Large Electronic Interaction Research Articles

Fused Aromatic and Antiaromatic Smaragdyrin Dimers

AbstractSingly‐linked aromatic [22]smaragdyrin BF2 complex dimer was synthesized by the reductive coupling of 16‐brominated [22]smaragdyrin BF2 complex, which was oxidized to a stable diradical with PbO2. As the first example of fused smaragdyrin dimer, a fused [22]smaragdyrin BF2 complex dimer was synthesized by the oxidation of a CuCl‐BF2 complex dimer with FeCl3 and subsequent reduction with NaBH4. After removal of the BF2 group, the singly‐linked and fused aromatic dimers were oxidized to the corresponding antiaromatic [20]smaragdyrin free base dimers. The first oxidation and reduction potentials of these dimers are split depending upon the intramolecular electronic interactions, which are larger for the fused dimers. Despite the large electronic interactions, the aromatic and antiaromatic characters are well preserved in the fused dimers.

Fused Aromatic and Antiaromatic Smaragdyrin Dimers.

Singly-linked aromatic [22]smaragdyrin BF2 complex dimer was synthesized by the reductive coupling of 16-brominated [22]smaragdyrin BF2 complex, which was oxidized to a stable diradical with PbO2. As the first example of fused smaragdyrin dimer, a fused [22]smaragdyrin BF2 complex dimer was synthesized by the oxidation of a CuCl-BF2 complex dimer with FeCl3 and subsequent reduction with NaBH4. After removal of the BF2 group, the singly-linked and fused aromatic dimers were oxidized to the corresponding antiaromatic [20]smaragdyrin free base dimers. The first oxidation and reduction potentials of these dimers are split depending upon the intramolecular electronic interactions, which are larger for the fused dimers. Despite the large electronic interactions, the aromatic and antiaromatic characters are well preserved in the fused dimers.

Meso-Nitro- and meso-Aminosubporphyrinatoboron(III)s and meso-to-meso Azosubporphyrinatoboron(III)s.

meso-Nitrosubporphyrinatoboron(III) was synthesized by nitration of meso-free subporphyrin with AgNO2 /I2 . The subsequent reduction with a combination of NaBH4 and Pd/C gave meso-aminosubporphyrinatoboron(III). meso-Nitro- and meso-amino-groups significantly influenced the electronic properties of subporphyrin, which has been confirmed by NMR and UV/Vis spectra, electrochemical analysis, and DFT calculations. Oxidation of meso-aminosubporphyrinatoboron(III)s with PbO2 cleanly gave meso-to-meso azosubporphyrinatoboron(III)s that exhibited almost coplanar conformations and large electronic interaction through the azo-bridge.

ChemInform Abstract: meso‐Free Corroles: Syntheses, Structures, Properties, and Chemical Reactivities.

5,10-Bis(pentafluorophenyl)corrole (5) and 5,15-bis(pentafluorophenyl)corrole (9) have been synthesized as meso-free corroles by rational synthetic routes. Both the structures of these corroles have been unambiguously revealed by X-ray diffraction analysis and their optical and electrochemical properties have been studied. Chlorination and oxidative dimerization of 5 and 9 have been explored, which revealed a marked different reactivity of the free meso-positions in 5 and 9. 10-Chlorinated corrole 11 was effectively prepared by the reaction of 9 with Palau‘chlor in the presence of 1 % pyridine whereas 5-chlorinated corrole 12 was obtained in a trace amount from similar chlorination of 5. 5,5′-Linked corrole dimer 13 was produced by reaction of 5 with AgNO2 in a good yield, whereas 10,10′-linked corrole dimer 14 was formed in a moderate yield by the reaction of 9 with [bis(trifluoroacetoxy)iodo]benzene. Observed large electronic interaction between the two corroles in 13 as compared with that in 14 has been ascribed mainly to conformational flexibility of the former, which allows more coplanar conformation.

Electric-Field-Driven Resistive Switching in the Dissipative Hubbard Model.

We study how strongly correlated electrons on a dissipative lattice evolve out of equilibrium under a constant electric field, focusing on the extent of the linear regime and hysteretic nonlinear effects at higher fields. We access the nonequilibrium steady states, nonperturbatively in both the field and the electronic interactions, by means of a nonequilibrium dynamical mean-field theory in the Coulomb gauge. The linear response regime, limited by Joule heating, breaks down at fields much smaller than the quasiparticle energy scale. For large electronic interactions, strong but experimentally accessible electric fields can induce a resistive switching by driving the strongly correlated metal into a Mott insulator. We predict a nonmonotonic upper switching field due to an interplay of particle renormalization and the field-driven temperature. Hysteretic I-V curves suggest that the nonequilibrium current is carried through a spatially inhomogeneous metal-insulator mixed state.

Meso-Free Corroles: Syntheses, Structures, Properties, and Chemical Reactivities.

5,10-Bis(pentafluorophenyl)corrole (5) and 5,15-bis(pentafluorophenyl)corrole (9) have been synthesized as meso-free corroles by rational synthetic routes. Both the structures of these corroles have been unambiguously revealed by X-ray diffraction analysis and their optical and electrochemical properties have been studied. Chlorination and oxidative dimerization of 5 and 9 have been explored, which revealed a marked different reactivity of the free meso-positions in 5 and 9. 10-Chlorinated corrole 11 was effectively prepared by the reaction of 9 with Palau'chlor in the presence of 1 % pyridine whereas 5-chlorinated corrole 12 was obtained in a trace amount from similar chlorination of 5. 5,5'-Linked corrole dimer 13 was produced by reaction of 5 with AgNO2 in a good yield, whereas 10,10'-linked corrole dimer 14 was formed in a moderate yield by the reaction of 9 with [bis(trifluoroacetoxy)iodo]benzene. Observed large electronic interaction between the two corroles in 13 as compared with that in 14 has been ascribed mainly to conformational flexibility of the former, which allows more coplanar conformation.

Synthesis of Direct β‐to‐β Linked Porphyrin Arrays with Large Electronic Interactions: Branched and Cyclic Oligomers

AbstractDirect β‐to‐β linked branched and cyclic porphyrin trimers and pentamers have been synthesized by the Suzuki–Miyaura coupling of β‐borylporphyrins and β‐bromoporphyrins. The cyclic porphyrin trimer, the smallest directly linked cyclic porphyrin wheel to date, and its twined pentamer, exhibit small electrochemical HOMO–LUMO gaps, broad nonsplit Soret bands, and red‐shifted Q‐bands, thus indicating large electronic interactions between the constituent porphyrin units.

Synthesis of direct β-to-β linked porphyrin arrays with large electronic interactions: branched and cyclic oligomers.

Direct β-to-β linked branched and cyclic porphyrin trimers and pentamers have been synthesized by the Suzuki-Miyaura coupling of β-borylporphyrins and β-bromoporphyrins. The cyclic porphyrin trimer, the smallest directly linked cyclic porphyrin wheel to date, and its twined pentamer, exhibit small electrochemical HOMO-LUMO gaps, broad nonsplit Soret bands, and red-shifted Q-bands, thus indicating large electronic interactions between the constituent porphyrin units.

Two-Photon Study on the Electronic Interactions between the First Excited Singlet States in Carotenoid−Tetrapyrrole Dyads

Electronic interactions between the first excited states (S(1)) of carotenoids (Car) of different conjugation lengths (8-11 double bonds) and phthalocyanines (Pc) in different Car-Pc dyad molecules were investigated by two-photon spectroscopy and compared with Car S(1)-chlorophyll (Chl) interactions in photosynthetic light harvesting complexes (LHCs). The observation of Chl/Pc fluorescence after selective two-photon excitation of the Car S(1) state allowed sensitive monitoring of the flow of energy between Car S(1) and Pc or Chl. It is found that two-photon excitation excites to about 80% to 100% exclusively the carotenoid state Car S(1) and that only a small fraction of direct tetrapyrrole two-photon excitation occurs. Amide-linked Car-Pc dyads in tetrahydrofuran demonstrate a molecular gear shift mechanism in that effective Car S(1) → Pc energy transfer is observed in a dyad with 9 double bonds in the carotenoid, whereas in similar dyads with 11 double bonds in the carotenoid, the Pc fluorescence is strongly quenched by Pc → Car S(1) energy transfer. In phenylamino-linked Car-Pc dyads in toluene extremely large electronic interactions between the Car S(1) state and Pc were observed, particularly in the case of a dyad in which the carotenoid contained 10 double bonds. This observation together with previous findings in the same system provides strong evidence for excitonic Car S(1)-Pc Q(y) interactions. Very similar results were observed with photosynthetic LHC II complexes in the past, supporting an important role of such interactions in photosynthetic down-regulation.

Effect of support on the activity of Ga 2O 3 species for steam reforming of dimethyl ether

The effects of various supports on the catalytic activity of Ga 2O 3 for the steam reforming of DME have been examined. Among the various supported Ga 2O 3 catalysts, Ga 2O 3/TiO 2 showed the highest DME steam reforming activity in terms of DME conversion and H 2 yield. The results from XRD, surface area and XPS indicate that the dispersion of Ga 2O 3 strongly depends on the catalyst support. A correlation between the XPS results and the DME steam reforming activity reveals that there is some electronic interaction between Ga 2O 3 and the support element. The large electronic interaction found in Ga 2O 3/TiO 2 leads to the best catalytic performance among all the catalysts.

Covalently linked pyropheophorbide dimers as models of the special pair in the photosynthetic reaction center

Covalently linked pyropheophorbide dimers were prepared by the condensation reactions 3-devinyl-3-carboxylpyropheophorbide-α. Among these, dimers bridged by 1,8-naphthalene spacers exhibit large electronic interactions in the 1H NMR and UV-visible spectra and in the redox potentials. In addition, a 1,8-naphthalene-bridged amide-linked dimer displays notable broadening and split CD effect in the Qy band as well as strong fluorescence quenching, being analogous to the special pair in the photosynthetic reaction center.

Oxygen-disorder and correlation effects on the hole concentration and metal-nonmetal transition in YBa2Cu3O6+x.

A detailed analysis of the effect that oxygen disorder has on the electronic structure of the highly correlated high-${\mathit{T}}_{\mathit{c}}$ superconductors is presented. The system is modeled by a Hubbard-type Hamiltonian in which the on-site and intersite correlations between oxygen and copper atoms are included. The Green-function formalism is used to calculate the local electronic density of states at the Cu and O sites characteristic of ${\mathrm{YBa}}_{2}$${\mathrm{Cu}}_{3}$${\mathrm{O}}_{6+\mathit{x}}$ as a function of oxygen concentration x and of the cation charge Q. Due to the large electronic interactions, a Mott-Anderson metal-nonmetal transition is obtained, in accordance with the experimental findings. The hole concentration n is calculated for disordered and ordered systems. A plateau in the concentration dependence of n is obtained for 0.45\ensuremath{\le}x\ensuremath{\le}0.75, only in the ordered system. The correlation functions of the various charge states in Cu and O are also calculated and discussed.