Alkoxyl Substituents Research Articles

Studies of optical, photophysical, and thermal properties of poly(paraphenylenevinylene) (PPV) polymers with symmetric alkoxy side‐chain lengths for potential application in electronic devices

AbstractOptical, photophysical, and thermal properties of poly(paraphenylenevinylene) (PPV) derivatives of various symmetric alkoxyl substituents were studied with UV–vis and photoluminescence spectroscopy. Molar absorptivity coefficients of the symmetric monomers increased compared to that of hydroquinone and its derivatives. The symmetric polymers exhibited photoluminescence quantum yields in the range of 32%–39% and excited‐state lifetimes of 3.01–3.61 ns. The emission energy values for the calculated band gaps were in the range of 2.16–2.12 eV for the symmetric polymers. The photoluminescent characteristics of these compounds may show great potential in improving the emitting layers of electronic devices. The thermal behavior and heat changes of the symmetric dialkyl PPV polymers were monitored by TGA and DSC. Glass transition temperatures (Tg) for these polymers were observed as being in range of 67–108°C. The heat values of the symmetric dialkyl PPV polymers were found to be in range 220.41–599.98 J/g, and the entropy values of symmetric dialkyl PPV polymers were determined to be in range 0.567–1.754 J/ g °C.Highlights• Symmetric poly(phenylene vinylene) (PPV) derivatives were prepared.• UV–vis spectroscopy was used for optical absorption studies.• Photophysical properties were examined by photoluminescence spectroscopy.• TGA was used for the thermal behavior of symmetric dialkyl PPV polymers.• Heat changes of symmetric dialkyl PPV polymers were investigated by DSC.

Tunable Fluorescence via Self-Assembled Switching of AIE-Active Micelle-like Nanoaggregates.

Chemical structures bearing a combination of aggregation-induced emission enhancement (AIEE) and intramolecular charge transfer (ICT) properties attracted the attention of many researchers. Recently, there is an increasing demand to pose tunable AIEE and ICT fluorophores that could present their conformation changes-related emission colors by adjusting the medium polarity. In this study, we designed and synthesized a series of 4-alkoxyphenyl-substituted 1,8-naphthalic anhydride derivatives NAxC using the Suzuki coupling reaction to construct donor-acceptor (D-A)-type fluorophores with alkoxyl substituents of varying carbon chain lengths (x = 1, 2, 4, 6, 12 in NAxC). To explain the observation that molecules with longer carbon chains revealed unusual fluorescence enhancement in water, we study the optical properties and evaluate their locally excited (LE) and ICT states by solvent effects combined with Lippert-Mataga plots. Then, we explored the self-assembly abilities of these molecules in water-organic (W/O) mixed solutions and observed the morphology of its nanostructure using a fluorescence microscope and SEM. The results show that NAxC, x = 4, 6, 12 show different degrees of self-assembly behaviors and corresponding aggregation-induced emission enhancement (AIEE) progresses. At the same time, different nanostructures and corresponding spectral changes can be obtained by adjusting the water ratio in the mixed solution. That is, NAxC compounds present different transitions between LE, ICT and AIEE based on the polarity, water ratio and time changes. We designed NAxC as the structure-activity relationship (SAR) of the surfactant to demonstrate that AIEE comes from the formation of micelle-like nanoaggregates, which causes a restriction of the transfer from the LE state to the ICT state, and micelle formation results in a blue-shift in emission and enhances the intensity in the aggregate state. Among them, NA12C is most likely to form micelles and the most obvious fluorescence enhancement, which will switch over time due to the nano-aggregation transition.

Synthesis, Structure-Activity Relationship and Antibacterial Activity of Some Simple (E)-Chalcones

In present work, 14 simple (E)-chalcones (1-14), synthesized via the Claisen-Schmidt condensation between arylmethyl ketone and aromatic aldehyde in the presence of either in NaOH or H3BO3, were tested for in vitro antibacterial activity against two Gram-positive (Staphylococcus aureus and Bacillus subtilis) and three Gram-negative (Escherichia coli, Enterobacter cloacae and Klebsiella pneumoniae) bacterial strains. Among them, (E)-3-(4-hydroxy-3-methoxyphenyl)-1-(3-nitrophenyl)prop-2-en-1-one (8) was found most efficient, while (E)-3-(4-(dimethylamino)phenyl)-1-phenylprop-2-en-1-one (4) and (E)-1-(2,4-dihydroxyphenyl)-3-(4-(dimethylamino)-phenyl)prop-2-en-1-one (14) were completely ineffective. The rest of the (E)-chalcones have displayed moderate to good antibacterial activity, particularly against Gram-positive bacteria, while E. coli was found resistant. From the structure-activity relationship (SAR) analysis, it is revealed that the presence of a strong electron-withdrawing group (NO2) in ring A and the presence of electron-donating group in ring B of (E)-chalcones could enhance the antibacterial activity. The presence of hydroxyl and/or alkoxyl substituents in both 3 and 4 positions of ring B proved beneficial.

Synthesis of New Star-Shaped Liquid Crystalline Cyclotriphosphazene Derivatives with Fire Retardancy Bearing Amide-Azo and Azo-Azo Linking Units.

Two series of new hexasubstituted cyclotriphosphazene derivatives were successfully synthesized and characterized. These derivatives are differentiated by two types of linking units in the molecules such as amide-azo (6a–j) and azo-azo (8a–j). The homologues of the same series contain different terminal substituents such as heptyl, nonyl, decyl, dodecyl, tetradecyl, hydroxyl, carboxyl, chloro, nitro, and amino groups. All the intermediates and final compounds were characterized using Fourier transform infrared spectroscopy (FT-IR), nuclear magnetic resonance spectroscopy (NMR), and Carbon, Hydrogen, and Nitrogen (CHN) elemental analysis. Liquid crystal properties for all compounds were determined using polarized optical microscope (POM). It was found that only intermediates 2a–e with nitro and alkoxyl terminal chains showed a smectic A phase. All the final compounds with alkoxyl substituents are mesogenic with either smectic A or C phases. However, other intermediates and compounds were found to be non-mesogenic. The study on the fire retardancy of final compounds was determined using limiting oxygen index (LOI) method. The LOI value of pure polyester resin (22.53%) was increased up to 24.71% after treating with 1 wt% of hexachlorocyclotriphosphazene (HCCP). Moreover, all the compounds gave positive results on the LOI values and compound 6i with the nitro terminal substituent showed the highest LOI value of 27.54%.

Self‐Assembly of Di‐Guanine Peptide Nucleic Acid Amphiphiles into Fractal Patterns

AbstractPeptide nucleic acids (PNAs) amphiphiles have been reported to assemble into different nanostructures; however, there is immense untapped potential to control their supramolecular assemblies by altering their lipid chain. Here, we functionalized di‐guanine PNA with various hydrophobic appendages, namely dodecyl, p‐dodecylbenzoyl and pentadecyl phenol groups, to investigate the effect of aromatic linkers, long alkyl and alkoxyl substituents on hierarchical self‐assembly of di‐guanine PNA. Systematic electron microscopy and atomic force microscopy studies revealed that while all three derivatives of di‐guanine‐PNA formed nanospheres, only nanospheres of dodecylamide and pentadecyl phenol derivatives matured into nanorods, these later formed higher order fractal assemblies. Furthermore, we observed that inclusion of a positively charged lysine at the C‐terminus prevented fractal assembly, possibly due to electrostatic repulsion between the head groups. Thus, the findings of the present work might guide rational design of PNA amphiphiles to obtain specific self‐assembled morphology.

IR Spectroscopic Study of Lanthanide Hydroxo Complexes with Esters of Acetoacetic Acid

The IR spectra of hydroxo complexes of lanthanides (Ln) with the β-ketoesters methyl, ethyl, and allyl acetoacetate with the general formula LnL2OH·H2O (Ln = La, Gd, Lu; L = β-ketoesterate anion) were studied in the range of 400–1700 cm–1. In order to interpret the spectra and assign bands to the vibrations of the β-ketoesterate ligands a normal coordinate analysis of the model complexes LnL(OH)2 (Ln = La, Lu) was performed in the PBE0/ECP46(60) MWB + DZP approximation. The experimental data and the theoretical calculations show that the radius of the Ln(III) ion and the structure of the hydrocarbon radical of the alkoxyl substituent have a negligible effect on the value of π-electron delocalization in the [OCCCO] conjugated system of the chelate fragment, whereas the decrease of the Ln(III) ionic radius leads to increase of conjugation in the ester C(O)O group of the ligands.

SYNTHESIS AND PROPERTIES COMPARISON OF MESO-ARYLPORPHYRINS METAL COMPLEXES AS POTENTIAL DYES FOR SOLAR CELLS

This work is dedicated to the synthesis of porphyrin metal complexes for creation of dyesensitized solar cells (DSSC). Three different dyes were synthesized - zinc complexes of porphyrins containing alkoxyl substituents: with symmetric structure (Zn-P1), as well as asymmetric (type A3B) with the introduction of a donor (Zn-P2) or an acceptor (Zn-P3) substituents via the 1,3,5-triazine fragment. The spectral characteristics of the synthesized substances are compared. For all the obtained dyes, geometry optimization and visualization of the electron density distribution were carried out using computational methods based on the density functional theory (DFT). The location of the frontier unbound molecular orbitals is more optimal when an acceptor substituent containing anchor groups is introduced via the triazine moiety. However, the use of ligands containing an anchor group simplifies the synthesis of the dye and opens up more possibilities for varying both the ligand and the introduced donor substituents. As a result, it was concluded that the spatial distribution of the dye, when applied to the electrode and, consequently, the number of its molecules per unit area of the semiconductor, can have the greatest effect on the efficiency of a cell using t he described compounds.

Precisely Tuning Helical Twisting Power via Photoisomerization Kinetics of Dopants in Chiral Nematic Liquid Crystals.

It has been paid much attention to improve the helical twisting power (β) of dopants in chiral nematic liquid crystals (CLCs); however, the correlations between the β value and the molecular structures as well as the interaction with nematic LCs are far from clear. In this work, a series of reversibly photo-switchable axially chiral dopants with different lengths of alkyl or alkoxyl substituent groups have been successfully synthesized through nucleophilic substitution and the thiol-ene click reaction. Then, the effect of miscibility between these dopants and nematic LCs on the β values, as well as the time-dependent decay/growth of the β values upon irradiations, has been investigated. The theoretical Teas solubility parameter shows that the miscibility between dopants and nematic LCs decreases with increasing of the length of substituent groups from dopant 1 to dopant 4. The β value of chiral dopants in nematic LCs decreases from dopant 1 to dopant 4 both at the visible light photostationary state (PSS) and at the UV PSS after UV irradiation. With increasing of the length of substituent groups, the photoisomerization rate constant of dopants increases for trans-cis transformation upon UV irradiation and decreases for the reverse process upon visible light irradiation either in isotropic ethyl acetate or in anisotropic LCs, although the constant in ethyl acetate is several times larger than the corresponding value in LCs. Also, the color of the CLCs could be tuned upon light irradiations. These results enable the precise tuning of the pitch and selective reflection wavelength/color of CLCs, which paves the way to the applications in electro-optic devices, information storage, high-tech anticounterfeit, and so forth.

Rational design of slightly twisted coumarin molecules with remarkable solution and solid dual efficient luminescence

Endowing slightly twisted molecules highly emissive in both solution and solid state is of great importance for understanding the principle of maximizing the luminescent efficiency of luminophores. To this end, a series of slightly twisted coumarin luminophores CMs with different alkoxyl substituents at the 7-positions were synthesized. The effect of the substitutes on the diversity photophysical properties of the four compounds in solution, THF/H2O mixtures and solid state were investigated. Comparing to the referenced compound CM (3-p-tolyl-2H-chromen-2-one) that without a substitute, the introduced electron-rich alkoxyl substitutes not only enhanced the intramolecular charge transfer (ICT) effect, but also significantly modified their molecular packing patterns in the crystals. The combined effect of increasing the radiative and suppressing the nonradiactive pathways boosted the luminescence efficiency of CM1-CM3 in solution and the solid state simultaneously. Eventually, compound CM2 with an ethoxyl substitute exhibited the strongest blue emission with fluorescence quantum yields as high as 73.2% and 96.7% in solution and the solid state, respectively. This work presents an efficient strategy towards dual strong fluorescent luminophores in both solution and the solid state.

Modulating Mechanochromic Luminescence Quenching of Alkylated Iodo Difluoroboron Dibenzoylmethane Materials

Difluoroboron β-diketonate compounds exhibit solid-state luminescence phenomena. Among these are reversible mechanochromic luminescence (ML), aggregation induced emission (AIE), and mechanochromic luminescence quenching (MLQ). These properties can be tuned by alterations to the molecular structure. Dyes with varying halide substituents exhibit tunable ML, MLQ, and solid-state emission with high quantum yields. A series of difluoroboron dibenzoylmethane (BF2dbm) dyes with iodide and alkoxyl substituents (BF2dbm(I)OR) were synthesized where R = CH3 (C1), C5H11 (C5), C6H13 (C6), C12H25 (C12), and C18H37 (C18)). The 4-iodo parent compound BF2dbm(I) (H) was made for comparison. By keeping the heavy atom static, the dependence of ML properties on alkyl chain length was probed. The hydrogen derivative is only weakly emissive as a solid and exhibited minimal mechanoresponsive behavior. In contrast, alkoxy dyes exhibited tunable ML and MLQ properties depending on the length of the alkyl chain. Longer chain dyes co...

Soluble Flavanthrone Derivatives: Synthesis, Characterization, and Application to Organic Light-Emitting Diodes.

Simple modification of benzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridine-8,16-dione, an old and almost-forgotten vat dye, by reduction of its carbonyl groups and subsequent O-alkylation, yields solution-processable, electroactive, conjugated compounds of the periazaacene type, suitable for the use in organic electronics. Their electrochemically determined ionization potential and electron affinity of about 5.2 and -3.2 eV, respectively, are essentially independent of the length of the alkoxyl substituent and in good agreement with DFT calculations. The crystal structure of 8,16-dioctyloxybenzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridine (FC-8), the most promising compound, was solved. It crystallizes in space group P1‾ and forms π-stacked columns held together in the 3D structure by dispersion forces, mainly between interdigitated alkyl chains. Molecules of FC-8 have a strong tendency to self-organize in monolayers deposited on a highly oriented pyrolytic graphite surface, as observed by STM. 8,16-Dialkoxybenzo[h]benz[5,6]acridino[2,1,9,8-klmna]acridines are highly luminescent, and all have photoluminescence quantum yields of about 80 %. They show efficient electroluminescence, and can be used as guest molecules with a 4,4'-bis(N-carbazolyl)-1,1'-biphenyl host in guest/host-type organic light-emitting diodes. The best fabricated diodes showed a luminance of about 1900 cd m(-12) , a luminance efficiency of about 3 cd A(-1) , and external quantum efficiencies exceeding 0.9 %.

N,N′-Diaryl-perylene-3,9-diamine derivatives: synthesis, characterization and electroluminescence properties

In this work, N,N′-diaryl-perylene-3,9-diamine (PDA) derivatives featuring different alkoxyl substituents at para position of the N-aryl rings were synthesized and employed as emitters in solution processed organic light emitting diodes.

Synthesis and optical properties of soluble low bandgap poly (pyrrole methine) with alkoxyl substituent

A soluble low bandgap poly (pyrrole methine) with alkoxyl substituent, poly {(3-hexanoyl)pyrrole-[2,5-diyl(p-tetradecyloxybenzylidene)]} (PHPDTBE), was synthesized and characterized by 1H nuclear magnetic resonance (1H-NMR), Fourier transform-infrared (FT-IR), elemental analysis (EA) and gel permeation chromatography (GPC). PHPDTBE was readily soluble in weak polar organic solvents. The absorption peaks of PHPDTBE solution and film were located at around 458 and 484 nm, respectively. The optical bandgaps of PHPDTBE film for indirect allowed and direct allowed transitions were measured to be 1.66 and 2.35 eV, respectively. PHPDTBE film had few defects in the energy band and the Urbach energy of PHPDTBE film was calculated to be about 0.19 eV. The resonant third-order nonlinear optical susceptibilities of PHPDTBE solution and film measured by degenerate four-wave mixing (DFWM) technique at 532 nm were all in the order of 10–8 esu, which was about 1~3 orders of magnitude larger than that of the other ordinary π-conjugation polymers.

Synthesis and antifungal activity of 3-substituted imidazo[1,2-b][1,2,4,5]tetrazines

A number of new 3-substituted imidazo[1,2-b][1,2,4,5]tetrazines containing azolyl, aminopyridyl, and alkoxyl substituents was synthesized. These compounds were studied for the biological activity against mycelial anthropophilic and zoophilous dermatophyte fungi (Trichophyton, Microsporum and Epidermophyton), causing diseases of skin and its appendages (hair, nails), and yeast-like fungi Candida.

Optimization of 2-phenylcyclopropylmethylamines as selective serotonin 2C receptor agonists and their evaluation as potential antipsychotic agents.

The discovery of a new series of compounds that are potent, selective 5-HT2C receptor agonists is described herein as we continue our efforts to optimize the 2-phenylcyclopropylmethylamine scaffold. Modifications focused on the alkoxyl substituent present on the aromatic ring led to the identification of improved ligands with better potency at the 5-HT2C receptor and excellent selectivity against the 5-HT2A and 5-HT2B receptors. ADMET studies coupled with a behavioral test using the amphetamine-induced hyperactivity model identified four compounds possessing drug-like profiles and having antipsychotic properties. Compound (+)-16b, which displayed an EC50 of 4.2 nM at 5-HT2C, no activity at 5-HT2B, and an 89-fold selectivity against 5-HT2A, is one of the most potent and selective 5-HT2C agonists reported to date. The likely binding mode of this series of compounds to the 5-HT2C receptor was also investigated in a modeling study, using optimized models incorporating the structures of β2-adrenergic receptor and 5-HT2B receptor.

Tetraphenylethene modified [n]rotaxanes: synthesis, characterization and aggregation-induced emission behavior.

A series of novel [n]rotaxanes based on a tetraphenylethene (TPE) backbone were constructed by a template-directed clipping approach and their structures were well-characterized. Investigation of their optical properties showed that these rotaxanes and their corresponding ammonium salts showed aggregation-induced emission (AIE) behavior. However, there were obvious differences as follows: (1) rotaxanes reached the aggregation state in the presence of less water compared with the corresponding ammonium salt; (2) the rotaxanes with a long alkoxyl chain on the pyridine unit of the crown ether formed the aggregation state in the presence of less water than for those without an alkoxyl substituent and (3) a smaller distance between the TPE unit and N-hetero crown ether component resulted in the aggregation state being reached more easily than when there is a longer distance. The results suggest that the mechanically interlocked structures can adjust the aggregation state of AIE molecules.

Synthesis and Characterization of Novel Soluble Fulleropyrrolidine Derivatives and Their Photovoltaic Performance

Currently, [60] fullerene derivatives are the focus of considerable research due to their important roles in many fields, especially material science. In this study, we synthesized the following two novel fulleropyrrolidine derivatives: C60-fused N-methyl-(4-hexyloxybenzen-2-yl) pyrrolidine, (p-HOPF) and C60-fused N-methyl-(2-hexyloxybenzen-2-yl) pyrrolidine, (o-HOPF). Structural assignments of the two fullerene derivatives were made through 1H NMR and FAB-MS. We also measured the optical and electrochemical properties of p-HOPF and o-HOPF through UV/Vis spectrophotometry and cyclic voltammetry. We found that the difference in the position of the alkoxyl substituent on the phenyl ring greatly affects the characteristics of the molecules. In particular, from the 1H NMR spectrum, we found that the hydrogen atoms on the carbons adjacent to the oxygens in p-HOPF and o-HOPF have completely different chemical environments. In order to study the effects of the substituent group positions on photovoltaic performance, photovoltaic devices were fabricated. The highest power conversion efficiency, 0.71%, was achieved when using o-HOPF as the electron acceptor.

Synthesis and ring-opening reaction of novel 1,3-dehydroadamantanes possessing phenyl and alkoxyl substituents

A series of novel 1,3-dehydroadamantanes (DHAs) possessing phenyl or alkoxyl substituents, such as 5-phenyl-1,3-dehydroadamantane, 5-butyl-7-phenyl-1,3-dehydroadamantane, 5-methoxy-1,3-dehydroadamantane, 5-butoxy-1,3-dehydroadamantane, 5-butyl-7-methoxy-1,3-dehydroadamantane, and 5-butoxy-7-butyl-1,3-dehydroadamantane were synthesized and subjected to react with acidic compounds. 1,3-Dibromoadamantanes carrying phenyl or alkoxyl substituents were converted into the corresponding DHAs via the intramolecular Wurtz-type coupling reactions with lithium metal in THF in 23–62% yields. Ring-opening reactions of DHAs readily occurred with acetic acid or methanol under acidic conditions to form various 1-acetoxyadamantanes or 1-methoxyadamantanes containing phenyl or alkoxyl groups. The resulting 1-butyl-3-methoxy-5-phenyladamantane, 1-acetoxy-3-butyl-5-phenyladamantane, 1-acetoxy-3-butyl-5-methoxyadamantane, 1-acetoxy-3-butoxy-5-butyladamantane, and 1-butoxy-3-butyl-5-methoxyadamantane possessed stereogenic center. The high reactivity of the inverted 1,3-carbon–carbon σ-bond in DHAs toward the acidic compounds indicated the high electron density, which was supported by the sp2 character of cyclopropane rings in DHAs estimated by JC–H coupling constants in the 13C NMR analyzes.

Synthesis and characterization of simple trans-AB-porphyrins for dye-sensitized solar cells

Four simple trans-AB-porphyrins 3a–3d either without any alkoxyl substituent, or with a mono-alkoxyl chain at different (ortho and para) positions of the meso-phenyl ring, or with two alkoxyl chains at two ortho positions of the meso-phenyl ring were designed and synthesized via three steps. The synthesis is simple and no expensive metal catalyst is involved. All compounds were characterized by 1H-NMR and mass spectraometry. UV-Vis absorption spectra and B band-excited fluorescence emission spectra were also obtained. The synthesized porphyrins were applied in dye-sensitized solar cells (DSSCs). Up to 3.05% conversion efficiency was realized for 3d under our experimental conditions, attributed to the two long alkoxyl chains present at the ortho positions of the meso-phenyl group. The influences of the position and the number of the alkoxyl chains at the macrocyclic meso-phenyl group on the photovoltaic performance of DSSCs are well explained via DFT calculations. It was shown that the VOC and JSC of the sensitizers are determined by μnormal, ΔGinject and LHE.

Synthesis and Characterization of Novel PPV Derivatives

Five kinds of poly(phenylene vinylene) (PPV) derivatives with different alkoxyl substituents were synthesized with optimized synthesis procedures. The optimized PPV derivatives are reacted at 80°C for 6 h after mixing of the reactants at 45°C, and then followed by aging at 95°C for 1 h. The optimized molar ratios of dichlorobenzyl chloride/potassium tert-butoxide for poly(2-methoxy-5-butoxy)-p-phenylene vinylene and poly(2,5-dibutyloxy)- 1,4-phenylene vinylene are 1/7 and 1/8, respectively. The yields of the derivatives increased gradually with the chain length of the substituents; however, the yields decreased with a further increase in the chain length to an eight-carbon substituent, which is resulted from the counteraction of the electronic effect by the steric effect of the substituents. The solubility of the derivatives was greatly enhanced with the incorporation of the alkoxyl substituents, and the highest solubility of 3.08% in chloroform and 1.79% in tetrahydrofuran is demonstrated by poly(2-methoxy-5-octyloxy)-p-phenylene vinylene (PMOOOPV). All derivatives exhibited higher solubility in chloroform than in tetrahydrofuran. The conductivity of the derivatives increased with increasing of the substituting chain lengths as a result of the enhanced the conjugation degree and lowered energy gap, and the highest conductivity of 2.9 × 10−4 S/cm was exhibited by PMOOOPV. © 2012 Wiley Periodicals, Inc. Adv Polym Techn 32: E603–E611, 2013; View this article online at wileyonlinelibrary.com. DOI 10.1002/adv.21304