Resolution and circular dichroism of a non-activated spiropyran dye: 6-(p-Chlorophenylazo)-1′,3′,3′-trimethylspiro[2H-1-benzopyran-2,2′-indoline]

Keum, Sam‐Rok; Lee, Myung-Jin; Swansburg, Susan; Buncel, Erwin; Lemieux, Robert P.

doi:10.1016/s0143-7208(98)00018-7

Cited by 12 publications

(5 citation statements)

References 9 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…However, much less attention has been paid to spiropyrans lacking a strong electron-withdrawing group because they tend to produce photostationary states with a negligible merocyanine concentration . These so-called non activated spiropyrans have rather limited use in photochromic applications, but they have been under consideration as potential chiroptical switches for optically addressed liquid crystal spatial light modulators 1 …”

Section: Introductionmentioning

confidence: 99%

“…Switching is achieved by reversible photoisomerization between the spiropyran form, which exhibits circular dichroism as a 1.6:1 mixture of two diastereomers at equilibrium, and the planar merocyanine form, which exhibits no circular dichroism . We are currently investigating an alternative approach toward a spiropyran chiroptical switch which consists of photoresolving a nonactivated liquid crystalline spiropyran using circularly polarized light to reversibly induce detectable chiral bulk properties such as a cholesteric helical pitch or a spontaneous polarization. , To undergo photoresolution, a chiral chromophore must undergo efficient photoracemization, yet maintain its configurational integrity in the absence of light . Photoracemization can be achieved with nonactivated spiropyrans because the chiral spiro form undergoes ring opening to a short-lived prochiral merocyanine form which reverts back to the ( R ) or ( S ) enantiomers of the spiro form with equal probabilities.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, we reported the synthesis and characterization of a spiropyran derivative ( 4 ) which forms monotropic nematic, smectic A, and smectic C liquid crystal phases 5a. Compound 4 was resolved by chiral phase HPLC but it could not be used as a liquid crystal chiroptical switch, or as a chiral dopant in liquid crystal hosts, due to its configurational instability.…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Thermal Racemization of Substituted Indolinobenzospiropyrans: Evidence of Competing Polar and Nonpolar Mechanisms

2000

Self Cite

View full text Add to dashboard Cite

A series of 6-substituted indolinobenzospiropyrans were resolved by chiral stationary phase HPLC and rate constants k rac for their thermal racemization were measured by circular dichroism spectropolarimetry at 60 °C in three different solvents: cyclohexane, 90:10 hexanes/2-propanol, and acetonitrile. Results show that the spiropyrans undergo thermal racemization most rapidly in acetonitrile, with k rac values ranging from 9.3 × 10 -5 to >5.0 × 10 -3 s -1 , and least rapidly in cyclohexane, with k rac values ranging from 6.8 × 10 -6 to 4.6 × 10 -4 s -1 . V-shaped plots of log k rac vs Hammett σ p constants in 90:10 hexanes/2-propanol and acetonitrile suggest that thermal racemization of the 6-substituted spiropyrans proceed via two competing mechanisms: a polar mechanism involving heterolytic C(sp 3 )-O bond cleavage with anchimeric assistance from the indoline nitrogen and a nonpolar electrocyclic ring opening mechanism with no anchimeric assistance from the indoline nitrogen. The outcome of this competition appears to be strongly influenced by solvent polarity: plots of log k rac vs σ p and σin cyclohexane show a near-linear correlation with negative slope, which is consistent with the nonpolar mechanism. However, an increase in solvent polarity results in a shift toward a linear correlation with positive slope, which is consistent with the polar mechanism.

show abstract

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Thermal Racemization of Substituted Indolinobenzospiropyrans: Evidence of Competing Polar and Nonpolar Mechanisms

2000

Self Cite

View full text Add to dashboard Cite

show abstract

“…Such a high molar absorption coefficient improves the sensitivity and contradistinction between the two ON (MC) and OFF (SP) levels of finely photoresponsive molecules. Previous to that study, there were only a few studies on using an azo chromophore as a part of photochromic spiropyran molecule . Hence, there is a lack of systematic study on azospiropyrans aimed at taking advantage of the electron‐withdrawing character of phenylazo moiety to lower the energy state of the MC form and deepening the color of the solution at the photostationary state by extending the conjugation system.…”

Section: Introductionmentioning

confidence: 99%

Sensitivity and Resolution Development of Spiropyran‐based Molecular Photoswitches

Heydaripour

Nourmohammadian

Saadatjoo

2016

J Chinese Chemical Soc

View full text Add to dashboard Cite

The phenylazo moiety and its donor‐ and acceptor‐substituted derivatives are studied as effective auxochromes to improve their sensitivity and resolution for distinguishing between the spiro (SP; OFF) and mero (ON) forms in molecular photoswitching applications. Thus, 13 azospiropyran derivatives were synthesized and their spectroscopic and photokinetic behaviors were studied. The quality of photochromic reactions of the synthesized photochromic compounds were compared using a dose–response model. Interestingly, by replacing the nitro group in 6‐nitrospiropyran (ε = 0.42 × 104 M−1 cm−1) with a simple phenylazo moiety, the SP form is still colorless and the color intensity of the merocyanine (MC) form is improved desirably by extending the conjugation length (1a, ε = 1.35 × 104 M−1 cm−1). The presence of a hydrophilic OH group or a CH3 group at the para position of phenylazo moiety revealed more or less the same photochromic properties as 1a. The OCH3 group substituted at position 6 of the phenylazo moiety at the para position of the azobenzene moiety effectively increased the photochromic properties with the maximum k‐value for SP to MC switching. Meanwhile, Cl, Br, COOH, and NO2 groups at the para position of the azobenzene moiety revealed the reduction in photochromic properties compared to 1a.

show abstract

“…This has led to studies aimed at stabilization of the MC form . To this end, in our laboratory, we have chosen to variously manipulate the system through acid−base equilibria (acidochromic modulation), metal ion coordination to Lewis base centers, , as well as structural modification (e.g., chelating carboxylate modification). − We, among other groups, , have also been involved in incorporating SP−MC photoswitches into novel media, including liquid crystal phases and most recently as attachments to microparticles …”

Section: Introductionmentioning

confidence: 99%

Spirooxazine to Merooxazine Interconversion in the Presence and Absence of Zinc: Approach to a Bistable Photochemical Switch

et al. 2010

Self Cite

View full text Add to dashboard Cite

A spironaphthoxazine (SO) photoswitch was synthesized, and its photochromic behaviors were investigated. SO underwent reversible ring-opening/closure isomerization between a spirocyclic isomer (closed form) and a merocyanine (MO isomer, open form) upon ultraviolet light irradiation. For the model SO in this work, the thermal equilibrium is substantially shifted toward the spirocyclic isomer even at -30.0 °C. However, addition of zinc, as Zn(ClO(4))(2), exerted an important effect on the thermal reversion process from the open (MO) to the closed form (SO). Kinetic analysis showed that thermal reversion with zinc is retarded more than 13-fold, significantly improving bistability. Moreover, introduction of zinc to the spirooxazine-merooxazine (SO-MO) system resulted in a new absorption band readily distinguishable from the bands arising from spirooxazine and merooxazine. For the first time, to the best of our knowledge, the microscopic rate constants for: MO photogeneration from SO (k(1)), thermal reversion of MO to SO (k(2)), complexation of MO with zinc (k(3)) and for dissociation of the complex, MO-Zn (k(4)), as well as for the ionization equilibria of Zn(ClO(4))(2) have been evaluated. The preferred transoid structures of MO and those of MO-Zn derived from the preferred MO structures are considered. Although the kinetic study does not permit elucidation of the nature of zinc binding to MO to give MO-Zn, nor the precursor isomers of MO, a DFT calculational study in progress should shed light on the structure and relative stability of these essential intermediates.

show abstract

Resolution and circular dichroism of a non-activated spiropyran dye: 6-(p-Chlorophenylazo)-1′,3′,3′-trimethylspiro[2H-1-benzopyran-2,2′-indoline]

Cited by 12 publications

References 9 publications

Thermal Racemization of Substituted Indolinobenzospiropyrans: Evidence of Competing Polar and Nonpolar Mechanisms

Thermal Racemization of Substituted Indolinobenzospiropyrans: Evidence of Competing Polar and Nonpolar Mechanisms

Sensitivity and Resolution Development of Spiropyran‐based Molecular Photoswitches

Spirooxazine to Merooxazine Interconversion in the Presence and Absence of Zinc: Approach to a Bistable Photochemical Switch

Contact Info

Product

Resources

About