Core Side Chains Research Articles

Synergistic effect of benzoselenadiazole core and alkoxy side chain substitution on the photovoltaic performance of non-fullerene acceptors

We developed a novel Y-series small molecule acceptor by adopting benzoselenadiazole central core and alkoxy side chains on the β-position of thiophene moieties, inducing a boost in performance due to upshifted energy levels and optimized morphology.

Revealing self-aggregation mechanism of asphaltenes during oxidative aging using quantum mechanical calculations

The density functional theory (DFT-D3) was used to reveal the molecular mechanisms responsible for self-aggregation of asphaltene. The results showed that electrostatic potential on the molecular vdW surface, atomic charge distribution and transfer, highest occupied, also lowest unoccupied orbitals all appeared at the aromatic rings and heteroatoms that in the aromatic core or aliphatic side chains of asphaltene molecules. The polar functional groups introduced by oxidation changed the electrostatic potential and charge distribution on these regions, which resulted in that electron over carbonyl groups (CO) around the aromatic core decreased the spatial extent of the π-electron cloud and the electron density, thus reduced some favorable contribution of π-π stacking effect in this region. The loss of interactions was partially compensated for by new forms of OH··N hydrogen bond and θ-θ interaction between the side chains in another part of the molecules. Compared to unoxidized dimer, the contribution of electrostatic interaction of oxidized asphaltenes enhanced from 2.42 % to 8.08 % and contribution of dispersion attraction slightly reduced from 63.41 % to 53.98 %. Bond critical points (BCPs) were distributed at aromatic rings and heteroatoms and the number of that were increase. The contributions of atom pair (δGpair (%)) around the strong OH··N bond (0.97 %) in oxidized dimer was significantly raised than that of unoxidized dimer (0.61 %). These changes were consistent with the electronic characteristics of asphaltene molecules after oxidation.

Recent Progress of Y6‐Derived Asymmetric Fused Ring Electron Acceptors

AbstractSymmetric conjugated molecules can be broken through suitable synthetic strategies to construct novel asymmetric molecules, which can largely broaden the material library. In the field of organic solar cells, fused‐ring electron acceptors (FREAs) with the A‐DA'D‐A type backbone structure have attracted much attention and enabled power conversion efficiencies (PCE) exceeding 18%. Among them, Y6 is one of the most classic FREAs that can derive many symmetric and asymmetric molecules and exhibit unique optoelectronic properties. Thus, in this review, the focus is on the recent progress of Y6‐derived asymmetric FREAs containing a dipyrrolobenzothiadiazole segment, which can be classified as the following three categories: asymmetric end group, asymmetric central core and asymmetric side chain. The relationship of the molecular structure, optoelectronic properties, and device performance is discussed in detail. Finally, the future design directions and challenges faced by this kind of photovoltaic materials are given.

Multiple glassy dynamics of a homologous series of triphenylene-based columnar liquid crystals – A study by broadband dielectric spectroscopy and advanced calorimetry

Hexakis(n-alkyloxy)triphenylene) (HATn) consisting of an aromatic triphenylene core and alkyl side chains are model discotic liquid crystal (DLC) systems forming a columnar mesophase. In the mesophase, the molecules of HATn self-assemble in columns, which has one-dimensional high charge carrier mobility along the columns. Here, a homologous series of HATn with different length of the alkyl chain (n = 5,6,8,10,12) is investigated using differential scanning calorimetry (DSC), broadband dielectric spectroscopy (BDS) and advanced calorimetric techniques including fast scanning calorimetry (FSC) and specific heat spectroscopy (SHS). The investigation of the phase behavior was done utilizing DSC experiments and the influence of the alkyl chain length on the phase behavior was revealed. By the dielectric investigations probing the molecular mobility, a γ-relaxation due to localized fluctuations as well as two glassy dynamics, the αcore- and αalkyl-relaxation, were observed in the temperature range of the plastic crystalline phase. Moreover, the observed glassy dynamics were further studied employing advanced calorimetry. All observed relaxation processes are attributed to the possible specific molecular fluctuations and discussed in detail. From the results a transition at around n = 8 from a rigid constrained (n = 5,6) to a softer system (n = 10,12) was revealed with increasing alkyl chain length. A counterbalance of two competing effects of a polyethylene-like behavior of the alkyl chains in the intercolumnar domains and self-organized confinement is discussed in the context of a hindered glass transition.

High-Performance Humidity Sensing in π-Conjugated Molecular Assemblies through the Engineering of Electron/Proton Transport and Device Interfaces.

The development of systems capable of responding to environmental changes, such as humidity, requires the design and assembly of highly sensitive and efficiently transducing elements. Such a challenge can be mastered only by disentangling the role played by each component of the responsive system, thus ultimately achieving high performance by optimizing the synergistic contribution of all functional elements. Here, we designed and synthesized a novel [1]benzothieno[3,2-b][1]benzothiophene derivative equipped with hydrophilic oligoethylene glycol lateral chains (OEG-BTBT) that can electrically transduce subtle changes in ambient humidity with high current ratios (>104) at low voltages (2 V), reaching state-of-the-art performance. Multiscale structural, spectroscopical, and electrical characterizations were employed to elucidate the role of each device constituent, viz., the active material's BTBT core and OEG side chains, and the device interfaces. While the BTBT molecular core promotes the self-assembly of (semi)conducting crystalline films, its OEG side chains are prone to adsorb ambient moisture. These chains act as hotspots for hydrogen bonding with atmospheric water molecules that locally dissociate when a bias voltage is applied, resulting in a mixed electronic/protonic long-range conduction throughout the film. Due to the OEG-BTBT molecules' orientation with respect to the surface and structural defects within the film, water molecules can access the humidity-sensitive sites of the SiO2 substrate surface, whose hydrophilicity can be tuned for an improved device response. The synergistic chemical engineering of materials and interfaces is thus key for designing highly sensitive humidity-responsive electrical devices whose mechanism relies on the interplay of electron and proton transport.

Lignin-based thermoresponsive macromolecules via vitamin-induced metal-free ATRP

An environmentally-friendly process for the modification of lignin with thermoresponsive polymers was employed, providing well-defined structures with narrow molecular weight distribution (Mw/Mn = 1.44). We report a biocompatible vitamin-inspired photoinitiation system composed of two components i.e. riboflavin (vitamin B2) as a photosensitizer and ascorbic acid (vitamin C) as a mild reducing agent. Under blue light LEDs irradiation at 460 nm (5.0 mW cm−2) the presented two-component photoinitiation setup enables grafting of poly(ethylene glycol) methyl ether methacrylate (OEGMA500) from brominated lignin via metal-free ATRP approach. A series of cyclic voltammetry (CV) measurements were conducted to electrochemically characterize ATRP initiators, both brominated lignin and lignin-based polymers, confirming preserved chain-end functionality of the prepared macromolecules. Received polymers with lignin core and POEGMA side chains exhibited thermoresponsive properties, which were investigated by determination of number average sizes of macromolecules by dynamic light scattering (DLS) and transmittance by ultraviolet/visible (UV-Vis) absorption spectroscopy of KL-g-(POEGMA-Br)10 aqueous solution. The in vitro curcumin release studies showed that the active substance is released from drug-loaded micelles in a thermo-sensitive manner. Prepared lignin-based macromolecules will show wide application as crucial components of thermoresponsive coatings, potentially creating bioactive surfaces characterized by antifouling properties, controlling cell adhesion or used as biosensors, due to PEG-containing side chains in branched polymers.

Influence of core extension and side chain nature in targeting G-quadruplex structures with perylene monoimide derivatives

A structure–activity relationship (SAR) study in terms of G-quadruplex binding ability and antiproliferative activity of six fluorescent perylenemonoimide (PMIs) derivatives is reported. A positive charge seems to be the key to target G4. This study also reveals the importance of the element substitution in the potential biological activity of PMIs, being the polyethylene glycol (PEG) chains in the peri position responsible for their antiproliferative activity. Among them, the cationic PMI6 with two PEG chains is the most promising compound since its fluorescence is enhanced in the presence of G-quadruplex structures. Moreover, PMI6 binds to the human telomeric G-quadruplex hTelo with high affinity and displays a high antiproliferative potential towards HeLa (cervical adenocarcinoma), A549 (lung adenocarcinoma) and A2780 (ovarian adenocarcinoma) cells. Its fate can be followed inside cells thanks to its fluorescent properties: the compound is found to accumulate in the mitochondria.

Total Synthesis, Structure Revision, and Neuroprotective Effect of Hericenones C-H and Their Derivatives.

The first total syntheses of hericenones C-H and "putative 3-hydroxyhericenone F" were achieved. Highlights of the synthesis include the straightforward construction of the resorcinol core and geranyl side chain, assembly of the natural product skeleton by sequential O-geranylation and a clay/zeolite-mediated O → C rearrangement reaction, and a biomimetic cyclization to form a variety of bicyclic natural hericenones and their congeners. The structure of the "putative 3-hydroxyhericenone F" was revised as the 5-exo cyclization product (named: hericenone Z) of epoxyhericenone C through in-depth analyses of the cyclization modes in addition to NMR spectroscopic studies. To gain insights into the biological functions of geranyl-resorcinols in Hericium erinaceus, potential neuroprotective effects against endoplasmic reticulum (ER) stress-dependent cell death were evaluated systematically to clarify a fundamental structure-activity relationship. Among the compounds assayed, the linoleate-containing hericenone analogue, i.e., the regioisomer of hericene D, was found to possess the most potent neuroprotective effect against tunicamycin and thapsigargin-induced ER stress-dependent cell death.

Effects of alkoxylation position on fused-ring electron acceptors

Four fused-ring electron acceptors composed of the same core and end groups without or with hexyloxyl groups on the core and/or phenyl side chains are compared to systematically study the effects of alkoxylation position on the molecular packing, optical, electronic, and photovoltaic properties of the nonfullerene acceptors.

Fluorenone imidazolium salts as novel de Vries materials.

In ionic liquid crystals (ILCs) tilted mesophases such as SmC required for electro-optic devices are quite rare. We report a design concept that induced the SmC phase and enabled de Vries-like behaviour in ILCs. For this purpose, we synthesized and characterized a library of ILC derivatives ImR(On,Ym)X which consist of a rigid central fluorenone core containing an alkoxy or thioether side chain and connected via a flexible spacer to an imidazolium head group. The mesomorphic properties were studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD). Temperature-dependent measurements of smectic layer spacing d by small-angle X-ray scattering (SAXS) and of optical tilt angles by POM demonstrate that ILCs ImR(On,Ym)X undergo SmA–SmC phase transitions with maximum layer contraction values between 0.4% and 2.1%. The lowest reduction factor R of 0.2 at the reduced temperature T − TAC = −10 K was calculated for Im(O12,S14)Br. Electron density calculations indicated a bilayer structure. Furthermore, temperature dependent emission studies show that self-assembling has a strong influence on the emission intensity of these ILCs.

Interactions between a subset of substrate side chains and AAA+ motor pore loops determine grip during protein unfolding.

Most AAA+ remodeling motors denature proteins by pulling on the peptide termini of folded substrates, but it is not well-understood how motors produce grip when resisting a folded domain. Here, at single amino-acid resolution, we identify the determinants of grip by measuring how substrate tail sequences alter the unfolding activity of the unfoldase-protease ClpXP. The seven amino acids abutting a stable substrate domain are key, with residues 2-6 forming a core that contributes most significantly to grip. ClpX grips large hydrophobic and aromatic side chains strongly and small, polar, or charged side chains weakly. Multiple side chains interact with pore loops synergistically to strengthen grip. In combination with recent structures, our results support a mechanism in which unfolding grip is primarily mediated by non-specific van der Waal's interactions between core side chains of the substrate tail and a subset of YVG loops at the top of the ClpX axial pore.

Antagonists for Constitutively Active Mutant Estrogen Receptors: Insights into the Roles of Antiestrogen-Core and Side-Chain.

A major risk for patients having estrogen receptor α (ERα)-positive breast cancer is the recurrence of drug-resistant metastases after initial successful treatment with endocrine therapies. Recent studies have implicated a number of activating mutations in the ligand-binding domain of ERα that stabilize the agonist conformation as a prominent mechanism for this acquired resistance. There are several critical gaps in our knowledge regarding the specific pharmacophore requirements of an antagonist that could effectively inhibit all or most of the different mutant ERs. To address this, we screened various chemotypes for blocking mutant ER-mediated transcriptional signaling and identified RU58668 as a model compound that contains structural elements that support potent ligand-induced inhibition of mutant ERs. We designed and synthesized a focused library of novel antagonists and probed how small and large perturbations in different ligand structural regions influenced inhibitory activity on individual mutant ERs in breast cancer cells. Effective inhibition derives from both nonpolar and moderately polar motifs in a multifunctional side chain of the antagonists, with the nature of the ligand core making important contributions by increasing the potency of ligands possessing similar types of side chains. Some of our new antagonists potently blocked the transcriptional activity of the three most common mutant ERs (L536R, Y537S, D538G) and inhibited mutant ER-mediated cell proliferation. Supported by our molecular modeling, these studies provide new insights into the role of specific components, involving both the ligand core and multifunctional side chain, in suppressing wild-type and mutant ER-mediated transcription and breast cancer cell proliferation.

Prediction of the phase equilibria for island-type asphaltenes via HMC-WL simulations.

Recent force microscopy experiments have shed light on new possible molecular structures for asphaltenes, which are key compounds for the oil industry. These studies have revealed the significance of asphaltenes with an island molecular architecture, i.e., composed of a large polycyclic aromatic hydrocarbon (PAH) core and alkyl side chains. In this work, we carry out molecular simulations based on a Wang-Landau sampling of the isothermal-isobaric ensemble to determine the thermodynamic properties of island-type asphaltenes at the vapor-liquid coexistence. We first parameterize a coarse-grained force field for these systems, focusing on compounds with a PAH core containing fluorene, fluoranthene, and dibenzothiophene motifs. Then, using this coarse-grained force field, we predict the entire phase envelope, including the boiling points and the critical parameters for a series of island-type asphaltenes.

Synthesis and mesophase characterization of methacrylate based three phenyl ring core side chain liquid crystalline copolymers

A new series of side chain liquid crystalline copolymers consisting of a mesogenic monomer and a non-mesogenic n-butyl methacrylate are prepared by free radical solution polymerization. The mesogenic monomer is synthesized by a multistep route and is built with side arm core consisting of three phenyl rings linked by an ester and a terminal alkoxy chain at one end and hexamethylene spacer between methacyrlate unit and the phenyl ring core. The copolymers are synthesized with different feed ratios of liquid crystalline monomer and n-butyl methacrylate to realize composition dependent copolymers. The mesogenic monomers are characterized by FT-IR, 1H and 13C NMR while for a representative mesogen solution two-dimensional (2D) NMR experiments are also carried out. The hot-stage optical polarized microscopy, differential scanning calorimetry and variable temperature powder X-ray diffraction investigations revealed the existence of enantiotropic nematic (N) and smectic C (SC) mesophases for the copolymers. The weight average and number average molecular weight of the copolymers are found to be in the range 1.6×104 to 3.7×104g/mol from gel permeation chromatography. Thermal degradation profile of mesogenic copolymers investigated by thermogravimetric analysis revealed that the copolymers are stable till 335°C in nitrogen atmosphere. The copolymer compositions were determined using 1H NMR analysis.

Controlling the Diameters of Nanotubes Self-Assembled from Designed Peptide Bolaphiles.

Controlling the diameters of nanotubes represents a major challenge in nanostructures self-assembled from templating molecules. Here, two series of bolaform hexapeptides are designed, with Set I consisting of Ac-KI4 K-NH2 , Ac-KI3 NleK-NH2 , Ac-KI3 LK-NH2 and Ac-KI3 TleK-NH2 , and Set II consisting of Ac-KI3 VK-NH2 , Ac-KI2 V2 K-NH2 , Ac-KIV3 K-NH2 and Ac-KV4 K-NH2 . In Set I, substitution for Ile in the C-terminal alters its side-chain branching, but the hydrophobicity is retained. In Set II, the substitution of Val for Ile leads to thedecrease of hydrophobicity, but the side-chain β-branching is retained. The peptide bolaphiles tend to form long nanotubes, with the tube shell being composed of a peptide monolayer. Variation in core side-chain branching and hydrophobicity causes a steady shift of peptide nanotube diameters from more than one hundred to several nanometers, thereby achieving a reliable control over the underlying molecular self-assembling processes. Given the structural and functional roles of peptide tubes with varying dimensions in nature and in technological applications, this study exemplifies the predictive templating of nanostructures from short peptide self-assembly.

Synthesis of (−)-6,7-Dideoxysqualestatin H5 by Carbonyl Ylide Cycloaddition–Rearrangement and Cross-electrophile Coupling

An asymmetric synthesis of (-)-6,7-dideoxysqualestatin H5 is reported. Key features of the synthesis include the following: (1) highly diastereoselective n-alkylation of a tartrate acetonide enolate and subsequent oxidation-hydrolysis to provide an asymmetric entry to a β-hydroxy-α-ketoester motif; (2) facilitation of Rh(II)-catalyzed cyclic carbonyl ylide formation-cycloaddition by co-generation of keto and diazo functionality through ozonolysis of an unsaturated hydrazone; and (3) stereoretentive Ni-catalyzed Csp3-Csp2 cross-electrophile coupling between tricarboxylate core and unsaturated side chain to complete the natural product.

Understanding Electron Transport in Disk-Shaped Triphenylene-Tris(naphthaleneimidazole)s through Structural Modification and Theoretical Investigation.

Disk-shaped molecules with large aromatic π-surfaces are a class of organic semiconductors in which the charge-carrier transport properties could be greatly facilitated by preferred intermolecular stacking of the π-surfaces. The optical and electronic properties are not only determined by the core aromatic structure of these disk-shaped molecules but are also strongly dependent on the side chains, which directly impact the molecular self-assembly behavior in condensed phases. Triphenylene-tris(naphthaleneimidazole) (TP-TNI) is a recently reported n-type semiconductor featuring a large π-core and branched side chains, with an electron-transporting mobility reaching 10-4 cm2 V-1 s-1. To further improve material performance, a detailed study is needed to understand the dependence of carrier transport properties on both the core electronic structure and side chain. Here, we present the detailed synthesis and characterization of a TP-TNI derivative bearing linear side chains, which has demonstrated a field-effect electron-transport mobility of up to 1.3 × 10-3 cm2 V-1 s-1. The more than 1 order improvement in electron-transport properties over the branched side chain homologue can be correlated to ordered twisted packing in the thin film, as revealed by in situ variable temperature grazing incidence wide-angle X-ray scattering studies. In-depth theoretical understanding of the frontier orbitals, reorganization energies, and charge-transfer integrals of TP-TNI molecules has provided further insight into the relationship between the molecular stacking geometry and charge-transport properties.

Fluorinated and Thermo-Cross-Linked Polyhedral Oligomeric Silsesquioxanes: New Organic-Inorganic Hybrid Materials for High-Performance Dielectric Application.

A fluorinated and thermo-cross-linked polyhedral oligomeric silsesquioxane (POSS) has been successfully synthesized by thermal polymerization of a fluorinated POSS monomer having an inorganic silsesquioxane core and organic side chains bearing thermo-cross-linkable trifluorovinyl ether groups. This new inorganic-organic hybrid polymer shows high thermostability with a 5 wt % loss temperature of 436 °C, as well as good transparency (a sheet with an average thickness of 1.5 mm shows high transmittance of 92% varying from 400 to 1100 nm). Moreover, the polymer exhibits both low dielectric constant (<2.56) and low dissipation factor (<3.1 × 10-3) in a wide range of frequencies from 40 Hz to 30 MHz even at a high frequency of 5 GHz. The polymer also shows low water uptake (<0.04%) and low Dk (near 2.63) after immersing it in water at room temperature for 3 days. These data imply that this polymer is very suitable to be utilized as a high-performance dielectric material for fabrication of high-frequency printed circuit boards or encapsulation resins for integrated circuit dies in the microelectronic industry. Furthermore, this work also provides a route for the preparation of fluorinated POSS-based polymers.

Revealing the Intermolecular Interactions of Asphaltene Dimers by Quantum Chemical Calculations

Understanding the nature of non-covalent interactions (NCIs) between asphaltene molecules is not only theoretically interesting but also important for practical application. We performed quantum chemical calculations to reveal the configuration feature and intermolecular interaction characteristics of asphaltene dimers using three representative asphaltene model compounds and their derivatives. The frontier molecular orbitals and electrostatic potential map of the model asphaltenes were analyzed to reveal the nature of interaction between the asphaltene monomers. The calculation of binding energies indicates that the stability of asphaltene dimers not only depends upon the number of aromatic rings but also relies on the presence of heteroatoms in the aromatic core and aliphatic side chains, which could change the electrostatic charge distribution on the molecular van der Waals surface. In addition, NCIs and the natural bond order analysis method were used to identify the interactions that promote the form...

Synthesis and structure–activity relationship studies of phenolic hydroxyl derivatives based on quinoxalinone as aldose reductase inhibitors with antioxidant activity

To enhance aldose reductase (ALR2) inhibition and add antioxidant ability, phenolic hydroxyl was introduced both to the quinoxalinone core and C3 side chain, resulting in a series of derivatives as ALR2 inhibitors. Biological activity tests suggested that most of the derivatives were potent and selective inhibitors with IC50 values ranging from 0.059 to 6.825μM, and 2-(3-(4-hydroxystyryl)-7-methoxy-2-oxoquinoxalin-1(2H)-yl)acetic acid (6b) was the most active. Particularly, it was encouraging to find that some derivatives endowed with obvious antioxidant activity, and among them the phenolic 3,4-dihydroxyl compound 6f with 7-hydroxyl in the quinoxalinone core showed the most potent activity, even comparable with the well-known antioxidant Trolox. Structure-activity relationship and docking studies highlighted the importance of phenolic hydroxyl both in C3 side chain and the core structure for constructing potent ALR2 inhibitors with antioxidant activity.