Larger Alkyl Research Articles

Automatization of theoretical kinetic data generation for tabulated TS models building - Part II: 1,2 to 1,5-H-shift reactions in alkyl radicals

Branched alkanes make up a significant fraction of sustainable alternative fuels. The accurate chemical kinetic modeling of the pyrolysis and oxidation of those fuels requires the availability of accurate kinetic data for branched structures. The accurate theoretical calculation of these data for substituted cyclic transition states (TS) is a challenge because of the large number of configurations that can be created, especially in the larger TS cycles. These configurations originate from all the possible combinations of the orientations of the substituents (axial or equatorial) on the cyclic TS and diastereomers in the reactants, which makes the rigorous counting of the multiple parallel pathways complicated. In this paper, the isomerisation reactions of branched alkyl radicals are theoretically investigated using the code presented in the Part I of this paper series. The 1,2 to 1,5-H-shift reactions are studied within the tabulated transition state models approach, where chain substituents are represented by methyl groups, and all combinations of substitutions in the model TSs are included in a table with their computed rate constants. The rate constants computed for hundreds of reactions with our code demonstrate the necessity to consider all the TS configurations in order to get accurate data. The presence of spectator substituents in the cyclic transition state is shown to have a major impact on the rate constants, increasing their values by more than a factor of 10 for some cases. The tabulated TS models (TMTS) method is validated by comparisons with available experimental data in the literature and is one of the only approach able to accurately capture the impact of branching on the rate constants of isomerizations for large alkyl radicals, which are still difficult to calculate with high-level on-the-fly ab initio calculations.

Dielectric Elastomer Network with Large Side Groups Achieves Large Electroactive Deformation for Soft Robotic Grippers

AbstractDielectric elastomer actuators (DEAs) face an acknowledged challenge: On the one hand, the majority of elastomers only achieve small electroactive deformation (<20%) in the absence of prestretch; on the other hand, rare elastomers capable of showing large electroactive deformation require relatively complicated processing and chemistry. This work addresses this challenge by fabricating an elastomer with a network of large side groups, which achieves a very large electroactive deformation (218%) without pre‐stretch. This elastomer can be rapidly and massively fabricated within a few min, by polymerizing a commercial monomer with a large alkyl side group. The large side groups in the polymer network repel each other and extend the load‐bearing strands, which results in a pronounced strain‐hardening behavior. This behavior helps the elastomer to get rid of electromechanical instability during actuation and hence to exhibit a large electro‐active deformation, a high energy density (>> human muscle), and a large output force (≈500 times self‐weight). the elastomer capable of manufacturing a soft electroactive gripper is demonstrated with large deformation, large force, and rapid response, which enables grasping fragile objects of various complex shapes in an agile away.

Effective prevention of structure II gas hydrate formation using the newly synthesized kinetic inhibitors

Gas hydrate deposition is a complex issue with significant implications for the oil and gas industry. The formation of solid gas hydrates in the hydrocarbon transportation pipelines leads to production disruptions and potentially even complete blockages, resulting in huge financial losses and operational difficulties. For over two decades, kinetic gas hydrate inhibitors have played a crucial role in preventing the formation of gas hydrates within the flow lines of oil and gas production. They directly influence the kinetics of hydrate formation, hindering nucleation and slowing down crystal growth. In this study, five new waterborne polyurethanes (WPUs) with varying degrees of hydrophobicity as inhibitors for cubic structure II gas hydrates were synthesized and tested using rocking cells and differential scanning calorimetry. The synthesis of WPUs involved the reaction between dialkylamines (diethyl, dipropyl, dibutyl, dibenzyl, and dioctyl) and glycidol under mild conditions. All WPUs effectively prevented gas hydrate formation, and a correlation between their efficiency and the alkyl chain length was observed. The inhibitory efficacy of WPUs increased with the extension of the alkyl chain from ethyl to butyl. WPU-DBuA, featuring butyl groups, exhibited the highest inhibition activity. It provided a subcooling temperature of 12.9 and 15.6 °C at 0.25 and 0.5 wt%, respectively, surpassing commercial samples, such as Luvicap EG and Luvicap 55 W. Additionally, the solutions containing 1 and 2 wt% of WPU-DBu exhibited maximum subcooling temperatures of 16.2 °C and 16.7 °C, respectively, which correspond to a 79.7 % and 85.4 % reduction in gas uptake during hydrate growth compared to pure water. However, the inhibitory power of WPUs diminished with larger alkyl (dioctyl) or aromatic groups (dibenzyl), indicating that dibutyl represents the optimal alkyl length for achieving maximum performance. Moreover, WPUs demonstrated a reduction in hydrate conversion under static conditions, signifying their efficiency when the flow is stopped. WPUs lowered the onset temperature of hydrate formation from 3 °C in pure water to temperatures below −12 °C. Thus, WPUs demonstrated a remarkable ability to prevent the formation of structure II gas hydrates, even under high subcooling conditions. Additionally, WPU-DBuA exhibits a considerable degree of biodegradability, as evidenced by its biodegradation level of 44 %, suggesting that it has the potential to break down more easily in the environment compared to Luvicap 55 W. This research contributes to a deeper understanding of the structure–property relationships of KHIs. This can facilitate the development of more effective and eco-friendly inhibitors, which helps address environmental concerns associated with using KHIs in the oil and gas industry.

Noncovalent Interactions in Crowded Benzene Systems: How Much Strain Is Too Much? Attractions Overcome Repulsions!

AbstractIn molecular design, large alkyl groups are used to introduce bulk and steric crowding of the catalytic center to improve catalytic efficiency and selectivity. The bulky groups are highly polarizable, increasing their ability to participate in stabilizing noncovalent interactions. The rationalization of noncovalent interaction trends is of both fundamental and practical interest as it provides new design concepts for catalysis and synthesis. Highly congested molecules always present challenges to chemists. Crowded benzene systems are an important class of compounds with well-established thermodynamic properties. The latter were used in this work to develop tools to quantify the degree of stabilization or destabilization in benzene systems crowded with bulky isopropyl and tert-butyl substituents. The basic idea was to quantify the delicate balance between repulsive and attractive interactions inherent in crowded benzene systems. The ensemble of experimental thermodynamic data and DFT-D3 calculations enabled the development of quantitative scales of the dispersion contributions and their understanding at the molecular level.

Tris(dialkylamino)cyclopropenium dialkylphosphate ionic liquids as lubricants.

Six new tris(dialkylamino)cyclopropenium dialkylphosphate ionic liquids (ILs), [C3(NR2)3]BEHP (NR2 = NEt2, NBuMe, NPr2, NBu2, NHex2, NDec2; BEHP = bis(2-ethylhexyl)phosphate), were prepared and characterised as potential lubricants. Thermophysical and thermochemical properties of these ILs were investigated, namely: viscosity, density, conductivity, miscibility, thermal stability and phase transitions. Miscibility studies indicated that [C3(NEt2)3]BEHP would not be suitable due to its water solubility and hexane immiscibility. [C3(NDec2)3]BEHP was not investigated as a lubricant due to its low purity (the chloride salt of this cation is also hexane miscible). Of the other four, [C3(NHex2)3]BEHP was found to exhibit significantly less wear for pin-on-disk test conditions than the standard phosphonium [P6,6,6,14]BEHP IL. The amount of wear was found to generally decrease with increasing molecular weight.

Quantitative analysis of steric effects on the regioselectivity of the Larock heteroannulation reaction.

Alkylphenylacetylene derivatives were synthesized and used as reactants in the Larock heteroannulation reaction to investigate the steric influence on regioselectivity. Large alkyl groups preferentially yielded 2-alkyl-3-phenylindole products, while smaller alkyl groups provided 3-alkyl-2-phenylindole as major products. The logarithm of regioisomeric product ratios exhibited good correlations with various steric parameters. Notably, the Charton values provided the best correlation when excluding the cyclopropyl group. In addition, the Boltzmann-weighted Sterimol parameter (wSterimol) was utilized to generate a good predictive model, indicating the B1 wSterimol as the significant regiochemical determining parameter with no obvious deviation for the cyclopropyl group. Relative atomic distances within the DFT-optimized transition state structures revealed good correlations with the logarithm of regioisomeric ratios. Furthermore, the cyclopropyl adsorption complex indicated electronic contribution, explaining the peculiar behavior of this substituent in the experimental observation.

Structure-Activity Relationship and Evaluation of Phenethylamine and Tryptamine Derivatives for Affinity towards 5-Hydroxytryptamine Type 2A Receptor.

Among 14 subtypes of serotonin receptors (5-HTRs), 5-HT2AR plays important roles in drug addiction and various psychiatric disorders. Agonists for 5-HT2AR have been classified into three structural groups: phenethylamines, tryptamines, and ergolines. In this study, the structure-activity relationship (SAR) of phenethylamine and tryptamine derivatives for binding 5-HT2AR was determined. In addition, functional and regulatory evaluation of selected compounds was conducted for extracellular signal-regulated kinases (ERKs) and receptor endocytosis. SAR studies showed that phenethylamines possessed higher affinity to 5-HT2AR than tryptamines. In phenethylamines, two phenyl groups were attached to the carbon and nitrogen (R3) atoms of ethylamine, the backbone of phenethylamines. Alkyl or halogen groups on the phenyl ring attached to the β carbon exerted positive effects on the binding affinity when they were at para positions. Oxygen-containing groups attached to R3 exerted mixed influences depending on the position of their attachment. In tryptamine derivatives, tryptamine group was attached to the β carbon of ethylamine, and ally groups were attached to the nitrogen atom. Oxygen-containing substituents on large ring and alkyl substituents on the small ring of tryptamine groups exerted positive and negative influence on the affinity for 5-HT2AR, respectively. Ally groups attached to the nitrogen atom of ethylamine exerted negative influences. Functional and regulatory activities of the tested compounds correlated with their affinity for 5-HT2AR, suggesting their agonistic nature. In conclusion, this study provides information for designing novel ligands for 5-HT2AR, which can be used to control psychiatric disorders and drug abuse.

The Composition and Properties of Soluble Products from the Coal ThermoSolvolysis with Hydrocarbon Residues and Blends as Solvents

The dissolution of bituminous coal at mild temperature was studied using a variety of commercially available coal- and petroleum-derived hydrocarbon fractions, hydrorefined derivatives and blends as solvents. The chemical and molecular composition of the coal, solvents and extracts were characterized by chemical and group analyses, and by IRFT, 1H NMR, GC-MS and liquid chromatography. Low volatile solvents like highly aromatic coal tar (CT), its anthracene fraction (AFCT), petroleum-derived solvent (HGOCC) and binary blends were found to exhibit high performance for coal dissolution into quinoline solubles (to 79‒82%), and the yields of gases being no more than 0.5%. The extracts obtained using CT and AFCT solvents represented pitch-like matter consisting of rarely substituted aromatic molecules with 4‒5 condensed rings. HGOCC extract was much less aromatic, the aromatic rings being highly substituted with fairly large alkyl substituents. The blended solvents yielded more extracts, and their molecular indexes were average between those obtained with each solvent separately. A remarkable finding was that the extracts obtained were characterized by significantly lower content of benzo(a) pyrene (BaP) compared to solvents used, its content further decreased as the time of coal dissolution increased.

Construction of two rosin-based BioAIEgens with distinct fluorescence and mechanochromic propertites for rewritable paper

Mechanochromic materials have been attractive to researchers in recent years due to their wide applications. However, traditional petrochemical-based mechanochromic materials are probably faced with problems of non-renewability and poor sustainability. Hence, it is of great significance to develop mechanochromic materials from phytochemicals endowed with renewability and sustainability. Herein, after combining the tetraphenylethene motif with a rosin-originated phytochemical, dehydroabietic acid, two natural rosin-based aggregation-induced emission (BioAIE) luminogens, DAA-TPE and DAMBA-TPE, were separately obtained on distinct Schiff base reaction sites. Both compounds have AIE phenomena mainly due to the introduction of tetraphenylethene group. However, their other optical properties are totally different depending on the imine site. DAMBA-TPE (imine on the aromatic site of dehydroabietic acid) shows very weak fluorescence at aggregate state, while DAA-TPE (imine on the alkyl site of dehydroabietic acid) exhibits strong emission and high contrast mechanochromic behavior in the solid state. Via the introduction of naturally large alkyl substitution, the pristine powder can be illuminated with a red shift of 28 nm from blue (442 nm) to cyan (470 nm) upon grinding. While a structurally analogue with a small iso-butyl substitution does not possess mechanochromism. Moreover, the fluorescence of DAA-TPE can be reversibly switched, which is most probably attributed to the crystal form change before and after grinding. This property endows DAA-TPE with potential application in the manufacturing of rewritable paper. Last but not least, this work paves a way to the design of mechanochromic materials from naturally renewable resources via introduction of large alkyl groups on the TPE skeleton.

Polymeric micelle/nano hydrogel composite matrix as a novel multi-drug carrier

According to the World Health Organization (WHO), fatality of cancer is 9.6 million in 2018. Of these, 1.8 million deaths are due to colorectal cancer. However, it doesn't seem that proper medications are unavailable. Instead, the medications should reach the site of action without causing any further side effects. With the advent of smart biomaterials this target is on its verge to be achieved. Previous reports prove that the side effects induced by Cisplatin (CIS) could be greatly decreased by curcumin (CUR). Hence, if these two drugs are used in unison, greater efficacy with lesser toxicity could be achieved. However, to incorporate two drugs and to release them simultaneously without any premature leakage can be achieved by polymeric micelles. To increase the core and hydrophobicity, monomers with large alkyl chains like triethylene tetraamine (TETA) and oleic acid (OA) were grafted to the backbone of heparin (HEP) skeleton. To target these drugs, folic acid was entrapped within hydroxyl appetite (HAP) based hydrogel and was dispersed onto polymeric micelle (PM). This coating could further act as a potential barrier to sustain the drug release as evident from similar previous studies. All the reaction steps were monitored using FTIR, XRD, H1 NMR, DLS and SEM studies. The in vitro swelling and release studies proved promising with folic acid showing burst release followed by the sustained release of chemotherapeutic drugs. The efficacy was further ascertained by MTT assay on normal and HCT 116 colon cancer cell lines. This was further proved by fluorescence studies. Thus, the present material could act as a promising candidate for the treatment of colorectal cancer with high efficacy and minimal toxicity.

Low-temperature photothermal irradiation triggers alkyl radicals burst for potentiating cancer immunotherapy

Although low-temperature photothermal therapy (PTT) can sensitize tumors to immune checkpoint inhibition, its efficacy is still restricted in the deep and internal tumors without enough oxygen and lymphocytic infiltration. Non-oxygen-dependent alkyl radicals have been demonstrated to synergistically enhance PTT through up-regulating lipid peroxidation and reactive oxygen species (ROS). Herein, an innovative strategy based on alkyl radicals to augment immunogenetic cell death (ICD) caused by mild PTT was proposed to improve poor efficacy of immunotherapy, which composed of a photothermal material of Chinse ink, an azo-initiator of 2,2-azobis[2-(2-imidazoline-2-acyl)propane]dihydrochloride (AIPH) and a PD-L1 inhibitor of HY19991 (HY). Upon near-infrared-II laser irradiation, low-temperature (<45℃) stimulation induced a high expression of immune checkpoint receptor (PD-L1) in tumors and triggered a large amount alkyl radicals generated by AIPH. Significantly, the alkyl radicals augmented the ICD and increased the recruitment of tumor-infiltrating lymphocytes against tumors after transformation of the immunologically cold tumor microenvironment into hot by mild PTT. The released HY further enhanced the immunotherapy effect by blocking the binding of activated T lymphocytes and PD-L1. In vivo studies exhibited that the all-in-one hydrogel with synergistic mechanisms had an extraordinary ability to reverse the immunosuppressive microenvironment, stimulate innate and adaptive immune responses to eliminate tumors and prevent metastasis.

Selective C(sp3)−N Bond Cleavage of N,N‐Dialkyl Tertiary Amines with the Loss of a Large Alkyl Group via an SN1 Pathway

AbstractPolar disconnection of the C(sp3)−N bond of N,N‐dialkyl‐substituted tertiary amines via ammonium species conventionally favored the loss of the smaller alkyl group by an SN2 displacement, while selective C(sp3)−N bond cleavage by cutting off the larger alkyl group is still underdeveloped. Herein, we present a novel Pd0‐catalyzed [2+2+1] annulation, proceeding through an alkyne‐directed palladacycle formation and consecutive diamination with a tertiary hydroxylamine by cleaving its N−O bond and one C(sp3)−N bond, for the rapid assembly of tricyclic indoles in a single‐step transformation. Noteworthy, experimental results indicated that large tert‐butyl and benzyl groups were selectively cleaved via an SN1 pathway, in the presence of a smaller alkyl group (Me, Et, iPr). Under the guidance of this new finding, tricyclic indoles bearing a removable alkyl group could be exclusively obtained by using a (α‐methyl)benzyl/benzyl or tert‐butyl/2‐(methoxycarbonyl)ethyl mixed amino source.

Selective C(sp3)−N Bond Cleavage of N,N‐Dialkyl Tertiary Amines with the Loss of a Large Alkyl Group via an SN1 Pathway

AbstractPolar disconnection of the C(sp3)−N bond of N,N‐dialkyl‐substituted tertiary amines via ammonium species conventionally favored the loss of the smaller alkyl group by an SN2 displacement, while selective C(sp3)−N bond cleavage by cutting off the larger alkyl group is still underdeveloped. Herein, we present a novel Pd0‐catalyzed [2+2+1] annulation, proceeding through an alkyne‐directed palladacycle formation and consecutive diamination with a tertiary hydroxylamine by cleaving its N−O bond and one C(sp3)−N bond, for the rapid assembly of tricyclic indoles in a single‐step transformation. Noteworthy, experimental results indicated that large tert‐butyl and benzyl groups were selectively cleaved via an SN1 pathway, in the presence of a smaller alkyl group (Me, Et, iPr). Under the guidance of this new finding, tricyclic indoles bearing a removable alkyl group could be exclusively obtained by using a (α‐methyl)benzyl/benzyl or tert‐butyl/2‐(methoxycarbonyl)ethyl mixed amino source.

Graphdiyne nanotubes in ionic liquids: Characterization of interfacial interactions by molecular dynamics

The interfacial interaction between ionic liquids and γ-graphdiyne nanotubes (GDYNT) has been scarcely explored, however, due to the porosity of the latter, it may be of interest to the development of improved energy storage devices. Here, the interfacial interactions in mixtures of [Emim][TFSI] and [Hmim][TFSI] with GDYNT are uncovered and compared to the interactions in mixtures of those ionic liquids with carbon nanotubes (CNTs). The porosity of GDYNT, in addition to its less stiff sidewall, allows an increased proximity between ions and the carbon sidewall, when compared to CNTs. It was demonstrated that hydrogen atoms (from cations) and fluorine atoms (from anions) assume preferential positions near the center of GDYNT’s pores, and, while [Emim] cations permit an almost crystal like packing of the ionic liquid inside GDYNT, the large alkyl “tail” of [Hmim] cation impedes that layer ordering. It was also found that the porous nature of GDYNT acts partially as a very fine sieve, “gluing” smaller atoms to its surface, while removing the remainders, which was not observed in mixtures of ionic liquids with CNTs. A detailed characterization of the interfacial interactions between ionic liquids and GDYNTs, using molecular dynamics modeling, is here presented for the first time.

The effect of alkyl chain and electronegative atoms in anion on biological activity of anilinium carboxylate bioactive ionic liquids and computational approaches by DFT functional and molecular docking

The Brønsted acid-base neutralization was executed for synthesis of the anilinium carboxylate ionic liquids (ACILs), and obtained highly viscous liquids with yields about (90–94)%. These ILs were purified by distillation process and used vacuum oven, as well as characterized by FT-IR, UV spectroscopy and 1H-NMR. To evaluate the antimicrobial activity, the well diffusion method was used against eight human pathogenic bacteria, showing inhibition of zone at 13 mm–27 mm, and three fungi with result about 60%. Plus, the DFT functional from material studio 8.0 was used for evaluation of computational screening for estimating the chemical reactivity, HOMO, LUMO and HOMO-LUMO gap, recorded from -7.252 to -8.20 kcal/mol. The IL05 has showed about -6.5 kcal/mol docking score as standard inhibitor, as and higher than starting. Form AMDET properties, it has revealed that they have low toxicity, higher absorption through the biological system and non-carcinogenic. Finally, the electronegative groups, such as F, Cl and Br atoms in anion can show the higher antimicrobial activity and molecular docking score among all others while F atom containing IL05 shows the highest docking score and antimicrobial activity. However, it is concluded that rather than long large alkyl chain of anion, F atom (the highest electronegative atom) containing anion is better for biologically significance ILs.

Molecular Structural Influence of Glymes on Co-Intercalation Behavior of Solvated Li+ in Graphite Electrodes

Solvated Li+ ions are intercalated into graphite in a dilute glyme-based solution and this reaction has attracted much attention for use in advanced lithium-ion batteries due to their high rate capability. In this study, Li+ co-intercalation behaviors in asymmetric glymes (CH3O(CH2CH2O) n C4H9, n = 2 or 3) were investigated and compared to those in symmetric glymes (CH3O(CH2CH2O) n CH3, n = 1–4). Despite the large alkyl sidechains of asymmetric glymes, co-intercalation reactions of solvated Li+ proceeded as well as those in symmetric glymes. In charge and discharge measurements, the reversible capacities in asymmetric glyme-based solutions were smaller than those in symmetric glymes except for tetraglyme, which showed the lowest reversible capacity. There was no clear difference in the sandwich distances of glyme-Li-GICs calculated from X-ray diffraction patterns of both symmetric and asymmetric glymes. Therefore, solvated Li+ ions with asymmetric glymes occupied more space in the graphite interlayer compared to symmetric glymes, which resulted in smaller reversible capacities for asymmetric glymes. These results demonstrate the influence of solvent-related structures of GICs on reversible capacities for co-intercalation systems.

Beyond the rule of transition state: Identification of roaming routes in some cases of carbonyl compounds

AbstractThis account focuses on photodissociation of carbonyl compounds to verify a so‐called roaming route, alternative to those passing through a transition state (TS) invoked in the realm of the kinetics of elementary chemical processes. Such a roaming route bypasses the minimum energy path but produces the same molecular products. The photodissociation of the carbonyl compounds of study includes methyl formate (HCOOCH3), formic acid (HCOOH), and aliphatic aldehydes (RCOH, RH, CH3, and large alkyl group). Methyl formate and formic acid were promoted to the excited state, followed by internal conversion via a conical intersection. Then, the energetic precursor dissociated to fragments, which proceeded along either TS or roaming path. As the excitation energy increases, the roaming fraction in methyl formate is significantly interfered with by an open channel of triple fragmentation (H + CO + CH3O), whereas such a channel may not occur in formic acid even at an excitation wavelength of 193 nm. As a distinct roaming type, aliphatic aldehydes are found to possess the structure of the roaming saddle point comprising two moieties weakly bound at a distance. The energy difference between the TS barrier and the roaming saddle point is indicative of the extent for the roaming contribution. The roaming route becomes increasingly dominant when the aliphatic aldehyde is larger. Experimentally, ion imaging was employed to visualize the rotational‐level dependence of the roaming route, while time‐resolved Fourier‐transform infrared emission spectroscopy was applied to determine the vibrational‐state dependence. The roaming signature was verified theoretically by quasi‐classical trajectory calculations. As an alternative, a multi‐center impulsive model was developed to simulate the roaming scalar and vector properties without involving the global energy surface.

Phenylthioether thiophene-based oxime esters as novel photoinitiators for free radical photopolymerization under LED irradiation wavelength exposure

Four new photoinitiators (PIs) containing phenylthioether-substituted thiophene groups as chromophores and oxime ester groups as initiating groups were designed and synthesized. These compounds exhibit excellent absorption under exposure to light-emitting diode (LED) irradiation wavelength (i.e., 365–425 nm). Moreover, they have a higher radical generation efficiency than the commercial PI O-benzoyl-α-oxooxime (i.e., OXE 01). The mechanism by which these oxime esters generate radicals was investigated via steady-state photolysis, high performance liquid chromatography, and online 1H NMR. These PIs can efficiently initiate the polymerization of acrylate monomer. Acetyl oxime esters show higher conversions than OXE 01 under LED irradiation at 365–425 nm. The methyl substituent on the benzene ring, the volume effect of the large alkyl group, and the acetyl substitution on the oxime ester all contribute to high photoinitiation efficiency. Owing to their excellent absorption and efficient photoinitiation properties, these optimized PIs have great potential in photocuring applications.

Synergistic antimicrobial activity of N-methyl substituted pyrrolidinium-based ionic liquids and melittin against Gram-positive and Gram-negative bacteria.

In pharmaceutical industry, the prodrug approaches and drug-drug conjugates are being now vastly used to optimize the efficacy of the drugs for multipurpose. The combination or conjugation of antimicrobials agents with natural antimicrobials may lead to better synergistic antimicrobial activity. Currently, many publications show the potential of ionic liquids (ILs) as novel antimicrobials and even as active pharmaceutical ingredients. The current study showed the synthesis of novel pyrrolidinium-based ILs (Cx, x = 4, 6, 8, 10, 12) and their antibacterial activity alone and in combination with antimicrobial peptide, melittin (MEL), against clinically relevant microorganism, E. coli and S. aureus. The cytotoxicity of synthesized ILs was administered on HEK 293 cell line using MTT assay. The obtained results showed the dependency of antibacterial activity of ILs on alkyl chain length (C4 < C6 < C8 < C10 < C12). The remarkable improvement in the antibacterial efficiency of MEL was seen with ILs; however, antibacterial effect is more pronounced with IL having large alkyl chain length (C8, C10, and C12) at their minimal concentration with MEL to disrupt the cell membrane. In addition, the binding study and haemocompatibility results showed favourable biocompatibility and stability which could potentially improve its utility for the biomedical field. KEY POINTS: • The combination of melittin and pyrrolidinium-based ILs showed improved antibacterial activity against E. coli and S. aureus which may be used for developing new antibacterial agents. • Moreover, the cytotoxicity and haemocompatibility results showed excellent biocompatibility of the combinations on human cell line and human serum albumin, respectively, which could potentially improve its utility for the biomedical field.

Variation in Near-Infrared Spectra of Water Containing Polyhydric Alcohol

Near-infrared absorption spectra of aqueous solutions of eleven polyhydric alcohols (nine dihydric alcohols and two trihydric alcohols) at concentrations up to 20% were obtained at 20, 25, and 30 °C. Variations in the band due to O–H stretching vibration overtones of water and alcohol with changes in concentration and temperature were determined by a multivariate curve resolution-alternating least squares analysis, which identified the components of the band causing the spectral variation. The band consisted of three common components almost independent of the alcohol type. The first and the second components are attributed, respectively, to water molecules weakly hydrogen-bonded (or non hydrogen-bonded) and those strongly hydrogen-bonded with other water molecules, while the third component are due to water interacting with the alcohol and to the alcohol itself. The abundance of the first and third components decreased and increased, respectively, as the alcohol concentration increased. In contrast, the abundance of the second component increased initially and then decreased. The initial increase corresponds to the enhancement of hydrogen bonding by hydrophobic interactions. The subsequent decrease is due to an increase in water–alcohol interactions and a decrease in water concentration. The maximum increase in the abundance of the second component depended on the type of alcohol. The increase in abundance was greater for alcohols with larger alkyl groups. In contrast, the increase in abundance of the second component was smaller for alcohols with more hydric groups.