Photoinduced electron transfer fluorescence

M -Dialkyldiazacrown ethers and their precursors fcis(alkylamino) derivatives of tri- and tetraethylene glycols were prepared <96CCCC622>. New hydroxy-bearing dibenzo-azocrown ethers have been conveniently prepared utilizing l,3-Ws(2-formylphenoxy)-2-propanol and a diamine, followed by reduction of the intermediate diimine <96P1197>. Fluorescent photoinduced electron transfer sensor 5 with monoaza-18-crown-6 and guanidinium receptor units demonstrated a fluorescence with T -aminobutyric acid in a mixed... 

In two other studies, it was observed that C60 in LB films can quench the fluorescence of pyrene [293] and of 16-(9-anthroyloxy)palmitic acid [294] by photoinduced electron transfer. In these studies, both C60 and the electron-donating fluorophore were incorporated into a tricosanoic acid LB film in different ratios. 

James TD (2007) Saccharide-Selective Boronic Acid Based Photoinduced Electron Transfer (PET) Fluorescent Sensors. 277 107-152... 

Miura T, Urano Y, Tanaka K, Nagano T, Ohkubo K, Fukuzumi S (2003) Rational design principle for modulating fluorescence properties of fluorescein-based probes by photoinduced electron transfer. J Am Chem Soc 125 8666-8671... 

The second group of intermolecular reactions (2) includes [1, 2, 9, 10, 13, 14] electron transfer, exciplex and excimer formations, and proton transfer processes (Table 1). Photoinduced electron transfer (PET) is often responsible for fluorescence quenching. PET is involved in many photochemical reactions and plays... 

Keywords Excited-state intramolecular proton transfer Fluorescence dye Photoinduced electron transfer Proton coupled electron transfer Relaxation dynamics... 

Callis PR, Liu T (2006) Short range photoinduced electron transfer in proteins QM-MM simulations of tryptophan and flavin fluorescence quenching in proteins. Chem Phys 326 (l) 230-239... 

The scientists from Hong Kong reported83 on a sol-gel derived molecular imprinted polymers (MIPs) based luminescent sensing material that made use of a photoinduced electron transfer (PET) mechanism for a sensing of a non-fluorescent herbicide - 2,4-dichlorophenoxyacetic acid. A new organosilane, 3 - [N,V-bis(9-anthrylmethyl)amino]propyltriethoxysilane, was synthesized and use as the PET sensor monomer. The sensing MIPs material was fabricated by a conventional sol-gel process. 

Keywords Luminescence m Fluorescence m Phosphorescence a Sensors a Switches a Logic Gates a Supramolecular Systems a Truth Tables a Photoinduced Electron Transfer a Molecular-Level Devices... 

Parkesh R, Lee TC, Gunnlaugsson T (2007) Highly selective 4-amino-1,8-naphthalimide based fluorescent photoinduced electron transfer (PET) chemosensors for Zn(II) under physiological pH conditions. Org Biomol Chem 5 310-317... 

Fan L-J, Jones WE Jr (2006) Studies of photoinduced electron transfer and energy migration in a conjugated polymer system for fluorescence tum-on chemosensor applications. J Phys Chem B 110 7777-7782... 

Photoinduced electron transfer (PET) is often responsible for fluorescence quenching. This process is involved in many organic photochemical reactions. It plays a major role in photosynthesis and in artificial systems for the conversion of solar energy based on photoinduced charge separation. Fluorescence quenching experiments provide a useful insight into the electron transfer processes occurring in these systems. 

Class C Fluorophores that undergo no photoinduced proton transfer but only photoinduced electron transfer. The fluorescence quantum yield of these fluorophores is very low when they are in the non-protonated form because of internal quenching by electron transfer. Protonation (which suppresses electron transfer) induces a very large enhancement of fluorescence (see Section 10.2.2.5). The bandshapes of the excitation and fluorescence spectra are independent of pH. 

Most PET fluorescent sensors for cations are based on the principle displayed in Figure 10.7, but other photoinduced electron transfer mechanisms can take place with transition metal ions (Fabbrizzi et al., 1996 Bergonzi et al., 1998). In fact, 3d metals exhibit redox activity and electron transfer can occur from the fluorophore... 

Appropriate combinations of boronic acid and fluorophores lead to a remarkable class of fluorescent sensors of saccharides (Shinkai et ah, 1997, 2000, 2001). The concept of PET (photoinduced electron transfer) sensors (see Section 10.2.2.5 and Figure 10.7) has been introduced successfully as follows a boronic acid moiety is combined intramolecularly with an aminomethylfluorophore consequently, PET from the amine to the fluorophore causes fluorescence quenching of the latter. In the presence of a bound saccharide, the interaction between boronic acid and amine is intensified, which inhibits the PET process (Figure 10.42). S-l is an outstanding example of a selective sensor for glucose based on this concept (see Box 10.4). 

Time-resolved fluorescence studies were also carried out on a series of zinc(II) complexes of meso-tetraphenylporphyrins covalently linked to 1,3-dinitrobenzene and 1,3,5-trinitrobenzene as acceptors to study the photoinduced electron transfer process, which is the initial process for the photosynthesis10. 

This type of probe, often called fluorescent photoinduced electron transfer (PET) sensors, has been extensively studied (for reviews, see Refs. 22 and 23). Figure 2.2 illustrates how a cation can control the photoinduced charge transfer in a fluoroiono-phore in which the cation receptor is an electron donor (e.g., amino group) and the fluorophore (e.g., anthracene) plays the role of an acceptor. On excitation of the fluorophore, an electron of the highest occupied molecular orbital (HOMO) is promoted to the lowest unoccupied molecular orbital (LUMO), which enables photoinduced electron transfer from the HOMO of the donor (belonging to the free cation receptor) to that of the fluorophore, causing fluorescence quenching of the latter. On... 

A. Prasanna de Silva, and H. Q. Nimal Gunaratne, Fluorescent PET (Photoinduced Electron Transfer) sensors selectives for submicromolar calcium with quantitatively predictable spectral and ion-binding properties, J. Chem, Soc., Chem, Common. 186 (1990). 

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