Flexible Alkyl Chains Research Articles

A turn-on fluorescence probe based on post-modified metal–organic frameworks for highly selective and fast-response hypochlorite detection

Hypochlorite/hypochlorous acid has been commonly regarded as one of the most vital reactive oxygen species in various physiological and pathological processes. However, the highly efficient detection of OCl− still remains a challenging work. Here, we fabricated a fluorescent MOF-based OCl− probe (ZIF-90-BA) by post-functionally modifying ZIF-90 with the Schiff base group. ZIF-90-BA features water stability, porous structures and functional sites. This probe was successfully used for OCl− turn-on fluorescence sensing. The Schiff base group on the ZIF-90-BA could be oxidized by OCl− and the flexible alkyl chain would put off, resulting in the turn-on fluorescence behavior. ZIF-90-BA exhibited high selectivity over other potentially interfering species, and it showed high sensitivity (detection limit: 6.25 μM) and fast response (15 s). It is anticipated that ZIF-90-BA can be a promising material for OCl− fluorescence sensing.

Confinement-driven radical change in a sequence of rotator phases: a study on n-octacosane.

Rotator-phase forming n-alkanes have been studied extensively in both their bulk state and in nanoconfinement. While some alkanes maintain their bulk-state rotator phases in nanoconfinement albeit with increased disorder, there are others exhibiting new rotator phases upon confinement. We present here a temperature dependent X-ray diffraction (XRD) and differential scanning calorimetric (DSC) study on n-octacosane (C28H58), which almost completely loses its bulk state RIV phase and undergoes complete disappearance of its RIII phase. In their place, when confined in cylindrical anodized alumina nanopores, a phase highly resembling the hexatic mesophase is formed at a higher temperature and the RI rotator phase at a lower temperature. The effects of finite size, interfacial interactions with the host matrix and alkyl chain flexibility are used to provide an explanation for such unexpected behaviour.

Stronger host-guest binding does not necessarily give brighter particles: a case study on polymeric AIEE-tunable and size-tunable supraspheres.

Supraspheres were prepared from a pillar[5]arene-based linear polymer (the host) and several multitopic guests. According to host-guest binding studies in nanosystems, the optical and structural properties (fluorescence capability, density, and particle size) of the nanoparticles were correlated not with the host-guest binding affinities, but with the relative fluorescence quantum yield.

Anchoring a Sulfonate Group to an Electron‐Transporting Molecule by an Alkyl Chain and Its Use as the Counter Anion in a Phosphorescent Cationic Iridium Complex

An electron-transporting anion prepared by anchoring a sulfonate group onto an electron-transporting molecule through a flexible alkyl chain and its use as the counter anion in a cationic iridium complex is reported. The flexible alkyl chain improves the solubility of the bulky anion in water or in polar organic solvents. The anion exhibits similar photophysical and electrochemical properties to the parent electron-transporting molecule. Within the complex, the anion does not disturb the phosphorescence of the cation in the solid film. Solution-processed small-molecule organic light-emitting diodes (OLEDs) using the complex as the dopant show superior performances over the reference device using the conventional complex with a PF6 - counter anion. It is revealed that anchoring anionic groups to optoelectronically active molecules with flexible alkyl chains is a feasible approach to develop optoelectronically active anions for assembling ion pairs with advanced optoelectronic properties.

Asymmetric Fullerene Nanosurfactant: Interface Engineering for Automatic Molecular Alignments.

Since the molecular self-assembly of nanomaterials is sensitive to their surface properties, the molecular packing structure on the surface is essential to build the desired chemical and physical properties of nanomaterials. Here, a new nanosurfactant is proposed for the automatic construction of macroscopic surface alignment layer for liquid crystal (LC) molecules. An asymmetric nanosurfactant (C60 NS) consisted of mesogenic cyanobiphenyl moieties with flexible alkyl chains and a [60]fullerene nanoatom is newly designed and precisely synthesized. The C60 NS directly introduced in the anisotropic LC medium is self-assembled into the monolayered protrusions on the surface because of its amphiphilic nature originated by asymmetrically programmed structural motif of LC-favoring moieties and LC-repelling groups. The monolayered protrusions constructed by the phase-separation and self-assembly of asymmetric C60 NS nanosurfactant in the anisotropic LC media amplify and transfer the molecular orientational order from surface to bulk, and finally create the automatic vertical molecular alignment on the macroscopic length scale. The asymmetric C60 NS nanosurfactant and its self-assembly described herein can offer the direct guideline of interface engineering for the automatic molecular alignments.

Environment-Adaptive Coassembly/Self-Sorting and Stimulus-Responsiveness Transfer Based on Cholesterol Building Blocks.

Manipulating the property transfer in nanosystems is a challenging task since it requires switchable molecular packing such as separate aggregation (self‐sorting) or synergistic aggregation (coassembly). Herein, a unique manipulation of self‐sorting/coassembly aggregation and the observation of switchable stimulus‐responsiveness transfer in a two component self‐assembly system are reported. Two building blocks bearing the same cholesterol group give versatile topological structures in polar and nonpolar solvents. One building block (cholesterol conjugated cynanostilbene, CCS) consists of cholesterol conjugated with a cynanostilbene unit, and the other one (C10CN) is comprised of cholesterol connected with a naphthalimide group having a flexible long alkyl chain. Their assemblies including gel, crystalline plates, and vesicles are obtained. In gel and crystalline plate phases, the self‐sorting behavior dominates, while synergistic coassembly occurs in vesicle phase. Since CCS having the cyanostilbene group can respond to the light irradiation, it undergoes light‐induced chiral amplification. C10CN is thermally responsive, whereby its supramolecular chirality is inversed upon heating. In coassembled vesicles, it is interestingly observed that their responsiveness can be transferred by each other, i.e., the C10CN segment is sensitive to the light irradiation, while CCS is thermoresponsive. This unprecedented behavior of the property transfer may shine a light to the precise fabrication of smart materials.

Versatile Adamantane-based porous polymers with enhanced microporosity for efficient CO2 capture and iodine removal

A series of multifunctional nanoporous organic polymers with high microporosity have been successfully synthesized via Friedel-Crafts alkylation and Scholl coupling reactions. Porous properties are well-controllable by simply regulating the lengths and rigidities of linkers, where the rigid tetrahedral building block, i.e. 1,3,5,7-tetraphenyladamantane, knitted with flexible alkyl chains leads to a hierarchically porous structure of NOP-53. Such amorphous materials derived from the high rigid building block achieve high surface areas (1178m2g−1 for NOP-54) and substantially improved micro-pore volumes (0.86cm3g−1, Vmicro/Vtotal=65%). The as-made porous network NOP-54 featuring highest microporosity can uptake 14.2wt% CO2 at 273K and 1bar, and good selectivity ratios for CO2 adsorption over N2 (56.1) and CH4 (13.9) at 273K are achieved. Furthermore, such polymers display excellent iodine vapor uptake of up to 202wt% and shows remarkable capability as iodine sorbent in solution. These results are significant for constructing accessible aromatic networks with promoted microporosity targeting for environmental challenges.

Synthesis, liquid-crystalline, photophysical and chemosensor properties of oxadiazole/thiadiazole-based amphiphiles with glycerol groups

Two series of heterocycle-based mesogens consisting of a long 2,5-diphenyl-1,3,4-oxadiazole/thiadiazole rigid core with three lipophilic and flexible alkyl chains at one end and a polar glycerol group at the opposite end have been synthesized via one pot cyclization reaction. These compounds were investigated by polarizing optical microscopy (POM), differential scanning calorimetry (DSC), X-ray scattering, cyclic voltammetry, UV–vis spectroscopy and photoluminescence measurements. Upon elongation of the alkyl chains, a transition from hexagonal columnar phase to Pm3¯n-type cubic phase was observed in both series. Oxadiazole series are blue luminescent LCs with binding selectivity to Li+, while thiadiazole series are blue-green luminescent LCs with binding selectivity to Fe3+.

CBP derivatives dendronized self-host TADF dendrimer: Achieving efficient non-doped near-infrared organic light-emitting diodes

A self-host thermally activated delayed fluorescence (TADF) dendrimer, namely MPPA-MCBP, for solution-processed nondoped near-infrared organic light-emitting diodes (OLEDs) was designed and synthesized, in which the bipolar CBP derivatives is introduced to render balanced charge transportation. This structural modification that the dendrons are well-bounded by the flexible alkyl chains, which can efficiently reduce the intermolecular interactions between the emissive cores and ensure the stable operation of the solution-processed device. As a result of the spin-coated OLEDs employing MPPA-MCBP as the host-free near-infrared emitter exhibits a highest external quantum efficiency (EQE) of 0.62% and a peak wavelength at 698 nm, which indicates the design of self-host TADF dendrimers containing bipolar dendrons will be a promising strategy to improve the electroluminescent performance of solution-processed nondoped device.

Self-assembly, AIEE and mechanochromic properties of amphiphilic α-cyanostilbene derivatives

A series of amphiphilic α-cyanostilbene derivatives consisting of an α-cyanostilbene rodlike core with lipophilic and flexible alkyl chains at one end and a polar glycerol group at the opposite end have been synthesized and investigated by polarizing microscopy, DSC, X-ray scattering, SEM, UV-vis spectroscopy and photoluminescence measurements. These compounds can self-assemble into liquid crystalline phase sequence of SmA- Colhex/p6mm- CubI/Pm3¯n in the bulk states and multistimuli responsive organogels in organic solvents. They have reversible photoresponsive properties in solution, liquid crystalline state and gel state. They also show aggregation-induced enhanced emission (AIEE) property, meanwhile, they present excellent mechanochromic behavior and have a good reversibility of fluorescence conversion upon grinding-fuming process.

Strengthening Phosphoric Acid Doped Polybenzimidazole Membranes with Siloxane Networks for Using as High Temperature Proton Exchange Membranes

Two silane compounds, i.e., ((chloromethyl)phenylethyl)trimethoxysilane (Ph‐Si) and 3‐chloropropyltriethoxysilane (Pr‐Si), are employed as covalent crosslinkers to fabricate high temperature proton exchange membranes based on polybenzimidazole (PBI) in order to better understand the correlation between the structure and the property of the crosslinked membranes. All the crosslinked PBI membranes display longer morphology durability over the neat PBI membrane toward the radical oxidation. The crosslinked membranes with the crosslinker containing a rigid group of phenylene (PBI‐Ph) show superior acid doping level, high conductivity, and excellent mechanical strength simultaneously, comparing to those with the crosslinker having a flexible alkyl chain (PBI‐Pr) and the pristine PBI based membrane. The technical feasibility for using as high temperature proton exchange membranes is demonstrated by the acid doped crosslinked PBI‐Ph membranes via fuel cell tests. image

Design, synthesis and insecticidal activity of novel hydrocarbylidene nitrohydrazinecarboximidamides.

Neonicotinoids, among the most important pesticides in recent decades, have played pivotal roles in controlling agricultural pests. However, the toxicity to some environmentally beneficial insects is a cause of concern. The development of novel insecticides safer to these insects is increasingly urgent. A novel series of hydrocarbylidene nitrohydrazinecarboximidamides were designed and synthesised, starting from S-methylisothiourea sulphate. Preliminary bioassays showed that the target molecules exhibited good activities against Lipaphis erysimi (turnip aphid) and Myzus persicae. As shown by initial insecticidal activity data, most of the target compounds had moderate to excellent activities at a concentration of 600 mg L-1 against L. erysimi, and the lethal rate of most compounds exceeded 90%. They were also highly effective against M. persicae. Some of them have shown excellent insecticidal activities, for example, the LC50 values of compounds Ie-02 to Ie-07 were found to be 3.8, 3.0, 2.5, 3.1, 4.1 and 4.0 mg L-1 respectively. Structure-activity relationship analysis indicated that a suitable flexible alkyl chain at the imine point and a Cl-substituted pyridine ring are the most crucial factors affecting the activity. © 2017 Society of Chemical Industry.

Tunable luminescence of cyclometallated platinum(II) derivatives based on novel pyrimidine-contained tridentate Pt(NˆCˆN)Cl complexes

Two novel tridentate Pt(NˆCˆN)Cl complexes, 1a and 2a, with an electron-deficient pyrimidine-contained NˆCˆN tridentate ligand, were synthesized and characterized. Single crystal X-ray diffraction of 1a revealed a cyclometallated square-planar geometry. In the single crystal, 1a adopted a head-to-head dimeric form with the shortest Pt⋯Pt distance of 4.22 Å and π–π stacking affording one-dimensional nanostructure along a-axial direction. Interestingly, in contrast to 1a, Pt⋯Pt interaction of 2a, with a flexible alkyl chain substituent, could be induced by facile solution processable self-assembly, allowing for modulation of luminescence from visible to near-IR (NIR) region.

Bilayers directly scrolling up to form nanotubes via self-assembly of an achiral small molecule.

The self-assembly behavior of a molecule composed of an azobenzene segment, carboxylic-acid group and flexible alkyl chains (denoted by ABA11) was studied as an extension of our proceeding work. We have previously reported that in DMSO solution ABA11 self-assembled into nanotubes starting from nanosheets and experiencing a meta-state of helical ribbons. Herein, we found that changing the solvent can also affect the self-assembly pathway of ABA11 to nanotubes. When DMSO was replaced by ethanol, the nanosheets formed by ABA11 bilayers either directly scrolled up to form nanotubes without a meta-state of helical ribbons at low concentrations, or stacked up to form nanobricks at higher concentrations. In addition, increasing the water content in ethanol can significantly facilitate the formation of the assembled nanostructures.

Bright persistent luminescence from pure organic molecules through a moderate intermolecular heavy atom effect.

Generally, strong phosphorescence always implies a short luminescence lifetime. So, pure organic molecules with strong persistent phosphorescence at room temperature are rarely explored. Here, a new strategy is used to explore strong persistent phosphorescence of carbazole derivatives through an intermolecular moderate heavy atom effect. Flexible alkyl chains were inserted between the heavy atom and carbazole moieties so as to avoid a strong internal heavy atom affect. The results indicate that the photoluminescence properties of crystals strongly depend on molecular stacking in crystal states. Moreover, seven molecules among eight carbazole derivatives exhibit persistent room-temperature phosphorescence in their crystals and the ΦP values of three compounds exceed 9.5%. Notably, when a 6-(4-bromophenoxy)hexyl group is linked to carbazole, the ambient phosphorescent quantum yield reaches 39.5% and the lifetime is as long as 200 ms. Moreover, it emitted white light with a luminescent efficiency of 72.6% owing to the coexistence of strong fluorescence and phosphorescence.

Correction: Bright persistent luminescence from pure organic molecules through a moderate intermolecular heavy atom effect.

Correction for ‘Bright persistent luminescence from pure organic molecules through a moderate intermolecular heavy atom effect’ by Pengchong Xue et al., Chem. Sci., 2016, DOI: 10.1039/c5sc03739e.

Conformational adjustment for high-pressure glass formation of 1-alkyl-3-methylimidazolium tetrafluoroborate.

The conformational stability of 1-alkyl-3-methylimidazolium tetrafluoroborate ([Cnmim][BF4], n = 3-8) under high pressure was investigated using Raman spectroscopy to reveal the preferential role of the alkyl-chain length (n) in high-pressure glass transition. To evaluate this, we determined the intensity ratio (r) and differences in the partial molar volume (ΔVtrans→gauche) between the whole trans and gauche conformers of the [Cnmim] cation using Raman intensities. Interestingly, both values were classified into a two alkyl-chain length region at the border of n = 5. The coulombic interaction (cation-anion interaction) for the conformational stability is the predominant factor below n = 5 (the cation-head portion: alkyl carbon number C < 5), and the alkyl-chain packing effect (cation-cation interaction) is the predominant factor above n = 5 (the cation-tail portion: C > 5). In combination with the conformational preference of the [Cnmim] cation under a high-pressure glassy state, the alkyl chain displays a preferential role, i.e., an increase in the gauche conformer of [Cnmim][BF4] adjusts to avoid crystallization (the conformational adjustment effect). In the presence of the coulombic interaction, the preferential role of the flexible alkyl chain is an important key to elucidate the mechanism of the complicated high-pressure phase transition behavior of ionic liquids.

Design strategy of yellow thermally activated delayed fluorescent dendrimers and their highly efficient non-doped solution-processed OLEDs with low driving voltage

We designed and synthesized two dendrimers TA-Cz and TA-3Cz with TADF characteristics by using non-conjugated aliphatic chains carbazole/tricarbazole as peripheral dendrons. Both dendrimers possess excellent thermal and morphological stabilities. Introduced the phenyl bridge to increase the distance of the emission core TA between donor (D) and acceptor (A) is a promising route to simultaneously achieve small singlet–triplet energy splitting (ΔEST) and enhanced PL quantum yields (PLQYs). Furthermore, non-conjugated aliphatic chains carbazole/tricarbazole dendrons were conveniently introduced to the TADF core, which can effective encapsulate the emission core to restrain the concentration quenching effect and make the fluorescence of the core independent. By utilizing TA-3Cz emitter as the non-doped solution-processed emissive layers, the resulting yellow OLED achieved low driving voltage of 2.4 V and superior external quantum efficiency of 11.8%. Thus, our results here provide a facile strategy to obtain highly efficient non-doped solution-processed OLEDs by employing the reasonable molecular design of the TADF core and the utilization of flexible alkyl chain.

Alkyl‐Chain‐Separated Triphenybenzene ‐ Carbazole Conjugates and their Derived Polymers: Candidates for Sensory, Electrical and Optical Materials

AbstractFour new triphenylbenzene based carbazoles (THPBCz4, THPBCz6, THPBCz8 and THPBCz10) and polycarbazoles (polyTHPBCz4, polyTHPBCz6, polyTHPBCz8 and polyTHPBCz10), have been synthesized. Photoluminescence spectra of the monomers in dichloromethane exhibit two intense bands at 353 and 369 nm. Two additional bands (410 and 435 nm) are also observed due to intermolecular interactions. These bands are more intense in the case of thin films, indicating stronger π‐π stacking interactions in the solid state. Due to the extended π‐conjugation, the polycarbazoles display two main emission bands (495 and 520 nm) which are red shifted as compared to the monocarbazoles. Due to the presence of emissive platforms such as triarylbenzene and carbazole, both monomers and polymers, function as efficient sensors for the detection of polynitroaromatic analytes (PA, DNT, p‐DNB and m‐DNB). The electrochemically polymerized carbazole derivatives showed maximum capacitance of 41 F/g for polyTHPBCz6. The SCLC measurement reveals a maximum mobility of 6 x 10−6 cm2/Vs for polyTHPBCz4 that showed better packing due to flexible alkyl chains that connect the conjugated moieties.

Mesomorphism and flexibility of alkyl chains in chalcone esters

ABSTRACTA novel homologous series of chalconyl ester liquid crystals (LCs): RO−C6H4–CH:CH–COO−C6H4–CO−CH:CH−C6H4–OC10H21 (n) (para) has been synthesized and studied with a view to understanding and establishing the relationship between molecular structure and LC properties with reference to flexibility of the terminal chain. The novel series consists of eleven homologs (C1–C16). The C1 and C2 homologs are nonliquid crystals and the rest of the homologs (C3–C16) are enantiotropic nematic without exhibition of smectic mesophase. Transition and melting temperatures were determined by an optical polarizing microscope equipped with a heating stage. Textures of nematic phases are threaded or Schlieren. Cr-N/I transition curve adopts a zigzag path in a normal manner with overall descending behaviors. The N-I transition curve exhibits a sharp and shorter odd-even effect from C3 to C6 and it diminishes from and beyond C6 for higher homologs of longer n-alkyl chain (R) in more or less or negligible deviating manner from normal descending tendency. Thermal stability for the nematic is 116.4°C and mesophase length ranges from 19°C to 67°C at the C3 and C12 homolog respectively. The LC properties of present novel series are compared with structurally similar analogous series to derive group efficiency order.