Hirohiko Houjou

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Although 2-(2'-hydroxyphenyl)imidazo[1,2-a]pyridine (HPIP) is only weakly fluorescent in solution, two of its crystal polymorphs in which molecules are packed as stacked pairs and in nearly coplanar conformation exhibit bright excited-state intramolecular proton transfer (ESIPT) luminescence of different colors (blue-green and yellow). In order to clarify(More)
Interaction force of chitin-binding domains (ChBD1 and ChBD2) from a thermostable chitinase onto chitin surface was directly measured by atomic force microscopy (AFM) in a buffer solution. In the force curve measurement, multiple pull-off events were observed for the AFM tips functionalized with either ChBD1 or ChBD2, whereas the AFM tips terminated with(More)
The intermolecular interaction energy of the model system of the water-crownophane complex was analyzed. The water molecule has four hydrogen bonds, with the two hydrogen-donating phenolic hydroxy groups and two hydrogen-accepting oxygen atoms of the poly-oxyethylene chain of the crownophane in the complex. The MP2/6-311G(2d,2p) level calculations of the(More)
We have formulated a procedure for evaluating the anisotropic stiffness of a molecular assembly. First, we show how to reduce the dimensions of the matrices that appear in a conventional Hessian analysis of mass-weighted coordination by using a 12-dimensional transverse-rotational basis set for expansion. This treatment yields matrix representations of the(More)
We investigated the mechanical nature of multiply hydrogen-bonded systems by means of ab initio quantum chemical calculations, and we derived a set of force constants to reproduce the anisotropic vibration modes of such systems. Twenty multiply hydrogen-bonded molecular dimers were selected for evaluation of the stiffness of their hydrogen bonds. By means(More)
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(More)
Here we improved our hybrid QM/MM methodology (Houjou et al. J Phys Chem B 2001, 105, 867) for evaluating the absorption maxima of photoreceptor proteins. The renewed method was applied to evaluation of the absorption maxima of several retinal proteins and photoactive yellow protein. The calculated absorption maxima were in good agreement with the(More)
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(More)
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(More)
We have developed a novel triphenylmethane-based hexanuclear zinc complex that exhibits peculiar photochemical and photophysical properties. Upon UV irradiation, the compound turned from colorless to reddish purple, while the color of emission turned from blue to red. The color change was attributed to an oxidation of the ligand part. It was suggested that(More)