Effects of modifications of the heteroatoms on fine-tuning the photophysical proprieties of A-π-D-π-A small molecules for photovoltaic applications

An effective way to enhance the photovoltaic properties of a small molecule is to modify the side groups into donor units. Herein three news small molecules A-π-D-π-A, denoted Dye1-3, have been designed, from experimentally reported one noted (R), by insertion of various heteroatoms (S, O, Se) on the electron-donating benzodithiophene (Donor (D = BDT)) part. From the calculated results, the dihedral angle between BDT and side-chain affects the distribution of density on the ground state, gap energy, and intramolecular charge transfer of Dyes. In particular, the Dye3 compound, with the smaller dihedral angle, shows that the furan groups in the side chain of D, participates in the distribution of density on the ground state and consequently the charge transfer is improved. Additionally, Dye3 has the lower reorganization energy revealing that this material exhibits better charge mobility. Using the Scharber diagram, Dye3-PCBM heterojunction shows a power conversion efficiency of around 7%. Overall, this work suggests that the photovoltaic properties can be affected by the modification of heteroatoms on side groups of donor parts in small molecules.     

Electronic states and pseudo Jahn-Teller distortion of heavy metal-monobenzene complexes: M(C6H6) (M = Y, La, and Lu)

Monobenzene complexes of yttrium (Y), lanthanum (La), and lutetium (Lu), M(C(6)H(6)) (M = Y, La, and Lu), were prepared in a laser-vaporization supersonic molecular beam source and studied by pulsed-field ionization zero electron kinetic energy (ZEKE) spectroscopy and ab initio calculations. The calculations included the second-order perturbation, the coupled cluster with single, double, and perturbative triple excitation, and the complete active space self-consistent field methods. Adiabatic ionization energies and metal-benzene stretching frequencies of these complexes were measured for the first time from the ZEKE spectra. Electronic states of the neutral and ion complexes and benzene ring deformation were determined by combining the spectroscopic measurements with the theoretical calculations. The ionization energies of M(C(6)H(6)) are 5.0908 (6), 4.5651 (6), and 5.5106 (6) eV, and the metal-ligand stretching frequencies of [M(C(6)H(6))](+) are 328, 295, and 270 cm(-1) for M = Y, La, and Lu, respectively. The ground states of M(C(6)H(6)) and [M(C(6)H(6))](+) are (2)A(1) and (1)A(1), respectively, and their molecular structures are in C(2v) point group with a bent benzene ring. The deformation of the benzene ring upon metal coordination is caused by the pseudo Jahn-Teller interaction of (1(2)E(2)+1(2)A(1)+2(2)E(2)) e(2) at C(6v) symmetry. In addition, the study shows that spectroscopic behaviors of Y(C(6)H(6)) and La(C(6)H(6)) are similar to each other, but different from that of Lu(C(6)H(6)).     

The role of botrydienediol in the biodegradation of the sesquiterpenoid phytotoxin botrydial by Botrytis cinerea

The biotransformation of botrydienediol (6) labelled with deuterium on carbons C-10 and C-15 has been studied. This has led to modification of some previous assumptions about the biodegradative route of botrydial. The [10-²H,15-²H]-botry-1(9)-4-diendiol (12) was transformed into dehydrobotrydienediol derivatives 13-15 but it was not incorporated into secobotryane skeleton (7). In addition, three new sesquiterpenoids have been isolated, which shed further light on the secondary metabolites of Botrytis cinerea. From the point of view of persistence of these toxins in the food chain, the easy biotransformation and different biodegradative routes of botrydial (1), seem to indicate that the toxin may not persist in the plant for a long time as it will be metabolized by the fungi and the plant.     

High resolution vacuum ultraviolet emission spectrum of D(2) from 78 to 103 nm: The D (1)Pi(u)-->X (1)Sigma(g) (+) and D(') (1)Pi(u) (-)-->X (1)Sigma(g) (+) band systems

The emission spectrum of the D(2) molecule has been studied at high resolution in the vacuum ultraviolet region 78.5-102.7 nm. A detailed analysis of the two D (1)Pi(u)-->X (1)Sigma(g) (+) and D(') (1)Pi(u) (-)-->X (1)Sigma(g) (+) electronic band systems is reported. New and improved values of the level energies of the two upper states have been derived with the help of the program IDEN [V. I. Azarov, Phys. Scr. 44, 528 (1991); 48, 656 (1993)], originally developed for atomic spectral analysis. A detailed comparison is made between the observed energy levels and solutions of coupled equations using the newest ab initio potentials by Wolniewicz and co-workers [J. Chem. Phys. 103, 1792 (1995); 99, 1851 (1993); J. Mol. Spectros. 212, 208 (2002); 220, 45 (2003)] taking into account the nonadiabatic coupling terms for the D (1)Pi(u) state with the lowest electronic states B (1)Sigma(u) (+), C (1)Pi(u), and B(') (1)Sigma(u) (+). A satisfactory agreement has been found for most of the level energies belonging to the D and D(') states. The remaining differences between observation and theory are probably due to nonadiabatic couplings with other higher electronic states which were neglected in the calculations.     

Multifractal Formalism for Selfsimilar Functions Expanded in Singular Basis

Selfsimilar functions can be written as the superposition of similar structures, at different scales, generated by a function g. Their expressions look like wavelet decompositions. In the case where g is regular, the multifractal formalism has been proved for the corresponding selfsimilar function, for Hölder exponents smaller than the regularity of g. In this paper, we show, in the case where g is the Schauder function (or the Haar function or a spline-type wavelet), that for larger Hölder exponents, the singularities of g can disturb the Hölder exponents of the associated selfsimilar function, modify the shape of the spectrum of singularities, and finally affect the validity of the multifractal formalism.     

Distribution of Resonances and Decay Rate of the Local Energy for the Elastic Wave Equation

We study resonances (scattering poles) associated to the elasticity operator in the exterior of an arbitrary obstacle with Neumann or Dirichlet boundary conditions. We prove that there exists an exponentially small neighborhood of the real axis free of resonances. Consequently we prove that for regular data, the energy for the elastic wave equation decays at least as fast as the inverse of the logarithm of time. According to Stefanov–Vodev ([SV1, SV2]), our results are optimal in the case of a Neumann boundary condition, even when the obstacle is a ball of ℝ³. The main difference between our case and the case of the scalar Laplacian (see Burq [Bu]) is the phenomenon of Rayleigh surface waves, which are connected to the failure of the Lopatinskii condition. Received: 22 February 2000 / Accepted: 28 June 2000     

Thermolysis of symmetrical dithiobiurea and thioureidoethylthiourea derivatives

Microwave and thermal heterocyclization of N,N′‐disubstituted hydrazinecarbothioamide 1a,b and substituted thioureidoethylthioureas 2a–c as well as 1‐phenyl‐3[2‐(3‐phenylthio‐ureido)phenyl]thiourea 6 are reported. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:535–541, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10188     

Magnetic Nanoparticle Thermometry via Controlled Diffusion

The process of magnetic nanoparticle heating releases enormous amounts of thermal energy. Through typical calorimetric analyses, the total thermal energy released can be easily quantified; however, knowledge of nanoscale temperature is necessary. Herein, a novel method of nanoscale thermometry by analyzing intra-particle diffusion in core–shell nanoparticles is proposed. Heating the iron cores with an alternating magnetic field in a saline suspension encourages the diffusion of sodium ions into the silica shells of the particles, which is modeled numerically; however, experimental measurements are needed in order to provide accurate diffusivity estimations. After determining the diffusion characteristics from X-ray photoelectron spectroscopy) depth profiling of silica films, energy dispersive analysis with high-resolution transmission electron microscopy measures the sodium ion gradient within single particles before and after heating. When compared directly to the numerical simulations, the results indicate that the temperature gradient between particles and saline suspension reaches significantly higher temperatures than the macro-scale temperature of the solution. By accurately knowing the thermal gradient between nanoparticles and the surrounding medium, nanoparticles can be engineered to limit surface resistances as much as possible and promote high rates of thermal energy transfer.     

Phenylbiguanide as electron donor in heterocyclic synthesis

Phenylbiguanide reacts with some π-acceptors such as TCNE, TCNQ, CNIND, DCNQ, and CHL-o, if any. opy; 2003 Wiley Periodicals, Inc. Heteroatom Chem 15:63–66, 2004; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10213