Thiourea as a Template for Photodimerization of Azastilbenes

Bhogala, Balakrishna R.; Captain, Burjor; Parthasarathy, Anand; Ramamurthy, V.

doi:10.1021/ja105166d

Cited by 140 publications

(80 citation statements)

References 85 publications

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“…Packing arrangements of 4,4′ BPE (a), 4‐cyanostilbazole (b), 2,4′‐ BPE (c), 4‐chlorostilbazole (d), 2,2′‐ BPE (e) and 2,3′‐ BPE (f) in cocrystals with thiourea .…”

Section: Resultsmentioning

confidence: 99%

“…Therefore, the solid state, restricting the geometric isomerization, has been the medium of choice to carry out photocycloaddition. This article dealing with photocycloaddition of pyridyl (mono and bis) ethylenes in the crystalline state is a continuation of our recent reports wherein we disclosed the use of thiourea and water‐chloride ion composite as templates to orient mono (or bis) pyridyl ethylenes.…”

Section: Introductionmentioning

confidence: 87%

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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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“…Packing arrangements of 4,4′ BPE (a), 4‐cyanostilbazole (b), 2,4′‐ BPE (c), 4‐chlorostilbazole (d), 2,2′‐ BPE (e) and 2,3′‐ BPE (f) in cocrystals with thiourea .…”

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 87%

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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“…Unfortunately, as described here, efforts to design crystals in this manner can be frustratingly unfruitful, and it may prove that templating techniques are more versatile in their application and hence more useful. 59 For recent overviews of crystal engineering and [2 + 2] photocycloadditions see the reviews by Natarajan, Biradha, and Elacqua. 18,54,55 …”

Section: Discussionmentioning

confidence: 99%

π–π Interaction Energies as Determinants of the Photodimerization of Mono-, Di-, and Triazastilbenes

2014

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We describe the quantitative [2 + 2] photocycloaddition of crystalline trans-2,4-dichloro-6-styrylpyrimidine to produce the corresponding htt r-ctt cyclobutane dimer, and we present 1H NMR analysis of the photolysis of this and six other mono-, di-, and triazastilbenes in solid and solution states. Density functional (M06-2X) and correlated ab initio (MP2) calculations were used to obtain interaction energies between two monomers of each azastilbene. These energies mirror the relative polarization of the stilbene moieties and can be quantitatively correlated with the rate of reaction and selective formation of the htt r-ctt dimers. In the solid state, poor correlation is observed between interaction energy and reactivity/selectivity. This lack of correlation is explained through X-ray analysis of the azastilbene monomers and is shown to be in accordance with the principles of Schmidt’s topochemical postulate. Conversely, in solution there is a strong positive correlation (R2 = 0.96) between interaction energies and formation of the htt r-ctt dimer. These results are the first to show this correlation and to demonstrate the utility of calculated interaction energies as a tool for the prediction of stereo- and regioselectivity in solution-state stilbene-type photocycloadditions.

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“…Resorcinol and its derivatives have been the most used linear template. Addition to this, using the concepts of supramolecular synthon, a library of hydrogen bonding templates has been engineered (Scheme 3.11), including 1,8-naphthalenedicarboxylic acid (1,8-nap) [100], 2,3-bis(4-methylenethiopyridyl)naphthalene (2,3-nap) [101], Rebek's imide (Reb-im) [102], thiourea (TU) [103], and a photoproduct rctt-cyclobutanetetracarboxylic acid (cbta) [104].…”

Section: Auxiliary Templatesmentioning

confidence: 99%

Hydrogen Bonding in Supramolecular Crystal Engineering

Wang

Zheng

2015

Lecture Notes in Chemistry

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This chapter emphases the important role of hydrogen bonding in crystal engineering for preparing fascinating architectures and engineering desired properties. The relatively high directionality and strength of hydrogen bonds make the prediction and control of molecular orientation in organic solids practical and reliable. Especially, strong hydrogen bonds like O-H···O, O-H···N, and N-H···O interactions are more useful. The introduction of supramolecular synthons and retrosynthesis theory has helped crystal chemists a lot in understanding and designing more complex structures. A large number of crystal structures reported in Cambridge Structure Database (CSD) provided a helpful tool for searching and analyzing specific interaction modes. Up to now, with the development of basic concepts and principles and the wide applications, the subject of crystal engineering has matured. Various intriguing structures and complicated entanglements have been constructed based on hydrogen bonds, such as nanocapsules, nanotubes, and n-Borromean arrayed topologies. The crystal engineering strategy has lent chemists the ability to control solid state reactions regio-and stereo-specifically and improve the physicochemical properties of drugs using pharmaceutical cocrystals. In addition, it will be seen that hydrogen bonding can also be used to prepare robust porous materials for gas adsorption and separation.

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Thiourea as a Template for Photodimerization of Azastilbenes

Cited by 140 publications

References 85 publications

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

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

π–π Interaction Energies as Determinants of the Photodimerization of Mono-, Di-, and Triazastilbenes

Hydrogen Bonding in Supramolecular Crystal Engineering

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