摘要:

Functionalized photochromic compounds and their applications in chemical and physical switching processes are under investigation. In this report exclusive consideration is given to the dihydroazulene @HA)/vinylheptafulvene (VHF) system½.A short description of the photochromism of½.is presented. Three topics of potential switching behaviour released by the photochromism of½.are pointed out: (i) change of the pkaand of proton transfer properties in anilinium derivatives, (ii) change of the redox potential in compounds with electron transfer active subunits, (iii) increase of second‐order nonlinear optical properties by irradiation of1.

ISSN:1058-725X    

DOI:10.1080/10587259208046897

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Solvent shift and inhomogeneous broadening of optical transitions in condensed matter are direct consequences of the dye‐matrix interaction. According to a stochastic theory, the ratio between the solvent shift and the width of an inhomogeneous distribution, and also its shape, depend on the average distance between the matrix units as compared to the size of the dopant molecules. In this way the nearly Gaussian shape of most absorption bands and the Lorentzian shape of spectral‐diffusion kernels can be explained within the framework of the same model. By performing site‐selective spectroscopic experiments at different frequencies within an absorption band it is possible to obtain more detailed information on the internal structure of the inhomogeneous distribution. Electric‐field studies of persistent spectral holes, for instance, show that in weakly polar systems, the solvent shift is mainly determined by the van der Waals interaction.

ISSN:1058-725X    

DOI:10.1080/10587259208046898

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

- Thiophene oligomers with extended π-systems can be considered as linear polyenes. They are stable and processible low molecular solids with electronic properties close to those of polythiophene. We report in this paper on the optical properties of vacuum evaporated oligothiophene thin films and their use as molecular semiconductors in the fabrication of “all‐organic” fieldeffect transistors.

ISSN:1058-725X    

DOI:10.1080/10587259208046899

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Stacked metallomacrocycles [MacM(L)]ncan be obtained by the so-called “shish kebab” approach1in which transition metallomacrocycles (MacM) are linked together by bidentate bridging ligands Q. Such bridged Macrocyclic metal compounds [MacM(L)]nwith transition metals e.g. Fe, Ru, Os, Co, Rh in various oxidation states have been synthesized by us.1Mostly as macrocycles (Mac), not only phthalocyanine (Pc), tetrabenzoporphyrine (TBP), but also macrocycles containing more extended p-systems like 1,2- or 2,3-naphthalocyanine (1,2-, 2,3-Nc) or phenanthrenocyanine (Phc) are used.1,2,3The bridging ligands (L) are bifunctional organic donor molecules, e.g. pyrazine (pyz),s-tetrazine (tz),p-diisocyanobenzene (dib), 1,4-diazabicyclo[2.2.2]octane (dabco) for metals in the oxidation state +2, or e.g. cyanide (CN−), thiocyanate (SCN−) or aide (N3−) for transition metals in the oxidation state +3.1aIn general, these complexes [MacM(L)]nare insoluble in organic solvents, however, soluble oligomers [R4PcM(L)]ncan be prepared using metallomacrocycles R4PcM, R =t-bu, et, M = Fe, Ru, which are substituted in the peripheric positions.4

ISSN:1058-725X    

DOI:10.1080/10587259208046900

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Liquid crystals possess a wide variety of interesting and useful properties which are strongly correlated to their structure. In order to modify and enhance certain useful properties we have examined the effects of systematic introduction of fluorine. Especially interesting examples are the influences on the phase range and type including ferroelectric properties and on miscibility leading to phase separation via spinodal decomposition of the anisotropic LC phase.

ISSN:1058-725X    

DOI:10.1080/10587259208046901

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Following our results obtained by organic MBE and “episorption” techniques with STM imaging, a more realistic approach to realizing novel material structures with low dimensionality was discussed. As a next phase to “nanoscopic” materials from conventional materials, future possibilities of “molecular planting” in terms of the combination of the organic MBE and “episorption” techniques with focused STM beam technique were introduced for organic molecular systems. The new concepts of “nanoscopic” materials and “nanoscopic” technology are bringing previously idealistic molecular electronic and photonic designs into the realm of achievable devices.

ISSN:1058-725X    

DOI:10.1080/10587259208046902

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A simple analytical expression for the charge photogeneration yield (φ) is derived which is based on the Onsager theory of geminate recombination. The expression shows non-Arrhenius temperature (T) dependence φ∼exp(-A/½) with A=2(ezα/4πϵ ϵk)½, where α is a characteristic parameter in the spatial (r) distribution function of thermalized electron-hole pairs g(r) = = (α/4πr2)exp(-αr). The values of α obtained on its basis from the literature experimental data for anthracene crystals are interpreted in terms of collision cross section for primary carriers. The discrete photon energy dependence of α can be explained by crystal anisotropy for the carrier motion.

ISSN:1058-725X    

DOI:10.1080/10587259208046903

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Generation and transport of charge carriers in poly(phenyl‐phenylenevinylene) and poly(3‐dodecylthiophene) have been investigated by means of dc and transient photoconductivity. Geminate pairs are formed by disorder assisted partial dissociation of singlet excitons of chain segments followed by temperature and field assisted dissociation in accord with 1D Onsager theory. In PDT secondary hole injection from an AL- anode is responsible for quantum yields > 1. It is initiated by O2ions accumulated at the interface.

ISSN:1058-725X    

DOI:10.1080/10587259208046904

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Results on steady-state and transient current photoconductivity in vacuum-evaporated films of linear trans-quinacridone (LTQUIN) are presented and discussed in terms of charge photogeneration and charge transport mechanisms. LTQUIN appeared to be a good photoconductor (photoconduction quantum yield φ>0.2 e/photon) with hole effective mobility μh≈ 10−4cm2/V s being a decreasing function of electric field. The hydrogen bonds present in the solid LTQUIN lead to some particular features of its photoconduction at high electric fields.

ISSN:1058-725X    

DOI:10.1080/10587259208046905

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Thin films of C60are fabricated by vacuum vapor deposition and their lateral photoconductivity is measured. We found unusual temperature dependence of photocurrents, the cause of which is so far unknown. From the comparison of photocurrent and absorption spectra it is shown that photocarrier generation efficiency is higher around absorption edge (600 nm). Photocurrents are found to increase in proportion to the square root of light intensity.

ISSN:1058-725X    

DOI:10.1080/10587259208046906

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor