Coupled-cluster singles and doubles for extended systems

Coupled-cluster theory with connected single and double excitation operators (CCSD) and related approximations, such as linearized CCSD, quadratic configuration interaction with single and double excitation operators, coupled-cluster with connected double excitation operator (CCD), linearized CCD, approximate CCD, and second- and third-order many-body perturbation theories, are formulated and implemented for infinitely extended one-dimensional systems (polymers), on the basis of the periodic boundary conditions and distance-based screening of integrals, density matrix elements, and excitation amplitudes. The variation of correlation energies with the truncation radii of short- and long-range lattice sums and with the number of wave vector sampling points in the first Brillouin zone is examined for polyethylene, polyacetylene, and polyyne, and is shown to be a function of the degree of pi-electron conjugation or the fundamental band gaps. The t2 and t1 amplitudes in the atomic orbital (AO) basis are obtained by first computing the t amplitudes in the Bloch-orbital basis and subsequently back-transforming them into the AO basis. The plot of these AO-based t amplitudes as a function of unit cells also indicates that the t2 amplitudes of polyacetylene and polyyne exhibit appreciably slower decay than those of polyethylene, although the asymptotic decay behavior is invariably 1/r3. The AO-based t1 amplitudes appear to correlate strongly with the electronic structure, and they decay seemingly exponentially for polyethylene whereas they stay at a constant magnitude across the seventh nearest neighbors of polyacetylene and polyyne, which attests to far reaching effects of nondynamical electron correlation mediated by orbital rotation. Nonetheless, the unit cell contributions to the correlation energies taper below 10(-6) hartree after 15 A for all three polymers. The basis set dependence of the decay behavior of t2 amplitudes is also examined for linear hydrogen fluoride polymer (HF)infinity and linear beryllium polymer (Be)infinity employing the STO-3G, 6-31G, and 6-31G* basis sets, and proves to be rather small.     

Syntheses and properties of donor-acceptor-type 2,5-diarylthiophene and 2,5-diarylthiazole

[structure: see text] Syntheses of differently substituted 2,5-diarylthiophenes and 2,5-diarylthiazoles are carried out with the palladium-catalyzed C-H substitution reaction using AgF as an activator. Remarkably strong photoluminescence is observed in 2,5-diarylthiophene. Differences between the physical properties of liquid crystalline characteristics and cyclic voltammograms of thiophene and thiazole are also studied.     

Chemical effects on beryllium K X-ray spectra produced by heavy ion bombardment

Beryllium X-ray spectra from Be and BeO targets by proton, helium, nitrogen and argon ion bombardment have been measured. In the oxide, chemical shifts of K_α and K²_α X-ray lines are similar magnitude and the intense satellite KL and hypersatellite K²L lines are observed by heavy ion bombardment.     

Synthesis and properties of 1,4,8,11,15,18,22,25-octaalkoxy-2,3,9,10,16,17,23,24-octakis(phenylthio)phthalocyaninato copper(II)

1,4,8,11,15,18,22,25-Octaalkoxy-2,3,9,10,16,17,23,24-octakis(phenylthio)phthalocyaninato copper(II) was synthesized. They were easily soluble in organic solvents and their Q-bands showed bathochromic shifts about 100 nm compared with unsubstituted phthalocyaninato copper(II). Their properties were examined.     

Rhodium-catalyzed anti-Markovnikov hydroamination of vinylarenes

The transition metal-catalyzed anti-Markovnikov hydroamination of unactivated vinylarenes with a rhodium complex of DPEphos is reported. The reaction of electron-neutral or electron-rich vinylarenes with a variety of secondary amines in the presence of catalyst forms the products from anti-Markovnikov hydroamination in high yields. Reactions of morpholine, N-phenylpiperazine, N-Boc-piperazine, piperidine, 2,5-dimethylmorpholine, and perhydroisoquinoline reacted with styrene to form the amine product in 51-71% yield. Reactions of a variety of vinylarenes with morpholine generated amine as the major product. Reactions of morpholine with electron-poor vinylarenes gave lower amine:enamine ratios than reactions of electron-rich vinylarenes at the same concentration of vinylarene, but conditions were developed with lower concentrations of electron-poor vinylarene to maintain formation of the amine as the major product. Reactions of dimethylamine with vinylarenes were fast and formed amine as the major product. Mechanistic studies on the hydroamination process showed that the amine:enamine ratio was lower for reactions conducted with higher concentrations of vinylarene and that one vinylarene influences the selectivity for reaction of another. A mechanism proceeding through a metallacyclic intermediate that opens in the presence of a second vinylarene accounts for these and other mechanistic observations.     

Copper L X-ray spectra measured by a high resolution ion-induced X-ray spectrometer

High resolution L X-ray emission spectra of Cu have been measured by 0.75 MeV/u H, He, and F, 0.73 MeV/u Ar, 0.64 MeV/u Si, and 0.073 MeV/u Si ion impacts with a crystal spectrometer. The X-ray transition energies in the Cu target for Lι, Lη, L_1,2, Lβ₁, and Lβ_3,4 diagram lines induced by H ion impact are determined, which are in good agreement with those given in the reference by Bearden (Rev. Mod. Phys. 39, 78, 1967). The X-ray spectra produced by F, Si, and Ar ions have complicated structures due to multiple L and M shell vacancy production. The L_1,2 and Lβ₁ emission spectra for H and He ions are compared with the calculated ones based on the multiconfiguration Dirac-Fock method. The origin of the broadening of the L_1,2 line to the lower energy for H ion impact is attributed to one 2p plus one 3d electron vacancy production.     

Catalytic conjugate addition of heterocyclic compounds to α,β-unsaturated carbonyl compounds by hafnium salts and scandium salts

The hafnium chloride (HfCl₄) and scandium chloride (ScCl₃) catalyzed conjugate additions of heterocyclic compounds, such as indoles, pyrrole, pyrazole, and imidazole, have been demonstrated. Hafnium chloride effectively catalyzed the conjugate addition of indoles to α,β-unsaturated carbonyl compounds, and the addition product was obtained in high yield. The reaction of pyrrole was also catalyzed by HfCl₄ or ScCl₃, and produced 2,6-dialkylated pyrroles up to 99% yields. Furthermore, the conjugate addition of the 1-position of the pyrazoles and imidazole occurred, and produced several substituted heterocyclic compounds in good yields.     

Pyrimidines. 65. Synthesis of 6-substituted thieno[2,3-d]pyrimidine-2,4(1H,3H)-diones

Several 6-substituted thieno[2,3-d]pyrimidine-2,4(1H,3H)-dione derivatives were synthesized. 6-Ethoxycarbonyl derivatives 3 and 7 were prepared by treatment of 6-chloro-5-formyluracil 1 and 6-chloro-5-cyanouracil 6 with ethyl 2-mercaptoacetate in the presence of a base. Electrophilic substitution reactions (Vilsmeier-Haack reaction, bromination, and nitration) of 5,6-unsubstituted thieno[2,3-d]pyrimidine 9 , prepared by condensation of 6-mercaptouracil 8 with chloroacetaldehyde, afforded the corresponding 6-formyl-, 6-bromo-, and 6-nitrothieno[2,3-d]pyrimidines 10, 15 and 16 , respectively.     

Ruthenium-catalyzed linear selective allylic aminations of monosubstituted allyl acetates

The ruthenium-catalyzed highly linear selective allylic amination of monosubstituted allylic acetates with secondary amines was developed. The regioselectivity was controlled by the Ru₃(CO)₁₂/2-DPPBA catalyst, and a linear-type aminated product was obtained as a single regioisomer.     

Completely dispersible PEGylated gold nanoparticles under physiological conditions: modification of gold nanoparticles with precisely controlled PEG-b-polyamine

A novel water-soluble, biocompatible polymer, poly(ethylene glycol)-block-poly((2-N,N-dimethylamino)ethyl methacrylate) (PEG-b-PAMA), possessing controlled molecular weight with a narrow molecular weight distribution, was synthesized by the atom-transfer radical polymerization (ATRP) method. PEG-b-PAMA having a short PAMA chain length was successfully synthesized under suitable polymerization conditions. Gold nanoparticles (GNPs) were modified using PEG-b-PAMA prepared under a variety of PEGylation conditions. Under alkaline conditions (pH >10) and an [N]/[GNP] ratio of more than 3300, the PEGylated GNPs (PEG-GNPs) showed complete dispersion stability, avoiding coagulation. The amino groups of the PAMA segment of the block copolymers were completely deprotonated above pH 10. This means that PEG-b-PAMA interacted with the GNP surface via multipoint coordination of the tertiary amino groups of PAMA, not electrostatically. The effect of the number of amino groups in the PAMA segment on GNP surface modifications was investigated by zeta potential and dynamic light scattering (DLS) measurements. When the PEG-GNPs were prepared in excess polymer solution, almost the same diameter was observed regardless of the PAMA chain length. After the PEG-GNPs were purified by centrifugation, the zeta potentials of all PEG-GNPs were shielded to almost 0 mV, indicating the effective modifications of the GNP surface by PEG-b-PAMA regardless of the chain length. However, the particle size and particle size distribution of the purified PEG-GNPs were strongly affected by the PAMA chain length. PEG-GNPs with longer PAMA segments underwent coagulation after purification, whereas PEG-GNPs with shorter PAMA segments increased their dispersion stability. The experimental results of the thermal gravimetric analysis confirmed that the PEG density on the GNP surface increased as the AMA units decreased to 3. Thus, the dispersion stability depended significantly on the PEG density on the GNP surface. GNPs modified with PEG-b-PAMA having short AMA units showed excellent dispersion stability under a variety of pH conditions. The excellent dispersion stability of the obtained PEG-GNP was also confirmed both in bovine serum albumin (BSA) solution and 95% human serum.