88-89 magnetic circular dichroism

B along the z axis raises thep+ orbital in energy by —e/2m) B ti and lowersp by the same amount (Fig. 9.12). At a field strength of 1 T, the separation between p+ and p is about 0.5 cm The 2s orbital, with Z = 0, has no orbital angular momentum and is unaffected by magnetic fields. 

Magnetic fields also can modify the mixing of the ground and excited states with other states at higher or lower energy [57,58]. However, this effect probably makes a relatively minor contribution to the MCD spectrum in most cases. 

Calculate the rotational strength (9i) of the transition represented by the CD spectrum of Fig. E.l. 

What are the exciton rotational strengths ( ex) of the two exciton bands of the dimer discussed in Exercise 8.1 Explain your answer. 

The dimer sketched in Fig. E.2 is similar to that of Exercise 8.1, except that 

Instrumentation. The spectroelectrochemical cell described by Kobayashi and Ni-shiyama includes a minigrid working electrode in a glass cuvet (approx. 3 mm optical pathlength) attached to the bottom of a cylindrical cell body with counter electrode and reference electrode mounted therein. The cuvet is exposed to the magnetic 

C-terms are related to the A-terms and are inversely temperature dependent and thus dominate the MCD spectra of bioinorganic compounds which are often acquired at low temperatures [10]. The temperature dependency is due to the higher population of the Zeeman-split ground state, as the population of the lowest state rises with lower temperatures, the C-term intensity increases. For a C-term to be observed, orbital degeneracy is required in the ground state (opposed to the 

B-terms arise from field induced mixing of excited and ground states to other states with Zeeman interaction [10]. States with similar energy are prone to mix more. These transitions have absorption-band shape and are temperature independent. However, if the two mixed states are degenerate in energy, an A-term is observed. When the states are similar in energy then a derivative shaped signal is observed (pseudo A-term) [10]. 

MCD of model complexes is extremely useful for the interpretation of features found in enzyme spectra. In small models the coordination geometry can be easily controlled and distinct transitions for 4- (negative band a 600 50 nm and less intense positive band at 525 50 nm), 5- (negative bands between 650 and 450 nm) and 6-coordinate Co(II) (sharp negative band around 500 50 nm) can be assigned [5]. Band intensities can also be an indicator for the coordination number of a Co(ll) ion [5]. While 4- and 5-coordinate Co(II) displays bands of substantial intensity at room temperature the transitions from 6-coordinate Co(II) are up to 10 times less intense. At very low temperature, however, the latter are often more intense than 5-coordinate transitions. A number of dinuclear Co(II) complexes have been studied by MCD [12, 14, 17], and with the aid of VTVH MCD magnetic coupling parameters have been obtained [14]. 

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MCD Magnetic circular dichroism. See optical rotatory dispersion. 

Baudelet F, Odin S, Giorgetti C, Dartyge E, Itie J P, Polian A, Pizzini S, Fontaine A and Kappler J P 1997 PtFej Invar studied by high pressure magnetic circular dichroism J. Physique IV C7 441... 

Goldbeck R A, Kim-Shapiro D B and Kliger D S 1997 Fast natural and magnetic circular dichroism Annu. Rev. Rhys. Chem. 48 453-79... 

Xie X L and Simon J D 1990 Picosecond magnetic circular dichroism spectroscopy J. Rhys. Chem. 94 8014-16... 

The UV spectrum of a complex conjugated molecule is usually observed to consist of a few broad band systems, often with fine structure, which may be sharpened up in non-polar solvents. Such a spectrum can often be shown to be more complex than it superficially appears, by investigation of the magnetic circular dichroism (MCD) spectrum, or by introduction of dissymmetry and running the optical rotatory dispersion (ORD) or circular dichroism (CD) spectrum. These techniques will frequently separate and distinguish overlapping bands of different symmetry properties <71PMH(3)397). 

Azaphenanthrenes magnetic circular dichroism, 2, 129 Azaphenoxathiin synthesis, 3, 985... 

Isoquinol-4(l H)-one, 2,3-dihydro-synthesis, 2, 73 Isoquinolinones from isocoumarins, 3, 691 magnetic circular dichroism, 2, 129 synthesis,... 

Purines, N-alkyl-N-phenyl-synthesis, 5, 576 Purines, alkylthio-hydrolysis, 5, 560 Mannich reaction, 5, 536 Michael addition reactions, 5, 536 Purines, S-alkylthio-hydrolysis, 5, 560 Purines, amino-alkylation, 5, 530, 551 IR spectra, 5, 518 reactions, 5, 551-553 with diazonium ions, 5, 538 reduction, 5, 541 UV spectra, 5, 517 Purines, N-amino-synthesis, 5, 595 Purines, aminohydroxy-hydrogenation, 5, 555 reactions, 5, 555 Purines, aminooxo-reactions, 5, 557 thiation, 5, 557 Purines, bromo-synthesis, 5, 557 Purines, chloro-synthesis, 5, 573 Purines, cyano-reactions, 5, 550 Purines, dialkoxy-rearrangement, 5, 558 Purines, diazoreactions, 5, 96 Purines, dioxo-alkylation, 5, 532 Purines, N-glycosyl-, 5, 536 Purines, halo-N-alkylation, 5, 529 hydrogenolysis, 5, 562 reactions, 5, 561-562, 564 with alkoxides, 5, 563 synthesis, 5, 556 Purines, hydrazino-reactions, 5, 553 Purines, hydroxyamino-reactions, 5, 556 Purines, 8-lithiotrimethylsilyl-nucleosides alkylation, 5, 537 Purines, N-methyl-magnetic circular dichroism, 5, 523 Purines, methylthio-bromination, 5, 559 Purines, nitro-reactions, 5, 550, 551 Purines, oxo-alkylation, 5, 532 amination, 5, 557 dipole moments, 5, 522 H NMR, 5, 512 pJfa, 5, 524 reactions, 5, 556-557 with diazonium ions, 5, 538 reduction, 5, 541 thiation, 5, 557 Purines, oxohydro-IR spectra, 5, 518 Purines, selenoxo-synthesis, 5, 597 Purines, thio-acylation, 5, 559 alkylation, 5, 559 Purines, thioxo-acetylation, 5, 559... 

Pyridinium iodide, 4,4 (l,3,4-thiadiazole-2,5-diyl)-bis(l-methyl)-reduction, 6, 564 Pyridinium ion, Af-methyl-as metabolite of pyridine, 1, 234 Pyridinium ions hydrogen bonding to water mass spectrometry, 2, 135 magnetic circular dichroism, 2, 129 NMR, 2, 121... 

IR spectroscopy, 2, 153 cycloaddition reactions, 1, 479 halogenation, 2, 203 hydrogenation, 2, 46 intermolecular cycloadditions, 2, 307 magnetic circular dichroism, 2, 129 N-oxides... 

In a few instances the technique of magnetic circular dichroism (MCD) spectroscopy has been used to corroborate assignments based on UV-visible spectroscopy. For example, the assignment of the intense 360 nm band for [S,N,Y to a r (2e") r (2a2") (HOMO LUMO) excitation has been confirmed by the measurement of the MCD spectrum of The MCD spectrum of [S4N3] indicates that each of the... 

Results from an array of methods, including X-ray absorption, EXAFS, esr and magnetic circular dichroism, suggest that in all ureases the active sites are a pair of Ni" atoms. In at least one urease,these are 350 pm apart and are bridged by a carboxylate group. One nickel is attached to 2 N atoms with a fourth site probably used for binding to urea. The second nickel has a trigonal bipyramidal coordination sphere. 

Data on the protonation sites for a variety of azaindolizines have been summarized in the previous survey (76AHCS1, p. 536).Tlie measured magnetic circular dichroism spectra for 14 azaindolizines confirmed with some corrections the protonation sites of polyazaheterocycles previously reported and also established the conjugated acid structures of additional compounds (85JOC302).Tlie data are summarized in Scheme 1. 

E. Dartyge, and A. Fontaine. K edge x-ray magnetic circular dichroism in molecular based magnets. Physica B 208 209 765 (1995). 

The magnetic circular dichroism (MCD) spectrum of matrix-isolated... 

A. Electronic Spectroscopy Absorption, Circular Dichroism, and Magnetic Circular Dichroism (MCD) Spectroscopy... 

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