A new spin on an old system: The title neutral radicals have been synthesized and characterized for the first time. Thanks to two terminal methoxy groups and three tert‐butyl groups, the chiral ...radicals are configurationally and chemically stable. The three‐dimensional π‐electron network shows extensive spin delocalization, and the distinct CD properties are attributed to the chirality of the helicene unit (see picture).
A “heat- and mass-balance analysis” for a direct-methanol fuel cell (DMFC) system, accounting for actual experimental data and the heat- and mass transfer of the DMFC, is proposed to facilitate the ...usage of general spreadsheet software. The spreadsheet software enables the use of various functions on the data and visualizes the data using graphs. In addition, this application has a light computational load and is thus easy to implement in system control. The output of the analysis is the transfer of material and heat within the DMFC, as well as the heat balance and electrical efficiency of the DMFC. The analysis was verified using experimental data of the DMFC system, and the results of the verification indicated that the analysis could predict heat balance and system efficiency with accuracies of approximately 3.7 and 2.5 %, respectively. Further, the analysis was used to investigate the effect of stack temperature on the electrical efficiency of the system, and the results showed that the optimum stack temperature at a system power of 130 W was 60 °C and the electrical efficiency at that temperature was 21.8 % HHV.
A series of group 11 metal complexes coordinated by (nitronyl nitroxide)‐2‐ide radical anion NN‐M(dtpb) NN: nitronyl nitroxide; M: CuI, AgI, and AuI; dtpb: 1,2‐bis(di‐2‐tolylphosphanyl)benzene) was ...prepared. Their structures, electrochemical properties, and related theoretical calculations were investigated. The oxidation potential (Eox, V vs. Fc/Fc+) of the NN‐moiety in these radical‐metalloids significantly shifted to the negative direction in comparison to that of the unsubstituted nitronyl nitroxide (NN‐H, Eox = +0.38 V); this is strongly dependant on the metal ion (Eox = –0.37 V for M = CuI, –0.31 V for AgI, and –0.28 V for AuI). The Eox values correlated with the energy level of the HOMO (SOMO) and also with the natural atomic charge of the C2 carbon atom attached to the metal ion, indicating that the ionic character of the metal–C2–carbon bond is a key factor in controlling the oxidation potential of these radical metalloids.
Group 11 metal complexes coordinated by (nitronyl nitroxide)‐2‐ide radical anion NN‐M(dtpb) (NN: nitronyl nitroxide; M: CuI, AgI, and AuI; dtpb: 1,2‐bis(di‐2‐tolylphosphanyl)benzene) were prepared. The oxidation potential of the NN moiety (Eox, V vs. Fc/Fc+) was shown to be lowered as increasing the anionic charge on the C2 carbon atom.
The spin–spin and magnetic properties of two (nitronyl nitroxide)‐(di‐p‐anisylamine‐phenothiazine) diradical cation salts, (DAA‐PTZ)+‐NN⋅MBr4− (M=Ga, Fe), have been investigated. These ...diradical‐cation species were prepared by the cross‐coupling of iodophenothiazine DAA‐PTZ‐I with NN‐AuPPh3 followed by oxidation with the thianthrenium radical cation (TA+⋅MBr4−). These salts were found to be highly stable under aerobic conditions. For the GaBr4 salt, large ferromagnetic intramolecular and small antiferromagnetic intermolecular interactions (J1/kB=+320 K and J2/kB=−2 K, respectively) were observed. The magnetic property of the Fe3+ salt was analyzed by using a six‐spin model assuming identical intramolecular exchange interaction (J3/kB=+320 K) and the other exchange interactions (J4/kB=−7 K and J5/kB=−4 K). A significant color change was observed in the UV/Vis/NIR absorption spectra upon electrochemical oxidation of the doublet DAA‐PTZ‐NN to the triplet (DAA‐PTZ)+‐NN.
Magnetic radical cations. Two stable diradical‐cation salts, (DAA‐PTZ)+‐NN⋅MBr4− (M=Ga, Fe), have been prepared and investigated. Their magnetic properties are characterized by the following exchange interactions: For the Ga salt, J1/kB=+320 K (intramolecular) and J2/kB=−2 K (intermolecular) according to the dimer model, and for the Fe salt, J3/kB=+320 K (intramolecular), J4/kB=−7 K (intramolecular), and J5/kB=−4 K (intermolecular) according to the six‐spin model (see figure).
The synthesis of 1-halonaphthalenes by the Cu-catalyzed benzannulation reaction of 2-(phenylethynyl)benzaldehyde and alkynes in the presence of the halogen reagents such as NBS, NCS, and NIS, was ...developed. This protocol afforded various type of 1-halonaphthalenes in moderate to excellent yields and the cross coupling reactions of 1-bromo-2-phenylnaphthalene prepared by this method with various reagents occurred to give the corresponding 1,2-disubstituted naphthalenes.
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•A copper catalyzed benzannulation and halogenation is described.•One pot synthesis of 1-halonaphthalenes is developed.•Synthesis of various 1,2-disubstituted naphthalenes by cross coupling reactions from 1-halonaphthalenes is demonstrated.
► Photoinduced electron transfer in donor–acceptor arrays using PDI and BODIPY. ► Intersystem crossing routes in the PDI- and BODIPY-excited states. ► Fluorescence sensors using BODIPYs. ► Solar ...cells using PDIs and BODIPYs.
This review summarizes recent studies concerning photophysical processes of donor–acceptor arrays involving perylene diimides and boron-dipyrromethenes (BODIPYs), and discusses fundamental photophysical properties, electron transfer in donor–acceptor arrays in solution and in aggregate systems, and applications to solar cells and sensors in biological systems (for BODIPYs). These compounds are generally characterized as fluorescent dyes and exhibit poor efficiency in intersystem crossing in direct excitation. However, a few studies have reported that the intersystem crossing is strongly induced by the following methodologies: presence of heavy atoms including metal ions; presence of radical substituents; charge recombination of the generated charge separated states; and hyperfine interactions in long-separated radical pairs. These methodologies are useful to selectively generate locally excited triplet states or charge separated states with minimal loss of deactivation to the singlet ground states. In this review, these methodologies are also introduced and discussed.
One-pot synthesis of (nitronyl nitroxide)-gold(i)-phosphine (NN-Au-P) complexes has been developed using chloro(tetrahydrothiophene)gold(i), phosphine ligands, nitronyl nitroxide radicals, and sodium ...hydroxide. The NN-Au-P complexes can be easily handled because they were quite stable under aerated conditions in both solution and crystalline states. They showed weak absorption bands with vibrational structures in the 450-650 nm region. The oxidation potentials assigned to the NN moieties of NN-Au-P complexes with aromatic phosphines were observed around -0.1 V vs. Fc/Fc
(-0.11 V for NN-Au-1, -0.08 V for NN-Au-2, -0.13 V for NN-Au-5, and -0.07 V for NN-Au-6), somewhat lower than that of NN-Au-P complexes with aliphatic phosphines (-0.25 V for NN-Au-3 and -0.17 V for NN-Au-4).
The influence of diarylamino (Ar 2 N–) substituents on the oxidation potential of 3,7-bis(diarylamino)phenothiazines (Ar2N)2–PTZ ( 1a–f , a : carbazolyl; b : dihydrodibenzoazepinyl; c : ...dibenzoazepinyl; d : diphenylamino; e : phenothiazinyl; and f : phenoxazinyl) is investigated, where the Ar 2 N-substituent sequence a → f is aligned in the increasing order of their electron-donating ability. Interestingly, a different sequence of electron-donating ability for Ar 2 N-substituents was observed for the oxidation potentials of (Ar2N)2–PTZ : 1a ( E ox 1 = +0.35 V vs. Fc/Fc + ) > 1f (+0.30 V) > 1e (+0.15 V) > 1d (−0.05 V) > 1c (−0.19 V) > 1b (−0.22 V). The observed sequence can be explained by the stereoelectronic effect of the Ar 2 N-substituents to stabilize (Ar2N)2–PTZ˙+ . Clear-cut examples are observed in the crystal structure of 1c˙+ and 1e˙+ , for which coplanar conformation is observed between the PTZ˙ + -plane and the planes of the sp 2 -hybridized nitrogen atoms in Ar 2 N-substituents through a large conformational change during the oxidation process of (Ar2N)2–PTZ .
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