Quantal phases, disorder effects, and superconductivity in spin-Peierls systems

In view of recent developments in the investigation on cuprate high- T(c) superconductors and the spin-Peierls compound CuGeO3, we study the effect of dilute impurity doping on the spin-Peierls state in quasi-one-dimensional systems. We identify a common origin for the emergence of antiferromagnetic order upon the introduction of static vacancies and superconductivity for mobile holes.     

Threshold temperature of thermal entanglement in an XXZ ferromagnetic chain

Pairwise thermal entanglement of an XXZ ferromagnetic chain with a uniform magnetic field is investigated by using the entanglement measure of negativity. The effects of spin, number of sites, anisotropic parameter, and magnetic field on the threshold temperature are discussed respectively.     

One color resonant two photon ionization spectroscopy of p-methylstyrene and theoretical calculation

The band origin of the S1<--S0 transition of p-methylstyrene is determined to be 34,276 cm-1 by one color resonant two photon ionization (1C-R2PI) method, which is red shifted by 3811 cm-1 with respect to that of benzene. This indicates that the interaction of the methyl and vinyl groups with the ring in the S1 state is greater than that in the S0 state. The active vibrations assigned from the R2PI spectrum are found to be the in-plane ring modes. The bands at 399, 613, 724, and 786 cm-1 are assigned to the vibrations 9b, 6b, 12, and 1, respectively, and discussed in detail. The experimental results are well supported by ab initio and density functional theory (DFT) calculations.     

Ten new antifouling briarane diterpenoids from the South China Sea gorgonian Junceella juncea

Ten new antifouling briarane diterpenoids, juncins R-ZI (1-10) were isolated from the South China Sea gorgonian coral Junceella juncea. The structures of these new compounds were established by extensive spectroscopic analysis, including 1D and 2D NMR data. Compounds 1-10 all showed potent antifouling activities against the larval settlement of barnacle Balanus amphitrite at nontoxic concentrations with EC₅₀ values of 0.004, 0.34, 2.65, 1.61, 3.77, 21.06, 0.004, 0.14, 1.47, and 0.51 μg mL⁻¹. The structure-activity relationship was discussed.     

Surface modification of self-assembled one-dimensional organic structures: white-light emission and beyond

Surface modification is an important method to functionalize micro-/nanostructures, but substrates are mainly confined to robust inorganic compounds. We develop here a facile method to modify the surface of a fragile organic 1D microstructure. The bulk molecules and surface modifier were designed with orthogonal solubility to protect the molecular crystals from destruction under the reaction conditions. As a proof of concept, white-light-emitting 1D microstructures were obtained by grafting red chromophores onto the surface of self-assembled blue-emissive microwires via a heterophase S(N)2 reaction. Spatial distribution of the two species is visualized by fluorescent lifetime mapping, which reveals a core-shell structure. The ability to postfunctionalize organic 1D structures enables many applications, where the surface property plays key roles, such as an organic P-N junction and a biosensor.     

Study of tetrabutylammonium perfluorooctanoate aqueous solutions with two cloud points by dielectric relaxation spectroscopy

Dielectric relaxation spectra of tetrabutylammonium perfluorooctanoate (TBPFO), an anionic fluorocarbon surfactant with two cloud points in aqueous solution, were investigated in the frequency range from 40 Hz to 110 MHz. Striking dielectric relaxations were observed when both the temperature-dependent and concentration-dependent phase transitions in TBPFO aqueous solution occurred. The changes in dielectric relaxation and the distribution of dielectric parameters were consistent with the phase boundaries of the phase diagram. In the first homogeneous phase region, two relaxations of rodlike micelles appeared at about 100 kHz and 5 MHz, which originated from the diffusion of the free counterions in the directions of the long axis and the short axis of rodlike micelles, respectively. With increasing temperature, two relaxations gradually turned to one as a result of the formation of connected or entanglement points between the wormlike micelles. The lengths of the long half-axis and the short half-axis of the rodlike micelles, as well as the average distance of the connected or entanglement points of the wormlike micelles, were evaluated by the obtained relaxation times.     

An Efficient synthesis of pyrimido[4,5‐b]quinoline and indeno[2′,1′:5,6]pyrido[2,3‐d]pyrimidine derivatives via multicomponent reactions in ionic liquid

A series of pyrimido[4,5‐b]quinoline and indeno[2′,1′:5,6]pyrido[2,3‐d]pyrimidine derivatives were synthesized via the three‐component reaction of an aldehyde, 6‐aminopyrimidine‐2,4‐dione and 5,5‐dimethyl‐1,3‐cyclohexanedione or 1,3‐indanedione in ionic liquid 1‐n‐butyl‐3‐methylimidazolium bromide ([bmim]Br). This protocol has the advantages of easier work‐up, milder reaction conditions, high yields and an environmentally benign procedure compared with other methods.     

A computational study of chlorocarbene additions to cyclooctyne

Dichloro- and phenylchlorocarbene (CCl2 and PhCCl) add to cyclooctyne via a barrierless process (MP2/6-311+G*, B3LYP/6-311+G*, B3LYP/6-31G*) to yield the expected corresponding cyclopropene adducts. A three-dimensional potential energy surface (PES) for CCl2 addition to cyclooctyne (B3LYP/6-31G*) shows the formation of the cyclopropene product and also possible formation of a vinylcarbene. Residing in a shallow energy well, the vinylcarbene easily rearranges to the cyclopropene product, or to an exocyclic vinyl bicyclo[3.3.0]octane. Although the calculated three-dimensional PES indicates possible dynamic control of the cyclooctyne-chlorocarbene system through the putative formation of a vinylcarbene (in addition to the expected cyclopropene), additional calculations and preliminary experimental work show paths through the vinylcarbene to be unlikely. If the additions of chlorocarbenes to cyclooctyne are controlled by reaction dynamics, we predict that the vast majority of the reactions proceed via traditional carbene cycloaddition with only a very minor amount of products formed from the alternative pathway.     

Synthesis and reactions of the first fluoroalkylated Ni(II) N-confused porphyrins

The first fluoroalkylated Ni(ii) N-confused porphyrins were synthesized with high regioselectivity and its further alkylation was studied.     

Different EDC/NHS activation mechanisms between PAA and PMAA brushes and the following amidation reactions

Infrared spectroscopy was applied to investigate the well-known EDC/NHS (N-ethyl-N'-(3-(dimethylamino)propyl)carbodiimide/N-hydroxysuccinimide) activation details of poly(acrylic acid) (PAA) and poly(methacrylic acid) (PMAA) brushes grafted on porous silicon. Succinimidyl ester (NHS-ester) is generally believed to be the dominant intermediate product, conveniently used to immobilize biomolecules containing free primary amino groups via amide linkage. To our surprise, the infrared spectral details revealed that the EDC/NHS activation of PMAA generated anhydride (estimated at around 76% yield and 70% composition), but not NHS-ester (around 5% yield and 11% composition) under the well-documented reaction conditions, as the predominant intermediate product. In contrast, EDC/NHS activation of PAA still follows the general rule, i.e., the expected NHS-ester is the dominant intermediate product (around 45% yield and 57% composition), anhydride the side product (40% yield and 28% composition), under the optimum reaction conditions. The following amidation on PAA-based NHS-esters with a model amine-containing compound, L-leucine methyl ester, generated approximately 70% amides and 30% carboxylates. In contrast, amidation of PAA- or PMAA-based anhydrides with L-leucine methyl ester only produced less than 30% amides but more than 70% carboxylates. The above reaction yields and percentage compositions were estimated by fitting the carbonyl stretching region with 5 possible species, NHS-ester, anhydride, N-acylurea, unreacted acid, unhydrolyzed tert-butyl ester, and using the Beer-Lambert law. The different surface chemistry mechanisms will bring significant effects on the performance of surface chemistry-derived devices such as biochips, biosensors, and biomaterials.