Phosphorescent photoinduced electron

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... 

Photoinduced electron transfer from eosin and ethyl eosin to Fe(CN)g in AOT/heptane-RMs was studied and the Hfe time of the redox products in reverse micellar system was found to increase by about 300-fold compared to conventional photosystem [335]. The authors have presented a kinetic model for overall photochemical process. Kang et al. [336] reported photoinduced electron transfer from (alkoxyphenyl) triphenylporphyrines to water pool in RMs. Sarkar et al. [337] demonstrated the intramolecular excited state proton transfer and dual luminescence behavior of 3-hydroxyflavone in RMs. In combination with chemiluminescence, RMs were employed to determine gold in aqueous solutions of industrial samples containing silver alloy [338, 339]. Xie et al. [340] studied the a-naphthyl acetic acid sensitized room temperature phosphorescence of biacetyl in AOT-RMs. The intensity of phosphorescence was observed to be about 13 times higher than that seen in aqueous SDS micelles. 

De Silva et al. [28] prepared a naphthalene derivative (3) with logic functions (Scheme 1). Here, the bromonaphthalene unit exhibits phosphorescence in the presence of both the calcium ion and (3-CD [28], However, without them, oxygen quenches the phosphorescence of 2-bromonaphthalene phosphor because the protection effect of (3-CD is absent and photoinduced electron transfer from the tetracarboxylate receptor to the 2-bromonaphthalene phosphor occurs. Thus, phosphorescence output occurs only when the calcium ion and (3-CD inputs are active. The operation of these two inputs with a phosphorescence output corresponds to the AND logic function. The input to the NOT gate is oxygen. In the presence of oxygen without either calcium or (3-CD, the AND gate is disabled. 

Cyclodextrins have been used for enhancing the phosphorescence of guests by encapsulation [12]. de Silva et al. employed cyclodextrins as transparent shields to protect the phosphor molecule sterically from contact with its environment (especially O2) while allowing access to photons. Sensing remains viable because the proton receptor module is not enveloped (Figure 9) [13]. The authors used this system as a phosphorescent PET (photoinduced electron transfer) chemosensor for... 

The principle of photoinduced electron transfer is combined with the modular system Fluorophore-Spacer-Receptor to develop the phenomenon of cation-responsive fluorescence. pH controlled on-off fluorescence is demonstrated in the case of the dialkylaminoalkyl heterocyclic derivative la. The modular system is then extended in two directions. In the first of these, targetting/anchoring modules are added to allow the investigation of proton fields in microheterogeneous membrane media with high spatial resolution. The sensor family 2a-f is the realization of this approach. The second direction employs phosphorescent (instead of fluorescent) modules with/without protective shields to permit the development of phosphorescent pH sensing in an interference-free manner within... 

On the basis of the overall results, an energy diagram for CT-allowing AN-s-BPDA-AN can be depicted as shown in Fig. 19. In the proposed mechanism, the intermolecular CT fluorescence emission occurs via two different pathways first, the photoinduced electron transfer from a local excited state at the biphenyldiimide unit to the spatially adjacent ground-state PDA residue, and second, the direct excitation at the CT absorption band. The first process is possible even at very low CTC concentration as in the PI film cured at a low temperature such as 200°C. Such a photoinduced electron transfer mechanism will be theoretically discussed again later. In fully aromatic s-BPDA-PDA, both the fluorescence from Si (tt, tt ) and phosphorescence from Ti (tt, tt ) are not observed practically. The results are probably attributed to the considerably fast CT process from Si (it, tt ). 

The electronic structure of Ni(CO)4 is not as well defined as those of either Cr(CO)6 or Fe(CO)5. This makes the assignment of processes in the early development of the excited-state dynamics somewhat speculative. However there are a number of unique features to the photophysics of CO-loss from Ni(CO)4. Firstly, the CO loss is very slow compared to the other two systems outlined herein taking approximately 600 fs. In addition the Ni(CO)3 fragment is produced in its St state and this state persists because there is no facile deactivation process available based on molecular motions. Deactivation can be achieved only by further CO loss or by radiative processes of either fluorescence or phosphorescence. The overall scheme of potential energy curves and pathways for photoinduced loss of CO from Ni(CO)4 is represented in Fig. 29. 

It has been shown recently by Kapturkiewicz and co-workers [14] that the analysis of the CT absorption CT <— So and the radiative and radiationless charge recombination processes CT So (Figure 4) in selected D-A n-n interacting systems sterically hindered to coplanarity (such as 9-anthryl and 9-acridyl derivatives of aromatic amines [14a,b], carbazol-9-yl derivatives of aromatic nitriles [14c] and ketones [14d] and D-A derivatives of indoles [14e] or phenoxazines and phe-nothiazines [14f]) in terms of the theory of photoinduced ET processes in absorption [52, 53] and emission [53-55] and Mulliken and Murrell models of molecular CT complexes [56, 57] leads to the determination of the quantities relevant for the rate of the radiative ET processes (exemplified by the CT absorption and emission) and to the estimation of the electronic structure and molecular conformation of the states involved in the photoinduced ET. A similar approach can be applied to describe the properties of the fluorescent singlet CT states and phosphorescent triplet CT states [58]. It should be pointed out that the relatively large values of the electronic transition dipole moments of the CT fluorescence indicate a non-... 

Quantitative photophysical, photochemical and photopolymerisation data are presented on five novel water soluble benzophenone photoinitiators. Phosphorescence quantum yields, triplet lifetimes and transient formation on conventional flash photolysis correlate with the ability of the initiators to photoinduce the polymerisation of 2-hydroxyethylmethacrylate and a commercial monoacrylate resin in aqueous media. The results indicate that the lowest excited triplet state of the initiator is abstracting an electron from the tertiary amine cosynergist probably via a triplet exciplex followed by hydrogen atom abstraction. This is confirmed by a detailed analysis on the effect of oxygen, pH and the ionisation potential of the amine on transient formation and photopolymerisation. Using photocalorimetry a linear correlation is found between the photopolymerisation quantum yields of the initiators and their photoreduction quantum yields in aqueous media. 

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