Über intramolekulare Ionisation

Wizinger, R.; Wenning, H.

doi:10.1002/hlca.19400230133

Cited by 73 publications

(11 citation statements)

References 5 publications

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“…The reduced tendency towards ring opening in benzospiropyrans compared to naphthospiropyrans supports this model as formation of the quinoidal structure requires loss of aromaticity in the former, reflected also in the oxidation potential of o-benzoquinone (0.833 V) and that of 6-naphthoquinone (0.576 V). 41 Thus, for thermochromism to occur it was established that one of the pyran rings has to be at least a naphthopyran, unless the structure of the heterocyclic ring contributes significantly to the stabilization of delocalized charge in the conjoined spiro-centre, as seen in the indolinobenzospiropyrans reported by Wizinger 38 and popularized by Fischer 26 (vide infra).…”

Section: Methodsmentioning

confidence: 99%

“…The second major aspect that determines ring-opening, therefore, is the electron releasing ability of the heterocyclic ring (dotted in Scheme 4), which can be complemented by stabilization of the phenolate by appropriate substituents on the pyran ring (Y in Scheme 4). 37,38,42 Last but not least, both steric substitution and the presence of an acidic hydrogen at the R-position (Scheme 4) have also been shown to dictate the driving force of isomerization, as substitution of the C 3 0 hydrogen obstructs ring opening. 43 Though the proposed steric blocking of concurrent planarization became the accepted rationalization of this effect eventually, an initially proposed H-bonding stabilizing interaction between the C 3 0 -H and phenol in the ring-open form 44 turns out to play a pivotal role as discovered more recently (vide infra).…”

Section: Methodsmentioning

confidence: 99%

“…Although the thermochromism of 1,3,3-trimethylindolinobenzospiropyran (Scheme 2) was reported in 1940 already (vide supra), 38 the first account of its photochromism was made by Fischer and Hirshberg only in 1952, 26 in which the thermal barrier to the merocyanine form was shown to be overcome by photoexcitation. In 1989 switching induced by two photon absorption with visible and NIR light was demonstrated also.…”

Section: Photochromism Of Spiropyransmentioning

confidence: 99%

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The evolution of spiropyran: fundamentals and progress of an extraordinarily versatile photochrome

2019

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Section: Photochromism Of Spiropyransmentioning

confidence: 99%

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The evolution of spiropyran: fundamentals and progress of an extraordinarily versatile photochrome

2019

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“…New water-soluble spiropyarans were synthesized accordingt o the classical methodo fW izinger and Wennig, [55] which is the most common procedure to obtain al arge variety of different spiropyrans.C ondensationo famethylene base (or its quaternary salt) with an o-hydroxy aromatica ldehyde in boiling alcohol yields the desired spiropyran under cleavageo fo ne water molecule (Scheme 2). In the present case, we used anhydrous methanoli nsteado ft he usually applied ethanolf or reasonso f solubility of the precursors.…”

Section: Synthesis Of Sulfonated Spiropyransmentioning

confidence: 99%

Water‐Soluble Spiropyrans with Inverse Photochromism and Their Photoresponsive Electrostatic Self‐Assembly

Moldenhauer

Gröhn

2017

Chemistry A European J

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A new type of light responsive nanoscale assemblies based on water-soluble spiropyrans is presented. We have synthesized four anionic spiropyrans bearing multiple sulfonate groups and investigated their photochromic behavior in aqueous solution. Depending on the pH, either inverse photochromism (acidic conditions) or normal photochromism (alkaline conditions) is found. Kinetic data for the interconversion of the spiropyran and merocyanine isomers including the subsequent slow hydrolysis have been obtained by UV/Vis spectroscopy. The results show that the spiropyrans undergo hydrolysis in both alkaline and acidic solution, while in the latter the rate is far slower than in the former. This prolonged hydrolytic stability together with the inverse photochromism under acidic conditions makes the sulfonated spiropyrans suitable to build photoresponsive nanostructures with cationic polyelectrolytes. We show how the self-assembly process is driven by electrostatic interactions and how the spiropyrans' photochromic property allows the size control of the supramolecular objects by visible light. The assembly size is characterized by dynamic light scattering and TEM. In addition, UV/Vis and fluorescence spectroscopy and ζ-potential measurements help to explain the size change upon visible light irradiation.

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“…1) [17][18][19] [20] and [21], respectively. The purity of the compound was controlled by TLC, mp, NMR spectroscopy, and ele mental analysis.…”

mentioning

confidence: 99%

Spectral and kinetic parameters of transient species in the photolysis of naphthylmethylideneiminospironaphthopyran by excitation at different wavelengths: Nano- and femtosecond laser photolysis

et al. 2013

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The synthesis, photochemistry, and photophysics of multifunctional photochromic systems are cur rently the subject of intensive research. Such systems can be used as photochemical probes and labels to monitor fine properties of complex chemical and bio logical objects [1]. These compounds are also promis ing for the design of materials for next generation molecular electronics [2,3].In [4,5] we reported procedures for the synthesis of photobifunctional compounds (PBCs) of two types. The PBCs contain two structural moieties with differ ent photochemical properties, the spirocyclic (indoli nonaphthopyran or naphthooxazine) and azomethine units, which are bound into the molecule in different modes. In the photolysis of these PBCs, the opening of the spirocycle to give the relatively long livied, colored merocyanine form absorbing light in the range of 550-650 nm occurs in the one moiety, and intramolecular proton transfer and cis-trans isomerization to give the relatively short lived isomer absorbing at 400-500 nm occurs in the other [6][7][8][9][10][11][12]. It has been shown that these photoprocesses can be induced selectively in some PBCs by varying the wavelength of excitation light [11,12]. This feature of PBCs can be useful from the standpoint of their application in devices requiring targeted photoinitiation of different processes by vary ing the excitation light wavelength. 1,3 Dihydro 5 (2 hydroxy 1 naphthylmethylide neimino) 1,3,3 trimethylspiro[2H indole 2,3 [3H] naphtho[2,1 b]pyran] is an example of PBC in which the ratio of the efficiencies of photoprocesses strongly depends on the excitation light wavelength. Recently [11,12], we studied the spectral and kinetic parame ters of relatively long lived photolysis products of this compound and found that two photochromic pro cesses can occur simultaneously: the formation of the merocyanine form in the spironaphthopyran moiety and cis-trans photoisomerization in the azomethine moiety.In this paper, we present results of a femtosecond laser photolysis study of the dynamics of ultrafast pho tophysical processes in this PBC excited at wave lengths of about 340 and 490 nm in methanol solution and compare the results with the data obtained by nanosecond laser photolysis. 1 (Phenyliminomethyl) 2 naphthol (PN) and 1,3 dihydro 1,3,3 trimethylspiro[2H indole 2,3' [3H] naphtho[2,1 b]pyran] (SNP) model the moi eties of the PBC molecule under study: PHOTOCHEMISTRYAbstract-Intramolecular processes occurring in a photobifunctional compound (PBC) comprising the spironaphthopyran and hydroxyazomethine moieties have been studied in methanol solutions by femtosec ond laser photolysis using light with wavelengths of 340 and 490 nm. At the excitation wavelength of 490 nm, the cis-trans photoisomerization in the azomethine moiety occurs in the S 1 state. In the case of PBC photol ysis with 340 nm light, the opening of the spiro bond of the spiropyran moiety (formation of the X form) also takes place during relaxation of the S n state to the S 1 state followed by isomerization to...

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Über intramolekulare Ionisation

Cited by 73 publications

References 5 publications

The evolution of spiropyran: fundamentals and progress of an extraordinarily versatile photochrome

The evolution of spiropyran: fundamentals and progress of an extraordinarily versatile photochrome

Water‐Soluble Spiropyrans with Inverse Photochromism and Their Photoresponsive Electrostatic Self‐Assembly

Spectral and kinetic parameters of transient species in the photolysis of naphthylmethylideneiminospironaphthopyran by excitation at different wavelengths: Nano- and femtosecond laser photolysis

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