Synthesis, crystal structure and spectroscopic properties of an unsymmetrical compound with carbazole and benzothiadiazole units

An unsymmetrical organic compound with carbazole (Cz) as donor and benzothiadiazole (BTD) as acceptor (D-π-A-π∗-D∗) was designed and synthesized via simple Heck reaction. The unique crystal structure of Cz-BTD-Cz∗ shows a ladder-like packing mode. A two molecule pair stacks parallelly with each other in each packing unit. In each cell, one Cz moiety is connected with BTD by vinylene bond in same plane. However, the other Cz group is connected to BTD by a one-end vinyl bond in almost perpendicular position to the coplanar part of the molecule. The shortest intermolecular plane distance is 3.48 ± 0.1 Å. The photophysical properties of Cz-BTD-Cz∗ in solution and in bulky crystalline powder state were studied. In bulk crystalline powder state, it has a red-shifted emission band peaked at 609 nm relative to that in solution, and the FWHM was reduced to only 58 nm. Electrochemical properties were also investigated.     

Charge compensation dynamics in a soluble copolymer of poly(aniline) and poly(phenylene sulfide)

Poly(phenylene sulfide phenyleneamine), PPSA, is a copolymer of poly(aniline) and poly(phenylene sulfide), soluble in conventional organic solvents as tetrahydrofuran, dimethyl sulfoxide, dimethylformamide, and cyclohexanone. In this research, its electrochemical behavior has been studied in acetonitrile in the presence of different electrolytes, where the loss of electroactivity was observed after few cycles. In this paper, the charge compensation dynamics of PPSA is analyzed through electrochemical quartz crystal microbalance experiments and electroacoustic impedance measurements. Raman spectroscopy data have shown that once the oxidation of the sulfur atom occurs, a loss of electroactivity is observed, being not possible to recover the pristine state of the polymer. Fourier transform infrared (FTIR) and X-ray diffraction (XRD) data obtained for the fully oxidized polymer are consistent with the formation of a networked polymer due to the electrophilic attack of the positive sulfur atom on the activated aromatic rings. Electrochemical quartz crystal microbalance results clearly show that the degree of irreversibility fully depends on the chemical nature of the anions with a negligible participation of the cations of the electrolytic solution. This work is in memoriam of Prof. Dr. Francisco C. Nart, dearest friend and colleague, whose scientific skills and enthusiasm will always be remembered.     

Electrostatics of phosphatidic acid monolayers: Insights from computer simulations

In this paper, we argue that many of the fascinating electrostatic effects that take place in amphiphilic systems are strongly related to the particular organization of the oxygen atoms within each individual molecule. In particular, we focus on two effects: charge inversion and dielectric overscreening. For that purpose, we present molecular dynamics simulations of phosphatidic acid (DMPA²⁻) in the presence of divalent counterions. Our results show that the many oxygens present in DMPA²⁻ cooperatively create strong binding sites for counterions, which in some cases lead to charge inversion. We also present an analysis of the role of interfacial water and relate our analysis to the phenomenon of dielectric overscreening. Several experimental implications are discussed in the conclusions.     

磺化酞菁铜分子膜／SiO2／Si界面电荷转移机制的研究

在具有不同氧化层厚度的p型硅基片上修饰2层磺化酞菁铜分子膜.利用时间分辨表面光电压谱技术,对该膜系的界面电荷转移机制的光电开关特性进行了研究。结果表明,用时间分辨表面光电压谱技术研究界面电荷转移过程具有明显优越性.     

Photoinduced electron transfer across linearly fused oligo-norbornyl structures

The rates of photoinduced electron transfer (ET) reactions across two oligo-norbornyl spacer groups (S), that is, structure 1 fused by two norbornadiene (NBD) units and structure 2 fused by three NBD units, are examined. Substituted naphthalene acted as an electron donor (D), whilst ethylene-1,2-dicarboxylate as an electron acceptor (A). ET rates were measured by fluorescence quenching experiments on these D-S-A dyads, and the results were correlated with reaction free energies according to the Marcus relationship. It was found that naphthalene with phenyl substituents showed relatively slower ET rates. The conformational flexibility of phenyl substituents may cause a hindrance on the electronic coupling between D and A. Another salient feature was the abnormally high quenching rates observed in nonpolar solvents such as cyclohexane, the results of which may be ascribed to a competing energy transfer process.     

Geometries and properties of bimetallic phosphido-bridged complex Cp(CO)2W(μ-PPh2)W(CO)5 and Cp(CO)3W(μ-PPh2)W(CO)5

Complete geometry optimizations were carried out by HF and DFT methods to study the molecular structure of binuclear transition-metal compounds (Cp(CO)₃W(μ-PPh₂)W(CO)₅) (I) and (Cp(CO)₂W(μ-PPh₂)W(CO)₅) (II). A comparison of the experimental data and calculated structural parameters demonstrates that the most accurate geometry parameters are predicted by the MPW1PW91/LANL2DZ among the three DFT methods. Topological properties of molecular charge distributions were analyzed with the theory of atoms in molecules. (3, −1) critical points, namely bond critical point, were found between the two tungsten atoms, and between W1 and C10 in complex II, which confirms the existence of the metal–metal bond and a semi-bridging CO between the two tungsten atoms. The result provided a theoretical guidance of detailed study on the binuclear phosphido-bridged complex containing transition metal–metal bond, which could be useful in the further study of the heterobimetallic phosphido-bridged complexes.     

Elucidating Factors Manipulated the Formation of Multiply Charged Protein Homomultimeric Complexes by Electrospray Ionization

Native non‐covalently bonded protein‐protein and protein‐substrate complexes are of great interest and have been extensively studied by electrospray ionization mass spectrometry (ESI‐MS). Multiply charged protein homomultimeric complexes are shown to form by ESI‐MS. This study addresses factors that can artificially induce the formation of multiply charged protein homomultimeric complexes. Cytochrome c (Cyt c) and ubiquitin, which are monomers in solution, were found to generate (Cyt c)_mⁿ⁺ by electrospray ionization (ESI). The homomultimeric complexes were not limited to dimeric complexes but include also multiply charged trimers, tetramers, and pentamers. The observation of these homomultimeric complexes has never been revealed from a Cyt c solution at the concentration as low as 10 μM. Increasing the concentration of Cyt c enhanced the formation of (Cyt c)_mⁿ⁺ as expected; however, the protein concentration does not affect the relative intensities of monomeric and dimeric complexes. Additionally the enrichment of NH₄OH also promotes the formation of (Cyt c)_mⁿ⁺. Notably, source collision‐induced dissociations (source‐CID) of (Cyt c)_mⁿ⁺ alter the charge state distribution (CSD) and may lead to an incorrect interpretation of Cyt c conformations. Hence, extra care should be taken when using CSD to interpret the conformation of a protein derived from ESI‐MS.     

Laser field induced charge transfer: Para-nitroaniline coupled to a quantum mechanical radiation field

Summary We present a preliminary model for describing a solvated intramolecular charge transfer reaction coupled to a quantum mechanical radiation field. Actual calculations of energies and couplings were performed with a recently developed self-consistent reaction field response method. The representation of dressed molecular states is used for calculating state populations for various laser fields. The state populations are sensitive to the properties of the laser field.     

碘掺杂的3-乙基-5-[2-(3-乙基-2苯并噻唑啉基)亚乙基]罗丹宁的结构与电性能

The merocyanine dye 3-ethyl-5-(2-(3-ethyl-2-benzothiazolinylidene)-ethylidene)-rhodanine (BTER) known as Agfa-10 has been found to have a good photoconductivity as solution cast film. In this paper iodine-doped BTER was obtained by doping with iodine vapor. Its structure was investigated with the following characteristies. 1 The doped iodine had been excited as I_3~- anion. 2 Because the electron located on the sulphur atom was transferred to iodine, the charge transfer complex of (BTER-I_3) formed. 3 During the iodine doping process, BTER changed from α-form to β-modification. These had been identified by X-ray diffraction, VIS-absorption spectra and SEM picture.4 From the volt-Ampere curve obtained from sandwich cell, when E≤2.2×10~(-1) V·cm~(-1), the room temperature electrical conductivity of BTER and BTER-I_3 were found to be 2.22×10~(-10) s·cm~(-1) and 2.6×10~(-7) S·cm~(-1), respectively.     

Does ionized diacetylene have a positive proton affinity?

Singly and doubly charged C₄H₃^+/2+ ions generated upon electron ionization (EI) of the neutral precursors 1,3-butadiene, benzene, and exo-methylene cyclopropane, respectively, are examined by sector-field mass-spectrometry. Charge stripping of the mass-selected monocations affords the corresponding dications and charge exchange of the C₄H₃²⁺ dications allows for the reverse redox process. Refined analysis and additional MS/MS studies suggest that the monocations are mixtures of isomeric ions formed upon ionization, whereas only a single type of dication seems to be formed. As an average of energy-resolved measurements, a vertical ionization energy of IE_v(C₄H₃⁺)=16.5±0.4 eV is derived. In addition to the experimental work, density functional theory is used for a computational exploration of the mono- and dicationic species. The best theoretical estimates are IE_a(C₄H₃⁺)=16.33 eV and IE_v(C₄H₃⁺)=16.49 eV for the most stable isomer H₂C=C---CCH⁺. Combination of the experimental and theoretical findings leads to the conclusion that the diacetylene cation C₄H₂⁺ has indeed a positive proton affinity of PA(C₄H₂⁺)=1.50±0.42 eV.