Wavelength irradiation

As a consequence of the rigid face-to-face orientation, there are strong electronic interactions between the benzene rings in the dibenzo-anellated isodrin derivative. Irradiation with 254-nm UV light gave rise to a 7 3 equilibrium mixture of the educt with the [6 -I- 6]cycloaddition isomer. At an irradiation wavelength of 300 nm the cycloaddition wa completely reversed. 

The benzo[Z)] fused systems participate in a number of [2 + 2] cycloaddition reactions (81JOC3939, 81TL521). The photocycloaddition products of benzo[Z)]thiophenes and DMAD are dependent on the irradiation wavelength (Scheme 56). 

Many studies relate to the effect of irradiation wavelength per se. Irradiation of virgin PVC under nitrogen with (266—... 

Figure 1. Spectrum of Ru3(CO) 2 in octane. Quantum yields for photosubstitution and photofragmentation in 25°C argon flushed octane in the presence in 0.012 M P(OCH3>3 represented as a function of irradiation wavelength (from reference 5).

The most notable feature of these intrazeolite photooxygenations (Fig. 30) is that the oxygen CT band experiences a dramatic bathochromic shift in comparison to solution. This was detected initially by recording the product growth as a function of irradiation wavelength (laser reaction excitation spectrum)98,110 and was later verified by direct observation using diffuse reflectance UV-Vis spectroscopy.111 For example, 2,3-dimethyl-2-butene CT-absorbance is shifted to lower energy by more than 300 nm... 

The formation of silyl radicals in the exhaustive photolysis of the silane polymers was indicated by the isolation of disilanes of general structure (HSiRR SiRR H) as shown in Table 1. These materials accumulate in the photolysate and are photostable as they absorb only weakly at the irradiation wavelength (254 nm). Longer chain silanes are presumably continuously degraded under the conditions of the exhaustive irradiation. 

Figure 3. Yield of adduct I SiSiB H from irradiation of poly(di-n-butylsilane) in the presence of triethylsilane as a function of the irradiation wavelength.

Table 16. Stationary state conversion to DHP (c, %) and extinction coefficient ratio ca/cb a function of irradiation wavelength (A.,nm)...

Quantum yields for all these systems are independent of irradiating wavelength. 

Considerable data are available concerning the photolysis of m-Cr(en)2(OH)2 +. Thermally, this system was found to give only isomerization to fra 5,-Cr(en)2(OH)2 + photochemically, both isomerization and aquation are observed to occur in proportions which depend upon irradiating wavelength and temperature. Data are given in Table III, from which it is clear that photoisomerization requires an activation... 

Complex Irradiating wavelength, m/i Reaction mode Quantum yield4 Refs. 

Complex Irradiating wavelength, mil Reaction mode Quantum yieldd Refs. 

UV-Light Source Irradiation Wavelength (nm) Light Intensity h E s-1 cm-2 Polymerization Rate Rp (mol L-1 s1) Quantum Yield ( ) (mol E-1)... 

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