Tatsuya Tachikawa

Precise PPP molecular orbital calculations of excitation energies of polycyclic aromatic hydrocarbons. Part 5: Spectroactive portion of fluoranthene derivatives☆

Abstract For Pariser–Parr–Pople molecular orbital (PPP MO) calculations of the p -band of fluoranthene derivatives, the values of the spectrochemical softness (SCS) parameter k in a novel two centre electron repulsion integral new-γ were evaluated based on the spectroactive portion (SP) of a molecular framework. The SP was determined by the character of MO calculated by the HMO method with reference to the structural analysis by ab initio MO calculations with 6-31G* level. The calculated excitation energies of the p -band of fluoranthene derivatives using the new-γ including k values based on the SP reproduced accurately the observed ones.

Chirality induction in a dibenzo-30-crown-10 congener promoted by an ion-pair coordinated self-assembly

We report the first example of chirality induction in a large-sized crown ether congener with bis(arylthiourea) units, which serve as an anion binding site. The phenomenon arises via an achiral ion-pair coordinated self-assembly in which intermolecular head-to-tail hydrogen bonding interactions occur between the thiourea units in the solid state.

Blue light-emitting electroluminescent devices with 2,9-disubstituted 1,10-phenanthrolines

Abstract 2,9-Diphenyl-1,10-phenanthroline derivatives 1 and 2 , containing N,N -dimethylamino and tert-butyl groups at the p -positions of their phenyl units, respectively, were synthesized as the emitting materials for the electroluminescent (EL) devices. The emission band of the device containing 1 was observed at 485 nm, and that of 2 was at 460 nm. These emissions were visible under ordinary room lighting. The EL emission of the device containing 1 was identical to the photoluminescence but that of the device containing 2 was revealed to be the exciplex emission.

Precise PPP molecular orbital calculations of excitation energies of polycyclic aromatic hydrocarbons. Part 6. Spectrochemical atomic softness parameter

The excitation energies of the α-, β-, and p-bands of benzo-annelated polyacenes were estimated by the Pariser–Parr–Pople (PPP) molecular orbital calculation method using a novel concept for evaluating the two-centre electron repulsion integral, new-γA, in which the spectrochemical atomic softness (SCAS) parameter krA was taken into account. The value of krA was determined using the concept of the spectroactive portion (SP) and allotted to each carbon atom. The calculated results using new-γA were excellent for the simultaneous calculations of the p-, α- and β-bands of benzo-annelated polyacenes and were better than those obtained from the conventional N·M-γ or the usual new-γ. The C–C bond lengths calculated using new-γA reproduced quantitatively the observed values.

Practical PPP molecular orbital calculations of absorption maxima of quinones.Part 2. Evaluation of the spectrochemical softness based on the absolute hardness

Abstract The first absorption maxima of linear para acenoquinones (LPAs) were calculated by the Pariser–Parr–Pople molecular orbital (PPP MO) method using a novel, two-centre electron repulsion integral new-γ. The spectrochemical softness parameter k in the new-γ was evaluated from the absolute hardness, η PPP and η HMO , which were obtained by the PPP MO and the HMO level approximations, respectively. The first absorption maxima calculated using the new-γ with k obtained from η PPP are greatly improved to reproduce the observed values better than using the conventional Nishimoto·Mataga-γ function.

PPP Molecular Orbital Calculations of Polyenyl Cations and their Analogs using New-γ and Pseudo Atom Modeling

Abstract The first absorption bands of the tetramethyl polyenyl cations were calculated by the Pariser-Parr-Pople molecular orbital method. By considering the extraordinary hyperconjugation effect of methyl substituents and using the new-y, the calculated absorption wavelengths reproduce well the observed ones.

MS-Windows Application for a PPP Calculation using the Novel Two-Center Electron Repulsion Integral

Abstract The application of Windows 95/98/NT for PPP MO (Pariser-Parr-Pople molecular orbital) calculation was developed by using the Inprise C++ builder. The novel two-center electron repulsion integral (new-γ), the concept of spectrochemical softness parameter krs for PPP calculation, was introduced in this application. The user can perform quickly the modeling of π-conjugated compounds on a PC monitor and select many suitable parameters (for example, ionization potentials, resonance integrals etc.) for the PPP calculation. The SCF calculation was momentarily performed and oscillator strength and LCAO coefficients of HOMO, LUMO or others were displayed. The calculations gave satisfactory results for the prediction of the electronic absorption spectra of polycyclic aromatic hydrocarbons(PAHs), symmetric cyanins and so on.

X-Ray Crystallographic Analysis of the Endo-Peroxide of Anthra[1,9-b c:4,10-b′c′]Dichromene

Abstract X-ray crystallographic analysis of the single crystals of endo-peroxide of anthra[1,9-bc:4,10-b′c′]dichromene (1) has revealed the positions of singlet oxygen addition to 1. The sites of oxygen attack were 9- and 10-positions of anthracene moieties but not 1- and 4-positions, coincided with the prediction from the coefficients of highest occupied molecular orbital calculated by AM1 or PM3 method.