Azobenzene‐Tethered Bis(Trityl Alcohol) as a Photoswitchable Cooperative Acid Catalyst for Morita–Baylis–Hillman Reactions

Imahori, Tatsushi; Yamaguchi, Ryo; Kurihara, Seiji

doi:10.1002/chem.201201383

Cited by 60 publications

(37 citation statements)

References 69 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The synthesis of these three molecules is shown schematically in Figure 1b where, starting from the precursor material, a two-step process was adapted from previous work on the synthesis of compound 1 for catalyst applications. 28 Optical and Thermal Properties of Compound 1. The azobenzene molecule possesses two main absorption features resulting from the π → π* and n → π* transitions (Figure 2a, top).…”

Section: ■ Results and Discussionmentioning

confidence: 99%

Molecularly Engineered Azobenzene Derivatives for High Energy Density Solid-State Solar Thermal Fuels

Cho

Zhitomirsky

Han

et al. 2017

ACS Appl. Mater. Interfaces

101

View full text Add to dashboard Cite

Solar thermal fuels (STFs) harvest and store solar energy in a closed cycle system through conformational change of molecules and can release the energy in the form of heat on demand. With the aim of developing tunable and optimized STFs for solid-state applications, we designed three azobenzene derivatives functionalized with bulky aromatic groups (phenyl, biphenyl, and tert-butyl phenyl groups). In contrast to pristine azobenzene, which crystallizes and makes nonuniform films, the bulky azobenzene derivatives formed uniform amorphous films that can be charged and discharged with light and heat for many cycles. Thermal stability of the films, a critical metric for thermally triggerable STFs, was greatly increased by the bulky functionalization (up to 180°C), and we were able to achieve record high energy density of 135 J/ g for solid-state STFs, over a 30% improvement compared to previous solid-state reports. Furthermore, the chargeability in the solid state was improved, up to 80% charged from 40% charged in previous solid-state reports. Our results point toward molecular engineering as an effective method to increase energy storage in STFs, improve chargeability, and improve the thermal stability of the thin film. KEYWORDS: solar thermal fuels heat storage, molecular thin films, solid-state applications, structural design, molecular engineering, photoswitching ■ INTRODUCTIONDespite the vast abundance of solar radiation, efficient conversion, storage, and distribution of this resource remains a challenge. One approach that uses the same material to both convert and store the sun's energy is the use of photoactive molecules. These molecules convert solar energy into strained or rearranged chemical bonds, with the amount of energy stored, ΔH, as the difference in energy between the ground and metastable states. Upon reversion back to the ground state, the energy is released in the form of heat with the molecules back in their ground state ready to be charged again. These materials for solar energy harvesting, referred to as solar thermal fuels (STF), operate in a closed cycle and ideally possess high energy density and cyclability with no degradation or emissions and easy distribution as "heat on demand".Previous work on candidate solar thermal fuels has shown both promise and many challenges in optimizing the required properties. For example, norbornadiene showed great potential with high energy density (89 kJ/mol). Although cyclability has been the biggest challenge, recent research by molecular modification of norbornedine using aryl substituents showed improvement of cyclability.1−3 Recent work showed that (Fulvalene) tetracarbonyl-diruthenium showed reasonable gravimetric energy density (30.6 Wh/kg) while showing high cyclability, but due to the use of expensive ruthenium, its potential is limited.4,5 Azobenzene possesses high cyclability but has been hindered by low energy density. 6 Recently, several templating methods of the solar thermal fuel molecule have gained attention and have been invest...

show abstract

Section: ■ Results and Discussionmentioning

confidence: 99%

Molecularly Engineered Azobenzene Derivatives for High Energy Density Solid-State Solar Thermal Fuels

Cho

Zhitomirsky

Han

et al. 2017

ACS Appl. Mater. Interfaces

101

View full text Add to dashboard Cite

show abstract

“…18 An azobenzene core was introduced to a bis(trityl alcohol) catalyst, in which the cooperative function of the two acidic trityl alcohol units acquires the catalytic activity, 22 to modulate the cooperative function by the overall conformational changes based on photoisomerization of azobenzene (Figure 8). The azobenzenebis(trityl alcohol) catalyst 12 reversibly changes the structure by external stimuli.…”

Section: 18mentioning

confidence: 99%

“…The closed form (16-closed) induced by irradiation of 313 nm light coordinates with Cu(I) in a monodentate fashion, which provides a loose chiral environment on the copper center. These 16/Cu(I) complexes promoted cyclopropanation of styrene (17) with ethyl diazoacetate (18) 27 in different stereoselectivities (Scheme 5). The reaction with 16-open/Cu(I) provided trans-and ciscyclopropane 19 with moderate enantioselectivities (cis-19: 50% ee, trans-19: 30% ee).…”

Section: 18mentioning

confidence: 99%

Stimuli-responsive Cooperative Catalysts Based on Dynamic Conformational Changes toward Spatiotemporal Control of Chemical Reactions

Imahori

Kurihara

2014

Chemistry Letters

Self Cite

View full text Add to dashboard Cite

show abstract

“…The cavitand features an azobenzene arm capable of competing with the piperidinium ion for the cavity when irradiated with UV light, allowing reversible control of the guest binding and reactivity. Imahori and co‐workers reported a bis(trityl alcohol)‐substituted azobenzene as a cooperative bifunctional switchable catalyst capable of reversible activity control when applied to a Morita–Baylis–Hillman reaction of 3‐phenylpropanal and 2‐cyclopenten‐1‐one . The switchable catalyst was able to increase the yield of the reaction after 2 h (background, 27 %) from 37 %, using the less active state ( E )‐isomer, to 78 % yield using the more active ( Z )‐isomer.…”

Section: Introductionmentioning

confidence: 99%

Bifunctional Molecular Photoswitches Based on Overcrowded Alkenes for Dynamic Control of Catalytic Activity in Michael Addition Reactions

Pizzolato

Collins

Leeuwen

et al. 2017

Chemistry A European J

View full text Add to dashboard Cite

The emerging field of artificial photoswitchable catalysis has recently shown striking examples of functional light-responsive systems allowing for dynamic control of activity and selectivity in organocatalysis and metal-catalysed transformations. While our group has already disclosed systems featuring first generation molecular motors as the switchable central core, a design based on second generation molecular motors is lacking. Here, the syntheses of two bifunctionalised molecular switches based on a photoresponsive tetrasubstituted alkene core are reported. They feature a thiourea substituent as hydrogen-donor moiety in the upper half and a basic dimethylamine group in the lower half. This combination of functional groups offers the possibility for application of these molecules in photoswitchable catalytic processes. The light-responsive central cores were synthesized by a Barton-Kellogg coupling of the prefunctionalized upper and lower halves. Derivatization using Buchwald-Hartwig amination and subsequent introduction of the thiourea substituent afforded the target compounds. Control of catalytic activity in the Michael addition reaction between (E)-3-bromo-β-nitrostyrene and 2,4-pentanedione is achieved upon irradiation of stable-(E) and stable-(Z) isomers of the bifunctional catalyst 1. Both isomers display a decrease in catalytic activity upon irradiation to the metastable state, providing systems with the potential to be applied as ON/OFF catalytic photoswitches.

show abstract

Azobenzene‐Tethered Bis(Trityl Alcohol) as a Photoswitchable Cooperative Acid Catalyst for Morita–Baylis–Hillman Reactions

Cited by 60 publications

References 69 publications

Molecularly Engineered Azobenzene Derivatives for High Energy Density Solid-State Solar Thermal Fuels

Molecularly Engineered Azobenzene Derivatives for High Energy Density Solid-State Solar Thermal Fuels

Stimuli-responsive Cooperative Catalysts Based on Dynamic Conformational Changes toward Spatiotemporal Control of Chemical Reactions

Bifunctional Molecular Photoswitches Based on Overcrowded Alkenes for Dynamic Control of Catalytic Activity in Michael Addition Reactions

Contact Info

Product

Resources

About