Computational investigations into the potential use of poly(benzyl phenyl ether) dendrimers as supports for organometallic catalysts

We studied the structure and conformation of organic and organochromium pol y(benzylphenyl ether) dendrimers (PBPE dendrimers) via atomistic molecular dynamics computer simulations. The results of our computational investigati ons show that the metal carbonyl centers are available to participate in ch emical reactions. When the results of a course-grain computer simulation st udy by Murat and Grest(1) were used, this conclusion was valid for all solv ent conditions. The terminal groups of both the organic and organochromium dendrimers smaller than generation 3 (g(max) less than or equal to 3) under go significant backfolding and are capable of penetrating the central (core ) region. However in the organochromium case, for g(max) > 3 the terminal ( (benzyl)tricarbonylchromium(0)) groups do not penetrate the core region to the same extent as do the terminal (benzyl) groups in the organic dendrimer s of similar generation. This is mainly due to molecular crowding. By calcu lating the fractal dimensions we are able to determine that both dendrimer types are compact structures. However, despite their compact nature the ter minal groups of the later organochromium polymers are solvent accessible an d hence spatially available to act as catalysts in chemical reactions.