Naphthalene Moiety Research Articles

Quinonaphthothiazines, syntheses, structures and anticancer activities

Two new types of pentacyclic azaphenothiazines being quinonaphthothiazines were obtaining from the reactions of dichlorodiquinolinyl disulfide with 1- and 2-naphthylamines. As the reactions could proceed in many ways, the proper structure elucidation was crucial. The structure determination was based on the 2D NMR spectra (NOESY, HSQC and HMBC) of the methyl derivatives. The final structure evidences came from X-ray analysis of the monocrystals. The new quinonaphthothiazines represent angularly fused pentacyclic ring systems which is folded along the N–S axis. The parent NH-compounds were transformed into the N-derivatives. Some quinonaphthothiazines exhibited promising anticancer activity against glioblastoma SNB-19, melanoma C-32 and human ductal breast epithelial tumor T47D cell lines. The anticancer activity dependent on the nature of the substituents and the ring fusion between the thiazine and naphthalene moieties. Two compounds were more active than the reference drug, cisplatin.

Novel blue emitters based on anthracene derivatives with naphthalene and phenylquinoline moieties for organic light-emtting diodes

In this study, we have designed three blue emitters based on anthracene derivatives with electron withdrawing phenylquinoline moieties. To explore the electroluminescence properties of these materials as blue materials, multilayer blue organic light-emtting diodes (OLEDs) were fabricated in the following device structure: indium–tin-oxide (ITO)/4,4′-bis[N-(1-naphthyl)-N-phenylamino]biphenyl (NPB)/blue emitters (30 nm) bathophenanthroline (Bphen) (35 nm)/lithium quinolate (Liq) (2 nm)/Al. Among those, a device using 4-{4-[10-(naphthalen-2-yl)anthracen-9-yl]phenyl}-2-phenylquinoline exhibited efficient blue emission with a luminous and power efficiency of 1.59 cd/A and 0.89 lm/W at 20 mA/cm2, respectively. The commission internationale de l’éclairage (CIE) coordinates of this device were (x = 0.17, y = 0.21) at 7.5 V.

The self-aggregation of some 7H-indolo[1,2-a]quinolinium dyes in aqueous solution

The aggregation of some 7H-indolo[1,2-a]quinolinium dyes in aqueous solution was investigated based on UV–vis spectroscopy. The influence of pH, dye concentration, ionic strength and the addition of organic solvents on the process was studied. The aggregation took place in alkaline solution and was strongly affected by ionic strength and the presence of organic solvents. The existence of aggregates in the solution was manifested in a new band appearance which exhibited bathochromic shift with respect to the monomer band. For all studied dyes the band was assigned to the dimer and the equilibrium constants for dimer formation were calculated. The dye tendency to aggregate was determined by its structure and was enhanced by the presence of naphthalene moiety in comparison to that of benzene ring as well as electron-rich substituents such as halogens.

The Impact of Antiaromatic Subunits in [4n+2] π-Systems: Bispentalenes with [4n+2] π-Electron Perimeters and Antiaromatic Character.

Three series of stable, neutral, π-extended bispentalene derivatives, with two pentalenes fused to a central benzene or naphthalene moiety, have been prepared through a modified double carbopalladation cascade reaction. While these chromophores feature skeletons with [4n+2] π-electron perimeters, the two 8 π-electron pentalene subunits strongly influence bonding and spectral properties. (1)H NMR spectra showed large upfield shifts of the protons in the pentalene moieties, comparable to antiaromatic monobenzopentalenes. Further investigations on magnetic ring currents through NICS-XY-scans suggest a global paratropic current and a local diatropic current at the central benzene ring in two of the series, while the third series, with a central naphthalene ring, showed more localized ring currents, with stronger paratropic ring currents on the pentalene moieties. X-ray diffraction analyses revealed planar bispentalene cores with large double- and single-bond alternation in the pentalene units, characteristic for antiaromaticity, and small alternation in the central aromatic rings. In agreement with TD-DFT calculations, both optical and electrochemical data showed much smaller HOMO-LUMO energy gaps compared to other neutral, acene-like hydrocarbons with the same number of fused rings. Both experimental and computational results suggest that the molecular properties of the presented bispentalenes are dominated by the antiaromatic pentalene-subunits despite the [4n+2] π-electron perimeter of the skeletons.

Distance Dependence of Electron Spin Polarization during Photophysical Quenching of Excited Naphthalene by TEMPO Radical.

Quenching of excited states by a free radical is generally studied in systems where these two are separate entities freely moving in a liquid solution. Random diffusive encounters bring them together to cause the quenching and leave the spins of the radical polarized. In the dynamics of the radical-triplet pair mechanism of the generation of electron spin polarization (ESP), the distance-dependent exchange interaction plays a crucial role. To investigate how the distance between the excited molecule and the radical influences the ESP, we have covalently linked a naphthalene moiety to a TEMPO free radical through a spacer group of three different lengths. We compared the ESP process of these linked compounds with that of the usual "unlinked system" of naphthalene and TEMPO through time-resolved EPR experiments at low temperature in n-hexane solution. The time evolution of both the linked and the "unlinked system" was treated on a similar footing. The time-dependent EPR signal was analyzed by combining photophysical kinetics and time-dependent Bloch equations incorporating spin dynamics. Sequential quenching of the singlet state and the triplet state of naphthalene was seen in all the systems, as revealed through the spin-polarized TREPR spectra of opposite phase. The magnitudes of the ESP in the linked molecules were higher than those of the "unlinked system," showing that when the two moieties are held together greater mixing of quartet-doublet states takes place. The magnitudes of ESP steadily decrease with increasing the length of the spacer group. The polarization magnitudes due to triplet quenching and singlet quenching are very similar, differing by a factor of only ∼2. These characteristics show that for all the linked molecules the quenching takes place in the "weak exchange" regime and at almost the same distance of separation between the two moieties. Our results also showed that observation of small absorptive TREPR signals does not necessarily imply that its magnitude of polarization is small.

Binding and ratiometric dual ion recognition of Zn(2+) and Cu(2+) by 1,3,5-tris-amidoquinoline conjugate of calix[6]arene by spectroscopy and its supramolecular features by microscopy.

Lower rim amide linked 8-amino quinoline and 8-amino naphthalene moiety 1,3,5-triderivatives of calix[6]arene L1 and L2 have been synthesized and characterized. While the L1 acts as a receptor molecule, the L2 acts as a control molecule. The complexation between L1 and Cu(2+) or Zn(2+) was delineated by the absorption and electrospray ionization (ESI) MS spectra. The binding ability of these molecules toward biologically important metal ions was studied by fluorescence and absorption spectroscopy. The derivative L1 detects Zn(2+) by bringing ratiometric change in the fluorescence signals at 390 and 490 nm, but in the case of Cu(2+), it is only the fluorescence quenching of 390 nm band that is observed, while no new band is observed at 390 nm. The stoichiometry of both the complexes is 1:1 and was confirmed in both the cases by measuring the ESI mass spectra. The isotopic peak pattern observed in the ESI MS confirmed the presence of Zn(2+) or Cu(2+) present in the corresponding complex formed with L1. Among these two ions, the Cu(2+) exhibits higher sensitivity. The density-functional theory (DFT) studies revealed the conformational changes in the arms and also revealed the coordination features in the case of the metal complexes. The arm conformational changes upon Zn(2+) binding were supported by nuclear Overhauser effect spectrometry (NOESY) studies. The stronger binding of Cu(2+) over that of Zn(2+) observed from the absorption study was further supported by the complexational energies computed from the computational data. While the L1 exhibited spherical particles, upon complexation with Cu(2+), it exhibits chain like morphological features in scanning electron microscopy (SEM) but only small aggregates in the case of Zn(2+). Thus, even the microscopy data can differentiate the complex formed between L1 and Cu(2+) from that formed with Zn(2+).

What Is the Structure of the Naphthalene-Benzene Heterodimer Radical Cation? Binding Energy, Charge Delocalization, and Unexpected Charge-Transfer Interaction in Stacked Dimer and Trimer Radical Cations.

The binding energy of the naphthalene(+•)(benzene) heterodimer cation has been determined to be 7.9 ± 1 kcal/mol for C10H8(+•)(C6H6) and 8.1 ± 1 kcal/mol for C10H8(+•)(C6D6) by equilibrium thermochemical measurements using the mass-selected drift cell technique. A second benzene molecule binds to the C10H8(+•)(C6D6) dimer with essentially the same energy (8.4 ± 1 kcal/mol), suggesting that the two benzene molecules are stacked on opposite sides of the naphthalene cation in the (C6D6)C10H8(+•)(C6D6) heterotrimer. The lowest-energy isomers of the C10H8(+•)(C6D6) and (C6D6)C10H8(+•)(C6D6) dimer and trimer calculated using the M11/cc-pVTZ method have parallel stacked structures with enthalpies of binding (-ΔH°) of 8.4 and 9.0 kcal/mol, respectively, in excellent agreement with the experimental values. The stacked face-to-face class of isomers is calculated to have substantial charge-transfer stabilization of about 45% of the total interaction energy despite the large difference between the ionization energies of benzene and naphthalene. Similarly, significant delocalization of the positive charge is found among all three fragments of the (C6D6)C10H8(+•)(C6D6) heterotrimer, thus leaving only 46% of the total charge on the central naphthalene moiety. This unexpectedly high charge-transfer component results in activating two benzene molecules in the naphthalene(+•)(benzene)2 heterotrimer cation to associate with a third benzene molecule at 219 K to form a benzene trimer cation and a neutral naphthalene molecule. The global minimum of the C10H8(+•)(C6H6)2 heterotrimer is found to be the one where the naphthalene cation is sandwiched between two benzene molecules. It is remarkable, and rather unusual, that the binding energy of the second benzene molecule is essentially the same as that of the first. This is attributed to the enhanced charge-transfer interaction in the stacked trimer radical cation.

Electrochemical investigation into the electron transfer mechanism of a diiron hexacarbonyl complex bearing a bridging naphthalene moiety

Electrochemical investigations and chemical reduction of the diiron hexacarbonyl complex bearing a 1,8-naphthalene moiety bridging linkage into which a ferrocenyl group was deliberately incorporated were performed. The complex exhibited two reduction and two oxidation processes in dichloromethane. Our results revealed that the first reduction could be assigned to an ECE (Electrochemical, Chemical and Electrochemical) mechanism with the second potential inversed. When the monoanion generated in the first reduction underwent, in part, the ECE mechanism, the rest of the monoanion continued to accept the second electron without involving a coupled chemical reaction, so called EE (Electrochemical and Electrochemical) mechanism. The two mechanisms co-existed in the electron transfer and compete with each other. By both increasing scanning rate and lowering temperature, the coupled reaction in the ECE mechanism could be effectively suppressed whereas the second reduction is highly irreversible. The coupled chemical reaction following the EE process might lead to the same dianion as that produced in the ECE processes. Although chemical reduction and re-oxidation were unsuccessful of confirming the transformation between the two dianions, DFT calculations did support this proposed chemical reaction.

Studies on the interaction of novel organogermanium sesquioxides with DNA

The affinity and mode of interaction of four novel organogermanium sesquioxides with calf thymus DNA(CT-DNA) and two synthetic oligonucleotides, d(AT)22d(AT)22 and d(GC)22d(GC)22, were investigated by a combination of absorption spectroscopy, DNA thermal denaturalization method, viscosity method, fluorometric technique, and competitive binding study with ethidium bromide(EB). The results show that the organogermanium compounds can interact with DNA by intercalation, the binding ability of the compounds to CT-DNA and the synthetic oligonucleotides was found to be modest(in comparison to the proven intercalators), with binding constants on the order of 103–105 L/mol, respectively. Generally, the binding of the organogermanium sesquioxides with naphthalene moiety to DNA is stronger than that of the compounds with anthraquinone moiety. And the compounds with anthraquinone moiety have preference for binding to AT-rich duplexes, whereas the compounds with naphthalene moiety have a little preference for binding to GC-rich duplexes. DNA may be the primary effect target.

Exploiting the efficacy of Lysinibacillus sp. RGS for decolorization and detoxification of industrial dyes, textile effluent and bioreactor studies

Complete decolorization and detoxification of Reactive Orange 4 within 5 h (pH 6.6, at 30°C) by isolated Lysinibacillus sp. RGS was observed. Significant reduction in TOC (93%) and COD (90%) was indicative of conversion of complex dye into simple products, which were identified as naphthalene moieties by various analytical techniques (HPLC, FTIR, and GC–MS). Supplementation of agricultural waste extract considered as better option to make the process cost effective. Oxido-reductive enzymes were found to be involved in the degradation mechanism. Finally Loofa immobilized Lysinibacillus sp. cells in a fixed-bed bioreactor showed significant decolorization with reduction in TOC (51 and 64%) and COD (54 and 66%) for synthetic and textile effluent at 30 and 35 mL h−1 feeding rate, respectively. The degraded metabolites showed non-toxic nature revealed by phytotoxicity and photosynthetic pigments content study for Sorghum vulgare and Phaseolus mungo. In addition nitrogen fixing and phosphate solubilizing microbes were less affected in treated wastewater and thus the treated effluent can be used for the irrigation purpose. This work could be useful for the development of efficient and ecofriendly technologies to reduce dye content in the wastewater to permissible levels at affordable cost.

Quantifying the formation of chiral luminescent lanthanide assemblies in an aqueous medium through chiroptical spectroscopy and generation of luminescent hydrogels.

Herein we present the synthesis and the photophysical evaluation of water-soluble chiral ligands (2·(R,R) and 2·(S,S)) and their application in the formation of lanthanide directed self-assembled structures. These pyridine-2,6-dicarboxylic amide based ligands, possessing two naphthalene moieties as sensitising antennae, that can be used to populate the excited state of lanthanide ions, were structurally modified using 3-propanesultone and caesium carbonate, allowing for the incorporation of a water-solubilising sulfonate motif. We show, using microwave synthesis, that Eu(III) forms chiral complexes in 1 : 3 (M : L) stoichiometries (Eu·[2·(R,R)]3 and Eu·[2·(S,S)]3) with these ligands, and that the red Eu(III)-centred emission arising from these complexes has quantum yields (Φtot) of 12% in water. Both circular dichroism (CD) and circular polarised luminescence (CPL) analysis show that the complexes are chiral; giving rise to characteristic CD and CPL signatures for both the Λ and the Δ complexes, which both possess characteristic luminescence dissymmetry factors (g(lum)), describing the structure in solution. The self-assembly process was also monitored in situ by observing the changes in the ligand absorption and fluorescence emission, as well as in the Eu(III) luminescence. The change, fitted using non-linear regression analysis, demonstrated high binding affinity for Eu(III) which in part can be assigned to being driven by additional hydrophobic effects. Moreover, using CD spectroscopy, the changes in the chiroptical properties of both (2·(R,R) and 2·(S,S)) were monitored in real time. Fitting the changes in the CD spectra allowed for the step-wise binding constants to be determined for these assemblies; these matched well with those determined from both the ground and the excited state changes. Both the ligands and the Eu(III) complexes were then used in the formation of hydrogels; the Eu(III)-metallogels were luminescent to the naked-eye.

Chemical and physical modification of poly(p-phenylene benzobisoxazole) polymers for improving properties of the PBO fibers. I. Ultraviolet-ageing resistance of PBO fibers with naphthalene moiety in polymer chain

In purpose of improving the poor ultraviolet-ageing resistance of poly(p-phenylene benzobisoxazole) (PBO) fiber, a series of modified PBO were synthesized in poly(phosphoric acid) (PPA) by introducing 2,6-naphthalene groups into PBO molecules. 2,6-naphthalenedicarboxylic acid (NDCA) was selected as a comonomer. It was found that there was little effect of NDCA on the molecular weight of PBO. PBO and PBO-NDCA fibers were prepared through dry-jet wet spinning. The PBO-NDCA fibers exhibited much improved UV-ageing resistance by showing less reduction in tensile strength after same amount of UV exposure, and the UV-ageing resistance increased with increasing of NDCA content. It was notable that the fiber diameter was significantly decreased in proportion to UV exposure time, which implies a kind of etching was occurred on the surface of the fibers by UV irradiation. It was also found that the degree of UV etching in fibers decreased with increasing of NDCA content. Surface morphology of the fibers before and after UV irradiation was observed using FE-SEM and AFM.

Ratiometric fluorescent probe for Al3+ based on coumarin derivative in aqueous media

In this study, a novel ratiometric chemosensor for Al3+ (HL) which contains coumarin and naphthalene moieties has been designed and synthesized on the basis of the mechanism of internal charge transfer (ICT).

Complementary Synthetic Approaches to Elongated Polycyclic Arenes with Regioisomeric Carboxylic Substitution Patterns

AbstractThe reaction of 1,5‐dibromoanthracene with butyllithium and diethyloxalate followed by saponification gives anthrylene‐1,5‐diglyoxylic acid as a bifunctional reactant. Its double condensation with 2‐bromophenylacetic acid, followed by double cyclization, leads to a bright‐orange near‐linear dinaphtho‐anthracene‐tetracarboxdiimide with substituents on the naphthalene moieties. An analogous condensation‐cyclization sequence of 2,5‐dibromophenylene‐1,4‐diacetic acid with 1‐naphthylglyoxylic acid leads to an isomeric red diimide substituted on the anthracene nucleus. The striking difference in band gaps shows that diimide substitution on the central moiety of diareno[a,h]anthracenes is particularly efficient in inducing long‐wavelength absorption. The substitution dependence of the band gap is found to be mainly caused by a variation of the reduction potentials with substituent position, whereas the oxidation potentials are largely substitution‐independent.

Synthesis of the carbon skeleton of the griseorhodins

A synthetic strategy to access the carbon skeleton of the griseorhodin family of natural products has been developed. The key step involved the acid-mediated spirocyclisation of a highly functionalised dihydroxyketone. The delicate electronic balance between the electron rich naphthalene moiety and the electron-withdrawing isocoumarin ring system were finely tuned to facilitate the acid-mediated spirocyclisation reaction. The development of this synthetic strategy provides a basis for further synthetic investigations towards the more structurally complex griseorhodin natural products.

5-Hydroxy substituted naphthofurans and naphthothiazoles as precursors of photochromic benzochromenes

3-Benzoylnaphtho[1,2-b]furan-5-ol forms a photochromic benzochromene upon reaction with a 1,1-diarylprop-2-yn-1-ol affording a red coloured photomerocyanine, with a half-life of 2.3 min, upon UV-irradiation. Retention of the initial 1,4-oxygenation pattern of the naphthalene moiety through replacement of the furan unit with a methoxy group led to a benzochromene, which developed a similar red colour upon UV-irradiation but was more persistent with a half-life of over 42 min. Treatment of the 3-benzoylnaphtho[1,2-b]furan-5-ol with a 1,1,3-triarylprop-2-yn-1-ol similarly afforded a benzochromene, which did not display any photochromism at ambient temperature as a consequence of steric interactions in the photomerocyanines. The synthesis of N-(5-hydroxynaphtho[1,2-d]thiazol-2-yl)acetamide, as a precursor to a photochromic hetero-fused benzochromene, by the mild selective deprotection of the O-acetyl group of 2-acetamidonaphtho[1,2-d]thiazol-5-yl acetate was complicated by a facile, competitive, oxidative dimerisation to afford a novel [2,2′-binaphthothiazole]-1,1′-diol.

Substituent effects on the properties of photochromic hybrid diarylethenes with a naphthalene moiety

Four new unsymmetrical photochromic diarylethenes bearing both naphthalene and thiophene moieties were synthesized, and the structures of two diarylethenes were determined by single-crystal X-ray diffraction analysis. The naphthalene ring was connected directly to the central perfluorocyclopentene ring as an aryl moiety and available to participate in photoisomerization reaction. All the diarylethenes exhibited favorable photochromism and functioned as fluorescence switches in both solution and poly(methyl methacrylate) films. The electron-withdrawing substituent significantly shifted the absorption maxima to a longer wavelength and evidently suppressed the cycloreversion quantum yield, whereas the electron-donating substituents enhanced the fluorescence quantum yield of diarylethenes with a naphthalene moiety. Furthermore, cyclic voltammograms suggested that the oxidation onsets and band-gaps of the open-ring isomers were much bigger than those of the closed-ring isomers. The results indicated that the substituents at the 5-position of thiophene ring could availably modulate their optical and electrochemical behaviors.

In Situ Synthesised Silver Nanoparticle‐Infused L‐Lysine‐Based Injectable Hydrogel: Development of a Biocompatible, Antibacterial, Soft Nanocomposite

AbstractThe synthesis of L‐lysine‐based amphiphilic hydrogelator consisting of a naphthalene moiety at the N termini and an ethyleneoxy unit with free primary amine at the C terminus is reported. The amphiphile showed good gelation ability with minimum gelation concentration 0.6 % w/v in binary mixtures of dimethyl sulfoxide/phosphate buffer (1:4 v/v, pH 7.4). The hydrogel was characterised by spectroscopic and microscopic studies to delineate the role of non‐covalent interactions in self‐assembly gelation. Subsequently, Ag nanoparticles were synthesised within the hydrogel by in situ photo‐reduction of AgNO3 under sunlight, in which the gelators act as reducing/stabilising agents. The nanocomposites were characterised by transmission electron microscopy, UV/Vis and X‐ray diffraction spectroscopy and thermogravimetric analysis. Rheology of the soft nanocomposite showed significant mechanical strength and thixotropic self‐recovery properties, which made the composite suitable for use as a syringe‐injectable hydrogel. These soft nanocomposites exhibited excellent antibacterial activity against both Gram‐positive and Gram‐negative bacteria. They showed low haemolytic activity and high biocompatibility to mammalian (Chinese hamster ovarian) cells. In addition, agar–gelatin film infused with these nanocomposites allowed normal growth of mammalian cells on its surface while being lethal towards bacteria.

New semiconducting copolymers containing alkyl quarterthiophene and alkoxy naphthalene moieties for organic thin film transistors

A π-conjugated alkyl quarterthiophene-based copolymer was synthesized by a Suzuki coupling reaction, and its optical, thermal, and electrochemical and organic thin film transistor properties were characterized. The copolymers showed good solubility in common solvents such as chloroform and toluene, etc. The weight average molecular weight (Mw) of PQTHN and PQTON were found to be 9,200 with polydispersity of 1.2 and 30,600 with polydispersity of 2.39, respectively. The structure of PQTHN and PQTON was confirmed using 1H NMR and FTIR spectroscopy. Solution-processed organic thin film transistors (OTFTs) using PQTON exhibited 6.96×10−4 cm2V−1s−1 as mobility with an on/off ratio of 2.46×104.

Dibenzo[a,f]perylene bisimide: effects of introducing two fused rings.

Perylene bisimides (PBIs) are fascinating dyes with various potential applications. To study the effects of introducing a dibenzo-fused structure to the perylene moiety, π-extended PBI derivatives with a dibenzo-fused structure at both of the a and f bonds were synthesized. The twisted structure was characterized by X-ray crystal structure analysis. In the cyclic voltammograms, the dibenzo[a,f]-fused PBI showed a reversible oxidation wave at much less positive potential, relative to a dibenzo[a,o]-fused PBI derivative. These data indicated that two ring fusions at both sides of a naphthalene moiety, which construct a tetracene core, effectively raise the HOMO level compared to fusion of one ring at each naphthalene moiety (two anthracene cores). The dibenzo[a,f]-fused PBI derivative showed an absorption band at 735 nm with a shoulder band reaching 900 nm.