Tetraaza[1₄]- and Octaaza[1₈]paracyclophane: Synthesis and Characterization of Their Neutral and Cationic States

Two kinds of aza­[1_<i>n</i>]­paracyclophanes, tetraaza­[1₄]­paracyclophane (<b>P4</b>) and octaaza­[1₈]­paracyclophane (<b>P8</b>), were synthesized as the smallest and the largest monodisperse macrocyclic oligomers of polyaniline ever made. Herein we report the electronic nature of the cationic species of these two macrocycles with different ring size. By combining ESR spectroscopy and DFT calculations it was suggested that <b>P4</b>^·+ was classified as delocalized class III or poised on the class II/III borderline while <b>P8</b>^·+ was regarded as a localized class II mixed-valence system. We successfully isolated the dication of <b>P4</b> as a stable dicationic salt <b>P4</b>²⁺·2­[SbF₆]⁻, and the structure of <b>P4</b>²⁺ was determined by X-ray crystal analysis. Variable-temperature NMR measurements for <b>P4</b>²⁺·2­[SbF₆]⁻ unequivocally showed that <b>P4</b>²⁺ was a 22π electron system with a singlet ground state. The supercharged hexacation of <b>P8</b> was also isolated as <b>P8</b>⁶⁺·6­[SbCl₆]⁻, and X-ray crystal analysis revealed that <b>P8</b>⁶⁺ includes one SbCl₆^– anion in its macrocyclic cavity

Hash-Mark-Shaped Azaacene Tetramers with Axial Chirality

The tetramers of azapentacene derivatives with unique hash mark (#)-shaped structures were prepared in a quite facile manner. The #-shaped tetramers are optically active due to possessing extended biaryl skeletons, and the structure of the tetramer composed of four dihydrodiaza­pentacene (DHDAP) units (<b>1</b>) was investigated as the first example of this kind of molecule. The tetramer <b>1</b> showed characteristic chiroptical properties reflecting its orthogonally arranged quadruple DHDAP moieties, as well as redox activity. The solution of enantiopure <b>1</b> exhibited intense circularly polarized luminescence (CPL) with a dissymmetry factor of 2.5 × 10^–3. The absolute configuration of the enantiomers of <b>1</b> was experimentally determined by X-ray crystal analysis for the dication salt of the enantiomer of <b>1</b> with SbCl₆^– counterions. The solutions of enantiopure <b>1</b>²⁺·2­[SbCl₆^–] also showed NIR circular dichroism (CD) spectra over the entire range from visible to 1100 nm, enabling the modulation of the chiroptical properties by redox stimuli

Hash-Mark-Shaped Azaacene Tetramers with Axial Chirality

The tetramers of azapentacene derivatives with unique hash mark (#)-shaped structures were prepared in a quite facile manner. The #-shaped tetramers are optically active due to possessing extended biaryl skeletons, and the structure of the tetramer composed of four dihydrodiaza­pentacene (DHDAP) units (<b>1</b>) was investigated as the first example of this kind of molecule. The tetramer <b>1</b> showed characteristic chiroptical properties reflecting its orthogonally arranged quadruple DHDAP moieties, as well as redox activity. The solution of enantiopure <b>1</b> exhibited intense circularly polarized luminescence (CPL) with a dissymmetry factor of 2.5 × 10^–3. The absolute configuration of the enantiomers of <b>1</b> was experimentally determined by X-ray crystal analysis for the dication salt of the enantiomer of <b>1</b> with SbCl₆^– counterions. The solutions of enantiopure <b>1</b>²⁺·2­[SbCl₆^–] also showed NIR circular dichroism (CD) spectra over the entire range from visible to 1100 nm, enabling the modulation of the chiroptical properties by redox stimuli

Landscape of Charge Carrier Transport in Doped Poly(3-hexylthiophene): Noncontact Approach Using Ternary Combined Dielectric, Paramagnetic, and Optical Spectroscopies

We report on a comprehensive measurement system for mobility and energy states of charge carriers in matter under dynamic chemical doping. The temporal evolution of the iodine doping process of poly­(3-hexylthiophene) (P3HT) was monitored directly through electron paramagnetic resonance (EPR) and optical absorption spectroscopy, as well as differential electrical conductivity by the microwave conductivity measurement. The increase in conductivity was observed after the EPR intensity reached a maximum and declined thereafter, and the conductivity finally reached ∼80 S cm^–1. The carrier species changed from a paramagnetic polaron with an estimated mobility of μ_P+ ≈ 2 × 10^–3 cm² V^–1 s^–1 to an antiferromagnetic polaron pair with μ_PP+ ≈ 0.6 cm² V^–1 s^–1. The technique presented here can be a ubiquitous method for rapid and direct observation of charge carrier mobility and energy states in p-type semiconducting materials as a completely noncontact, experimental, and quantitative technique

Hash-Mark-Shaped Azaacene Tetramers with Axial Chirality

The tetramers of azapentacene derivatives with unique hash mark (#)-shaped structures were prepared in a quite facile manner. The #-shaped tetramers are optically active due to possessing extended biaryl skeletons, and the structure of the tetramer composed of four dihydrodiaza­pentacene (DHDAP) units (<b>1</b>) was investigated as the first example of this kind of molecule. The tetramer <b>1</b> showed characteristic chiroptical properties reflecting its orthogonally arranged quadruple DHDAP moieties, as well as redox activity. The solution of enantiopure <b>1</b> exhibited intense circularly polarized luminescence (CPL) with a dissymmetry factor of 2.5 × 10^–3. The absolute configuration of the enantiomers of <b>1</b> was experimentally determined by X-ray crystal analysis for the dication salt of the enantiomer of <b>1</b> with SbCl₆^– counterions. The solutions of enantiopure <b>1</b>²⁺·2­[SbCl₆^–] also showed NIR circular dichroism (CD) spectra over the entire range from visible to 1100 nm, enabling the modulation of the chiroptical properties by redox stimuli

Hash-Mark-Shaped Azaacene Tetramers with Axial Chirality

The tetramers of azapentacene derivatives with unique hash mark (#)-shaped structures were prepared in a quite facile manner. The #-shaped tetramers are optically active due to possessing extended biaryl skeletons, and the structure of the tetramer composed of four dihydrodiaza­pentacene (DHDAP) units (<b>1</b>) was investigated as the first example of this kind of molecule. The tetramer <b>1</b> showed characteristic chiroptical properties reflecting its orthogonally arranged quadruple DHDAP moieties, as well as redox activity. The solution of enantiopure <b>1</b> exhibited intense circularly polarized luminescence (CPL) with a dissymmetry factor of 2.5 × 10^–3. The absolute configuration of the enantiomers of <b>1</b> was experimentally determined by X-ray crystal analysis for the dication salt of the enantiomer of <b>1</b> with SbCl₆^– counterions. The solutions of enantiopure <b>1</b>²⁺·2­[SbCl₆^–] also showed NIR circular dichroism (CD) spectra over the entire range from visible to 1100 nm, enabling the modulation of the chiroptical properties by redox stimuli

Hash-Mark-Shaped Azaacene Tetramers with Axial Chirality

The tetramers of azapentacene derivatives with unique hash mark (#)-shaped structures were prepared in a quite facile manner. The #-shaped tetramers are optically active due to possessing extended biaryl skeletons, and the structure of the tetramer composed of four dihydrodiaza­pentacene (DHDAP) units (<b>1</b>) was investigated as the first example of this kind of molecule. The tetramer <b>1</b> showed characteristic chiroptical properties reflecting its orthogonally arranged quadruple DHDAP moieties, as well as redox activity. The solution of enantiopure <b>1</b> exhibited intense circularly polarized luminescence (CPL) with a dissymmetry factor of 2.5 × 10^–3. The absolute configuration of the enantiomers of <b>1</b> was experimentally determined by X-ray crystal analysis for the dication salt of the enantiomer of <b>1</b> with SbCl₆^– counterions. The solutions of enantiopure <b>1</b>²⁺·2­[SbCl₆^–] also showed NIR circular dichroism (CD) spectra over the entire range from visible to 1100 nm, enabling the modulation of the chiroptical properties by redox stimuli

Optical and Structural Properties of ESIPT Inspired HBT–Fluorene Molecular Aggregates and Liquid Crystals

In bulk materials, positional isomers not only help in understanding how slight difference in molecular structure alters the crystal packing and optical properties, but also play a key role in developing new type of materials for functional applications. A detailed study on the photophysical properties of fluorene–HBT positional isomers in solution and in the solid state providing a molecular level understanding of the factors which influence fluorescence behavior is reported. Two molecules <b>Ia</b> and <b>IIa</b> were synthesized by Suzuki coupling reaction and their photophysical properties were compared to positional isomers <b>Ib</b> and <b>IIb</b>. Crystal structure analyses and density functional theory (DFT) computation studies were performed to understand structure–properties relation and the results reveal that changing substitution pattern has a marked influence on their packing modes and luminescence properties. Strong noncovalent interactions (π–π) in the solid state hamper the excited state intramolecular proton transfer (ESIPT) process which causes fluorescence quenching in the solid state (<b>Ia</b> and <b>IIa</b> = Φ_f, 28–40%; <b>Ib</b> and <b>IIb</b> = Φ_f, 55–67%). Compounds show solvent–responsive and aggregation induced emission (AIE) properties. Bent structures of <b>Ia</b> with double and symmetric substitution of ESIPT motifs exhibit particularly unique condensed phase upon heating, confirmed as a nematic liquid crystalline phase, and this is the first report on the ESIPT and AIE active liquid crystalline materials with a banana-shaped molecule