Photoluminescent diamino-substituted dinaphthopentalenes were synthesized successfully by the treatment of in situ prepared dinaphthocyclooctadiyne with lithium amide. This reaction involves a series of transformations including the nucleophilic addition of the lithium amide to a triple bond of the cyclooctadiyne moiety, transannulation, protonation of the resulting pentalene anion, and the nucleophilic substitution of the pentalene core with the lithium amide. In this procedure, a novel double amination step plays a key role. When the diamino-substituted dinaphthopentalenes were irradiated with UV light in toluene, fluorescence was observed at around 580 nm (ΦF < 0.03).

Herein, we report the syntheses of dibenzoheteroles, namely, heterofluorenes, containing four-coordinated group 13 elements (boron Bf; aluminum Alf; gallium Gaf; indium Inf) and the relationship between their structures and optical properties. The electronic states of the compounds were considered theoretically by the density functional theory (DFT) calculation. In particular, we focused on their emission behaviors and electronic structures in the excited states. Initially, we confirmed that Bf and Gaf showed high stability in water and air, while Alf and Inf were sensitive. The structures of heterofluorenes, involving the heavier elements in the 13th group, tend to form trigonal planar structures even in the presence of coordination by nitrogen. Next, in their emissions, larger contribution from the triplet excited states was observed in the heterofluorenes with heavier elements. The major emission of Inf at 77 K was attributed to phosphorescence. These phosphorescence properties can be explained by the heavy atom effect. In Gaf and Inf, their excited states were deactivated by vibrational relaxation in their triplet excited states at room temperature. In Bf, Alf and Gaf when adding B(C6F5)3, the emissions oriented from the triplet exciplex were observed. Time-dependent DFT (TD-DFT) calculations revealed that the optimized structure of Bf in the excited S1 state has a considerably different geometry from those of Alf and Gaf. Finally, we obtained the data that the B–N bond could be cleaved in the excited S1 of Bf according to the B–N bond length and bond order. As a result, the lower intensity of the emission of Bf was comparable to that of Alf. This bond cleavage could be caused by an increase of the anti-bonding property in the B–N bond in the Franck–Condon (FC) S1 state and by weak electrostatic interaction between boron and nitrogen atoms. In Alf and Gaf, although the anti-bonding character of the M–N bonds (M = Al or Ga) in the FC S1 states also increases, the M–N bonds survive because of their stronger electrostatic interaction. The subsequent stronger emission in Alf and Gaf could be observed by suppressing the molecular motion in the excited states.

Three kinds of para-phenylenediamine (PDA) derivatives bearing nitronyl nitroxide (NN) groups were prepared and characterized on the basis of the electrochemical, electron spin resonance (ESR) spectroscopic, absorption spectroscopic, and magnetic susceptibility measurements. It was clarified that the oxidation potential of the central PDA unit is strongly influenced by the numbers of substituted electron–withdrawing NN groups. In addition, the intervalence charge transfer in the central PDA unit was detected in the monocationic states of the PDAs with two NN groups, indicating the coexistence of the localized spins and the delocalized spin on theses molecules. Moreover, pulsed ESR measurements confirmed that the delocalized spin on the central PDA unit and the localized two spins on the NN groups were ferromagnetically coupled in the monocationic states.

A functionalized single-walled carbon nanotube (SWCNT) of a finite length with a ring-like hydrogenation around its surface is designed toward fabrication of a molecular field-effect transistor (FET) device. The molecular wire thus designed is equipped with a quantum dot inside, which is confirmed by theoretical analysis for electronic transport. In particular, the current-voltage (I–V) characteristics under influence of the gate voltage are discussed in detail.

Herein, we report the syntheses of dibenzoheteroles, namely, heterofluorenes, containing four-coordinated group 13 elements (boron Bf; aluminum Alf; gallium Gaf; indium Inf) and the relationship between their structures and optical properties. The electronic states of the compounds were considered theoretically by the density functional theory (DFT) calculation. In particular, we focused on their emission behaviors and electronic structures in the excited states. Initially, we confirmed that Bf and Gaf showed high stability in water and air, while Alf and Inf were sensitive. The structures of heterofluorenes, involving the heavier elements in the 13th group, tend to form trigonal planar structures even in the presence of coordination by nitrogen. Next, in their emissions, larger contribution from the triplet excited states was observed in the heterofluorenes with heavier elements. The major emission of Inf at 77 K was attributed to phosphorescence. These phosphorescence properties can be explained by the heavy atom effect. In Gaf and Inf, their excited states were deactivated by vibrational relaxation in their triplet excited states at room temperature. In Bf, Alf and Gaf when adding B(C6F5)3, the emissions oriented from the triplet exciplex were observed. Time-dependent DFT (TD-DFT) calculations revealed that the optimized structure of Bf in the excited S1 state has a considerably different geometry from those of Alf and Gaf. Finally, we obtained the data that the B–N bond could be cleaved in the excited S1 of Bf according to the B–N bond length and bond order. As a result, the lower intensity of the emission of Bf was comparable to that of Alf. This bond cleavage could be caused by an increase of the anti-bonding property in the B–N bond in the Franck–Condon (FC) S1 state and by weak electrostatic interaction between boron and nitrogen atoms. In Alf and Gaf, although the anti-bonding character of the M–N bonds (M = Al or Ga) in the FC S1 states also increases, the M–N bonds survive because of their stronger electrostatic interaction. The subsequent stronger emission in Alf and Gaf could be observed by suppressing the molecular motion in the excited states.