Alkyl Chain Substitution Research Articles

Spin‐Crossover and Liquid Crystal Property in Fe(II) Complexes: Impact of Alkyl Chain Lengths

AbstractMaterials that combine spin‐crossover (SCO) and liquid crystal (LC) behavior have gained significant attention due to their potential applications in technological devices, attributed to their easy processability. Herein, we report three neutral heteroleptic Fe(II) complexes: [Fe(dpa‐C4)2(NCS)2] (1), [Fe(dpa‐C6)2(NCS)2] (2), and [Fe(dpa‐C16)2(NCS)2] (3) (dpa‐Cn=N‐alkyl‐N‐(pyridin‐2‐yl)pyridin‐2‐amine; n=4, 6 and 16), which exhibit thermal‐induced spin transition behavior. The transition profiles and temperatures are effectively modulated by the length of the alkyl chains. Longer alkyl chains result in gradual and higher T1/2 values, while the shorter chains lead to abrupt SCO with lower T1/2 (i. e. T1/2=259 K (3) >237 K (2) >211 K (1)). Crystallographic studies reveal the impact of hydrophobic and hydrophilic packing in the crystal lattice, contributing to cooperativity and thereby affecting the SCO behavior. Complex 3 with long alkyl chain substitution, displayed non‐synchronized SCO‐LC behavior due to the thermal motion of the alkyl chains.

Bushy-Tailed QACs: The Development of Multicationic Quaternary Ammonium Compounds with a High Degree of Alkyl Chain Substitution.

Quaternary ammonium compounds have served as a first line of protection for human health as surface disinfectants and sanitizers for nearly a century. However, increasing levels of bacterial resistance have spurred the development of novel QAC architectures. In light of the observed reduction in eukaryotic cell toxicity when the alkyl chains on QACs are shorter in nature (≤10 C), we prepared 47 QAC architectures that bear multiple short alkyl chains appended to up to three cationic groups, thus rendering them "bushy-tailed" multiQACs. Antibacterial activity was strong (often ~1-4 μM) in a varied set of bushy-tailed architectures, though observed therapeutic indices were not significantly improved over QAC structures bearing fewer and longer alkyl chains.

Toxicity of a novel antifungal agent (ATB1651 gel) in Yucatan minipigs (Sus scrofa) following 4weeks of daily dermal administration.

ATB1651 gel is an antifungal drug candidate that enhances antifungal activity through substitution of several aryl rings, alkyl chains, and methyl groups. To ensure safety of use of ATB1651 gel, assessment of its potentially toxic side effects is necessary. In this study, we examined the repeated-dose toxicity of ATB1651 gel to Yucatan minipigs (Sus scrofa) in accordance with the Good Laboratory Practice guidelines. Five doses of ATB1651 gel (0%, 0.2%, 0.5%, 1.0%, 3.0%) were administered dermally to the left and right flanks of 38 minipigs daily for 4weeks. Mortality, clinical symptoms, dermal scores, body weights, and physiological, biochemical, pathological, and toxicokinetic analyses were performed after the treatment period. No systemic toxicological damage was observed in either male or female minipigs regardless of dose; however, dermal application of ATB1651 gel caused some skin alterations at the application sites. Specifically, erythema and eschar formation, edema, and scabs or raise spots were observed at the application site(s) in males in the 3.0% ATB1651 gel treatment group and in females at ATB1651 gel concentrations ≥ 1.0%, with dermal scores ranging from grade 1 to 2. Additionally, histopathological assay indicated infiltration of different types of inflammatory cells and the presence of pustule/crust at the application site(s) in both males and females at ATB1651 gel concentrations ≥ 0.5%. However, these changes were reversible after a 2-week recovery period and were considered a local irritation effect of ATB1651 gel. The no-observed-adverse-effect level of ATB1651 gel was 3.0% with regard to topical and systemic toxicity in both male and female minipigs. Collectively, our results imply that ATB1651 gel is a safe candidate for clinical development as an antifungal drug with a wide therapeutic window.

Permeation of urea and water through sulfonated poly(styrene‐isobutylene‐styrene) membranes with counterion substitution

AbstractThis study describes the influence of counterion substitution on the transport of urea and water through sulfonated poly(styrene‐isobutylene‐styrene) (SIBS) membranes. SIBS was sulfonated to 66.4% to allow for enough ionic domains to transport urea and water through the membrane. Counterions, including alkyl‐substituted ammonium ions, influenced the ionic domains creating a selective barrier that hindered the transport of urea and water through SIBS. Permeability measurements demonstrated that counterion substitution significantly affected the transport of urea. Membranes with higher charge counterions exhibited a more pronounced reduction in permeability due to the formation of crosslinks and increased restriction on molecular diffusion. Membranes substituted with ammonium salts showed reduced permeability due to the alkyl chains' hydrophobic nature, which created a physical barrier against the passage of urea molecules. Pure water flux tests indicated that counterion substitution also reduced the water flux of the membranes. Membranes with +1 counterions showed a small reduction in the water flux, while membranes with higher charge counterions and alkyl chain substitutions exhibited larger reductions, highlighting the influence of crosslinking and hydrophobicity on water transport.

The influence of ionic liquids with heterocyclic cations on CO2 hydrates formation

Kinetic characteristics of CO2 hydrates formation in the presence of eight ionic liquids with heterocyclic cations and [PF6]- anion were experimentally investigated here. It is found that the imidazolium ionic liquids with short substituted alkyl chains can inhibit CO2 hydrates formation. Increasing the alkyl chain length can alleviate the nucleation inhibition effect, and 1-hexadecyl-3-methylimidazolium hexafluorophosphate([C16mim][PF6]) with a concentration of 10 wt% even shows a slight promotion effect comparing to the pure water. In contrast, adding pyrrolidinium, piperidinium and pyridinium ionic liquids increases the nucleation temperatures, shortens the induction times and enhances the CO2 consumption. Based on DFT calculations and MD simulations, it is inferred that the strong binding energy between H2O and 1-ethyl-imidazolium hexafluorophosphate([Emim][PF6]) plays a main role on its inhibition behavior during CO2 hydrates formation. The H2O-H2O RDF curves of N-butyl pyridinium hexafluorophosphate([OPy][PF6]), N-butyl-N-methylpiperidinium hexafluorophosphate([PP14][PF6]) and N-butyl-N-methylpyrrolidinium hexafluorophosphate([PY14][PF6]) aqueous systems exhibit three peaks which become intensified and narrow with time, while [Emim][PF6]-containing system only has a single peak due to its strong interaction with water and thus inhibits the water-water attraction. In addition, RDF peaks of H2O–[PF6]- become weak gradually with time, implying that the anion [PF6]- does not engage in the structures of water cages.

A newly fascinating approach to construct pillar[5]arene functionalized ester derivatives for nematic liquid crystalline behavior

A Pillar[5]arene linked 4-n-alkoxy benzoic acid based multifunctional supramolecular systems ((PB1-PB4) with variable alkyl chains were synthesized and well characterized. The microscopic and thermal behaviors of the compounds were investigated by using POM, DSC, and TGA analysis. All four pillar[5]arene-ester based macrocyclic compounds display nematic type mesomorphic properties, with a well-known schlieren and droplets type texture pattern observed in all four ten-side substituted pillarene derivatives. All four materials exhibit enantiotropic mesogenic behavior with a wide temperature range and thermal stability. The material with higher alkyl chain exhibit nematic phase at lower temperatures compared to materials with lower alkyl chain substitutions. Furthermore, we have investigated the structure property relationship to understand the influence of substitution on the rigid core of pillar[5]arene and its ability to induce different types of liquid crystalline behaviors.

Modular Bicyclophane-Based Molecular Platforms.

The modular synthesis of a series of nanoscale phenylene bicyclophanes with an intraaanular orthogonal pillar is described. The compounds are obtained by a Suzuki cross-coupling condensation and are characterized by mass spectrometry and NMR spectroscopy as well as in situ scanning tunneling microscopy at the solid/liquid interface of highly ordered pyrolytic graphite. In addition, their structures and conformations are supported by quantum chemical calculations, also after adsorption to the substrate. A set of two alkyl chain substitution patterns as well as a combination of both was investigated with respect to their ability to form extended 2D-crystalline superstructures on graphite. It shows that not the most densely packed surface coverage gives the most stable structure, but the largest number of alkyl chains per molecule determines the structural robustness to alterations at the pillar functionality.

Fine-tuning morphology via oligo(ethylene oxide) side chain engineering for squaraine-based organic solar cells

Two squaraine dyes (SQs), USQ-O bearing oligo(ethylene oxide) (OE) chain, and USQ-C bearing alkyl chain, were synthesized. The influence of OE side chain on photovoltaic performances was systematically investigated. USQ-C and USQ-O show similar absorption spectra in dilute solutions, energy levels, charge mobility and the molecular electrostatic potential (ESP) on the conjugated skeleton. However, USQ-O exhibits hypsochromic absorption band compared to that of USQ-C in the film, and the distribution of positive and negative alternating ESP on the OE side chain. Significantly different electrostatic interactions and multiple hydrogen bonds among OE side chains could greatly affect the behaviors of intermolecular interactions, and, in turn, influence the photophysical properties of pristine/blend films and the miscibility with PC71BM acceptor. USQ-O-based devices exhibit higher short circuit current than that of USQ-C-based (13.94 vs 12.36 mA cm−2), which could be principally put down to the effective improvement of the blending morphology. These results indicate that simply substituted alkyl chain by OE chain for SQ is an effective strategy for optimizing morphology.

Asymmetric side-chain engineering of organic semiconductor for ultrasensitive gas sensing

Molecular structure of organic semiconductor plays a critical role in determining the performance and functionality of organic electronic devices, by optimizing the electrical, optical and physicochemical properties. Substituted alkyl chains are fundamental units in tailering the solubility and assemblability, among which the asymmetric properties have been reported as key element for controlling the packing motifs and intrinsic charge transport. Here, we expanded the scope of molecular asymmetry dependent sensing features based on a new series of naphthalene diimides (NDI)-based derivatives substituted with a same branching alkyl chain but various linear-shaped alkyl chains (Cn-). A clear molecular stacking change, from head-to-head bilayer to head-to-tail monolayer packing model, is observed based on the features of anisotropic molecular interactions with the change in the chain length. Most importantly, a unique LUMO level shift of 0.17 eV is validated for NDI-PhC4, providing a record sensitivity up to 150% to 0.01 ppb ammonia, due to the desired molecular reactivity and device amplification properties. These results indicate that asymmetric side-chain engineering opens a route for breath healthcare.

Coumarin functionalized dimeric mesogens for promising anticoagulant activity: Tuning of liquid crystalline property

This paper demonstrates the synthesis of novel bi-substituted coumarin-based symmetrical compounds (A1-A6)via a simple two-step reaction by conversion of coumarin (I) to dicoumarol (II) followed by the alkylation using different alkyl bromides. The chemical proposed structure was confirmed by IR, NMR, Mass, and CHN analysis. These dimeric materials were further investigated for liquid crystalline properties. The thermal behavior and liquid crystalline properties were evaluated using TGA, DSC, POM, and high temperature XRD. The substitution of various alkyl chains on coumarin core presented a broad scope to achieve different types of liquid crystalline properties. These symmetrical dimers of coumarin derivatives exhibited enantiotropic type mesophase with a broad temperature range and wide thermal stability. The compound with a hexadecyloxy tail exhibited mesogenic properties at room temperature. The lower alkoxy side chain substituted materials presented only nematic phase while higher alkoxy side chain substituted materials displayed smectic type mesogenic properties. The present coumarin-based dimeric mesogens were easily fabricated by simple two-step method as compared to other coumarin-based mesogens. In addition, one of the dicoumarol derivatives showed promising anticoagulant activity. Compound A5 at 10.0 mg/5.0 mL of blood concentration revealed good efficacy as an anticoagulant agent to prevent blood clotting.

Nonlinear Optical Properties of Several π Conjugated Bridge Groups based on Diketo-Pyrrole-Pyrrole: Study on the Length and Symmetry of N-atom Position Substituted Alkyl Chains

In this paper, three modified π-conjugated bridges, were selected to study the relationship between substituted alkyl chains and two photon absorption ability as well as intramolecular charge transfer property. The modification is on the N-atom position of Diketo-Pyrrole-Pyrrole bridges. Some nonlinear optical measurements as well as several spectra methods, were used. DPP-J0, DPP-J1 and DPP-J2 exhibit cross-section of 5.6 GM, 8.1 GM, and 6.4 GM. The results exhibit obvious relation on the length and symmetry of N-atom position substituted alkyl chains. A pump-probe measurement was operated at 800 nm. Ultrafast dynamics results exhibit slight difference on the intramolecular charge transfer of these conjugated bridge derivatives. The quantum chemical calculations results are well accorded with the nonlinear optical properties. The results obtained may provide some useful information on molecular design and optimization of new advanced materials.

Phospholipid-Mimetic Aggregation-Induced Emission Luminogens for Specific Elimination of Gram-Positive and Gram-Negative Bacteria.

Precise elimination of both Gram-positive and Gram-negative bacteria greatly contributes to the fight against bacterial infection but remains challenging. Herein, we present a series of phospholipid-mimetic aggregation-induced emission luminogens (AIEgens) that selectively kill bacteria by capitalizing on both the different structure of two bacterial membrane and the regulated length of substituted alkyl chains of AIEgens. Because of the positive charges that they contain, these AIEgens are able to kill bacteria by anchoring onto the bacterial membrane. For AIEgens with short alkyl chains, they could combine with the membrane of Gram-positive bacteria other than Gram-negative bacteria, because of their complicated outer layers, thus exhibiting selective ablation to Gram-positive bacteria. On the other hand, AIEgens with long alkyl chains have strong hydrophobicity with bacterial membranes, as well as large sizes. This inhibits the combination with Gram-positive bacterial membrane but destroys the membranes of Gram-negative bacteria, resulting in selective ablation to Gram-negative bacteria. Moreover, the combined processes to two bacteria are clearly observed by fluorescent imaging, and in vitro and in vivo experiments show the extraordinary antibacterial selectivity toward a Gram-positive and Gram-negative bacterium. This work could facilitate the development of species-specific antibacterial agents.

Experimental and simulated distribution and interaction of water in cellulose esters with alkyl chain substitutions

This study investigated the effect of the average length of substituted side chains in different cellulose esters on water sorption and the water association mechanism. For this purpose, a set of esters with a similar total degree of substitution was selected: cellulose acetate, cellulose acetate propionate, and cellulose acetate butyrate. Dynamic vapor sorption was used to determine the effect of the side chain length on sorption, desorption, and the occurrence of water clustering. Since water association in the structure was of interest, molecular dynamics simulations were performed on cellulose acetate and cellulose acetate propionate. This study showed that cellulose acetate appears to be water-sensitive and experiences hysteresis upon water sorption, which was attributed to structural changes. The simulations also showed that water is screened out by the side chains and forms intermolecular hydrogen bonds, primarily to the carbonyl oxygen rather than the residual hydroxyl groups.

Tuning the odd-even effect on two-dimensional assemblies of curcumin derivatives by alkyl chain substitution: a scanning tunnelling microscopy study.

Well-ordered molecular arrangement on surfaces is fundamental for fabrication of functional molecular devices which are of particular interest in nanotechnology. In addition to nano-manufacturing, the production of useful materials from natural resources has recently attracted increasing attention. Herein, we focused on the two-dimensional (2D) self-assemblies of curcumin derivatives. The effects of the number, length, and substitution of the alkyl chains on the 2D structures of curcumin derivatives were studied by scanning tunnelling microscopy at the highly oriented pyrolytic graphite/1,2,4-trichlorobenzene interface. Curcumin derivatives containing both methoxy and alkoxy chain groups and those possessing four alkoxy chains exhibit linear structures with and without interdigitation of alkoxy chains, respectively. These 2D structure formations are independent of the alkyl chain length. However, the bisdemethoxycurcumin derivatives periodically form stair-like and linear structures depending on the alkyl chain length, which indicates the existence of the odd-even effect. These results suggest that the 2D structural modulation of curcumin derivatives caused by the odd-even effect can be tuned by the number of alkyl chain substituents. The appearance and disappearance of the odd-even effect in curcumin derivatives are discussed in terms of the balance between intermolecular and molecule-substrate interactions.

Tailored alkyl-imidazolium templating synthesis of extra-large-pore germanosilicate zeolite ITT as Baeyer-Villiger oxidation catalyst

Extra-large-pore germanosilicate zeolite ITT was prepared with several structure-tailored alkyl-substituted imidazolium templates. The effect of alkyl chain length and substitution number of template on zeolite topology structure was studied with the variation of synthesis Si/Ge ratio. 1-hexyl-3-methyl-imidazaolium (1H3M) exhibited superior templating effect on the formation of ITT structure within the widest range of synthesis Si/Ge molar ratio of about 2–6. 1H→13C CP/MAS NMR, TGA and molecular simulation results revealed that two 1H3M was occluded in the 18-ring channels per unit cell, presenting the lowest interaction energy with framework. With the combination of XRD, SEM, EDS, ICP, 29Si, 19F MAS NMR, FTIR, N2 physisorption results, it was found that the increase of synthesis Si/Ge ratio improved framework Si/Ge ratio within d4r unit to a certain degree, and in the meantime resulted in the decrease of zeolite crystallinity with the formation of some amorphous phase. ITT showed better Lewis-acid catalytic activity and lactone selectivity for B–V oxidation of 2-adamantanone than BEC, the best germanosilicate zeolite ever reported. The excellent catalytic performance was ascribed to the presence of 18-ring channels in ITT, which facilitated the diffusion of bulky ketone substrate and lactone product. The structure stability of ITT during the reaction was evaluated with the use of either aqueous H2O2 or non-aqueous tert-butyl hydroperoxide (TBHP) as oxidant.

Two new cyclohexylethanol derivatives from the whole plants of Incarvillea delavayi and their inhibition on LPS-induced NO release in BV-2 cells

Delavatones A (4 β , 7 α -dihydroxy-7 β -(13-methylpent-11-one-12-ene)-octahydrobenzofuran, 1) and B (4 β , 7 α -dihydroxy-7 β -(propan-9-one)-octahydrobenzofuran, 2 ), two structurally unique cyclohexylethanol derivatives with a substituted alkyl chain, were isolated from the 90% ethanol extract of the whole plants of Incarvillea delavayi . The structures of delavatones A and B were characterized by the interpretation of 1D and 2D NMR spectroscopic data in combination with NMR chemical shift calculation coupled with DP4+ probability analysis. In an in vitro assay for anti-inflammatory effect, delavatones A and B displayed remarkable suppression on NO production in LPS-induced BV-2 cells at concentrations ranging from 6 μM to 100 μM. • Two new cyclohexylethanols, delavatones A and B, were isolated from I. delavayi . • Delavatones A and B are two rare cyclohexyethanols with an substituted alkyl chain. • The stereo configurations of delavatones A and B was determined by DP4+ computation. • Delavatones A and B remarkably suppressed LPS induced NO release in BV-2 cells.

Effect of Substituents on the Homopolymerization Activity of Methyl Alkyl Diallyl Ammonium Chloride.

Among nitrogen-containing cationic electrolytes, diallyl quaternary ammonium salt is a typical monomer with the highest positive charge density, which has attracted the most attention, especially in the research on homopolymers and copolymers of dimethyl diallyl ammonium chloride (DMDAAC), which occupy a very unique and important position. In order to improve the lipophilicity of substituted diallyl ammonium chloride monomers under the premise of high cationic charge density, the simplest, most direct, and most efficient structure design strategy was selected in this paper. Only one of the substituents on DMDAAC quaternary ammonium nitrogen was modified by alkyl; the substituents were propyl and amyl groups, and their corresponding monomers were methyl propyl diallyl ammonium chloride (MPDAAC) and methyl amyl diallyl ammonium chloride (MADAAC), respectively. The effect of substituent structure on the homopolymerization activity of methyl alkyl diallyl ammonium chloride was illustrated by quantum chemical calculation and homopolymerization rate determination experiments via ammonium persulfate (APS) as the initiator system. The results of quantum chemistry simulation showed that, with the finite increase in substituted alkyl chain length, the numerical values of the bond length and the charge distribution of methyl alkyl diallyl ammonium chloride monomer changed little, with the activation energy of the reactions in the following order: DMDAAC < MPDAAC < MADAAC. The polymerization activities measured by the dilatometer method were in the order DMDAAC > MPDAAC > MADAAC. The activation energies Ea of homopolymerization were 96.70 kJ/mol, 97.25 kJ/mol, and 100.23 kJ/mol, and the rate equation of homopolymerization of each monomer was obtained. After analyzing and comparing these results, it could be easily found that the electronic effect of substituent was not obvious, whereas the effect of the steric hindrance was dominant. The above studies have laid a good foundation for an understanding of the polymerization activity of methyl alkyl diallyl ammonium chloride monomers and the possibility of preparation and application of these polymers with high molecular weight.

Toxicity studies of select ionic liquids (1-ethyl-3-methylimidazolium chloride, 1-butyl-3-methylimidazolium chloride, 1-butyl-1-methylpyrrolidinium chloride, and n-butylpyridinium chloride) administered in drinking water to Sprague Dawley (Hsd:Sprague Dawley SD) rats and B6C3F1/N mice.

Ionic liquids (ILs) are synthetic solvents with applications in a variety of industrial and chemical industries. Human exposure to this diverse chemical class is primarily through dermal or oral routes. Research suggests toxicity may be associated with IL structural characteristics, including the type of cation base or alkyl chain substitutions associated with the cation. To further investigate this hypothesis, the National Toxicology Program (NTP) conducted 3-month toxicity studies in male and female Sprague Dawley (Hsd:Sprague Dawley SD) rats and B6C3F1/N mice (n = 10/sex/exposure group; 3 exposure concentrations per IL) to compare the relative toxicities of four ILs administered via drinking water-1-ethyl-3-methylimidazolium chloride (Emim-Cl), 1-butyl-3-methylimidazolium chloride (Bmim-Cl), 1-butyl-1-methylpyrrolidinium chloride (Bmpy-Cl), and n-butylpyridinium chloride (NBuPy-Cl). (Abstract Abridged).

Mesophase behaviour of 1,2,3-triazole-based nematic liquid crystals influenced by varying alkyl chains and halogen atom substitution

ABSTRACT To develop novel nematic-phase liquid-crystal (LC) materials with practical potential in optical and photovoltaic devices, the alkyl chain and halogen atom substitution in 1,2,3-triazole-based compounds were varied, and the effects on the mesophase behaviour were investigated. The 4-(4-propylcyclohexyl)phenyl 4-(1-alkyl-5-hydro/halo-1,2,3-triazol-4-yl)benzoate series 1 was successfully synthesised through tandem aerobic oxidative halogenation and click reaction via in situ activation. Except for 5-thiophene-1,2,3-triazole compound 1c-Th displaying no mesomorphism, the other compounds 1 form enantiotropic nematic mesophases, among which compounds 5-hydro-1,2,3-triazole 1c-H (C10) and 1d-H (C12) (long straight chain compounds) form two mesophases (smectic C phase and nematic phase). For 5-halo-1,2,3-triazole compounds 1c-X (× = halide), the mesomorphic temperature range was wider than for the corresponding compound 1c-H because of the effect of the halogen atom substituent on the triazole. Density functional theory (DFT) analysis showed that the structure-property relation for series 1c-X(H) could be defined by using the calculated dihedral angles, dipole moment, polarisability, and molecular electrostatic potential as parameters. Notably, introducing halogen atoms at the 5-position of 1,2,3-triazole can greatly broaden the mesogenic temperature range, ascribed to the weak intermolecular forces and large dipole moment in this class of compounds.

Screening of hydrogen bonds in modified cellulose acetates with alkyl chain substitutions

This study aimed to elucidate how the glass transition temperature and water interactions in cellulose esters are affected by the structures of their side chains. Cellulose acetate, cellulose acetate propionate and cellulose acetate butyrate with three fractions of butyrates, all having the same total degree of substitution, were selected, and hot-melt pressed. The degree of substitution, structural properties, and water interactions were determined. The Hansen solubility parameters were calculated and showed that the dispersive energy dominates the total cohesive energy, followed by hydrogen bonding and polar energy. The glass transition temperature (Tg) decreased, counter-intuitively, with an increased total cohesive energy, which can be explained by the short-range hydrogen bonds being screened by the increased length of the substituents. The solubility and penetration of water in the cellulose esters decreased with increased side chain length, although the hydrogen bonding energies for all the esters were approximately constant.