The interest on diffusion and trapping of small molecules inside dendrimers has increased in recent years because of the new synthetic strategies that have allowed to achieve a high control of the supramolecular structure of these macromolecules. Crucial, in this regard, are the dimension and topology of intra- and inter-molecular cavities that can capture small molecules, along with the nature (physical or chemical) of the penetrant/dendrimer interaction. In recent years a divergent method to synthesize polyphenylene dendrimers with different cores and up to the fourth generation has been developed [1]. Owing to their semi-rigid framework, these monodisperse polyaromatic dendrimers are of interest with respect to the design of nanostructures with invariant shape [2] and because of their cavities they are promising materials for selective sensor layers [3]. In this work we present a computational study on both intra-molecular and inter-molecular properties of polyphenylene dendrimers with a three-substituted phenyl core. The first objective is to assess the degree of intra-molecular shape persistence at different temperatures. To this end atomistic molecular dynamics simulations have been carried out at 80 K and room temperature. It is found that out of the six possible core conformations only four are stable and jumps among these are possible at room temperature, although core conformational jumps induce only slight shape modifications of the polyphenylene dendrimer. The second objective of this study is to explore whether aggregates of these peculiar three-dimensional structures can form stable inter- and intra-molecular cavities and to investigate their trapping capacity. To this end, accessible surfaces and trapping sites have been studied by employing an in-house written algorithm in which the preferential approaching paths for external molecules moving toward intra- or inter-dendrimer cavities (trapping sites) are evaluated on the basis of a selected grid of points used by the penetrant to explore the accessible volume and with a Monte Carlo sampling. [1] A. J. Berresheim, M.Müller, K. Müllen, Chem. Rev., 99 (1999), 1747. [2] F. Morgenroth, A. J. Berresheim, M.Wagner, K. Müllen, Chem. Commun., 10 (1998), 1139. [3] M. Schlupp, T. Weil, A. J. Berresheim, U. M. Wiesler, J. Bargon, K. Müllen, Angew. Chem. Int. Ed. 40 (2001), 4011.
SHAPE PERSISTENCE AND TRAPPING IN POLYPHENYLENE DENDRIMERS: NEW CARBON BASED SENSOR MATERIALS?
CARBONE, PAOLA;NEGRI, FABRIZIA;
2005
Abstract
The interest on diffusion and trapping of small molecules inside dendrimers has increased in recent years because of the new synthetic strategies that have allowed to achieve a high control of the supramolecular structure of these macromolecules. Crucial, in this regard, are the dimension and topology of intra- and inter-molecular cavities that can capture small molecules, along with the nature (physical or chemical) of the penetrant/dendrimer interaction. In recent years a divergent method to synthesize polyphenylene dendrimers with different cores and up to the fourth generation has been developed [1]. Owing to their semi-rigid framework, these monodisperse polyaromatic dendrimers are of interest with respect to the design of nanostructures with invariant shape [2] and because of their cavities they are promising materials for selective sensor layers [3]. In this work we present a computational study on both intra-molecular and inter-molecular properties of polyphenylene dendrimers with a three-substituted phenyl core. The first objective is to assess the degree of intra-molecular shape persistence at different temperatures. To this end atomistic molecular dynamics simulations have been carried out at 80 K and room temperature. It is found that out of the six possible core conformations only four are stable and jumps among these are possible at room temperature, although core conformational jumps induce only slight shape modifications of the polyphenylene dendrimer. The second objective of this study is to explore whether aggregates of these peculiar three-dimensional structures can form stable inter- and intra-molecular cavities and to investigate their trapping capacity. To this end, accessible surfaces and trapping sites have been studied by employing an in-house written algorithm in which the preferential approaching paths for external molecules moving toward intra- or inter-dendrimer cavities (trapping sites) are evaluated on the basis of a selected grid of points used by the penetrant to explore the accessible volume and with a Monte Carlo sampling. [1] A. J. Berresheim, M.Müller, K. Müllen, Chem. Rev., 99 (1999), 1747. [2] F. Morgenroth, A. J. Berresheim, M.Wagner, K. Müllen, Chem. Commun., 10 (1998), 1139. [3] M. Schlupp, T. Weil, A. J. Berresheim, U. M. Wiesler, J. Bargon, K. Müllen, Angew. Chem. Int. Ed. 40 (2001), 4011.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
