Photochemistry of metalloporphyrin complexes. Ligand photoisomerization via intramolecular energy transfer

Whitten, David G.; Wildes, Peter D.; DeRosier, Carol A.

doi:10.1021/ja00777a025

Cited by 63 publications

(30 citation statements)

References 9 publications

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“…25 A more quantitative picture of the process as well as confirmation of eqs. (I)-(10) as the mechanism for the photocatalysis can be gained by examination of intramolecular photosensitization with some modified derivatives of NPE and 4-stilbazole.…”

Section: ~C-t Ffi [Ks + Kt(lc)][ks + K~o][k + Ks] -Kt(lc)kek4mentioning

confidence: 80%

“…24 Results with different sensitizers and the observation of weak singlet-triplet spectra indicate that triplet levels for the uncomplexed 4-stilbazole isomers are similar to those of the stilbenes while slightly lower energies are indicated for the isomers of NPE. 25 Both NPE and 4-stilbazole isomers form complexes with zinc and magnesium porphyrin complexes in which the long-wavelength transitions (porphyrin ~r--,~r* bands) are essentially identical to those of pyddine or piperidine complexes. Since excess 4-stilbazole or NPE must be added to solutions containing the zinc and magnesium porphyrins, it is not possible to determine the effect complex formation produces on the ligand transitions; however, for the cobalt (III) complexes, which do not undergo exchange, a subtraction spectrum indicates that the ligand ~r ~ ~r* transitions are shifted to longer wavelengths (for NPE the ~,~x shifts from 331 to 353 nm with a corresponding but smaller shift in the band onset) and that excitation energies may be lowered by several kcal tool-1.…”

Section: Intramolecular Triplet Energy Transfer In Metalloporphyrimentioning

confidence: 99%

“…(4), that the activation energy for the process is only 2.5 kcal tool-1. 25 Since the difference in "spectroscopic" triplets of zinc porphyrin and olefin is estimated to be 10-12 kcal tool -~, it is clear that the triplet populated must not be the cisoid triplet but more likely one of twisted geometry. Not surprisingly the value of AS* for the process is -34 eu.…”

Section: Dg Whitenmentioning

confidence: 99%

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Photochemistry of porphyrins and their metal complexes in solution and organized media

Whitten

1978

Reviews of Chemical Intermediates

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Section: ~C-t Ffi [Ks + Kt(lc)][ks + K~o][k + Ks] -Kt(lc)kek4mentioning

confidence: 80%

Section: Intramolecular Triplet Energy Transfer In Metalloporphyrimentioning

confidence: 99%

Section: Dg Whitenmentioning

confidence: 99%

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Photochemistry of porphyrins and their metal complexes in solution and organized media

Whitten

1978

Reviews of Chemical Intermediates

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“…Das gilt fur die sensibilisierte und nicht sensibilisierte E/Z-Isornerisierung (a+ d) [45][46][47][48][49], die Photocyclisierung zu (Aza)Phenanthrenderivaten (e -+ f ) 5 0 -5 s ) und auch die Photodimerisierung zu Cyclobutanen C8 ( a + k)'Q. Bei den Azaderivaten treten in starker Abhangigkeit von der Stellung des Stickstoffs zusatzliche Photoprozesse auf, wie die Bildung von Azadihydrophenanthrenderivaten uber 1,3-Wasserstoffverschiebungen (e + g)50).…”

Section: Photodimerisierungen In Losungunclassified

Pyridylsubstituierte Cyclobutane durch Photodimerisierung von Azastilbenen

Horner

Hünig

1982

Liebigs Ann. Chem.

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Die Mono-und Diazastilbene A 1 -A 9 werden, auch als ihre Mono-und Dihydro-oder -alkylQuartirsalze, mit UV-Licht bestrahlt. Die Monosalze werden im Kristall und/oder in Losung glatt zu Cyclobutanen C dimerisiert. Die freien Basen A oder ihre Bis-Salze, die nur in Losung reagieren, bilden teilweise oder vollstlndig andere Produkte. Deren Struktur, sowie die Konstitution und Konfiguration von C1-C9 werden aufgekllrt. Literaturergebnisse werden teils bestiltigt, teils korrigiert. Pyridyl-substituted Cyclobutanes viu Photodimerisation of AzastilbenesMono-and diazastilbenes A 1 -A 9 as well as their mono-and dihydro-or -alkyl quaternary salts are irradiated (UV). Mono salts are smoothly converted into cyclobutanes C in crystalline state and/or in solution. The free bases A or their bis salts, reacting in solution only, form partly or exclusively different products. Their structures together with the constitutions and configurations of the cyclobutanes A are elucidated. Results from the literature are partly confirmed and partly corrected. ZielsetzungIn unsere Untersuchungen ilber mehrstufige reversible Redoxsysteme2) sollten auch Verbindungen einbezogen werden, die zwischen den Pyridylendgruppen das Kohlenstoffgeriist der Quadratsilure l s 3 ) oder des Bicycl~butans~*~) besitzen. Als geeignetes Ausgangsmaterial hierfiir boten sich pyridylsubstituierte Cyclobutane (,,C") an, die wiederum -wie einige Literaturbeispiele zeigens -aus den ebenfalls zum Teil bekannten Azastilbene" (,,A") durch Photodimerisierung darstellbar sein sollten. Diese Reaktionsfolge bildet, zusammen mit der Konstitutions-und Konfigurationsaufkllrung der Cyclobutane C den Inhalt der vorliegenden Abhandlung. Synthesen der Azastilbene A1 -A9Die meisten der eingesetzten Monoaza-und Diazastilbene sowie ihre Salze (vgl. Tab. I und 2) waren literaturbekannt. Sie werden im allgemeinen durch Knoevenagel-Kondensation gewonnen. Abweichungen verschiedener Darstellungsvorschriften fur AS, Me16.') aus 1,4-Dimethylpyridiniurn-iodid (1) und 4-Pyridincarbaldehyd (2) wurden zum Anial3 genommen, den EinfluD der Reaktionsdauer zu pfifen. Dabei zeigte sich eine drastische Ausbeuteverminderung mit zunehrnender Reaktionszeit; ein PhPnomen,

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“…[75] the stilbazole ligand (in both directions) was not hampered by the presence of the aluminum porphyrin complex, which is in line with previous mechanistic studies in related systems. [79,80] Successful photocontrol of the stereochemical outcome of a cyclopropanation reaction was demonstrated by Branda and co-workers utilizing chiral dithienylethene (DTE) ligands (Scheme 8). [81] Classification of this system according to the concepts given in Section 3.1 is not straightforward.…”

Section: Photochromic Additivesmentioning

confidence: 99%

Artificial Light‐Gated Catalyst Systems

2010

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Having control over an entity or even an entire process is arguably the ultimate demonstration of its understanding and it will enable its potential to be fully exploited. With this in mind, chemists have not only been creating and optimizing a myriad of different catalysts for most (relevant) chemical reactions over the past decades, but have recently started to implement controlling elements into the catalyst design. These incorporated gates operate upon exposure to suitable control stimuli, and light represents perhaps the scientifically and technologically most attractive stimulus. In principle, irradiation can thereby induce activity and selectivity in a given catalyst system with high spatial and temporal control, leading to an overall localization and amplification of an optical signal and translation into chemical action. While nature has developed and utilized this concept, in particular in the processes of vision and photomovement, such artificial photocontrolled catalyst systems offer unique opportunities and have high potential for future applications. In this Review, we outline the general concept of light-gated catalysis based on photocaged and also photoswitchable systems, and discuss relevant examples of the past and recent literature.

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Photochemistry of metalloporphyrin complexes. Ligand photoisomerization via intramolecular energy transfer

Abstract: and 5.5-5.7 (mult, 2 H). The mass spectrum showed peaks for a molecular ion at 326 and 328.

Cited by 63 publications

References 9 publications

Photochemistry of porphyrins and their metal complexes in solution and organized media

Photochemistry of porphyrins and their metal complexes in solution and organized media

Pyridylsubstituierte Cyclobutane durch Photodimerisierung von Azastilbenen

Artificial Light‐Gated Catalyst Systems

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