Deuterium relaxation time ofα-d-tryptophan included in cyclodextrin host molecules

Deuterium relaxation times ofd- andl--d-tryptophan included in -cyclodextrin derivatives were directly measured by deuterium NMR spectroscopy. The results showed that the molecular motion of the tryptophan molecule was strongly restricted even in the cavity of unmodified -cyclodextrin and the additional recognition groupings — ammonium and carboxylate — on -cyclodextrin did not affect the molecular motion of tryptophan, though the association constants were significantly enhanced.Deceased on March 22, 1987.     

Electronic structures and charge-transfer spectra of tris[2.2.2]paraxylylene and related compounds

Electronic spectra of tris[2.2.2]paraxylylene (3°-PX) and some related compounds were measured in order to investigate the electronic interaction (pπ-pπ and pσ-pσ type) between “normal” (undistorted) benzene rings. 3°-PX showed a large hypochromic effect, i.e., its oscillator strength was observed to be 0·61 times of that of the corresponding linear polyparaxylylene. Charge-transfer (CT) spectra between these compounds and some electron acceptors were also studied. MO calculations (the VI/1, CNDO/2 and CI methods) were carried out in order to elucidate the electronic structure of 3°-PX and also the CT interactions between tetracyanoethylene and 3°-PX, benzene, toluene or p-xylene.     

Preparations and properties of pseudo-geminal ketones of tris-[2.2.2]- and tetrakis[2.2.2.2]parazylylene

Pseudo-geminal bridged ketones of tris[2.2.2]paraxylylene, 1, and of tetrakis[2.2.2.2]paraxylylene, 2, were prepared and their spectral properties were investigated in comparison with those of dibenzosuberone, 3. The CO stretching band of 1 was observed at abnormally high frequency region (by ca. 50 cm^?1) compared with that of 3, while that of 2 was at a position similar to that of 3. The electronic spectrum of 1 showed that 1 has enormous loss of conjugation due to lack of coplanarity between CO and aromatics. The chemical shift of H⁰, ortho to CO, of 1 also supported this structural characteristic.     

Charge-transfer absorption spectra between tetracyclo[3.2.0.02,7.04,6]heptane and π-type electron acceptors

Charge-transfer transition energies, association constants, and molar extinction coefficients of complexes between tetracyclo[3.2.0.0^2,7.0^4,6]heptane(quadricyclane) and olefine type or quinone type acceptors were measured in methylene chloride at 20°. An excellent linear relationship (r = 0·9938) with a slope of 0·96 was observed in plots of ν_max(CT) for a series of complexes of quadricyclane against ν_max(CT) for the corresponding complexes of N,N-dimethyl-aniline, indicating that quadricyclane forms electron donor-acceptor complexes of weak interactions. The first ionization potential, estimated from the hyperbolic relationship between the charge-transfer transition energy (E_CT) and the ionization potential, was an exceptionally low value (8·28–8·32 eV) for a saturated hydrocarbon and was indeed in the same order of magnitude with that of norbornadiene, which was well reproduced by EHM and MINDO/1 calculations applying Koopmans' theorem to the calculated HOMO energy.