Establishing design principles to create nonplanar π-conjugated molecules is crucial for the development of novel functional materials. Herein, we describe the synthesis and properties of dinaphtho[1,8-bc:1′,8′-ef]azepine bisimides (DNABIs). Their molecular design is conceptually based on the insertion of a nitrogen atom into a perylene bisimide core. We have synthesized several DNABI derivatives with a hydrogen atom, a primary alkyl group, or an aryl group on the central nitrogen atom. These DNABIs exhibit nonplanar conformations, flexible structural changes, and ambipolar redox activity. The steric effect around the central nitrogen atom substantially affects the overall structures and results in two different conformations: a nonsymmetric bent conformation and a symmetric twisted conformation, accompanied by a drastic change in electronic properties. Notably, the nonsymmetric DNABI undergoes unique structural changes in response to the application of an external electric field, which is due to molecular motions that are accompanied by an orientational fluctuation of the dipole moment. Furthermore, the addition of a chiral Brønsted base to N-unsubstituted DNABI affords control over the helical chirality via hydrogen-bonding interactions.
Polar H 2 O molecules generally act as trapping sites and suppress the electron mobility of n-type organic semiconductors, making chemical design of H 2 O-tolerant and responsive n-type semiconductors an important step toward multifunctional electron−ion coupling devices. The introduction of effective electrostatic interactions between potassium ions (K + ) and carboxylate (−COO − ) anions into the electron-transporting naphthalenediimide πframework enables the design of high-performance H 2 O-tolerant n-type semiconductors with a reversible H 2 O adsorption−desorption ability, where the electron mobility and K + ionic conductivity were coupled with the reversible H 2 O sorption behavior. The reversible H 2 O adsorption into the crystals enhanced the electron mobility from 0.04 to 0.28 cm 2 V −1 s −1 , whereas the K + ionic conductivity decreased from 3.4 × 10 −5 to 4.7 × 10 −7 S cm −1 . Because this reversible electron−ion conducting switch is responsive to H 2 O sorption behavior, it is a strong candidate for H 2 O gating carrier transport systems.
Electrostatic cation–anion interaction is effective to form a tightly bounded π-molecular assembly, which enhances the thermal stability and carrier transport property. Dianionic bis(benzenesulfonate)–naphthalenediimide (BSNDI 2– ) formed simple 2:1 cation–anion pairs of (Na+)2(BSNDI 2– ) (1), (K+)2(BSNDI 2– ) (2), and (NH4 +)2(BSNDI 2– ) (3), and their redox behaviors, thermal stabilities, crystal structures, electron transport properties, and dielectric constants were compared to those of neutral bis(phenyl)–naphthalenediimide (4). Crystals 1, 2, and 3 had quite high thermal stabilities up to 850, 810, and 600 K, respectively, even though organic molecules. A two-dimensional (2D) n-type electron transport layer consisting of NDI π cores was sandwiched between networks of highly polarized electrostatic cation–anion pairs showing 2D herringbone (1), one-dimensional π-stacking (2), and brickstone-like 2D π-stacking (3) interactions. The values of electron mobility in polycrystalline 1, 2, 3, and 4 reached 0.22, >0.0003, 0.036, and >0.028 cm2 V–1 s–1, respectively, according to flash-photolysis time-resolved microwave conductivity measurements. The electron mobility of crystal 1 was 1 order of magnitude higher than those of crystals 2, 3, and 4 owing to the tight intermolecular interactions within the 2D transport layer. The real part dielectric constants of crystals 1, 2, 3, and 4 were ∼4, ∼50, ∼20, and ∼4 at 450 K, respectively, which affected the electron transport property. The chemical design of highly polarized electrostatic cation–anion pair formed the 2D transport layer and also has high thermal stability up to ∼850 K in the ionic n-type semiconducting materials.
Hydrophilic fullerene derivatives of C60(OH)12 (1) and C60(OH)36 (2) bearing different numbers of-OH groups formed amorphous solids of 1•x(H2O) (x = 5-10) and 2•x(H2O) (x = 15-22), respectively, according to the humidity. The thermally activated dynamic molecular motion of polar H2O was confirmed in the DSC and dielectric spectra. Three-dimensional O-H•••O hydrogen-bonding networks in amorphous 1 and 2 produced extrinsic adsorption-desorption pores with a hydrophilic environment posed by-OH groups, where N2, CO2, H2, and CH4 gases vapors and polar H2O, MeOH, and EtOH molecules reversibly adsorbed into the networks. Molecular motion of polar H2O was directly observed in dielectric enhancement and protonic conductivity in three-dimensional O-H•••O hydrogen-bonding networks. The Brunauer-Emmett-Teller (BET) specific surface areas of amorphous 1 and 2 were 315 and 351 m 2 g-1 , respectively, from the CO2 sorption isotherms. Reversible vapor sorption behaviors with structural changes of amorphous 1 and 2 were also confirmed for the polar H2O, MeOH, and EtOH.
which exhibited reversible H 2 O adsorption−desorption behavior because of the presence of their electrostatically binding crystal lattices. The maximum H 2 O adsorption amounts (n) for M + = Li + , Na + , K + , Rb + , and Cs + were 0.25, 6.0, 4.0, 6.0, and 2.0, respectively, whereas the reversible gate-opening (gateclosing) H 2 O adsorption−desorption isotherms were observed at 273 and 298 K, except for M + = Li + . High ionic conductivities of around 10 −4 −10 −5 S cm −1 were observed in M + = Na + and K + salts, whereas short-range thermal fluctuations occurred in large cations of M + = Rb + and Cs + . The change in the electrostatic lattice energy for M + = Na + and K + salts during the H 2 O adsorption−desorption cycles was significantly larger than those for M + = Rb + and Cs + . Therefore, the Na + and K + salts had a considerably flexible electrostatic crystal lattice with a large amplitude of lattice modulation during the H 2 O sorption cycle. In contrast, the lattice modulation for M + = Rb + and Cs + salts involved a low magnitude of ion displacements, forming a relatively rigid cation−anion electrostatic crystal lattice. The flash-photolysis time-resolved microwave conductivity and transition absorption spectroscopy results revealed the high electron mobility of H 2 O-adsorbed thin films, wherein the crystallized H 2 O molecules did not act as electron-trapping sites. The values of electron mobility increased in the order of Cs
Polyrotaxane networks (PRNs) were synthesized by exploiting a Pd-templated bis-macrocycle as a topological cross-linker during radical polymerization of a vinyl monomer. The bis-macrocycle (9) was prepared by combining two macrocycles with a linear linker. Radical polymerization of 4-vinylpyridine in the presence of 9 and a catalytic amount of 2,2¢-azobisisobutyronitrile (AIBN) yielded a gelled polymer. The addition of 4-tert-butylstyrene as a vinyl co-monomer to the polymerization system afforded a sufficiently stable gel as the PRN, clearly indicating that 4-tert-butylstyrene was successfully introduced as end-capping moieties of the trunk polymer. The swelling properties of the PRN were evaluated using several solvents. The topological structure and swelling properties of the PRNs were confirmed by a control experiment using a bis-acyclic pincer-type Pd complex (13) Keywords: metal template; Pd-templated bis-macrocycle; polyrotaxane network; rotaxane; topological cross-linker INTRODUCTION Among networked polymers, polyrotaxane networks (PRNs) that have rotaxane structures on the cross-link points are the most interesting class of cross-linked polymers. The generation of unique properties in a network polymer having rotaxane-like cross-links was predicted by de Gennes; 1 one such property leads to easy polymer chain sliding. Ito and coworkers synthesized a hydrogel possessing rotaxane structures at the cross-link points 2 using Harada's cyclodextrin-based polyrotaxane, 3 and this hydrogel has recently been made practicable (Nissan, Kanagawa, Japan) and NTT docomo (Tokyo, Japan) used a PRN as a coating paint of automobile or mobile phone, which is termed as 'SCRATCH SHIELD' . The coating paint shows self-healing properties to scrapes depending on the high elasticity of PRN.). 4,5 However, we reported crown ether-based PRNs that exploit strategic rotaxanation as the cross-linking reaction. [6][7][8][9][10][11][12][13] Although the use of a crown ether as a wheel component allows more precise structures of PRNs than the use of cyclodextrin, the crown ether-based PRN requires the somewhat troublesome synthesis of sec-ammonium axle. To find a simple and widely applicable approach to PRNs, especially toward PRNs containing vinyl polymers, we planned the development of a topological cross-linker that includes a bis-macrocycle moiety to enable efficient penetration of the propagation end of radical polymerization into macrocyclic cavities. We became intrigued in exploiting a Pd(II)-templated bis-macrocycle based on the metal-templated method that is often used for rotaxane architectures (Scheme 1) 14-16 because of the following three merits: (1) the coordination bond of the Pd complex
Dianionic bis(benzenesulfonate)–naphthalenediimide (BSNDI 2– ) formed simple 2:1 cation–anion salts of (NH4 +)2(BSNDI 2– ) (1), (CH3NH3 +)2(BSNDI 2– ) (2), (C2H5NH3 +)2(BSNDI 2– ) (3), [(C2H5)2NH2 +]2(BSNDI 2– ) (4), and [(C2H5)3NH+]2(BSNDI 2– ) (5). The thermal stability, crystal structure, electron transport properties, and dielectric response were evaluated for these systems in terms of π-electron density and dimensional crossover from two-dimensional (2D) and one-dimensional (1D) to zero-dimensional (0D) electronic structures. Systematic modification of the counter cations from NH4 + to simple alkylammoniums (CH3NH3 +, C2H5NH3 +, (C2H5)2NH2 +, and (C2H5)3NH+) for BSNDI 2– salts affected the packing π-density and dimensionality of NDI π-cores. All single crystals formed alternating cation–anion layers, where the intermolecular interactions in salts 1, 2, 3, 4, and 5 were observed as dense 2D brickstone, 1D column, 1D column, dilute 2D herringbone, and isolated 0D monomer arrangements, respectively. The π-electron occupation percentage in the unit cell of salts 1, 2, 3, 4, and 5 decreased in that order, at 96.2%, 87.8%, 83.8%, 78.8%, and 72.6%, respectively, where the intermolecular π–π interaction between BSINDI 2– anions was gradually diluted on increasing in the cation volume. The transfer integrals between the lowest unoccupied molecular orbital in salts 1–5 clearly indicated a dimensional crossover from 2D to 1D to 0D electronic structures. Flash-photolysis time-resolved microwave conductivity measurements of salts 1, 2, 3, and 4 helped determine the magnitude of electron carrier mobility, which followed the order 1 > 2 ≈ 3 ≈ 4. The dielectric response of salt 1 being an order of magnitude higher than those of salts 2–5 was associated with the protonic conductivity in the NH4 +···–SO3– electrostatic hydrogen-bonding network layer. Simple cation exchange in dianionic BSNDI 2– salts conventionally modified the intermolecular π–π interactions in terms of dimensionality, magnitude, and electron transport properties.
Dianionic bis(benzenesulfonate)-naphthalenediimide (BSNDI 2− ) formed simple 2:1 cation−anion salts (Cn-BSNDIs) by the combination of two molar alkylammonium (C n H 2n+1 NH 3 + ) in which the alkyl-chain length (n) was systematically changed from 1 to 16 to study the n-dependent phase transition behavior, molecular assembly structure, dielectric response, and transient conductivity of a series of Cn-BSNDI salts. The electrostatic cation−anion and van der Waals interactions in the molecular assembly compensated for each other, where the elongation of the −C n H 2n+1 chain increased the energy contribution from van der Waals interactions. The crystal lattices of short-chain Cn-BSNDIs (n = 1−4) were rigid and static without temperature-and frequency-dependent dielectric responses. By contrast, large dielectric responses were observed in Cn-BSNDI salts with intermediate n = 5−8 because of the motional freedom of the cation−anion arrangement and thermal fluctuation of the flexible alkyl chains. In the case of Cn-BSNDIs with n = 9−16, the thermal fluctuation of long alkyl chains primarily contributed to the dielectric responses. The one-dimensional intermolecular interactions of Cn-BSNDI salts (n = 1 and 2) showed a dimensional crossover to the two-dimensional C3-BSNDI, and the transient conductivity (ϕΣμ) of C3-BSNDI and C4-BSNDI thin films was much larger than those of the other salts. The rigid crystal lattice of Cn-BSNDIs (n = 3 and 4) became dynamic when n ≥ 5, with a successive phase transition and an even−odd effect in the dielectric constants and ϕΣμ values. The observed interplay of van der Waals and electrostatic interaction allows the dynamic tuning of electronic properties with identical molecular cores as represented by their dielectric response and transient conductivity.
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