Cyclodextrin effects on the photochromism of spiropyrans/β-cyclodextrin inclusion polymers

Wang, Lifen; Chen, Jyun-Wei; Chen, Jyun-Wun

doi:10.1016/j.matchemphys.2012.06.045

Cited by 15 publications

(2 citation statements)

References 47 publications

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“…Spiropyrans are an interesting class of photochromic molecules because the colorless and colored isomers have quite different structures. The colorless “spiropyran” isomer (SP) has a compact nonplanar structure, whereas the colored “merocyanine” isomer (MC) has an extended planar structure. , Because of this structural difference, placing spiropyrans in a rigid environment slows SP ↔ MC interconversion. − One such example involves incorporating a spiropyran within the cavity of a cyclodextrin (CD) capsule. − …”

Section: Introductionmentioning

confidence: 99%

Electron Injection and Energy-Transfer Properties of Spiropyran–Cyclodextrin Complexes Coated onto Metal Oxide Nanoparticles: Toward Photochromic Light Harvesting

Dryza

Bieske

2015

J. Phys. Chem. C

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The photochromic and spectroscopic properties of spiropyran−γ-cyclodextrin inclusion complexes coated onto the surface of zirconia and titania nanoparticles (NPs) are examined. After ultraviolet (UV) irradiation, the colorless spiropyran (SP) isomer contained within the cyclodextrin (CD) is converted to the colored merocyanine (MC) isomer, which absorbs light in the 400−600 nm region. A significant increase in the excited-state lifetime for MC-CD on zirconia NPs (τ MC = 1.32 ns) is observed compared to MC in solution (τ MC = 0.21 ns), indicating that MC → SP photoisomerisation is hindered by the surrounding CD. Excitation of MC-CD on titania NPs results in electron injection into the titania conduction band with a quantum yield of 0.70. Excitation of MC-CD on zirconia NPs when a squaraine-based dye sensitizer is also attached to the NP surface results in energy transfer to the dye sensitizer with a quantum yield of 0.65. The prolonged excited-state lifetime of the encapsulated MC-CD is responsible for the high electron injection and energy-transfer quantum yields. The SP-CD/MC-CD system has potential applications for photochromic, light-harvesting electrodes in dye-sensitized solar cells.

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Section: Introductionmentioning

confidence: 99%

Electron Injection and Energy-Transfer Properties of Spiropyran–Cyclodextrin Complexes Coated onto Metal Oxide Nanoparticles: Toward Photochromic Light Harvesting

Dryza

Bieske

2015

J. Phys. Chem. C

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“…Upon addition of the CDs, the rate constants decrease to 0.37-0.22 times that of MCH1, further supporting that CDs can stabilize the SP1 form using the hydrophobic cavity. [50] At 290 K, the two plots of relaxation data in the absence and presence of α-CD (8.00 mM) were almost parallel (Figure S7c), indicating that α-CD has negligible effect on the reaction rate. This is consistent with the conclusion that α-CD cannot form stable enough inclusion complexes with MCH1.…”

Section: Kinetics Of the Thermal Relaxation After Irradiationmentioning

confidence: 86%

Inclusion Complexes of a Metastable‐State Photoacid with High Acidity and Chemical Stability

et al. 2023

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Metastable‐state merocyanine photoacids (MCHs) have been widely applied to various chemical, material and biomedical areas to drive or control chemical processes with light. In this work, stoichiometry and association constants have been determined for inclusion complexes of a photoacid MCH1 with β‐cyclodextrin (β‐CD), 2‐hydroxypropyl‐β‐CD (HP‐β‐CD), γ‐CD and HP‐γ‐CD by means of UV‐Vis absorption titrations. The inclusion complexes were studied to enhance its acidity and chemical stability. Kinetic study showed that CDs stabilized the acidic metastable‐state and slowed its thermal relaxation. The acidity of the ground and metastable‐state (pKaGS and pKaMS) increased upon addition of CDs. The pKaMS of [MCH1·(γ‐CD)2] is as low as 0.92 in comparison with 2.25 for MCH1, which is close to the lowest pKaMS values (1.20 and 1.03) reported previously, in which case the MCH1 was structurally modified with alkylammonium side chains. Addition of CDs also significantly enhanced the chemical stability of MCH1 against hydrolysis, which is one of the major concerns for the application of MCHs. In particular, the addition of HP‐β‐CD increased the half‐life of MCH1 in aqueous solution by more than four times. Moreover, the quantum chemical calculations confirmed the stoichiometry and analyzed the binding sites and hydrogen bonds of the inclusion complexes.

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A Supramolecule‐Triggered Mechanochromic Switch of Cyclodextrin‐Jacketed Rhodamine and Spiropyran Derivatives

Wan

Chen

et al. 2015

Adv Funct Materials

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An innovative approach for covalent-bond-activated mechanoresponse by complexing rhodamine or spiropyran with cyclodextrin (CD) is reported. This approach endows diverse fl uorophores with perfect mechanochromism by introducing a supramolecular system. Unique characteristics such as noncovalent chemical modifi cation and convenient preparation make this approach promising for practical applications. The strong hydrogen bonds provided by CD play a crucial role in triggering the mechanochromic switch. First, the hydrogen bonds seize both sides of the fl uorophore's weak chemical bonds and tightly lock the fl uorophore in the cavity of CD. Second, the hydrogen bonds prompt the aggregation of complex inclusions in large ordered arrays and strengthen the molecular interactions. In this way, the weak chemical bonds can focus more external force and stretch more easily upon shearing (quantifi ed). This is the fi rst report of supramolecule-triggered mechanochromic switches. This study opens an avenue to correlate a mechanochemical reaction with a supramolecular system. [ 3 ] In recent years, the latter approach is appealing to more researchers due to the good color stability and signifi cant color transformation. [ 3d ] Reported achievements of the activation of mechanoresponsive molecules by covalent bonds can be summarized into two classifi cations. The fi rst is covalently modifying the molecules, especially with numerous hetero atoms, to facilitate the interactions such as hydrogen bonds, π-π stacking, and van der Waals force between molecules. These covalent chemical modifi cations require complicated syntheses. Moreover, although some molecules are elaborately modifi ed, a high (nonquantifi ed) external force is still needed to trigger the mechanochromic switches. [ 3d ] The second is the crystallization of solid molecules. [ 4 ] Without the need for chemical modifi cations, this approach is relatively convenient, but the crystallization of solid is constrained by numerous environmental and structural effects. A lot of effort will be taken in preparing the crystalline solid, thus complicating the strategy and limiting the application. Herein, we report an innovative approach for the covalentbond-activated mechanoresponsive molecules. The approach is characterized by noncovalent chemical modifi cation, low external force (0.7 kg for rhodamine-β cyclodextrin ( Rh-βCD ), 2.2 kg for spiropyran-β cyclodextrin ( SP-γ CD )) requirement, and convenient preparation. DOIMotivated by the previous fi ndings that CD can act as a host to interact with guest molecules, we introduce CD as a matrix in our mechanochromic research. CD is well-known for its capability of forming complex inclusions with small molecules. [ 5 ] The hydroxyl groups of CD form strong hydrogen bonds to induce host-guest interactions to stabilize the inclusion complex. [ 5c , 6 ] These excellent interactions are the basic elements for mechanochromism. These interactions, along with the easy strategy affording the inclusion, prompted us to use CD fo...

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Cyclodextrin effects on the photochromism of spiropyrans/β-cyclodextrin inclusion polymers

Cited by 15 publications

References 47 publications

Electron Injection and Energy-Transfer Properties of Spiropyran–Cyclodextrin Complexes Coated onto Metal Oxide Nanoparticles: Toward Photochromic Light Harvesting

Electron Injection and Energy-Transfer Properties of Spiropyran–Cyclodextrin Complexes Coated onto Metal Oxide Nanoparticles: Toward Photochromic Light Harvesting

Inclusion Complexes of a Metastable‐State Photoacid with High Acidity and Chemical Stability

A Supramolecule‐Triggered Mechanochromic Switch of Cyclodextrin‐Jacketed Rhodamine and Spiropyran Derivatives

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