Acyclic Azines Research Articles

Fluorescence properties of some substituted acyclic azines

Fluorescence spectra of some acyclic azines (2,3-diazabutadienes), namely ō-hydroxybenzaldizine (1), p̄-N, N-dimethyl-amino abenzaldazine (2) and 2-hydroxy-1-naphthaldazine (3) were determined in different solvents at ambient temperature and at 77 K. The results showed that radiative and nonradiative rates are essentially controlled by the structure of the molecules. The fluorescence of compounds (1)-(3) is enhanced sufficiently by affecting the nπ∗ nature of the S 1 state in different media. The fluorescence quantum yield Φ F increases significantly as the viscosity of the homogeneous medium increases and as the temperature is lowered to 77 K. However, Φ F reaches a limiting small value, indicating the existence of an important nonradiative decay channel involving formation of different rotamers and E-Z isomers. The results of quantum chemical calculations based on the Hückel MO method, show that optical excitation decreases bond alternation in the S 1 state, leading to increasing nonradiative decay. Furthermore, the results demonstrate that the photophysical properties of these compounds in an ionic micellar system (CTAB) differ from analogous properties in homogeneous solitions. Optical excitation of azines containing a hydroxyl group ((1) and (3)) gives rise to a large increase in their acidic properties suggesting that intramolecular proton transfer in these molecules can be switched on by optical excitation. We have focussed our interest on ō-hydroxybenzaldazine (1) since preliminary studies show that it may be a useful indicator for fluorimetric determination of the microproperties of the surrounding environment.

Quantenchemische Untersuchungen zur Farbe und Stereodynamik von acyclischen Azinen. XV. Zum strukturellen Aspekt des Photochromie‐Effektes

Quantum Chemical Studies on Colour and Stereodynamics of Acyclic Azines. XV. On the Structural Aspect of the Photochromic EffectFor the longest‐wavelength colour‐determining electronic transition of selected arylsubstituted acyclic azines the curvature of λ=λ(θcc) has been adapted by means of polynomic and trigonometric functions. On this basis it is possible to discuss the structural aspect of the photochromic and aphotochromic behaviour being observed due to the (E, Z) isomerization.

ChemInform Abstract: QUANTUM CHEMICAL STUDIES ON COLOR AND STEREODYNAMICS OF ACYCLIC AZINES. PART XI. THE MODEL OF THE “CRANK‐SHAFT” MECHANISM FOR (E,Z) ISOMERIZATION OF ARYLSUBSTITUTED ACYCLIC AZINES

Chemischer InformationsdienstVolume 15, Issue 1 Physical Organic Chemistry ChemInform Abstract: QUANTUM CHEMICAL STUDIES ON COLOR AND STEREODYNAMICS OF ACYCLIC AZINES. PART XI. THE MODEL OF THE “CRANK-SHAFT” MECHANISM FOR (E,Z) ISOMERIZATION OF ARYLSUBSTITUTED ACYCLIC AZINES S. VETTERMANN, S. VETTERMANNSearch for more papers by this authorK. GUSTAV, K. GUSTAVSearch for more papers by this authorJ. + JUENGEL, J. + JUENGELSearch for more papers by this author S. VETTERMANN, S. VETTERMANNSearch for more papers by this authorK. GUSTAV, K. GUSTAVSearch for more papers by this authorJ. + JUENGEL, J. + JUENGELSearch for more papers by this author First published: January 3, 1984 https://doi.org/10.1002/chin.198401060Read the full textAboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume15, Issue1January 3, 1984 RelatedInformation

Quantenchemische Untersuchungen zur Farbe und Stereodynamik von acyclischen Azinen. XIV. Zum Chromophorsystem der isomeren Anthraldazine in den niedrigsten Sp(ππ*)‐Zuständen

Quantum Chemical Studies on Colour and Stereodynamics of Acyclic Azines. XIV. On the Chromophoric System of the Isomeric Anthraldazines in the Lowest Sp (ππ*) StatesThe chromophoric system of the isomeric anthraldazines have been studied quantumchemically by means of the PPP‐CA and LHM‐CI methods. On the basis of a definite substructure being in analogy to the molecular geometries the electronic Sp(ππ*) states of the isomers can be characterized through the corresponding configurations. Taking into account these results an interpretation of the electronic absorption spectra is presented. The conclusions with respect to the chromophoric system are generalized for this class of compounds.

Thermochromism and photochromism of aryl-substituted acyclic azines VII: solvent effect on photochemical E-Z isomerization

In the E-Z isomerization of benzophenone-9-anthraldazine and benzophenone-9-acridinealdazine there is a significant relation between φ E → Z and the solvent acceptor number AN, whereas a significant relation between φ Z → E and AN could not be detected. These results are interpreted in terms of the effect of solvent polarity on the energy levels of the E-Z isomers of the azine.

Quantum chemical studies on colour and stereodynamics of acyclic azines: Part XII. Completely-optimized molecular geometries of the isomers of benzaldazine and benzophenone-9-anthraldazine in the S0 and S1 (ππ*) electronic states

The completely-optimized molecular geometries of the isomers of benzaldazine and benzophenone-9-anthraldazine have been calculated for the S 0 and S 1 (ππ*) electronic states by means of the Warshel—Karplus method, taking into account all molecular coordinates as structural variables for the minimization of the total energy. The results obtained are discussed with regard to the electronic spectral behaviour.

Quantum chemical studies on colour and stereodynamics of acyclic azines: Part XI. The model of the “crank-shaft” mechanism for ( E, Z) isomerization of arylsubstituted acyclic azines

A new mechanism called the “crank-shaft” mechanism (“Kurbelwellen”-Mechanismus), based on the concept of motion processes through multiple-coupled structural variables, is proposed for the ( E, Z) isomerization of the arylsubstituted acyclic azines in different media. The mathematical model is presented. The isomerization quantum yields are of a comparable order of magnitude for these compounds and are included in the discussion of the mechanism.

Thermochromism and photochromism of aryl- substituted acyclic azines V: Quenching of the photochemical E Z isomerization via Förster energy transfer

The E Z isomerization of benzophenone-9-anthraldehyde azine is quenched by dyes of appropriate singlet energy. The quenching occurs predominantly via Förster energy transfer. The development of a procedure that allows a distinction to be made between direct and sensitized fluorescence for the case of a non-fluorescing donor (azine) and overlapping donor and acceptor spectra is reported.

Quantum chemical studies on colour and stereodynamics of acyclic azines: Part IX. The coupled NN rotation/N inversion mechanism for the thermal (E,Z) isomerization of benzaldazine

NDDO calculations have been done for the thermal (E,Z) isomerization of benzaldazine, a suitable model compound for aryl substituted acyclic azines. The process considered is a coupled NN rotation/N inversion mechanism. It is composed of an NN rotation followed by an N inversion motion and completed by the NN rotation.

Thermochromism and photochromism of aryl substituted acyclic azines : Uncatalised and acid-catalised thermal isomerisation

The photochemical E- Z isomerisation of the benzophenone-9-anthraldehyde azine ( 1), benzophenone-9-acridine aldehyde azine ( 2) and 9-anthraldehyde azine ( 3) is thermally reversible. The thermal reaction gives the same isomers as the photochemical reaction. We have studied the mechanism of the thermal isomerisation of these azines. Our results are in accordance with an inversion of the N atom which is connected with a rotation movement about the N-N single or the CN double bond.

Thermochromism and photochromism of aryl-substituted acyclic azines II: Photokinetics

Acyclic azines with higher condensed aromatic and heterocyclic substituents are photochromic and show both thermal isomerization and photochemical isomerization. From the point of view of formal kinetics the azines can be divided into four reaction types depending on the substituents R i . The correspondence of the expected formal kinetic behaviour of the azines with the experimental results is a direct proof of a photochemical E– Z isomerization of these compounds. We investigated acyclic azines which fulfil all criteria of a complicated unitary photoreaction of the type A ⇌ B as well as those azines showing a reversible consecutive photoreaction A ⇌ B ⇌ C. All quantum yields were determined using formal kinetics.

Thermochromism and photochromism of aryl-substituted acyclic azines III: Investigations on the mechanism of photochemical isomerization

We studied the reaction mechanism of the unsensitized as well as the sensitized photochemical E— Z and Z— E isomerizations of benzophenone-9-anthraldehyde azine. The photochemistry of this compound follows a unitary E ⇌ Z reaction. For qualitative investigations we used benzophenone-9-acridinealdehyde azine, 9-anthranyl-2-pyridinealdehyde azine, 9-anthranyl-3-quinolinealdehyde azine, 9-anthranyl-9-acridinealdehyde azine and 9-acridinealdehyde azine. The experimental results are consistent with the following mechanism for the photoisomerization of azines. In the photochemical E— Z isomerization the S 1 state of the E isomer is reactive; sensitization of the triplet state does not induce the reaction. A singlet mechanism is also very probable for the Z— E isomerization. The most effective photophysical processes competing with isomerization are intersystem crossing in the E isomer and radiationless internal conversion in the Z isomer.

ChemInform Abstract: QUANTUM CHEMICAL STUDIES ON COLOR AND STEREODYNAMICS OF ACYCLIC AZINES. II. EFFECT OF TWISTED S0 MOLECULAR GEOMETRIES ON THE SPECTRAL BEHAVIOR AND THE PHOTOCHROMIC EFFECT OF BENZ‐ AND ANTHRALDAZINES

Chemischer InformationsdienstVolume 10, Issue 40 Organic Dyes ChemInform Abstract: QUANTUM CHEMICAL STUDIES ON COLOR AND STEREODYNAMICS OF ACYCLIC AZINES. II. EFFECT OF TWISTED S0 MOLECULAR GEOMETRIES ON THE SPECTRAL BEHAVIOR AND THE PHOTOCHROMIC EFFECT OF BENZ- AND ANTHRALDAZINES K. GUSTAV, K. GUSTAVSearch for more papers by this authorS. VETTERMANN, S. VETTERMANNSearch for more papers by this authorI. ROSE, I. ROSESearch for more papers by this author K. GUSTAV, K. GUSTAVSearch for more papers by this authorS. VETTERMANN, S. VETTERMANNSearch for more papers by this authorI. ROSE, I. ROSESearch for more papers by this author First published: October 2, 1979 https://doi.org/10.1002/chin.197940291AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat No abstract is available for this article. Volume10, Issue40October 2, 1979 RelatedInformation

Quantenchemische Untersuchungen zur Farbe und Stereodynamik von acyclischen Azinen. IIZum Einfluß tordierter S0‐Molekülgeometrien auf das Spektralverhalten und den Photochromie‐Effekt des Benz‐ und Anthraldazins

Quantum Chemical Study on Colour and Stereodynamics of Acyclic Azines. II. Influence of Twisted S0 Molecular Geometries on the Spectral Behaviour and the Photochromic Effect of Benz‐ and AnthraldazineOn the basis of quantum chemical calculations the influence of twisted molecular geometries on the spectral behaviour of (1E,3E)‐ and (1E,3Z)‐isomers of benz‐ and anthraldazine has been investigated. It is possible to point out structural peculiarities in the S0 state and to explain the photochromic effect of the arylsubstituted acyclic azines.

The photolysis of acyclic azines and the electronic spectra of R 1 R 2 CN • radicals

Flash photolysis of formaldazine, acetaldazine and dimethylketazine produced three new transient u.v. spectra which have been attributed to the CH 2 N., CH 3 CHN. and (CH 3 ) 2 CN. free radicals. The absolute rate constant for the second-order decay of the CH 2 N • radical has been determined. The pressure dependence of the product quantum yields from the continuous 253.7 nm photolysis of acetaldazine was investigated. The results from these experiments, and a re-interpretation of the data published by Brinton on acetaldazine photolysis, have been used to derive a free radical mechanism which includes several primary reactions, of which NN fission is the major process under all experimental conditions, and a sequence of secondary reactions in which the disproportionation of CH 3 CHN. radicals predominates. The overall mechanism satisfactorily describes the pressure and wavelength dependence of acetaldazine photolysis. Preliminary experiments on formaldazine indicate that the photolysis of the azine proceeds by a very similar mechanism.