Nanostructuring of Hybrid Silicas: New Approach to Bridged Silsesquioxanes with Purine-Pyrimidine Base Pairs as Bridging
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1007-S02-03
Nanostructuring of Hybrid Silicas: New Approach to Bridged Silsesquioxanes with Purine-Pyrimidine Base Pairs as Bridging Units Michel WONG CHI MAN1, Guilhem ARRACHART1, Carole CARCEL1, Joël J.E. MOREAU1, Christian BONHOMME2, Florence BABONNEAU2, Gaëlle CREFF3, Jean-Louis BANTIGNIES3, Philippe DIEUDONNE3, and Bruno ALONSO4 1 Architectures Moléculaire et Matériaux Nanostructurés, ICG Montpellier (UMR 5253) UMIICNRS-ENSCM-UMI, 8 rue de l'école normale, Montpellier, 34296, France 2 Laboratoire de Chimie de la Matière Condensée de Paris, 4 Place Jussieu, Paris, 75005, France 3 Laboratoire des Colloïdes, Verres et Nanomatériaux, Place Eugène Bataillon, Montpellier, 34095, France 4 MACS, ICG Montpellier (UMR 5253) UMII-CNRS-ENSCM-UMI, 8 rue de l'école normale, Montpellier, 34296, France ABSTRACT A new route to synthesize hybrid silica-based network with bridging organic units via molecular recognition is described. The hydrolysis of two monosilylated complementary base pairs, one bearing an adenine fragment and the other a thymine fragment leads to the formation of a powdered sample that has been characterized by Scanning Electron Microscopy (SEM), Powder X-ray Diffraction (PXRD) FTIR and solid state NMR (1H, 13C and 29Si). This last technique proved to be extremely powerful to directly demonstrate the occurrence of heteroassembly of the nucleobase-based silylated fragments, through the use of two-dimensional 1 H double-quanta MAS-NMR that could probe spatial proximities between the thymine NH groups and the adenine NH2 groups. INTRODUCTION Organo-bridged silsesquioxanes are commonly synthesized by the hydrolyticcondensation of silyl organics of type (RO)3Si-X-Si(OR)3 (X=organic bridging fragment) [1,2]. Through this Bottom-Up approach, functional hybrid materials are obtained with targeted properties resulting from the organic moieties which are regularly distributed throughout the whole silica network owing to the strong covalent Si-C bonds [3]. Recently, we showed that the combination of urea groups as self-associative groups with the organic fragment allowed a good control of the organisation of these solids at various scale lengths [4,5]. Here we report a new approach to bridged silsesquioxanes starting from two different monotrialkoxysilyl organics in which the organic fragments can interact with each other by weak interactions. The hydrolysis of this new system leads to a new type of bridged silsesquioxanes in which the two organic fragments linked together to form the bridging unit (Figure 1). H 2O
M.R. (EtO)3Si
+
Si(OEt)3
M.R. = Molecular Recognition
(EtO)3Si
Si(OEt)3
= bridging fragment
O 1.5Si
SiO 1.5 n
Figure 1. Bridged silsesquioxanes obtained from two different monotrialkoxysilyl organics with molecular recognition properties In this work, we present the results obtained from two silyl derivatives of complementary base pairs consisting of adenine and thymine derivatives capable to assemble through molecular recognition H-bonds interactions. Adenine can bind to thymine via two hydrogen
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