A Novel Proton Sensor with Luminescence and Color Signaling Based on Platinum(II) Terpyridyl Acetylide Complex

Molecular switches that are controllable, reversible and readable at molecular level are an essential compo-nent of molecular electronics1 and chemical sensors.2-6 Of particular interest are the molecules which show dramatic and reversible changes in color and/or lumi-nescence in visible spectral region upon exposure to specific substrates. A number of chromophore- spacer-receptor systems that can selectively recognize specific guest molecules at their receptor site and pro-duce measurable col…     

Spectroscopic and electrochemical properties of Cu-dicyandiamide complex

Dicyandiamide(DICY) is a common ligand that exhibits low toxicity but can irritate the skin and eyes and cause methemoglobinemia on long-term exposure. Crystalline Cu-dicyandiamide(Cu-DICY) was obtained via facile synthesis and its molecular structure and theoretical Raman spectra were simulated by using density functional theory(DFT). The results suggested that the Cu~(2+) coordinates with two H_2 O molecules and two different DICY molecules(an imino DICY and an amino DICY). The stability constants of Cu-DICY were calculated, and the electrochemical properties were studied. Two electrochemical redox processes occur in Cu-DICY in an aqueous solution: a reversible reaction with a formal potential of 0.2 V vs.MSE and an irreversible reaction between –0.4 and –1.2 V vs. MSE. The standard rate constant k0 for the reversible reaction was estimated to be 7.6×10~(-3) cm/s. In addition, based on the reversible reaction of Cu-DICY, square wave voltammetry was used to rapidly determine the concentration of Cu(II) and the detection limit was 66.7 μg/L, which satisfies the detection limit requirements for copper in tap water(2 mg/L) as provided by the World Health Organization.     

Macrocyclic versus acyclic preorganization in organoplatinum(II)-based host-guest complexes

Two host-guest systems have been constructed,by employing structurally similar terpyridine platinum (II) macrocycle and molecular tweezer as the synthetic receptors.The macrocycle/guest complex displays low-energy emission signal,reinforced non-covalent binding affinity,and enhanced photosensitization capability than those of the molecular tweezer/guest one.The discrepancy between macrocyclic and acyclic preorganization modes originates from the different numbers of Pt (II)...Pt (II) metal-metal bonds in host-guest complexation structures.     

Synthesis of polystyrene-styrene/butadiene diblock copolymers via reversible addition-fragmentation chain transfer miniemulsion polymerization

<正>Polystyrene-styrene/butadiene diblock copolymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) miniemulsion polymerization.During the polymerization process,the molecular weight distribution was narrow and the numerical molecular weight of the copolymers increased with increasing conversion of monomers,which was close to the theoretical.FT-IR and ~1H NMR results indicated that the microstructure of the polymer was mainly 1,4-trans-butadiene with small amount of 1,2-units,and composition in the copolymers was obtained.     

Reversible light-driven magnetic switching of salen cobalt complex

Spin-crossover(SCO) metal complexes are expected to be widely used in data storage materials, display devices and sensors.Although a lot of spin-crossover photoswitches have been developed, the reversible photomodulation cases that work at room temperature are limited. Herein, a novel cobalt complex o-1-Co(II) wherein the salen unit bridges with bis-diarylethene has been designed as switch to construct "off-on" logic operation at room temperature. The complex o-1-Co(II) displays an abrupt,reversible and hysteretic spin crossover(T_(1/2)↓=166 K, T_(1/2)↑=177 K, and ΔT_(1/2)=11 K) between the high-spin(HS) and low-spin(LS) states. Meanwhile, photocyclization of o-1-Co(II) with UV light produces a photoresponsive closed form c-1-Co(II),which always stays at low-spin without SCO at all. Moreover, the magnetic switching of the complex can also be achieved with redox reactions between Co(II) and Co(III).     

Aqueous RAFT polymerization of acrylamide: A convenient method for polyacrylamide with narrow molecular weight distribution

Controlled and homogeneous free-radical polymerization of acrylamide(AM) in aqueous phase was realized by using S,S'-bis(α,α'-dimethyl-α'-acetic acid)-trithiocarbonate as a reversible addition-fragmentation transfer(RAFT) agent. Linear increases in molecular weight with conversion and narrow molecular weight distribution were observed for polyacrylamide(PAM) throughout the polymerization. By this method, PAMs with controlled molecular weight(up to 1.0 × 10~6) and narrow molecular weight distribution(M_w/M_n 1.2) were prepared. This study provides an effective method for synthesis of PAMs with narrow molecular weight distribution under environmentally friendly conditions.     

Studies on Transition Metal Complexes of Schiff Base( Ⅰ )——Oxygen-carrying Properties of Cobalt( Ⅱ )Schiff Base Complexes

Introduction The compounds that can take up and release molecular oxygen reversibly is of significance because they can be used as model compounds for the study of the reversible oxygenation mechanisms involved in the very complex natural oxygen carriers, e.g., the hemoglobins and hemocyanins, and as the means of separating molecular oxygen from the air. The dioxygen carriers extensively studied are the Cobalt     

Fluorescence Switch Based on a Porphyrin-perylene Dyad

Upon excitation of porphyrin or perylene subunit, the porphyrin-perylene dyad exhibits reversible fluorescence emitting and quenching by formation and neutralization of the protonated porphyrin subunit, thereby providing a prototype of molecular fluorescence switch working in an expanded spectral range.     

External stimulation-controlled dynamic DNA devices for biosensing and biomedical applications

DNA devices that can recognize molecular inputs and transform them into functional outputs in an autonomous manner have been actively pursued as versatile toolkits for controlled nanofabrication, molecular network regulation, biosensing and cellular function modulation. The introduction of external stimuli-responsive units not only ensures the programmability and functionality of DNA devices themselves, but also confers rapid, remote and reversible dynamic regulation capabilities. This facilitat...     

Redox-responsive diphenylalanine aggregate mediated by cyclodextrin

The molecular assembling behaviours between ferrocene-modified diphenylalanine and β-cyclodextrin were investigated, which showed a reversible morphological conversion by the chemical redox of ferrocenyl moiety.     

Loading single lanthanide ion into aluminum molecular rings:water-stable sodalite cage for removal of nuclear-industry anions

Based on our discovery of neutral aluminum molecular rings, we herein introduce rare earth ions into the center of the ring and reveal their structural adaptability. The resulting yoyo-like cationic macrocycles are highly adaptive to guests, creating unusual supramolecular assemblies. The first category is stacked with singly oriented rhombohedral channels, which exhibit fast and reversible solvent-triggered molecular motions and structural rearrangements. The second type of assembly is that yoy...     

Effect of dextran molecular weight on resonance light-scattering of quantum dots modified with dextran and concanavalin A

The reversible aggregation between dextran-conjugated CdSe quantum dots(Dex-CdSe-QDs) and concanavalin A(Con A) was explored based on the specific affinity of polysaccharide for Con A by resonance light-scattering technique.In this study,the aggregation of Dex-CdSe-QDs induced by Con A and sequential dissociation by glucose was determined over a wide range of dextran molecular mass(10-500 kDa).The results demonstrate that the sensitivity of lectin-dextran-modified-QDs interactions increase with dextran molecular mass,and an optimum dextran molecular mass is 500 kDa.     

Synthesis and Crystal Structure of a Coordination Polymer {[Co(phth)(phen)(H_2O)]·(C_2H_5OH)}_n

1 INTRODUCTION Metal-organic coordination polymer has particu- lar and special structure characters with some caves, holes and channels[1], and can be used in selected catalysis, molecular recognition, reversible exchan- ge of host-guest molecules (ions), super purity sepa- ration, biological conductor[2～5], etc. In the past ten years, polymers with bridging ligand have been widely investigated[6, 7]. The development of supra- molecular architectures of inorganic-organic hybrid molecules …     

Formation Mechanism and Stability Study of Konjac Glucomannan Helical Structure

The formation mechanism and stability of konjac glucomannan (KGM) helical structure were investigated by molecular dynamic simulation and experimental method. The results indicate that the molecular conformation of KGM is a non-typical helical structure. In detail, helical structure of KGM is mainly sustained by acetyl group, whose size and stability are affected by the molecular polymerization degree of KGM. In vacuum among the non-bonding interactions, electrostatic force is the greatest factor affecting its helical structure, but in water solution, hydrogen bond affects the helical arrangement greatly. To our interest, temperature exhibits a reversible destroying effect to some extent; the helical structure will disappear completely and present a ruleless clew-like arrangement till 341 K. This work suggests that the method of combining molecular dynamic simulation and experiment tools can be effective in the study of KGM helical structure.     

An acid-base responsive linear-cyclic polymer rotaxane molecular shuttle with fluorescence signal output

The preparation of intelligent-responsive materials with controllable topology structure has long been a significant objective for chemists in the field of materials science. In this paper, we designed and prepared a linear-cyclic reversible topological structure polymer based on the bistable [1]rotaxane molecular shuttle. A ferrocene-functionalized [1]rotaxane and naphthalimide fluorophore group are introduced into the both ends of the polymer, which exhibit distance-induced photo-electron tran...     

Light-Triggered Molecular Level Self-Healing Spiropyran Thin Film

Spiropyran thin film with capability of light-triggered molecular level sell-healing has been successtully aesigned and fabricated by Langmuir-Blodgett technology. Various remarkable properties of thin film shrinkage or height increase or self-healing nano-defect recovery under different fabrication conditions have been observed. In addition, further evidence of the self-healing, which resulted from the movement of spiropyran molecules （such as ＂standing＂ ＂lie-down＂ and ＂tip-toes＂ etc.） on the substrate, has also been observed from the reversible contact angle change of the thin film.     

Wet-spinning of Regenerated Silk Fiber fromAqueous Silk Fibroin Solutions: Influence ofCalcium Ion Addition in Spinning Dope on thePerformance of Regenerated Silk Fiber简

Ca（II） ions are added in the spinning dope to adjust the solidification rate of regenerated silk fibroin （RSF） solution during the wet-spinning process since Ca（II） ions are proved to be favorable to maintain the stable silk fibroin network in our previous work. The results show that when Ca（II）/RSF ratios are 1/50 and 1/20, the resulted RSF fibers exhibit good performance with the breaking energy more than 70 kJ/kg. However, higher Ca（II）/RSF ratio （for example, 1/10） hinders the solidification of spinning dope and results in poor RSF fibers. These observations together with earlier papers from this laboratory confirm that to produce tough silk fibers the spinning conditions must allow sufficient time for the adjustment of silk fibroin molecular chains.     

Off-on-off Luminescent Switching of a Novel Ru(II) Complex

There has been explosive interest in the synthesis and applications of novel Ru(II) polypyridyl complexes with respect to molecular sensors1,2, switches3, and sensitizers of Gr鋞zel solar cells based on nanocrystalline TiO24. Here we report a novel Ru(II) complex, which can serve as pH-induced remarkable off-on-off luminescent switch. Scheme 1 The acid-base equilibria of the complex UV-vis absorption and emission spectroscopic pH titration experiments of the Ru complex wit…     

Rational design of FLP catalysts for reversible H2 activation: A DFT study of the geometric and electronic effects

The thermodynamics of reversible H₂ activation could be controlled by adjusting substituents of LA group and using different polar solvents, which forges a guide to design potential FLPs catalysts for reversible H₂ activation.