Chromophores center

If energy migration were ignored, the fluorescence kinetics of aryl vinyl polymers in solution could be expressed by the same set of rate constants as utilized for the meso- and d/-2,4-diarylpentanes. However, each chromophore in the polymer (ignoring chain ends) has two neighbors which may participate in excimer formation. A chromophore centered in a heterotactic triad, for example, would generate excimers on the syndiotactic side and on the isotactic side at the rates k M, and ki w r.r. 

Os(II) chromophore centers were found to serve as energy donors in the complexes Ospytpp and OspyZntpp (Fig. 7), in which each Os(II) center has a [(bpy)20s(C0)(py)]2+ environment. The 3MLCT state of the Os(II) donor chromophore has an emission maximum of 590 nm in CH2CI2 at room tem-... 

Figure 20. The dicopper(I) knots made of two identical chromophoric centers linked by two threads (X and Z), each of which can be of different length.

By comparison, substitution by methoxy groups at the chromophore center does not significantly affect TPA as shown for the data obtained for 58a and 58c (Table 3.7). Quantum chemical calculations show that the transition dipole moments possess the largest value along the molecular axis. 

AaAbB2 loaded with iron(II) develops a strong (e= 1,000 M cm ) chromophore centered at 625 nm, properties reminiscent of those of (peroxo)di-iron(III) species (Tables 1 and 2). 

Cotton FA, Donahue JP, Murillo CA (2003) Polyunsaturated dicarboxylate tethers connecting dimolybdenum redox and chromophoric centers absorption spectra and electronic structures. J Am Chem Soc 125 5486-5492... 

Cartoon representation of the three-dimensional structures of three different photoresponsive proteins. Left GFP with its HBDI anionic chromophore. Center the bovine visual pigment rhodopsin together with the cationic PSB11 chromophore. Right bacteriorhodopsin and its PSBAT chromophore... 

From the point of view of color the second case is of greatest importance, because the conjugation of jc-bonds can connect several chromophoric centers and create a sufficient condition for absorption in the visible region. In addition to groups with double bonds, atoms and groups with free-electron pairs also play a very important role in the molecules of colored substances, because they can take part in mesomeric shifts in the molecule and thus have a substantial influence on the color (auxochromes). However, groups can also exist which produce an opposite effect (so-called anti-auxochromes). 

E., and Taube, H. (1981). Determination of E20-E10 in Multistep Charge Transfer by Stationary-Electrode Pulse and Cyclic Voltammetry Application to Binuclear Ruthenium Ammines. Inorg. Chem., 20, 1278-1285. (c) Cotton, F. A. Donohue, J. P., and Murillo, C. A. (2003). Polyunsaturated Dicarboxylate Tethers Connecting Dimolybdenum Redox and Chromophoric Centers Syntheses, Structures, and Electrochemistry. J. Am. Chem. Soc., 125, 5436-5450. (d) Berry, J. F. Cotton, F. A., and Murillo, C. A. (2004). A Trinuclear EMAC-Type Molecular Wire with Redox-Active Ferroeenylaeetylide "Alligator Clips" Attaehed. Organometallics, 23, 2503-2506. (e) Sheng, T. Appelt, R. Comte, V., and Vahrenkamp, H. (2003). Chain-Like... 

The application of coupled oscillator and related theories to the investigation of nucleic acids and polynucleotides has been reviewed by Brahms. The optical activities of single nucleosides and derivatives have been calculated by a coupled oscillator theory in which the tt-tt transitions of the bases were decomposed into individual bond-bond transition moments which were then coupled by the dipolar coupling mechanism. Apparently such a treatment was necessary to account for deficiencies in the simple approach of chromophore-centered dipole transition moments. 

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