Preparation of cyclic polyphenylene array 2, which corresponds to a complete carbon array of a zigzag-type CNT segment with (18,0)-structure, has been established by a Diels-Alder reaction of cyclic biphenylylene-acetylene derivative 1 with tetraphenylcyclopentadienone. The reaction of 2 with excess FeCl3 realized a presumed cyclodehydrogenation reaction and elimination of the alkyl chains that were introduced as a measure to counter the low solubility problem, but this resulted in the formation of a complicated mixture that included the mass region of a presumed zigzag-type CNT segment with (18,0)-structure. The rather efficient blue emission of cyclic compounds 1 and 2 was discussed utilizing fluorescence (FL) quantum efficiencies (Φ(FL)) and lifetimes (τ(FL)) in their crystalline state along with those in dichloromethane solution. Thermal analyses of these compounds revealed their characteristic phase transition behavior. The synthesis of a novel cyclic polyphenylene array by utilizing a Diels-Alder reaction of cyclic phenylene-acetylene compounds with tetraphenylcyclopentadienone should afford an attractive pathway to a novel belt-shaped CNT segment.
Abstract The ene–diyne systems 1 and 2 , possessing ferrocenyl groups at the periphery, were prepared by a simple one‐pot Sonogashira–Hagihara coupling reaction of ethynylferrocene with 9‐dibromomethylene‐9 H ‐fluorene ( 4 ) and 9,10‐bis(dibromomethylene)‐9,10‐dihydroanthracene ( 5 ). Ene–diyne 1 reacted with tetracyanoethylene (TCNE) in a formal [2+2] cycloaddition reaction, followed by ring opening of the initially formed [2+2] cycloadduct, cyclobutene, to afford the corresponding 1,1,4,4‐tetracyanobutadiene (TCBD) derivative 6 in good yield. The redox behavior of the ene–diyne compounds 1 and 2 , and the TCBD derivative 6 was examined by cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which revealed their electrochemical oxidation properties with multi‐electron transfer depending on the number of ferrocene units in the molecule, in addition to the two‐electron reduction of the TCBD moiety in the case of TCBD derivative 6 . Moreover, a significant color change was observed by visible spectroscopy under electrochemical oxidation conditions and under reduction conditions in the case of TCBD derivative 6 .
class is a stable class, and we omit this class from further consideration.2) The case of $a=1/4$ (that is, the case of $ab=1$).Let $A_{0}=[0,3/4]$ and $A_{1}=[13/16,1]$ , then we have $f_{a,b}A_{0}=A_{1},$ $f_{a,b}A_{1}=$ $A_{0}$ , and $f_{a,b}^{4}|_{A_{i}}$ is the identity map on $A_{i}(i=0,1)$ and every orbit starting from $(3/4, 13/16)-\{4/5\}$ enters into $A_{0}\cup A_{1}$ .So, this class is also stable.3) $Thecaseofl/41,$ $(a+b-ab)/b\geqq b/(b+1)$ ).There exist a natural number $m$ and intervals $A_{0},$ $A_{1},$ $\cdots,$ $A_{2^{m}-1}$ such that $f_{a,b}A_{i}=A_{i+1}$ for $0\leqq i\leqq 2^{m}-2$ and $f_{a,b}A_{2^{m}-1}=A_{0}$ , and every orbit starting from $[0,1]-\bigcup_{i=0}^{2^{m}-1}A_{l}$ (except the fixed point of $f_{a,b}^{2^{m}}$ ) enters into
We previously reported that 2-aminotryptanthrin (T2NH2) and 2-(N,N-dimethylamino)tryptanthrin (T2NMe2) possess excellent photophysical properties such as wide-wavelength absorption and emission in the visible region and a high fluorescence quantum yield. These compounds also exhibit large positive fluorescent solvatochromism. In this study, the new derivative 2-(N,N-diphenylamino)tryptanthrin (T2NPh2) is synthesized, and its photophysical properties are investigated. In contrast to T2NH2 and T2NMe2, T2NPhe2 shows weak fluorescence only in nonpolar toluene and 1,4-dioxane among the 13 solvents of different polarity tested, which is considered to be due to thermal deactivation resulting from the promotion of internal conversion by the rotation of the phenyl groups. Although T2NPhe2 is nonfluorescent in tetrahydrofuran (THF), fluorescence is observed in water/THF solutions with more than 80 vol% water content as a result of aggregation-induced emission.
Abstract The reaction of 1-azulenecarbaldehydes 9a and b with pyrrole (8) in acetic acid resulted in decarbonylation to afford azulenes even at room temperature in 49 and 78% yields, respectively. 1,3-Azulenedicarbaldehydes also reacted with 8 to give azulenes in 36 and 52% yields, respectively. This decarbonylation reaction was adopted to the selective synthesis of 3,3′-unsubstituted di(1-azulenyl)methane derivatives 7a—d. Acid-catalyzed condensation of 9a and b with paraformaldehyde or benzaldehyde afforded 3,3′-methylenedi(1-azulenecarbaldehyde)s, following this decarbonylation reaction gave the desired 7a—d as a sole product in 33—59% yields starting from 9a and b. Such decarbonylation is because of the ability of protonation of azulene ring in acidic condition and because of electron-donating properties of pyrrole ring. This reaction would serve as a new strategy for the protection of 1- and/or 3-positions of azulene ring.
Tryptanthrin derivatives, which are known antimicrobial agents, were synthesized, and their absorption and fluorescence spectral behaviors were investigated. Our results showed that 2-aminotryptanthrin exhibits both a high fluorescence quantum yield and large positive fluorescent solvatochromism.
The following theorem was published in [2]. Theorem. There exists a constant δ > 0 such that for Lebesgue almost every (α, β) ∈ X = [0, 1] × [0, 1], there exists n o = n o (α, β) such that for any n > n o where the integers p n , q n , r n are provided by the modified Jacobi-Perron algorithm.
Preparation of 1-azulenyl ketones was achieved by metal-free hydration of 1-azulenylalkynes with trifluoroacetic acid in good to excellent yields. In the cases of the reaction of alkyne 1m, isocoumarin congener 4 was obtained in excellent yield.
Abstract The stable carbocation, tris(2-methyl-1-azulenyl)methyl hexafluorophosphate (4·PF6−) was prepared by a hydride-abstraction reaction of the corresponding methane derivative, tris(2-methyl-1-azulenyl)methane (5). The dynamic stereochemistry of 4 and 5 was studied based on the temperature-dependent 1H NMR spectra, which were analyzed by a flip mechanism; the steric effect of the three 2-methyl groups was also investigated by comparing it with that of the 3,3′,3″-trimethyl analogue, tris(3-methyl-1-azulenyl)methyl hexafluorophosphate (1b·PF6−). The threshold rotation mechanism for 4 was a two-ring flip, in contrast to a one-ring flip for 1b, and the activation energies for 4 (78.0 and 73.4 kJ mol−1) were higher than those for 1b due to increased crowding in the transition state for the rotation. Although the activation energies for 5 (49.9 and 43.2 kJ mol−1) were lower than those for 1b, the mechanism for 5 was also a two-ring flip. The mechanism was variable between one- and two-ring flip processes due to a steric effect of the three 2-methyl groups. These results indicate that a conjugative interaction between the central cation and the three azulene rings largely contribute to the transition state of the ring flipping as well as to the ground state.
