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Article

In Search of Excited-State Proton Transfer in the Lumichrome Dimer in the Solid State: Theoretical and Experimental Approach

Supporting Info

Ewa Sikorska,^† Igor Khmelinskii,^‡ Maciej Kubicki,^§ Wiesław Prukała,^§ Marcin Hoffmann,^§ Isabel F. Machado,^# Luis F. V. Ferreira,^# Jerzy Karolczak,^£ David R. Worrall,^¶ Alina Krawczyk,^§ Małgorzata Insińska-Rak,^§ and Marek Sikorski*^§

Faculty of Commodity Science, Pozna University of Economics, al. Niepodlegloci 10, 60-967 Pozna, Poland, Universidade do Algarve, DQB, FCT, Campus de Gambelas, Faro 8005-139, Portugal, Faculty of Chemistry, A. Mickiewicz University, Grunwaldzka 6, 60-780 Pozna, Poland, BioInfoBank Institute, Limanowskiego 24A, 60-744 Pozna, Poland, Centro de Qumica-Fsica Molecular, Complexo Interdisciplinar, Instituto Superior Tcnico, 1049-001 Lisbon, Portugal, Faculty of Physics, A. Mickiewicz University, Umultowska 85, 61-614 Pozna, Poland, Center for Ultrafast Laser Spectroscopy, A. Mickiewicz University, Umultowska 85, 61-614 Pozna, Poland, and Department of Chemistry, Loughborough University, Loughborough, Leicestershire LE11 3TU, U.K.

J. Phys. Chem. A, 2006, 110 (14), pp 4638–4648

DOI: 10.1021/jp060072y

Publication Date (Web): March 22, 2006

†

Poznań University of Economics.

‡

Universidade do Algarve.

Faculty of Chemistry, A. Mickiewicz University.

BioInfoBank Institute.

Instituto Superior Técnico.

Faculty of Physics, A. Mickiewicz University.

Center for Ultrafast Laser Spectroscopy, A. Mickiewicz University.

Loughborough University.

Corresponding author. Phone: +48 61 8291309. Fax: +48 61 8658008. E-Mail: sikorski@amu.edu.pl.

Abstract

Quantum chemical density functional theory (DFT) calculations and spectral data were employed to investigate the possibility of the excited-state double proton transfer (ESDPT) in lumichrome crystals. The calculations in a lumichrome dimer predict a transfer of a proton in the first excited state, leading to a cation−anion pair. The presently reported X-ray structure of 1,3-dimethyllumichrome and its complex solid-state luminescence indicate that also in this molecule intermolecular hydrogen bonds might be involved in the photophysics. The long-wavelength emission in lumichrome crystals peaked at 530 nm is attributed to excited-state proton transfer, whereas a wider emission band in methylated lumichrome derivatives peaked at 560 nm is attributed to ions formed upon photoexcitation of the crystals.

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