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Proceedings of the 31 st European Peptide SymposiumMichal Lebl, Morten Meldal, Knud J. Jensen, Thomas Hoeg-Jensen (Editors)European Peptide Society, 2010Bis-Azobenzene Photoswitchable α-Amino Acids forNanomaterials ApplicationsAlessandro Moretto 1 , Marco Crisma 1 , Paola Fatás 2 , Gema Ballano 2 ,Ana I. Jimenéz 2 , Carlos Cativiela 2 , and Claudio Toniolo 11 ICB, Padova Unit, CNR, Department of Chemistry, University of Padova, Padova, 35131,Italy; 2 Department of Organic Chemestry, ICMA, University of Zaragoza-CSIC,Zaragoza, 50009, SpainIntroductionThe photoisomerization of an azobenzene moiety between the extended (trans) andcompact (cis) conformations (Figure 1) is reversibly triggered by light at two differentwavelengths [1-3]. The resulting modifications in the molecular 3D-structures have beenextensively exploited to photoswitch transformation in chemical species reversibly forvarious types of applications, e.g. in the construction of optoelectronic devices [4].N NNN NNN NHONHHONH 22 OOtranscisFig. 1. The trans and cis forms of the C α -tetrasubstituted α-amino acid pAzoDbgsynthesized and studied in this work.Results and DiscussionHere, we describe synthesis and chemical characterization of the two achiral,C α -tetrasubstituted, α-amino acids, each characterized by two azobenzene moietiescovalently linked to their α-carbon atom, bis[4-(phenylazo)benzyl]Gly (pAzoDbg) and its3-(phenylazo)benzyl (mAzoDbg) analogue. These “albatros-like” compounds werecharacterized by UV-Vis spectroscopy and, one of them, by X-ray diffraction as well.We found that both compounds undergo multiple, reversible isomerizations in avariety of solvents by irradiation with Vis light (to trans) or UV light (to cis) (Figure 2).However, when the α-amino acids are dispersed in a paraffin medium, their photoswitchFig. 2. Mechanism of light-driven, trans/cis isomerization via the intermediate (X)-HpAzoDbg-L-Leu-OMe(cis-trans)/(Y)-H-pAzoDbg-L-Leu-OMe (trans-cis) diastereomers.12