 

The tliree-line spectrum with a 15.6 G hyperfine reflects the interaction of the TEMPO radical with tire nitrogen nucleus (/ = 1) the benzophenone triplet caimot be observed because of its short relaxation times. The spectrum shows strong net emission with weak E/A multiplet polarization. Quantitative analysis of the spectrum was shown to match a theoretical model which described the size of the polarizations and their dependence on diffrision. 

Figure B2.4.3. Proton NMR spectrum of the aldehyde proton in N-labelled fonnainide. This proton has couplings of 1.76 Hz and 13.55 Hz to the two amino protons, and a couplmg of 15.0 Hz to the nucleus. The outer lines in die spectrum remain sharp, since they represent the sum of the couplings, which is unaffected by the exchange. The iimer lines of the multiplet broaden and coalesce, as in figure B2.4.1. The other peaks in the 303 K spectrum are due to the NH2 protons, whose chemical shifts are even more temperature dependent than that of the aldehyde proton.

A — P transition, shown in Figure 7.10(b), has six components. As with doublet states the multiplet splitting decreases rapidly with L so the resulting six lines in the spectrum appear, at medium resolution, as a triplet. For this reason the fine structure is often called a compound triplet. 

The purity of cyclobutanone was checked by gas chromatography on a 3.6-m. column containing 20% silicone SE 30 on chromosorb W at 65°. The infrared spectrum (neat) shows carbonyl absorption at 1779 cm. - the proton magnetic resonance spectrum (carbon tetrachloride) shows a multiplet at 8 2.00 and a triplet at S 3.05 in the ratio 1 2. 

The reference compound methyloxirane gives the H NMR spectrum 11a shown with expanded multiplets. What information regarding its relative configuration can be deduced from the expanded H multiplets of monordene displayed in 11b ... 

From which compound were the INADEQUATE contour plot and C NMR spectra 21 obtained Conditions (CD3)2CO, 95 % v/v, 25 °C, 100 MHz. (a) Symmetrised INADEQUATE contour plot with C NMR spectra (b) H broadband decoupled spectrum (c) NOE enhanced coupled spectrum (gated decoupling) (d) expansion of multiplets of (c). 

Conditions (CD3)2CO, 25 °C, 200 MHz H), 50 MHz ( C). (a) //NMR spectrum with expanded sections (b,c) C NMR partial spectra, each with proton broadband decoupled spectrum below and NOE enhanced coupled spectrum above with expanded multiplets at 6c = 76.6 and 83.0. 

Conditions CDCI3, 25 °C, 100 MHz ( C), 400 MHz H). (a-e) C NMR spectra (a,b) //broadband decoupled spectra (c,d) NOE enhanced coupled spectra (gated decoupling) with expansion (e) of the multiplets in the sp shift range (f) //NMR spectrum with expanded multiplets. 

The salts of some enamines crystallize as hydrates. In such cases it is possible that they are derived from either the tautomeric carbinolamine or the amino ketone forms. Amino ketone salts (93) ( = 5, 11) can serve as examples. The proton resonance spectra of 93 show that these salts exist in the open-chain forms in trifluoroacetic acid solution, rather than in the ring-closed forms (94, n = 5, 11). The spectrum of the 6-methylamino-l-phenylhexanone cation shows a multiplet at about 2.15 ppm for phenyl, a triplet for the N-methyl centered at 7.0 ppm and overlapped by signals for the methylene protons at about 8.2 ppm. The spectrum of 93 ( = 11) was similar. These assignments were confirmed by determination of the spectrum in deuterium oxide. Here the N-methyl group of 93 showed a sharp singlet at about 7.4 ppm since the splitting in —NDjMe was much reduced from that of the undeuterated compound. 

Reduction of epoxide 21 with lithium aluminium hydride gave a crystalline branched-chain methyl heptoside derivative 24. The NMR spectra of compounds 21 and 24 were very similar. In the spectrum of compound 24 the disappearance of the two sharp doublets at r 6.80 and 7.45 (2 protons) and the appearance of a singlet at r 8.65 (3 protons) is consistent with the reductive cleavage of epoxide 21 to give a substance 24 with a methyl substituent. The multiplet at r 7.40-8.50 ( 5 protons ) was assigned to the four protons of the two methylene groups and the hydroxylic proton. 

In the 1H NMR spectra we ve seen thus far, each different kind of proton in a molecule has given rise to a single peak. It often happens, though, that the absorption of a proton splits into multiple peaks, called a multiplet. For example, in the lH NMR spectrum of bromoethane shown in Figure 13.13, the -CH2Br protons appear as four peaks (a quartet) centered at 3.42 8 and the -CH3 protons appear as three peaks (a triplet) centered at 1.68 6. 

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