Artificial tongues and leaves

Abstract

Abstract:The objective with synthetic multifunctional nanoarchitecture is to create large suprastructures with interesting functions. For this purpose, lipid bilayer membranes or conducting surfaces have been used as platforms and rigid-rod molecules as shape-persistent scaffolds. Examples for functions obtained by this approach include pores that can act as multicomponent sensors in complex matrices or rigid-rod π-stack architecture for artificial photosynthesis and photovoltaics.Keywords: nanoarchitecture; sensors; photovoltaics; photosynthesis; lipid bilayer; scaffolds.The objective with synthetic multifunctional nanoarchitecture is to create large suprastructures with interesting functions [1,2]. To address this challenge, we often begin with lipid bilayer membranes or, more recently, conducting surfaces as platforms. To direct, control, and stabilize advanced functional architecture, rigid-rod molecules [3][4][5][6][7][8][9][10] have been introduced as shape-persistent scaffolds. Somehow the antithesis to foldamers [11,12], these simple sturdy rods are attractive scaffolds, bypassing all folding problems because they do not fold. Unknown in biology, rigid-rod molecules are much appreciated in the materials sciences [3]. Prominent members of this family of oligomeric molecules include oligoacetylene 1, p-oligophenyls 2 [4,5] and their formal mixture, i.e., p-oligophenyleneethynylene (OPE) rods 3 [6,7] (Fig. 1). Whereas the benzene rings in p-oligophenyls 2 and OPEs 3 can rotate more or less freely, oligonaphthalenes 4 cannot. This produces an exceptionally complex axial stereochemistry [8]. Rigid oligonaphthalenediimide (O-NDI) rods 5 [9] and oligoperylenediimides (O-PDI) rods 6 [10] are of interest because they are colorizable, π-acidic n-semiconductors. Oligoporphyrins are extensively studied because of their optoelectric properties, the nonplanar rod 7 has been elongated up to l = 1060 Å of the monodisperse 128-mer [11].From this rich collection of rigid-rod molecules, we originally selected p-oligophenyls 2 as model rods [1,2,14]. p-Oligophenyls are not only straightforward to synthesize and derivatize but also nonplanar and fluorescent, and can exhibit a dynamic axial chirality. The torsion angles between neighboring phenyls of the p-oligophenyl scaffold provide the directionality that is needed to control advanced supramolecular architecture. Dynamic chirality and fluorescence are of use for structural studies in