Elongation Of Alkyl Chain Research Articles

Asymmetrical Elongation of Branched Alkyl Chains in Non‐Fullerene Acceptors for Large‐Area Organic Solar Modules

AbstractWith the drive toward the development of large‐area organic solar cells (OSCs), there is a critical need for advanced fabrication techniques that ensure both their efficiency and scalability. In particular, a shift from toxic halogenated solvents to safer non‐halogenated alternatives such as o‐xylene, which have lower environmental and health impacts, is required. However, transitioning to non‐halogenated solvents can lead to serious problems, including aggregation within the active layer, which compromises film morphology and the resulting efficiency of OSCs. To address this aggregation, in the present study, the 2‐ethylhexyl (EH) groups in L8‐BO(EH‐EH) are replaced with longer chains (2‐heptylundecyl [HU], 2‐decyltetradecyl [DT], and 2‐dodecylhexadecyl [DH] groups) to synthesize the non‐fullerene acceptors (NFAs) of L8‐BO(HU‐HU), L8‐BO(HU‐DT), and L8‐BO(HU‐DH). The NFAs with the longer alkyl chains are highly soluble in o‐xylene and produce highly uniform films, making them more suitable for use in large‐area OSCs. Using the NFAs, slot‐die‐coated organic solar modules with an active area of 200 cm2 are fabricated; the L8‐BO(HU‐DT)‐based module exhibits an impressive power conversion efficiency of 11.44%. This work thus underscores the asymmetrical elongation of alkyl chains in the NFAs to mitigate severe NFA phase separation and improve film printability in the practical production of organic solar modules.

On the dependence of electrical mobility on temperature, humidity and structure of alkylammonium ions

Insights into the effect of temperature (T) and relative humidity (RH) as well as structure and polarisation on ion mobility help the comparison and interpretation of mobility and mass-based data. We measured alkylammonium ions in air under different T (14 °C, 24 °C, 34 °C and 41 °C) and RH (0 %, 20 %, 40 %) conditions using two individual setups (in both cases a planar differential mobility analyser coupled with a time-of-flight mass spectrometer) and the results are in excellent agreement. Mobility increases with rising T and decreases with water vapour loading. When separating the measurement mobility by structures, clear mass dependence was observed. The measured mobilities exhibited large deviations from theoretically calculated results in dry conditions, which are possibly caused by adduct formation on the monomer ions via clustering (or reactions). This phenomenon seems to be unavoidably associated with light ions under atmospheric pressures, which is worth further exploration and bearing in mind when comparing measurements to calculations. Both methanol and oxygen (occasionally nitrogen or alkyl chain elongation) are possible candidates of the adduct. Under spherical assumption, we used the modified Mason–Schamp's approximation to link the measured mobility to the mobility equivalent diameter. The drag enhancement factor ξ and the effective gas-molecule collision diameter dg derived from our measurement data are comparable to literature values. Our data also exposed a non-linear dependence on the polarisation parameter ε*. Polarisation, ξ and dg were parameterised using linear models against ion structures, T, and RH for primary, secondary and tertiary alkylammonium ions with identical alkyl groups. Our model parametrisations predict mobilities within ±10 % deviation from the measured data. The model also has satisfying predicting power for alkylammonium ions with unidentical alkyl structures.

Ionic Liquid Interface as a Cell Scaffold.

In sharp contrast to conventional solid/hydrogel platforms, water-immiscible liquids, such as perfluorocarbons and silicones, allow the adhesion of mammalian cells via protein nanolayers (PNLs) formed at the interface. However, fluorocarbons and silicones, which are typically used for liquid cell culture, possess only narrow ranges of physicochemical parameters and have not allowed for a wide variety of cell culturing environments. In this paper, it is proposed that water-immiscible ionic liquids (ILs) are a new family of liquid substrates with tunable physicochemical properties and high solvation capabilities. Tetraalkylphosphonium-based ILs are identified as non-cytotoxic ILs, whereon human mesenchymal stem cells are successfully cultured. By reducing the cation charge distribution, or ionicity, via alkyl chain elongation, the interface allows cell spreading with matured focal contacts. High-speed atomic force microscopy observations of the PNL formation process suggest that the cation charge distribution significantly altered the protein adsorption dynamics, which are associated with the degree of protein denaturation and the PNL mechanics. Moreover, by exploiting dissolution capability of ILs, an ion-gel cell scaffold is fabricated. This enables to further identify the significant contribution of bulk subphase mechanics to cellular mechanosensing in liquid-based culture scaffolds.

Bisphosphonium cation based metal halide glass scintillators with tunable melting points.

Organic-inorganic metal halide (OIMH) glass offers the advantages of large-scale production, high transparency, and minimal light scattering. However, undesired crystallization in OIMH glass can occur, leading to deteriorated transparency. Herein, a series of bisphosphonium organic cations were designed to construct Mn-based metal halide crystals with a photoluminescence quantum yield (PLQY) near unity, alongside the development of highly thermally stable OIMH glasses. Two strategies were employed to lower the melting point of OIMH: alkyl chain elongation and fluorine substitution. The (Hex-3,4-2F)MnBr4·MeOH (Hex-3,4-2F = hexane-1,6-diylbis((3,4-difluorobenzyl)diphenylphosphonium)) crystal delivers a glass transition temperature of 100 °C and the highest T g/T m ratio (0.82) among OIMHs. The resulting OIMH glass exhibits a PLQY of 47.6%, achieves an impressive resolution of 25 lp mm-1 in X-ray imaging, and remains transparent even after being heated at 90 °C for six weeks. These bisphosphonium-based OIMH glasses present a feasible design for the practical application of OIMH glasses in radiation detection.

Cholinium-Based Ionic Liquids as Promising Antimicrobial Agents in Pharmaceutical Applications: Surface Activity, Antibacterial Activity and Ecotoxicological Profile.

Cholinium-based ionic liquids are compounds increasingly studied in pharmaceutics and biomedicine to enhance bioavailability in drug delivery systems and as bioactive ingredients in pharmaceutical formulations. However, their potential as antimicrobial agents has scarcely been investigated. Herein, we explored the antimicrobial activity of a series of surface-active cholinium-based ionic liquids (Chol-ILs). For this purpose, Chol-ILs with alkyl chains of 10-16 carbon atoms were synthesized and their self-assembly in aqueous medium was investigated. Subsequently, their antimicrobial activity against a panel of clinically relevant bacteria and their ability to eradicate MRSA and P. aeruginosa PAO1 biofilms was evaluated. Finally, we analyzed the ecotoxicological profile of Chol-ILs in terms of susceptibility to aerobic biodegradation and acute aquatic toxicity against D. magna and V. fisheri. Our results reveal that cholinium-based ILs with alkyl chain lengths ≥12 C show a broad spectrum of antibacterial activity. Their antimicrobial efficacy depends on their hydrophobicity, with the C14-C16 homologs being the most effective compounds. These ILs exhibit antimicrobial activity similar to that of imidazolium ILs and quaternary ammonium antiseptics. Moreover, the longer alkyl chain Chol-ILs are able to eradicate established biofilms at concentrations as low as 16-32 µg/mL. The biodegradation rate of cholinium-based ILs decreases with alkyl chain elongation. Our results reinforce the suitability of Chol-ILs as promising multifunctional compounds for application in pharmaceutical and biomedical formulation.

Synthesis and Surface Properties of Piperidinium-Based Herbicidal Ionic Liquids as a Potential Tool for Weed Control

A series of piperidinium-based herbicidal ionic liquids (HILs) were synthesized and investigated. The designed HILs, obtained with high yields, consisted of cation 1-alkyl-1-methylpiperidinium with surface activity and a commercially available herbicidal anion: (3,6-dichloro-2-methoxy)benzoates (dicamba). The above-mentioned compounds were characterized in terms of surface activity and phytotoxicity. Preliminary results were obtained at higher wettability for all HILs when compared to the wettability of commercial Dicash, with HIL having 18 atoms in the carbon chain being the best effectiveness in wetting surfaces (weeds and crop leaves), whereby a drop of HILs with short alkyl chains (C8-C10) could not slide down a leaf. Our findings present that wettability or mobility of HILs drops varied depending on the plant species. Moreover, in this study, by zeta potential and atomic force microscopy measurements, we provide conclusive evidence to demonstrate that alkyl chain elongation plays a significant role in the evolution of surface properties of HILs.

Effect of Alkyl Chain Elongation on Thermophysical Properties of 1-Alkyl-3-vinylimidazolium Bromide-Based Ionic Liquids and Salts

Effect of Alkyl Chain Elongation on Thermophysical Properties of 1-Alkyl-3-vinylimidazolium Bromide-Based Ionic Liquids and Salts

Cytotoxicity of asymmetric mononuclear silver(I)-N-heterocyclic carbene complexes against human cervical cancer: Synthesis, crystal structure, DFT calculations and effect of substituents

A new series of asymmetrical N,N’-disubstituted benzimidazolium derived N-heterocyclic carbene (NHC) ligands and their mononuclear silver(I)-NHC complexes are reported. The ligands were prepared from N-alkylation of 1-methylbenzimidazole with alkyl bromides (n = 10-18 in even parity), non-fluorinated or fluorinated benzyl bromides. In situ deprotonation of the ligands with silver oxide, followed by metathesis reaction with potassium hexafluorophosphate facilitated the formation of the mononuclear silver(I)-NHC complexes. Chemical structures of all the compounds were elucidated using Fourier transform infrared, 1H and 13C nuclear magnetic resonance (NMR) spectroscopy, and CHN elemental microanalysis. The coordination mode of the Ag(I)-NHC complexes was confirmed by single crystal XRD analysis. Single crystal analysis of ortho-fluorinated benzyl-containing complex showed that each complex consisted of one Ag(I) ion coordinated with two NHC ligands in a linear geometry in the presence of one PF6− anion in the lattice. Cytotoxic effects of the NHC ligands and their silver(I) complexes against human cervical cancer cells (HeLa) and normal human skin fibroblasts (Hs27) were investigated using the MTT assay. Cytotoxicity of these compounds was dependent on the N-substituents in the benzimidazolium moiety and the presence of silver ions. Benzylated ligands were non-active whilst their dialkylated analogues showed weak to excellent cytotoxic effects on HeLa cells. The incorporation of silver ions and elongation of alkyl chains significantly enhanced cytotoxicity. Density functional theory revealed that Ag–C bond strength was insensitive to the NHC ligand design, and about one-third of the overall complex binding enthalpy was contributed by the non-covalent interaction between the long alkyl chains. Long-chain ligands (n = 16-18) and all silver(I)-NHC complexes exhibited superior cytotoxicity against HeLa cells (IC50 ranged between 1.18 µM–9.38 µM) as compared to that of the anticancer drug, Etoposide (IC50 = 25.67 µM).

Mechanism of Methyldehydrofosmidomycin Maturation: Use Olefination to Enable Chain Elongation.

Utilization of mononuclear iron- and 2-oxoglutarate-dependent (Fe/2OG) enzymes to enable C-H bond functionalization is a widely used strategy to diversify the structural complexity of natural products. Besides those well-studied reactions including hydroxylation, epoxidation, and halogenation, in the biosynthetic pathway of dehydrofosmidomycin, an Fe/2OG enzyme is reported to catalyze desaturation, alkyl chain elongation, along with demethylation in which trimethyl-2-aminoethylphosphonate is converted into methyldehydrofosmidomycin. How this transformation takes place is largely unknown. Herein, we characterized the reactive species, revealed the structure of the reaction intermediate, and used mechanistic probes to investigate the reaction pathway and mechanism. These results led to the elucidation of a two-step process in which the first reaction employs a long-lived Fe(IV)-oxo species to trigger C═C bond installation. During the second reaction, the olefin installed in situ enables C-C bond formation that is accompanied with a C-N bond cleavage and hydroxylation to furnish the alkyl chain elongation and demethylation. This work expands the reaction repertoire of Fe/2OG enzymes by introducing a new pathway to the known C-C bond formation mechanisms utilized by metalloenzymes.

Influence of Alkyl Chain Length on Thermal Properties, Structure, and Self-Diffusion Coefficients of Alkyltriethylammonium-Based Ionic Liquids.

The application of ionic liquids (ILs) has grown enormously, from their use as simple solvents, catalysts, media in separation science, or electrolytes to that as task-specific, tunable molecular machines with appropriate properties. A thorough understanding of these properties and structure–property relationships is needed to fully exploit their potential, open new directions in IL-based research and, finally, properly implement the appropriate applications. In this work, we investigated the structure–properties relationships of a series of alkyltriethylammonium bis(trifluoromethanesulfonyl)imide [TEA-R][TFSI] ionic liquids in relation to their thermal behavior, structure organization, and self-diffusion coefficients in the bulk state using DSC, FT-IR, SAXS, and NMR diffusometry techniques. The phase transition temperatures were determined, indicating alkyl chain dependency. Fourier-transformed infrared spectroscopy studies revealed the structuration of the ionic liquids along with alkyl chain elongation. SAXS experiments clearly demonstrated the existence of polar/non-polar domains. The alkyl chain length influenced the expansion of the non-polar domains, leading to the expansion between cation heads in polar regions of the structured IL. 1H NMR self-diffusion coefficients indicated that alkyl chain elongation generally caused the lowering of the self-diffusion coefficients. Moreover, we show that the diffusion of anions and cations of ILs is similar, even though they vary in their size.

Spectroscopic and electrochemical properties of thiophene-phenylene based Shiff-bases with alkoxy side groups, towards photovoltaic applications

The influence of presence and elongation of alkoxy side chains in the π-conjugated Schiff-bases has been considered on the basis of UV–Vis absorption and photoluminescence spectra of model compounds and polymers solutions in chloroform and binary solvents of different polarity. The results of these investigations have been supported by electrochemical data. It has been demonstrated that introduction of electron donating methoxy side groups decreases the energy gap, however the elongation of alkyl chains only slightly affects the electronic structure of model compounds. In the case of polymers, such octyloxy side chains improves the solubility, enabling formation of longer polymer chains, with the enhanced effective π-conjugation length and narrower energy gap, however the intensity of emission band clearly decreased. Positive solvatochromism has been observed in both absorbance and photoluminescence spectra for all investigated compounds. As the concluding task, bulk-heterojunction (BHJ) photovoltaic (PV) structures, consisting of polyazomethines blended with the fullerene derivative, [6,6]-phenyl-C61-butyric acid methyl ester (PCBM) have been prepared and tested in the context of potential application in solar cells. All investigated polymers have shown the photovoltaic effect, but the best power conversion efficiency and other PV parameters have been obtained for polyazomthine with octyloxy side chains.

Synthesis, inhibitory activity and in silico docking of dual COX/5-LOX inhibitors with quinone and resorcinol core

Based on the significant anti-inflammatory activity of natural quinone primin (5a), series of 1,4-benzoquinones, hydroquinones, and related resorcinols were designed, synthesized, characterized and tested for their ability to inhibit the activity of cyclooxygenase (COX-1 and COX-2) and 5-lipoxygenase (5-LOX) enzymes. Structural modifications resulted in the identification of two compounds 5b (2-methoxy-6-undecyl-1,4-benzoquinone) and 6b (2-methoxy-6-undecyl-1,4-hydroquinone) as potent dual COX/5-LOX inhibitors. The IC50 values evaluated in vitro using enzymatic assay were for compound 5b IC50 = 1.07, 0.57, and 0.34 μM and for compound 6b IC50 = 1.07, 0.55, and 0.28 μM for COX-1, COX-2, and 5-LOX enzyme, respectively. In addition, compound 6d was identified as the most potent 5-LOX inhibitor (IC50 = 0.14 μM; reference inhibitor zileuton IC50 = 0.66 μM) from the tested compounds while its inhibitory potential against COX enzymes (IC50 = 2.65 and 2.71 μM for COX-1 and COX-2, respectively) was comparable with the reference inhibitor ibuprofen (IC50 = 4.50 and 2.46 μM, respectively). The most important structural modification leading to increased inhibitory activity towards both COXs and 5-LOX was the elongation of alkyl chain in position 6 from 5 to 11 carbons. Moreover, the monoacetylation in ortho position of bromo-hydroquinone 13 led to the discovery of potent (IC50 = 0.17 μM) 5-LOX inhibitor 17 (2-bromo-6-methoxy-1,4-benzoquinone) while bromination stabilized the hydroquinone form. Docking analysis revealed the interaction of compounds with Tyr355 and Arg120 in the catalytic site of COX enzymes, while the hydrophobic parts of the molecules filled the hydrophobic substrate channel leading up to Tyr385. In the allosteric catalytic site of 5-LOX, compounds bound to Tyr142 and formed aromatic interactions with Arg138. Taken together, we identified optimal alkyl chain length for dual COX/5-LOX inhibition and investigated other structural modifications influencing COX and 5-LOX inhibitory activity.

Synthesis and self-assembly of benzothiadiazole-cored α-cyanostilbene hexacatenar mesogens

ABSTRACT A novel series of biscyanovinyl diphenylbenzothiadiazole-based polycatenars with 3,4,5-trialkoxyl benzene units at both ends were synthesized in high yield. The terminal alkyl chain length had great effect on the self-assembly properties. Upon terminal alkyl chain elongation, these compounds showed a mesophase transition from Colrec/p2 mm phase to Colhex/p6 mm phase in their bulk states and could aggregate into organogels with complex morphologies varying from 2D nanosheets via partial spheres to absolute 3D spherical flower-like morphologies. The results indicated that changing the alkyl chain length could tune supramolecular assembly nanostructures of the polycatenars effectively.

The first mesomorphic benzimidazolium-based silver(I)-N-heterocyclic dicarbene complexes: Synthesis, characterization and phase properties

The first mesomorphic benzimidazolium based mononuclear silver (I) N-heterocyclic dicarbene complexes, Ag(I)-NHC were prepared via in situ deprotonation of 1-octadecyl-3-alkyl/arylbenzimidazolium salts with silver oxide (Ag2O). Both series of Ag (I)-NHC complexes contained a C18 alkyl chain on one N atom and differed in term of the substituent (alkyl and substituted benzyl moiety) on the other N atom in the benzimidazolium ring. All the synthesized compounds were characterized by elemental analysis, Fourier-transform infrared, 1H and 13C NMR spectroscopy. Cation geometry, anion and alkyl chain length were found to be essential parameters for mesophase formation in the salts and Ag(I)-NHC complexes in this study. All dialkylated salts except the one with the shortest chain, n = 10 were smectogenic. On the other hand, a large width-to-length ratio of the cationic core in the benzyl analogues had a negative effect on the formation and stability of mesophase. No mesophases were observed for these compounds. Wider mesophase range was seen with decrease in anion size and elongation of alkyl chains. A metastable SmA phase was observed in two Ag(I)-NHC complexes. The minimum chain length required for compounds with different anions to exhibit liquid crystal (LC) properties was addressed. Mesophase was observed for bromide salts with C12 onwards while C14 is the minimum chain length required for the hexaflurophosphate containing Ag(I)-NHC complexes to display LC properties. All Ag(I)-NHC complexes except the one bearing a cyano group could be considered ionic liquids with melting/clearing temperatures below 100 °C.

Influence of the alkyl chain length on the physicochemical properties and biological activity in a homologous series of dichlorprop-based herbicidal ionic liquids

This study focused on the synthesis and subsequent characterization of a homologous series of herbicidal ionic liquids (HILs) that incorporate a 2-(2,4-dichlorophenoxy)propionate (dichlorprop) anion and 1-alkyl-1-methylpiperidinium cation with a varied alkyl length from ethyl to octadecyl. Novel derivatives of dichlorprop were synthesized in high yields (≥90%) via a simple and eco-friendly two-step procedure. Subsequently, the obtained ionic liquids were subjected to analyses of their physicochemical properties (density, viscosity, refractive index, thermal decomposition profiles, octanol-water partition coefficient and solubility) and an evaluation of their herbicidal activity under greenhouse conditions. Generally, all the products possess great thermal stability and hydrophobicity; however, their affinities to various organic solvents were affected by the length of the alkyl substituent. Moreover, the densities and refractive indices of the ionic liquids containing middle-length alkyl chains (from hexyl to decyl) decreased with alkyl chain elongation. All the synthesized ionic liquids maintained biological activity against selected dicotyledonous weeds, including common lambsquarters, cornflower and oilseed rape. Among the tested ionic liquids, the products with dodecyl and octadecyl groups had the highest herbicidal efficacy against all plants. The octanol-water partition coefficients of these new herbicides indicated their low potential for bioaccumulation in the soil and for leaching into groundwater, which minimizes their adverse impacts on the environment.

Experimental evaluation and thermodynamic modelling of AILs alkyl chain elongation on methane riched gas hydrate system

In this study, the thermodynamic inhibition of CH4 rich binary mixed hydrate system (70-30 mol% CH4 + CO2) is reported for four ammonium based ionic liquids (AILs) via experimental and modelling approaches. The T-cycle technique applied for the characterization of the AILs namely tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide (TEAOH), tetrapropyl ammonium hydroxide (TPrAOH) and tetrabutylammonium hydroxide (TBAOH). The hydrate liquid-vapour equilibrium (HLwVE) conditions of studied systems measure within the temperature and pressure ranges of 275.0–286.0 K and 3.0–7.50 MPa respectively at 10 wt% aqueous AILs solutions. All the studied AILs except TBAOH inflicted the THI influence by shifting the HLwVE of CH4 enrich mixed gas hydrates. Elongation in AILs alkyl chain length attributed to decrease the average hydrate suppression temperature (ΔŦ). At 10 wt%, TMAOH exhibited the maximum inhibition impact with a ΔŦ value of 1.28 K, followed by TEAOH (0.8 K), TPrAOH (0.7 K), and TBAOH (−0.84 K) respectively. Instead of hydrate inhibitor, TBAOH worked as gas hydrate promotor owing to the presence of relatively higher alkyl chain cation (butyl) make it semi-clathrate hydrate. The study further extended for different concentrations (1, 5 and 10 wt%) of TMAOH among the best considered AIL in this study. COSMO-RS investigation is also incorporated to further understand the thermodynamic inhibition behaviour of AILs via sigma profile analysis. Additionally, the enthalpies of hydrate dissociation for all studied AILs systems also calculated via Clausius-Clapeyron equation in this study. The calculated hydrate dissociation enthalpies data revealed that all the studied AILs except TBAOH show insignificant participation in mixed gas hydrate cage formation, therefore, do not form semi-clathrate hydrates. However, enthalpy data of TBAOH revealed that it participated in hydrate crystalline structure, therefore, worked as semi-clathrate hydrate. Furthermore, the HLwVE predictions of studied systems also performed via electrolyte based model proposed by Dickens and Quinby-Hunt and found in respectable agreement with the experimental data.

Impacts of ammonium based ionic liquids alkyl chain on thermodynamic hydrate inhibition for carbon dioxide rich binary gas

In this work, the thermodynamic inhibition impact of four ammonium-based ionic liquids (AILs) on CO2 rich mixed gas hydrate system (70–30mol% CO2+CH4) is experimentally studied, and the observed behaviour is modelled. The studied AILs are; tetramethylammonium hydroxide (TMAOH), tetraethylammonium hydroxide (TEAOH), tetrapropylammonium hydroxide (TPrAOH) and tetrabutylammonium hydroxide (TBAOH). Initially, the impact of 10wt% AILs in an aqueous solution on the CO2 enriched binary gas phase boundary is evaluated by measuring the dissociation temperature in the pressure range of 1.90–5.10MPa. The thermodynamic inhibition influence of AILs is quantitatively analyzed by calculating the hydrate suppression temperatures for all studied systems. Further, the Clausius–Clapeyron equation is used to determine the molar hydrate enthalpy of dissociation (∆Hdiss) for the studied systems. The results revealed that the inhibition influence of AILs is observed to be decreasing with the increasing alkyl chain length of AILs. Excluding TBAOH, all the other studied AILs act as thermodynamic inhibitors due to the relatively shorter alkyl chain. The ∆Hdiss results of the binary mixed gas system in the presence and absence of AILs revealed that the presence of TMAOH, TEAOH and TPrAOH has negligible effect in hydrate cages formation. However, TBAOH exhibited a significant change in ∆Hdiss which indicates the semi-clathratic nature of it. Among the considered AILs, TMAOH shown better thermodynamic impact attributed to its shortest alkyl chain length. Therefore it is further investigated for various concentrations (1, 5 and10wt%). Moreover, the measured, mixed gas hydrate phase boundaries of various aqueous AILs solutions are also predicted via electrolyte model proposed by Dickens and Quinby-Hunt and are found to be in good agreement with the experimental data apart from TBAOH. Therefore, this study is relevant for the understanding of structural variations (alkyl chain elongation) of AILs on the hydrate phase stability of the high CO2 content mixed gas system.

Alkyl chain elongation and acyl group effects in a series of Eu/Tb complexes with hexadentate π-electronic skeletons and their enhanced luminescence in solutions.

Five Eu complexes with long alkyl chain groups, abbreviated as EuLCx ("x" indicates the number of methylene groups: x = 8, 12, 14, 18, and 22), were synthesized to evaluate their structural and luminescence properties in chloroform. The mother helicate Eu complex, EuL, which has two bipyridine moieties bridged by an ethylenediamine, has been previously reported. A reduced form in which the azomethine groups of L also coordinated to the Eu ion, EuLH, was newly prepared. EuLH also adopts a helicate molecular structure based on single crystal X-ray structural analysis. The amine hydrogens of the bridging ethylenediamine of LH are active sites for substitution and were exchanged with five different alkyl chains to form EuLCx. Luminescence band positions and shapes of EuLCx in chloroform were completely identical, with a quantum yield of 37.1 ± 1.2 and a lifetime of around 1.25 ms. This indicates that the environments surrounding the Eu ion in the various complexes are all similar. Luminescence quantum yields of TbLH and TbLC18 are also strengthened, 48.7% in acetonitrile and 55% in chloroform, respectively. Potential energy surfaces were also described by using density functional theory, suggesting the possibility of a 1 : 2 complex of Eu and the ligand as a main luminescent species in solutions. This 1 : 2 complexation forms Eu-oxygen coordination using acyl groups. It indicates that the acyl group modification results in a different structure from the mother complexes.

Synthesis and characterization of new mesogenic esters derived from 1,2,4-oxadiazole and study the effect of alkoxy chain length in their liquid crystalline properties

ABSTRACTIn this study, a new series of non-symmetrically 3,5-disubstituted of 1,2,4-oxadiazole derivatives, 4-[5-(4-methylphenyl)-1,2,4-oxadiazol-3-yl]-phenyl-4-alkoxybenzoate (G1–G11), which containing ether and ester linkages in the same molecule, is synthesized using different synthetic procedures and their structures are confirmed by several spectroscopic techniques (FT-IR and 1H nuclear magnetic resonance). The mesomorphic properties of these compounds are studied by differential scanning calorimetry (DSC) and polarized optical microscopy (POM); all these derivatives exhibited as mesogens and displayed an enantiotropic liquid crystal with nematic texture, the nematogenic phase of these materials was appeared in wide temperature ranges on heating and cooling cycles that were observed by POM and DSC. The influence of 1,2,4-oxadiazole ring and the elongation of alkyl chain in the mesomorphic properties of this series were investigated. The mesogenic behaviour of this series was compared with the compounds possessing a somewhat similar structure.

STM Exploration of the Diverse Polymorphs for Tri‐Substituted Anthraquinone Derivatives via Alkyl Chain Elongation

Fabrication of structural diversity in self‐assembled monolayers has gained considerable attention, not only due to its significance in interface science but also because of its potential application in designing nanomaterials. Here, systematical characterization of the molecular self‐assembly of tri‐substituted anthraquinone derivatives at the 1‐octanoic acid/HOPG interface is provided. Different nanopatterns of Linear I, Butterfly‐like, and Linear II are recorded for 1,2,4‐A‐3OC16 by gradually changing the solution concentration. Diverse polymorphs are also obtained by alkyl chain elongation, meaning that 1,2,4‐A‐3OC15,17,18 adopt Dimer‐Linear, Linear III, and Linear IV structures, respectively. Dipole–dipole, hydrogen bonding, and van der Waals interactions are the dominant forces on forming the stable adlayers. Also, the coadsorption of the solvent molecules is a common phenomenon, ascribing to space matching and gain of enthalpy. Moreover, the 1,2,4‐A‐3OC17,18 self‐assembled into monolayers consists of both ordered and chaotic domains. This loss of regularity is attributed to the large number and long length of the side chains, for entropy reasons. This work provides important insight into the fabrication of complex molecular self‐assembly and the exploration of monolayers at the liquid/solid interface.