Facile synthesis of fulminene ([6]phenacene) was achieved through the Mallory reaction of 1-(1-naphthyl)-2-(1-phenanthryl)ethene or the 9-fluorenone-sensitized photo-ring-closure of 1-(1-naphthyl)-2-(1-phenanthryl)ethane. The electronic spectral properties of fulminene were investigated for the first time using photoluminescence as well as transient absorption spectroscopy. The spectral features were compared with those of a series of lower phenacene homologs such as phenanthrene ([3]phenacene), chrysene ([4]phenacene), and picene ([5]phenacene). For the [n]phenacene series, both the fluorescence and phosphorescence bands linearly red-shifted with an increase in the number of the benzene rings (n). Trends in the energy levels of the excited singlet (ES) and the triplet (ET) states were expressed as Es = −2.6n + 89.1 (kcal mol−1) and ET = −1.8n + 66.2 (kcal mol−1), respectively. In the case of fulminene, laser flash photolysis displayed a transient spectrum with an absorption maximum (λmaxT–T) at 675 nm, which was assigned as the triplet fulminene excited state. The λmaxT–T values for the [n]phenacene series showed a linear correlation as a function of the ring number n, given by an equation, λmaxT–T = 60n + 318 (nm).

A 3-trifluoroacetylaminophthalimide selectively distinguished LiI from other alkaline-metal iodides and lithium halides by a marked fluorescence colour change, from orange-yellow to sky-blue, subsequent to 254 nm photolysis.

The Cd(3P1)- and Hg(3P1)-photosensitized emissions of some secondary and tertiary alkyl- and silylamines have been investigated under conditions of steady illumination at 493 and 298 K, respectively. The emission bands were observed at around 440 nm in the cadmium-photosensitized reactions of these amines. In contrast, no appreciable emission bands were observed in the mercury-photosensitized reactions of these amines. However, upon addition of tert-butyl alcohol to the amine-mercury system, an emission band evolved at around 350 nm in the mercury-photosensitization. The peak-wavelengths for secondary and tertiary alkyl- and silylamines are slightly shorter than the values predicted from the correlations between the peak wavelength and the first ionization energy obtained in the cadmium- and mercury-photosensitized luminescence of ammonia and primary amines. The quenching efficiencies of the cadmium and mercury resonance lines by secondary alkyl- and silylamines are higher than those by tertiary alkyl- and silylamines. These observations suggest that the steric hindrance by the alkyl and silyl groups to the approach of the nitrogen atom in the amines to excited cadmium and mercury atoms seems to be an important factor for the stabilization of the exciplexes and the quenching of the resonance lines. The behavior of silylamines is similar to that of alkylamines in cadmium- and mercury-photosensitized reactions.Graphical abstractHighlight► Cd- and Hg-photosensitized emissions of alkyl- and silylamines were investigated. ► The emissions from Hg-exciplexes of silylamines were observed for the first time. ► The Cd- and Hg-amine exciplexes possessed charge-transfer character. ► Secondary amines quenched Cd and Hg emissions more effectively than tertiary amines. ► The substituents of amines sterically affect their approach to excited Cd and Hg atoms.

A facile formation of picene was achieved by photosensitization of 1,2-di(1-naphthyl)ethane using 9-fluorenone as a sensitizer. This sensitized photoreaction is the first photochemical cyclization of ethylene-bridged naphthalene moieties to afford the picene skeleton. 5,8-Dibromopicene, prepared by this procedure using 1,2-di[1-(4-bromonaphthyl)]ethane as the substrate, was readily converted to novel functionalized picenes by conventional substitution and cross-coupling reactions.

Phthalide derivatives incorporating mono- and di-picolylamino functionalities at the 6-position have been prepared as novel fluoroionophores and their fluorescence responses to metal cations have been investigated. These phthalides not only exhibited efficient fluorescence in an aqueous medium but also displayed fluorescence on–off response upon addition of transition-metal cations, namely Cu2+. The 6-aminophthalide fluorophore served as the core of the fluorescent probes although it has rarely been applied to a chemosensor. To the best of our knowledge, these modified phthalides are the first 6-aminophthalide-derived fluorometric probes for metal cations, namely Cu2+.

A 3-trifluoroacetylaminophthalimide selectively distinguished LiI from other alkaline-metal iodides and lithium halides by a marked fluorescence colour change, from orange-yellow to sky-blue, subsequent to 254 nm photolysis.