Aromatic Linkers Research Articles

Expanding the Variety of Pyridinium‐Based bis‐QACs with Antimicrobial Properties: Investigation into Linker Structure‐Activity Correlation.

For decades quaternary ammonium compounds (QACs) have served as main component of a top antiseptic and disinfectant compositions. Among them, bis‐QACs are the most prominent and effective class of biocides. Although mono‐QACs still dominate the antiseptic market, their activity against Gram‐negative bacteria is largely inferior to bis‐QACs. Moreover, the new wave of bacterial resistance during the COVID‐19 pandemic is threatening the efficiency of popular antiseptics. Therefore, the requirement for novel biocides is urgent. Reported here is a unified and simple two‐step synthesis to achieve novel biocide’s architectures with aromatic linkers. Thus, a series of 14 bis‐QACs have been prepared using an Ullman‐type reaction following by N‐alkylation. The most prominent compounds showed strong bioactivity against a panel of nineteen microbial pathogens, multi‐resistant bacterial ESKAPEE strains, fungi and biofilms, including strains, which acquired resistance during COVID‐19 in 2021. Moreover, significant improvements in antibiofilm action were observed, where bis‐QACs 5c and 6a outperformed gold standard pyridinium antiseptic octenidine. These findings will serve as a good basis for further studies of bis‐QACs architectures as highly effective biocides.

Bis-3-chloropiperidines: a novel motif for anthelmintic drug design.

Parasites account for huge economic losses by infecting agriculturally important plants and animals. Furthermore, morbidity and death caused by parasites affect a large part of the world population, especially in economically weak regions. Anthelmintic drugs to tackle this challenge remain scarce and their efficiency becomes increasingly endangered by the advent of drug resistance development. In the present study, we assessed the anthelmintic potential of bis-3-chloropiperidines, a family of compounds which have already demonstrated antiproliferative activity against various cell lines. We synthesized and tested the activity of 21 bis-3-chloropiperidine derivatives against two strains of the free-living nematode Caenorhabditis elegans (N2 and DC19) and the parasitic flatworm Schistosoma mansoni. Overall, bifunctional chloropiperidines featuring an aromatic linker performed best against the tested indicator organisms and could be considered for future optimization efforts. Ultimately, out of the 21 analyzed bis-3-chloropiperidines, four derivatives (2, 5, 9 and 11) reduced vitality parameters against S. mansoni and five the motility of C. elegans (2, 4, 5, 13, 21) while exhibiting no or low cytotoxicity.

Aromatic vs. aliphatic linkers: impact on dye loading and stability in oligoglycerol-derived dendronized polymersomes

We report the synthesis and self-assembly of oligoglycerol-based dendronized polythiourethanes, which consist of an aliphatic or aromatic linker. Using FRET, the effect of the linker was understood and the dye exchange mechanism was unravelled.

Architecting Multi-Level Structures and Regulating Hydrophilicity of Covalent Organic Framework Aerogels for Optimizing Mass Transport Capacity.

Architecting hierarchical structures in monolithic covalent organic frameworks (COFs) is vital for the applications of COFs in mass transport fields. The MXene-coated bilayer aerogels containing β-keto-enamine COF (MX-TpX-COF) with different chain lengths of aromatic linkers are constructed for the study. The directional freezing method endowed the COF part and MXene coating with aligned channels, and the small pores mainly exist in the former, while the larger ones in the latter. The occurrence of multi-level structures inside COF bulks, together with locally ordered vessels formed in the surfaces of MXene coating, are conducive to the mass transport of aerogels. Accordingly, the MX-TpX-COF aerogels showed attractive performance in oil/water separation and desalination, and even can be used for treating and desalinating oil-contaminated seawater simultaneously. The mass transport rate and efficiency, however, strongly depended on the hydrophilicity and specific surface areas of COF bulks, which can be easily tuned by tailoring the chain lengths of aromatic linkers. This study offers a specific perspective on the utilization of bulk COF materials in marine governance, and also proposes a structural regulation way of multi-functional integration for COF-based aerogels.

Deciphering the Impact of Aromatic Linkers in Self‐Assembled Monolayers on the Performance of Monolithic Perovskite/Si Tandem Photovoltaic

Aromatic linker‐constructed self‐assembled monolayers (Ar‐SAMs) can modulate the work function of indium tin oxide (ITO), thereby improving hole extraction/transport efficiency. However, the specific role of the aromatic linkers between the polycyclic head and the anchoring groups of SAMs in determining the performance of perovskite solar cells (PSCs) remains unclear. In this study, we developed a series of phenothiazine‐based Ar‐SAMs to investigate how different aromatic linkers could affect molecular stacking, the regulation of substrate work function, and charge carrier dynamics. When served as hole‐selective layers (HSLs) in PSCs and monolithic perovskite/silicon tandem solar cells (P/S‐TSCs), we found that the Ar‐SAM with naphthalene linker along the 2,6‐position axis (β‐Nap) could form dense and highly ordered HSLs, enhancing interfacial interactions and favoring optimal energy level alignment with the perovskite films. Using this strategy, the optimized wide‐bandgap PSCs achieved an impressive power conversion efficiency (PCE) of 21.86% with negligible hysteresis, utilizing a 1.68 eV perovskite. Additionally, the encapsulated devices demonstrated enhanced stability under damp‐heat conditions (ISOS‐D‐2, 50% RH, 65°C) with a T91 of 1000 hours. Notably, the fabricated P/S‐TSCs, based on solution‐processed micron‐scale textured silicon heterojunction (SHJ) solar cells, achieved an efficiency of 28.89% with outstanding reproducibility.

Deciphering the Impact of Aromatic Linkers in Self-Assembled Monolayers on the Performance of Monolithic Perovskite/Si Tandem Photovoltaic.

Aromatic linker-constructed self-assembled monolayers (Ar-SAMs) can modulate thework function of indium tin oxide (ITO), thereby improving hole extraction/transportefficiency. However, the specific role of the aromatic linkers between the polycyclichead and the anchoring groups of SAMs in determining the performance of perovskitesolar cells (PSCs) remains unclear. In this study, we developed a series ofphenothiazine-based Ar-SAMs to investigate how different aromatic linkers could affectmolecular stacking, the regulation of substrate work function, and charge carrierdynamics. When served as hole-selective layers (HSLs) in PSCs and monolithic perovskite/silicon tandem solar cells (P/S-TSCs), we found that the Ar-SAM withnaphthalene linker along the 2,6-position axis (β-Nap) could form dense and highlyordered HSLs, enhancing interfacial interactions and favoring optimal energy levelalignment with the perovskite films. Using this strategy, the optimized wide-bandgap PSCs achieved an impressive power conversion efficiency (PCE) of 21.86% withnegligible hysteresis, utilizing a 1.68 eV perovskite. Additionally, the encapsulateddevices demonstrated enhanced stability under damp-heat conditions (ISOS-D-2, 50%RH, 65°C) with a T91 of 1000 hours. Notably, the fabricated P/S-TSCs, based onsolution-processed micron-scale textured silicon heterojunction (SHJ) solar cells,achieved an efficiency of 28.89% with outstanding reproducibility.

Nanoconfined Metal Hydrides As Alternatives to Lithium Ion Battery Energy Storage

Energy densities of metal hydrides are competitive with lithium ion batteries (Fig. 1), highlighting their potential as contenders for emerging energy storage technologies. Metal hydrides have long been of interest for hydrogen storage for both transportation and stationary applications. However, most of these materials are too stable, i.e. their enthalpy of H2 desorption is too high to use the residual heat of a proton exchange membrane (PEM) fuel cell to drive the H2 release. Alternatively, metastable metal hydrides (MMH), for which H2 release is exothermic or only slightly endothermic, have received much less attention. Compounds such as LiAlH4 and AlH3 are so thermodynamically unstable that direct rehydrogenation following H2 release is thought to be impossible. This is unfortunate because these hydrides have high gravimetric and volumetric energy densities with potential for fast, low-temperature hydrogen release to power a fuel cell.The goal of this work was to synthesize nanoscale metal hydrides from earth-abundant elements and demonstrate that they can achieve energy densities higher than state-of-the-art lithium ion batteries, achieving full recharge using the residual heat from a PEM fuel cell. We employed a nanoconfinement strategy to improve the thermodynamics and kinetics of hydrogen release and uptake, which has been shown to be effective for many thermally stable metal hydrides.2 We will describe the synthesis and properties of nanoconfined alane (AlH3) using a bipyridine-functionalized covalent triazine framework (CTF) and the Metal-Organic Framework (MOF) UiO-67bpy (Zr6O4(OH)4(bpydc)6; bpydc2− =2,2′-bipyridine-5,5′dicarboxylate), which can coordinate AlH3 through the aromatic linker nitrogens.We find that the MOF and CTF both maintain the porous structure after infiltration. Brunauer-Emmett-Teller (BET) surface areas derived from nitrogen isotherms indicate significant decreases in the surface area and pore volume. Using a focused ion beam (FIB) to cut a channel in a MOF crystal surface, we obtained cross-sectional transmission electron microscopy (TEM)/energy-dispersive X-ray spectroscopy (EDS) images indicating that AlH3 is uniformly infiltrated throughout the MOF. Electron energy loss (EELS) spectra reveal that signals from MOF linker carbon atoms and aluminum atoms alternate along the FIBed channel, providing convincing evidence that AlH3 is located within the pores. Solid state 27Al-NMR, DFT calculations, and single crystal X-ray diffraction provide additional evidence that AlH3 is located in the vicinity of the bipyridine groups.We also demonstrate that AlH3 is thermodynamically stabilized by nanoconfinement within the CTF. AlH3@CTF-bipyridine rapidly desorbs hydrogen between 95 – 150 °C. Even more surprising, AlH3@CTF-bipyridine dehydrogenation is reversible at only 60 °C and 700 bar hydrogen, a pressure 36 times lower than the experimentally measured H2 plateau pressure of bulk aluminum. Together, these results suggest that metastable hydrides could be practical materials for H2 storage, and in selected cases with theoretical energy densities exceeding those of Li-ion batteries. L. Snider, M. Witman, M. E. Bowden, K. Brooks, B. L. Tran, T. Autrey Nat. Chem., DOI: 10.1038/s41557-022-01056-2Girishkumar, B. McCloskey, A. C. Luntz, S. Swanson, W. Wilcke J. Phys. Chem. Lett. 2010, 1, 2193–2203. Figure 1. Comparison of volumetric energy density vs. gravimetric energy density for various energy carriers and batteries. Adapted from Ref. 1. Figure 1

Facile synthesis of Bidentate Boron Lewis Acids by Pentafluorobenzene Elimination

AbstractThe obtained results reveal simple synthetic approach for bidentate boron Lewis acids with the ‐OB(C6F5)2 acid group and aliphatic or aromatic linkers. Computational results showed comparable FIA for the ‐OB(C6F5)2 site in boron bidentate Lewis acids relative to initial B(C6F5)3. The relative Lewis acid strength of R[OB(C6F5)2]2 (R=C2H4, p‐C6H4, m‐C6H4) was characterized by Gutman‐Beckett tests. The elimination of pentafluorobenzene by the reaction of R‐OH with B(C6F5)3 can be used for the synthesis of R‐OB(C6F5)2 derivatives and polydentate strong Lewis acids.

Metal-Hydroxide Organic Frameworks for Aqueous Nickel-Zinc Batteries.

Hydroxides exhibit a high theoretical capacity for energy storage by ion release and are often intercalated with anions to enhance the ion migration kinetics. In this study, a series of metal-hydroxide organic frameworks (MHOFs) are synthesized by intercalating aromatic organic linkers into hydroxides using I-M/Ni(OH)2 (where M = Co2+, Cu2+, Mg2+, Fe2+). The coordination environment and layer spacing (1.09 nm) of I-M/Ni(OH)2 are explored by X-ray absorption fine structure and cryo-electron microscopy. The intercalation nanostructure improves the conductivity of the hydroxides and facilitates Zn2+ migration by increasing the interlayer spacing, while enhancing the rate capability and cycling stability. Consequently, the I-Co/Ni(OH)2 material exhibites a satisfactory specific capacity of 0.35 mAh cm-2 at 3 mA cm-2 and a high peak power density of 6.78 mW cm-2. This study offers a novel perspective on the design of intercalated hydroxide and provides new insights into high-performance nickel-zinc batteres.

Understanding CO adsorption in MOFs combining atomic simulations and machine learning

This study introduces a computational method integrating molecular simulations and machine learning (ML) to assess the CO adsorption capacities of synthesized and hypothetical metal–organic frameworks (MOFs) at various pressures. After extracting structural, chemical, and energy-based features of the synthesized and hypothetical MOFs (hMOFs), we conducted molecular simulations to compute CO adsorption in synthesized MOFs and used these simulation results to train ML models for predicting CO adsorption in hMOFs. Results showed that CO uptakes of synthesized MOFs and hMOFs are between 0.02–2.28 mol/kg and 0.45–3.06 mol/kg, respectively, at 1 bar, 298 K. At low pressures (0.1 and 1 bar), Henry’s constant of CO is the most dominant feature, whereas structural properties such as surface area and porosity are more influential for determining the CO uptakes of MOFs at high pressure (10 bar). Structural and chemical analyses revealed that MOFs with narrow pores (4.4–7.3 Å), aromatic ring-containing linkers and carboxylic acid groups, along with metal nodes such as Co, Zn, Ni achieve high CO uptakes at 1 bar. Our approach evaluated the CO uptakes of ~ 100,000 MOFs, the most extensive and diverse set studied for CO capture thus far, as a robust alternative to computationally demanding molecular simulations and iterative experiments.

Fast tailoring the ZIF-8 surface microenvironment at ambient temperature to boost glucose oxidase-like activity of AuNPs for biosensing

Rational design and tailoring of the surface microenvironment surrounding the catalytic sites, such as noble metal nanoparticles, is an effective way to enhance the catalytic activity of mimicking enzymes. However, it remains on-going challenges to regulate the microenvironment of the catalytic sites due to the lack of tunable variability in structural precision of conventional solid catalysts. Herein, three types of zeolitic imidazolate framework-8 (ZIF-8) with different major crystal facet orientations, i.e., cubic with (100) facets (denoted ZIF-8c), truncated dodecahedral with (100), (110) facets (denoted ZIF-8tr), and dodecahedral with (110) facets (denoted ZIF-8r), were developed facilely using an electrochemical method by switching the potential at ambient temperature. Because the Zn2+ nodes were predominantly exposed on the (100) facets of ZIF-8, while the ligands were mainly exposed on the (110) facets. Hence, gold nanoparticles (AuNPs) showed differential glucose oxidase (GOx)-like activities when anchored in situ on different crystal facets of ZIF-8 and obeyed the following order ZIF-8c/Au>ZIF-8tr/Au>ZIF-8r/Au. Notably, both the metal nodes and aromatic linkers of ZIF-8 interacted with AuNPs through coordination and π-π interactions. The Zn2+ nodes facilitated the formation of the electron-deficient Au species. The electron transfer from AuNPs to Zn2+ sites effectively boosted the catalytic activity. It was known that directly tailoring the microenvironment at the supporting sites of noble metal catalysts to boost catalysis through a facile electrochemical method was not reported. Based on the favorable GOx-like activity and long-term stability of ZIF-8tr/Au, a highly sensitive electrochemical biosensing platform for assaying squamous cell carcinoma antigen (SCCA) was developed. It enabled fg-level detection of cancer marker.

Development of Phloroglucinol-Linked Tris-Quaternary Ammonium Salt Antimicrobial Peptide Mimics with Low Cytotoxicity and Broad-Spectrum Antibacterial Activity.

Encouraged by the significantly different toxicities and antibacterial activities of diverse linkers, such as alkyl and aromatic nuclei linkers, and the unique structure of phloroglucinol, we synthesized a series of tris-quaternary ammonium salt (tris-QAS) antibacterial peptide mimics based on the marketed drug phloroglucinol. Among them, 2f displayed excellent activity against Staphylococcus aureus (MIC = 0.5 μg/mL) and high selectivity (SI > 2560). Surprisingly, the cytotoxicity of 2f (CC50 = 152.7 μg/mL) was dramatically better than those of alkyl QAS I and hydroquinone QAS II. Additionally, 2f possessed rapid bactericidal capability, was not prone to inducing bacterial resistance, and also exhibited excellent activity against S. aureus biofilms and persistent bacteria. Mechanistic research and transcriptome analysis revealed that 2f can interfere with the normal metabolism of bacterial cells, and it can specifically bind with phosphatidylglycerol to destroy the cell membrane. Importantly, 2f exhibited potent in vivo antibacterial activity in a mouse subcutaneous methicillin-resistant S. aureus (MRSA) infection model.

Quasi-One-Dimensional Zigzag Covalent Organic Frameworks for Photocatalytic Hydrogen Evolution from Water.

Covalent organic frameworks (COFs) have potential applications in a wide range of fields. However, it remains a critical challenge to constrain their covalent expansions in the one-dimensional (1D) direction. Here, we developed a general approach to fabricate 15 different highly crystalline COFs with zigzag-packed 1D porous organic chains through the condensation of V-shaped ditopic linkers and X-shaped tetratopic knots. Appropriate geometrical combinations of a wide scope of linkers and knots with distinct aromatic cores, linkages, and functionalities offer a series of quasi-1D COFs with dominant pore sizes of 7-13 Å and surface areas of 116-784 m2 g-1. Among them, nitrogen (N)-doped 1D COFs with site-specific doping of heteroatoms favor a tunable control of band structures and conjugations and thus allow a remarkable hydrogen evolution rate up to 80 mmol g-1 h-1 in photocatalytic water splitting. This general strategy toward programming function in porous crystalline materials has the potential to tune the topologically well-defined electronic properties through precisely periodic doping.

Heteropolyaromatic Covalent Organic Frameworks via One-Pot Multicomponent Reactions.

Multicomponent reactions (MCRs) offer a platform to create different chemical structures and linkages for highly stable covalent organic frameworks (COFs). As an illustrative example, the multicomponent Povarov reaction generates 2,4-phenylquinoline from aldehydes and amines in the presence of electron-rich alkenes. In this study, we introduce a new domino reaction to generate unprecedented 2,3-phenylquinoline COFs in the presence of epoxystyrene. This work thus presents, for the first time, structural isomeric COFs produced by multicomponent domino and Povarov reactions. Furthermore, 2,3-phenylquinolines can undergo a Scholl reaction to form extended aromatic linkages. With this approach, we synthesize two thermally and chemically stable MCR-COFs and two heteropolyaromatic COFs using both domino and in situ domino and Scholl reactions. The structure and properties of these COFs are compared with the corresponding 2,4-phenylquinoline-linked COF and imine-COF, and their activity toward benzene and cyclohexane sorption and separation is investigated. The position of the pendant phenyl groups within the COF pore plays a crucial role in facilitating the industrially important sorption and separation of benzene over cyclohexane. This study opens a new avenue to construct heteropolyaromatic COFs via MCR reactions.

Covalently bridging graphene edges for improving mechanical and electrical properties of fibers

Assembling graphene sheets into macroscopic fibers with graphitic layers uniaxially aligned along the fiber axis is of both fundamental and technological importance. However, the optimal performance of graphene-based fibers has been far lower than what is expected based on the properties of individual graphene. Here we show that both mechanical properties and electrical conductivity of graphene-based fibers can be significantly improved if bridges are created between graphene edges through covalent conjugating aromatic amide bonds. The improved electrical conductivity is likely due to extended electron conjugation over the aromatic amide bridged graphene sheets. The larger sheets also result in improved π-π stacking, which, along with the robust aromatic amide linkage, provides high mechanical strength. In our experiments, graphene edges were bridged using the established wet-spinning technique in the presence of an aromatic amine linker, which selectively reacts to carboxyl groups at the graphene edge sites. This technique is already industrial and can be easily upscaled. Our methodology thus paves the way to the fabrication of high-performance macroscopic graphene fibers under optimal techno-economic and ecological conditions.

Constructing Photocatalytic Covalent Organic Frameworks with Aliphatic Linkers.

Photocatalytic covalent organic frameworks (COFs) are typically constructed with rigid aromatic linkers for crystallinity and extended π-conjugation. However, the essential hydrophobicity of the aromatic backbone can limit their performances in water-based photocatalytic reactions. Here, we for the first time report the synthesis of hydrophilic COFs with aliphatic linkers [tartaric acid dihydrazide (TAH) and butanedioic acid dihydrazide] that can function as efficient photocatalysts for H2O2 and H2 evolution. In these hydrophilic aliphatic linkers, the specific multiple hydrogen bonding networks not only enhance crystallization but also ensure an ideal compatibility of crystallinity, hydrophilicity, and light harvesting. The resulting aliphatic linker COFs adopt an unusual ABC stacking, giving rise to approximately 0.6 nm nanopores with an improved interaction with water guests. Remarkably, both aliphatic linker-based COFs show strong visible light absorption, along with a narrow optical band gap of ∼1.9 eV. The H2O2 evolution rate for TAH-COF reaches up to 6003 μmol h-1 g-1, in the absence of sacrificial agents, surpassing the performance of all previously reported COF-based photocatalysts. Theoretical calculations reveal that the TAH linker can enhance the indirect two-electron oxygen reduction reaction for H2O2 production by improving the O2 adsorption and stabilizing the *OOH intermediate. This study opens a new avenue for constructing semiconducting COFs using nonaromatic linkers.

Linker Mediated Electronic-State Manipulation of Conjugated Organic Polymers Enabling Highly Efficient Oxygen Reduction.

Conjugated polymers with tailorable composition and microarchitecture are propitious for modulating catalytic properties and deciphering inherent structure-performance relationships. Herein, we report a facile linker engineering strategy to manipulate the electronic states of metallophthalocyanine conjugated polymers and uncover the vital role of organic linkers in facilitating electrocatalytic oxygen reduction reaction (ORR). Specifically, a set of cobalt phthalocyanine conjugated polymers (CoPc-CPs) wrapped onto carbon nanotubes (denoted CNTs@CoPc-CPs) are judiciously crafted via in situ assembling square-planar cobalt tetraaminophthalocyanine (CoPc(NH2)4) with different linear aromatic dialdehyde-based organic linkers in the presence of CNTs. Intriguingly, upon varying the electronic characteristic of organic linkers from terephthalaldehyde (TA) to 2,5-thiophenedicarboxaldehyde (TDA) and then to thieno/thiophene-2,5-dicarboxaldehyde (bTDA), their corresponding CNTs@CoPc-CPs exhibit gradually improved electrocatalytic ORR performance. More importantly, theoretical calculations reveal that the charge transfer from CoPc units to electron-withdrawing linkers (i.e., TDA and bTDA) drives the delocalization of Co d-orbital electrons, thereby downshifting the Co d-band energy level. Accordingly, the active Co centers with more positive valence state exhibit optimized binding energy toward ORR-relevant intermediates and thus a balanced adsorption/desorption pathway that endows significant enhancement in electrocatalytic ORR. This work demonstrates a molecular-level engineering route for rationally designing efficient polymer catalysts and gaining insightful understanding of electrocatalytic mechanisms.

Quantifying the contribution of lignin to humic acid structures during composting

The transformation behavior of different types of lignin structure was investigated during composing with particular interest of revealing the contribution rate of lignin functional groups as well as their interaction to humic acids (HA). Rice straws, tree branches, and pine needles were selected as composting materials, because they predominantly contain G-S-H, G-S, and G-type lignin. Results showed that microorganisms were the driving force behind the conversion of lignin into HA. During composting, appeared different levels of cleavage, tearing, and fragmentation on the superficial lignin structures. In depth analysis of lignin transformation, lignin primarily consisted of aromatic groups, CO bonds, alkyl groups, hydroxyl groups and linkage between monomeric units (β-O-4, β-5 and β-β) in the early stage of composting. As lignin degraded, the CO bonds were gradually exposed. But due to their unstable nature, the CO bonds were prone to undergo changes with the cleavage of the aromatic rings at positions 2, 5, and 6 during composting. CO bonds could be converted into aromatic rings, alkyl groups, hydroxyl groups, and CO groups in HA. Through multiple linear regression analysis, it could be concluded that the CO bonds in G-type and S-type monomeric units contributed significantly to the aromatic rings, accounting for 30.4 % and 48.4 %, respectively. The main mechanism might be related to the cleavage of CO bonds and subsequent atomic rearrangement after the release of carbon atoms. This in-depth analysis filled the gap in the mechanism of HA formation during composting.

Aromatic linker variations in novel dopamine D2 and D3 receptor ligands.

Dopamine D2-like receptors, especially D2 and D3 receptor subtypes, are important targets of antipsychotic agents. Many of these antipsychotics share an aliphatic linker element between a protonable amine group and an acyl-like moiety. Here, we have modified this aliphatic linker into phenylmethyl and phenylethyl linkers substituted in different positions. The design, synthesis, and in vitro evaluation of 18 dopamine D2 and D3 receptor ligands were performed in this study. Using a radioligand displacement assay, all ligands were found to have modest nanomolar affinity to D2R and D3R. N-(4-{2-[4-(2-Methoxyphenyl)piperazin-1-yl]ethyl}phenyl)acetamide (6c) demonstrates the highest D3R and D2R affinity values (pKi values of 7.83 [D2R] and 8.04 [D3R]), featuring a slight preference to D3R. This derivative can be taken as a reference structure for the development of a new class of D2R and D3R ligands.

Biphenyls embedded Schiff base-bis esters: self-assembling behaviour, impact of additional aromatic ring and ester linkage and their DFT investigations

ABSTRACT In the present investigation, two series of biphenyl embedded Schiff base-bis esters alkyl-(E)-4-(((4’-(decyloxy)-[1,1’-biphenyl]-4-yl)methylene)amino)-benzoate, BPK-(2–18) and alkyl-(E)-4-(((4’-((4-(decyloxy)benzoyl)oxy)-[1,1’-biphenyl]-4-yl)-methylene)amino)benzoate, BPEK-(8–18) containing either terminal alkoxy biphenyl core or central biphenyl core have been synthesised and studied for their self-assembling behaviour. The compounds of both series demonstrated enantiotropic liquid crystal properties, displaying typical calamitic mesophases (Smectic A (SmA), Smectic C (SmC)) across a broad temperature range and with high thermal stability. The bimorphic behaviour of new molecules has been investigated by VT-XRD analysis. The density function theory has been done to illustrate the experimental results of the mesomorphic properties of the studied compounds. Several parameters have been calculated such as molecular geometry, dipole moment, polarisability, aspect ratio, etc. The results showed that more planar compounds will attain more packed structures leading to the formation of more ordered smectic phases.