Absorption Spectra of Conjugated Dyes

2448 WordsMar 4, 201410 Pages
Absorption Spectra of Conjugated Dyes Abstract: The absorption spectra of a series of three diphenyl dyes and three polymethine dyes were measured and interpreted by ultra-violet spectroscopy. The spectrums of these dyes were compared to the estimated wavelength of absorbance through the particle-in-a-box model. Maximum wavelengths of 523, 604, 707, 330, 354 and 375 and box lengths of 1.053, 1.284, 1.535, 0.707, 0.867, and 1.011 nm, for 1,1’-diethyl-2,2’-cyanine iodide, 1,1’-diethyl-2,2’-carbocyanine chloride, 1,1’-diethyl-2,2’-dicarbocyanine iodide, 1,4-diphenyl-1,3-butadiene, 1,6-diphenyl-1,3,5-hexatriene, and 1,8-diphenyl-1,3,5,7-octatetraene were experimental obtained. Both spectral and physical measurements proved Kuhn’s…show more content…
Based on the above, the length of the one-dimensional box is L=(p+3)l, where l is the bond length between atoms on a benzene molecule. Equation 3 can be rewritten as λ (nm) = 8mcl2(p+3+α)2h(p+4) = 63.7 (p+3+α)2p+4 (4) where l=0.139 pm and α is a constant for a series of dyes.3 Experimental: The following polymethines were dissolved in methanol and the diphenyls were dissolved in cyclohexane to give dilute solutions: 1,1’-diethyl-2,2’-cyanine iodide, 1,1’-diethyl-2,2’-carbocyanine chloride, 1,1’-diethyl-2,2’-dicarbocyanine iodide, 1,4-diphenyl-1,3-butadiene, 1,6-diphenyl-1,3,5-hexatriene, and 1,8-diphenyl-1,3,5,7-octatetraene. The concentrations of 1,1’-diethyl-2,2’-cyanine iodide, 1,1’-diethyl-2,2’-carbocyanine chloride, 1,1’-diethyl-2,2’-dicarbocyanine iodide were 1.00 × 10-6 M, 5.02 × 10-7 M and 1.00 × 10-6 M, respectively and were made together by Groups B, C, and D. The concentrations of 1,4-diphenyl-1,3-butadiene, 1,6-diphenyl-1,3,5-hexatriene, and 1,8-diphenyl-1,3,5,7-octatetraene were 5.30 × 10-6 M, 5.20 × 10-6 M, and 5.00 × 10-6 M, respectively and were made by Group A. Each solution was made dilute enough to be perceived accurately with a smooth maximum absorbance below 1 Au. Shown in Figure 1 and Figure 2, absorbances were taken between 190 and 1100 nm for the
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