The photocyclisation of 1,2-Ciarylpyridinium cations and the photobiscyclisation of 1,2,6-triarylpyridinium cations

Katritzky, Alan R.; Zakaria, Zuriati; Lunt, E.

doi:10.1039/p19800001879

Cited by 41 publications

(29 citation statements)

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“…Note, when adding two aryl groups at the meta positions of the pyridinium core, that is, going from tetra‐branched ( 1 R2 , Scheme ) to hexa‐branched ( 2 R2 , Scheme ), the site of photoinduced cyclodehydrogenation is shifted from the N pyridinio ‐aryl group towards the tolyl terminus at the 4‐position of the pyridinium ring. Although this finding is, at first glance, in contradiction with the conclusions of the studies of Katritzky and co‐workers, which suggest that electron‐donating substituents disfavor (or deactivate) photochemical cyclodehydrogenation,39 it is, however, in line with another particular observation by the same author that “where the possibility exists of alternative cyc1izations to a phenyl or a p ‐tolyl group, the latter seems to be preferred” 39b. This is the case for 2 Me f , which is by far the main photoproduct as judged from the 1 H NMR spectrum of the reaction’s crude (see Figure S‐VIIa in the Supporting Information).…”

Section: Resultscontrasting

confidence: 72%

Expanded Pyridiniums: Bis‐cyclization of Branched Pyridiniums into Their Fused Polycyclic and Positively Charged Derivatives—Assessing the Impact of Pericondensation on Structural, Electrochemical, Electronic, and Photophysical Features

Fortage

Tuyèras

Ochsenbein

et al. 2010

Chemistry A European J

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This study evaluates the impact of the extension of the π-conjugated system of pyridiniums on their various properties. The molecular scaffold of aryl-substituted expanded pyridiniums (referred to as branched species) can be photochemically bis-cyclized into the corresponding fused polycyclic derivatives (referred to as pericondensed species). The representative 1,2,4,6-tetraphenylpyridinium (1(H)) and 1,2,3,5,6-pentaphenyl-4-(p-tolyl)pyridinium (2(Me)) tetra- and hexa-branched pyridiniums are herein compared with their corresponding pericondensed derivatives, the fully fused 9-phenylbenzo[1,2]quinolizino[3,4,5,6-def]phenanthridinium (1(H)f) and the hitherto unknown hemifused 9-methyl-1,2,3-triphenylbenzo[h]phenanthro[9,10,1-def]isoquinolinium (2(Me)f). Combined solid-state X-ray crystallography and solution NMR experiments showed that stacking interactions are barely efficient when the pericondensed pyridiniums are not appropriately substituted. The electrochemical study revealed that the first reduction process of all the expanded pyridiniums occurs at around -1 V vs. SCE, which indicates that the lowest unoccupied molecular orbital (LUMO) remains essentially localized on the pyridinium core regardless of pericondensation. In contrast, the electronic and photophysical properties are significantly affected on going from branched to pericondensed pyridiniums. Typically, the number of absorption bands increases with extended activity towards the visible region (down to ca. 450 nm in MeCN), whereas emission quantum yields are increased by three orders of magnitude (at ca. 0.25 on average). A relationship is established between the observed differential impact of the pericondensation and the importance of the localized LUMO on the properties considered: predominant for the first reduction process compared with secondary for the optical and photophysical properties.

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Section: Resultscontrasting

confidence: 72%

Expanded Pyridiniums: Bis‐cyclization of Branched Pyridiniums into Their Fused Polycyclic and Positively Charged Derivatives—Assessing the Impact of Pericondensation on Structural, Electrochemical, Electronic, and Photophysical Features

Fortage

Tuyèras

Ochsenbein

et al. 2010

Chemistry A European J

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“…The synthesis of the 1‐aryl‐2,4,6‐triphenylpyridinium salts and their subsequent dehydrogenations were carried out by a modified literature procedure5 (see the http://www.wiley-vch.de/contents/jc_2002/2007/z700515_s.pdf). PQPX‐6 and PQPX‐14 with chloride and tetrafluoroborate as counterions were synthesized in this way (Scheme ).…”

Section: Methodsmentioning

confidence: 99%

Self‐Assembly of Positively Charged Discotic PAHs: From Nanofibers to Nanotubes

et al. 2007

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Mind your PQPs: 1D nanostructures were fabricated by the self‐assembly of amphiphilic centrally charged discotic 9‐alkyl‐2‐phenylbenzo[8,9]quinolizino[4,5,6,7‐fed]phenanthridinylium (PQP) salts. Increasing the alkyl chain length of the PQP salts resulted in nanoscaled lamellar structures, whereas changing the counterion of the PQP salts from Cl− to BF4− led to a change from nanoribbons to helices and tubes.

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“…The incorporation of heteroatoms into the aromatic skeleton of such PAHs offers an opportunity to strongly influence their intermolecular carrier‐transport properties when they are fabricated into nanoarchitectural devices 3f. 4 Although a few centrally charged discotic PAHs have been synthesized,5 to the best of our knowledge, their aggregation behavior has not been reported.…”

Section: Methodsmentioning

confidence: 99%

“…The synthesis of the 1‐aryl‐2,4,6‐triphenylpyridinium salts and their subsequent dehydrogenations were carried out by a modified literature procedure5 (see the http://www.wiley-vch.de/contents/jc_2001/2007/z700515_s.pdf). PQPX‐6 and PQPX‐14 with chloride and tetrafluoroborate as counterions were synthesized in this way (Scheme ).…”

Section: Methodsmentioning

confidence: 99%

Self‐Assembly of Positively Charged Discotic PAHs: From Nanofibers to Nanotubes

Wu¹,

Zhi²,

Bodwell³

et al. 2007

Angewandte Chemie

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Variable Steuerung: 1D‐Nanostrukturen wurden durch die Selbstorganisation amphiphiler zentral geladener diskotischer 9‐Alkyl‐2‐phenylbenzo[8,9]chinolizino[4,5,6,7‐fed]phenanthridinylium(PQP)‐Salze erhalten. Längere Alkylketten in den PQP‐Salzen führten zu nanoskaligen lamellaren Strukturen, der Wechsel des Gegenions der PQP‐Salze von Cl− zu BF4− dagegen verwandelte die Nanobänder in Nanohelices und ‐röhren.

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The photocyclisation of 1,2-Ciarylpyridinium cations and the photobiscyclisation of 1,2,6-triarylpyridinium cations

Cited by 41 publications

References 1 publication

Expanded Pyridiniums: Bis‐cyclization of Branched Pyridiniums into Their Fused Polycyclic and Positively Charged Derivatives—Assessing the Impact of Pericondensation on Structural, Electrochemical, Electronic, and Photophysical Features

Expanded Pyridiniums: Bis‐cyclization of Branched Pyridiniums into Their Fused Polycyclic and Positively Charged Derivatives—Assessing the Impact of Pericondensation on Structural, Electrochemical, Electronic, and Photophysical Features

Self‐Assembly of Positively Charged Discotic PAHs: From Nanofibers to Nanotubes

Self‐Assembly of Positively Charged Discotic PAHs: From Nanofibers to Nanotubes

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