Novel oxy-perfluoroalkylation

(Perfluoroalkyl)phenyliodonium sulfonates underwent novel oxy-perfluoroalkylation with alkenes under oxygen atmosphere in the presence of a base.     

Binary clusters AuPt and Au6Pt: structure and reactivity within density functional theory

Within density functional theory with the general gradient approximation for the exchange and correlation, the bimetallic clusters AuPt and Au(6)Pt have been studied for their structure and reactivity. The bond strength of AuPt lies between those of Au(2) and Pt(2), and it is closer to that of Au(2). The Pt atom is the reactive center in both AuPt and AuPt(+) according to electronic structure analysis. AuPt(+) is more stable than AuPt. Au(6)Pt prefers electronic states with low multiplicity. The most stable conformation of Au(6)Pt is a singlet and has quasi-planar hexagonal frame with Pt lying at the hexagonal center. The doping of Pt in Au cluster enhances the chemical regioselectivity of the Au cluster. The Pt atom essentially serves as electron donor and the Au atoms bonded to the Pt atom acts as electron acceptor in Au(6)Pt. The lowest triplet of edge-capped rhombus Au(6)Pt clusters is readily accessible with very small singlet-triplet energy gap (0.32 eV). O(2) prefers to adsorb on Au and CO prefers to adsorb on Pt. O(2) and CO have stronger adsorption on AuPt than they do on Au(6)Pt. CO has a much stronger adsorption on AuPt bimetallic cluster than O(2) does. The adsorption of CO on Pt modifies the geometry of AuPt bimetallic clusters.     

Strong electron correlation effects on first- and second-order hyperpolarizabilities in zwitterionic sigma-conjugated systems: its dependence on substituents, conformations, spacer size, and basis sets

Nonlinear optical properties of zwitterionic sigma-conjugated systems were theoretically investigated with relation to the electron correlation effects at the ab initio molecular orbital level. We examined the strong electron correlation effects on the first- and second-order hyperpolarizabilities in the specific systems with effective "pi-sigma-pi" and (or) "pi-sigma-n" interactions. The electron correlation effects on the hyperpolarizabilities strongly depend on the type of substituents, conformations, spacer size, and basis sets. It was found that the Hartree-Fock level calculations qualitatively predict the behavior of the hyperpolarizabilities after considering the correlation effects. Through-space/-bond interaction analysis quantitatively revealed that the electron correlation effects on the hyperpolarizabilities were induced mainly by the sigma-conjugations on the spacer unit in the zwitterionic sigma-systems.     

Assessment of time-dependent density functional schemes for computing the oscillator strengths of benzene, phenol, aniline, and fluorobenzene

In present study the relevance of using the time-dependent density functional theory (DFT) within the adiabatic approximation for computing oscillator strengths (f) is assessed using different LDA, GGA, and hybrid exchange-correlation (XC) functionals. In particular, we focus on the lowest-energy valence excitations, dominating the UV/visible absorption spectra and originating from benzenelike HOMO(pi)-->LUMO(pi(*)) transitions, of several aromatic molecules: benzene, phenol, aniline, and fluorobenzene. The TDDFT values are compared to both experimental results obtained from gas phase measurements and to results determined using several ab initio schemes: random phase approximation (RPA), configuration interaction single (CIS), and a series of linear response coupled-cluster calculations, CCS, CC2, and CCSD. In particular, the effect of the amount of Hartree-Fock (HF) exchange in the functional is highlighted, whereas a basis set investigation demonstrates the need of including diffuse functions. So, the hybrid XC functionals--and particularly BHandHLYP--provide f values in good agreement with the highly correlated CCSD scheme while these can be strongly underestimated using pure DFT functionals. These results also display systematic behaviors: (i) larger f and squares of the transition dipole moments (mid R:mumid R:(2)) are associated with larger excitation energies (DeltaE); (ii) these relationships present generally a linear character with R>0.9 in least-squares fit procedures; (iii) larger amounts of HF exchange in the XC functional lead to larger f, R:mumid R:(2), as well as DeltaE values; (iv) these increases in f, mid R:mumid R:(2), and DeltaE are related to increased HOMO-LUMO character; and (v) these relationships are, however, not universal since the linear regression parameters (the slopes and the intercepts at the origin) depend on the system under investigation as well as on the nature of the excited state.     

Specific crystal structure of poly(3-hydroxybutyrate) thin films studied by infrared reflection–absorption spectroscopy

Infrared reflection–absorption (IR-RAS) and transmission spectra were measured for poly(3-hydroxybutyrate) (PHB) thin films to explore its specific crystal structure in the surface region. As IR-RAS is sensitive to the vibration mode of perpendicular orientation of the surface, differences between IR-RAS and transmission spectra indicate an orientation of the lamella structure in the surface of PHB thin films. The relative intensity of the crystalline CO stretching band in the IR-RAS spectrum is significantly weaker than that in the transmission spectrum. It may be concluded that the transient dipole moment of the CO stretching mode of the crystalline state is not oriented perpendicular but nearly parallel to the substrate surface. On the other hand, the relative intensity of the band at 3009 cm⁻¹ due to the C–H stretching mode of the C–HOC hydrogen bonding is similar between the IR-RAS and transmission spectra, suggesting that the C–H bond is oriented neither perpendicular nor parallel to the substrate surface but in an intermediate direction. Since the CO group of the C–HOC hydrogen bonding is oriented nearly parallel to the surface and its C–H group is in the intermediate direction, it is very likely that the C–HOC hydrogen bonding has a somewhat bent structure. These results are in good agreement with our previous conclusion that the C–HOC hydrogen bonding of PHB exists along the a-axis (not the b-axis) between the CH₃ group of one helix and the CO group of another helix.     

Chemical and Genetic Study of Ligularia cyathiceps in Yunnan Province of China

Root chemicals and evolutionarily neutral DNA regions in L. cyathiceps samples collected in the Zhongdian (Shangrila) County of Yunnan, P. R. China, were examined. Twenty compounds were isolated, including three new ones, 1β,10β‐epoxy‐6β‐(propionyloxy)furanoeremophilan‐9‐one ( 6 ), 1β,10β‐epoxy‐8α‐ethoxyeremophila‐6,11‐diene ( 14 ), and 11αH‐6β‐isobutyryloxy‐1β,10β,7β,8β‐diepoxyeremophilan‐12,8α‐olide ( 15 ). The chemical diversity was found to be limited, with cacalol ( 1 ) and 6‐(acyloxy)furanoeremophilan‐9‐ones ( 4 and/or 5 ) being major components in all the samples. The nuclear ribosomal RNA gene was also found to harbor little variation, although two distinct sequence types were found for the plastid atpB‐rbcL intergenic region.     

Planar catechin analogues with alkyl side chains: a potent antioxidant and an alpha-glucosidase inhibitor

Planar catechin analogues having various alkyl side chain lengths were synthesized, and their remarkable antioxidative abilities and alpha-glucosidase inhibitory activities are shown.     

Royal crown-shaped electride Li3-N3-Be containing two superatoms: new knowledge on aromaticity

The structure and aromaticity of a royal crown-shaped molecule Li(3)-N(3)-Be are studied at the CCSD(T)/aug-cc-pVDZ level. This molecule is a charge-separated system and can be denoted as Li(3) (2+)N(3) (3-)Be(+). It is found that the Li(3) (2+) ring exhibits aromaticity mainly because the Li(3) (2+) ring can share the pi-electron with the N(3) (-3) ring. The 4n+2 electron counter rule can be satisfied for the Li(3) (2+) subunit if the shared pi valence electron of N(3) (3-) subunit is also taken into account. This new knowledge on aromaticity of a ring from the interactions between subunits is revealed first time in this paper. Li(3)-N(3)-Be can be also regarded as a molecule containing two superatoms (Li(3) and N(3)), which may be named as a "superomolecule." Li(3)-N(3)-Be is a new metal-nonmetal-metal type sandwich complex. The N(3) (3-) trianion in the middle repulses the electron clouds of the two metal subunits (mainly to the Li(3) superatom) to generate an excess electron, and thus Li(3)-N(3)-Be is also an electride. This phenomenon of the repulsion results in: (a) the HOMO energy level increased, (b) the electron cloud in HOMO distended, (c) the area of the negative NICS value extended, and (d) the VIE value lowered. So the superomolecule Li(3)-N(3)-Be is not only a new metal-nonmetal-metal type sandwich complex but also a new type electride, which comes from the interaction between the alkali superatom (Li(3)) and the nonmetal superatom (N(3)).