An achiral oligo(p-phenylene vinylene) derivative with a ureido-triazine hydrogen bonding unit self-assembles into rows of hydrogen bonded dimers at the liquid/solid interface. Scanning tunneling microscopy reveals the formation of chiral domains, but overall, the surface remains racemic. Addition of a chiral auxiliary which is able to interact with the dimers through hydrogen bonding, showed that global organizational chirality could be achieved since a majority of the domains show the same handedness. After removing the chiral auxiliary with a volatile solvent, the global organizational chirality could be trapped, revealing a memory effect. With this straightforward supramolecular approach, we were able to create a chiral surface with preferred handedness composed of achiral molecules at the air/solid interface.

The formation of DNA nucleoside-assisted π-conjugated nanostructures was studied by means of scanning tunneling microscopy (STM) and force field simulations. Upon adsorption of the achiral oligo(p-phenylenevinylene) (OPV) derivative at the liquid/solid interface, racemic conglomerates with mirror related rosettes are formed. Addition of the DNA nucleosides D- and L-thymidine, which act as "chiral handles", has a major effect on the supramolecular structure and the expression of chirality of the achiral OPV molecules. The influence of these "chiral handles" on the expression of chirality is probed at two levels: monolayer symmetry and monolayer orientation with respect to the substrate. This was further explored by tuning the molar ratio of the building blocks. Molecular modeling simulations give an atomistic insight into the monolayer construction, as well as the energetics governing the assembly. Thymidine is able to direct the chirality and the pattern of OPV molecules on the surface, creating chiral lamellae of π-conjugated dimers.

A series of novel cis poly(phenylacetylene)s (PPAs) substituted at the meta-position(s) by both achiral alkoxycarbonyl and chiral alkylamide groups, i.e., rP-I, sP-I to sP-V, or by just a chiral alkylamide group, i.e., rP-VI, were synthesized under catalysis of [Rh(nbd)Cl] 2 . The dependence of the elongation, screw sense, and stimuli response of helical polyene backbone on the structure and number of substituent was systematically investigated in both solution and solid states. Stretched cis−transoid helices with opposite signs coexisted in the DMF solution of either sP-I or rP-I, but a single handed, contracted cis−cisoid one formed in the mixture of DMF/THF (10/90, v/v). Increasing the substituent size made the polymers sP-III, sP-IV, and sP-V to take only single handed stretched cis−transoid helical conformations regardless of the solvent polarity. The N-methylation of the amide group in sP-II caused a similar effect. With the removal of achiral methoxycarbonyl substituent, rP-VI took just a stretched cis−transoid helical conformation in polar DMF, whereas it existed as a mixture in equilibrium of stretched cis−transoid and contracted cis−cisoid helices with identical screw sense in less polar solvents such as dioxane, THF, and chloroform. The twisting directions of substituent array and polyene backbone were found to be coincident in a dynamic, contracted helix, but the opposite in a less dynamic, stretched helix. These results suggested that the 3,5-disubstitution, strong intramolecular hydrogen bonding, and small substituent favored the formation of contracted cis−cisoid helices for PPAs. ■ INTRODUCTIONHelix is the central structural motif in biomacromolecules such as genes and proteins, which plays vital roles in their fundamental and sophisticated biological activities. 1−5 Motivated by Nature, chemists have designed and prepared various synthetic polymers with helical main chains [e.g., poly-(isocyanide)s, 6−10 poly(isocyanate)s, 11−13 polyacetylenes, 14−18 poly(silane)s, 19,20 poly(methyl methacrylate)s, 21,22 polystyrenes, 23−26 polyguanidines, 27−29 and foldmers, 30,31 etc.]. Unlike nonhelical polymers, the materials based on helical polymers exhibit unique superiority in multichannel sensors, 32−34 enantioselective separation, 35−39 asymmetric catalysis, 40−44 among others. 45−49 Regulating the conformations of helical polymers at will would not only deepen our understanding of living systems 50 but also promote the development of novel materials. 5 As a result, control over the helical sense (lefthanded/right-handed) and the elongation (contracted/ stretched) has received ever-increasing attention in the last few decades. 51−53 Poly(phenylacetylene)s (PPAs) are a typical type dynamic helical polymers. 54−56 A PPA molecule possesses at least four possible conformers: cis−transoid, cis−cisoid, trans−cisoid, and trans−transoid. With rhodium diene complexes as the polymerization catalysts, PPAs with cis−transoid or cis−cisoid structures can be obtained. The former is a stretched structure, while the ...

Porous organic polymers (POPs) have been considered as prominent adsorbents for volatile iodine. So far, both crystalline and amorphous POPs have accomplished excellent iodine capture capability. Considering the difficulty and challenges in preparing perfect crystalline POPs, more explorations into developing versatile amorphous POPs are needed. Herein, amorphous POPs based on the Schiff-base reaction were designed and synthesized for volatile iodine removal. Four amorphous POPs products named as NDB-H, NDB-S, ADB-HS, and ADB-S obtained under different solvothermal conditions were investigated in terms of their morphologies, porosity, and their iodine enrichment performance in detail. It is noteworthy that excellent efficiency for removing iodine vapor was acquired for NDB-S (≈425 wt %), ADB-HS (≈345 wt %), and ADB-S (≈342 wt %). Remarkably, NDB-H exhibited an iodine capture capacity up to ≈443 wt %. Excellent reusability was obtained as well. Amorphous NDB-H has accomplished an extremely high iodine capture performance, illustrating the great chance to exploit versatile amorphous POPs for iodine enrichment and removal based on Schiff-base chemistry.

An enhancement near threshold is observed in the omega(phi) invariant mass spectrum from the doubly Okubo-Zweig-Iizuka-suppressed decays of J/psi-->gamma(omega)phi, based on a sample of 5.8 x 10(7) J/psi events collected with the BESII detector. A partial wave analysis shows that this enhancement favors JP=0+, and its mass and width are M=1812(+19)(-26)(stat)+/-18(syst) MeV/c2 and Gamma=105+/-20(stat)+/-28(syst) MeV/c2. The product branching fraction is determined to be B(J/psi-->gammaX)B(X-->omega(phi))=[2.61+/-0.27(stat)+/-0.65(syst)]x10(-4).