Proline as a charge stabilizing amino acid in peptide radical cations

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Influence of proline in the stabilization of radical cations –

Supporting Information

Nicolas P.-A. Monney, Thomas Bally and Bernd Giese*.

University of Fribourg, Chemin du Musée 9, CH-1700 Fribourg, Switzerland *

Correspondence: Prof. Dr. B. Giese, e-mail: bernd.giese@unifr.ch Reference

[13] Gaussian 09, Revision C.01, M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria, M. A. Robb, J. R. Cheeseman, G. Scalmani, V. Barone, B. Mennucci, G. A. Petersson, H. Nakatsuji, M. Caricato, X. Li, H. P. Hratchian, A. F. Izmaylov, J. Bloino, G. Zheng, J. L. Sonnenberg, M. Hada, M. Ehara, K. Toyota, R. Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O. Kitao, H. Nakai, T. Vreven, J. A. Montgomery, Jr., J. E. Peralta, F. Ogliaro, M. Bearpark, J. J. Heyd, E. Brothers, K. N. Kudin, V. N. Staroverov, R. Kobayashi, J. Normand, K.

Raghavachari, A. Rendell, J. C. Burant, S. S. Iyengar, J. Tomasi, M. Cossi, N. Rega, J. M. Millam, M. Klene, J. E. Knox, J. B. Cross, V. Bakken, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann, O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski, R. L. Martin, K. Morokuma, V. G. Zakrzewski, G. A. Voth, P. Salvador, J. J. Dannenberg, S. Dapprich, A. D. Daniels, Ö. Farkas, J. B. Foresman, J. V. Ortiz, J. Cioslowski, and D. J. Fox, Gaussian, Inc., Wallingford CT, 2009.

Table S1: Different vertical ionization energies calculated with M06-2X/6-31G*. Species Vertical IE (eV) Difference (eV) Difference (kcal/mol) 2,4-dimethoxytoluene 7.73 1A 7.27 -0.46 -10.5 1C 7.36 -0.37 -8.5 2,4,6-trimethoxytoluene 7.48 1B 7.34 -0.14 -3.3 toluene 8.841) neutral 4A 8.34 -0.50 -11.6 neutral 4B 8.34 -0.50 -11.6 neutral 4C 8.40 -0.45 -10.3 N,N-dimethylacetamide 8.992) 5 8.46 -0.54 -12.3 1)

8.83 eV on NIST Webbook of chemistry 2)

9.11 eV from Fig. 7

Figure S1: Distances between the trimethoxybenzyl ring and both the interacting p-lone pair and the

dimethoxybenzyl ring in conformer 3B.

Published in -RXUQDORI3K\VLFDO2UJDQLF&KHPLVWU\± which should be cited to refer to this work.

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Figure S2: Geometry changes of the interacting groups on one electron oxidation of the conformers A, B and C.

The green structures are those of the neutral conformers.

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Figure S4: Superimposition of the two conformers of 5 that participate in the PE spectrum shown in Fig. 7.

Table S2: Lowest Ionization Energies (in eV) of N,N-Dimethylacetamide (DMA) and 5 as shown in Fig. 7.

Compound experimental calculated

DMA 9.1, 9.5 9.0, 9.2,