On the mechanism of conductivity enhancement in poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) film through solvent treatment

A benchmark set of 28 medium-sized organic molecules is assembled that covers the most important classes of chromophores including polyenes and other unsaturated aliphatic compounds, aromatic hydrocarbons, heterocycles, carbonyl compounds, and nucleobases. Vertical excitation energies and one-electron properties are computed for the valence excited states of these molecules using both multiconfigurational second-order perturbation theory, CASPT2, and a hierarchy of coupled cluster methods, CC2, CCSD, and CC3. The calculations are done at identical geometries (MP26-31G*) and with the same basis set (TZVP). In most cases, the CC3 results are very close to the CASPT2 results, whereas there are larger deviations with CC2 and CCSD, especially in singlet excited states that are not dominated by single excitations. Statistical evaluations of the calculated vertical excitation energies for 223 states are presented and discussed in order to assess the relative merits of the applied methods. CC2 reproduces the CC3 reference data for the singlets better than CCSD. On the basis of the current computational results and an extensive survey of the literature, we propose best estimates for the energies of 104 singlet and 63 triplet excited states.

https://www.chemie.hhu.de/fileadmin/redaktion/Fakultaeten/Mathematisch-Naturwissenschaftliche_Fakultaet/Chemie/SFB_663/Veroeffentlichungen/C4_043.pdf

Benchmarks for electronically excited states: CASPT2, CC2, CCSD, and CC3

The application of broken symmetry density functional calculations to homobinuclear and heterobinuclear transition metal complexes produces good estimates of the exchange coupling constants as compared to experimental data. The accuracy of different hybrid density functional theory methods was tested. A discussion is presented of the different methodological approaches that apply when a broken symmetry wave function is used with either Hartree–Fock or density functional calculations. ©1999 John Wiley & Sons, Inc. J Comput Chem 20: 1391–1400, 1999

Broken symmetry approach to calculation of exchange coupling constants for homobinuclear and heterobinuclear transition metal complexes

Tetrathiafulvalene (TTF) and its derivatives were originally prepared as strong electron-donor molecules for the development of electrically conducting materials. This Review emphasizes how TTF and its derivatives offer new and in some cases little-exploited possibilities at the molecular to the supramolecular levels, as well as in macromolecular aspects. TTF is a well-established molecule whose interest goes beyond the field of materials chemistry to be considered an important building block in supramolecular chemistry, crystal engineering, and in systems able to operate as machines. At the molecular level, TTF is a readily available molecule which displays a strong electron-donor ability. However, its use as a catalyst for radical-polar crossover reactions, thus mimicking samarium iodide chemistry, has only recently been addressed. Important goals have been achieved in the use of TTF at the macromolecular level where TTF-containing oligomers, polymers, and dendrimers have allowed the preparation of new materials that integrate the unique properties of TTF with the processability and stability that macromolecules display. The TTF molecule has also been successfully used in the construction of redox-active supramolecular systems. Thus, chemical sensors and redox-switchable ligands have been prepared from TTF while molecular shuttles and molecular switches have been prepared from TTF-containing rotaxanes and catenanes. A large synthetic effort has been devoted to the preparation of the so-called organic ferromagnets, many of which are derived from TTF. The main task in these systems is the introduction of ferromagnetic coupling between the conduction electrons and localized electrons. TTF has also played a prominent role in molecular electronics where TTF-containing D-sigma-A molecules have allowed the preparation of the first confirmed unimolecular rectifier. Recently, it has been confirmed that TTF can display efficient nonlinear optic (NLO) responses in the second and third harmonic generation as well as a good thermal stability. These findings can be combined with the redox ability of TTF as an external stimuli to provide a promising strategy for the molecular engineering of switchable NLO materials. Fullerenes endowed with TTF exhibit outstanding photophysical properties leading to charge-separated (CS) states that show remarkable lifetimes.

New Concepts in Tetrathiafulvalene Chemistry.

Orbital interactions, electron delocalization and spin coupling in iron-sulfur clusters

Unrestricted Hartree–Fock theory and its applications to molecules and chemical reactions

A molecular-orbital theoretical classification of reactions of singlet ground-state molecules

Measurements of the optical absorption spectra of the sublimed films of adenine, guanine, cytosine, thymine, and uracil were extended down to 120 mμ at room temperature. Several remarkable absorption peaks were found to exist below 190 mμ in addition to the already known ones near 260 mμ and 200 mμ. The intensities of these peaks were comparable to or, in some cases, even larger than those near 260 mμ and 200 mμ. It was found that the relative intensities of the absorption peaks differed considerably from sample to sample for all five bases, probably due to variation in the arrangement of the bases in the sublimed films. It was found also that the absorption spectra of the sublimed films change with aging on standing in vacuo at room temperature. On comparing the spectra of several fresh samples it was found that the intensities of the transitions with wavelength longer than 160 mμ of adenine, guanine, and uracil films are inversely correlated with those of the transitions shorter than 160mμ.

Vacuum ultraviolet absorption spectra of sublimed films of nucleic acid bases

Design of conjugated polymers with polaronic ferromagnetism

We develop a new general theory for large quantum fluctuations in a Fermion many·body system that cannot be described by fluctuations around the Hartree·Fock ground state but arises from resonance of different correlation structures. We start with an exact coherent state representation of a Fermion system on a unitary group. We show that the Hamiltonian in the coherent state representation has a close connection with the Hartree·Fock energy functional. From this, we can derive a new approximation called the resonating Hartree·Fock approximation in which a state is approximated by a superposition of non· orthogonal Slater deterrp.inants with different correlation structures. We derive the variation equations to determine a resonating Hartree· Fock wavefunction. We show that the resonance between degenerate broken symmetry Slater determinants may partially recover the symmetry. We discuss how to choose trial Slater determinants in a resonating Hartree· Fock wavefunction. We suggest that resonance of Slater determinants representing localized defects, such as solitons, polarons and breathers, produced in the long range order of the HF ground state may be the most important content of large quantum fluctuations in condensed matter systems.

/pdf/theory-of-resonating-quantum-fluctuations-in-a-fermion-4qhvo74qt2.pdf

Hideo Fukutome

Papers

Unrestricted Hartree–Fock theory and its applications to molecules and chemical reactions

A molecular-orbital theoretical classification of reactions of singlet ground-state molecules

Vacuum ultraviolet absorption spectra of sublimed films of nucleic acid bases

Design of conjugated polymers with polaronic ferromagnetism

Theory of Resonating Quantum Fluctuations in a Fermion System -- Resonating Hartree-Fock Approximation--