Photophysics and photochemistry of the EE and ZE isomers of 1-(n-pyridyl)-4-phenyl-1,3-butadiene (n = 2, 3 and 4)

Bartocci, G.; Galiazzo, G.; Mazzucato, U.; Spalletti, Anna

doi:10.1039/b009107n

Cited by 20 publications

(39 citation statements)

References 24 publications

(8 reference statements)

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“…This behaviour, probably owing to a large torsional barrier in the lowest excited states, consistent with the experimental results, resembles that reported for analogous compounds with the N atom in ortho position to the ethenic bridge. The occurrence of one-way photoisomerization (only in one direction) because of the preferential stabilization of one of the two geometrical isomers was first reported in 1973 [7] and then found in several dihetarylethenes [8][9][10][11][12][13][14][15][16][17][20][21][22][23][24][25][26][27][28]. In addition to the case of 1-styrylisoquinoline cited above [11], other interesting examples are 1-(2 0 -pyridyl)-2-phenylbutadiene [21,22] (see Section 10.4) and 1-(2 0 -pyridyl),2-(2 00 -indolyl)ethene [13,15,16].…”

Section: Control Of Radiative and Reactive Relaxationmentioning

confidence: 99%

“…Z direction is quite uncommon for stilbene-like molecules, where very often the energy level of 1;3 Z * is higher than that of 1;3 E*. Very few examples are reported in the literature [23,[39][40][41][42]. As stated above, in some aza-diarylethenes, IHB may preferentially stabilize the Z geometrical isomer, inducing in some cases energy inversion of the 1;3 Z * and 1;3 E* species.…”

Section: Unusual Adiabatic Photoisomerization In the E ! Z Directionmentioning

confidence: 99%

“…ZE photoisomerization of 2-pyridylphenylbutadiene (2PyPhBu), whose marked deviations from the normal spectral behaviour and the reduced photoisomerization yield suggested a preferential stabilization of specific species by IHB involving the nitrogen in ortho position with respect to the adjacent ethenic bridge [23,24], as shown in Scheme 10.4.…”

Section: Unusual Adiabatic Photoisomerization In the E ! Z Directionmentioning

confidence: 99%

“…Within the framework of a long-term project on the study of internal rotation around single and double bonds in stilbene-like compounds, intramolecular NÁ Á ÁH interactions were found to play an important role in the relative stability of the conformers and in the photoreactivity and reaction mechanism of the geometrical isomers in the lowest excited states of singlet and triplet multiplicity ( 1;3 Z * and 1;3 E*) [20][21][22][23][24][25][26][27][28]. This behaviour was observed for specific positional isomers of compounds bearing one (or more than one) isomerizable double bond(s) when a suitable distance of the heteroatom favours the interaction with the closest hydrogen atom of the ethene bridge.…”

Section: Introductionmentioning

confidence: 99%

“…Photophysical and photochemical parameters of the geometrical isomers of 2PyPhBu in MCH/3MP at room temperature a (from Refs[23] and[24])…”

mentioning

confidence: 99%

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Effect of Intramolecular H‐Bond‐Type Interactions on the Photochemistry of Aza‐Stilbene‐Like Molecules

Bartocci

Mazzucato

Spalletti

2010

Hydrogen Bonding and Transfer in the Excited State

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It is well known that molecular photochemistry can be affected significantly by both intermolecular and intramolecular interactions, and that hydrogen bonding (HB) can play an important role in this respect. The abundant experimental and theoretical investigations reported in the literature on the role of the intramolecular hydrogen bond (IHB) in controlling the dynamics of excited molecules mainly refer to the process of hydrogen or proton transfer to a heteroatom acceptor under irradiation (a few representative examples are reported in Refs [1] to [6]). When the interaction of H with the accepting group is only moderately strong, the effect can be limited to favour specific conformations, geometrical configurations and deactivation channels of the excited molecule.Early work on the effect of intramolecular interactions on the cis-trans (Z-E) photoreaction of compounds containing isomerizable double bonds showed how IHB of moderate strength can control the direction and the extent of the photoreaction [7-11], inhibiting photoisomerization and enhancing competing relaxation processes, or vice versa. Later, detailed studies were carried out on diarylethenes bearing aza-aromatic groups, such as pyridyl, quinolyl, pyrrolyl and indolyl groups [12][13][14][15][16][17].When rotation around single bonds is operative, different conformations may display a different behaviour. It is well known that flexible molecules containing double bonds, such as 1,2-diarylethenes, can be found in fluid solution as a mixture of different conformational geometries (conformers or rotamers) that exist in dynamic equilibrium in the ground state (S 0 ). The competition between conjugative and steric effects leads

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Section: Control Of Radiative and Reactive Relaxationmentioning

confidence: 99%

Section: Unusual Adiabatic Photoisomerization In the E ! Z Directionmentioning

confidence: 99%

Section: Unusual Adiabatic Photoisomerization In the E ! Z Directionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Photophysical and photochemical parameters of the geometrical isomers of 2PyPhBu in MCH/3MP at room temperature a (from Refs[23] and[24])…”

mentioning

confidence: 99%

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Effect of Intramolecular H‐Bond‐Type Interactions on the Photochemistry of Aza‐Stilbene‐Like Molecules

Bartocci

Mazzucato

Spalletti

2010

Hydrogen Bonding and Transfer in the Excited State

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Fluorescence/photoisomerization competition in trans-aza-1,2-diarylethenes

et al. 2009

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The effect of the presence and position of the nitrogen heteroatom on the photobehaviour of a series of symmetric and asymmetric 1,2-diarylethenes, where one or both the one-, two- or three-membered aryl groups, linked to the ethene bridge, contain(s) nitrogen heteroatoms, has been investigated by fluorimetric and photochemical techniques. The yield of the radiative pathway is generally reduced with respect to the corresponding hydrocarbons, due to a smaller energy barrier for trans-->cis (E-->Z) photoisomerization in the singlet state, which often can be slightly favoured in the aza-compounds. All compounds investigated exist in solution as mixtures of two or more conformers, which can have different spectral and kinetic properties. Attempts to separate the intrinsic properties by selective photoexcitation, at a wavelength where the light is mainly absorbed by one conformer, allowed in some favourable cases the spectra and decay times of the largely prevalent (quasi-pure) conformer to be obtained. In two cases, the formation of intramolecular (hydrogen-bond-type) interactions between the nitrogen atom and the nearest hydrogen atom of the ethene bridge (proved by NMR measurements and confirmed by theoretical calculations) were found to stabilize a specific conformer thus affecting a selective relaxation of the excited molecule.

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Acid–base strength and acido(fluoro)chromism of three push–pull derivatives of 2,6-distyrylpyridine

Mencaroni

Cesaretti

Elisei

et al. 2022

Photochem Photobiol Sci

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The acidochromism and acid–base properties of 2,6-distyrylpyridine (2,6-DStP) derivatives bearing on the sides push/pull substituents (namely two dimethylamino, one nitro, and one methoxy and two nitro groups in the case of 2,6-bis[(E)-2-(4-dimetylaminophenyl)ethenyl]pyridine, 2-[(E)-2-(4-nitrophenyl)ethenyl],6-[(E)-2′-(4′-methoxyphenyl)ethenyl]pyridine and 2,6-bis[(E)-2-(4-nitrophenyl)ethenyl]pyridine, respectively) were investigated by stationary and time-resolved spectroscopies. The sensitivity of the absorption and emission spectrum to the medium acidity was found to enhance in the dimethylamino-derivative relative to the unsubstituted 2,6-DStP, also because of the second protonation by the N(CH3)2 group. Spectrophotometric titrations, also processed by a global fitting approach, gave pKa values, for the protonation of the central pyridine, higher in the derivatives with electron-donor unities and lower in compounds bearing electron-acceptor groups. A fluorometric titration was performed in the case of the dimethylamino-derivative thanks to non-negligible emission efficiencies for both neutral and protonated species, unveiling an attractive naked-eye acido(fluoro)chromism from green to yellow upon pyridine protonation, and then to purple with the second protonation involving the lateral N(CH3)2 substituent. Due to the extremely short excited-state lifetimes, as resulted from femtosecond transient absorption experiments, the pKa values for the excited state (pKa*) were estimated through the Förster cycle, revealing that the monoprotonated species of the dimethylamino-derivative would become upon excitation the only stable form in a wide range of pH. Graphical abstract

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Photophysics and photochemistry of the EE and ZE isomers of 1-(n-pyridyl)-4-phenyl-1,3-butadiene (n = 2, 3 and 4)

Cited by 20 publications

References 24 publications

Effect of Intramolecular H‐Bond‐Type Interactions on the Photochemistry of Aza‐Stilbene‐Like Molecules

Effect of Intramolecular H‐Bond‐Type Interactions on the Photochemistry of Aza‐Stilbene‐Like Molecules

Fluorescence/photoisomerization competition in trans-aza-1,2-diarylethenes

Acid–base strength and acido(fluoro)chromism of three push–pull derivatives of 2,6-distyrylpyridine

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