Conjugation shifts

Conjugation shifts Amax to longer wavelengths in alkenes. The conjugated diene 2-methyl-l,3-butadiene has the longest wavelength absorption, Amax = 222 nm. The isolated diene 1,4-pentadiene and the simple alkene cyclopentene both absorb below 200 nm. 

Conjugation shifts a carbonyl absorption to lower frequencies. 

Conjugation shifts to longer wavelengths in alkenes. The conjugated diene 2-methyl-l,3-... 

Conjugation of two chromophores not only results in a bathochromic shift but increases the intensity of the absorption. These two effects are of prime importance in the use and interpretation of eleetronic spectra of organic molecules, because conjugation shifts the selective light absorption of isolated chromophores from a region of the spectrum that is not readily accessible to a region that is... 

Some famihar compounds may serve to imderscore these relationships between the absorption spectrum and the observed color. The structural formulas of these examples are shown. Notice that each of these substances has a highly extended eonjugated system of electrons. Such extensive conjugation shifts their electronic spectra to such long wavelengths that they absorb visible hght and appear colored. 

L. D. (2004). Quantum dot-antibody and aptamer conjugates shift fluorescence upon binding bacteria. Biochem Biophys Res Commun 325, 739-743. 

Figure 6.6 Increased ligand conjugation shifts the absorption maxima to the red.

Another polymer-attached fluorophore that binds metal ions is the porphyrin moiety (5-(p-methacrylamidophenyl)-10,15,20-triphenylporphjnin (MATPP) (Scheme 8.3). It can be polymerized into a copolymer that is then electrospun into nanofibers d 300 nm) (Wan, L.-S., et al. 2006). Metal conjugation shifts the fluorescence emission wavelength of these... 

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