Photodimerization of substituted stilbenes

Abstract

cyanogen in 35 ml of ethyl acetate was prepared in the usual manner in the dark at 0°. To this cold solution was added 7.2 mmol of I in 20 ml of ethyl acetate over at 15-min period. At this point tic indicated that no thiol remained. The appropriate thioether (7.2 mmol) was dissolved in 25 ml of ethyl acetate and added in one portion to the reaction mixture. The solution was stirred in the dark for 2 hr at 0°, allowed to warm to room temperature, and stirred for an additional period of time (3-33 hr depending on the reaction progress as demonstrated by tic). After reaction was complete the solution was diluted to 200 ml with ethyl acetate and washed with 5% sodium bicarbonate solution, water, and saturated brine. The organic extract was dried and evaporated in vacuo, and the residue was triturated with hexane to remove the trityl thiocyanate. The resulting powder was purified by recrystallization or chromatography followed by recrystallization. The reported yields (Table I) are based on the amount of purified product.B. Acidic Solvents.-To a cold, stirred solution containing 9 mmol of thio cyanogen in 35 ml of ethyl acetate was added 7.2 mmol of I in 20 ml of trifluoroacetic acid (TEA). After 10 min,

Azastilbenes. 1. Synthesis, characterization, and structure

“…It should be noticed that III (for which the molecular structure is asymmetric) presents an apparent centrosymmetry due to disorder at the positions 2 and 2'. These positions are occupied 50% of the time, alternatively by 9.810 (4) 7.822 (2) 11.740 (4) 9.190 (4) 11.52 (2) 16.079 (5) 12.722 (4) 8.119 (3) 13.644 (4) 11.901 (3) b, A 7.206 (2) 10.562 (4) 5.385 (2) 5.894 (2) 5.26 (1) 6.399 (2) 14.843 (5) 7.017 (2) 10.489 (3) 11.275 (3) c, A…”

Photo‐Cross‐Linking of Polymethacrylates with Stilbene Chromophores in the Side Chains

“…The differentiation between the head-to-head fraction 8/9 and the head-to-tail fraction 10/ 11 was achieved by the orthogonal decay of the molecular ions (EI, linked scan technique) [41].…”

π–π Interaction Energies as Determinants of the Photodimerization of Mono-, Di-, and Triazastilbenes

“…Similar comparisons of irradiation results and the polarity of extended π systems have been made, but only in a generalized fashion. 24 , 33 , 60 Our work in this area was only partially successful, largely due to the unexpected crystal packing of 15 and 16 . If these compounds are excluded from the analysis shown in Figure 5 , the hypothesized relationship between binding energy and the percent composition of the htt r-ctt dimer in the reaction mixture and the inverse relationship between interaction energy and t 1/2 become apparent.…”