Inversion of Supramolecular Helicity in Oligo‐p‐phenylene‐Based Supramolecular Polymers: Influence of Molecular Atropisomerism

The helical organization of oligo‐p‐phenylene‐based organogelators has been investigated by atomic force microscopy, circular and vibrational circular dichroism, and Raman techniques. Whilst OPPs with more than two phenyl rings in the core self‐assemble into left‐handed helices, that with a biphenyl core shows an inversion of the supramolecular helicity depending on the formation conditions through the atropisomerism of the biphenyl central unit. The results presented herein outline a new example of kinetically controlled modulation of supramolecular helicity.     

Numerical simulations of the polymerization reaction of deuterated diacetylene 2,4‐hexadiynylene bis(p‐toluenesulfonate) crystal

In this paper, we developed two types of programs in order to simulate the polymerization reaction of a fully deuterated crystal of diacetylene 2,4‐hexadiynylene bis(p‐toluenesulfonate) (pTS‐D). The first simulation is based on a modification of Baughman's model, a classical model for simulating the polymerization of diacetylene crystals. The agreement between the simulated and experimental results concerning the reaction kinetics is satisfactory. With this simulation algorithm, we take into account the experimental observation that the polymerization of pTS‐H and pTS‐D crystals is really a random process of formation of polymer chains along the crystallographic axis b . The second simulation is based on the Monte Carlo method, which permits not only to simulate the kinetics of the reaction, but also the chain‐length distribution in the hydrogenated and deuterated compounds. These two types of simulations were already developed for the hydrogenated crystal of diacetylene, named pTS‐H. Two main modifications are applied in the case of pTS‐D for taking into account experimental results: in the first the rate constants of chain‐terminating microscopic processes are different in pTS‐H and pTS‐D which must be considered. The second modification concerns the evolution of the lattice deformation during the course of polymerization. The experimental variation of the b parameter as a function of polymer content X in pTS‐D is different from that in pTS‐H; this result is important to consider when calculating the activation energy of the initiation and propagation microscopic processes.     

Synthesis and characterization of a novel polyurethane/polypyrrole‐p‐toluenesulfonate (PU/PPy‐pTS) electroactive nanofibrous bending actuator

Electroactive actuators based on conductive polymers currently have attracted a great deal of attention. In this study, a nanofibrous structure of polypyrrole (PPy) was used to fabricate an electroactive bending actuator. For this purpose, polyurethane/PPy (PU/PPy) nanofibrous bending actuator was fabricated through the combined use of electrospinning and in‐situ chemical polymerization. The response surface methodology (RSM) was considered to find the optimal electrospinning conditions for producing PU nanofibers with the minimum diameter. The in‐situ chemical polymerization method was then used to prepare a conductive layer of PPy on the surface of optimum electrospun nanofibers with p‐toluenesulfonate (pTS) as the dopant. The coated nanofibers were used in the fabrication of PU/PPy‐pTS nanofibrous bending actuator. The morphology and electrical, thermal, electrochemical, and electrochemomechanical properties of the fabricated actuator were investigated. By using optimum conditions of electrospinning, PU nanofibers were obtained with a diameter of 221 nm. The results showed that the produced PU/PPy‐pTS nanofibers enjoy good thermal stability and have an electrical conductivity of about 276.34 S/cm. The obtained cyclic voltammetric and dynamo‐voltammetric responses showed that the dominant mechanism of actuation in the fabricated PU/PPy‐pTS nanofibrous actuator is the exchange of perchlorate anions with a partial exchange of lithium cations in 1M lithium perchlorate electrolyte solution. The fabricated actuator was capable of undergoing 141° reversible angular displacement during a potential cycle. The results demonstrated that, given high porosity, large specific surface area, flexibility, and desirable electrical properties, PU/PPy nanofibrous electroactive actuator provides a lot of potential for developing artificial muscle applications.     

p‐Quaterphenylene as an Aggregation‐Induced Emission Fluorogen in Supramolecular Organogels and Fluorescent Sensors

Two dumbbell‐shaped organogelators with a p ‐quaterphenylene core were synthesized, and their self‐assembly properties were investigated. These low‐molecular‐weight gelators could form self‐supporting gels in many apolar organic solvents with an H‐type aggregation form through a synergic effect of π–π stacking, intermolecular translation‐related hydrogen bonding, and van der Waals forces. In comparison to the p ‐terphenylene‐cored gelator, the extended π‐conjugated segment improved the gelation efficiency significantly with enhanced gelation rate. Additionally, these p ‐quaterphenylene‐centered gelators exhibited strong fluorescence emission induced by aggregation, which not only provided an in situ method to optically monitor the gelation process, but also endowed these self‐assemblies with substantial applications in sensing explosives.     

p‐Chloro‐, p‐bromo‐ and two polymorphs of p‐iodo­aceto­phenone

The title p‐haloaceto­phenones, C₈H₇XO (X = Cl, Br and I), have different packing modes. The chloro compound contains H⋯O and H⋯Cl contacts, but no Cl⋯O contacts. The bromo compound and one polymorph (A) of the iodo compound are isomorphous, with significant X⋯O contacts [Br⋯O = 3.320 (4) Å and I⋯O = 3.374 (5) Å]. In the other polymorph (B) of the iodo compound, the I⋯O distance is 3.082 (4) Å. Both polymorphs contain C—H⋯π contacts; these contacts are shorter in A than in B.     

Autoresolution of Segregated and Mixed p‐n Stacks by Stereoselective Supramolecular Polymerization in Solution

A “chirality driven self‐sorting” strategy is introduced for the controlled supramolecular organization of donor (D) and acceptor (A) molecules in multicomponent assemblies. The trans‐1,2‐bis(amido)cyclohexane (trans‐BAC) has been identified as a supramolecular motif with strong homochiral recognition to direct this chirality controlled assembly process of enantiomers in solution. Stereoselective supramolecular polymerization of trans‐BAC appended naphthalene diimide monomers (NDIs) has been probed in detail by spectroscopic and mechanistic investigations. This chirality‐driven self‐sorting design of enantiomeric components also offers to realize mixed and segregated D‐A stacks by supramolecular co‐assembly of the NDI acceptors with trans‐BAC appended dialkoxynaphthalene (DAN) donor monomers. Such an unprecedented chirality control on D‐A organization paves the way for the creation of supramolecular p‐n nanostructures with controlled molecular‐level organization.     

Multiple‐Stimuli Responsive and Tunable Luminescent Supramolecular Assembly by Oligo(p‐phenylvinylene) and Surfactant

Achieving multicolor photoluminescence under multiple stimuli response based on a single fluorescent compound remains a great challenge. Herein, we report a novel multicolor fluorescent supramolecular assembly, which was constructed from surfactant sodium dodecyl sulfate (SLS) and fluorescent compound 1 bearing a rigid symmetrical acceptor–donor–acceptor structure. The luminescence property of 1 /SLS assembly showed the multiple stimuli response towards temperature, cyclodextrin complexation and UV light irradiation, exhibiting the tunable emission wavelengths from 490 nm to 590 nm and the multicolor photoluminescence including cyan, green, yellow and orange. Furthermore, this assembly could be used in light writing owing to the fast fluorescence change within 15 s. These results could provide a convenient and useful method for fabricating smart tunable photoluminescent materials.     

Chain Architecture Dependent 3‐Dimensional Supramolecular Assembly of Rod‐Coil Molecules with a Conjugated Hexa‐p‐phenylene Rod

Summary: We have prepared hexa‐p‐phenylene based rod‐coil molecules with identical coil volume fractions, but different poly(propylene oxide) (PPO) coil architectures (linear versus dibranched), and investigated their self‐assembling behavior in the solid state by small angle X‐ray scattering (SAXS) and transmission electron microscopy (TEM) techniques. Rod‐coil molecules with a linear PPO coil showed a honeycomb‐like lamellar assembly of rod segments with hexagonally arrayed PPO coil perforations. In contrast, the rod‐coil molecules with dibranched PPO coils self‐organized into rod bundles with a body centered tetragonal symmetry surrounded by a PPO coil matrix. These results demonstrate that the steric hindrance at the rod/coil interface arising from coil architectural variation is a dominant parameter governing supramolecular rod assembly in the rod‐coil system.

TEM images and schematic illustrations of the self‐assembled structures of rod‐coil molecules with linear (left) and dibranched (right) PPO coils, respectively.     

A Supramolecular Vesicle Based on the Complexation of p‐Sulfonatocalixarene with Protamine and its Trypsin‐Triggered Controllable‐Release Properties

Enzyme‐responsive assembly represents one of the increasingly significant topics in biomaterials research and finds feasible applications to the controlled release of therapeutic agents at specific sites at which the target enzymes are located. In this work, based on the concept of host–guest chemistry, a trypsin‐responsive supramolecular vesicle using p‐sulfonatocalix[4]arene as the macrocyclic host and natural serine protease trypsin‐cleavable cationic protein protamine as the guest molecule, is reported. The complexation of p‐sulfonatocalix[4]arene with protamine directs the formation of a supramolecular binary vesicle, which is dissipated by trypsin with high selectivity. Therefore, the present system represents a principle‐of‐concept to build a controlled‐release carrier at trypsin‐overexpressed sites.     

Dual Self‐Assembling Polycondensation of p‐Acetoxybenzoic Acid and p‐Acetamidobenzoic Acid

The dual self‐assembling polycondensation of p‐acetoxybenzoic acid (ABA) and p‐acetamidobenzoic acid in Therm S 800 was examined at 300 °C. Needle‐like crystals and lath‐like crystals were formed simultaneously through reaction‐induced crystallization of oligomers at a molar ratio of 30–50 mol‐% ABA in the feed. The needle‐like crystals comprised more p‐oxybenzoyl units, whereas the lath‐like ones contained higher amounts of p‐benzamide moieties.

     

p‐Nitro­phenyl isocyanide

Achiral p‐nitro­phenyl isocyanide, C₇H₄N₂O₂, crystallizes in the orthorhombic chiral space group P2₁2₁2₁. Attractive intermolecular interactions between the nitro O atoms and both aromatic H and nitro N atoms of neighbouring mol­ecules are observed. The O⋯N interaction is surprisingly strong [N⋯O = 2.869 (2) Å] compared with other aromatic nitro compounds.     

Morphology of poly(p‐oxybenzoyl) crystal prepared by direct polycondensation of p‐hydroxybenzoic acid with p‐toluenesulfonyl chloride in pyridine

Poly(p‐oxybenzoyl) (POB) crystals were prepared with the reaction‐induced crystallization of oligomers during the direct polycondensation of p‐hydroxybenzoic acid (HBA) with p‐toluenesulfonyl chloride (TsCl) and N,N‐dimethylformamide in pyridine. Sheaflike lozenge‐shaped POB crystals were obtained, of which the longer diagonal was 7.0–8.0 μm. The influence of the polymerization condition on the morphology was examined to optimize the preparative condition for the crystals exhibiting the clearest habit, and the favorable condition was determined as the molar ratio of TsCl to HBA of 1.3 and polymerization concentration of 3.0%. The crystals possessed extremely high crystallinity and outstanding thermal stability. The formation mechanism of the crystal was proposed as follows. When the number‐average degree of polymerization of the oligomers exceeded a critical value of about 4, they were precipitated to form the hexagonal lamellae. The crystals were grown very quickly to lozenge‐shaped crystal through screw dislocation with the continuous precipitation of oligomers from the solution. Finally, the further polymerization occurred in the precipitated crystal with developing polymer‐chain packing. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3275–3282, 2003     

Relativistic and Non‐Relativistic Electronic Molecular‐Structure Calculations for Dimers of 4p‐, 5p‐, and 6p‐Block Elements

We report results of non‐relativistic and two‐component relativistic single‐reference coupled‐cluster with single and double and perturbative triple excitations [CCSD(T)] treatments for the 4p‐block dimers Ga₂ to Br₂, the 5p‐block dimers In₂ to I₂, and their atoms. Extended basis sets up to pentuple zeta are employed and energies extrapolated to the complete basis‐set limit. Relativistic and non‐relativistic results for the dissociation energy D_e are in close agreement with each other and previously published data, provided non‐relativistic or scalar‐relativistic results are corrected for spin–orbit contributions taken from the literature. An exception is Te₂ where theoretical results scatter by 0.085 eV. By virtue of this agreement it is unexpected that comparison with the experimental D₀ or D_e dissociation energies (zero‐point vibrational effects are negligible in this context) reveal errors larger than 0.1 eV for Ga₂, Ge₂, and Sb₂. Only relativistic treatments are presented for the 6p‐block cases Tl₂ to At₂. Sufficient agreement with experimental data is found only for Pb₂ and Bi₂, the deviation of the computed and experimental D₀ values for Po₂ is again larger than 0.1 eV. Deviations of 0.1 eV between the computed and experimental D₀ values are a major reason for concern and call for additional investigations in both fields to clarify the situation.     

Supramolecular hydrogen‐bonding patterns in salts of the antifolate drugs trimethoprim and pyrimethamine

Nine salts of the antifolate drugs trimethoprim and pyrimethamine, namely, trimethoprimium [or 2,4‐diamino‐5‐(3,4,5‐trimethoxybenzyl)pyrimidin‐1‐ium] 2,5‐dichlorothiophene‐3‐carboxylate monohydrate (TMPDCTPC, 1:1), C₁₄H₁₉N₄O₃⁺·C₅HCl₂O₂S⁻, ( I ), trimethoprimium 3‐bromothiophene‐2‐carboxylate monohydrate, (TMPBTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₅H₂BrO₂S⁻·H₂O, ( II ), trimethoprimium 3‐chlorothiophene‐2‐carboxylate monohydrate (TMPCTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₅H₂ClO₂S⁻·H₂O, ( III ), trimethoprimium 5‐methylthiophene‐2‐carboxylate monohydrate (TMPMTPC, 1:1:1), C₁₄H₁₉N₄O₃⁺·C₆H₅O₂S⁻·H₂O, ( IV ), trimethoprimium anthracene‐9‐carboxylate sesquihydrate (TMPAC, 2:2:3), C₁₄H₁₉N₄O₃⁺·C₁₅H₉O₂⁻·1.5H₂O, ( V ), pyrimethaminium [or 2,4‐diamino‐5‐(4‐chlorophenyl)‐6‐ethylpyrimidin‐1‐ium] 2,5‐dichlorothiophene‐3‐carboxylate (PMNDCTPC, 1:1), C₁₂H₁₄ClN₄⁺·C₅HCl₂O₂S⁻, ( VI ), pyrimethaminium 5‐bromothiophene‐2‐carboxylate (PMNBTPC, 1:1), C₁₂H₁₄ClN₄⁺·C₅H₂BrO₂S⁻, ( VII ), pyrimethaminium anthracene‐9‐carboxylate ethanol monosolvate monohydrate (PMNAC, 1:1:1:1), C₁₂H₁₄ClN₄⁺·C₁₅H₉O₂⁻·C₂H₅OH·H₂O, ( VIII ), and bis(pyrimethaminium) naphthalene‐1,5‐disulfonate (PMNNSA, 2:1), 2C₁₂H₁₄ClN₄⁺·C₁₀H₆O₆S₂²⁻, ( IX ), have been prepared and characterized by single‐crystal X‐ray diffraction. In all the crystal structures, the pyrimidine N1 atom is protonated. In salts ( I )–( III ) and ( VI )–( IX ), the 2‐aminopyrimidinium cation interacts with the corresponding anion via a pair of N—H…O hydrogen bonds, generating the robust R₂²(8) supramolecular heterosynthon. In salt ( IV ), instead of forming the R₂²(8) heterosynthon, the carboxylate group bridges two pyrimidinium cations via N—H…O hydrogen bonds. In salt ( V ), one of the carboxylate O atoms bridges the N1—H group and a 2‐amino H atom of the pyrimidinium cation to form a smaller R₂¹(6) ring instead of the R₂²(8) ring. In salt ( IX ), the sulfonate O atoms mimic the role of carboxylate O atoms in forming an R₂²(8) ring motif. In salts ( II )–( IX ), the pyrimidinium cation forms base pairs via a pair of N—H…N hydrogen bonds, generating a ring motif [R₂²(8) homosynthon]. Compounds ( II ) and ( III ) are isomorphous. The quadruple DDAA (D = hydrogen‐bond donor and A = hydrogen‐bond acceptor) array is observed in ( I ). In salts ( II )–( IV ) and ( VI )–( IX ), quadruple DADA arrays are present. In salts ( VI ) and ( VII ), both DADA and DDAA arrays co‐exist. The crystal structures are further stabilized by π–π stacking interactions [in ( I ), ( V ) and ( VII )–( IX )], C—H…π interactions [in ( IV )–( V ) and ( VII )–( IX )], C—Br…π interactions [in ( II )] and C—Cl…π interactions [in ( I ), ( III ) and ( VI )]. Cl…O and Cl…Cl halogen‐bond interactions are present in ( I ) and ( VI ), with distances and angles of 3.0020 (18) and 3.5159 (16) Å, and 165.56 (10) and 154.81 (11)°, respectively.     

1,3,5‐Tri‐p‐tolyl­biuret

MoOCl₂(L_OMe) as catalyst, where L_OMe is CpCo[P(O)(OMe)₂]₃, reacts with p‐tolyl isocyanate to afford the title compound, C₂₃H₂₃N₃O₂. The structural features are the intramolecular hydrogen bond forming a six‐membered ring and a nearly planar arrangement of the biuret moiety. Each p‐tolyl phenyl ring is twisted by approximately 60–80° with respect to the others. The bond lengths N1—C22 of 1.357 (3) Å and N2—C23 of 1.333 (3) Å indicate that they are partial double bonds.     

Heterogeneous polycondensation for composition control of poly(p‐mercaptobenzoyl‐co‐p‐benzamide) by shearing

Composition control of aromatic poly(thioester‐amide) was examined by the reaction‐induced phase separation during polymerization of S‐acetyl‐4‐mercaptobenzoic acid (AMBA) and p‐acetylaminobenzoic acid (AABA) in aromatic solvent. The poly(thioester‐amide)s were obtained as precipitates and their yields became lower at the middle range of the content of AMBA in feed (χ_f). The contents of p‐mercaptobenzoyl (MB) moiety (χ_p) in the precipitates prepared without shearing were in good agreement with the χ_f values. In contrast to this, the χ_p values of the precipitates prepared at χ_f of 50–70 mol % under shearing were much lower than the χ_f values. The reaction rate of AMBA increased with shearing, whereas that of AABA was unchanged by shearing. This shearing effect on the reaction rates accelerated to form the homo‐oligomers. The solubility of MB oligomers enhanced by shearing, whereas that of p‐benzamide oligomers did not enhance owing to the strong interaction through hydrogen bonding. The MB oligomers were inhibited to be precipitated, resulting in the lower χ_p values than the χ_f values. The composition could be controlled by the application of the shearing to the heterogeneous polymerization. © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 4301–4308