Asymmetric indolylmaleimide derivatives and their complexation with zinc(II)-cyclen.
The spectroscopic properties of two asymmetric indolylmaleimide derivatives, 4-bromo-3-(1'H-indol-3'-yl)maleimide and 4-methyl-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.
Kaletas
Basak Kükrer
BK
Molecular Photonic Materials, van't Hoff Institute for Molecular Sciences, Universiteit van Amsterdam, Nieuwe Achtergracht 166, 1018 WS Amsterdam, The Netherlands.
Joshi
Hem C
HC
van der Zwan
Gert
G
Fanti
Marianna
M
Zerbetto
Francesco
F
Goubitz
Kees
K
De Cola
Luisa
L
König
Burkhard
B
Williams
René M
RM
D003198:Computer Simulation; D018360:Crystallography, X-Ray; D000080027:Cyclams; D006571:Heterocyclic Compounds / Q000737:chemistry*; D007211:Indoles / Q000737:chemistry*; D008301:Maleimides / Q000737:chemistry*; D008956:Models, Chemical; D008958:Models, Molecular; D015394:Molecular Structure; D009942:Organometallic Compounds / Q000138:chemical synthesis / Q000737:chemistry*; D011789:Quantum Theory; D012680:Sensitivity and Specificity; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013997:Time Factors; D015032:Zinc / Q000737:chemistry*
C521320:4-bromo-3-(1'H-indol-3'-yl)maleimide; C521319:4-methyl-3-(1'H-indol-3'-yl)maleimide; D000080027:Cyclams; D006571:Heterocyclic Compounds; D007211:Indoles; D008301:Maleimides; D009942:Organometallic Compounds; C038072:cyclen; D015032:Zinc