Syntheses, Crystal Structures and Properties of Two New W-Ag 1D Chain Complexes: [W_2Ag_2S_8·Ca(DMF)_6]_n and [WAgS_4·Na(DMF)_3]_n

Two new complexes, [W2Ag2S8?Ca(DMF)6]n 1 and [WAgS4?Na(DMF)3]n 2, have been synthesized and characterized. Single-crystal X-ray analyses show both 1 and 2 have {WAgS4}n anion linear chains, but 1 has a discrete [Ca(DMF)6]2+ cation while 2 is a linear chain. UV-Visible-Near-IR spectroscopy data show that the bandgaps of the two complexes are 1.86 and 1.99 eV, respectively. Electrical conductivity measurements reveal the conductivities of 1 and 2 are 10?7 and 10?8 Scm?1, respectively and they exhibit thermally activated temperature depen- dence, which may be attributed to semiconductors.

Structure influence of alkyl chains of thienothiophene-porphyrins on the performance of organic solar cells

Two new A-D-A porphyrin derivatives,denoted as XLP-I and XLP-II,were prepared through extending theπ-conjugation of thienothiophene-porphyrin center with phenylethynyl bridges and electron-deficient ethylrhodanine terminal units,and varying the structures of alkyl chain(linear vs branched)on peripheral thienothiophene substitutions of porphyrin rings.Both molecules show strong absorption in UV–visible–near-infrared region,good thermal stability,suitable energy levels,and ordered molecular packing in solid state.In organic solar cells,PC71BM was used as electron acceptor,and porphyrin small molecules were used as electron donors.The device based on XLP-I exhibits a power conversion efficiency(PCE)of 8.30%,an open circuit voltage(Voc)of 0.894 eV,and a fill factor(FF)of 62.1%.In contrast,the device based on XLP-II presents an inferior performance with a PCE of 3.14%,a Voc of 0.847 eV,and a FF of 49.3%.The better performance of XLP-I based device is mainly attributed to its optimized film morphology,excellent absorption,and well-balanced charge transport properties.

Raman spectroscopy of isolated carbyne chains confined in carbon nanotubes:Progress and prospects

Carbyne is an infinitely long linear chain of carbon atoms with sp1hybridization and the truly one-dimensional allotrope of carbon.While obtaining freestanding carbyne is still an open challenge,the study of confined carbyne,linear chains of carbon encapsulated in carbon nanotubes,provides a pathway to explore carbyne and its remarkable properties in a well-defined environment.In this review,we discuss the basics and recent advances in studying single confined carbyne chains by Raman spectroscopy,which is their primary spectroscopic characterization method.We highlight where single carbyne chain studies are needed to advance our understanding of confined carbyne as a material system and provide an overview of the open questions that need to be addressed and of those aspects currently under debate.

A review of arc-discharge method towards large-scale preparation of long linear carbon chains

Linear carbon chains as new one-dimensional(1D)nanomaterials attract attention for the predicted outstanding properties.However,the high reactivity of linear carbon chains hampers further experimental research.To date,different methods have been developed to synthesize new materials containing linear carbon chains.Among them,the arc-discharge method is a practical way to prepare both finite and infinite linear carbon chains.This review provides a brief discussion of the recent progress in the techniques to prepare carbon chain-based materials and then focuses on the arc-discharge method.The configuration of apparatus,optimal conditions,and the corresponding mechanism of arc-discharge method to prepare long linear carbon chain inside multi-walled carbon nanotubes are summarized in detail.The characterization techniques are introduced to evaluate the quality of products.Moreover,remaining challenges and perspectives are presented for further investigation of long linear carbon chains.

Novel Poly m eric Transition Metal Co m plexes Having1D Chain and 3D Networks Structures

The syntheses and structures of eleven novel polymeric transition metal complexes having one dimensional chain structures or three dimensional networks are summarized. They are prepared from the controlled assembling reactions in organic solvents and characterized by X ray diffraction analyses. The spectroscopic or magnetic properties of some complexes are studied.

Heat Transport in Double-Bond Linear Chains of Fullerenes

Heat transport in one kind of double-bond linear chains of fullerenes （C60＇s） is investigated by the classical nonequilibrium molecular dynamics method. It is found that the negative differential thermal resistance （NDTR） is more likely to occur at larger temperature difference and shorter length. In addition, with the increase of the length, the thermal conductivity of the chains increases, and NDTR region shrinks and vanishes in the end. The temperature profiles reveal that a large temperature jump exists at a high-temperature boundary of the chains when NDTR occurs. These results may be helpful for designing thermal devices where low-dimensional C60 polymers can be used.

Mean-square exponential stability for stochastic time-varying delay systems with Markovian jumping parameters:a delay decomposition approach

The mean-square exponential stability problem is investigated for a class of stochastic time-varying delay systems with Markovian jumping parameters. By decomposing the delay interval into multiple equidistant subintervals, a new delay-dependent and decay-rate-dependent criterion is presented based on constructing a novel Lyapunov functional and employing stochastic analysis technique. Besides, the decay rate has no conventional constraint and can be selected according to different practical conditions. Finally, two numerical examples are provided to show that the obtained result has less conservatism than some existing ones in the literature.

One-dimensional sp carbon:Synthesis,properties,and modifications

Carbyne,as the truly one-dimensional carbon allotrope with sp-hybridization,has attracted significant interest in recent years,showing potential applications in next-generation molecular devices due to its ultimate one-atom thinness.Various excellent properties of carbyne have been predicted,however,free-standing carbyne sample is extremely unstable and the corresponding experimental researches and modifications are under-developed compared to other known carbon allotropes.The synthesis of carbyne has been slowly developed for the past decades.Recently,there have been several breakthroughs in in-situ synthesis and measurement of carbyne related materials,as well as the preparation of ultra-long carbon chains toward infinite carbyne.These progresses have aroused widespread discussion in the academic community.In this review,the latest approaches in the synthesis of sp carbon are summarized.We then discuss its extraordinary properties,including mechanical,electronic,magnetic,and optical properties,especially focusing on the regulations of these properties.Finally,we provide a perspective on the development of carbyne.

Electron—rich Polynuclear Transition Metal Clusters：Ⅱ.Synthetic and S

The syntheses and structures of a novel series of polynuclear coinage metal cluster compounds are discussed. The most fascinating structural characteristic of the Au-Ag alloy clusters with Au_18Ag_19 and Au_18Ag_19 cores and phosphine ligands, which were prepared by the reduction of mononuclear coinage metal complexes R3PAuX and R3PAgX with NaBH4 in organic solution, is their construction from 13-atom gold-centred icosahedral Au_7Ag_6 building blocks. The structures of the polynuclear coinage metal clusters with R2dtc ligands are variable with either unlimited linear chain or triangular M3 units.

Synthesis, Crystal Structure and Anti-lung Cancer Activity of a New Dy(Ⅱ) Complex

A new Dy-based coordination polymer, namely {[Dy（cptpy）_2（H_2O）_2]（TPT）（Cl）}_n（1, Hcptpy = 4-（4-carboxyphenyl）-4,2？：6？,4？？-terpyridine, TPT = 2,4,6-tri（4-pyridyl）-1,3,5-triazine, DMA = N,N-dimethylacetamide） has been solvothermally synthesized by the reactions of DyCl_3, Hcptpy and TPT in a mixture solvent of DMA and H_2O. Single-crystal X-ray structural analysis reveals that 1 is a 1D linear chain coordination polymer with quadrangle channels which are occupied by the TPT ligands. The compound has been characterized by singe-crystal analyses, thermogravimetry analyses and powder X-ray diffraction measurements. The antitumor activity of compound 1 and its corresponding organic ligands Hcptpy and TPT were then investigated against four human lung cancer cell lines（NCI-H460, Calu-3, A549 and NCI-H292） by MTT assay. It was found that compared with Hcptpy and TPT, compound 1 exerted rather potent activity against all of these cell lines.

A review of linear carbon chains

Linear carbon chains(LCCs)are a one-dimensional sp1-hybridized allo trope of ca rbon.LCCs are extre mely unstable:The longer the LCCs,the less stable the materials.Thus,it is a big challenge to synthesize long LCCs.Although the research on the short LCCs,e.g.,polyynes,can be traced back to the 18th,LCCs are still not well-known compared to other allotropes of carbon,e.g.,fullerenes,carbon nanotubes and graphene.Therefore,introducing recent progress on LCCs is of great significance to draw more attention in the community of nanocarbons as well as nanomaterials in general.Theoretically,various excellent properties have been predicted.Experimentally,LCCs with different length in many kinds of forms have been successfully synthesized.In this review,we summarized recent studies of polyynic LCCs from both theoretical and experimental aspects.Also,perspectives are highlighted to point out the further investigations of the materials.

SIMPLE COMPUTING OF THE CUSTOMER LIFETIME VALUE:A FIXED LOCAL-OPTIMAL POLICY APPROACH

In this paper,we present a new method for finding a fixed local-optimal policy for computing the customer lifetime value.The method is developed for a class of ergodic controllable finite Markov chains.We propose an approach based on a non-converging state-value function that fluctuates（increases and decreases） between states of the dynamic process.We prove that it is possible to represent that function in a recursive format using a one-step-ahead fixed-optimal policy.Then,we provide an analytical formula for the numerical realization of the fixed local-optimal strategy.We also present a second approach based on linear programming,to solve the same problem,that implement the c-variable method for making the problem computationally tractable.At the end,we show that these two approaches are related：after a finite number of iterations our proposed approach converges to same result as the linear programming method.We also present a non-traditional approach for ergodicity verification.The validity of the proposed methods is successfully demonstrated theoretically and,by simulated credit-card marketing experiments computing the customer lifetime value for both an optimization and a game theory approach.