Chemical Physics Letters (v.487, #4-6)

Contents (iii-x).

Plasmonic coupling in noble metal nanostructures by Prashant K. Jain; Mostafa A. El-Sayed (153-164).
Near-field coupling between the plasmon excitations on neighboring noble metal nanoparticles modulates the radiative and non-radiative properties of the nanostructure.Noble metal nanostructures display unique and strongly enhanced optical properties due to the phenomenon of localized surface plasmon resonance (LSPR). In assemblies or complex noble metal nanostructures, individual plasmon oscillations on proximal particles can couple via their near-field interaction, resulting in coupled plasmon resonance modes, quite akin to excitonic coupling in molecular aggregates or orbital hybridization in molecules. In this frontier Letter we discuss how the coupling of plasmon modes in certain nanostructure geometries (such as nanoparticle dimers and nanoshells) allows systematic tuning of the optical resonance, and also the confinement and enhancement of the near-field, making possible improved refractive-index sensing and field-enhanced spectroscopy and photochemistry. We discuss the polarization, orientation, and distance-dependence of this near-field coupling especially the universal size-scaling of the plasmon coupling interaction. In addition to radiative properties, we also discuss the effect of inter-particle coupling on the non-radiative electron relaxation in noble metal nanostructures.

Fluorescence spectroscopy and signalling from optically-tweezed aerosol droplets by Kerry J. Knox; Rachel Symes; Jonathan P. Reid (165-170).
Sequential images showing rapid evaporation of a trapped aerosol droplet in <0.08 s following inclusion of Rhodamine B by coalescence.Spectroscopic signatures from fluorescing optically-tweezed aqueous droplets in air and polymer beads in solution are presented and compared. Rapid fluorescence signalling is reported for the aerosol droplets with a time resolution of 34 ms, achieved by dosing a trapped droplet with a fluorescent dye via coalescence with a flow of dye-doped aerosol. The quality factors of cavity-enhanced resonances present in the emission spectra are compared with those reported in a range of other studies. Rapid aerosol droplet heating is observed following coalescence for the case of high dye-loading.

Theoretical study on structures and stability of GeSiN and GeCP radicals by Yi Pan; Guang-hui Chen; Di Wu; Zhi Lv; Zhi-ru Li; Dan Li; Xiao-chun Huang (171-176).
The structures and isomerization of GeSiN and GeCP species are explored at density functional theory and ab initio levels.The structures, isomerization and spectroscopies of GeSiN and GeCP radicals are explored at density functional theory and ab initio levels. For GeSiN, the global minimum is linear GeNSi 1, in agreement of the mass spectra detection, which can be qualitatively described as a resonance hybrid of |Ge=N|–Si|• and •|Ge–N|=Si|, where the latter contributes more. As to GeCP, the lowest-lying isomer is linear GeCP 1 resonating between •|Ge–CP| and |Ge=C=P|• with the former contributes more, followed by a cyclic isomer cGeCP 2 at 8.8 kcal/mol. All above three species with large kinetic stability (about 10 kcal/mol barrier) should be experimentally important.

Photocyclization of trans-stilbene induced by an ultrafast laser pulse by Chen-Wei Jiang; Rui-Hua Xie; Fu-Li Li; Roland E. Allen (177-182).
We predict that photocyclization of trans-stilbene to 4a,4b-dihydrophenanthrene (DHP) can be achieved with a femtosecond-scale laser pulse.We predict that photocyclization of trans-stilbene to 4a,4b-dihydrophenanthrene (DHP) can be achieved with a femtosecond-scale laser pulse. Specifically, we have performed dynamical simulations in which the original trans-stilbene molecule is observed first to isomerize to cis-stilbene (as an excited-state intermediate) after more than one picosecond, and then to form a new bond to become DHP, after a few hundred additional femtoseconds. The process is initiated by excitation from the S 0 electronic state to S 1 , with subsequent de-excitation at avoided crossings.

PO can be formed selectively due to its relatively low activation energy (9.3 kcal/mol).The gas-phase radical chain reactions which utilize O2 as the oxidant to produce propylene oxide (PO) are investigated through theoretical calculations. The transition states and energy profiles were obtained for each path. The rate constants were also calculated. The energetics for the competing pathways indicate that PO can be formed selectively due to its relatively low activation barrier (9.3 kcal/mol) which is in a good agreement with the experimental value (11 kcal/mol) of gas-phase propylene epoxidation. The formation of the acrolein and combustion products have relatively high activation barriers and are not favored. These results also support the recent experimental findings.

First-principles study of the hexahalogenotechnetate(IV) ions TcX 6 2 - [X = Cl, Br] by Philippe F. Weck; Eunja Kim; Kenneth R. Czerwinski (190-193).
All-electron scalar relativistic calculations of the structural and electronic properties of the octahedral hexahalogenotechnetate(IV) ions TcX 6 2 - [X = Cl, Br] have been performed using spin-polarized density functional theory.We report all-electron scalar relativistic calculations of the structural and electronic properties of the octahedral hexahalogenotechnetate(IV) ions TcX 6 2 - [X = Cl, Br] using spin-polarized density functional theory. The calculated bond distances are in good agreement with X-ray diffraction (XRD) and extended X-ray absorption fine structure (EXAFS) data available for salts of hexachloride and hexabromide technetate ions. Molecular-orbital analysis shows the importance of the hybridization between Tc 4 d orbitals and p orbitals of the ligands. Normal modes of vibration of the hexachloride and hexabromide complexes of Tc and Re have also been computed and assessed by comparison with spectral data for salt crystals of technetate/rhenate complex ions.

Synthesis, spectroscopy and structure of diiodofuroxan by Tibor Pasinszki; Melinda Krebsz; Gábor Vass (194-199).
Structure of diiodofuroxan has been investigated by experimental and theoretical methods.Diiodofuroxan (3,4-diiodo-1,2,5-oxadiazole 2-oxide) has been investigated for the first time in the gas phase by UV photoelectron spectroscopy, and in the solid phase by mid-infrared and Raman spectroscopy. The individual spectroscopies provide a detailed investigation into the vibrational and electronic character of the molecule, and are supported by quantum-chemical calculations. The molecule is confirmed by calculations at the B3LYP and CCSD(T) levels as a planar five-membered ring with a strong exocyclic and a relatively weak endocyclic N–O bond. Diiodofuroxan, upon thermolysis, does not cleave to the ICNO monomer, but leads to the formation of ONCCNO and iodine.

Density functional theoretical study of transition metal carbohydrazide perchlorate complexes by Huisheng Huang; Tonglai Zhang; Jianguo Zhang; Liqiong Wang (200-203).
The performance of SVWN5, PBE, TPSS, B3LYP and HSE functionals for reproducing the geometries of transition metal carbohydrazide perchlorates MCP (M = Co, Ni, Zn, Cd) is assessed. The HSE functional yields the most accurate geometry. Detailed NBO analyses indicate that the metal–ligand bonding scheme and mechanism of detonation initiation of CoCP and NiCP are quite different from those of ZnCP and CdCP. The correlation of energy gap with impact sensitivity and the thermochemical properties of these complexes are also discussed.The geometry, electronic structure and thermochemical properties of transition metal carbohydrazide perchlorates MCP [M = Co(II), Ni(II), Zn(II), Cd(II)] are investigated via density functional theory (DFT). The results show that the Heyd–Scuseria–Ernzerhof (HSE) functional yields the most accurate geometry. Detailed NBO analyses indicate that the metal–ligand interactions of CoCP and NiCP are covalent, whereas those of ZnCP and CdCP are ionic in nature. The mechanism of detonation initiation in covalent and ionic complexes is entirely different. There is a relationship between the energy gap and impact sensitivity. The thermochemical properties show that the formations of these complexes are exothermic; moreover, CoCP and NiCP are easier to decompose than ZnCP.

Vanadium-doped small silicon clusters: Photoelectron spectroscopy and density-functional calculations by Hong-Guang Xu; Zeng-Guang Zhang; Yuan Feng; Jinyun Yuan; Yuchao Zhao; Weijun Zheng (204-208).
V 2 Si 6 - has D 3 d symmetry, with the six Si atoms forming a six-membered ring in the chair conformation, similar to cyclohexane; the two vanadium atoms are bound to each other through a δ bond.Vanadium-doped small silicon clusters, VSi n - and V 2 Si n - (n  = 3–6), have been studied by anion photoelectron spectroscopy. The vertical detachment energies (VDEs) and adiabatic detachment energies (ADEs) of these clusters were obtained from their photoelectron spectra. We have also conducted density-functional calculations of VSi n - and V 2 Si n - clusters and determined their structures by comparison of theoretical calculations with experimental results. Our results show that two V atoms in V 2 Si n - clusters tend to form a strong V–V bond. V 2 Si 6 - has D 3 d symmetry with the six Si atoms forming a chair like six-membered ring similar to the ring in cyclohexane and the two vanadium atoms are joined with a δ bond.

Femtosecond interferometry is demonstrated to be a viable tool for controlling photochemical processes. Under specific conditions it resembles the signature of both electron and nuclear dynamics.The interaction of a molecule with the laser field generated by two time-shifted interfering femtosecond laser pulses is shown to control electron and nuclear dynamics. We demonstrate that the product yields caused by the interferometric dissociation carry the signature of time dependent electronic polarization due to the correlated electronic and nuclear dynamics induced in the region of partial overlap of two laser pulses. Thus, the two pulse technique provides a powerful tool for bridging the gap between electron and nuclear dynamics.

Planar and pyramidal conformers of the alkali–ethylene complexes by Denis Hagebaum-Reignier; Vincent Ledentu; Gwang-Hi Jeung (214-219).
Unusual planar conformation of the Li–ethylene complexes due to a d(δ) → π∗ interaction.Two geometric forms of the ethylene complex with an alkali atom are studied by ab initio methods. The lowest bound state of LiC2H4 belongs to the B2 point-group symmetry in the pyramidal conformer lying 0.20 eV higher than the dissociation asymptote into the ground state, while it is A2 in the planar conformer lying 0.20 eV higher than the former state. The 12A2 state is more ionic than the 12B2 state with the effective metal charges of 0.62 and 0.47, respectively. We give here the potential energy surfaces, the electronic structures and spectroscopic properties of LiC2H4, NaC2H4 and KC2H4.

Comparison of ab initio molecular properties of EDO-TTF with the properties of the (EDO-TTF)2PF6 crystal by Gerrit-Jan Linker; Paul H.M. van Loosdrecht; Piet van Duijnen; Ria Broer (220-225).
Intrinsic geometry of EDO-TTF (side view) and the HOMO and HOMO-1 molecular orbitals.We performed ab initio quantum chemical calculations for the geometrical and electronic structure of the EDO-TTF (ethylenedioxy-tetrathiafulvalene) molecule using HF, CASSCF and DFT methods. We compare these in vacuo results with the properties of the (EDO-TTF)2PF6 crystal at near room temperature. We demonstrate that, by bending and charging the molecule in vacuum, the deformation that is thought to be the origin of charge ordering in this material is an inherent property of the EDO-TTF molecule. We further show that deformations can be readily made at ambient temperatures.

Azo-group dihedral angle torsion dependence on temperature: A theorerical–experimental study by Leonardo De Boni; Carlos Toro; Sérgio C. Zilio; Cleber R. Mendonca; Florencio E. Hernandez (226-231).
For this family of azoaromatic compounds, changes in the –N=N– dihedral angle strongly affect the electronic absorption spectrumQuantum chemical calculations were carried out to explain the observed shifts in the absorption spectrum of different azo-aromatic compounds due to changes in the dihedral angle of the azo-group. Our results reveal that the π−π∗ transition presents a hypsochromic shift and an oscillator strength drop upon increase of the dihedral angle. Nevertheless, the n−π∗ transition exhibits the opposite behavior. This effect is attributed to the reduction in the π−electron conjugation length of the molecule. Experimentally, we performed temperature dependence measurements of the linear absorption spectrum. Both the theoretical and experimental results demonstrate that small energy changes are mirrored in the electronic transitions of conjugated linear molecules.

Solid-state 95Mo NMR of mixed-valence polyoxomolybdates (V, VI) with localized or delocalized d 1 electrons by Takahiro Iijima; Toshihiro Yamase; Masataka Tansho; Tadashi Shimizu; Katsuyuki Nishimura (232-236).
The Mo V, VI site in the mixed-valence polyoxomolybdate (V, VI) exhibited a very large chemical shift of 95Mo NMR.We report solid-state 95Mo NMR of Mo V , Mo V,VI and Mo VI species in mixed-valence polyoxomolybdates (V, VI) with localized or delocalized d 1 electrons. Parameters about chemical shift and quadrupole interactions of 95Mo in diamagnetic crystals of [ Me 3 NH ] 6 [ H 2 Mo 12 V O 28 ( OH ) 12 ( Mo VI O 3 ) 4 ] · 2 H 2 O ( 1 ) with localized electrons and [ NMe 4 ] 2 [ NH 4 ] 8 [ ( Mo 6 VI Mo V O 23 ) 2 ] · 8 H 2 O ( 2 ) with delocalized ones were obtained by simulation of magic-angle-spinning (MAS) 95Mo NMR spectra. The isotropic and anisotropic chemical shifts of sites of Mo V in 1 and Mo V, VI in 2, respectively, exhibited absolute values quite larger than those of other Mo VI sites, which is examined by quantum chemical calculations.

The complex core level spectra of CeO2: An analysis in terms of atomic and charge transfer effects by P.S. Bagus; C.J. Nelin; E.S. Ilton; M. Baron; H. Abbott; E. Primorac; H. Kuhlenbeck; S. Shaikhutdinov; H.-J. Freund (237-240).
Core level spectra of metal oxides often exhibit a pronounced fine structure which is related to the physical and chemical properties of the oxide. For the case of the Ce 4s and 5s levels of CeO2(1 1 1) the fine structure is calculated with a parameter-free ab initio theoretical approach.We present a rigorous parameter-free theoretical treatment of the Ce 4s and 5s photoelectron spectra of CeO2. The currently accepted model explains the satellite structure in the photoelectron spectra in terms of mixed valence (Ce 4f0 O 2p6, Ce 4f1 O 2p5, and Ce 4f2 O 2p4) configurations. We show that charge transfer (CT) into Ce 5d as well as configurations involving intra-atomic movement of charge must be considered in addition and compute their contributions to the spectra.

An integral equation theory for structural fluctuation in molecular liquid by Daisuke Yokogawa; Hirofumi Sato; Shigeyoshi Sakaki (241-245).
We present an integral equation theory to treat structural fluctuation of a molecule based on classical density functional theory. The present method was successfully applied to several liquids consisting of middle-length chain molecule. Temperature and density dependence of the structural function is also presented.We present an integral equation theory to treat structural fluctuation of a molecule based on classical density functional theory. Because a chain molecule is flexible enough and many conformations coexist in its liquid system, an efficient sampling in molecular simulation is not readily achieved in general. The present method was successfully applied to several liquids consisting of such a chain molecule. Temperature and density dependence of the structural function is also presented.

The ultrafast excited-state dynamics of aminoperylene in liquid solutions is dominated by solvent relaxation.The photophysics of aminoperylene (APe) in various solvents, including a room-temperature ionic liquid, has been investigated by steady-state and femtosecond transient absorption spectroscopies. The ultrafast excited-state dynamics originates from the solvation of the polar S1 state and not from a transition from a locally-excited to a charge-transfer state, as found with perylene-dimethylaniline. Addition of acid yields the protonated form APeH+, which exhibits similar photophysical properties than perylene, due to the suppression of the charge-transfer character of the S0–S1 transition. However, excited-state proton transfer, resulting to the formation of APe in the S1 state, is observed in methanol.

Effects of carbon on the weak ferromagnetism in doped GaN by Lin Yu; Zeyan Wang; Meng Guo; Donghong Liu; Ying Dai; Baibiao Huang (251-255).
Ferromagnetism is possible exist in doped GaN with high and appropriate C concentration. Figures show that the measured magnetization of both has a weak but discernable hysteresis indicative of ferromagnetic interactions at room temperature for the as-grown C-doped GaN samples.The magnetic properties of carbon doping GaN have been examined in combination of first-principles density functional calculations and experiments. The calculated results indicate that a single C dopant produces a spin magnetic moment of about 0.7 μB and the two-C-atoms form a stable ferromagnetic coupling when their distance lies around 5–6 Å, which can be explained by the C2p magnetic orbitals overlapping via the nearest Ga p-d orbitals and next-nearest N2p orbitals. The ferromagnetism is also observed in our C-doped GaN samples with high C/Ga ratio.

The frequency dispersion of the linear susceptibility of 3-methyl-4-nitropyridine N-oxide crystal can be reproduced from using an electrostatic interaction scheme and first principle molecular responses.An electrostatic interaction scheme is applied to evaluate the macroscopic linear susceptibilities of 2-methyl-4-nitroaniline, m-nitroaniline, 3-methyl-4-nitropyridine N-oxide and 2-carboxylic acid-4-nitropyridine-1-oxide crystals. The molecular polarizabilities have been determined from first principles calculations while a distribution scheme is employed to evaluate the Lorentz-factor tensors. It is shown that when employing an appropriate distribution scheme, where the molecules are divided in polarizable sites placed on each heavy atom, this approach reproduces well the experimental crystal linear susceptibilities and its frequency dispersion. Moreover, averaging the Lorentz-factor tensors over the submolecules has only a weak impact on the agreement with experiment.

Molecular alignment effects on spectroscopic properties 2,1,3-benzothiadiazole guested in liquid–crystalline compounds by P. Alliprandini-Filho; G.F. Borges; W.B. Calixto; I.H. Bechtold; A.A. Vieira; R. Cristiano; H. Gallardo; R.A. Silva; N.M. Barbosa Neto; Alexandre Marletta (263-267).
This work concerns about the polarized emission by a new compound based on 2,1,3-benzothiadiazole guested in liquid crystals structures. Besides, we show that the ellipsometry technique is a useful tool to investigate phase transitions in fluorescent systems.This Letter reports about the molecular alignment effects on absorbance and emission properties of a new compound based on 2,1,3-benzothiadiazole guested in liquid crystals. The molecular ordering is available for different chromophore concentrations. Despite of the increasing in molecular disorder above the concentration of 0.20%, samples always present a high degree of linear polarization in fluorescence. A considerable amount of polarized emission is observed during the isotropic phase (T  > 58 °C), which is attributed to emission of light by aligned molecules before loosing the coherence among them. Finally, we demonstrate the feasibility of ellipsometry technique to investigate phase transitions in fluorescent systems.

Molecular vibrations in metal–single-molecule–metal junctions by Kazumichi Yokota; Masateru Taniguchi; Tomoji Kawai (268-271).
Molecular vibrational analyses of single–molecule junctions based on density functional theory using a Au13–benzenedithiolate–Au13 junction as a model.Molecular vibrations in a metal–single-molecule–metal junction were studied based on density functional theory using a single benzenedithiolate molecule connected between gold clusters. We found that the difference in vibrational energy between an isolated benzenedithiol and the single-molecule junction is less than 3% in the energy range above 540 cm−1, where sulfur atoms contribute little to molecular vibrations. The finding implies that we can predict the peak energy in the inelastic electron tunneling spectrum of the single-molecule junction in the high energy range by vibrational analyses of isolated molecules.

Controllable stacked disk morphologies of charged diblock copolymers by Monojoy Goswami; Bobby G. Sumpter; Jimmy Mays (272-278).
To form the disk shape stacked morphologies, it is required to have a balance between electrostatic energy with the entropic and hydrophobic interactions.Monte Carlo simulations are used to demonstrate the controlled stacking of charged block copolymer disk morphologies that can be obtained under certain thermodynamic conditions. We examine a partially charged block copolymer where 75% of the blocks are neutral and 25% of the blocks are charged. The presence of strong electrostatic interactions promotes charge agglomeration thereby changing morphologies in these systems. This study relates different thermodynamic quantities for which disk-like stackings can be obtained. The long-range order can be sustained even if hydrophobicity is increased albeit with lower dimensional structures. Our simulation results agree very well with recent experiments and are consistent with theoretical observations of counterion adsorption on flexible polyelectrolytes.

(a) Space-resolved tunneling spectra and (b) STM image of a unisized monatomic-layered platinum cluster disk (size of 30 atoms) bonded to a silicon(1 1 1) surface.A local density of electronic states and a local HOMO–LUMO gap of a monatomic-layered platinum cluster with a size of 30 (Pt30 cluster disk) on a silicon(1 1 1) surface were measured by space-resolved tunneling spectroscopy. It has been found that (1) both occupied and unoccupied electronic orbitals are delocalized due to Pt–Pt metallic interaction in the cluster disk and (2) electrons in the occupied orbitals of the cluster disk are transferred to the adjacent silicon atoms so as to induce two-dimensional charge polarization of the cluster disk. The center of the cluster disk is charged positively, while the boundary between the cluster disk and the silicon surface is charged negatively.

Oxygen coordination of aluminum cations in dehydrated AlPW12O40 investigated by solid-state NMR spectroscopy by Arne Bressel; Jörg Frey; Urszula Filek; Bogdan Sulikowski; Dieter Freude; Michael Hunger (285-290).
Dehydrated aluminumdodecatungstophosphate (AlPW12O40) was investigated by 27Al MAS NMR spectroscopy in magnetic fields of 9.4 and 17.6 T. Two kinds of octahedrally coordinated, two kinds of penta-coordinated, and a small amount of tetrahedrally coordinated aluminum cations were found. Comparison with 1H MAS NMR spectroscopic studies indicates that the dehydroxylation of aluminum OH groups at temperatures of 473 and 573 K is accompanied by a partially irreversible change of the oxygen coordination of aluminum cations.Dehydrated aluminumdodecatungstophosphate (AlPW12O40) was investigated by 27Al MAS NMR spectroscopy in magnetic fields of 9.4 and 17.6 T. Two kinds of octahedrally coordinated (δ 27Al  = 1–2 ppm, C Q  = 2.4–2.5 MHz, and δ 27Al  = 4–6 ppm, C Q  = 6.0–6.5 MHz), two kinds of penta-coordinated (δ 27Al  = 24–30 ppm, C Q  = 7.0–7.3 MHz, and δ 27Al  = 44 ppm, C Q  = 7.5–8.7 MHz), and a small amount of tetrahedrally coordinated aluminum cations (δ 27Al  = 65 ppm, C Q  = 8.2–8.5 MHz) were found. Comparison with 1H MAS NMR spectroscopic studies indicates that the dehydroxylation of aluminum OH groups (δ 1H  = 4.2 ppm and 5.6 ppm) at temperatures of 473 and 573 K is accompanied by a partially irreversible change of the oxygen coordination of aluminum cations.

Atomistic and mesoscale simulation of polymer electrolyte membranes based on sulfonated poly(ether ether ketone) by P.V. Komarov; I.N. Veselov; P.P. Chu; P.G. Khalatur; A.R. Khokhlov (291-296).
Snapshots from MD and DDFT simulations illustrating the structure of hydrated sPEEK membrane.We report results of multiscale simulations of a hydrated ionomer membrane based on sulfonated poly(ether ether ketone) (sPEEK) that constitutes an important class of the promising membrane materials for fuel cell applications. Using atomistic and field-theoretic simulation techniques – classical molecular dynamics and dynamic density functional theory – we study the processes of self-organization in sPEEK membranes in the presence of water. At the same water content, both simulation techniques predict a similar structure of the hydrated membranes. The observed membrane morphology can be represented as a topologically complex sponge-like network consisting of irregular water-filled channels. Compared to Nafion, the channels in the sPEEK membrane are narrower. Nevertheless, the estimated percolation threshold in sPEEK is lower than for Nafion.

Snapshots from DDFT and DPD simulations illustrating the guided self-assembly of cylinder forming block copolymers under confinement.We discuss a simple and robust approach to control the orientation of cylindrical microdomains in block copolymer films. The approach is based on the so-called double phase separation occurring in the binary blend of incompatible compositionally asymmetric block copolymers and their selective adsorption on a homogeneous surface. As a proof-of-concept, we perform mesoscale simulations, using dynamic density functional theory and dissipative particle dynamics, and show that the target morphology with perpendicularly oriented cylinders can be thermodynamically stable for rather thick films when the intrinsic hexagonal period of the majority bulk phase is commensurate with the surface-induced pattern formed by the strongly adsorbed minority component.

Photophysics of a fluorescent non-natural amino acid: p-Cyanophenylalanine by Arnaldo L. Serrano; Thomas Troxler; Matthew J. Tucker; Feng Gai (303-306).
The fluorescence lifetime of p-cyanophenylalanine is sensitive to hydrogen bonding.The non-natural amino acid p-cyanophenylalanine (PheCN) has recently emerged as a useful fluorescent probe of proteins; however, its photophysical properties have not been systematically examined. Herein, we measure the fluorescence quantum yield and the fluorescence lifetime of PheCN in a series of solvents. It is found that the fluorescence lifetime of PheCN shows a linear dependence on the Kamlet–Taft parameter α of the protic solvents used, indicating that the solute-solvent hydrogen bonding interactions mediate the non-radiative decay rate. Thus, results of this study provide a basis for quantitative application of PheCN fluorescence in protein conformational studies.

Investigation of the EPR and local structure for [Mn(H2O)6]2+ complex in MSnF6·6H2O:Mn2+ (M = Zn, Co) and Cd(BF4)2·6H2O:Mn2+ systems at different temperature.The relationship between the local structure and EPR spectrum is studied by diagonalizing the complete energy matrices for Mn2+ in a trigonal ligand-field. The results show that the degree of distortion increases with temperature increasing whether it is compressed or elongate distortion, and the distorted tendency of the local structure is different according to the sign of D. Meanwhile, the distortion of Cd(BF4)2·6H2O:Mn2+ system is more sensitive to temperature than that of ZnSnF6·6H2O:Mn2+ system. Moreover, the EPR parameter D is closely associated with the local structure parameters R and θ while (a  −  F) is mainly concerned with R.

Two illumination modes in fluorescence microscope provide full absorption anisotropy of luminescent nanoparticles.We introduce theoretically and demonstrate experimentally a method for the determination of three-dimensional absorption anisotropy (three-dimensional linear dichroism) of single luminescent nanoparticles. The anisotropy is measured by monitoring polarization-modulated fluorescence intensity excited alternately by epi-illumination and by total internal reflection. As an example of the application of the method, three-dimensional linear dichroism measured on single light-harvesting systems of photosynthetic bacteria is presented.

Quantum mechanical analyses based on NBO and AIM methods indicate that the sulfilimine bond is a coordinate covalent (dative) single bond, not a double bond as generally believed.Using quantum mechanical calculations in combination with AIM and NBO analyses, we investigate the properties of the sulfilimine bond, which has been recently detected in collagen IV [Vanacore et al., Science 325 (2009) 1230]. Contrary to the general belief that this is a double bond, –N=S<, our analysis of the wavefunction of a model compound indicates it being a coordinate covalent (dative) single bond, –N ← S<, with a strong polarization towards nitrogen.

Author Index (320-324).