The self-assembly of small molecular modules into non-covalently linked polymeric nanostructures is a subject of continuous interest [1]. In particular, supramolecular structures with a high degree of order can be obtained through the self-association of organic molecules on flat solid surfaces. Such structures can be used as scaffolds to position electrically/optically active groups in pre-determined locations in 2D [2] thereby paving the way towards a wide range of applications, e.g. in electronic and optical devices. Among weak interactions, H-bonding offers high control over the process of molecular self-assembly because it combines reversibility, directionality, specificity and cooperativity. Such a unique character is the basis of sophisticated programs for self-assembly such as those based on the Watson–Crick base pairing which directs the formation of the helical structure of DNA. While the self-assembly of guanines into G-quartet based architectures on solid surfaces has been studied by Scanning Tunneling Microscopy (STM) under ultrahigh vacuum (UHV) [3], STM explorations at the solid-liquid interface have been primarily carried out on guanosine derivatives [4]. In this lecture we will present a sub-molecularly resolved STM study at the solid-liquid interface of the metal templated reversible assembly/reassembly process of a N9-alkylguanine into highly ordered quartets and ribbons on highly oriented pyrolitic graphite (HOPG) surfaces. The self-assembly of guanine derivatives on HOPG has been studied as neat component[5] and upon sub-sequent addition of cryptand [2.2.2] molecules, potassium picrate and triflic acid to trigger the reversible interconversion between two different highly ordered supramolecular motifs, i.e. H-bonded ribbon and G-quartet based architectures. In-situ STM imaging provided the first direct evidence on the sub-nm scale of a dynamer operating at surfaces. [6] Finally we will also provide the first example of sub-molecularly resolved vertically oriented switchable chromophores in physisorbed monolayers by monitoring the cis-trans isomerization of a physisorbed azobenzene at surfaces. [7] The nanoscale visualization of such supramolecular interconversion at the solid-liquid interface opens new avenues towards understanding the mechanism of formation and functioning of complex architectures. Furthermore, the in-situ reversible assembly and re-assembly between two highly ordered supramolecular structures at a given surface represents the first step towards the generation of nanopatterned responsive architectures. [1] J. M. Lehn, Science, 295, 2002, 2400. [2] G. P. Spada, S. Lena, S. Masiero, S. Pieraccini, M. Surin, P. Samorì, Adv. Mater., 2008, 20, 2433; A. Ciesielski, L. Piot, P. Samorì, A. Jouaiti, M. W. Hosseini, Adv. Mater., 2009, 21, 1131. [3] R. Otero, M. Schock, L. M. Molina, E. Laegsgaard, I. Stensgaard, B. Hammer, F. Besenbacher, Angew. Chem. Int. Ed., 2005, 44, 2270. [4] G. Gottarelli, S. Masiero, E. Mezzina, S. Pieraccini, J. P. Rabe, P. Samorì, G. P. Spada, Chem. Eur. J., 2000, 6, 3242; T. Giorgi, S. Lena, P. Mariani, M. A. Cremonini, S. Masiero, S. Pieraccini, J. P. Rabe, P. Samorì, G. P. Spada, G. Gottarelli, J. Am. Chem. Soc., 2003, 125, 14741; S. Lena, G. Brancolini, G. Gottarelli, P. Mariani, S. Masiero, A. Venturini, V. Palermo, O. Pandoli, S. Pieraccini, P. Samorì, G. P. Spada, Chem. Eur. J., 2007, 13, 3757. [5] A. Ciesielski, R. Perone, S. Pieraccini, G.P. Spada, P. Samorì, Chem. Commun 2010, 46, 4493. [6] A. Ciesielski, S. Lena, S. Masiero, G. P. Spada, P. Samorì, Angew. Chem. Int. Ed. 2010, 49, 1963. [7] D. Bléger, A. Ciesielski, P. Samorì, S. Hecht, 2010 submitted.

NANOSCALE MONITORING OF RESPONSIVE SUPRAMOLECULAR NANOSTRUCTURES AT THE SOLID-LIQUID INTERFACE

LENA, STEFANO;MASIERO, STEFANO;SPADA, GIAN PIERO;
2010

Abstract

The self-assembly of small molecular modules into non-covalently linked polymeric nanostructures is a subject of continuous interest [1]. In particular, supramolecular structures with a high degree of order can be obtained through the self-association of organic molecules on flat solid surfaces. Such structures can be used as scaffolds to position electrically/optically active groups in pre-determined locations in 2D [2] thereby paving the way towards a wide range of applications, e.g. in electronic and optical devices. Among weak interactions, H-bonding offers high control over the process of molecular self-assembly because it combines reversibility, directionality, specificity and cooperativity. Such a unique character is the basis of sophisticated programs for self-assembly such as those based on the Watson–Crick base pairing which directs the formation of the helical structure of DNA. While the self-assembly of guanines into G-quartet based architectures on solid surfaces has been studied by Scanning Tunneling Microscopy (STM) under ultrahigh vacuum (UHV) [3], STM explorations at the solid-liquid interface have been primarily carried out on guanosine derivatives [4]. In this lecture we will present a sub-molecularly resolved STM study at the solid-liquid interface of the metal templated reversible assembly/reassembly process of a N9-alkylguanine into highly ordered quartets and ribbons on highly oriented pyrolitic graphite (HOPG) surfaces. The self-assembly of guanine derivatives on HOPG has been studied as neat component[5] and upon sub-sequent addition of cryptand [2.2.2] molecules, potassium picrate and triflic acid to trigger the reversible interconversion between two different highly ordered supramolecular motifs, i.e. H-bonded ribbon and G-quartet based architectures. In-situ STM imaging provided the first direct evidence on the sub-nm scale of a dynamer operating at surfaces. [6] Finally we will also provide the first example of sub-molecularly resolved vertically oriented switchable chromophores in physisorbed monolayers by monitoring the cis-trans isomerization of a physisorbed azobenzene at surfaces. [7] The nanoscale visualization of such supramolecular interconversion at the solid-liquid interface opens new avenues towards understanding the mechanism of formation and functioning of complex architectures. Furthermore, the in-situ reversible assembly and re-assembly between two highly ordered supramolecular structures at a given surface represents the first step towards the generation of nanopatterned responsive architectures. [1] J. M. Lehn, Science, 295, 2002, 2400. [2] G. P. Spada, S. Lena, S. Masiero, S. Pieraccini, M. Surin, P. Samorì, Adv. Mater., 2008, 20, 2433; A. Ciesielski, L. Piot, P. Samorì, A. Jouaiti, M. W. Hosseini, Adv. Mater., 2009, 21, 1131. [3] R. Otero, M. Schock, L. M. Molina, E. Laegsgaard, I. Stensgaard, B. Hammer, F. Besenbacher, Angew. Chem. Int. Ed., 2005, 44, 2270. [4] G. Gottarelli, S. Masiero, E. Mezzina, S. Pieraccini, J. P. Rabe, P. Samorì, G. P. Spada, Chem. Eur. J., 2000, 6, 3242; T. Giorgi, S. Lena, P. Mariani, M. A. Cremonini, S. Masiero, S. Pieraccini, J. P. Rabe, P. Samorì, G. P. Spada, G. Gottarelli, J. Am. Chem. Soc., 2003, 125, 14741; S. Lena, G. Brancolini, G. Gottarelli, P. Mariani, S. Masiero, A. Venturini, V. Palermo, O. Pandoli, S. Pieraccini, P. Samorì, G. P. Spada, Chem. Eur. J., 2007, 13, 3757. [5] A. Ciesielski, R. Perone, S. Pieraccini, G.P. Spada, P. Samorì, Chem. Commun 2010, 46, 4493. [6] A. Ciesielski, S. Lena, S. Masiero, G. P. Spada, P. Samorì, Angew. Chem. Int. Ed. 2010, 49, 1963. [7] D. Bléger, A. Ciesielski, P. Samorì, S. Hecht, 2010 submitted.
Guanosines and Quadruplexes
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A. Ciesielki; S. Lena; S. Masiero; D. Bléger; S. Hecht; G. P. Spada; P. Samorì
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11585/97342
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