Quantum-chemical interpretation of electronic absorption spectra of the Hantzsch 1,4-dihydropyridines

Kurfürst, Antonín; Kuthan, J.

doi:10.1135/cccc19831422

Cited by 7 publications

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“…The hypsochromic shift observed in the absorption range 320-420 nm has been assigned to the → * electronic transition in the dihydropyridine ring, while the hyperchromic effect in the 259-320 nm range is ascribed to the → * electronic transitions in the aromatic ring [11]. The latter may also involve an underlying → * transition of the dihydropyridine in agreement with the spectral contribution of each chromophore to the overall NIS electronic spectrum [17].…”

Section: Photodegradation Of Nissupporting

confidence: 54%

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Quantification of Unimolecular Photoreaction Kinetics: Determination of Quantum Yields and Development of Actinometers—The Photodegradation Case of Cardiovascular Drug Nisoldipine

Maafi

2015

International Journal of Photoenergy

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The lack of integrated rate-laws for photoreactions has led to carry out the treatment of drugs photodegradation kinetic data using the classical zeroth-, first-, and second-order kinetics that were originally developed for thermal reactions. The recent developments of Φ-order kinetic models has opened new perspectives in the treatment of photoreaction kinetics of systems involving a photolabile molecule (A) transforming into a photochemically and thermally stable product (B), that is, the AB(1Φ) photoreaction systems. Within this framework, the kinetics of cardiovascular and photosensitive drug nisoldipine (NIS) has been rationalised. Continuous and monochromatic irradiation of NIS in ethanol obeyed Φ-order kinetics with a sigmoid-shaped quantum yield variation with irradiation wavelength (0.0041–0.35 within 235–390 nm spectral region). Both NIS initial concentration-induced self-photostabilisation effect and the photostabilisation by absorption competitors were quantified (up 70%) and related to a reduction of the photokinetic factor. Finally, the Φ-order kinetics also served to demonstrate the actinometric potential of NIS for the 320–400 nm dynamic range.

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Section: Photodegradation Of Nissupporting

confidence: 54%

“…NIS spectrum may be interpreted by the contribution of the independent absorptions of the nitrobenzene and the dihydropyridine chromophores. The long wavelength band (300-420 nm) belongs exclusively to the latter molecular moiety, whereas both chromophores input the UVB transition [17].…”

Section: Photodegradation Of Nismentioning

confidence: 99%

Quantification of Unimolecular Photoreaction Kinetics: Determination of Quantum Yields and Development of Actinometers—The Photodegradation Case of Cardiovascular Drug Nisoldipine

Maafi

2015

International Journal of Photoenergy

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“…Introduction of the phenyl group in position 4 as the second chromophore is not expected to involve a major π interaction with the dihydropyridine moiety, in view of the large angle they form . Indeed, as already remarked by Kurfürst, the absorption spectrum of 4-phenyl derivative 16 (PyH 2 -Ph) roughly corresponds to the sum of the spectrum of 15 and of that of benzene. Compound 16 exhibits the same temperature-dependent fluorescence as 15 with an identical shape of the spectrum (see Figure and Table ).…”

Section: Discussionmentioning

confidence: 90%

Intramolecular Electron Transfer in the Photochemistry of Some Nitrophenyldihydropyridines

et al. 2006

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4-Phenyl-1,4-dihydropyridine-3,5-dicarboxylates contain two pi chromophores separated by an sp3 carbon. The lowest singlet is localized on the dihydropyridine moiety (1PyH2-Ph) and emits a blue fluorescence (with close to unitary efficiency in glass at 77 K). In 3-nitrophenyl derivatives (PyH2-PhNO2, some of which are photolabile drugs) the fluorescence is completely quenched. Reasonably, this is due to intramolecular electron transfer between the close-lying donor and acceptor moieties to give the charge-separated species (PyH2*+-PhNO2*-). In EPA glass at 77 K, back-electron transfer gives the dihydropyridine-localized triplet (3PyH2-PhNO2), which emits a yellow phosphorescence. In solution, deprotonation from the radical cation on the dihydropyridine moiety initiates rearomatization, finally giving Py-PhNO2 with low quantum yield (5 x 10(-4) to 5 x 10(-3), increasing up to 0.013 by irradiation at 254 nm, where direct excitation of the nitrophenyl chromophore contributes). In the presence of triethylamine, the reaction changes to neat reduction of the nitro group. When a tethered alkylamino group is present, oxidative degradation of that moiety occurs, again via an electron-transfer intramolecular process. This has been found with the drug nicardipine, where photodegration is more efficient (phi 0.02 to 0.1). Donor-acceptor dyads of this type, easily available through the Hantzsch synthesis, may be useful for building new photoinduced electron-transfer systems.

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“…The broad long-wavelength band ( > 300 nm) belongs to the dihydropyridine chromophore (Krufurst and Kuhan, 1983) which undergoes aromatisation during the photoreaction (Scheme 1). The disappearance of this band is concomitant with the appearance of a series of new peaks between 200 and 300 nm.…”

Section: Discussionmentioning

confidence: 99%

Modelling nifedipine photodegradation, photostability and actinometric properties

Maafi

2013

International Journal of Pharmaceutics

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Quantum-chemical interpretation of electronic absorption spectra of the Hantzsch 1,4-dihydropyridines

Abstract: Electronic absorption spectra of 1,4-dihydropyridines I-XII have been interpreted by means of the SCF-PPP method. Possibility of interpretation of the said spectra of 4-substituted derivatives V-XII as superposition of two independent chromophoric systems is discussed.

Cited by 7 publications

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Quantification of Unimolecular Photoreaction Kinetics: Determination of Quantum Yields and Development of Actinometers—The Photodegradation Case of Cardiovascular Drug Nisoldipine

Quantification of Unimolecular Photoreaction Kinetics: Determination of Quantum Yields and Development of Actinometers—The Photodegradation Case of Cardiovascular Drug Nisoldipine

Intramolecular Electron Transfer in the Photochemistry of Some Nitrophenyldihydropyridines

Modelling nifedipine photodegradation, photostability and actinometric properties

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