Hirotoshi Ito

Evaluation of molecular spin-orbit integrals by a gaussian expansion method

A method is presented for the evaluation of molecular multi-centre spin-orbit integrals of Coulomb, hybrid and exchange types using cartesian gaussian functions. It is shown that if gaussian bases are employed the spin-same-orbit integrals reduce to one-electron field integrals and the spin-other-orbit integrals to two-electron field integrals. The final formulae for these integrals are found to be convenient for computer programming. Some relationships among the nuclear attraction, the field and the field-gradient integrals as well as among the electronic repulsion, the two-electron field, and the zero-field splitting integrals are discussed in connection with the spin-orbit integrals. Some calculations are carried out for the radicals CH2 and NH.

UV absorption and circular dichroism calculations of three Drosophila virilis satellite DNA’s: Use of linear response polarizability theory

Assuming the Fano–DeVoe‐type of model Hamiltonian which is capable of involving usual cases of copolymer systems, the polymer polarizability tensor has been derived in terms of the electronic state wave functions for identical and nonidentical constituent monomers. A prescription is presented as to how to simply involve the polarizability tensors of sugar–phosphate residues into the total polymer polarizability tensor. Within the dipole–dipole approximation, a detailed computational procedure is given for obtaining the polymer polarizability tensor from monomer spectroscopic data. The calculations of UV and CD band shapes have been carried out on highly repeating DNA’s such as Drosophila virilis satellite DNA’s I, II, and III, i.e., poly[d(CAAACTA)]⋅poly[d(TAGTTTG)], poly[d(TAAACTA)]⋅poly[d(TAGTTTA)], and poly[d(CAAATTA)]⋅poly[d(TAATTTG)].

Bandshapes of electronic absorption spectra in molecular aggregates

Abstract Qualitative analyses of bandshapes of molecular aggregates are made in terms of hypochromism (or hyperchromism) taking account of the TRK sum rule. The linear response theory for vibronic systems is applied to the analyses for the sharp J-band and the bands of the DNA-dye complexes as examples. It is numerically checked that the sum rule is satisfied within the absorption region under consideration. It is also emphasized that a particular bandshape in the region of interest is governed by not only its neighboring electronic levels but also by higher electronic levels outside the absorption region - this fact being implicated by the TRK sum rule. Finally, an analytical relationship for the bandwidths of polymer vibronic bands which are to be determined entirely by intermolecular interaction is derived and discussed in connection with the damping parameters.

Equations‐of‐motion method for the spin–orbit coupling of aromatic molecules: Application to the phosphorescence lifetime of benzene

A phosphorescence theory for aromatic molecules is formulated in terms of the equations‐of‐motion method. The theory is applied to the INDO/S calculations on the lowest triplet radiative lifetime of benzene. All the calculations are performed within the spin‐same‐orbit interaction approximation. The random‐phase approximations are found to give better results than the Tamm–Dancoff approximation (or the singly excited CI). The importance of the spin‐other‐orbit interactions contributing to the phosphorescence lifetime is discussed from the formula derived in an Appendix.

Linear response Fano–DeVoe polarizability theory for biopolymers composed of chiral chromophores: Infinite order dipole–dipole approximation calculations of circular dichroism and ultraviolet band shapes of α‐helical and β‐pleated polypeptides

The first order dimer model made by Stiles and Buckingham for predicting optical activity has been extended up to an infinite order N‐mer model within the framework of the Fano–DeVoe type dipole approximation. The present formalism involves four mechanisms (1) the Kirkwood–Moffitt coupled oscillator mechanism through the Coulombic interactions; (2) the local asymmetric mechanism due to the intrinsic monomer optical activity; (3) the indirect electric–magnetic coupling mechanism through the Coulombic interactions; (4) the Condon, Alter, Eyring (CAE) direct electric–magnetic coupling mechanism through the electrostatic interactions between the upper to upper state transition moments on a certain site and the permanent dipole moments on the other sites. However, mechanism (4) must be excluded if we follow the Fano–DeVoe approximation, whereas it is indispensable for circular dichroism (CD) calculations of polypeptides to incorporate the CAE electric–magnetic coupling mechanism. This requirement is attained b...

Linear response polarizability theory of the ORD and the CD spectra of helical biopolymers

Abstract The linear response theory of configurationally induced optical rotation for helical biopolymers is formulated in terms of the molecular polarizability. Simple numerical computation of the ORD and the CD curves is carried out for the single-stranded polyadenylic acid having the configuration of DNA.

Evaluation of molecular integrals by gaussian expansion method with particular reference to zero-field splitting integrals

Abstract A new method is presented for deriving necessary molecular integrals of spin—orbit coupling and zero-field splitting integrals in benzene show that the contribution of the delta function integrals is large.

Polarizability tensor theory by Green’s function matrix: Circular dichroism and ultraviolet absorption band shape calculations of cyclo(Gly-Pro-Gly-D-Ala-Pro) having β- and γ-turns

In a recent paper, we represented the partial polymer polarizability tensor equation in terms of partial monomer polarizability tensors and intermonomer unit dipole–dipole interaction tensors. Here, we represent the same equation in terms of a partial polymer Green’s function matrix equation being constructed from partial monomer Green’s matrix elements and intermonomer interaction energies. We also show that the circular dichroism (CD) and ultraviolet (UV) absorption band shape functions bear a strong resemblance to DeVoe’s scalar representation of the band shape functions, which we have rewritten, using our terminology, in terms of the three terms describing the dipole–dipole coupling, the electromagnetic coupling, and the intrinsic optical activity. The latter is capable of incorporating the one-electron mechanism. The present tensor theory offers five advantages. First, for describing physical phenomena, the tensor form may be more convenient than the scalar forms. Second, in both the partial polariza...

CD and UV absorption bandshapes of DNA—acridine orange complexes: Influence of the interactions of purine—pyrimidine base pairs with dyes in intercalated model complexes

Abstract Induced CD and UV absorption spectral bandshapes of DNA—acridine orange (AO) complexes have been calculated for a model in which DNA intercalates one AO dye between every other base pair ( P/D =4), using the linear response polarizability theory of copolymer systems. The spectra show a strong dependence on the intercalated positions and the orientational angles of the AO dyes in the DNA pocket. The base pair sequence effect in the bandshapes which reflects the interaction of AOs with the DNA bases can clearly be observed, particularly in the ultraviolet region. It is necessary to take into account the interactions of DNA bases with AOs in electronic excited states in order to calculate reliable induced CD and UV absorption spectral bandshapes.

POLARIZABILITY TENSOR THEORY BASED UPON A BAYLEY-NIELSEN-SCHELLMAN-TYPE MODEL HAMILTONIAN : CIRCULAR DICHROISM CALCULATIONS OF POLYPEPTIDES

In our previous article based upon the usual Fano–DeVoe model Hamiltonian, the partial polymer polarizability tensor equation for describing visible and ultraviolet (VIS/UV) absorption and circular dichroism (CD) spectra was represented in terms of transition moments and a partial polymer Green’s function matrix equation, which is constructed from partial monomer Green’s matrix elements and inter(sub)molecular interaction energies. Here, on the basis of the extended Fano–DeVoe model Hamiltonian similar to the Bayley–Nielsen–Schellman secular Hamiltonian matrix, we represent a partial polymer polarizability tensor matrix equation in terms of transition moments and a partial polymer Green’s function matrix equation, which is constructed from partial monomer Green’s matrix elements, inter(sub)molecular interaction energies, and inter(sub)molecular electrostatic interaction energies. The last ones are newly taken into account. Computing the amide monomer spectroscopic parameters by the CNDO/S method and subst...