Photoisomerization mechanisms and photoselectivity of the stereoisomers of 1-(pyrid-n-yl),4-phenylbuta-1,3-diene

Bartocci, G.; Galiazzo, G.; Latterini, Loredana; Marri, Elena; Mazzucato, U.; Spalletti, Anna

doi:10.1039/b200353h

Cited by 15 publications

(15 citation statements)

References 15 publications

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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%

“…As the process is generally less activated, or even barrierless, when starting from the Z side, the adiabatic mechanism has been mainly evidenced for the reaction in the 1;3 Z * ! 1;3 E* direction, where the formation of Conformational equilibrium of two E-styrylquinolines [24]. Reproduced by permission of the PCCP Owner Societies 1 E* is easily recognized from its fluorescence, and that of 3 E* from the transient absorption spectrum obtained by laser flash photolysis.…”

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%

“…processes in the triplet manifold in the more common cis ! trans direction, indicating that the preferential stabilization of the compounds with a double bond in cis configuration adjacent to the pyridyl group (ZE and ZZ), with respect to EE and EZ respectively, is not operative in the triplet state [24]. The sketch of the potential energy curves of the excited singlet state, shown in Figure 10.3, reflects the observed behaviours, which obviously depend on the shape of the energy surfaces as a function of the rotation around the ethenic bonds.…”

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%

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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: Unusual Adiabatic Photoisomerization In the E ! Z Directionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 3 more Smart Citations

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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Preparation of Butadienylpyridines by Iridium‐NHC‐Catalyzed Alkyne Hydroalkenylation and Quinolizine Rearrangement

Azpíroz

Greger

Oro

et al. 2021

Chemistry A European J

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Iridium(I) N‐heterocyclic carbene complexes of formula Ir(κ2O,O’‐BHetA)(IPr)(η2‐coe) [BHetA=bis‐heteroatomic acidato, acetylacetonate or acetate; IPr=1,3‐bis(2,6‐diisopropylphenyl)imidazolin‐2‐carbene; coe=cyclooctene] have been prepared by treating Ir(κ2O,O’‐BHetA)(η2‐coe)2 complexes with IPr. These complexes react with 2‐vinylpyridine to afford the hydrido‐iridium(III)‐alkenyl cyclometalated derivatives IrH(κ2O,O’‐BHetA)(κ2N,C‐C7H6N)(IPr) through the iridium(I) intermediate Ir(κ2O,O’‐BHetA)(IPr)(η2‐C7H7N). The cyclometalated IrH(κ2O,O’‐acac)(κ2N,C–C7H6N)(IPr) complex efficiently catalyzes the hydroalkenylation of aromatic and aliphatic terminal alkynes and enynes with 2‐vinylpyridine to afford 2‐(4R‐butadienyl)pyridines with Z,E configuration as the major reaction products (yield up to 89 %). In addition, unprecedented (Z)‐2‐butadienyl‐5R‐pyridine derivatives have been obtained as minor reaction products (yield up to 21 %) from the elusive 1Z,3gem‐butadienyl hydroalkenylation products. These compounds undergo a thermal 6π‐electrocyclization to afford bicyclic 4H‐quinolizine derivatives that, under catalytic reaction conditions, tautomerize to 6H‐quinolizine to afford the (Z)‐2‐(butadienyl)‐5R‐pyridine by a retro‐electrocyclization reaction.

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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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Photoisomerization mechanisms and photoselectivity of the stereoisomers of 1-(pyrid-n-yl),4-phenylbuta-1,3-diene

Cited by 15 publications

References 15 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

Preparation of Butadienylpyridines by Iridium‐NHC‐Catalyzed Alkyne Hydroalkenylation and Quinolizine Rearrangement

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

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