Changes in the Electronic Transitions of Polyethylene Glycol upon the Formation of a Coordinate Bond with Li⁺, Studied by ATR Far-Ultraviolet Spectroscopy

This study investigates the electronic transitions of complexes of lithium with polyethylene glycol (PEG) by the absorption bands of solvent molecules via attenuated total reflectance spectroscopy in the far-UV region (ATR–FUV). Alkali-metal complexes are interesting materials because of their functional characteristics such as good ionic conductivity. These complexes are used as polymer electrolytes for Li batteries and as one of the new types of room-temperature ionic liquids, termed solvation ionic liquids. Considering these applications, alkali-metal complexes have been studied mainly for their electrochemical characteristics; there is no fundamental study providing a clear understanding of electronic states in terms of electronic structures for the ground and excitation states near the highest occupied molecular orbital–lowest occupied molecular orbital transitions. This study explores the electronic transitions of ligand molecules in alkali-metal complexes. In the ATR–FUV spectra of the Li–PEG complex, a decrease in intensity and a large blue shift (over 4 nm) were observed to result from an increase in the concentration of Li salts. This observation suggests the formation of a complex, with coordinate bonding between Li+ and the O atoms in PEG. Comparison of the experimental spectrum with a simulated spectrum of the Li–PEG complex calculated by time-dependent density functional theory indicated that changes in the intensities and peak positions of bands at approximately 155 and 177 nm (pure PEG shows bands at 155, 163, and 177 nm) are due to the formation of coordinate bonding between Li+ and the O atoms in the ether molecule. The intensity of the 177 nm band depends on the number of residual free O atoms in the ether, and the peak wavelength at approximately 177 nm changes with the expansion of the electron clouds of PEG. We assign a band in the 145–155 nm region to the alkali-metal complex because we observed a new band at approximately 150 nm in the ATR–FUV spectra of very highly concentrated binary mixtures

Binding Motif of Terminal Alkynes on Gold Clusters

Gold clusters protected by terminal alkynes (1-octyne (OC-H), phenylacetylene (PA-H) and 9-ethynyl-phenanthrene (EPT-H)) were prepared by the ligand exchange of small (diameter <2 nm) Au clusters stabilized by polyvinylpyrrolidone. The bonding motif of these alkynes on Au clusters was investigated using various spectroscopic methods. FTIR and Raman spectroscopy revealed that terminal hydrogen is lost during the ligand exchange and that the CC bond of the alkynyl group is weakened upon attachment to the Au clusters. Acidification of the water phase after the ligand exchange indicated that the ligation of alkynyl groups to the Au clusters proceeds via deprotonation of the alkynes. A series of precisely defined Au clusters, Au₃₄(PA)₁₆, Au₅₄(PA)₂₆, Au₃₀(EPT)₁₃, Au₃₅(EPT)₁₈, and Au_41–43(EPT)_21–23, were synthesized and characterized in detail to obtain further insight into the interfacial structures. Careful mass analysis confirmed the ligation of the alkynes in the dehydrogenated form. An upright configuration of the alkynes on Au clusters was suggested from the Au to alkyne ratios and photoluminescence from the excimer of the EPT ligands. EXAFS analysis implied that the alkynyl carbon is bound to bridged or hollow sites on the cluster surface

Generation and Characterization of Highly Strained Dibenzotetrakisdehydro[12]annulene

We report here the generation of tetrakisdehydro[12]annulene possessing a highly deformed triyne component from the [4.3.2]propellatriene-annelated precursor by its photolysis extruding indan and the characterization of the highly reactive annulene by chemical and spectroscopic methods. In addition to the chemical evidence for the formation of the title compound in solution such as interception as a Diels−Alder adduct, we succeeded in its characterization by UV−vis and FTIR spectra in an argon matrix at 20 K. The experimental IR spectrum agreed well with the theoretical one calculated by the DFT method

[16.16.16](1,3,5)Cyclophanetetracosayne (C₆₀H₆): A Precursor to C₆₀ Fullerene

[16.16.16](1,3,5)Cyclophanetetracosayne (C60H6):  A Precursor to C60 Fulleren

A New Entry into Cyclo[<i>n</i>]carbons: [2 + 2] Cycloreversion of Propellane-Annelated Dehydroannulenes

A New Entry into Cyclo[n]carbons:  [2 + 2] Cycloreversion of Propellane-Annelated Dehydroannulene

Generation and Characterization of Highly Strained Dibenzotetrakisdehydro[12]annulene

We report here the generation of tetrakisdehydro[12]annulene possessing a highly deformed triyne component from the [4.3.2]propellatriene-annelated precursor by its photolysis extruding indan and the characterization of the highly reactive annulene by chemical and spectroscopic methods. In addition to the chemical evidence for the formation of the title compound in solution such as interception as a Diels−Alder adduct, we succeeded in its characterization by UV−vis and FTIR spectra in an argon matrix at 20 K. The experimental IR spectrum agreed well with the theoretical one calculated by the DFT method

A New Entry into Cyclo[<i>n</i>]carbons: [2 + 2] Cycloreversion of Propellane-Annelated Dehydroannulenes

A New Entry into Cyclo[n]carbons:  [2 + 2] Cycloreversion of Propellane-Annelated Dehydroannulene

Generation and Characterization of Highly Strained Dibenzotetrakisdehydro[12]- and Dibenzopentakisdehydro[14]annulenes

To generate dibenzotetrakisdehydro[12]- and dibenzopentakisdehydro[14]annulenes ([12]- and [14]DBAs) having a highly deformed triyne moiety, [4.3.2]propellatriene-anneleted dehydro[12]- and dehydro[14]annulenes were prepared as their precursors. UV irradiation of the precursors resulted in the photochemical [2 + 2] cycloreversion to generate the strained [12]- and [14]DBAs, respectively. The [12]DBA was not detected by 1H NMR spectroscopy, but it was intercepted as Diels−Alder adducts in solution, suggesting its intermediacy. Its spectroscopic characterization was successfully carried out by UV−vis spectroscopy in a 2-methyltetrahydrofuran (MTHF) glass matrix at 77 K and by FT-IR spectroscopy in an argon matrix at 20 K. On the other hand, the [14]DBA was stable enough for observation by 1H and 13C NMR spectra in solution, though it was not isolated because of the low efficiency of the cycloreversion. The [14]DBA was also characterized by interception as Diels−Alder adducts in solution and by UV−vis spectroscopy in a MTHF glass matrix at 77 K. The kinetic stabilities of the DBAs are compared with the related dehydrobenzoannulenes with respect to the topology of the π-systems. In addition, the tropicity of the [14]DBA is discussed based on its experimental and theoretical 1H NMR chemical shifts

Generation and Characterization of Highly Strained Dibenzotetrakisdehydro[12]- and Dibenzopentakisdehydro[14]annulenes

To generate dibenzotetrakisdehydro[12]- and dibenzopentakisdehydro[14]annulenes ([12]- and [14]DBAs) having a highly deformed triyne moiety, [4.3.2]propellatriene-anneleted dehydro[12]- and dehydro[14]annulenes were prepared as their precursors. UV irradiation of the precursors resulted in the photochemical [2 + 2] cycloreversion to generate the strained [12]- and [14]DBAs, respectively. The [12]DBA was not detected by 1H NMR spectroscopy, but it was intercepted as Diels−Alder adducts in solution, suggesting its intermediacy. Its spectroscopic characterization was successfully carried out by UV−vis spectroscopy in a 2-methyltetrahydrofuran (MTHF) glass matrix at 77 K and by FT-IR spectroscopy in an argon matrix at 20 K. On the other hand, the [14]DBA was stable enough for observation by 1H and 13C NMR spectra in solution, though it was not isolated because of the low efficiency of the cycloreversion. The [14]DBA was also characterized by interception as Diels−Alder adducts in solution and by UV−vis spectroscopy in a MTHF glass matrix at 77 K. The kinetic stabilities of the DBAs are compared with the related dehydrobenzoannulenes with respect to the topology of the π-systems. In addition, the tropicity of the [14]DBA is discussed based on its experimental and theoretical 1H NMR chemical shifts

Generation and Characterization of Highly Strained Dibenzotetrakisdehydro[12]- and Dibenzopentakisdehydro[14]annulenes

To generate dibenzotetrakisdehydro[12]- and dibenzopentakisdehydro[14]annulenes ([12]- and [14]DBAs) having a highly deformed triyne moiety, [4.3.2]propellatriene-anneleted dehydro[12]- and dehydro[14]annulenes were prepared as their precursors. UV irradiation of the precursors resulted in the photochemical [2 + 2] cycloreversion to generate the strained [12]- and [14]DBAs, respectively. The [12]DBA was not detected by 1H NMR spectroscopy, but it was intercepted as Diels−Alder adducts in solution, suggesting its intermediacy. Its spectroscopic characterization was successfully carried out by UV−vis spectroscopy in a 2-methyltetrahydrofuran (MTHF) glass matrix at 77 K and by FT-IR spectroscopy in an argon matrix at 20 K. On the other hand, the [14]DBA was stable enough for observation by 1H and 13C NMR spectra in solution, though it was not isolated because of the low efficiency of the cycloreversion. The [14]DBA was also characterized by interception as Diels−Alder adducts in solution and by UV−vis spectroscopy in a MTHF glass matrix at 77 K. The kinetic stabilities of the DBAs are compared with the related dehydrobenzoannulenes with respect to the topology of the π-systems. In addition, the tropicity of the [14]DBA is discussed based on its experimental and theoretical 1H NMR chemical shifts