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2495 KiB

Open AccessArticle

Photochemistry of 1,4-Dihydropyridine Derivatives: Diradical Formation, Delocalization and Trapping as a Route to Novel Tricyclic and Tetracyclic Nitrogen Heterocyclic Ring Systems

by Nader A. Al-Jalal, Yehia A. Ibrahim, Nouria A. Al-Awadi, Maher R. Ibrahim and Osama M. Sayed

Molecules 2016, 21(7), 866; https://doi.org/10.3390/molecules21070866 - 30 Jun 2016

Cited by 6 | Viewed by 5177

Abstract

Irradiation of an acetonitrile solution of 4-aryl-3,5-dibenzoyl-1,4-dihydropyridine derivatives 1a–c and maleimides 2a–c using medium pressure Hg-arc lamp (λ > 290) nm afforded three different cycloadducts 4, 5, 6 in addition to the oxidation products 3. These [...] Read more.

Irradiation of an acetonitrile solution of 4-aryl-3,5-dibenzoyl-1,4-dihydropyridine derivatives 1a–c and maleimides 2a–c using medium pressure Hg-arc lamp (λ > 290) nm afforded three different cycloadducts 4, 5, 6 in addition to the oxidation products 3. These results indicate that compounds 1a–c undergoes intermolecular cycloaddition reaction through three biradical intermediates and behave photochemically different than those reported previously for the analogous 3,5-diacetyl and 3,5-dicarboxylic acid derivatives. The present work also offers simple access to novel tricyclic and tetracyclic nitrogen heterocyclic ring systems of potential biological and synthetic applications. The structure of the photoproducts was established spectroscopically and by single crystal X-ray crystallography. Full article

(This article belongs to the Special Issue Photoactive Molecules)

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4297 KiB

Open AccessArticle

A Novel Photosensitizer 3¹,13¹-phenylhydrazine -Mppa (BPHM) and Its in Vitro Photodynamic Therapy against HeLa Cells

by Wenting Li, Guanghui Tan, Jianjun Cheng, Lishuang Zhao, Zhiqiang Wang and Yingxue Jin

Molecules 2016, 21(5), 558; https://doi.org/10.3390/molecules21050558 - 29 Apr 2016

Cited by 13 | Viewed by 5735

Abstract

Photodynamic therapy (PDT) has attracted widespread attention due to its potential in the treatment of various cancers. Porphyrinic pyropheophorbide-a (PPa) has been shown to be a potent photosensitizer in PDT experiments. In this paper, a C-3¹,13¹ bisphenylhydrazone modified methyl pyropheophorbide-a [...] Read more.

Photodynamic therapy (PDT) has attracted widespread attention due to its potential in the treatment of various cancers. Porphyrinic pyropheophorbide-a (PPa) has been shown to be a potent photosensitizer in PDT experiments. In this paper, a C-3¹,13¹ bisphenylhydrazone modified methyl pyropheophorbide-a (BPHM) was designed and synthesized with the consideration that phenylhydrazone structure may extend absorption wavelength of methyl pyro-pheophorbide-a (Mppa), and make the photosensitizer potential in deep tumor treatment. The synthesis, spectral properties and in vitro photodynamic therapy (PDT) against human HeLa cervical cancer cell line was studied. Methyl thiazolyl tetrazolium (MTT) assay showed the title compound could achieve strong inhibition of cervical cancer cell viability under visible light (675 nm, 25 J/cm²). Cell uptake experiments were performed on HeLa cells. Morphological changes were examined and analyzed by fluorescent inverted microscope. In addition, the mechanism of the photochemical processes of PDT was investigated, which showed that the formation of singlet oxygen after treatment with PDT played a moderate important role. Full article

(This article belongs to the Special Issue Photoactive Molecules)

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5851 KiB

Open AccessArticle

Conformational and Molecular Structures of α,β-Unsaturated Acrylonitrile Derivatives: Photophysical Properties and Their Frontier Orbitals

by María Judith Percino, Margarita Cerón, Oscar Rodríguez, Guillermo Soriano-Moro, María Eugenia Castro, Víctor M. Chapela, Maxime A. Siegler and Enrique Pérez-Gutiérrez

Molecules 2016, 21(4), 389; https://doi.org/10.3390/molecules21040389 - 28 Mar 2016

Cited by 14 | Viewed by 6477

Abstract

We report single crystal X-ray diffraction (hereafter, SCXRD) analyses of derivatives featuring the electron-donor N-ethylcarbazole or the (4-diphenylamino)phenyl moieties associated with a -CN group attached to a double bond. The compounds are (2Z)-3-(4-(diphenylamino)-phenyl)-2-(pyridin-3-yl)prop-2-enenitrile (I), (2Z)-3-(4-(diphenylamino)phenyl)-2-(pyridin-4-yl)-prop-2-enenitrile ( [...] Read more.

We report single crystal X-ray diffraction (hereafter, SCXRD) analyses of derivatives featuring the electron-donor N-ethylcarbazole or the (4-diphenylamino)phenyl moieties associated with a -CN group attached to a double bond. The compounds are (2Z)-3-(4-(diphenylamino)-phenyl)-2-(pyridin-3-yl)prop-2-enenitrile (I), (2Z)-3-(4-(diphenylamino)phenyl)-2-(pyridin-4-yl)-prop-2-enenitrile (II) and (2Z)-3-(9-ethyl-9H-carbazol-3-yl)-2-(pyridin-2-yl)enenitrile (III). SCXRD analyses reveal that I and III crystallize in the monoclinic space groups P2/c with Z’ = 2 and C2/c with Z’ = 1, respectively. Compound II crystallized in the orthorhombic space group Pbcn with Z’ = 1. The molecular packing analysis was conducted to examine the pyridine core effect, depending on the ortho, meta- and para-positions of the nitrogen atom, with respect to the optical properties and number of independent molecules (Z’). It is found that the double bond bearing a diphenylamino moiety introduced properties to exhibit a strong π-π-interaction in the solid state. The compounds were examined to evaluate the effects of solvent polarity, the role of the molecular structure, and the molecular interactions on their self-assembly behaviors. Compound I crystallized with a cell with two conformers, anti and syn, due to interaction with solvent. DFT calculations indicated the anti and syn structures of I are energetically stable (less than 1 eV). Also electrochemical and photophysical properties of the compounds were investigated, as well as the determination of optimization calculations in gas and different solvent (chloroform, cyclohexane, methanol, ethanol, tetrahydrofuran, dichloromethane and dimethyl sulfoxide) in the Gaussian09 program. The effect of solvent by PCM method was also investigated. The frontier HOMO and LUMO energies and gap energies are reported. Full article

(This article belongs to the Special Issue Photoactive Molecules)

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1658 KiB

Open AccessArticle

A Peptoid-Based Fluorescent Sensor for Cyanide Detection

by Bumhee Lim and Jeeyeon Lee

Molecules 2016, 21(3), 339; https://doi.org/10.3390/molecules21030339 - 10 Mar 2016

Cited by 26 | Viewed by 7303

Abstract

Peptoids, N-substituted glycine oligomers, are versatile peptidomimetics with diverse biomedical applications. However, strategies to the development of novel fluorescent peptoids as chemical sensors have not been extensively explored, yet. Here, we synthesized a novel peptoid-based fluorescent probe in which a coumarin moiety [...] Read more.

Peptoids, N-substituted glycine oligomers, are versatile peptidomimetics with diverse biomedical applications. However, strategies to the development of novel fluorescent peptoids as chemical sensors have not been extensively explored, yet. Here, we synthesized a novel peptoid-based fluorescent probe in which a coumarin moiety was incorporated via copper(I)-catalyzed azide-alkyne cycloaddition reaction. Fluorescence of the newly generated coumarin-peptoid was dramatically quenched upon coordination of the Cu²⁺ ion, and the resulting peptoid-Cu²⁺ complex exhibited significant Turn-ON fluorescence following the addition of CN⁻. The rapid and reversible response, combined with cyanide selectivity of the synthesized peptoid, reflects a multistep photo-process and supports its utility as a new type of CN⁻ sensor. Full article

(This article belongs to the Special Issue Photoactive Molecules)

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4022 KiB

Open AccessArticle

Photochemistry of the α-Al₂O₃-PETN Interface

by Roman V. Tsyshevsky, Anton Zverev, Anatoly Mitrofanov, Sergey N. Rashkeev and Maija M. Kuklja

Molecules 2016, 21(3), 289; https://doi.org/10.3390/molecules21030289 - 29 Feb 2016

Cited by 8 | Viewed by 7949

Abstract

Optical absorption measurements are combined with electronic structure calculations to explore photochemistry of an α-Al₂O₃-PETN interface formed by a nitroester (pentaerythritol tetranitrate, PETN, C₅H₈N₄O₁₂) and a wide band gap aluminum oxide [...] Read more.

Optical absorption measurements are combined with electronic structure calculations to explore photochemistry of an α-Al₂O₃-PETN interface formed by a nitroester (pentaerythritol tetranitrate, PETN, C₅H₈N₄O₁₂) and a wide band gap aluminum oxide (α-Al₂O₃) substrate. The first principles modeling is used to deconstruct and interpret the α-Al₂O₃-PETN absorption spectrum that has distinct peaks attributed to surface F⁰-centers and surface—PETN transitions. We predict the low energy α-Al₂O₃ F⁰-center—PETN transition, producing the excited triplet state, and α-Al₂O₃ F⁰-center—PETN charge transfer, generating the PETN anion radical. This implies that irradiation by commonly used lasers can easily initiate photodecomposition of both excited and charged PETN at the interface. The feasible mechanism of the photodecomposition is proposed. Full article

(This article belongs to the Special Issue Photoactive Molecules)

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4320 KiB

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Synthesis and Characterization of Novel Polythiophenes Containing Pyrene Chromophores: Thermal, Optical and Electrochemical Properties

by Bianca X. Valderrama-García, Efraín Rodríguez-Alba, Eric G. Morales-Espinoza, Kathleen Moineau Chane-Ching and Ernesto Rivera

Molecules 2016, 21(2), 172; https://doi.org/10.3390/molecules21020172 - 30 Jan 2016

Cited by 35 | Viewed by 6345

Abstract

A novel series of pyrene containing thiophene monomers TPM1–5 were synthesized and fully characterized by FTIR, MS, ¹H- and ¹³C-NMR spectroscopy; their thermal properties were determined by TGA and DSC. These monomers were chemically polymerized using FeCl₃ as [...] Read more.

A novel series of pyrene containing thiophene monomers TPM1–5 were synthesized and fully characterized by FTIR, MS, ¹H- and ¹³C-NMR spectroscopy; their thermal properties were determined by TGA and DSC. These monomers were chemically polymerized using FeCl₃ as oxidizing agent to give the corresponding oligomers TPO1–5) and they were electrochemically polymerized to obtain the corresponding polymer films deposited onto ITO. All oligomers exhibited good thermal stability, with T₁₀ values between 255 and 299 °C, and T_g values varying from 36 to 39 °C. The monomers showed an absorption band at 345 nm due to the S₀ → S₂ transition of the pyrene group, whereas the fluorescence spectra showed a broad emission band arising from the “monomer” emission at 375–420 nm. The obtained polymers exhibited two absorption bands at 244 and 354 nm, due to the polythiophene and the pyrene moieties, respectively. The fluorescence spectra of polymers showed a broad “monomer” emission at 380–420 nm followed by an intense excimer emission band at 570 nm, due to the presence of intramolecular pyrene-pyrene interactions in these compounds. Full article

(This article belongs to the Special Issue Photoactive Molecules)

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2423 KiB

Open AccessArticle

An Amidochlorin-Based Colorimetric Fluorescent Probe for Selective Cu²⁺ Detection

by Wenting Li, Guohua Zhu, Jinghua Li, Zhiqiang Wang and Yingxue Jin

Molecules 2016, 21(1), 107; https://doi.org/10.3390/molecules21010107 - 18 Jan 2016

Cited by 25 | Viewed by 6882

Abstract

The design and synthesis of selective and sensitive chemosensors for the quantification of environmentally and biologically important ionic species has attracted widespread attention. Amidochlorin p6 (ACP); an effective colorimetric and fluorescent probe for copper ions (Cu²⁺) in aqueous solution [...] Read more.

The design and synthesis of selective and sensitive chemosensors for the quantification of environmentally and biologically important ionic species has attracted widespread attention. Amidochlorin p6 (ACP); an effective colorimetric and fluorescent probe for copper ions (Cu²⁺) in aqueous solution derived from methyl pheophorbide-a (MPa) was designed and synthesized. A remarkable color change from pale yellow to blue was easily observed by the naked eye upon addition of Cu²⁺; and a fluorescence quenching was also determined. The research of fluorescent quenching of ACP-Cu²⁺ complexation showed the detection limit was 7.5 × 10⁻⁸ mol/L; which suggested that ACP can act as a high sensitive probe for Cu²⁺ and can be used to quantitatively detect low levels of Cu²⁺ in aqueous solution. In aqueous solution the probe exhibits excellent selectivity and sensitivity toward Cu²⁺ ions over other metal ions (M = Zn²⁺; Ni²⁺; Ba²⁺; Ag⁺; Co²⁺; Na⁺; K⁺; Mg²⁺; Cd²⁺; Pb²⁺; Mn²⁺; Fe³⁺; and Ca²⁺). The obvious change from pale yellow to blue upon the addition of Cu²⁺ could make it a suitable “naked eye” indicator for Cu²⁺. Full article

(This article belongs to the Special Issue Photoactive Molecules)

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2782 KiB

Open AccessArticle

Solvatochromic and Single Crystal Studies of Two Neutral Triarylmethane Dyes with a Quinone Methide Structure

by Katherine Chulvi, Ana M. Costero, Luis E. Ochando, Salvador Gil, José-Luis Vivancos and Pablo Gaviña

Molecules 2015, 20(11), 20688-20698; https://doi.org/10.3390/molecules201119724 - 19 Nov 2015

Cited by 4 | Viewed by 6655

Abstract

The crystal structure of two neutral triarylmethane dyes with a p-quinone methide core was determined by X-ray diffraction analysis. The spectroscopic characteristics of both compounds in 23 solvents with different polarities or hydrogen-bonding donor (HBD) abilities has been studied as a function of [...] Read more.

The crystal structure of two neutral triarylmethane dyes with a p-quinone methide core was determined by X-ray diffraction analysis. The spectroscopic characteristics of both compounds in 23 solvents with different polarities or hydrogen-bonding donor (HBD) abilities has been studied as a function of three solvatochromic parameters (E_T(30), π* and α). Both compounds 1 and 2 showed a pronounced bathochromic shift of the main absorption band on increasing solvent polarity and HBD ability. The correlation is better for compound 2 than for compound 1. The stronger effect and better correlation was observed for compound 2 with the increment of the solvent HBD ability (α parameter). Full article

(This article belongs to the Special Issue Photoactive Molecules)

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