Peripheral Chains Research Articles

Giant Thermosalient Effect in a Molecular Single Crystal: Dynamic Transformations and Mechanistic Insights.

The exploration of mechanical motion in molecular crystals under external stimuli is of great interest because of its potential applications in diverse fields, such as electronics, actuation, or sensing. Understanding the underlying processes, including phase transitions and structural changes, is crucial for exploiting the dynamic nature of these crystals. Here, we present a novel organic compound, PT-BTD, consisting of five interconnected aromatic units and two peripheral alkyl chains, which forms crystals that undergo a drastic anisotropic expansion (33% in the length of one of its dimensions) upon thermal stimulation, resulting in a pronounced deformation of their crystal shape. Remarkably, the transformation occurs while maintaining the single-crystal nature, which has allowed us to follow the crystal-to-crystal transformation by single-crystal analysis of the initial and expanded polymorphs, providing valuable insights into the underlying mechanisms of this unique thermosalient behavior. At the molecular level, this transformation is associated with subtle, coordinated conformational changes, including slight rotations of the five interconnected aromatic units in its structure and increased dynamism in one of its peripheral alkyl chains as the temperature rises, leading to the displacement of the molecules. In situ polarized optical microscopy reveals that this transformation occurs as a rapidly advancing front, indicative of a martensitic phase transition. The results of this study highlight the crucial role of a soft and flexible structural configuration combined with a highly compact but loosely bound supramolecular structure in the design of thermoelastic materials.

A non-symmetric room-temperature tristriazolotriazine liquid crystal

Tristriazolotriazine (TTT) has emerged as an easily accessible electron-deficient heterocyclic core for discotic liquid crystals (LCs). Materials that are liquid-crystalline at room temperature, i.e., do not crystallize in ambient conditions, are of particular interest when the LC state is prone to offer advantages in optoelectronic devices, e.g., for anisotropic charge or exciton transport, or anisotropic light emission. However, there has been no report of non-symmetric TTT LCs, i.e., with unequal arms. Here, we report two non-symmetric compounds derived from the TTT core. Their non-symmetry, combined with a high number of peripheral alkyl chains, is found to promote Colh mesomorphism over a broad temperature range including room temperature. The non-symmetry also induces an increase in the emission quantum yield, compared to symmetric analogs.

Synthesis, Thermotropic Properties, and Applications of Porphyrin-based Liquid Crystals: A Comprehensive Review

Abstract: Research on novel discotic molecules, which consist of a rigid core with flexible peripheral chains, has gained much attention due to their crucial role as organic photovoltaic materials, organic field-effect transistors, and semiconductors for photocurrent generation, as well as the possibility of their other optoelectronic applications. This review article describes the developments in fundamental design ideas and synthetic approaches of porphyrin-based meso and beta-substituted liquid crystals. In addition, the current review highlights the various structural alterations made by the researchers in the field of porphyrin-based mesogens and changes in properties, both for materials intended for commercially successful liquid crystal displays, including other applications, and for more basic purposes of demonstrating structure-property relationships.

Neem leaf glycoprotein binding to Dectin-1 receptors on dendritic cell induces type-1 immunity through CARD9 mediated intracellular signal to NFκB

BackgroundA water-soluble ingredient of mature leaves of the tropical mahogany ‘Neem’ (Azadirachta indica), was identified as glycoprotein, thus being named as ‘Neem Leaf Glycoprotein’ (NLGP). This non-toxic leaf-component regressed cancerous murine tumors (melanoma, carcinoma, sarcoma) recurrently in different experimental circumstances by boosting prime antitumor immune attributes. Such antitumor immunomodulation, aid cytotoxic T cell (Tc)-based annihilation of tumor cells. This study focused on identifying and characterizing the signaling gateway that initiate this systemic immunomodulation. In search of this gateway, antigen-presenting cells (APCs) were explored, which activate and induce the cytotoxic thrust in Tc cells.MethodsSix glycoprotein-binding C-type lectins found on APCs, namely, MBR, Dectin-1, Dectin-2, DC-SIGN, DEC205 and DNGR-1 were screened on bone marrow-derived dendritic cells from C57BL/6 J mice. Fluorescence microscopy, RT-PCR, flow cytometry and ELISA revealed Dectin-1 as the NLGP-binding receptor, followed by verifications through RNAi. Following detection of β-Glucans in NLGP, their interactions with Dectin-1 were explored in silico. Roles of second messengers and transcription factors in the downstream signal were studied by co-immunoprecipitation, western blotting, and chromatin-immunoprecipitation. Intracellularization of FITC-coupled NLGP was observed by processing confocal micrographs of DCs.ResultsConsidering extents of hindrance in NLGP-driven transcription rates of the cytokines IL-10 and IL-12p35 by receptor-neutralization, Dectin-1 receptors on dendritic cells were found to bind NLGP through the ligand’s peripheral β-Glucan chains. The resulting signal phosphorylates PKCδ, forming a trimolecular complex of CARD9, Bcl10 and MALT1, which in turn activates the canonical NFκB-pathway of transcription-regulation. Consequently, the NFκB-heterodimer p65:p50 enhances Il12a transcription and the p50:p50 homodimer represses Il10 transcription, bringing about a cytokine-based systemic-bias towards type-1 immune environment. Further, NLGP gets engulfed within dendritic cells, possibly through endocytic activities of Dectin-1.ConclusionNLGP’s binding to Dectin-1 receptors on murine dendritic cells, followed by the intracellular signal, lead to NFκB-mediated contrasting regulation of cytokine-transcriptions, initiating a pro-inflammatory immunopolarization, which amplifies further by the responding immune cells including Tc cells, alongside their enhanced cytotoxicity. These insights into the initiation of mammalian systemic immunomodulation by NLGP at cellular and molecular levels, may help uncovering its mode of action as a novel immunomodulator against human cancers, following clinical trials.

Alpine blooming of “snow fleas”: the importance of snow for Alpine springtails (Hexapoda: Collembola) ecology and biodiversity

Springtails can occur in large populations on the snow surface. This peculiar habitat hosts specialized winter-active springtails living in colonies and using this seasonal habitat for feeding, effective dispersal and migration. Snow-active species have never been studied in Southern European Alps: the aim of this work is to study snow-active springtails of Adamello-Brenta Nature Park (“PNAB”; Italy), a peripheral mountain range of relevant biogeographic interest using integrative taxonomy. Springtail “bloomings” were sampled for 17 months by an environmental assistant of the park. Nine assemblages of springtails were found when temperatures were higher than 0 °C; eight were monospecific, with a total of five species found. The snow-active springtail fauna found includes both common Central-Northern European nival species like Desoria hiemalis (first record for Italy, although genetically differentiated from Northern Alps populations), Ceratophysella sigillata (known in Italy mainly from caves) and three species likely new to science (Hypogastrura cf. kelmendica sp1, Hypogastrura cf. kelmendica sp2, H. cf. peloponnesica, all belonging to the Hypogastrura socialisgroup). Snow is an important ephemeral habitat for springtails, for the biodiversity hosted and for its importance as an ecological corridor. We could hypothesize that snow, especially in peripheral mountain chains, acts as a fragmentary ephemeral habitat for those cold-adapted springtails. This could constitute a relevant aspect to take into consideration for conservation biology, especially in the context of the ongoing climate change. On the other hand, the Alpine chain probably acts as an ecological barrier for nival species, since isolated species and populations were found in PNAB.Graphical

Solvent Geometry Regulated J- and H-Type Aggregates of Photoswitchable Organogelator: Phase-Selective Thixotropic Gelation and Oil Spill Recovery.

We demonstrate supramolecular polymerization and formation of 1D nanofiber of azobenzene based organogelator (AZO-4) in cyclic hydrocarbon solvents (toluene and methylcyclohexane). The AZO-4 exhibits J- and H-type aggregates in toluene: MCH (9 : 1) and MCH: toluene (9 : 1) respectively. The type of aggregate was governed by the geometry of the solvents used in the self-assembly process. The J-type aggregates with high thermal stability in toluene is due to the enhanced interaction of AZO-4 π- surface with the toluene π-surface, whereas H-aggregate with moderate thermal stability in MCH was due to the interruption of the cyclic hydrocarbon in van der Waals interactions of peripheral chains of AZO-4 molecule. The light induced reversible photoisomerization is observed for both J- and H-aggregates. The macroscopic property revealed spontaneous and strong gelation in toluene preferably due to the strong interactions of the AZO-4 nanofibers with the toluene solvent molecules compared to the MCH. The rheological measurements revealed thixotropic nature of the gels by step-strain experiments at room temperature. The thermodynamic parameter (ΔHm) of gel-to-sol transition was determined for all the gels to get more insight into the gelation property. Furthermore, the phase selective gelation property was extended to the oil spill recovery application using diesel/water and petrol/water mixture.

Entropy-Enthalpy Compensation in Solvent Geometry Regulated Supramolecular Polymerization of Luminescent Napthalimide via a Non-Cooperative, Isodesmic Mechanism.

Supramolecular polymers of π-conjugated systems are an important class of materials with fascinating functions and properties originated from the dynamic behavior and highly ordered molecular organizations. Here, a donor-π-acceptor based functionalized luminescent napthalene monoimide (NMI) undergoes J-type self-assembly by non-covalent interactions via a non-cooperative, isodesmic mechanism to form supramolecular 1D nanowire. The fundamental insights into the thermodynamics regulating the supramolecular polymerization were derived through the fitting of the isodesmic model to variable temperature UV/Vis data in linear (dodecane) and nonliner hydrocarbon (decalin) based solvents. This shows a significant role of entropy-enthalpy compensation in solvent geometry-regulated formation and stabilization of supramolecular polymer. Furthermore, we have quantitively estimated the influence of solvent geometry and found that NMI forms stronger self-assembly and spontaneous gel in linear hydrocarbon based solvent compared to nonliner one and thereby substantially increases the degree of polymerization in linear hydrocarbon solvent (dodecane). This is accredited to the effective influence of the linear hydrocarbon solvent molecules in the polymerization process by favourable van der waals interactions with the peripheral alkyl chains of the NMI monomers in contrast to unfavourable interaction of nonliner hydrocarbon solvent due to geometry mismatch.

Supramolecular polymerization and bulk properties relationship in ester-functionalized N-annulated perylenediimides.

The synthesis of a series of N-annulated perylenediimides (NPDIs) 1-4 with an ester group and an alkyl spacer of different length in the peripheral chains was carried out, and the influence of the side chain architecture on the self-assembly, both in solution and in the solid state, was investigated. Solution studies evidenced that the carbonyl group plays a key role in the supramolecular organization of these derivatives, changing from an H-type isodesmic polymerization (4) to a J-type cooperative process as the spacer length decreases (1-3). On the other hand, bulk assays revealed an odd-even effect that correlates with the length of the alkyl spacer. Whereas the odd-spaced derivatives (2 and 4) organize in a disordered columnar hexagonal fashion, the even-spaced ones (1 and 3) show the formation of multiple crystalline (and liquid crystalline) structures. The results presented herein highlight the importance of side chain functionalization in the design of building blocks for in-solution and bulk purposes.

Supramolecular polymerization of [6]helicene-based cyano-luminogens: on the overall efficiency of self-assembled circularly polarized emitters.

The synthesis of the [6]helicene-based luminophores 1 and 2 is reported. These chiral systems, endowed with cyano-stilbene fragments, form supramolecular polymers by the operation of intermolecular H-bonding interactions between the amides present in the peripheral side chains. The dissimilar disubstitution of 1 and 2 plays a crucial role in their self-assembling features. Thus, 1 does not show an efficient π-stacking of the central aromatic moiety. Instead, its self-assembling process results in a zig-zag arrangement of the monomeric units to form the aggregated species. On the other hand, 2 presents an efficient overlap of the aromatic backbones that affords a co-facial arrangement of the monomeric units. The solvent-dependent studies indicate that both [6]helicenes self-assemble following a cooperative supramolecular polymerization mechanism with a higher degree of cooperativity and stability for compound 2. The enantioenriched samples of both 1 and 2 display a rich dichroic pattern that changes when the supramolecular polymerization takes place. Furthermore, the presence of the cyano-stilbene moieties gives rise to an aggregation induced emission effect. The inherent chirality of both the monomeric and aggregated species of 1 and 2 provides the systems with CPL-emitting properties, presenting a remarkable overall CPL-efficiency, quantified by the BCPL parameter, that increases upon supramolecular polymerization.

Temperature-dependent hole mobility in pyrene-thiophene-based room-temperature discotic liquid crystals.

π-Conjugated pyrene-thiophene-based room-temperature discotic liquid crystals armed with four peripheral aliphatic chains are reported to study their potential use in a hole-transporting organic semiconductor. The charge carrier mobility studies using the ToF method revealed room temperature hole mobility in the order of 10-4 cm2 V-1 s-1 for both mesogens. However, the mobility values for compound 1a were observed in the order of 10-3 cm2 V-1 s-1 at high temperatures. Such molecular systems can potentially be used in nonlinear organic electronic applications.

Distinct bulk emission properties of the hexacatenar molecules by varying the polarity of peripheral chains

The molecular engineering of chain polarity in hexacatenar molecules, which are composed of an identical D–A–D chromophore leads to distinct emission properties in the bulk state.

Probing conformational properties of conjugated polymers in dilute solutions under variable solvent quality via coarse‐grained modeling

AbstractConjugated polymers (CPs), characterized by rigid conjugation backbones and flexible peripheral side chains, hold significant promise in various organic optoelectronic applications. In this study, we employ coarse‐grained molecular dynamics (CG‐MD) simulations to investigate the intricate interplay of solvent quality, temperature, and chain architecture (e.g., side‐chain length and molecular mass) on the conformational behaviors of CPs in dilute solutions. Our research uncovers distinctive conformational behaviors under varying solvent conditions, highlighting the versatile nature of polymer chains, which can adopt extended configurations in good solvents and transition to aggregated states in poor solvents. Additionally, the mass scaling exponent , a robust structural descriptor, consistently described CPs behavior across diverse architectures and solvent conditions. Furthermore, our study shows that a CP with longer side‐chain exhibits improved solubility, which is further confirmed by experimental observations. Moreover, our analysis of the shape descriptor provided valuable insights into the symmetry and dimensionality of CPs under varying solvent conditions. These findings offer a comprehensive understanding of conformational behaviors of CPs in dilute solution, which are helpful in guiding the conformational design of polymer for specific applications.

Shedding Light on Highly Emissive 1,4-Dihydropyrrolo[3,2-b]pyrrole Derivatives: Synthesis and Aggregate-Dependent Emission.

Three tetraaryl-1,4-dihydropyrrolo[3,2-b]pyrrole derivatives containing different number of long alkoxy chains (2, 4 and 6) were synthesized, characterized and applied in Organic Light Emitting Diodes (OLEDs). The compounds showed good emission properties with Photoluminescence Quantum Yields (PLQYs) higher than 80 % in solution and 50 % in solid state (thin film). The solvatochromism results revealed a pronounced vibronic emission in methylcyclohexane and toluene, characterized by two distinct sharp emission peaks and a small redshift in the following order: methylcyclohexane>toluene>dichloromethane>tetrahydrofuran>acetonitrile. Also, the compounds formed aggregates with redshifted emission, which can be attributed to excimer formation. This phenomenon was observed in solutions containing 90 % water and with the concentration variation in methylcyclohexane (MCH). Compounds with a greater number of peripheral chains showed the capacity to keep hexagonal columnar organization in films after fast cooling from liquid state. OLEDs fabricated with these compounds showed turn-on voltages lower than 4.0 V, with luminance higher than 1400 cd m-2 , electroluminescence spectra with Full Width at Half Maximum lower than 70 nm and maximum External Quantum Efficiency between 7.2 % and 4.3 %. Overall, this shows that the 1,4-dihydropyrrolo[3,2-b]pyrrole moiety is promising for applications where luminescence is paramount, as in organic light-emitting devices.

Supramolecular Block Copolymers from Tricarboxamides. Biasing Co-assembly by the Incorporation of Pyridine Rings.

The synthesis of a series of triangular-shape tricarboxamides endowed with three picolin or nicotin (compounds2and3) or just one nicotine unit (compound4) is reported and their self-assembling features investigated. The pyridine rings make compounds2-4electronically complementary with our previously reported OPETA1to form supramolecular copolymers.C3-symmetric tricarboxamide2forms highly stable intramolecular five-membered pseudocycles that impedes its supramolecular polymerization intopoly-2and the co-assembly with1to yield copolymerpoly-1-co-2. On the other hand,C3-symmetric tricarboxamide3readily formpoly-3with great stability but unable to form helical supramolecular polymers despite the presence of the peripheral chiral side chains. The copolymerpoly-1-co-3can only be obtained by a previous complete disassembly of the constitutive homopolymers in CHCl3. Helicalpoly-1-co-3arises in a process involving the transfer of the helicity from racemicpoly-1topoly-3, and the amplification of asymmetry from chiralpoly-3topoly-1. Importantly,C2v-symmetric4, endowed with only one nicotinamide moiety and three chiral side chains, self-assembles intoP-type helical supramolecular polymer (poly-4) in a thermodynamically controlled cooperative process. The combination ofpoly-1andpoly-4generates chiral supramolecular copolymerpoly-1-co-4, whose blocky microstructure has been investigated by applying the supramolecular copolymerization model.

Supramolecular Block Copolymers from Tricarboxamides. Biasing Co‐assembly by the Incorporation of Pyridine Rings

AbstractThe synthesis of a series of triangular‐shaped tricarboxamides endowed with three picoline or nicotine units (compounds 2 and 3, respectively) or just one nicotine unit (compound 4) is reported, and their self‐assembling features investigated. The pyridine rings make compounds 2–4 electronically complementary with our previously reported oligo(phenylene ethynylene)tricarboxamides (OPE‐TA) 1 to form supramolecular copolymers. C3‐symmetric tricarboxamide 2 forms highly stable intramolecular five‐membered pseudocycles that impede its supramolecular polymerization into poly‐2 and the co‐assembly with 1 to yield copolymer poly‐1‐co‐2. On the other hand, C3‐symmetric tricarboxamide 3 readily forms poly‐3 with great stability but unable to form helical supramolecular polymers despite the presence of the peripheral chiral side chains. The copolymer poly‐1‐co‐3 can only be obtained by a previous complete disassembly of the constitutive homopolymers in CHCl3. Helical poly‐1‐co‐3 arises in a process involving the transfer of the helicity from racemic poly‐1 to poly‐3, and the amplification of asymmetry from chiral poly‐3 to poly‐1. Importantly, C2v‐symmetric 4, endowed with only one nicotinamide moiety and three chiral side chains, self‐assembles into a P‐type helical supramolecular polymer (poly‐4) in a thermodynamically controlled cooperative process. The combination of poly‐1 and poly‐4 generates chiral supramolecular copolymer poly‐1‐co‐4, whose blocky microstructure has been investigated by applying the previously reported supramolecular copolymerization model.

Non-Covalent Free-Standing Monolayer Nanoarchitectonics of Heterocoronene-Based Discotic Liquid Crystal Molecules

With excellent charge carrier mobility, tendency to form long-range assembly with self-healing ability, and remarkable chemical and mechanical stability, highly conjugated discotic molecules constitute an important class of materials for electronic applications. Here, we report formation of the stable free-standing molecular film of heterocoronene-based discotic liquid crystal (DLC) molecules, held solely by supra-molecular non-covalent interactions. The films of monolayer thickness (∼4 nm) were lifted from Langmuir trough directly onto a circular ring of diameter up to 2 mm as well as onto TEM grids. Films remain free-standing up to a macroscopic length scale, as revealed by optical and secondary electron microscopy, presumably due to the synergistic effect of intermolecular π–π interactions and the dispersion forces between the peripheral alkyl chains as well as their interdigitation. The monolayer is more than 97% transparent in the visible range. Further, resistive switching measurements carried out on the monolayer DLC film transferred on a silver substrate revealed electrochemical metallization to be the governing process. The switching time was found to decrease exponentially with voltage indicating nucleation to be a possible rate-limiting step. We anticipate that the method presented here will facilitate utilization of such non-covalent free-standing films in flexible memristor and nano-electromechanical systems.

Influence of monohalogenated flexible tails on the mesomorphism of triphenylene-based discotics

A series of triphenylene-based discotic liquid crystals (DLCs) modified by fluorination or chlorination at the end of peripheral flexible chains were examined in this work. DLC derivatives containing one mono fluorine or chlorine-substituted flexible chain 4a-e and six mono fluorine or chlorine-substituted flexible chains 8a & 8b, 10a & 10b were mainly synthesized and molecular structures confirmed by 1H NMR, 19F NMR and MALDI-TOF MS. The mesogenic properties of the obtained compounds were further studied by differential scanning calorimetry (DSC), polarizing optical microscopy (POM) and X-ray diffraction (XRD). Impressively, compounds 4a-e were found exhibiting hexagonal columnar phases and the π-π stacking distances of 4a-e were lower than that of the parent molecule HAT5. Due to the influence of atomic radius and molecular symmetry, the mesophase stability of the fluorinated triphenylene compounds was greater than the chlorinated ones. Through the modification of the side chain, the self-assembly behavior of triphenylene was stronger and the intracolumnar distance was decreased, which may give rise to a higher charge transport mobility. Compound 10b showed self-assembly behavior and formed a spherulite texture that could also remain orderly until room temperature. This is rare in reported DLCs and it might be applied as active components of in electronic devices. These ordered stacked discotic molecules may exhibit improved charge carrier mobility as semiconducting materials.

Phosphates Induced H-Type or J-Type Aggregation of Cationic Porphyrins with Varied Side Chains.

Non-covalent interactions have been extensively used to fabricate nanoscale architectures in supramolecular chemistry. However, the biomimetic self-assembly of diverse nanostructures in aqueous solution with reversibility induced by different important biomolecules remains a challenge. Here, we report the synthesis and aqueous self-assembly of two chiral cationic porphyrins substituted with different types of side chains (branched or linear). Helical H-aggregates are induced by pyrophosphate (PPi) as indicated by circular dichroism (CD) measurement, while J-aggregates are formed with adenosine triphosphate (ATP) for the two porphyrins. By modifying the peripheral side chains from linear to a branched structure, more pronounced H- or J-type aggregation was promoted through the interactions between cationic porphyrins and the biological phosphate ions. Moreover, the phosphate-induced self-assembly of the cationic porphyrins is reversible in the presence of the enzyme alkaline phosphatase (ALP) and repeated addition of phosphates.

Liquid-Crystalline Naphthalene and Perylene Bisimides with a D2–π2–A Architecture for High-Mobility Organic Field-Effect Transistors

We designed and synthesized four naphthalene and perylene bisimide-based imidazole-containing liquid-crystalline (NI and PI) derivatives based on a donor−π–acceptor−π–donor (D2–π2–A) architecture. These compounds bear 10 flexible peripheral chains to ensure liquid crystallinity and solution processability making them suitable to use as organic semiconductors. All four compounds stabilized different columnar phases. Higher thermal stability and lower band gaps were also observed in both NI and PI derivatives. NI derivatives showed larger Stokes shifts, while PI derivatives exhibited very high molar extinction coefficients. Two solution-processable liquid-crystalline compounds (NI-12 and PI-12) were utilized for the fabrication of organic field-effect transistors, exhibiting a hole mobility of 1.99 cm2/V·s for NI-12 and 0.63 cm2/V·s for PI-12 derivatives at room temperature in normal air conditions.

Heparin Induced Dual Mode Luminescence Modulation of Organic Nanoparticles and Efficient Energy Transfer.

Amphiphilic di-cationic fumaronitrile derivatives with peripheral n-alkyl chains formed organic nanoparticles (NPs) through self-assembly in aqueous media. The NPs exhibited enhanced luminescence in both steady-state and delayed mode in comparison to their molecularly dissolved state. Due to the presence of the multivalent array of positive charges on their surface, they were found to bind heparin, a bio-polyanion which is routinely employed during surgery as an anticoagulant. The electrostatically driven co-assemblies resulted in a significant enhancement in the steady-state and delayed luminescence of the NPs. This provided a highly sensitive detection of the polyanion in aqueous buffer as well as in highly competitive serum and plasma media. Furthermore, and most notably, the heparin based co-assemblies were found to act as efficient donors exhibiting fluorescence resonance energy transfer (FRET) to acceptor dyes with the energy transfer efficiency reaching up to 88%.