Bimodal fluorescence signaling based on control of the excited-state conformational twisting and the ground-state protonation processes
摘要:
Amino-based fluoroionophores 1 and 2 can selectively sense alkaline earth metal ions in MeCN under both neutral and acidic conditions by different signaling mechanisms. The fluoroionophoric behavior for the neutral probes is characterized by an 'off-on' photoinduced electron transfer (PET)-like fluorescence intensity response due to a switching from a twisted internal charge transfer (TICT) to a planar internal charge transfer (PICT) state. For the protonated probes (i.e., 1/H+ and 2/H+), the fluorescing species is the localized stilbene fluorophores, but dual fluorescence is induced upon metal-ion recognition through a deprotonation process. (c) 2007 Elsevier Ltd. All rights reserved.
Photophysical Properties of Silyl‐Substituted Stilbene Derivatives
作者:Hajime Maeda、Ryo Horikoshi、Minoru Yamaji、Taniyuki Furuyama、Masahito Segi
DOI:10.1002/ejoc.202000397
日期:2020.6.23
Absorption and fluorescenceproperties of silyl‐substituted stilbenes were investigated. The derivative in which four Me3Si groups were introduced at the ortho positions did not fluoresce at room temperature. The para bis‐Me3SiC≡C‐substituted analog has a high fluorescence quantum yield (0.95). The stilbene containing Ph2N and Me3SiC≡C groups exhibited solvatofluorochromism while maintaining a good
Palladium-Catalysed Desulfitative Heck Reaction Tolerant to Aryl Carbon–Halogen Bonds for Access to (Poly)halo-Substituted Stilbene or Cinnamate Derivatives
(poly)halo-substituted benzenesulfonylchlorides with alkenes was investigated. Styrene or acrylates in the presence of bromo- or iodobenzenesulfonyl chlorides and a phosphine-free palladium catalyst were found to afford the expected β-arylated Heck type products with complete regio- and stereoselectivities. The reaction tolerates a variety of substituents on the halobenzenesulfonyl chloride. Moreover, no cleavage
Unsymmetrical <i>E</i>-Alkenes from the Stereoselective Reductive Coupling of Two Aldehydes
作者:Keyhan Esfandiarfard、Juri Mai、Sascha Ott
DOI:10.1021/jacs.7b00428
日期:2017.3.1
The unprecedented formation of unsymmetrical alkenes from the intermolecular reductive coupling of two different aldehydes is described. In contrast to the McMurry reaction which affords statistical product mixtures, selectivity in the reported procedure is achieved by a sequential ionic mechanism in which a first aldehyde is reacted with a phosphanylphosphonate to afford a phosphaalkene intermediate
Spectroscopic Correlations between Supermolecules and Molecules. Anatomy of the Ion-Modulated Electronic Properties of the Nitrogen Donor in Monoazacrown-Derived Intrinsic Fluoroionophores
The synthesis, absorption and emission spectra, fluorescence quantum yields, and fluorescence lifetimes of three compound series of trans-4,4'-disubstituted aminostilbenes (1-3) are reported. The chromo-/fluoroionophoric behavior of the monoaza-15-crown-5- (A15C5) and monoaza-18-crown-6 (A18C6)-derived species (1A(5)-3A(5) and 1A(6)-3A(6)) in acetonitrile and dichloromethane are also investigated. Great similarities in electronic spectroscopic properties (chemical shifts, wavelength, intensity, and lifetime) between the metal ion-complexed supermolecules and the corresponding chloro-substituted molecules have been observed: namely, 1A(5)/Ca2+-3A(5)/Ca2+ similar to 1A(6)/Ba2+-3A(6)/ Ba(2+)similar to 1C-3C in acetonitrile and 1A(5)/Na+-2A(5)/Na+ similar to 1A(6)/K+-2A(6)/K+ similar to 1C-2C in dichloromethane. Such spectroscopic correlations allow us to define the metal ion-modulated electronic character of the azacrown nitrogen atom in the ground and excited states and, in turn, to gain insights into the observed fluoroionophoric behavior of these probes in terms of the size and direction of fluorescence shifts and intensity variations.
Design of π-Conjugated Organic Materials for One-Dimensional Energy Transport in Nanochannels
Various end-substituted distyrylbenzenes have been synthesized to serve as guest molecules in inclusion compounds to promote efficient energy transport along one-dimensional channels. Their optical and photophysical properties have been characterized at both experimental and theoretical levels. All molecules display a large transition dipole moment between the ground state and lowest excited state and hence a short radiative lifetime (on the order of 1-2 ns). They also exhibit a large spectral overlap between the emission and absorption spectra, which enables efficient energy transport between molecules arranged in a head-to-tail configuration in nanochannels. Hopping rates on the order of 10(12) s(-1) are calculated at a full quantum-chemical level; this is much larger than the radiative lifetimes and opens the way for energy migration over large distances. Changes in the nature of the terminal substituents are found to modulate the optical properties weakly but to impact significantly the energy transfer rates.