The spectroscopic properties of two asymmetric indolylmaleimide derivatives, 4-bromo-3-(1′H-indol-3′-yl)-maleimide and 4-memyl-3-(1′H-indol-3′-yl)maleimide, are investigated. The bromo derivative was crystallized and its X-ray structure was determined. Both compounds are strongly colored while their separate components (indole and maleimide) absorb in the UV region only. To understand the ground- and excited-state behavior, the photophysical properties of the two compounds were studied in detail by steady state and time-resolved absorption and emission spectroscopy. Their solvatochromic behavior was investigated by using the Kamlet-Taft approach, which indicates some charge transfer (CT) character in the excited state. Nano- and femtosecond transient absorption spectroscopy was used for the identification and investigation of the CT state. Furthermore, the effect of the complexation with zinc(II) 1,4,7,11-tetraazacyclododecane (Zn-cyclen) on the photophysical properties of these two compounds was studied. An enhancement of the fluorescence intensity upon self-assembly (up to 90 times) and high association constants were observed, which illustrate the potential use of these compounds as luminescent sensors. DFT calculations indicate that HOMO-1 to LUMO excitation is mainly responsible for the charge transfer character and that this transition changes its character drastically when Zn-cyclen complexation occurs, thus giving it sensor properties.
Asymmetric indolylmaleimide derivatives and their complexation with zinc(II)-cyclen / B.K. Kaletas, H.C. Joshi, G.D. Van Zwan, M. Fanti, F. Zerbetto, K. Goubitz, L. De Cola, B. Konig, R.M. Williams. - In: JOURNAL OF PHYSICAL CHEMISTRY. A, MOLECULES, SPECTROSCOPY, KINETICS, ENVIRONMENT, & GENERAL THEORY. - ISSN 1089-5639. - 109:42(2005), pp. 9443-9455.
|Titolo:||Asymmetric indolylmaleimide derivatives and their complexation with zinc(II)-cyclen|
|Parole Chiave:||solvatochromic comparison method; chelation-enhanced fluorescence; macrocyclic tetraamine complex; photoinduced electron-transfer; solvation energy relationships; alkali-metal ion; isoelectronic molecules; scattering factors; alcohol-pedant; PI-star|
|Settore Scientifico Disciplinare:||Settore CHIM/03 - Chimica Generale e Inorganica|
|Data di pubblicazione:||2005|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1021/jp054651z|
|Appare nelle tipologie:||01 - Articolo su periodico|