AA ligands

Fig. 7.9 Mechanisms which can interconvert trans, cis isomers of the type MfAAIjXj include (a) twist, (b) dissociation of a unidentate ligand, (c) one-ended dissociation of one AA ligand and (d) associative...

X-Ray studies on Na[(-)5 g-Co(ox)(aa)2],2H20 [aa = trans-iV-methyl-(S)-alaninate] confirm the RS configuration of the aa ligands and show the absolute configuration of the anion to be A. Fractional crystallization and column chromatography on D-lactose has been used to separate diastereoisomers of [Co(acac)2(L-Phe)] and [Co(acac)2(L-Val)]. The method was, however, unsuccessful for the corresponding L-Ala complex. ... 

Stage II Loss of one AA ligand and conversion of chlorate into chloride. 

Obtain a spectrum (300-700 nm) for [Fe(CN)5(H20)]3, each AA ligand, and each [Fe(CN)5(AA)]" complex. Record the maximum wavelength for each and determine the molar absorptivity for each complex. (To save time, only one trial for molar absorptivity determination is made. To obtain good reliable values, several trials should be made.)... 

Prepare samples of your AA ligand and [Fe(CN)5(AA)]"- complexes as well as your [Fe(CN)5(NH3)]3- starting material for IR analysis by grinding to a fine powder, a mixture of compound ( 2 mg) and dry, IR-quality KBr (100 mg) and pressing into a thin, clear, pellet. 

This experiment involves advanced theory and substantial reagent preparation that requires outside-lab prep time. The goal of this experiment is to determine the standard reduction potentials (E°, V) for a series of substituted pentacyanoferrate(II) complexes. By comparing the electrochemical behavior of each AA ligand system, information about electronic structure and solution properties will be obtained. An introduction to cyclic voltammetry is given in Appendix 2. 

Now go to Display, Vibrations. By clicking the box next to a listed frequency in the vibration window, you can see how the molecule vibrates at that frequency. View the CN- and carbonyl vibrations for the [Fe(CN)5AA]"- complexes and free met and gly. (Hint met carbonyl vibrations are at approximately 560, 1550, and 1850 Hz. Gly carbonyl vibrations are at approximately 600, 1560, and 1850 Hz.) Look for any shifts in frequency for a given vibration when the AA ligand is bound as opposed to when the ligand is free. 

List the calculated and observed vibrational frequencies for the metal-bound CN-and AA ligands and their shifts (Aw) from free forms in Table 4.6. 

Under the experimental conditions, the formation rate constant, kf = k2KiPj (1+Xip[Y-]). Assuming Kiy, <[Pg.107]

Figure 19 Anderson s c-B4-(AA)2 type complex formed by a bisporphyrin tetrapyridyl receptor (64) and two bisfzinc porphyrin) (AA) ligands.

The present paper summarizes typical examples of precise calculations and realistic approximations. In particular, volume, surface and hydration properties of several proteins of different characteristics are highlighted, including visualization of their atoms, AAs, ligands, preferentially bound water molecules (for short waters ) and water clusters, position of water-coated crevices and channels. 

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