Hideo Tomioka was born in Ise in 1941 and received his B.Sc. at Nagoya Institute of Technology. He obtained his Ph.D. from Nagoya University in 1969 and is now a Professor of Chemistry at Mie University. Current research interests in the Tomioka group include the study of neutral reactive species using spectroscopic and computational techniques coupled with traditional product analysis methods. When he is not discussing strategies to isolate triplet carbenes with co-workers in the laboratory, he can be found strolling along the beach of the Ise Bay in front of his office.

Most molecules are held together by covalent bonds-electron pairs jointly shared by the two atoms that are linked by the bond. Free radicals, in contrast, have at least one unpaired electron. In the case of carbon-based radicals, the carbon atom at the radical centre no longer makes four bonds with other atoms as it would do in its normal, tetravalent state. The presence of unpaired electrons renders such radicals highly reactive, so they normally occur only as transient intermediates during chemical reactions. But the discovery by Gomberg in 1900 of triphenylmethyl, the first relatively stable free radical containing a central trivalent carbon atom, illustrated that radicals with suitable geometrical and electronic structures can be stable. Compounds containing a divalent carbon atom that uses only two of its four valence electrons for bonding are usually less stable than Gomberg-type radicals with trivalent carbon. Although the role of these so-called carbenes in chemical reactions has long been postulated, they were unambiguously identified only in the 1950s. More recently, stable carbenes have been prepared, but the singlet state of these molecules, with the two nonbonding valence electrons paired, means that they are not radicals. Carbenes in the second possible electronic state, the triplet state, are radicals: the two nonbonding electrons have parallel spins and occupy different orbitals. Here we report the preparation and characterization of a triplet carbene, whose half-life of 19 minutes at room temperature shows it to be significantly more stable than previously observed triplet carbenes.

Photochromism of a series of 1 '-alkyl-3',3'-dimethyl-6-nitro-8-alkanoyloxymethylspiro(2~-l-benzopyran-2,2'-indoline) derivatives (SPs) having different lengths of their alkyl chains has been investigated in didodecyldimethylammonium chloride-clay matrices; stable H (parallel type) and J (head-to-tail type) aggregates of photo-merocyanines are formed when SPs containing an appropriate length of alkyl chains are irradiated.

Photolysis of diazomethylstannylene 2 (ArSn-C(N2)Si(i-Pr)3, Ar = C6H3-2,6-Tip2 (Tip = C6H2-2,4,6-(i-Pr)3)) generated formal stannaacetylene 1 as a reactive intermediate, which was evidenced by the formation of cyclic arylalkylstannylene 4 via an intramolecular carbene insertion to a CH bond of isopropyl groups. The structures of the compounds 2 and 4 were fully characterized by X-ray crystallography. Stannaacetylene 1 was directly observed by laser flash photolysis of 2; lambdamax = 355 nm, tau = 50 ms at room temperature. No triplet ESR signals were observed during the photolysis of 2 in 3-methylpentane glass matrix at 77 K, indicating the singlet nature of 1. Theoretical calculations for the parent stannaacetylene suggest that the stannaacetylene is characterized as a SnC triple-bonded compound with a significant contribution of stannylene-(doubly excited)carbene structure.