Arcyriarubin A and arcyriaflavin A, two strongly emissive and intensely colored natural products containing both two indoles and a maleimide unit, are investigated (in the flavin the two indole moieties are coupled by a cyclization). The photophysical properties of these compounds were studied in several solvents using UV-vis absorption, steady-state and time-resolved emission, nano- and femtosecond transient absorption spectroscopy. Furthermore, the effect of complexation with zinc(II) 1,4,7,11-tetraazacyclododecane on the photophysical properties of these natural products has been investigated. The chemical structures of the compounds would suggest a charge transfer (CT) character in the ground and/or excited states, since indole is a well-known electron donor and maleimide is a good electron acceptor. Their solvatochromic behavior was investigated by using the Kamlet-Taft approach and indicates only a small CT character in the excited state. This is substantiated by the time-resolved spectroscopy and the complexation study. Molecular orbital calculations indicate that there are no electronic transitions in which a large electron density is transferred from one indole unit to the maleimide part. All calculated orbitals show a strong delocalization of the electron density over the whole molecule. These findings corroborate the experimental results. Whereas the two compounds do have a substantial (calculated) ground-state dipole moment (6 D) and show some solvatochromic behavior, they behave more like conjugated aromatic systems than like electron donor-acceptor systems.
Unexpected photophysical properties of symmetric indolylmaleimide derivatives / B.K. Kaletas, C. Mandl, G. Van Der Zwan, M. Fanti, F. Zerbetto, L. De Cola, B. Konig, R.M. Williams. - In: JOURNAL OF PHYSICAL CHEMISTRY. A, MOLECULES, SPECTROSCOPY, KINETICS, ENVIRONMENT, & GENERAL THEORY. - ISSN 1089-5639. - 109:29(2005), pp. 6440-6449.
|Titolo:||Unexpected photophysical properties of symmetric indolylmaleimide derivatives|
|Parole Chiave:||protein-kinase-C; solvation energy relationships; PI-star; bisindolylmaleimides; recognition; inhibitors|
|Settore Scientifico Disciplinare:||Settore CHIM/03 - Chimica Generale e Inorganica|
|Data di pubblicazione:||2005|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1021/jp051035u|
|Appare nelle tipologie:||01 - Articolo su periodico|