Double Alkylene-Strapped Diphenylanthracene as a Photostable and Intense Solid-State Blue-Emitting Material

We report the synthesis and photochemical and photophysical properties of double alkylene-strapped 9,10-diphenylanthracene derivatives <b>3a</b>–<b>c</b> (<b>a</b>: C6 strap, <b>b</b>: C7 strap, <b>c</b>: C8 strap) in which the reactive central aromatic ring of the anthracene moiety is protected by the double alkylene straps. Thus, <b>3a</b>–<b>c</b> were much more resistant to photochemical reactions than the parent 9,10-diphenylanthracene (DPA). Furthermore, <b>3b</b> in C₆H₁₂ as well as in a cast film and the powder state showed the highest fluorescence quantum yields among <b>3a</b>, <b>3b</b>, quadruple triethylsilyl-protected DPA <b>4</b>, and DPA, wherein the C7 strap in <b>3b</b> effectively serves to block fluorescence self-quenching

Self-Assembled Molecular Gear: A 4:1 Complex of Rh(III)Cl Tetraarylporphyrin and Tetra(<i>p</i>‑pyridyl)cavitand

The components of a 4:1 mixture of Rh­(III)Cl tetrakis­(4-methyl­phenyl)­porphyrin <b>1</b> and a bowl-shaped tetra­(4-pyridyl)­cavitand <b>4</b> self-assemble into a 4:1 complex <b>1</b>₄•<b>4</b> via Rh–pyridyl axial coordination bonds. The single-crystal X-ray diffraction analysis and variable-temperature (VT) ¹H NMR study of <b>1</b>₄•<b>4</b> indicated that <b>1</b>₄•<b>4</b> behaves as a quadruple interlocking gear with an inner space, wherein (i) four subunits-<b>1</b> are gear wheels and four <i>p</i>-pyridyl groups in subunit-<b>4</b> are axes of gear wheels, (ii) one subunit-<b>1</b> and two adjacent subunits-<b>1</b> interlock with one another cooperatively, and (iii) four subunits-<b>1</b> in <b>1</b>₄•<b>4</b> rotate quickly at 298 K on the NMR time scale. Together, the extremely strong porphyrin-Rh–pyridyl axial coordination bond, the rigidity of the methylene-bridge cavitand as a scaffold of the pyridyl axes, and the cruciform arrangement of the interdigitating <i>p</i>-tolyl groups as the teeth moiety of the gear wheels in the assembling <b>1</b>₄-unit make <b>1</b>₄•<b>4</b> function as a quadruple interlocking gear in solution. The gear function of <b>1</b>₄•<b>4</b> was also supported by the rotation behaviors of other 4:1 complexes: <b>2</b>₄•<b>4</b> and <b>3</b>₄•<b>4</b> obtained from Rh­(III)Cl tetrakis­[4-(4-methyl­phenyl)­phenyl]­porphyrin <b>2</b> or Rh­(III)Cl tetrakis­(3,5-dialkoxy­phenyl)­porphyrin <b>3</b> and <b>4</b> also served as quadruple interlocking gears, whereas <b>1</b>₄•<b>5</b> obtained from <b>1</b> and tetrakis­[4-(4-pyridyl)­phenyl]­cavitand <b>5</b> did not behave as a gear. The results of activation parameters (Δ<i>H</i>^⧧, Δ<i>S</i>^⧧, and Δ<i>G</i>^⧧) obtained from Eyring plots based on line-shape analysis of the VT ¹H NMR spectra of <b>1</b>₄•<b>4</b>, <b>2</b>₄•<b>4</b>, and <b>3</b>₄•<b>4</b> also support the interlocking rotation (geared coupled rotation) mechanism

Double Alkylene-Strapped Diphenylanthracene as a Photostable and Intense Solid-State Blue-Emitting Material

We report the synthesis and photochemical and photophysical properties of double alkylene-strapped 9,10-diphenylanthracene derivatives <b>3a</b>–<b>c</b> (<b>a</b>: C6 strap, <b>b</b>: C7 strap, <b>c</b>: C8 strap) in which the reactive central aromatic ring of the anthracene moiety is protected by the double alkylene straps. Thus, <b>3a</b>–<b>c</b> were much more resistant to photochemical reactions than the parent 9,10-diphenylanthracene (DPA). Furthermore, <b>3b</b> in C₆H₁₂ as well as in a cast film and the powder state showed the highest fluorescence quantum yields among <b>3a</b>, <b>3b</b>, quadruple triethylsilyl-protected DPA <b>4</b>, and DPA, wherein the C7 strap in <b>3b</b> effectively serves to block fluorescence self-quenching

Double Alkylene-Strapped Diphenylanthracene as a Photostable and Intense Solid-State Blue-Emitting Material

We report the synthesis and photochemical and photophysical properties of double alkylene-strapped 9,10-diphenylanthracene derivatives <b>3a</b>–<b>c</b> (<b>a</b>: C6 strap, <b>b</b>: C7 strap, <b>c</b>: C8 strap) in which the reactive central aromatic ring of the anthracene moiety is protected by the double alkylene straps. Thus, <b>3a</b>–<b>c</b> were much more resistant to photochemical reactions than the parent 9,10-diphenylanthracene (DPA). Furthermore, <b>3b</b> in C₆H₁₂ as well as in a cast film and the powder state showed the highest fluorescence quantum yields among <b>3a</b>, <b>3b</b>, quadruple triethylsilyl-protected DPA <b>4</b>, and DPA, wherein the C7 strap in <b>3b</b> effectively serves to block fluorescence self-quenching

Double Alkylene-Strapped Diphenylanthracene as a Photostable and Intense Solid-State Blue-Emitting Material

We report the synthesis and photochemical and photophysical properties of double alkylene-strapped 9,10-diphenylanthracene derivatives <b>3a</b>–<b>c</b> (<b>a</b>: C6 strap, <b>b</b>: C7 strap, <b>c</b>: C8 strap) in which the reactive central aromatic ring of the anthracene moiety is protected by the double alkylene straps. Thus, <b>3a</b>–<b>c</b> were much more resistant to photochemical reactions than the parent 9,10-diphenylanthracene (DPA). Furthermore, <b>3b</b> in C₆H₁₂ as well as in a cast film and the powder state showed the highest fluorescence quantum yields among <b>3a</b>, <b>3b</b>, quadruple triethylsilyl-protected DPA <b>4</b>, and DPA, wherein the C7 strap in <b>3b</b> effectively serves to block fluorescence self-quenching

Double Alkylene-Strapped Diphenylanthracene as a Photostable and Intense Solid-State Blue-Emitting Material

We report the synthesis and photochemical and photophysical properties of double alkylene-strapped 9,10-diphenylanthracene derivatives <b>3a</b>–<b>c</b> (<b>a</b>: C6 strap, <b>b</b>: C7 strap, <b>c</b>: C8 strap) in which the reactive central aromatic ring of the anthracene moiety is protected by the double alkylene straps. Thus, <b>3a</b>–<b>c</b> were much more resistant to photochemical reactions than the parent 9,10-diphenylanthracene (DPA). Furthermore, <b>3b</b> in C₆H₁₂ as well as in a cast film and the powder state showed the highest fluorescence quantum yields among <b>3a</b>, <b>3b</b>, quadruple triethylsilyl-protected DPA <b>4</b>, and DPA, wherein the C7 strap in <b>3b</b> effectively serves to block fluorescence self-quenching

Stereospecific Synthesis of Tris-heteroleptic Tris-cyclometalated Iridium(III) Complexes via Different Heteroleptic Halogen-Bridged Iridium(III) Dimers and Their Photophysical Properties

Herein, we report on the stereospecific synthesis of two single isomers of tris-heteroleptic tris-cyclometalated iridium­(III) (Ir­(III)) complexes composed of three different nonsymmetric cyclometalating ligands via heteroleptic halogen-bridged Ir dimers [Ir­(tpy)­(F₂ppy)­(μ-Br)]₂ <b>17b</b> and [Ir­(mpiq)­(F₂ppy)­(μ-Br)]₂ <b>27b</b> (tpyH: (2-(4′-tolyl)­pyri­dine) and F₂ppyH: (2-(4′,6′-di­fluoro­phenyl)­pyridine), and mpiqH: (1-(4′-methyl­phenyl)­iso­quinoline)) prepared by Zn²⁺-promoted degradation of Ir­(tpy)₂­(F₂ppy) <b>21</b> and Ir­(mpiq)₂­(F₂ppy) <b>26</b>, as reported by us. Subsequently, <b>17b</b> and <b>27b</b> were converted to the tris-heteroleptic tris-cyclometalated Ir complexes Ir­(tpy)­(F₂ppy)­(mpiq) <b>25</b> consisting of tpy, F₂ppy, and mpiq, as confirmed by spectroscopic data and X-ray crystal structure analysis. The first important point in this work is the selective synthesis of specific isomers among eight possible stereoisomers of Ir complexes having the same combination of three cyclometalating ligands. Namely, two meridional forms of <b>25</b> were synthesized and isolated. The second finding is that the different stereoisomers of <b>25</b> have different stability. Finally, different stereoisomers exhibit different emission spectra. Namely, one of its stereoisomers <b>25a</b> exhibits a single broad emission from <i>ca</i>. 550 nm to <i>ca</i>. 650 nm (orange emission), while stereoisomer <b>25c</b> emits dual emission at <i>ca</i>. 509 nm and <i>ca</i>. 600 nm (pale pink emission), as supported by time-dependent density functional theory calculation. To the best of our knowledge, this is the first report of the selective and efficient synthesis of different stereoisomers of tris-heteroleptic tris-cyclometalated Ir­(III) complexes that have different stabilities and different photophysical properties

Pyrrole-Fused Azacoronene Family: The Influence of Replacement with Dialkoxybenzenes on the Optical and Electronic Properties in Neutral and Oxidized States

A novel pyrrole-fused azacoronene family was synthesized via oxidative cyclodehydrogenation of the corresponding hexaarylbenzenes as the key step, and the crystal structures of tetraazacoronene <b>3b</b> and triazacoronene <b>4a</b> were elucidated. The photophysical properties for neutral compounds <b>1</b>–<b>4</b> were investigated using steady-state UV–vis absorption/emission spectroscopy and time-resolved spectroscopy (emission spectra and lifetime measurements) at both room temperature and 77 K. The observation of both fluorescence and phosphorescence allowed us to estimate the small S₁–T₁ energy gap (Δ<i>E</i>_S–T) to be 0.35 eV (<b>1a</b>), 0.26 eV (<b>2a</b>), and 0.36 eV (<b>4a</b>). Similar to the case of previously reported hexapyrrolohexaazacoronene <b>1</b> (HPHAC), electrochemical oxidation revealed up to four reversible oxidation processes for all of the new compounds. The charge and spin delocalization properties of the series of azacoronene π-systems were examined using UV–vis–NIR absorption, ESR, and NMR spectroscopies for the chemically generated radical cations and dications. Combined with the theoretical calculations, the experimental results clearly demonstrated that the replacement of pyrrole rings with dialkoxybenzene plays a critical role in the electronic communication, where resonance structures significantly contribute to the thermodynamic stability of the cationic charges/spins and determine the spin multiplicities. For HPHAC <b>1</b> and pentaazacoronene <b>2</b>, the overall aromaticity predicted for closed-shell dications <b>1</b>^<b>2+</b> and <b>2</b>^<b>2+</b> was primarily based on the theoretical calculations, and the open-shell singlet biradical or triplet character was anticipated for tetraazacoronene <b>3</b>^<b>2+</b> and triazacoronene <b>4</b>^<b>2+</b> with the aid of theoretical calculations. These polycyclic aromatic hydrocarbons (PAHs) represent the first series of nitrogen-containing PAHs that can be multiply oxidized

Pyrrole-Fused Azacoronene Family: The Influence of Replacement with Dialkoxybenzenes on the Optical and Electronic Properties in Neutral and Oxidized States

A novel pyrrole-fused azacoronene family was synthesized via oxidative cyclodehydrogenation of the corresponding hexaarylbenzenes as the key step, and the crystal structures of tetraazacoronene <b>3b</b> and triazacoronene <b>4a</b> were elucidated. The photophysical properties for neutral compounds <b>1</b>–<b>4</b> were investigated using steady-state UV–vis absorption/emission spectroscopy and time-resolved spectroscopy (emission spectra and lifetime measurements) at both room temperature and 77 K. The observation of both fluorescence and phosphorescence allowed us to estimate the small S₁–T₁ energy gap (Δ<i>E</i>_S–T) to be 0.35 eV (<b>1a</b>), 0.26 eV (<b>2a</b>), and 0.36 eV (<b>4a</b>). Similar to the case of previously reported hexapyrrolohexaazacoronene <b>1</b> (HPHAC), electrochemical oxidation revealed up to four reversible oxidation processes for all of the new compounds. The charge and spin delocalization properties of the series of azacoronene π-systems were examined using UV–vis–NIR absorption, ESR, and NMR spectroscopies for the chemically generated radical cations and dications. Combined with the theoretical calculations, the experimental results clearly demonstrated that the replacement of pyrrole rings with dialkoxybenzene plays a critical role in the electronic communication, where resonance structures significantly contribute to the thermodynamic stability of the cationic charges/spins and determine the spin multiplicities. For HPHAC <b>1</b> and pentaazacoronene <b>2</b>, the overall aromaticity predicted for closed-shell dications <b>1</b>^<b>2+</b> and <b>2</b>^<b>2+</b> was primarily based on the theoretical calculations, and the open-shell singlet biradical or triplet character was anticipated for tetraazacoronene <b>3</b>^<b>2+</b> and triazacoronene <b>4</b>^<b>2+</b> with the aid of theoretical calculations. These polycyclic aromatic hydrocarbons (PAHs) represent the first series of nitrogen-containing PAHs that can be multiply oxidized

Pyrrole-Fused Azacoronene Family: The Influence of Replacement with Dialkoxybenzenes on the Optical and Electronic Properties in Neutral and Oxidized States

A novel pyrrole-fused azacoronene family was synthesized via oxidative cyclodehydrogenation of the corresponding hexaarylbenzenes as the key step, and the crystal structures of tetraazacoronene <b>3b</b> and triazacoronene <b>4a</b> were elucidated. The photophysical properties for neutral compounds <b>1</b>–<b>4</b> were investigated using steady-state UV–vis absorption/emission spectroscopy and time-resolved spectroscopy (emission spectra and lifetime measurements) at both room temperature and 77 K. The observation of both fluorescence and phosphorescence allowed us to estimate the small S₁–T₁ energy gap (Δ<i>E</i>_S–T) to be 0.35 eV (<b>1a</b>), 0.26 eV (<b>2a</b>), and 0.36 eV (<b>4a</b>). Similar to the case of previously reported hexapyrrolohexaazacoronene <b>1</b> (HPHAC), electrochemical oxidation revealed up to four reversible oxidation processes for all of the new compounds. The charge and spin delocalization properties of the series of azacoronene π-systems were examined using UV–vis–NIR absorption, ESR, and NMR spectroscopies for the chemically generated radical cations and dications. Combined with the theoretical calculations, the experimental results clearly demonstrated that the replacement of pyrrole rings with dialkoxybenzene plays a critical role in the electronic communication, where resonance structures significantly contribute to the thermodynamic stability of the cationic charges/spins and determine the spin multiplicities. For HPHAC <b>1</b> and pentaazacoronene <b>2</b>, the overall aromaticity predicted for closed-shell dications <b>1</b>^<b>2+</b> and <b>2</b>^<b>2+</b> was primarily based on the theoretical calculations, and the open-shell singlet biradical or triplet character was anticipated for tetraazacoronene <b>3</b>^<b>2+</b> and triazacoronene <b>4</b>^<b>2+</b> with the aid of theoretical calculations. These polycyclic aromatic hydrocarbons (PAHs) represent the first series of nitrogen-containing PAHs that can be multiply oxidized