Fluorescence excited state intramolecular proton transfer

Poly(aryl ether) branches of generation 1 to 3 have been appended to a pho-totautomerizable quinoHne core to investigate the effect of dendritic architecture on the excited state intramolecular proton transfer [45]. The changes observed in the absorption and emission spectra on increasing dendrimer generation indicate that the dendritic branches affect the planarity of the core and therefore the efficiency of the excited state intramolecular proton transfer and of the related fluorescence processes. 

Excited-state intramolecular proton transfer (ESIPT) exhibits different regularities [49, 50]. Commonly, this is a very fast and practically irreversible reaction proceeding along the H-bonds preexisting in the ground state. Therefore, only the reaction product band is seen in fluorescence spectra. Such cases are not interesting for designing the fluorescence reporters. The more attractive dual emission is... 

Klymchenko AS, Demchenko AP (2003) Multiparametric probing of intermolecular interactions with fluorescent dye exhibiting excited state intramolecular proton transfer. Phys Chem Chem Phys 5 461 -68... 

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

Jang DJ, Kelley DF (1985) Time-resolved and steady-state fluorescence studies of the excited-state intramolecular proton transfer and relaxation of 2-hydroxy-4, 5-naphthotro-pone. J Phys Chem 89 209-211... 

Sytnik A, Kasha M (1994) Excited-state intramolecular proton transfer as a fluorescence probe for protein binding-site static polarity. Proc Natl Acad Sci USA 91 8627-8630... 

Lim SJ, Seo J, Park SY (2006) Photochromic switching of excited-state intramolecular proton-transfer (ESIPT) fluorescence a unique route to high-contrast memory switching and nondestructive readout. J Am Chem Soc 128 14542-14547... 

Kim CH, Joo T (2010) Coherent excited state intramolecular proton transfer probed by time-resolved fluorescence. Phys Chem Chem Phys. doi 10.1039/b915768a... 

Chen KY, Cheng YM, Lai CH et al (2007) Ortho green fluorescence protein synthetic chromophore Excited-state intramolecular proton transfer via a seven-membered-ring hydrogen-bonding system. J Am Chem Soc 129 4534 -535... 

Shynkar VV, Mely Y, Duportail G et al (2003) Picosecond time-resolved fluorescence studies are consistent with reversible excited-state intramolecular proton transfer in 4 -(dialkylamino)-3-hydroxyflavones. J Phys Chem A 107 9522-9529... 

Seo J, Kim S, Park SY (2004) Strong solvatochromic fluorescence from the intramolecular charge-transfer state created by excited-state intramolecular proton transfer. J Am Chem Soc 126 11154-11155... 

Klymchenko AS, Demchenko AP (2002) Electrochromic modulation of excited-state intramolecular proton transfer the new principle in design of fluorescence sensors. J Am Chem Soc 124 12372-12379... 

Rate coefficients in the expected range have been observed in excited state intramolecular proton transfers involving 2-(2-hydroxyphenyl)benzothiazole (Barbara et al., 1980a) and salicylideneaniline (Barbara et al., 1980b). In the former, the observation of fluorescence was explained by Scheme 2 and the... 

If the molecule carries its own base, excited-state proton transfer can occur intramolecularly (ESIPT = excited-state intramolecular proton transfer(37)) and becomes more or less independent of the surrounding solvent. The ESIPT reaction is extremely fast (subpicosecond kinetics(38)) and occurs also in rigid glasses and at very low temperatures.06 39) Very often, only the ESIPTproduct P fluoresces, and this is the source of extremely large Stokes shifts which are fairly independent of medium... 

Different photochemical channels leading either to TICT or to other products can be combined in one and the same molecule. An example involving competition between Excited State Intramolecular Proton Transfer (ESIPT) and TICT formation (Scheme 2) is the molecule Kal [111]. In this case, three fluorescence bands can be expected in principle (the precursor state E and the two product species ESIPT and TICT). The product channels can be selectively blocked in the model compounds Ka2 and Ka3. 

Two papers deserve to be reported here. The absence of excited-state intramolecular proton-transfer (ESIPT) in 3-hydroxy-2-methyl-phenyl-4-pyridinone (129) was explained by the twist (48°) of the dihedral angle (AMI calculations) (94CPL(220)229). The tiimethyl derivative of N-(l-naphthyl)-pyridinium 130 shows temperature dependent multiple fluorescence. B3LYP/6-31G(d) calculations indicate that several minima on the SI-hypersurface are responsible for this behavior (01MI127). 

Where the substituent X on the polymer is an OH group with an intramolecular H bond, the polymer in solution shows dual blue and red fluorescent bands. The authors claim that a semiempirical molecular orbital calculation of this emission supports the phenomenon of excited-state intramolecular proton transfer. 

The development of picosecond laser techniques has led to a renewed interest in the spectroscopy and kinetics of aromatic molecules which may undergo excited state intramolecular proton transfer (ESIPT, fig. 1). The ESIPT reaction is evidenced by a large Stokes shift for fluorescence from the proton-transferred molecule. ... 

N. P. Ernsting, Dual fluorescence and excited-state intramolecular proton transfer in jet-cooled... 

Rodembusch FS, Campo LF, Stefani V, Rigacci A (2005) The first silica aerogel fluorescent by excited state intramolecular proton transfer mechanism (ESIPT). J Mater Chem 15 1537-1541... 

Ernesting NP, Dick B. (1989) Fluorescence excitation of isolated, jet-cooled 3-hydroxyflavone-the rate of excited-state intramolecular proton-transfer from homogenous linewidths. Chem. Phys. 136 (2) 181-186. Miihlpfordt A, Bultmann T, Ernesting NP. (1994) Excited-state intramolecular proton... 

Another fluorescent probe 26, based on 1-amidoanthraquinone and with calix[4] arene in the cone conformation, was developed (Fig. 28.6) [54]. Probe 26 exhibits very weak fluorescence because of the excited state intramolecular proton transfer (ESIPT) between the amide NH and the quinone oxygen. The addition of F significantly enhances the fluorescence emission due to inhibition of the ESIPT process. The F ions interact with the amide NH groups on the two arms, thereby inhibiting the ESIPT process and thus increasing the fluorescence emissirMi. 

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