Report on the 28th symposium on heteroatom chemistry of the chemical society of Japan

The 28th domestic Symposium on Heteroatom Chemistry of the Chemical Society of Japan was held at Saitama Culture Center in Saitama during the period of December 12–14, and about 250 chemists from various academic institutes and industries took part in the symposium. There were four plenary lectures, 44 oral presentations, and 52 poster presentations. The present article describes abstracts of the plenary lectures and graphical abstracts of oral presentations. Titles of poster presentations are also given. © 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:1–12, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10073     

Structures and properties of two diastereomeric cyclic sulfites derived from cis‐3,4‐di‐tert‐butylthiolane‐3,4‐diol and thionyl chloride

cis‐3,4‐Di‐tert‐butylthiolane‐3,4‐diol ( 1 ) was treated with an equimolar amount of thionyl chloride in the presence of triethylamine or pyridine in several solvents of different polarity to furnish two diastereomeric sulfites 2a and 2b generally in excellent combined yields. Although 2a was consistently formed as the major diastereomer when pyridine was used as the base, 2a and 2b were formed in approximately equal amounts when triethylamine was used as the base in polar solvents. X‐ray crystallographic analyses revealed that the S O group of 2a is anti to the thiolane ring and that of 2b syn to the thiolane ring. Density functional theory calculations (B3LYP/6‐31G* level) revealed that 2a is less stable than 2b by 1.28 kcal mol⁻¹, although 2a was formed generally as the predominant diastereomer. Spectroscopic data of 2a and 2b are discussed with emphasis on comparison with those obtained by calculations. Treatment of 2a and 2b with m‐chloroperbenzoic acid resulted in the oxidation of the divalent sulfur atom of the thiolane ring and not the sulfite sulfur atom. The above oxidations took place exclusively at the syn‐side with respect to the tert‐butyl groups.© 2003 Wiley Periodicals, Inc. Heteroatom Chem 14:587–595, 2003; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/hc.10192     

Resonant electron impact excitation of highly charged Fe ions studied with a compact electron beam ion trap

We present extreme ultraviolet spectra of 3s3p–3s3d transitions in Fe¹⁴⁺ observed with a compact electron beam ion trap. The contributions of indirect excitation via a metastable state and resonant excitation are studied by observing the electron energy dependence of the spectra for the energy range of 60–210 eV. The results indicate that the 3s3d ¹D₂ level is directly excited from the 3s² ground state whereas the 3s3d ³D₃ level has a large contribution of the indirect excitation via the 3s3p ³P₂ metastable state. Comparisons with the theoretical excitation cross sections including MNn resonant excitations show good qualitative agreement with the experimental results for the electron energy dependent features.     

Helical Oligophenylene Linked with [2.2]Paracyclophane: Stereogenic π-Conjugated Dye for Highly Emissive Chiroptical Properties

A stereogenic π-system based on dimer ( 2 ) and trimer ( 3 ) of [2.2]paracyclophane (PC) and biphenyl was prepared and its structural, photophysical, and chiroptical properties were investigated. X-ray analysis revealed that the quaterphenyl moieties in 2 adopt a double helical structure anchoring [2.2]PC from both sides. Furthermore, 3 forms a isosceles triangle structure with a large chiral cavity. A homodesmotic reaction using DFT calculations revealed that 2 has a larger strain energy than 3 owing to its highly twisted phenylene linkers. Electronic and circular dichroic (CD) spectra were recorded in CH₂Cl₂ solution. The spectra of both 2 and 3 are similar, and their longest absorption band accompanying a remarkable Cotton effect is attributed to the transition from HOMO to LUMO, which is delocalized to the quaterphenyl moiety. These compounds exhibit fairly high fluorescence quantum yields (ϕ=0.70–0.83) and moderate dissymmetry factor (|g_CPL|=1.6×10⁻³) in circularly polarized luminescence (CPL).     

Small Figure-Eight Luminophores: Double-Twisted Tethered Cyclic Binaphthyls Boost Circularly Polarized Luminescence

Double-twisted cyclic binaphthyls, in which two naphthalenes are tethered by -O(CH₂)_nO- linkage (n=1–3), have been synthesized. X-ray analyses and DFT calculations revealed a tightly constrained stereogenic figure-eight geometry. Tethering of two naphthalenes by short linkage forces a small dihedral angle, and the cyclic binaphthyls with short tether (n=1, 2) exhibit remarkable boosting of the g_lum value (1.0–1.6×10⁻²) in circularly polarized luminescence (CPL) and unusual g_lum/g_abs ratios (0.93–1.3). These experimental high |g_lum| values are in accord with the results of excited state TD-DFT calculations, which show transannular interactions and that consequent extensive delocalization occurs throughout the figure-eight π-core. As a result, the present figure-eight luminophore promote the elongation of the magnetic transition dipole moment that results in significant increases in g_lum values.     

Reversible Multicolor Photochromism of Dihydroazulene Crystals

The photochemical conversion of 1,8a-dihydroazulene-1,1-dicarbonitrile (DHA) to vinylheptafulvene (VHF) is a positive T-type photoswitch that is well understood in solution, but has not been explored in the solid state. Upon excitation with UV light, DHA is converted into VHF in the solid state, with a distinct color change from yellow to deep-red, and retention of crystallinity. The structure of the ring-opened product was assigned to syn-VHF using variable-temperature infrared spectroscopy, and determined by X-ray photodiffraction in a crystal enriched with the product by two-photon excitation. A radical pathway becomes an observable photoreaction channel at low temperatures, and includes a strongly colored, short-lived diradical intermediate.