Hirohiko Houjou

We develop a hybrid quantum mechanical/molecular mechanical-configuration interaction (QM/MM-CI) method for calculating the absorption maxima of photoreceptor proteins such as bacteriorhodopsin. A unique point of our method, discriminating it from usual QM/MM methods, is that the ground-state electronic structure of the whole protein is first evaluated by a linear scaling-molecular orbital calculation. The resultant electronic distribution is utilized to construct a modified Fock matrix for subs

To elucidate the origin of the opsin shift of bacteriorhodopsin (bR), a self-consistent reaction field method combined with configuration interaction calculation is employed. In addition, the absorption maxima of all-trans-retinal and its Schiff bases are measured in a variety of aprotic solvents. It is shown that the calculation reproduces well the observed solvatochromic shifts. From regression analysis, we obtain an empirical relationship between the absorption maximum of protonated retinal S

Heterodinuclear complexes of a fully pi-conjugated salphen ligand were efficiently synthesized with arbitrary combinations of Ni(II), Cu(II), and Zn(II). The UV-vis spectra of the heterodinuclear complexes were approximately represented by a simple average of the spectra of the corresponding homodinuclear complexes. Systematic analysis of the spectra highlighted weak intracomplex interactions through the pi-conjugated system of the ligand.

A hydroxybenzaldehyde derivative which has isobutenyl linkage reacts with a variety of diamines to efficiently result in a 2∶2 macrocyclic compound.

We prepared and characterized a series of mono- and dicarbaldehydes of 2,6-dihydroxynaphthalene that bear potential resonance-assisted hydrogen bonding (RAHB) unit(s). X-ray crystal structures of selected compounds revealed that each salicylaldehyde moiety forms an intramolecular hydrogen bond and that the introduction of formyl groups into either the α- or β-position causes a considerable difference in geometry, which was interpretative from a conventional scheme of resonance hybrids including

Novel dinuclear complexes were synthesized through the self-assembly of macrocyclic Schiff base ligands and either nickel(II) or copper(II) ions. X-Ray structural analysis revealed that the complexes had either a double helix (twisted) structure in which each atom had a distorted square-planar coordination or a non-helical (parallel) structure in which the metals had octahedral coordination. The helical complexes were rather unusual in that their helicity originated not in the coordination centr

Stepwise condensation reactions of 2,6-dihydroxynaphthalene-1,5-dicarbaldehyde and a phenylenediamine with concomitant binding of metal ions afforded a trinuclear complex of a fully π-conjugated, fused salphen ligand. By changing the synthetic pathway, we obtained a series of homo- and heteronuclear complexes containing selected combinations of nickel(II) and zinc(II) ions. Comparison of the trinuclear complexes' spectroscopic features with those of analogous dinuclear complexes revealed that th

Single-crystal microscopic absorption spectroscopy was used to clarify the effect of a bulky substituent on the photochromic properties of salicylideneanilines. We discovered that 3,5-di-tert-butylsalicylideneaniline (1), exhibiting debatable chromic properties, had at least three crystalline polymorphs, α1, α1, and β. α1-1 is thermochromic from −75 to 45 °C and also photochromic, particularly from −75 to 0 °C; α2-1 is photochromic but considerably unstable and transforms into the β form; β-1 is

We synthesized two constitutionally isomeric bis(iminomethyl)-2,6-dihydroxynaphthalenes, namely, α,α-diimines 1 and β,β-diimines 2, which can be formally represented as fused salicylaldimines with resonance-assisted hydrogen-bonding sites. Spectroscopic data show that the OH/OH, NH/OH, and NH/NH forms of 1 were in equilibrium in solution and that the proportion of the NH-bearing tautomers increased as the solvent polarity increased. The UV spectra of thin solid films of 1 with various types of h

A new method is formulated for evaluating solvent effects on the absorption maxima of molecules. The method is based on a self-consistent reaction field polarizable continuum model (SCRF-PCM), coupled with the configuration interaction (CI) procedure. We propose a new scheme in which the polarization of solvent, induced by the excitation of a solute molecule, is partitioned into orientational and electronic contributions, and the exact expression of excitation energy is derived with nonspecific

Abstract A series of mono‐ and dinuclear zinc(II), copper(II), nickel(II), and iron(III) complexes of novel salphen ligands were synthesized and spectroscopically characterized. The mononuclear ligand (H 2 L 1 ) was synthesized from 2,6‐dihydroxynaphthalene‐1‐carbaldehyde and an o ‐phenylenediamine; the dinuclear ligand (H 4 L 2 ), which was not isolated, contains a 2,6‐dihydroxynaphthalene‐1,5‐dicarbaldimine linkage that enables extended π‐conjugation over two salphen units. Bymeans of a contro

A series of monodisperse colloidal microspheres has been fabricated by precipitation polymerization of imine chains and concomitant transition metal binding. The resulting metal‐bound polyimine microspheres (M‐PIMSs, M = Co, Ni, Cu, or Zn, see Figure, which shows Zn‐PIMSs) have characteristic diameters in the range from 0.5 to 1.4 μm, depending on the metal used, and are of interest for applications in photonic devices.

Abstract A new variety of salicylideneaniline derivatives were prepared from a substituted aniline and a bis(hydroxybenzaldehyde) which has been synthesized through a tandem Claisen rearrangement reaction. X-ray crystal structures were obtained for many of the products. With respect to the conformation of their isobutenylene chain, the crystal structures can be classified into three groups: i.e., skew–skew (I), syn–skew (II), and syn–syn (III) conformers. The 1H NMR spectra were significantly di

Novel π-conjugated compounds composed of fused salphen groups as a repeating unit, embedded with four or an indefinite number of zinc nuclei have been synthesized. The solid-state absorption spectra, IR spectra, and powder XRD patterns of these compounds are investigated and compared with those of analogous oligomers. The presumptive polymer contains at least five units of the salphen complex and its assembly is highly ordered in the solid state.