Photo-induced ionic-to-neutral phase transition in tetrathiafulvalen-p-chloranil crystals

Recent experimental results are reviewed of the transformation between ionic and neutral phases in tetrathiafulvalen-p-chloranil crystals, induced by exciting the electronic states of the crystal. Spectroscopic studies have revealed that N phase domains are formed in the ionic-host crystal only above threshold-excitation intensity in the case of charge-transfer excitation; the threshold intensity depends strongly on the wavelength. On the other hand, N-phase domains can be formed without threshold in the excitation intensity in the case of intra-molecular excitation. Also, femtosecond time-resolved study has shown the intensity-dependent dynamics of the N-phase domain formation, and revealed the presence of short-lived intermediate states prior forming the N-phase domain. The mechanism of the photo-induced phase transition in this crystal is discussed based on these results.     

Determination of the structural features of a long-lived electron-transfer state of 9-mesityl-10-methylacridinium ion

Extensive efforts have been devoted to developing electron donor-acceptor systems that mimic the utilization of solar energy that occurs in photosynthesis. X-ray crystallographic analysis shows how absorbed photon energy is stabilized in those compounds by structural changes upon photoinduced electron transfer (ET). In this study, structural changes of a simple electron donor-acceptor dyad, 9-mesityl-10-methylacridinium cation (Acr(+)-Mes), upon photoinduced ET were directly observed by laser pump and X-ray probe crystallographic analysis. The N-methyl group in Acr(+) was bent, and a weak electrostatic interaction between Mes and a counteranion in the crystal (ClO(4)) was generated by photoinduced ET. These structural changes correspond to reduction and oxidation due to photoinduced ET and directly elucidate the mechanism in Acr(+)-Mes for mimicking photosynthesis efficiently.     

A strong convergence theorem for relatively nonexpansive mappings in a Banach space

In this paper, we prove a strong convergence theorem for relatively nonexpansive mappings in a Banach space by using the hybrid method in mathematical programming. Using this result, we also discuss the problem of strong convergence concerning nonexpansive mappings in a Hilbert space and maximal monotone operators in a Banach space.     

Electrooxidation of vanillyl alcohol in acidic aqueous solution using rotating ring-disk electrode voltammetry.

The electrooxidation of benzylic alcohol derivative in acidic aqueous solution shows an oxidation pre-peak in the cyclic voltammogram, which means that the reaction is proceeding via an ECE mechanism where the second electron transfer occurs at a less positive potential. From the result of the rotating ring-disk electrode voltammetry, the initial oxidation response of the electrode reaction can be extracted.     

Strategy for preparation of hybrid polymer hydrogels using silica nanoparticles as multifunctional crosslinking points

Novel hybrid polymer hydrogels were prepared in a facile manner by simple mixing of a water-soluble copolymer having trimethoxysilyl side chains with silica nanoparticles used as multiple crosslinkers.     

Strong convergence theorems obtained by a generalized projections hybrid method for families of mappings in Banach spaces

Let C be a nonempty, closed and convex subset of a uniformly convex and smooth Banach space and let {T_n} be a family of mappings of C into itself such that the set of all common fixed points of {T_n} is nonempty. We consider a sequence {x_n} generated by the hybrid method by generalized projection in mathematical programming. We give conditions on {T_n} under which {x_n} converges strongly to a common fixed point of {T_n} and generalize the results given in [12], [14], [13] and [11].     

Photoinduced flavin-tryptophan electron transfer across vesicle membranes generates magnetic field sensitive radical pairs

ABSTRACT

Due to the photobiology of the flavoproteins DNA photolyase and cryptochrome, electron transfer reactions between flavins and tryptophan are of significant biological relevance. In addition, electron transfer across vesicle membranes has also seen much attention. In this work, we study the electron transfer reaction between flavins and tryptophan across lipid bilayer membranes in 1,2-dipalmitoyl-sn-glycero-3-phosphocholine small unilamellar vesicles using time-resolved optical absorption microspectroscopy and magnetically affected reaction yield spectroscopy. We demonstrate that riboflavin tetrabutyrate is embedded in the vesicle bilayer and can undergo electron transfer with tryptophan molecules in either the inner water pool or the bulk solution. Remarkably, flavin mononucleotide encapsulated in the inner water pool can undergo electron transfer across the vesicle bilayer to generate a magnetically sensitive radical pair with tryptophan molecules located in the bulk solution. The observed kinetics suggest that back electron transfer occurs between radical pairs generated by diffusive reencounter, either in the vesicle surface water or via electron hopping through degenerate electron exchange.     

Anomalous phase diagram of ferroelectric (Ba,Ca)TiO3 single crystals with giant electromechanical response

We report the anomalous phase evolution in ferroelectric single crystals Ba1-xCaxTiO3 (0.02相似文献   

Dynamical aspects of the photoinduced phase transition in spin-crossover complexes

We report a dynamical study on the photoinduced cooperative changes of the spin configurations in single crystals of the organometal spin-crossover complex. In the photoswitching process between low- and high-spin states, nonlinear characteristics such as thresholdlike behavior, incubation period, and phase separation have been observed. These results demonstrate that the cooperative intersystem crossing mediated by spin-lattice interaction plays a key role in the driving process of a new class of nonequilibrium phenomena so called photoinduced phase transition.     

Phosphorescent iridium complexes based on 2-phenylimidazo[1,2-a]pyridine ligands: tuning of emission color toward the blue region and application to polymer light-emitting devices

A series of new blue-phosphorescent iridium(III) complexes 1-14 with ligands of 2-phenylimidazo[1,2-a]pyridine (pip) derivatives were successfully prepared, and their electrochemical, photophysical, and electroluminescent (EL) properties were systematically investigated. It was found that the emission maxima are significantly dependent on the substituents on the phenyl ring in the range of 489-550 nm. For instance, electron-withdrawing groups such as F and CF3 shift the emission maxima to shorter wavelengths by lowering the HOMO levels (complexes 4-8), whereas the extended pi-conjugation leads to bathochromic shifts (2, 3). To obtain further information about the frontier orbital, substitution effects on the imidazole part were also investigated here, and it was found that electron-withdrawing or -donating substituents on the imidazole ring affected the emission maxima (9, 557 nm; 10, 525 nm). These results including their oxidation potentials suggest that the HOMO of the pip-based complex is a mixture of Ir-d, phenyl-pi, and imidazole-pi orbitals. From this viewpoint, combination of electron-withdrawing substituents on the phenyl ring with the use of another ancillary ligand enabled further blue shifts (13, 468, 499 nm; 14, 464, 494 nm). This new system based on pip is one of the rare examples of iridium complexes whose emissions can be tuned to the blue region. Preliminary polymer light-emitting devices (PLEDs) employing the Ir complexes were fabricated, and the devices showed moderate EL efficiencies.