A Theoretical Investigation of Surface‐enhanced Sum‐frequency Generation

Following the surface enhanced Raman scattering (SERS), we shall investigate the possibility of observing surface‐enhanced sum‐frequency generation (SESFG), which refers to the transformation of ordinary vibrational SFG (i.e. singly resonant) into SESFG. Two mechanisms of SESFG will be studied; one is due to the transformation of singly‐resonant vibrational SFG into doubly resonant vibrational SFG (that is, both vibrationally resonant and Raman‐scattering resonant) and the other is due to the enhancement of the polarizability in addition to the original vibrational resonance in vibrational SFG.     

Reactions of a Ruthenium Complex with Substituted N‐Propargyl Pyrroles

In an investigation into the chemical reactions of N‐propargyl pyrroles 1 a – c , containing aldehyde, keto, and ester groups on the pyrrole ring, with [Ru]?Cl ([Ru]=Cp(PPh₃)₂Ru; Cp=C₅H₅), an aldehyde group in the pyrrole ring is found to play a crucial role in stimulating the cyclization reaction. The reaction of 1 a , containing an aldehyde group, with [Ru]?Cl in the presence of NH₄PF₆ yields the vinylidene complex 2 a , which further reacts with allyl amine to give the carbene complex 6 a with a pyrrolizine group. However, if 1 a is first reacted with allyl amine to yield the iminenyne 8 a , then the reaction of 8 a with [Ru]?Cl in the presence of NH₄PF₆ yields the ruthenium complex 9 a , containing a cationic pyrrolopyrazinium group, which has been fully characterized by XRD analysis. These results can be adequately explained by coordination of the triple bond of the propargyl group to the ruthenium metal center first, followed by two processes, that is, formation of a vinylidene intermediate or direct nucleophilic attack. Additionally, the deprotonation of 2 a by R₄NOH yields the neutral acetylide complex 3 a . In the presence of NH₄PF₆, the attempted alkylation of 3 a resulted in the formation the Fischer‐type amino–carbene complex 5 a as a result of the presence of NH₃, which served as a nucleophile. With KPF₆, the alkylation of 3 a with ethyl and benzyl bromoacetates afforded the disubstituted vinylidene complexes 10 a and 11 a , containing ester groups, which underwent deprotonation reactions to give the furyl complexes 12 a and 13 a , respectively. For 13 a , containing an O‐benzyl group, subsequent 1,3‐migration of the benzyl group was observed to yield product 14 a with a lactone unit. Similar reactivity was not observed for the corresponding N‐propargyl pyrroles 1 b and 1 c , which contained keto and ester groups, respectively, on the pyrrole ring.     

Extended metal-atom chains with an inert second row transition metal: [Ru5(mu5-tpda)4X2] (tpda2- = tripyridyldiamido dianion, X = Cl and NCS)

EMACs (extended metal-atom chains) offer a unique platform for the exploration of metal-metal interactions. There has been significant advances on the synthesis of EMACs, such as lengthening the chains up to 11 metal atoms thus far, integrating naphthyridine moieties for tuning the charge carried at metal centers, and manipulation of metal-metal interactions. However, the metal centers in EMACs hitherto are limited to first row transition metals which are more labile than those relatively inert ones with electrons filled in the 4d and 5d shells. In this Communication, the synthesis, crystallographic, magnetic, and electrical conducting studies of [Ru5(mu5-tpda)4Cl2] and [Ru5(mu5-tpda)4(NCS)2], the first pentanuclear EMACs of second-row transition metal, are reported.     

Quantum Mechanical Calculations for Biomass Valorization over Metal-Organic Frameworks (MOFs)

Metal-organic framework (MOF) in biomass valorization is a promising technology developed in recent decades. By tailoring both the metal nodes and organic ligands, MOFs exhibit multiple functionalities, which not only extend their applicability in biomass conversion but also increase the complexity of material designs. To address this issue, quantum mechanical simulations have been used to provide mechanistic insights into the catalysis of biomass-derived molecules, which could potentially facilitate the development of novel MOF-based materials for biomass valorization. The aim of this review is to survey recent quantum mechanical simulations on biomass reactions occurring in MOF catalysts, with the emphasis on the studies of the catalytic activity of active sites and the effects of organic ligand and porous structures on the kinetics. Moreover, different model systems and computational methods used for MOF simulations are also surveyed and discussed in this review.     

Biocompatible bacteria@Au composites for application in the photothermal destruction of cancer cells

We have successfully transformed the infectious E. coli bacteria into biocompatible bacteria@Au composites for photothermal therapy.     

Calculating molecular vibrational spectra beyond the harmonic approximation

We present a new approach for calculating anharmonic corrections to vibrational frequency calculations. The vibrational wavefunction is modelled using translated Hermite functions thus allowing anharmonic effects to be incorporated directly into the wavefunction whilst still retaining the simplicity of the Hermite basis. We combine this new method with an optimised finite-difference grid for computing the necessary third and fourth nuclear derivatives of the energy. We compare our combined approach to existing anharmonic models—vibrational self-consistent field theory (VSCF), vibrational perturbation theory (VPT), and vibrational configuration interaction theory (VCI)—and find that it is more cost effective than these alternatives. This makes our method well-suited to computing anharmonic corrections for frequencies in medium-sized molecules. Contribution of the Mark S. Gordon 65th Birthday Festschrift Issue.     

Novel organosoluble aromatic polyimides bearing pendant methoxy‐substituted triphenylamine moieties: Synthesis,electrochromic, and gas separation properties

Four series of polyimides I – VI with pendent triphenylamine (TPA) units having inherent viscosities of 0.44–0.88 dL/g were prepared from four diamines with two commercially available tetracarboxylic dianhydrides via a conventional two‐step procedure that included a ring‐opening polyaddition to give polyamic acids, followed by chemical cyclodehydration. These polymers were amorphous and could afford flexible films. All the polyimides had useful levels of thermal stability associated with high softening temperatures (279–300 °C), 10% weight‐loss temperatures in excess of 505 °C, and char yields at 800 °C in nitrogen higher than 58%. The hole‐transporting and electrochromic properties were examined by electrochemical and spectroelectrochemical methods. Cyclic voltammograms of the polyimide films cast onto an indium‐tin oxide (ITO)‐coated glass substrate exhibited a or two reversible oxidation couples at 0.65–0.78 and 1.00–1.08 V versus Ag/AgCl in acetonitrile solution. The polymer films revealed electrochromic characteristics with a color change from neutral pale yellowish to blue doped form at applied potentials ranging from 0.00 to 1.20 V. The CO₂ permeability coefficients (P) and permeability selectivity (P/P) for these polyimide membranes were in the range of 4.73–16.82 barrer and 9.49–51.13, respectively. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 7937–7949, 2008     

A new photothermal therapeutic agent: core-free nanostructured Au x Ag1-x dendrites

A new class of Au(x)Ag(1-x) nanostructures with dendrite morphology and a hollow interior were synthesized by using a replacement reaction between Ag dendrites and an aqueous solution of HAuCl(4). The Ag nanostructured dendrites were generated by the reaction of AgNO(3) with ascorbic acid in a methanol/water system. The dendrites resemble a coral shape and are built up of many stems with an asymmetric arrangement. Each stem is approximately 400 nm in length and 65 nm in diameter. The bimetallic composition of Au(x)Ag(1-x) can be tuned by the addition of different amounts of HAuCl(4) to the Ag dendritic solution. The hollowing process resulted in tubular structures with a wall thickness of 10.5 nm in Au(0.3)Ag(0.7) dendrites. The UV/Vis spectra indicate that the strongest NIR absorption among the resulting hollow Au(x)Ag(1-x) dendrites was in Au(0.3)Ag(0.7). The MTT assay was conducted to evaluate the cytotoxicity of Ag dendrites, hollow Au(0.06)Ag(0.94) and Au(0.3)Ag(0.7) dendrites, and Au nanorods. It was found that hollow Au(0.06)Ag(0.94) and Au(0.3)Ag(0.7) dendrites exhibited good biocompatibility, while both Ag dendrites and Au nanorods showed dose-dependent toxicity. Because of absorption in the NIR region, hollow Au(0.3)Ag(0.7) dendrites were used as photothermal absorbers for destroying A549 lung cancer cells. Their photothermal performance was compared to that of Au nanorod photothermal therapeutic agents. As a result, the particle concentration and laser power required for efficient cancer cell damage were significantly reduced for hollow Au(0.3)Ag(0.7) dendrites relative to those used for Au nanorods. The hollow Au(0.3)Ag(0.7) nanostructured dendrites show potential in photothermolysis for killing cancer cells.     

Quantification of SMN1 and SMN2 genes by capillary electrophoresis for diagnosis of spinal muscular atrophy

We present the first CE method for the separation and quantification of SMN1 and SMN2 genes. Spinal muscular atrophy (SMA) is an inherited neuromuscular disorder deleted or mutated in SMN1 gene and retained at least one copy of SMN2 gene. However, these two genes are highly homologous, differentiation and quantification of SMN1 and SMN2 are therefore required in diagnosis to identify SMA patients and carriers. We developed a fluorescence-labeled conformation-sensitive CE method to quantitatively analyze PCR products covering the variable position in the SMN1/SMN2 genes using a copolymer solution composed of hydroxyethylcellulose and hydroxypropylcellulose. The DNA samples included 24 SMA patients, 52 parents of SMA patients (obligatory carriers), and 255 controls. Those 331 samples were blind analyzed to evaluate the method, and the results compared with those obtained using denaturing HPLC (DHPLC). Validation of accuracy was performed by comparing the results with those of DHPLC. Nine of total samples showed different results. Diagnosis of one fetus DNA among them was related to abortion or not, which was further confirmed by gel electrophoresis and DNA sequencing. Our method showed good coincidence with them, and proved the misdiagnosis of DHPLC. This simple and reliable CE method is a powerful tool for clinical genotyping of large populations to detect carriers and SMA patients.