Thermotransformations of chromenoacridines

Gutsulyak, B. M.; Gutsulyak, Kh. V.; Manzhara, V. S.; Melnik, Maksim; Sereda, I. I.

doi:10.1007/bf00661811

Cited by 2 publications

(6 citation statements)

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“…The preceding investigations of dyes showed [17] that the thermochromic properties are displayed by CA at its insertion into a polymer matrix. Along with that, the temperature of transition rises to 60-90 C by depending on the polymer type, while the kinetic characteristics of the transmutation of both forms are slowed down.…”

Section: Ca Thermochromism In Non-oriented Matricesmentioning

confidence: 97%

Processes of Molecular Transformations and Self-Organization of Chromenoacridines in Liquid Crystal Matrices

Gutsulyak

2008

Molecular Crystals and Liquid Crystals

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The thermochromism and the crystallization of bistable chromeno[2,3-q]acridines in liquid crystals are investigated. The dependence of thermochromic properties of the dye and characteristics of the liquid crystal on the dye concentration is revealed.At small concentrations of the dye, the ordering of the LC matrix stimulates the thermotransformations of the dye and reflects in the increase of the transition temperature from the chromene form to the merocyanine form. At large concentrations of the dye the LC matrix ordering hampers the reversal transition from the merocyanine form to the chromene form, and the transition temperature reduces (DT ¼ 80 C).The ordering of the LC matrix impedes the crystallization of the dye and causes both a modification of the form and a decrease of the size of crystals.The influence of the dye on the LC properties is exposed in the modification of physical characteristics of the LC (reduction of the crystallization temperature) and in the oriented influence of the dye on the LC (appearance of the texture).

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Section: Ca Thermochromism In Non-oriented Matricesmentioning

confidence: 97%

Processes of Molecular Transformations and Self-Organization of Chromenoacridines in Liquid Crystal Matrices

Gutsulyak

2008

Molecular Crystals and Liquid Crystals

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“…As stated above, the initial concentration, the incident light intensity, the optical path lengths, and the kinetic traces performed on the reaction medium (monitored by UV–visible spectrophotometry at a constant temperature) usually represent the accessible experimental condition for these systems 1–14. Thermal and photochemical equilibria are reached within reasonable time spans, and the photochemical reaction is undertaken by using continuous irradiation.…”

Section: The Mathematical Formalismmentioning

confidence: 99%

“…From a reaction point of view, a number of these chromic systems can be described by a generic AB(2 k ,1 ϕ) kinetic mechanism 1–14, which consists of opposing thermal steps between the reactive species A and B in addition to a forward photochemical reaction involving the starting material (species A, Scheme ). Of course, the true mechanism will be more complex than that assumed by this generalization, but the other intermediate species (particularly excited states) involved in the overall reaction are characterized by lifetimes several orders of magnitude shorter (<ms) than those of species A and B (in the order of seconds/minutes) 2–4.…”

Section: Introductionmentioning

confidence: 99%

“…The elucidation approaches proposed, thus far, to solve such kinetics have necessarily involved independent estimation of the effective values of at least one of the unknown parameters, besides considering (or assuming) that the spectrum of the initial species is accessible 1–14. For example, to determine the thermal equilibrium constant ( K e = k AB / k BA ) at a given temperature, the spectrum of B has been estimated by undertaking measurements at low temperature (−75°C) 11, by using iterative methods 12,13, or by the total protonation of the charged species (open form isomers) 14. However, the estimated values were always approximate, especially because the spectrum of species A was not known with certainty.…”

Section: Introductionmentioning

confidence: 99%

“…For spiropyrans, spirooxazines, Schiff's bases, and bianthrones the same species B structure is generated through the pure thermal and photochemical processes 1–4. The photobleaching reaction quantum yield (ϕ BA ) of such systems is usually neglected 1–14.…”

Section: Introductionmentioning

confidence: 99%

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A mathematical analysis and elucidation of AB(2k,1ϕ) thermophotochromic kinetics: Analytical solutions using pure kinetic data and considering as unknown the rate constants, quantum yield, and both species' spectra

Maafi

Brown

2008

Int J of Chemical Kinetics

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A new spectrokinetic method is described that determines the absolute values of all five unknown parameters (ε A , ε B , φ AB , k AB , k BA ) of AB(2k,1φ) thermophotoreactive chromic systems. For the first time, solely kinetic data are used to perform complete analytical elucidations. Also, the method addresses realistic situations by considering that both absorption spectra of the reactive species are unknown and partially or totally overlap, solving the identifiability problem, and using a single set of experimental data (for the thermal and photochemical reactions). The absolute values for the five unknown parameters that make up the true kinetic solution are readily obtained by the application of five analytically defined algebraic equations. The method is independent of experimental conditions relating to initial concentration, temperature, threshold of incident light intensity, and the wavelength at which the kinetic traces are measured. The detailed mathematical algorithm also allows the determination of the reaction quantum yield at any (isosbestic and nonisosbestic) irradiation wavelength and proposes a new colorability expression for these systems.

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Thermotransformations of chromenoacridines

Cited by 2 publications

References 0 publications

Processes of Molecular Transformations and Self-Organization of Chromenoacridines in Liquid Crystal Matrices

Processes of Molecular Transformations and Self-Organization of Chromenoacridines in Liquid Crystal Matrices

A mathematical analysis and elucidation of AB(2k,1ϕ) thermophotochromic kinetics: Analytical solutions using pure kinetic data and considering as unknown the rate constants, quantum yield, and both species' spectra

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