Organic photochromic systems represent a starting point for the elaboration of light-triggered molecular switching devices. The novel bispyridinium and bispyridine compounds 12+ and 6 were synthesized as their uncyclized isomers from 3,5-dibromo-2-methylthiophene in overall yields of 43 and 44%, respectively. The diarylethene photochromes 2 and 10–13, substituted with electron donors and acceptors, were prepared from 5-methylthiophene-2-carboxaldehyde in 21–32% overall yield. All of the compounds were found to exhibit pronounced photochromic properties. Irradiation with UV light resulted in essentially complete photocyclization of the open forms to the intensely coloured closed isomers which could, in turn, be reconverted back to the open state with visible light of γ>600 nm. The absorption maxima of the described compounds in their closed forms are shifted far towards, and even into, the near-IR region. Whereas no thermochromic properties were observed for the open isomers, the rates of thermal decolouration of the cyclized forms was found to be highly dependent on the nature of the substituents on the thiophene rings. It was demonstrated that reversible photochemical interconversion between the two photochromic states could be used to effectively switch a number of physical properties. Thus, the molecules 12+ and 12 represent two kinds of redox switches, the former in reduction and the latter in oxidation, in which electron conduction is switched on in the closed state and off in the open state. Compound 12 may also be considered to be a photoswitchable analogue of tetrathiafulvalene type substances. On the other hand, compound 2 displays a marked increase in nonlinear optical activity on conversion from the open to the closed form. Such systems are prototypes of photoswitchable molecular wires where electron conduction and push-pull interaction can be reversibly modulated by an external stimulus, namely, irradiation by light.

Light‐Triggered Molecular Devices: Photochemical Switching Of optical and Electrochemical Properties in Molecular Wire Type Diarylethene Species

The mixed-valence character of a set of six bistriarylamine derivatives with varying π-electron spacers has been investigated. The distances of triarylamine redox centers vary from 0.5 nm (N,N,N‘,N...

The Class II/III Transition in Triarylamine Redox Systems

The transition metal coordination chemistry of anion radicals

3.3. Influence of the Bridge Redox States 5159 4. Multidimensional Organic Mixed Valence 5163 5. Intervalence Charge Transfer across Noncovalent Pathways 5167 6. Use of EPR Spectroscopy as a Direct Test for Hush Theory 5170 7. Solvent and Ion Pairing Effects 5171 8. Crystallographic Studies 5173 9. Concluding Remarks 5175 Author Information 5175 Biographies 5175 Acknowledgment 5176 References 5176

Organic mixed valence.

Described is the construction of an ultrafast electrochromic window. One electrode of this window is based on a transparent nanostructured TiO2 (anatase) film (4.0 mum. thick) supported on conducti ...

Ultrafast electrochromic windows based on redox-chromophore modified nanostructured semiconducting and conducting films

Two step reversible redox systems of the weitz type

Mehrstufige reversible Redoxsysteme, XXXV. Voltammetrie vinyloger Polyene mit gekreuzt konjugierten Endgruppen und UV/VIS‐Spektroskopie ihrer Radikalanionen und ‐kationen

3-Aryl-3-chloro-1,2-diaziridines as Isolable Intermediates in the Preparation of 3-Aryl-3-chloro-3H-1,2-diazirines



The formation of 3-aryl-3-chloro-3H-1,2-diazirines 3 from arylamidines 1 with sodium hypo-chlorite passes through intermediate 3-aryl-3-chloro-1,2-diaziridines 2, which are isolable at low temperature. The direct path 1 3 so far suggested therefore becomes unlikely.

Horst Berneth

Papers

Two step reversible redox systems of the weitz type

Mehrstufige reversible Redoxsysteme, XXXV. Voltammetrie vinyloger Polyene mit gekreuzt konjugierten Endgruppen und UV/VIS‐Spektroskopie ihrer Radikalanionen und ‐kationen

3‐Aryl‐3‐chlor‐1,2‐diaziridine als isolierbare Zwischenprodukte bei der Darstellung von 3‐Aryl‐3‐chlor‐3H‐1,2‐diazirinen

Voltammetrie von Triazeniumsalzen

Benzol-1.4-Bis(diphenylcyclopropenylium)-dikation