Cinnamoyloxy group

The same tendency was observed in the cases of stylene,stilbene( 6) and cinnamoyloxy group( 6). The calculated value of Ti is 21700 cm". The So-)Ti absorption spectrum in EtI gives only tail near the calculated value. The emission spectrum in EPA gave such a phosphorescence as was shown in Fig.3. The Intensity Increases with the irradiation time. Therefore, it is clear that the emission spectrum is that of the photodecomposed product, which is estimated to be aniline from the similarity of the phosphorescence of the authentic sample. 

The lowest triplet state energy calculated by the PPP method is 18755 cm"1 in accordance with the observed value. The MIM calculations show that the main contribution to Ti is the LE of cinnamoyloxy group (69 ) and the energy difference between Ti and T2 is only 3200 cm . We can understand from the small difference that the only one vibrational structure appears in Pig.5(b) and can also estimate that the vibrational structiure arises from the central double bond of cinnamoyloxy group and not from azide. The T2 state has the same character as the Ti state of phenylazide where the contribution of the LE function of azide group is remarkable(55.02 in this case). 

Figure la. Atomic configuration of cinnamoyloxy group. All the angles are 120°. 

Figure Ic. (bottom) Examples of LE and CT configurations of cinnamoyloxy group (a), LE configuration of emylene group (b), CT configuration from ethylene to carboxyl group...

Figure 3a. Comparison of the calculated values with the experimental ones on the electronic transition energies and oscillator strengths of trans-cinnamoyloxy group...

Figure 4. Molecular diagrams of various electronic states of cinnamoyloxy group in the electron system...

Table 3. The Contributions of Various Electronic Configurations of the HIM model for the State Functions of the PPP model of trans-Cinnamoyloxy Group %)...

The same phenomena is also found in the S3 transition. In the cases of aniline, phenol, etc., of which ll-electron systems exactly belong to C2v point group, the weak transitions arising from Bi and 62 of benzene are exclusively separated in the direction of long- and short-axis, respectively(j8 ). Therefore, we can consider that the phenomena arise from the fact that Tl-electron system of cinnamoyloxy group belongs to Cs and not to C2v ssanmetry. 

Tables. Charge Distributions in the Various Electronic States of trans-Cinnamoyloxy Group...

Table 6. The Resemblance of the Sj State Function of Stilbene and the S2 State Function of Cinnamoyloxy Group-...

Since it does not suffer dark reactions, poly (vinyl cinnamate) (PVCi) is one of the most excellent and practically important photosensitive polymers and has been widely investigated(1). Recently, it was found that a more highly photosensive polymer than PVCi was obtained by the separation of cinnamoyloxy group through -CH2-CH2-O-from the main chain of the vinyl polymer(2). The fact means that by... 

Few reports(, 11 ) have been published on the electronicstates of cinnamoyloxy group although there are many of those on the photochemical reactions ). In this paper, the electronic structures in the excited states of cinnamoyloxy group are clarified by the molecular orbital calculations and the spectroscopic procedures, and discussed in connection with the intensity of light absorption, photochemical reaction processes and energy transfers in the sensitization which are important in the comprehensive understanding of the photosensitive polymer. 

UV Spectrumof Poly (vinyl cinnamate )(PVCi). The UV spectrum of PVCi in tetrahydrofuran solution is identical with that of ethyl cinnamate and it is believed to be the absorption by cinnamoyloxy group. The main peak(6-10 ) of the latter has the absorption maximum at 36750 cm in n-hexane and is considered to be (Tt >TT )1 transition from the solvent effects. There is another weak absorption near 34000 cnT which is clearly observed at low temperatures(at 77°K in EPA solutions)(15)... 

The authors revised the PPP method in a few points, especially in the formulation for the two center Coulomb repulsion integrals, in order to calculate the correct values of the triplet state energies(5) The application of the revised method to the calculation of the electronic states of cinnamoyloxy group was found to reproduce well the experimental values of its electronic transitions. The results are also shown in Pig.3. 

The Excited States of Poly (vinyl cinnamate) and their Photochemical Reactivities. The photochemical reaction of PVCi is believed to be intermolecular crosslinking of the polymer chains by the formation of the four-membered ring from the central double bonds of cinnamoyloxy groups(6), and it is known that many experimental results from the photochemical reaction are interpreted well(6) if we can postulate that the reaction is the concerted cycloaddition according to the Woodward-Hoffmann s rule(j 3). This means that the four-membered ring... 

Analyses of the Electronic Transitions of Poly(vinyl cinnamate). The concerted cycloaddition of cinnamoyloxy group is essentially the reaction of the central double bond. Therefore, we can expect to obtain the clearer image than that hitherto considered in the photochemical reaction if the contributions of the central double bond for the excited states are calculated quantitatively. It is known that the state functions of PPP model can be rewritten to the linear combinations of LE and CT(charge transfer) functions of MIM method(7 ) when we use the same atomic orbitals as the base functions (q ). Using the technique, the state functions in Table 2 are rewritten and the results are collected in Table 3 The relationship between these two methods is illustrated in Fig.1 (b), (c). 

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