具有极性大侧基乙烯基聚合物的分子尺寸和均方二极矩

基于旋转异构态模型和生成矩阵代数方法,重新推导了大侧基聚合物均方回转半径和均方二极矩等基础量公式,应用于对聚乙烯咔唑（PVK）、聚对氯苯乙烯（PPCS）、聚乙烯砒啶（P2VP）和聚乙烯砒咯烷酮（PVP）链构象-构型依赖性质的研究.计算得到其无规链的均方二极矩特征比分别为0.55、0.57、0.48和0.37,均方回转半径特征比分别为2.07、1.74、1.11和1.52,全同链温度系数在？6.1×10？3～2.1×10？3K？1之间,范围比间同和无规链大.比较各特征比变化曲线规律,发现PPCS、PVP和P2VP的基础量分别受聚合物聚合度、规整程度和构象能的影响相对比较明显,而大侧基使PVK的均方二极矩和均方回转半径特征差异显著;对照改进的计算结果表明,在计算均方二极矩和回转半径时考虑极性侧基的方向和尺寸是十分重要的,在聚合物极性和柔性分析中不能忽略极性大侧基的影响.     

Examining the effect of the dipole moment on charge separation in donor-acceptor polymers for organic photovoltaic applications

A new low band gap copolymer PBB3 containing [6,6']bi[thieno[3,4-b]thiophenyl]-2,2'-dicarboxylic acid bis-(2-butyloctyl) ester (BTT) and 4,8-bis(2-butyloctyl)benzo[1,2-b:4,5-b']dithiophene (BDT) units was synthesized and tested for solar cell efficiency. PBB3 showed a broad absorbance in the near-IR region with a substantially red-shifted (by more than 100 nm) λ(max) at 790 nm as compared to the PTB series of polymers, which have been previously reported. The PBB3 polymer also showed both a favorable energy level match with PCBM (with a LUMO energy level of -3.29 eV) and a favorable film domain morphology as evidenced by TEM images. Despite these seemingly optimal parameters, a bulk heterojunction (BHJ) photovoltaic device fabricated from a blend of PBB3 and PC(71)BM showed an overall power conversion efficiency (PCE) of only 2.04% under AM 1.5G/100 mW cm(-2). The transient absorption spectra of PBB3 showed the absence of cationic and pseudo charge transfer states that were observed previously in the PTB series polymers, which were also composed of alternating thienothiophene (TT) and BDT units. We compared the spectral features and electronic density distribution of PBB3 with those of PTB2, PTB7, and PTBF2. While PTB2 and PTB7 have substantial charge transfer characteristics and also relatively large local internal dipoles through BDT to TT moieties, PTBF2 and PBB3 have minimized internal dipole moments due to the presence of two adjacent TT units (or two opposing fluorine atoms in PTBF2) with opposite orientations or internal dipoles. PBB3 showed a long-lived excitonic state and the slowest electron transfer dynamics of the series of polymers, as well as the fastest recombination rate of the charge-separated (CS) species, indicating that electrons and holes are more tightly bound in these species. Consequently, substantially lower degrees of charge separation were observed in both PBB3 and PTBF2. These results show that not only the energetics but also the internal dipole moment along the polymer chain may be critical in maintaining the pseudocharge transfer characteristics of these systems, which were shown to be partially responsible for the high PCE device made from the PTB series of low band gap copolymers.     

Exchange-hole dipole moment and the dispersion interaction

A simple model is presented in which the instantaneous dipole moment of the exchange hole is used to generate a dispersion interaction between nonoverlapping systems. The model is easy to implement, requiring no electron correlation (in the usual sense) or time dependence, and has been tested on various atomic and molecular pairs. The resulting C6 dispersion coefficients are remarkably accurate.     

Electric dipole moment of BrCl

The electric dipole moment of the BrCl molecule has been determined by a study of the Stark effect on nine hyperfine components of the J = 1 ← 0 rotational transition lying at 9 GHz. A direct diagonalisation procedure of the energy matrix of the total hamiltonian has been used and the electric dipole moment derived for the ground vibrational state of BrCl is |μ_o| = 0.519 ± 0.004 D.     

Exchange-hole dipole moment and the dispersion interaction revisited

We have recently introduced a model of the dispersion interaction based on the position-dependent dipole moment of the exchange hole [J. Chem. Phys. 122, 154104 (2005)]. The original derivation, involving simple dipole-induced-dipole electrostatics, was somewhat heuristic, however, and lacking in rigor. Here we present a much more satisfying derivation founded on second-order perturbation theory in the closure approximation and a semiclassical evaluation of the relevant interaction integrals. Expressions for C6, C8, and C10 dispersion coefficients are obtained in a remarkably straightforward manner. Their values agree very well with ab initio reference data on dispersion coefficients between the atoms H, He, Ne, Ar, Kr, and Xe. We also highlight the importance of the exchange-hole contribution to the dispersion coefficients, especially to C6.     

Microwave spectrum and dipole moment of norbornane

The microwave spectrum of norbornane has been studied in the 26–40 GHz region. The rotational constantsA = 3694.246 MHz B = 3212.566 MHz, C = 2774.813 MHz and the dipole moment μ = 0.091(8) D have been determined. These values are compared with electron diffraction data.     

Electric dipole moment of the diatomic AgBr molecule

Stark effect measurements on hyperfine components of the J = 3 – 2 rotational transition of ¹⁰⁷ Ag ⁷⁹ Br and ¹⁰⁹ Ag⁷⁹ Br at 11.5 GHz were carried out. The electric dipole moment derived for AgBr in its ground electronic and vibrational state is |μ_o| = 5.620 ± 0.030 D.     

Tautomerism in arylazonaphthols by dipole moment analysis

The azo-hydrazone equilibrium in some arylazonaphthols has been studied by dipole moment measurements and HMO calculations. Results show that in 1,4-derivatives comparable amounts of both forms are present. The 1,2-derivatives appear to be essentially azo-compounds, but an overestimate of azo proportion cannot be excluded.     

Electric dipole moment of the diatomic if molecule

The electric dipole moment of the IF molecule has been determined by a study of the Stark effect on the hyperfine components of the J = 1 ← 0 rotational transition lying in the 17 GHz region. The production of molecules was by microwave discharge of I₂ and C₆F₁₀(CF₃)₂. A direct diagonalisation of the energy matrix of the total hamiltonian has been used and the electric dipole moment derived for the ground vibrational state of IF is |μ₀ |= 1.948(20)D.     

Nonadiabatic contribution to the dipole moment of HCl

Nonadiabatic corrections to the dipole moments of HCl and DCl are calculated. Kaiser's deduction that the effect of the breakdown of the Born-Oppenheimer approximation is to reduce the dipole of DCl relative to HCl by about 10^?3 D is shown to be realistic.     

Perpendicular component of dipole moment in methyl groups

Consideration of the non equivalence of hydrogen atoms in a methyl group attached to a planar moiety indicates that a component of electric dipole moment should exist in a direction perpendicular to the local C ₃ axis of the CH₃ group. Semiempirical molecular-orbital computations produced estimates of this moment and of the barriers to internal rotation which may make this moment observable.     

Microwave spectrum and dipole moment of glycolic acid

More than 200 rotational transitions of glycolic acid (CH₂OHCOOH) have been assigned in the frequency range 18–40 GHz. Rotational constants and centrifugal distortion constants for the ground state and two vibrationally excited states were deduced. From Stark splittings the dipole moment was determined: μ_a = 1.913(5), μ_b = 0.995(14) and μ_total = 2.156(9) D.     

Microwave spectrum and dipole moment of 1,2,3,4-tetra-fluorobenzene

The microwave spectrum of the ground state of 1,2,3,4-tetrafluorobenzene has been measured in the range 7 to 25 GHz. A possible structure of the molecule is discussed. The rotational constants obtained are (in MHz): A = 2090.711 ± 0.012, B = 1196.257 ± 0.014, C = 760.880 ± 0.005. The observed inertial defect, Δ = 0.010 amu Ų, confirms the planar structure. A dipole moment of 2.42 ± 0.05 Debye was determined.     

Analytic matrix elements of the dipole moment and Herman-Wallis coefficients

Perturbation theory proves to be a powerful approach to obtain in analytic form both vibration-rotational energies and matrix elements of the dipole moment of diatomic molecules in terms of the expansion parameter = 2B _e/gw_e,B _e and _e being, respectively, the equilibrium rotational and harmonic vibrational spectral parameters. A systematic and efficient algorithm has been developed to execute such calculations with sufficient accuracy for most physical applications when the potential-energy function is accurately represented in the Dunham form. The method also provides analytic expressions of the Herman-Wallis coefficientsC _v ^v andD _v ^v for the vibration-rotational overtone bandsv ¹v for diatomic molecules in¹ electronic states.     

Permanent electric dipole moment of molybdenum carbide

High resolution optical spectroscopy has been used to study a molecular beam of molybdenum monocarbide (MoC). The Stark effect of the R(e)(0) and Q(fe)(1) branch features of the [18.6] (3)Pi(1)-X (3)Sigma(-)(0,0) band system of (98)MoC were analyzed to determine the permanent electric dipole moments mu(e) of 2.68(2) and 6.07(18) D for the [18.6] (3)Pi(1)(nu=0) and X (3)Sigma(-)(nu=0) states, respectively. The dipole moments are compared with the experimental value for ruthenium monocarbide [T. C. Steimle et al., J. Chem. Phys. 118, 2620 (2003)] and with theoretical predictions. A molecular orbital correlation diagram is used to interpret the observed and predicted trends of ground state mu(e) values for the 4d-metal monocarbides series.     

A dipole moment study of organo-chalcogen compoun

Analysis of the dipole moments of chalcogenoanisoles, the directions of which are given by those of their p-bromo derivatives, shows that the mesomeric moment decreases on passing from anisole to thioanisole, selenoanisole and telluroanisole (m = 1.1, 0.5, 0.25 and 0.18 D, respectively). In p-nitrochalcogenoanisoles and 1-chalcogenochroman-4-ones the interaction moment follows the reverse order, which is ascribed to the increasing sensitivity of the chalcogen mesomeric moment to the chalcogen atomic number and polarizability. The less-hindered (Te, O)-cis conformation is preferred for 2-acyl-3-methyltellurothiophenes and 3-acyl-2-methyltellurothiophenes (acyl: formyl or acetyl), and 3-formyl-4-methyltellurothiophene. Rotational isomerism in bis(2-furyl), bis(2-thienyl), bis(3-thienyl) and bis(2-selenienyl) ditelluride is also examined, and the dipole moments of 1-chalcogenochroman-4-ones, 2-chalcogenochroman-1-ones and 2-chalco-genochrom-1-ones analyzed.     

Calculations of force constants and dipole moment derivatives in silane

Force constants and dipole moment derivatives were calculated for the symmetric stretching and asymmetric stretching and bending vibrational modes for the silane molecule. The orbital exponents of small basis sets of Slater orbitals were optimized for silane in several geometrical configurations. It was determined that the addition of d orbitals to the silicon basis set has negligible effect on the calculated properties.     

On the enhancement of the electric dipole moment in molecular complexes

In the formation of molecular complexes an enhancement Δμ of the molecular dipole moment with respect to the vectorial sum of the moments of the monomers is often observed. The charge distribution provided by infrared intensity studies successfully predicts, in several cases, Δμ as due to polarization effects.