Volume-Demanding Cis<i>−</i>Trans Isomerization of 1,2-Diaryl Olefins in the Solid State

Natarajan, Arunkumar; Mague, Joel T.; Venkatesan, Κ.; Arai, Tatsuo; Ramamurthy, V.

doi:10.1021/jo0520644

Cited by 42 publications

(41 citation statements)

References 22 publications

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“…Many of the reported solid-state reactions involve large molecular motions, which lead to crystal breakdown when conversion percentages exceed 5-10%. 17,18 Such reactions are usually not single-crystalto-single-crystal reactions, even though the external shape of the crystals may be perfectly retained. 19 In protein crystallography in which reactive centers are typically embedded in a protein envelope and much solvent is present, the danger of crystal breakdown initiated by the light-induced process is much less severe or absent, as illustrated by time-resolved and freeze-trapping studies of, for example, the dissociation and recombination of CO in myoglobin, 20 and the photoreaction of photoactive yellow protein.…”

Section: General Considerationsmentioning

confidence: 99%

Supramolecular solids and time-resolved diffraction

et al. 2006

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Supramolecular solids are an ideal medium for time-resolved diffraction studies at atomic resolution as they allow dilution of the active species, and the study of a species in different states of aggregation and different environments, but attention must be paid to excited-state quenching due to energy transfer. Crystallinity must be preserved up to reasonable product concentrations if chemical reactions are to be monitored at the atomic level.

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Section: General Considerationsmentioning

confidence: 99%

Supramolecular solids and time-resolved diffraction

et al. 2006

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“…[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

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Ramamurthy

2016

Journal of Photochemistry and Photobiology A: Chemistry

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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.

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“…F and Cl) (17), (b) templation with host cyclic or cavitand structures (e.g. bis-urea macrocycles, cyclodextrins, Pd nanocages and zeolites) (12,(32)(33)(34)(35)(36)(37)(38)(39) and (c) steering crystallization through hydrogen bonding with a photoinert second molecule (40)(41)(42). For the current presentation the last strategy known as "templation" is of interest and a brief background is provided: In this strategy a chosen template molecule enables the potentially reactive guest molecules to pack in a manner that would facilitate photodimerization -in most examples thus far explored the reactant pair alignment results from hydrogen bonding between the template and the reactant molecules.…”

Section: Introductionmentioning

confidence: 99%

Comparison of Templating Abilities of Urea and Thioruea During Photodimerization of Bipyridylethyelene and Stilbazole Crystals

Bhogala

Captain

Ramamurthy

2014

Photochem & Photobiology

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Photodimerization of cocrystals of four bispyridylethylenes and two stilbazoles with urea as a template in the solid state has been investigated following our success with thiourea. Four investigated olefins photodimerized quantitatively to a single dimer in the crystalline state only. The reactivity of urea-olefin crystals is understood on the basis of their packing arrangements in the crystalline state. In reactive crystals the adjacent reactive molecules are within 4.2 Å and parallel, whereas the unreactive ones have their adjacent molecules are farther than 4.6Å and nonparallel. Thus, with the knowledge of crystal packing the reactivity of urea-olefin crystals is predictable on the basis of Schmidt's topochemical postulates. The templating property of urea, similar to thiourea, derives from its ability to form hydrogen bonds with itself and the guest olefins. Despite the similarities in molecular structures of urea and thiourea their subtle electronic properties, yet to be fully understood, affect the crystal packing and consequently their reactivity in the crystalline state. Further work is needed to fully exploit the templating properties of urea.

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Volume-Demanding Cis−Trans Isomerization of 1,2-Diaryl Olefins in the Solid State

Cited by 42 publications

References 22 publications

Supramolecular solids and time-resolved diffraction

Supramolecular solids and time-resolved diffraction

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

Comparison of Templating Abilities of Urea and Thioruea During Photodimerization of Bipyridylethyelene and Stilbazole Crystals

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