Polycyclic aromatic hydrocarbons (PAHs) are prominent lead structures for organic optoelectronic materials. This work describes the synthesis of three B,S-doped PAHs with heptacene-type scaffolds via nucleophilic aromatic substitution reactions between fluorinated arylborane precursors and 1,2-(Me3SiS)2C6H4/1,8-diazabicyclo[5.4.0]undec-7-ene (72–92% yield). All compounds contain tricoordinate B atoms at their 7,16-positions, kinetically protected by mesityl (Mes) substituents. PAHs 1/2 feature two/four S atoms at their 5,18-/5,9,14,18-positions; PAH 3 is a 6,8,15,17-tetrafluoro derivative of 2. For comparison, we also prepared the skewed naphtho[2,3-c]pentaphene-type isomer 4. The simultaneous presence of electron-accepting B atoms and electron-donating S atoms results in a redox-ambiphilic behavior; the radical cations [1 • ] + and [2 • ]+ were characterized by electron paramagnetic resonance spectroscopy. Several low-lying charge-transfer states exist, some of which (especially S-to-B and Mes-to-B transitions) compete on the excited-state potential-energy surface. Consistent with the calculated state characters and oscillator strengths, this competition results in a spread of fluorescence quantum yields (2–27%). The optoelectronic properties of 1 change drastically upon addition of Ag+ ions: while the color of 1 in CH2Cl2 changes bathochromically from yellow to red (λmax from 463 to 486 nm; −0.13 eV), the emission band shifts hypsochromically from 606 to 545 nm (+0.23 eV), and the fluorescence quantum yield increases from 12 to 43%. According to titration experiments, higher order adducts [Ag n 1 m ] n+ are formed. As a suitable system for modeling Ag+ complexation, our calculations predict a dimer structure (n = m = 2) with Ag2S4 core, approximately linear S–Ag–S fragments, and Ag–Ag interaction. The computed optoelectronic properties of [Ag2 1 2]2+ agree well with the experimentally observed ones.
A series of four mononuclear and one dinuclear ruthenium styryl complexes with redox active triarylmethylium ligands were prepared. All new compounds were characterized by NMR spectroscopy, MS spectrometry, cyclic voltammetry, and in various oxidation states by IR and UV/vis/NIR and EPR spectroscopy. The increase in conjugation length by the introduction of the vinyl ruthenium entity pushes the electronic absorption to low energy, almost into the near-infrared region. Electrochemical and spectroscopic properties are strongly influenced by the para substituents at the triarylmethylium ligands. The complexes were characterized in up to four different oxidation states up to the trication level and show pronounced electrochromism. The oxidized mixed-valent diruthenium complex 5 2+ shows a moderate degree of charge and spin delocalization over the styryl ruthenium sites.
We present two new donor-acceptor dyads composed of a polychlorotriphenylmethyl radical (PTM * ) as the acceptor (A) and bis(4-dimethylaminophenyl)(phenyl)amine (TPAN) or 2,2':6',2'':6'',6-trioxytriphenylamine (TOTA) as particularly electron-rich triarylamine (TAA) donors (D). We assessed their electrochemical properties and electronic structures by cyclic voltammetry, UV/vis/NIR spectroscopy, EPR spectroscopy and quantum chemical calculations. By establishing the spectroscopic fingerprints of the oxidized and reduced forms, we probe for the possible coexistence of a zwitterionic TAA + -PTM À valence tautomer (VT), besides neutral TAA-PTM * . UV/vis/NIR and EPR spectroscopic studies at variable temperature and in various solvents however provide no indication for such equilibria. Quantitative spin counting experiments by EPR spectroscopy and quantum chemical calculations indicate that the one-electron oxidized forms of these dyads possess an open-shell singlet ground state which is energetically slightly below the triplet state [a
We report on three new vinylruthenium−triarylamine (TA) conjugates with planarized TA substituents. The neutral, mono-, and dioxidized forms of the complexes were scrutinized by UV/vis/NIR, IR, and EPR spectroscopies as well as by quantum chemical calculations. By analyzing the intervalence charge-transfer (IVCT) transitions of the mixed-valent radical cations, we obtain information on the extent of electronic coupling between the chemically different redox sites. Completely delocalized Ru-MeTA + shows a vibrationally structured, nonsolvatochromic IVCT band. Decreased blueshifts of the indicative Ru(CO) stretching vibration during the first oxidation and larger A( 14 N) EPR hyperfine splitting constants in concert with smaller gvalues indicate enhanced TA contributions to the singly occupied molecular orbital of the other two complexes Ru-TOTA •+ and Ru-DOTA •+ and hence less symmetrical charge and spin density distributions. This is also reflected by the solvatochromism and the asymmetric shape of the IVCT band with a smaller bandwidth at the low-energy side. Temperature-dependent UV/vis/NIR spectroscopy of mixed-valent Ru-TOTA •+ and Ru-DOTA •+ revealed that the band skewing is due to the vibrational coupling of the IVCT transition to symmetrical vibrations, placing these radical cations near or at the class II/III borderline according to Robin and Day.
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