Paramagnetism, poly derivatives

A couple of papers have dealt with dendrimers. Wang and co-workers reported a study of host-guest behaviour of poly(amidoamine) dendrimers with various functionalities interacting with paramagnetic TEMPO derivatives. They measured the PRE effects on the polymer protons. Neelov et investigated second- and fourth-generation lysine dendrimers by MD simulations, combined with relaxation rates measurements. 

However, disorder appears to be crucial in the occurrence of photoexcited paramagnetic centers since irradiation of single crystal samples, e.g. poly TS, has no effect. The energy levels in the low energy absorption tail of the disordered samples play an important part. It is not clear if these derive from excitonic or interband transitions but it should be noted that in principle any distortion of the polymer chain can lead to defect states in the optical gap ( ) and that the weak absorption tail in crystals is a major factor determining photoconduction (9 ). Thus, it appears that a basis exists for the correlation of structure and the intrinsic absorption spectra but that further efforts are required to obtain a better understanding of defect states and their spectroscopic properties. 

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