Tautomerism of 9-acridinamines substituted at the exocyclic nitrogen atom in view of computational predictions and experimental findings

Wróblewska, Agnieszka; Meszko, Joanna; Krzymiński, Karol; Ebead, Youssif; Błażejowski, Jerzy

doi:10.1016/j.chemphys.2004.06.025

Cited by 9 publications

(3 citation statements)

References 55 publications

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“…The calculations indicate that the ground state has a large contribution of an imine form of the exocyclic nitrogen (N−H) due to the presence of the electron-withdrawing groups. The tautomerism of the 9AA and of its derivatives is well stablished in the literature. , Following this argument, the strong red absorption band in polar solvents would originate from a π-conjugated extended effect because the 9AA moiety has contribution of an imine form. Note that in such tautomeric imine form, the endocyclic N of the acridine ring becames the center of an electron donor group, and the resonance favors a charge-transfer toward the electron withdrawing groups through the vinylene molecular bridge (see Figure below).…”

Section: Resultsmentioning

confidence: 82%

Photoinduced Intramolecular Charge Transfer in 9-Aminoacridinium Derivatives Assisted by Intramolecular H-Bond

Pereira

Gehlen

2006

J. Phys. Chem. A

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Fluorochromic dyes derived from 9-aminoacridinium containing a vinylene function with electron withdrawing groups such as diethyl [(acridinium-9-ylamino)methylene]malonate (I), ethyl [(acridinium-9-ylamino)methylene]cyanoacetate (II), [(acridinium-9-ylamino)methylene]malononitrile (III), are prepared and studied in their monoprotonated form. Absorption spectra of the new dyes are red shifted compared to that of the precursor dye. The observed dual fluorescence and multiexponential decay are ascribed to normal emission from the acridinium chromophore in addition to excited-state intramolecular charge transfer (ESICT) process. However, biexponential decay character is observed only for the dicyano derivative (compound III), whereas for the two other systems, more complex kinetics and a three-component decay is recovered. The analysis of the fluorescence decays in different solvents for the first two compounds reveals two short-lived components in the range of 160-350 ps and 1.1-3.0 ns, related to formation and decay of the ESICT state, plus a third one with decay time of about 9 ns, which is ascribed to the normal emission from the acridinium chromophore as an enol tautomer or as an intramolecular H-bond conformer (closed form tautomer). For the dicyano derivative, in which the absence of carbonyl group precludes the H-bond interaction, the biexponential fitting reveals a slightly fast formation rate of the ESICT state with values on the order of 10(10) s(-1), whereas its decay time is between 0.6 and 3.2 ns, depending on the solvent used.

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Section: Resultsmentioning

confidence: 82%

Photoinduced Intramolecular Charge Transfer in 9-Aminoacridinium Derivatives Assisted by Intramolecular H-Bond

Pereira

Gehlen

2006

J. Phys. Chem. A

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“…Their biological relevance is well established, and 9-aminoacridines are capable of interacting speci®cally with adjacent molecules. The mechanisms of these interactions undoubtedly depend on the form in which the 9-aminoacridines occur (Barbe et al, 1996;Wro Â blewska et al, 2004). The present work was undertaken in order to discover the tautomeric form of compound (I) in the crystalline phase and the crystal structure of its precursor (II).…”

Section: Commentmentioning

confidence: 99%

“…The practically and cognitively interesting 9-aminoacridine molecule has the potential to co-exist, in the liquid and gas phases, in the amine and imine tautomeric forms (Rak et al, 1997), even though it has been established that only the amine tautomer is present in the crystalline phase (Chaudhuri, 1983). It has recently been found that the electron-withdrawing and -donating substituents at the exocyclic N atom have a greater af®nity for, respectively, the imine and amine forms of 9-aminoacridines (Wro Â blewska et al, 2004). Two examples con®rm this rule: molecules of the imine form are present in crystals of 9-(trichloroacetylimino)acridine (Meszko et al, 2002) and 9-(phenylsulfonylimino)acridine (Kuz'mina & Struchkov, 1981), both of which contain strongly electronattracting substituents at the exocyclic N atom (the former compound crystallizes as a monohydrate).…”

Section: Commentmentioning

confidence: 99%

9-(2-Chloroethylamino)acridine monohydrate and its precursor 9-phenoxyacridine

et al. 2005

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The title compounds, C15H13ClN2.H2O, (I), and C19H13NO, (II), form monoclinic crystals. Arranged in a 'head-to-tail' manner, the molecules of the amine form (I) lie along the b axis in layers that are linked by a network of hydrogen bonds involving the endocyclic N atom, the H atom at the exocyclic N atom and all the atoms of the solvent water molecule. Molecules of (II), with the phenoxy group nearly perpendicular to the acridine moiety, are arranged in pairs related by a center of symmetry and stabilized via two C-H...N contacts; the latter are linked via a network of further C-H...N contacts and non-specific dispersive interactions.

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Dependence of the Reactivity of Acridine on Its Substituents: A Computational and Kinetic Study

et al. 2011

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Aromatic nucleophilic substitution on the C9 carbon of acridine plays an important role in multiple biological and medicinal applications. The rate of the key reaction is strongly dependent on the environment and acridine substituents. In this study, the factors influencing the reaction mechanism were studied theoretically and verified experimentally for simplified systems. Density functional theory was used for the computations. The activation energy of a model derivative was determined experimentally from a kinetic study. Also, the relative reactivities of selected compounds were verified by a competition experiment. The theoretical predictions correlate well with the observations. The computed re-

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Tautomerism of 9-acridinamines substituted at the exocyclic nitrogen atom in view of computational predictions and experimental findings

Cited by 9 publications

References 55 publications

Photoinduced Intramolecular Charge Transfer in 9-Aminoacridinium Derivatives Assisted by Intramolecular H-Bond

Photoinduced Intramolecular Charge Transfer in 9-Aminoacridinium Derivatives Assisted by Intramolecular H-Bond

9-(2-Chloroethylamino)acridine monohydrate and its precursor 9-phenoxyacridine

Dependence of the Reactivity of Acridine on Its Substituents: A Computational and Kinetic Study

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