Spacer Chain Length Research Articles

Experimental and theoretical studies of physicochemical properties of Gemini imidazolium ionic liquids: hydroxyl group in spacer chain and alkyl chain length of cation

Experimental and theoretical studies of physicochemical properties of Gemini imidazolium ionic liquids: hydroxyl group in spacer chain and alkyl chain length of cation

Elucidating effect of dicarboxylate anions on nanostructural organization of dicationic imidazolium-based ionic liquids

This work reports the influence of the dicarboxylate anion (oxalate, malonate succinate, glutarate, adipate, pimelate) on the aggregation process of ionic liquids derived from 1,8-bis(3-methylimidazolium-1-yl)-octane [C8(MIM)2] and 1,10-bis(3-methylimidazolium-1-yl)-decano [C10(MIM)2] in water solution. The aggregation behavior was investigated using electrical conductivity, nuclear magnetic resonance, transmission electron microscopy, atomic force microscopy, and zeta potential. Results showed that the aggregates have a wormlike morphology. The CAC values for [C10(MIM)2]2+ increase in the following order: [Oxa] < [Suc] < [Mal] < [Glu] < [Adi] < [Pim], which indicates a direct relationship with the increase in the number of methylene groups of the dianion spacer. In the case of [C8(MIM)2]2+, there was no relationship between the CAC value and the anion’s alkyl spacer chain length, which was attributed to the flexibility and complexity of the dynamic behavior of the aggregates. Anions on the nanorganized structures of micelles are oriented in the way that carboxylate groups are at the aggregate surface (forming hydrogen bonds with cationic heads and water), and apolar alkyl chains are in the hydrophobic (downshift) region of the micelles making an arrangement where they also adopt the bend conformation of alkyl chains. The aggregation of dicationic ILs with dicarboxylate anions is a very innovative topic of investigation in the literature, and more research on different structures, system conditions, and techniques could be done to gain a better understanding of these systems.

Understanding the Role of Ligand Structure on Extraction of Neptunium by N-Pivot Tripodal Diglycolamides in an Ionic Liquid

ABSTRACT The extraction of Np4+ was studied by a series of N-pivot tripodal diglycolamides, with varying substituents (alkyl groups with varying branching and chain length) and varying spacer length, dissolved in an ionic liquid, i.e. [C4mim][Tf2N]. Out of a series of four ligands, L I (propylene spacer) and L II (ethylene spacer) differ only in the spacer length connecting the three diglycolamide units with the tripodal N platform. While L II – L IV have the same spacer length (ethylene spacer), but L II has a hydrogen atom, L III has methyl group, and L IV has isopropyl group as a substituent at the amidic N atom close to the central N atom. A reversal extraction mechanism of Np4+ was observed when the spacer chain length reduced from a propylene group in L I to an ethylene group in L II – L IV . While a cation-exchange mechanism was observed in case of L I , a solvation extraction mechanism was seen for the other three ligands with the extracted species being Np(NO3)2(L)2+ for L I , and [Np(NO3)4·L] for L II – L IV . The extraction efficiencies of Np4+ with L II – L IV were significantly affected by the nature of the alkyl substituents and follow the order: L II > L III > L IV . This trend in the extraction pattern affirms that the alkyl substitution at the amidic N atom creates steric strain in the ligand while complexing with the metal ion.

Regulation of the quantum barrier and carrier transport toward high-efficiency quasi-2D Dion-Jacobson tin perovskite solar cells

Quasi-2D Dion-Jacobson (DJ) tin halide perovskite has attracted much attention due to its elimination of Van der Waals gap and enhanced environmental stability. However, the bulky organic spacers usually form a natural quantum well structure, which brings a large quantum barrier and poor film quality, further limiting the carrier transport and device performance. Here, we designed three organic spacers with different chain lengths (ethylenediamine (EDA), 1,3-propanediamine (PDA), and 1,4-butanediamine (BDA)) to investigate the quantum barrier dependence. Theoretical and experimental characterizations indicate that EDA with short chain can reduce the lattice distortion and dielectric confinement effect, which is beneficial to the effective dissociation of excitons and the inhibition of trap-free non-radiative relaxation. In addition, EDA cation shows strong interaction with the inorganic octahedron, realizing large aggregates in precursor solution and high-quality films with improved structural stability. Furthermore, femtosecond transient absorption proves that EDA cations can also weaken the formation of small n-phases with large quantum barrier to achieve effective carrier transport between different n-phases. Finally, the quasi-2D DJ (EDA)FA9Sn10I31 solar cells achieves a 7.07% power conversion efficiency with good environment stability. Therefore, this work sheds light on the regulation of the quantum barrier and carrier transport through the chain length of organic spacer for quasi-2D DJ lead-free perovskites.

Clarifying the role of carboxyl functionality in squaraines towards aggregation and self-assembly through photophysical characterization and BSA interactions

The demand for near-infrared (NIR) probes with robust and stable fluorescence signals has surged, driven by their applications in optical sensing and bioimaging. Squraine dyes as NIR fluorescent probes have gained significant traction. However, understanding their behavior in aqueous media is important for their successful application. Herein we report the synthesis and photophysical characterization of carboxy-functionalized unsymmetrical squaraine dyes capable of light absorption and emission in the near-infrared (NIR) wavelength region. Structural variations in alkyl chain length, and spacer chain length between the primary chromophore and –COOH group were systematically introduced to investigate their impact on self-assembly in aqueous media leading to dye aggregation and their differential interactions with Bovine Serum Albumin (BSA) as a model protein. In phosphate buffer (PB) the absorption intensity decreased drastically along with pronounced shoulders due to dye aggregation leading to complete fluorescence quenching. However, in the presence of BSA, the intensity of shoulder bands reduced coupled with a sharp increase in the absorption associated with monomeric dye with the increasing concentration of BSA, indicating the prevention of dye aggregation owing to dye-BSA interactions. The prevention of dye aggregation due to dye-BSA interaction also led to a tremendous increase in the fluorescence intensities as a function of the increasing BSA concentrations. Site-selective study off BSA showed that these dyes bind preferably at Site-II using hydrophilic interactions. Thus, these dyes show great potential as FRET or fluorescent on/off probes for biosensing, non-covalent labeling of proteins, and fluorescent probes for bioimaging.

Structural Analysis of Aggregates Formed by Linear- and Star-type Quaternary Ammonium Salt-Based Trimeric Surfactants Using Rheology and Small-Angle X-ray Scattering.

We performed a structural analysis of aggregates formed by two types of trimeric surfactants based on quaternary ammonium salts─linear-type 3Cnlin-s-Q and star-type 3Cntris-s-Q─featuring varying alkyl chain lengths (n) and spacer chain lengths (s) in aqueous solutions. We performed rheology, dynamic light scattering, and small-angle X-ray scattering measurements on the trimeric surfactants and investigated the effects of the alkyl chain length, spacer chain length, spacer skeleton structure, and surfactant concentration on their aggregation behavior. Linear-type 3C12lin-3-Q transitioned from gel solutions to worm-like micelles at high concentrations, and 3C14lin-3-Q became gel solutions over a wide range of concentrations. In contrast, all other studied surfactants formed ellipsoidal micelles. The minor and major axes of the ellipsoidal micelles formed by liner-type 3Cnlin-3-Q increased with the increasing alkyl chain length. As the spacer chain length of 3Cnlin-s-Q increased from 3 to 6, and as the spacer skeleton expanded from linear-type 3Cnlin-s-Q to star-type 3Cntris-s-Q, the surfactants formed ellipsoidal micelles without the formation of aggregates with a high-order structure, demonstrating this behavior over a broad concentration range.

Ionic strength and phase systems influence nanotubular material functionality

We synthesized novel thiacyanine chromonic liquid crystals (CLCs) and structurally characterized using NMR and mass spectrometry. The impact of distinct substitution at the para position of aromatic counter anions, aliphatic counter ion chain length, and varied spacer parity of thiacyanine dyes on CLC formation is investigated. Liquid crystal properties of the synthesized dyes are characterized by polarizing optical microscopy (POM) and X-ray diffraction (XRD) studies. Dyes exhibit nematic (N), lamellar (Lα), columnar rectangular (Colr), and columnar oblique (Colob) CLCs at different concentrations in the water. Electronic absorption spectra reveal Scheibe aggregation in all the dyes. Cylicvoltametry studies confirm redox behaviour in TC-1a and TC-5e dyes. Chromonic LCs hybrid nano-materials are synthesized using sol–gel method. Scanning electron microscopy employed to confirm nano tubular fiber structure of the hybrid nanomaterilals..

Synthesis and application of novel Gemini esterquats in fabric softeners: Role of spacer chain length on surfactant properties

AbstractGemini surfactants are dimeric molecules having two monomeric units connected by a spacer. Gemini surfactants, owing to their molecular structure have better surfactant properties than other monomeric surfactants. Esterquat class gemini surfactants can be synthesized using a spacer containing ester linkages. In the current study, the synthesis of novel esterquat gemini surfactants was carried out with spacers of varying chain lengths and was characterized using sophisticated instrumental methods. Various surfactant properties including foaming, emulsification, CMC, surface excess, antimicrobial activity and wetting potential using contact angle were analyzed and compared with benzalkonium chloride. It was observed that the CMC as low as 24.79 × 10−3 mM of the synthesized surfactants is potentially lower than that of conventional monomeric surfactants and was found to increase with an increase in spacer chain length. Further, the applicability and evaluation of performance properties of the synthesized surfactants were studied in fabric softener formulation. The water absorbency and whiteness retention of the formulation prepared using 12‐6‐12 GS was the highest due to its better wettability amongst other synthesized surfactants owing to its higher spacer chain length. To summarize, the surface and anti‐microbial properties of the synthesized surfactants vary greatly with the alteration in spacer chain length.

Photophysical Characterization and Biointeractions of NIR Squaraine Dyes for in Vitro and in Vivo Bioimaging.

The increasing demand for reliable near-infrared (NIR) probes exhibiting enduring fluorescence in living systems and facile compatibility with biomolecules such as peptides, antibodies or proteins is driven by the increasing use of NIR imaging in clinical diagnostics. To address this demand, a series of carboxy-functionalized unsymmetrical squaraine dyes (SQ-27, SQ-212, and SQ-215) along with non-carboxy-functionalized SQ-218 absorbing and emitting in the NIR wavelength range were designed and synthesized followed by photophysical characterization. This study focused on the impact of structural variations in the alkyl chain length, carboxy functionality positioning, and spacer chain length on dye aggregation and interaction with bovine serum albumin (BSA) as a model protein. In phosphate buffer (PB), the absorption intensity of the dyes markedly decreased accompanied by pronounced shoulders indicative of dye aggregation, and complete fluorescence quenching was seen in contrast to organic solvents. However, in the presence of BSA in PB, there was a enhancement in absorption intensity while regaining the fluorescence coupled with a remarkable increase in the intensity with increasing BSA concentrations, signifying the impact of dye-BSA interactions on preventing aggregation. Further analysis of Job's plot unveiled a 2:1 interaction ratio between BSA and all dyes, while the binding studies revealed a robust binding affinity (Ka) in the order of 107/mol. SQ-212 and SQ-215 were further tested for their in vitro and in vivo imaging capabilities. Notably, SQ-212 demonstrated nonpermeability to cells, while SQ-215 exhibited easy penetration and prominent cytoplasmic localization in in vitro studies. Injection of the dyes into laboratory mice showcased their efficacy in visualization, displaying stable and intense fluorescence in tissues without toxicity, organ damage, or behavioral changes. Thus, SQ-212 and SQ-215 are promising candidates for imaging applications, holding potential for noninvasive cellular and diagnostic imaging as well as biomarker detection when coupled with specific vectors in living systems.

Understanding the influence of ethylene glycol on the microscopic behavior of imidazolium-based monocationic and dicationic ionic liquid

In the present work, the influence of a molecular co-solvent, ethylene glycol (EG) on the microscopic behaviour of an imidazolium-based dicationic ionic liquid (DIL) is analysed by employing time-resolved fluorescence anisotropy (TRFA) and nuclear magnetic resonance (NMR) spectroscopic techniques. In order to have a clear understanding of the specific role of DIL, a mono-cationic ionic liquid (MIL) containing an alkyl side chain unit, same as the alkyl spacer chain length of DIL, has also been investigated. The rotational diffusion of two fluorescent probes 9-PA and R110 have been carried out in both neat MIL and DIL and their mixtures with various fractions of EG. The analysis of the results has demonstrated that, within the studied concentration range, the microstructure of MIL encompassing both polar and nonpolar domains gets disrupted as the mole fraction of EG increases. However, a similar investigation in DIL has revealed that the micro-structure of DIL gets affected slightly when similar proportions of EG are added to DIL. This behaviour of DIL is attributed to the enhanced rigidity of the DIL structure due to its folded structural arrangements. Furthermore, NMR studies have provided additional insights into the interactions between the components of ILs and the added solvent. It has been observed that EG can form strong hydrogen-bonding interactions with the imidazolium-ring and alkyl chain protons of MIL. However, such interaction has not been observed in DIL. Moreover, the translational diffusion coefficient (Dt) value for the cationic moiety of both MIL and DIL, measured through NMR, has depicted that in the presence of EG, the change in Dtvalue is much higher for MIL than that for DIL. Overall, the outcome of the combined fluorescence and NMR studies have pointed out that the behaviour of DIL and MIL in the presence of a co-solvent is very different from one another and thus the individual mixture (IL+solvent) can be used for various targeted industrial applications.

Self-aggregation of cationic gemini surfactants with amide groups in the spacer and variable alkyl chain length

AbstractSynthesis, aggregation parameters and antimicrobial activity of novel cationic gemini surfactants with two amide groups in gemini spacer structure and a variable number of carbon atoms in alkyl tails ranging from 12 to 15 are reported. The critical micelle concentration of gemini surfactants was determined using surface tension and electrical conductivity methods. The cmc values were found in the range 0.83 to 0.06 mM. The interfacial area, micelle ionisation degree and the Gibbs free energy per molecule and alkyl chain were calculated from the surface tension and conductivity curves. Particle size analysis using the dynamic light scattering method confirmed the formation of small spherical micelles 6–7 nm large in size for gemini surfactants with 12 and 13 carbon atoms in the alkyl chain. A large size above 50 nm was found for the aggregates composed of long-chain gemini molecules with 14 and 15 carbon atoms. The zeta potential of gemini surfactants shows a continuous increase with the increasing alkyl chain length. Micelle aggregation number of gemini surfactants correlates well with the hydrodynamic size data. Small aggregation number values were found for short-chain gemini molecules with 12 and 13 carbon atoms in the alkyl chain. Long-chain gemini molecules with 14 and 15 carbon atoms exhibit aggregate growth represented by an increase in the aggregation number values while maintaining the spherical or spheroidal shape of micelles. The investigations of antimicrobial activity against Gram-positive bacteria, Gram-negative bacteria and yeast indicate the increasing antimicrobial efficiency towards the short-chain surfactant with 12 carbon atoms in the alkyl chain. A possible cut-off effect presence is proposed to explain the dependence of antimicrobial activity on the surfactant alkyl tail length.

Self-Aggregation, Antimicrobial Activity and Cytotoxicity of Ester-Bonded Gemini Quaternary Ammonium Salts: The Role of the Spacer.

Five ester-bonded gemini quaternary ammonium surfactants C12-En-C12 (n = 2, 4, 6), with a flexible spacer group, and C12-Bm-C12 (m = 1, 2), with rigid benzene spacers, were synthesized via a two-step reaction and analyzed. Furthermore, the effects of the spacer structure, spacer length and polymerization degree on the self-aggregation, antimicrobial activity and cytotoxicity of C12-En-C12 and C12-Bm-C12 and their corresponding monomer N-dodecyl-N,N,N-trimethyl ammonium chloride DTAC were investigated. The results showed that C12-En-C12 and C12-Bm-C12 had markedly lower critical micellar concentration (CMC) values and lower surface tension than DTAC. Moreover, the CMC values of C12-En-C12 and C12-Bm-C12 decreased with increasing spacer length. In the case of equivalent chain length, the rigidity and steric hindrance of phenylene and 1,4-benzenediyl resulted in larger CMC values for C12-Bm-C12 than for C12-En-C12. The antibacterial ability of C12-En-C12 and C12-Bm-C12 was assessed using Escherichia coli (E. coli) and Staphylococcus albus (S. aureus) based on minimum inhibitory concentrations (MICs). Furthermore, C12-En-C12 and C12-Bm-C12 exhibited higher antimicrobial activity than DTAC and had stronger function toward S. aureus than E. coli. The antimicrobial activity was enhanced by increasing the spacer chain length and decreased with the increased rigidity of the spacers. The cytotoxic effects of C12-En-C12 and C12-Bm-C12 in cultured Hela cells were evaluated by the standard CCK8 method based on half-maximal inhibitory concentration (IC50). The cytotoxicity of C12-En-C12 and C12-Bm-C12 was significantly lower than alkanediyl-α,ω-bis(dimethyldodecylammonium) bromide surfactants and DTAC. The spacer structure and the spacer length could induce significant cytotoxic effects on Hela cells. These findings indicate that the five ester-bonded GQASs have stronger antibacterial activity and lower toxicity profile, and thus can be used in the pharmaceutical industry.

Flexible, Linear, and Systematically Expanded Tetraphosphonate Bolaamphiphiles and Their Inhibition Performance against Calcite and Barite Scale Formation

Oilfield scaling is one of the most prevalent water-based oilfield production problems. Chemical inhibitors are often used to combat and prevent scale deposition. The phosphonate functional group is commonly used in many scale inhibitors. A series of bolaamphiphilic alkyldiamine tetrakis(methylenephosphonic acid)s have been synthesized from 1,X-diamines, where X in the polymethylene spacer groups has an even number of 2–12 carbon atoms. These inhibitors were coined CX-T (X is the number of C atoms between the N atoms on the inhibitor backbone, and T stands for tetraphosphonates). All tetraphosphonates showed excellent compatibility with calcium ions at 100 ppm or less, i.e., normal scale inhibitor dosage levels. At higher dosages, the calcium concentration and length of the alkylene spacer chain between the nitrogen atoms also determine the compatibility. Crystal structures were determined for the calcium “complexes” with the tetraphosphonates C2-T, C4-T, C6-T, and C8-T. All tetraphosphonates were investigated for calcite and barite scale inhibition under dynamic conditions using oilfield produced waters based on the Heidrun field water composition, offshore Norway. For calcite scaling, tetraphosphonates with ethylene (2 carbons) and hexamethylene (6 carbons) spacer groups gave the best inhibition performance. For barite scaling, the best inhibition was observed for the tetraphosphonates with ethylene and tetramethylene spacer groups, which relates to the ability of both disphosphonate moieties to interact with a single barium ion.

Adsorption dynamics of quaternary-ammonium-salt–based gemini and trimeric surfactants with different spacer structures at air/water interface

The dynamic surface tensions of gemini surfactants with spacers containing cyclic structures such as diethylene and triethylene chains, and atoms such as oxygen and nitrogen, and of linear- and star-type trimeric surfactants with spacers having propylene or hexylene chains between the quaternary ammonium groups (for the linear-type) and propylene or hexylene chains between the quaternary ammonium group and the central amino group (for the star-type) were measured using the maximum bubble pressure method. The effects of the molecular structures and surfactant concentration on the maximum rate of reduction in the surface tension as well as the diffusion coefficient were elucidated. The gemini surfactants containing cyclic structures in the spacer exhibited slower interfacial adsorption, which was ascribed to their rigid spacer structure. The longer the spacer chain length of the gemini surfactants, the greater the molecular flexibility and hence the faster the adsorption at the interface. Thus, the diffusion and adsorption of gemini surfactants are affected by the rigidity and hydrophobicity of the spacer, respectively. However, the adsorption of the trimeric surfactants at the air/water interface (which resulted in a maximum rate of reduction in the surface tension of 0.0007–0.004 mN m–1 s–1) was lower than that of the gemini surfactants (which resulted in a maximum rate of reduction in the surface tension of 0.0009–0.9 mN m–1 s–1). This was ascribed to the greater bulkiness of trimeric structures compared with those of the gemini surfactants. The star-type trimeric surfactants adsorbed faster at the air/water interface than the linear-type trimeric surfactants because the former were flexible despite their bulky spacer structure. For the linear- and star-type trimeric structures, the diffusion rate increased with the spacer chain length because of the resulting increase in the molecular flexibility. The linear-type surfactants were adsorbed faster at the air/water interface as their spacer chain length was increased, whereas the star-type surfactants were adsorbed more slowly because of their molecular bulkiness.

Characterization of Micelle Formation by the Single Amino Acid-Based Surfactants Undecanoic L-Isoleucine and Undecanoic L-Norleucine in the Presence of Diamine Counterions with Varying Chain Lengths

The binding of linear diamine counterions with different methylene chain lengths to the amino-acid-based surfactants undecanoic L-isoleucine (und-IL) and undecanoic L-norleucine (und-NL) was investigated with NMR spectroscopy. The counterions studied were 1,2-ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, and 1,6-diaminohexane. These counterions were all linear diamines with varying spacer chain lengths between the two amine functional groups. The sodium counterion was studied as well. Results showed that when the length of the counterion methylene chain was increased, the surfactants’ critical micelle concentrations (CMC) decreased. This decrease was attributed to diamines with longer methylene chains binding to multiple surfactant monomers below the CMC and thus acting as templating agents for the formation of micelles. The entropic hydrophobic effect and differences in diamine counterion charge also contributed to the size of the micelles and the surfactants’ CMCs in the solution. NMR diffusion measurements showed that the micelles formed by both surfactants were largest when 1,4-diaminobutane counterions were present in the solution. This amine also had the largest mole fraction of micelle-bound counterions. Finally, the und-NL micelles were larger than the und-IL micelles when 1,4-diaminobutane counterions were bound to the micelle surface. A model was proposed in which this surfactant formed non-spherical aggregates with both the surfactant molecules’ hydrocarbon chains and n-butyl amino acid side chains pointing toward the micelle core. The und-IL micelles, in contrast, were smaller and likely spherically shaped.

Preparation of a Monovalent-Selective Anion-Exchange Membrane: Effect of Alkyl Chain Length and Crystallinity

Crosslinked anion-exchange membranes (AEMs) with reasonable water uptake are used for the separation of monovalent anions from their mixture with bivalent anions by electrodialysis (ED). Herein, we report the preparation of a series of monovalent-selective crosslinked AEMs containing imidazole rings from the polyacrylonitrile-co-poly(vinylimidazole) (PAN-co-PVIm) copolymer (AN/VIm ratio = 75:25 mol/mol), followed by N-alkylation with alkyl halide of different chain lengths (carbon number: 1,6,10,18), followed by reaction with 1,6-diamino hexane. The difference in the obtained permselectivity (PSO42–Cl–) was compared with those of un-crosslinked and commercial Ionsep membranes. The effects of crosslinking, the chain length of the alkyl spacer attached to imidazolium nitrogen of the membrane matrix, and the partial crystallinity occurring due to the arrangement of long alkyl chains on PSO42–Cl– were investigated. A representative crosslinked membrane (MQ18) with an octadecyl alkyl chain length (C18) attached to the imidazole moiety exhibited moderate water uptake (22%), high fixed charge density (0.037 meq/cm3), and high PSO42–Cl– (6.4) during the separation of a mixture of 0.01 M sodium chloride and 0.01 M sodium sulfate (2000 mg/L) by the ED process. The PSO42–Cl– value is further increased from 6.4 to 16.7 by increasing the electrolyte concentration to 0.05 M sodium chloride and 0.05 M sodium sulfate. The rigid imidazolium structure, locally organized higher chain length of the alkylating group, and the crosslinked network structure provide steric hindrance for the passage of more hydrophilic sulfate anions, which facilitates higher selectivity.

Role of Dual Nature of Ionic Liquid in Solvation Dynamics and Rotational Diffusion in Mixed Micelles: A Time‐Resolved Fluorescence and Fluorescence Anisotropy Study

AbstractThe present work demonstrates the role of the dual nature of an ionic liquid, 1‐dodecyl‐3‐methylimidazolium bromide (C12mimBr), in the solvation dynamics and rotational diffusion of Coumarin 153 (C‐153) in the aqueous mixed micellar solutions of three cationic gemini surfactants, 12‐s‐12,2Br− (where s = 4, 6 and 8) using different spectroscopic and light scattering techniques. Ionic liquid within the micelles controls the weightages of solvation components. In pure micelles of a gemini surfactant, the fast and slow solvation components are major and minor, respectively, which vary based on the concentration of the ionic liquid. The effective solvation rate enhances with increasing concentration of C12mimBr. Dual nature of C12mimBr governs the size of mixed micelles. Thus the associated time constant for rotational motion also alters accordingly. In micelle, lateral diffusion coefficient (DL) value enhances with its increasing size due to mixed micelle's increased porosity. Gemini spacer chain length effect is also discussed.

The effect of position of (-)-menthyl on the mesomorphic and photoisomerization behavior in azobenzene chiral liquid crystals

As the mesomorphic type of liquid crystals could be largely altered by the molecular chirality, we herein explored the effect of position of chiral (-)-menthyl on the mesomorphic and photoisomerization behavior in azobenzene liquid crystals. By modifying the position of chiral (-)-menthyl in the menthol based liquid crystal compounds through gradually increasing the alkyl chain length of the dicarboxylic spacer, seven new chiral liquid crystal compounds 4-(4-menthyloxy-n-oxoalkanoyloxy)-4′-(4-ethoxybenzoyloxy) azobenzene MnAZO2B (n = 2–8) were prepared. A combination of analysis methods was conducted to systematically investigate their structures, mesophase behaviors and optical properties. The length and parity of the flexible spacers has a dramatic influence on the mesomorphic behaviors, and an odd-even effect is observed for these chiral liquid crystal compounds.

Synthesis, Structural and Theoretical Analyses of C≡N···I Halogen-Bonded Liquid Crystalline Complexes of 4-Cyano-4′-alkoxy Biphenyl Systems

A series of 4-cyano-4′-alkoxybiphenyl compounds were synthesized by varying the spacer chain lengths (−CH2−)n, where n = 3–10, for the systematic study of a halogen-bonded (XB) complex with 1,4-diiodotetrafluoro benzene. The XB liquid crystalline complexes obtained from the liquid-assisted grinding method were characterized by FTIR, Raman, DSC, and PXRD studies. Further, C≡N···I XB interaction was established by single-crystal X-ray diffraction analysis. The odd-even analysis has suggested that the even carbon chain length containing XB liquid crystalline complexes shows slightly higher alteration in their isotropic temperature compared to the odd carbon chain lengths of such complexes. Furthermore, it is interesting to note that the higher alkyl chain complexes (n = 6–10) showed liquid crystalline temperature at lower values with respect to their ligands. The Hirshfeld and energy framework analyses have also been carried out to assess the stability and percentage contribution of XB noncovalent interaction. The frontier molecular orbital, noncovalent interaction, molecular electrostatic potential, and QTAIM analysis were performed using DFT to evaluate the nature of XB in these halogen-bonded liquid crystalline systems.

Lipopolysaccharide and statin-mediated immune-responsive protein networks revealed in macrophages through affinity purification spacer-arm controlled cross-linking (AP-SPACC) proteomics.

Toll-like receptor 4 (TLR4), a pattern recognition receptor, is activated by lipopolysaccharides (LPS) and induces the MyD88 pathway, which subsequently produces pro-inflammatory cytokines through activation of transcriptional nuclear factor (NF)-κB. Statins have been widely prescribed to reduce cholesterol synthesis for patients with cardiovascular disease. Statins may have pleiotropic effects, which include anti- and pro-inflammatory effects on cells. The molecular mechanism of the sequential influence of LPS and statin on the innate immune system remains unknown. We employed affinity purification-spacer-arm controlled cross-linking (AP-SPACC) MS-based proteomics analysis to identify the LPS- and statin-LPS-responsive proteins and their networks. LPS-stimulated RAW 264.7 macrophage cells singly and combined with the drug statin used in this study. Two chemical cross-linkers with different spacer chain lengths were utilized to stabilize the weak and transient interactors. Proteomic analysis identified 1631 differentially expressed proteins. We identified 151 immune-response proteins through functional enrichment analysis and visualized their interaction networks. Selected candidate protein-coding genes were validated, specifically squamous cell carcinoma antigens recognized by T cells 3, sphingosine-1-phosphate lyase 1, Ras-related protein Rab-35, and tumor protein D52 protein-coding genes through transcript-level expression analysis. The expressions of those genes were significantly increased upon statin treatment and decreased in LPS-stimulated macrophage cells. Therefore, we presumed that the expression changes of genes occurred due to immune response during activation of inflammation. These results highlight the immune-responsive proteins network, providing a new platform for novel investigations and discovering future therapeutic targets for inflammatory diseases.