Structures and photochemical reactions of 1-(9-anthryl)-2-aroylethylenes: competing <i>cis</i>–<i>trans</i> isomerization and skeletal rearrangement

Mori, Yusuke; Maeda, Kōko

doi:10.1107/s0108768193008961

Cited by 19 publications

(5 citation statements)

References 4 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…S4, ESI †), consistent with a previous report. 23 However, the characteristic singlet peak of the cis-1 isomer at 4.24 ppm was not observed after UV irradiation, indicating almost no occurrence of trans-to-cis photoisomerisation. The yield of [4 + 4] cycloadduct 2 was estimated to be 4% from the hydrogen integration.…”

Section: Photomechanical Motionmentioning

confidence: 96%

“…In contrast, intermolecular [4 + 4] photodimerisation of the anthracene chromophore of trans-1 occurs in a crystalline state (Scheme 1). 23,24 Herein, we report the bending motion of rod-like trans-1 microcrystals upon ultraviolet (UV) irradiation. The possible mechanism behind this bending is also discussed based on in situ X-ray measurements and calculations of the optimised anthracene dimer product.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Mechanical motion of molecular crystals induced by [4 + 4] photodimerisation

et al. 2016

View full text Add to dashboard Cite

The photomechanical bending of crystals of a stilbene-type compound substituted with anthracene and indanone groups, (E)-2-(9-anthrylmethylene)-1-indanone (trans-1), was investigated. When a narrow platelike microcrystal was irradiated with ultraviolet (UV) light at 365 nm, the crystal gradually bent away from the light source and finally reached a semicircular shape after more than 10 min. A larger rod-like crystal, approximately 10 mm in length, also exhibited a slight bending motion. The cessation of UV irradiation caused the bent crystals to return very slowly to their straight form. In the crystals, the anthracene planes of two neighbouring trans-1 molecules are arranged in a head-to-tail parallel manner, with a short planeto-plane distance of only 3.72 Å. The 1 H nuclear magnetic resonance spectra of trans-1 crystals before and after UV irradiation revealed the intermolecular [4 + 4] photodimerisation of the two anthracene planes, while the trans-to-cis photoisomerisation was not significant. The UV-vis absorption spectra of the trans-1 powder crystals, obtained using a diffuse reflectance spectrophotometer, showed a gradual increase in absorbance between 200 and 500 nm with increasing UV irradiation time, reaching a maximum after 1 h. Thermal back-monomerisation was very slow in the dark, not recovering the initial spectrum even after 25 days. The fluorescence spectra at 570 nm, derived from the anthracene excimer, decreased in intensity with increasing UV irradiation time due to a decrease in the amount of anthracene chromophore via photodimerisation. In situ X-ray measurements revealed that the bending of the crystals was caused by slight elongation of the b axis of the unit cell, corresponding to the long axis of the rod-like crystals. Calculations revealed that the observed crystal elongation could be explained by an optimised head-to-tail [4 + 4] orientation of the anthracene dimer.

show abstract

Section: Photomechanical Motionmentioning

confidence: 96%

Section: Introductionmentioning

confidence: 99%

Mechanical motion of molecular crystals induced by [4 + 4] photodimerisation

et al. 2016

View full text Add to dashboard Cite

show abstract

“…[5,8] This report prompted several studies focusing on the mechanism of cis-trans isomerization in crystals. [9][10][11][12][13][14][15][16] Currently four mechanisms exist, including the original suggestion by Schmidt, to rationalize the cis-trans isomerization in crystals: (a) isomerization via a metastable dimer intermediate, (b) conventional one bond (C=C) rotation, [17,18] (c) two bond rotation of adjacent single and double bonds (Hula twist), [19][20][21][22] and (d) bicycle pedal mechanism involving concurrent isomerization of more than one double bond. [23][24][25][26] A few examples of cis-trans isomerization where the adjacent C=C bonds are separated by more than 4.2 Å have also been reported since Schmidt and co-workers' report casting doubt on the role of a metastable dimer during cis-trans isomerization.…”

Section: Introductionmentioning

confidence: 99%

Volume demanding geometric isomerization of cis-4-stilbazole. HCl salts in the crystalline state: Probing the role of a metastable dimer

Mondal

Captain

Ramamurthy

2016

Journal of Photochemistry and Photobiology A: Chemistry

View full text Add to dashboard Cite

Cis-trans isomerization is one of the most common and well-investigated photoreaction of olefins in solution. This occurs via 180° rotation of one of the substituents on C=C bond requiring large space around the double bond. One would expect that in crystals the neighboring molecules would prohibit such a process. In spite of this in early 1960s Schmidt and co-workers reported occurrence of such a process in crystals via 2+2 'meta cyclobutane' formation. In this study by examining the photochemistry of four cis-stilbazolium salts we show that the photoconversion to the corresponding trans isomers does not occur via 2+2 addition. Large separation that ensures considerable space between neighboring olefins favors cis-trans isomerization in crystals. An aspect that is puzzling is that the product trans isomer phase separates and recrystallizes within the parent cis crystals and photodimerizes to the cyclobutane dimer. Details of this phenomenon are to be understood.

show abstract

“…Scheme 1 shows the known examples of E / Z ‐ and Z / E ‐isomerizations within crystals. The Z / E ‐isomerizations of 4 (8), 7 (9), 8 (10), 9 (10), 12 (11) and the E / Z ‐isomerizations of 5 (12), 6 (12), 10 (13), 11 (14) proceed unidirectionally, and a clear‐cut explanation for these observations has been given from their experimentally derived solid‐state mechanisms. All these isomerizations are of interest because they experience particularly large geometric changes upon photoreaction.…”

Section: Introductionmentioning

confidence: 99%

Hula-twist Within the Confinement of Molecular Crystals¶

Kaupp¹

2002

Photochemistry and Photobiology

View full text Add to dashboard Cite

E/Z‐photoisomerizations within molecular crystals are varied. Existing cases are summarized. They require crystal lattices that allow for long‐range molecular movements in the nontopotactic solid‐state mechanism. Reactivity and directionality can be foreseen on the basis of the crystal packing. The reacting crystal changes continuously by phase rebuilding, phase transformation and disintegration. Two possibilities for the chemical mechanism exist: (1) highly space‐demanding (cooperative) double‐bond rotations; and (2) space‐conserving hula‐twist (HT) motions while the substituents move within their planes and only one C—H unit undergoes out‐of‐plane translocation. If internal rotation cannot be reasonably modeled within the crystal lattice, HT remains the only choice, as in the case of trans‐1,2‐dibenzoylethene. Direct experimental proof is still lacking because the differences in the conformational outcome could not be assessed in the studied examples. Density functional theory calculations of cis‐1,2‐dibenzoylethene revealed very low differences in energy content of the helical (s‐cis, s‐cis)‐ and the almost orthogonal (s‐cis, s‐trans)‐cis‐conformers. The almost orthogonal (s‐cis, s‐trans)‐cis‐conformer that is found in the pure crystal is very similar to the calculated counterpart. It is suggested that more favorable initial conformers might be obtained by proper vinylic substitution. The stereochemical outcome of highly space‐demanding thermal vinylic‐bond rotations followed by cyclizations of conjugated bisallenes to give bismethylene cyclobutenes excludes the alternative HT mechanism (double‐bond isomerization) in the present cases. But space‐conserving HT might be a mechanistic alternative in less‐substituted cases under photoexcitation. The stereochemical consequences are discussed.

show abstract

Structures and photochemical reactions of 1-(9-anthryl)-2-aroylethylenes: competing cis–trans isomerization and skeletal rearrangement

Cited by 19 publications

References 4 publications

Mechanical motion of molecular crystals induced by [4 + 4] photodimerisation

Mechanical motion of molecular crystals induced by [4 + 4] photodimerisation

Volume demanding geometric isomerization of cis-4-stilbazole. HCl salts in the crystalline state: Probing the role of a metastable dimer

Hula-twist Within the Confinement of Molecular Crystals¶

Contact Info

Product

Resources

About