Carrier Transport Switching of Ferroelectric BTBT Derivative

Alkylamide-substituted [1]benzothieno[3,2-b][1]benzothiophene (BTBT) derivative of BTBT-NHCOC14H29 (1), which has ferroelectric N-H···O= hydrogen-bonding network of alkylamide group and two-dimensional (2D) electric structure of BTBT π-cores, was prepared to design the external electric field-responsive organic semiconductors. The short-chain derivative of BTBT-NHCOC3H7 (1') revealed the coexistence of a 2D electronic band structure based on the herringbone BTBT arrangement and the one-dimensional (1D) hydrogen-bonding chain. 1 formed a smectic E (SmE) liquid crystal phase above 412 K and showed ferroelectric hysteresis in the electric field-polarization (P-E) curves at 403-433 K. The remanent polarization (Pr) and coercive electric field (Ec) of 1 at 408 K, 0.1 Hz were 24.0 μC cm-2 and 5.54 V μm-1, respectively. By thermal annealing of thin-film 1 at 443 K, the molecular assembly structure of 1 changed from a monolayer to a bilayer structure with high crystallinity, resulting in conducting layers of BTBT parallel to the substrate surface. The organic field-effect transistor (OFET) device with thermally annealed thin-film 1 showed p-type semiconducting behavior with the hole mobility of 1.0 × 10-3 cm2 V-1 s-1. Furthermore, device 1 showed switching behavior of semiconducting properties by electric field poling and thermal annealing cycle. The electric field response of ferroelectrics modulated the molecular orientation and conduction properties of organic semiconductors, resulting in external electric field control of carrier transport properties.

Urea-Comprising Single Core Diketopyrrolopyrrole Derivatives: Exploring the Synthesis, Self-Assembly and Charge Transport Properties

Supramolecular electronics exploits the distinctive features stemming from noncovalent interactions, guiding the self-assembly of molecules to craft materials endowed with customized electronic functionalities. Hydrogen-bonded materials, characterized by their capacity to establish dynamic and stable networks, introduce an extra dimension to the development of supramolecular electronic systems. This study presents a comparative analysis of two remarkably small semiconductors utilizing diketopyrrolopyrrole functionalized with urea units as hydrogen-bonding motifs, strategically positioned at opposing ends of the conjugated core. We show how the subtle distinction in functionalization not only influences morphology and self-assembly dynamics via hydrogen-bonding and π-π stacking formation, but also holds significant consequences for ultimate charge transport properties. Our observations into the interplay of noncovalent interactions provide valuable insights and strategic pathways for the design of novel materials with enhanced electronic characteristics.

Ferroelectric Organic Semiconductor: [1]Benzothieno[3,2-b][1]benzothiophene-Bearing Hydrogen-Bonding -CONHC14H29 Chain

An alkylamide-substituted [1]benzothieno[3,2-b][1]benzothiophene (BTBT) derivative of BTBT-CONHC14H29 (1) and C8H17-BTBT-CONHC14H29 (2) were prepared to design the multifunctional organic materials, which can show both ferroelectric and semiconducting properties. Single-crystal X-ray structural analyses of short-chain (-CONHC3H7) derivatives revealed the coexistence of two-dimensional (2D) electronic band structures brought from a herringbone arrangement of the BTBT π core and the one-dimensional (1D) hydrogen-bonding chains of -CONHC3H7 chains. The thin films of 1 and 2 fabricated on the Si/SiO2 substrate surface have monolayer and bilayer structures, respectively, resulting in conducting layers parallel to the substrate surface, which is suitable for a channel layer of organic field-effect transistors (OFETs). The thin film of 1 indicated a hole mobility μFET = 2.4 × 10-5 cm2 V-1 s-1 and threshold voltage VTh = - 29 V, whereas that of 2 showed a μFET = 2.1 × 10-2 cm2 V-1 s-1 and threshold voltage VTh = -9.7 V. Both 1 and 2 formed the smectic E (SmE) phase above 410 and 369 K, respectively, where the existence of a hole transport pathway was confirmed in the SmE phase. The ferroelectric hysteresis behavior was observed in bulk 1 and 2 in the polarization-electric field (P-E) curves at the SmE phase. 1 showed the remanent polarization Pr = 2.3 μC cm-2 and coercive electric field Ec = 5.2 V μm-1, whereas the Pr and Ec of 2 were 3.4 μC cm-2 and 7.0 V μm-1 at the conditions of 453 K and 1 Hz. Introduction of alkylamide units into the BTBT π core has the potential to develop the external stimulus-responsive organic semiconductors brought from both ferroelectricity and semiconducting properties.

Structural Transformable Coulomb Lattice of n-Type Semiconductors for Guest Sorption

In recent years, highly designable organic porous materials have attracted considerable attention in the development of new types of molecular adsorption-desorption materials. The adsorption-desorption process also changes the electronic structure via the existence of guest molecules. Therefore, it is possible to change the physical property during the guest adsorption-desorption cycle using an appropriate chemical design of the host crystal lattice. As the development of n-type organic semiconductors has been limited, we focused on designing an n-type organic semiconductor material to control the host crystal lattice, electronic dimensionality, chemical stability, and high electron mobility using an ionic naphthalenediimide (NDI) derivative. Low symmetrical dianionic bis(benzene-m-sulfonate)-naphthalenediimide (m-BSNDI^2-) forms various types of single-crystal (M⁺)₂(m-BSNDI^2-)·n(guest) with a combination of M⁺ = Na⁺, K⁺, Rb⁺, and guest = H₂O, CH₃OH. Four crystals of (K⁺)₂(m-BSNDI^2-)·n(H₂O), (K⁺)₂(m-BSNDI^2-)·n(CH₃OH), α-(K⁺)₂(m-BSNDI^2-), and β-(K⁺)₂(m-BSNDI^2-) were transformable using the guest adsorption-desorption cycle. Two kinds of single-crystal (K⁺)₂(m-BSNDI^2-)·n(CH₃OH) with n = 0 and 2.0 showed a single-crystal to single-crystal (SCSC) transformation through CH₃OH desorption. On the contrary, five kinds of single crystals with n = 0, 3.0, 3.3, 4.75, and 5.5 were identified in the single-crystal X-ray structural analyses of (K⁺)₂(m-BSNDI^2-)·n(H₂O). Systematic change of the ionic radii in (M⁺)₂(m-BSNDI^2-) modified the crystal lattice flexibility for the guest adsorption-desorption cycles.

Dendritic-Like Molecules Built on a Pillar[5]arene Core as Hole Transporting Materials for Perovskite Solar Cells

Invited for the cover of this issue are the groups of S. Seki (Kyoto), G. Reginato (Sesto Fiorentino), J.-F. Nierengarten (Strasbourg), A. Abate (Berlin) and J. L. Delgado (San Sebastian). The image depicts an artistic view of a dendrimer-like hole transporting material at work in a perovskite solar cell. Read the full text of the article at 10.1002/chem.202101110.

Dendritic-Like Molecules Built on a Pillar[5]arene Core as Hole Transporting Materials for Perovskite Solar Cells

Multi-branched molecules have recently demonstrated interesting behaviour as charge-transporting materials within the fields of perovskite solar cells (PSCs). For this reason, extended triarylamine dendrons have been grafted onto a pillar[5]arene core to generate dendrimer-like compounds, which have been used as hole-transporting materials (HTMs) for PSCs. The performances of the solar cells containing these novel compounds have been extensively investigated. Interestingly, a positive dendritic effect has been evidenced as the hole transporting properties are improved when going from the first to the second-generation compound. The stability of the devices based on the best performing pillar[5]arene material has been also evaluated in a high-throughput ageing setup for 500 h at high temperature. When compared to reference devices prepared from spiro-OMeTAD, the behaviour is similar. An analysis of the economic advantages arising from the use of the pillar[5]arene-based material revealed however that our pillar[5]arene-based material is cheaper than the reference.

Switching of Electron and Ion Conductions by Reversible H2O Sorption in n-Type Organic Semiconductors

Polar H₂O molecules generally act as trapping sites and suppress the electron mobility of n-type organic semiconductors, making chemical design of H₂O-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 π-framework enables the design of high-performance H₂O-tolerant n-type semiconductors with a reversible H₂O adsorption-desorption ability, where the electron mobility and K⁺ ionic conductivity were coupled with the reversible H₂O sorption behavior. The reversible H₂O adsorption into the crystals enhanced the electron mobility from 0.04 to 0.28 cm² 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 H₂O sorption behavior, it is a strong candidate for H₂O gating carrier transport systems.

Intermolecular cascaded π-conjugation channels for electron delivery powering CO2 photoreduction

Photoreduction of CO₂ to fuels offers a promising strategy for managing the global carbon balance using renewable solar energy. But the decisive process of oriented photogenerated electron delivery presents a considerable challenge. Here, we report the construction of intermolecular cascaded π-conjugation channels for powering CO₂ photoreduction by modifying both intramolecular and intermolecular conjugation of conjugated polymers (CPs). This coordination of dual conjugation is firstly proved by theoretical calculations and transient spectroscopies, showcasing alkynyl-removed CPs blocking the delocalization of electrons and in turn delivering the localized electrons through the intermolecular cascaded channels to active sites. Therefore, the optimized CPs (N-CP-D) exhibiting CO evolution activity of 2247 μmol g⁻¹ h⁻¹ and revealing a remarkable enhancement of 138-times compared to unmodified CPs (N-CP-A).

While conversion of CO₂ to fuels may offer a bio-inspired means to renewably utilize fossil fuel emission, most materials demonstrate poor activities for CO₂ reduction. Here, authors construct conjugated polymers that modulate photo-induced electron transfer to CO₂ reduction catalysts.

Protein-directed crystalline 2D fullerene assemblies

Water soluble 2D crystalline monolayers of fullerenes grow on planar assemblies of engineered consensus tetratricopeptide repeat proteins. Designed fullerene-coordinating tyrosine clamps on the protein introduce specific fullerene binding sites, which facilitate fullerene nucleation. Through reciprocal interactions between the components, the hybrid material assembles into two-dimensional 2 nm thick structures with crystalline order, that conduct photo-generated charges. Thus, the protein-fullerene hybrid material is a demonstration of the developments toward functional materials with protein-based precision control of functional elements.

Helical Pore Alignment on Cylindrical Carbon

Interest in chiral substances has mainly focused on the substances themselves, but not on the accompanying space, especially regarding the pore alignment. As a method to form both the chiral substance and the accompanying space, cylindrical self-assembly of uniform polystyrene nanoparticles with fructose is carried out in the presence of both carbon and sodium alginate, which is followed by heat treatment in an inert atmosphere. The carbonization generates fructose-derived honeycomb-like carbon walls with helically aligned nanopores left after the polystyrene decomposition. The diffuse reflectance circular dichroism measurements give peaks with opposite signs for the d- and l-fructose-derived cylindrical carbons. Circularly polarized light sensitivity in transient photoconductivity is confirmed apparently in the carbon-based helical structures. This sensitivity as well as straightforward formation of composites with another component to give helicity shows potential applications of the helically aligned pores.

Two-step template method for synthesis of axis-length-controlled porphyrin-containing hollow structures

π-Conjugated porphyrin-containing hollow structures with defined axis-length were successfully synthesized by a two-step template method, i.e., template-assisted cyclization and oligomerization.

Preparation, Electronic and Liquid Crystalline Properties of Electron-Accepting Azaacene Derivatives

A series of electron-accepting azaacene-type materials 1-4 with different kinds and degrees of intermolecular interactions were synthesized. Simple modification of the terminal substituents significantly modulated the photophysical and electrochemical properties. The degree of weak intermolecular interaction determined the emergence of a liquid crystalline (LC) phase for each compound. Dipole-dipole interaction, π-π interaction, and van der Waals interaction all contributed to stabilize the LC phase of 1 and 2. The introduction of strong hydrogen bonding interaction enabled the formation of a highly ordered LC phase in 4. Charge-transport properties of 1, 2, and 4 were also investigated.

Efficient Benzodithiophene/Benzothiadiazole-Based n-Channel Charge Transporters

A series of donor-acceptor (D-A) small molecules based on electron-deficient benzothiadiazole (BTD) and electron-rich benzodithiophene (BDT) featuring an A-D-A structure is presented. Exhaustive spectroscopic, electrochemical, and computational studies evidence their electroactive nature and their ability to form well-ordered thin films with broad visible absorptions and low band gaps (ca. 2 eV). Time-resolved microwave conductivity (TRMC) studies unveil unexpected n-type charge transport displaying high electron mobilities around 0.1 cm²  V^-1  s^-1 . Efficient electron transport properties are consistent with the low electron reorganization energies (0.11-0.17 eV) theoretically predicted.

Regioisomer effects of [70]fullerene mono-adduct acceptors in bulk heterojunction polymer solar cells

Regioisomer separations of [70]fullerene mono-adducts for polymer solar cell (PSC) applications were conducted for the first time.

Despite numerous organic semiconductors being developed during the past decade, C₇₀ derivatives are predominantly used as electron acceptors in efficient polymer solar cells (PSCs). However, as-prepared C₇₀ mono-adducts intrinsically comprise regioisomers that would mask individual device performances depending on the substituent position on C₇₀. Herein, we separate the regioisomers of C₇₀ mono-adducts for PSC applications for the first time. Systematic investigations of the substituent position effect using a novel symmetric C₇₀ mono-adduct ([70]NCMA) and a prevalent, high-performance one ([70]PCBM) reveals that we can control the structures of the blend films with conjugated polymers and thereby improve the PSC performances by regioisomer separation. Our approach demonstrates the significance of exploring the best-matching regioisomer of C₇₀ mono-adducts with high-performance conjugated polymers, which would achieve a remarkable progress in PSC devices.

π-Electron Systems That Form Planar and Interlocked Anion Complexes and Their Ion-Pairing Assemblies

Interactions between designed charged species are important for the ordered arrangements of π-electron systems in assembled structures. As precursors of π-electron anion units, new arylethynyl-substituted dipyrrolyldiketone boron complexes, which showed anion-responsive behavior, were synthesized. They formed a variety of receptor-anion complexes ([1+1] and [2+1] types) in solution, and the stabilities of these complexes were discussed in terms of their thermodynamic parameters. Solid-state ion-pairing assemblies of [1+1]- and [2+1]-type complexes with countercations were also revealed by single-crystal X-ray analysis. In particular, a totally charge-segregated assembly was constructed based on negatively and positively charged layers fabricated from [2+1]-type receptor-anion complexes and tetrabutylammonium cations, respectively. Furthermore, the [1+1]-type anion complex of the receptor possessing long alkyl chains exhibited mesophases based on columnar assembled structures with contributions from charge-by-charge and charge-segregated arrangements, which exhibited charge-carrier transporting properties.

Evaluation of the intrinsic charge carrier transporting properties of linear- and bent-shaped π-extended benzo-fused thieno[3,2-b]thiophenes

The local-scale hole mobilities of two isomeric linear- and bent-shaped π-extended thienoacenes were investigated using flash-photolysis and field-induced time-resolved microwave conductivity (FP- and FI-TRMC) techniques.

Synthesis and characterization of an electroactive surface that releases gamma-aminobutyric acid (GABA)

We report the synthesis and characterization of a new electroactive surface capable of releasing the neurotransmitter gamma-aminobutyric acid (GABA) upon reduction. The GABA was anchored to an alkanethiol via electrochemically active quinone (abbreviation, TM-GABA). The quinone unit, upon reduction to the hydroquinone, cyclizes to release GABA into solution. The half-life is 99 s. The self-assembled monolayer (SAM) of TM-GABA on gold was prepared and characterized with several surface sensitive techniques. X-ray photoelectron spectroscopy (XPS) explored the SAM formation of TM-GABA on Au surfaces. Cyclic voltammograms showed the ability to electrochemically control the quinone unit at the distal end of the chain. GABA was selectively released upon electrochemical reduction at a potential of -700 mV. The functional GABA terminal group was detected by surface plasmon resonance measurements of anti-GABA antibody binding.

Awakenings from persistent vegetative state: report of three cases with parkinsonism and brain stem lesions on MRI

Three patients with a persistent vegetative state after severe head injury are reported. They recovered from a prolonged disturbance of consciousness after the administration of levodopa. These patients all had parkinsonian features. On magnetic resonance imaging, the distribution of lesions implied a diffuse axonal injury involving the substantia nigra or ventral tegmental area. The existence of patients whose dopaminergic systems may have been selectively damaged by a severe head injury should be recognised because such individuals may respond to levodopa treatment.

[A case of cardiogenic cerebral embolism with successful recanalization: apparent diffusion coefficient analysis for prediction of reversible cerebral ischemia]

A 54-year-old woman complaining of left hemiplegia was transferred to our hospital. Computed tomography on admission demonstrated normal. Electrocardiogram showed atrial fibrillation. Cerebral blood flow (CBF) was decreased in both the cortex and the perforator territory of the right middle cerebral artery (MCA), whereas the apparent diffusion coefficient (ADC) in the cortex was normal. Digital subtraction angiography (DSA) revealed an occlusion of the right MCA (M 1 proximal) with collateral flow from the right anterior cerebral artery (ACA) to the territory of the right MCA. After intra-arterial injection of tissue-plasminogen activator (t-PA), DSA showed partial recanalization, and the symptoms of the patient improved considerably. Five days after that, the patient deteriorated again and showed disturbance of consciousness and left hemiplegia. In this episode, both CBF and ADC in the cortex of the right MCA were decreased. DSA revealed an occlusion of the right internal carotid artery (ICA) and collateral flow from the right ACA to the territory of the right MCA disappeared. After intra-arterial injection of t-PA, DSA showed partial recanalization with collateral flow from the right ACA, and the symptoms of the patient improved. DSA 5 weeks after onset showed complete recanalization of both the right MCA and the ICA. The patient was diagnosed as both mitral and aortic stenosis and regurgitation (MSR + ASR) and underwent an operation for both mitral and aortic value replacement. She was discharged with no neurological deficit 4 months after onset. ADC analysis is especially useful for the prediction of reversible ischemic damage and the prevention of hemorrhagic transformation and fatal edema in acute ischemic stroke.

[Clinical usefulness of diffusion-weighted magnetic resonance imaging in patients with ischemic cerebrovascular disease]

Diffusion-weighted magnetic resonance imaging was performed to determine the detectability of ischemic changes in patients with ischemic cerebrovascular disease. We retrospectively reviewed 103 patients with symptoms suggestive of ischemic cerebrovascular disease. All patients underwent computed tomography, routine magnetic resonance imaging, and diffusion-weighted imaging. Of 103 patients, 18 were imaged within 3 hours after onset, 57 were imaged between 3 and 24 hours, and 29 were imaged between 24 and 144 hours. Eighty-eight patients were diagnosed as ischemic cerebrovascular disease. Magnetic resonance imaging was performed at a 1.0 Tesla clinical machine using single-shot spin-echo/echo-planar imaging sequence. In each case, three sets of DWI with motion-probing gradient pulses in the x, y, and z directions were taken. The detectability of ischemic changes of each imaging modality was compared. DWI detected ischemic changes in 83 of 88 cases with clinical diagnoses of cerebral ischemia(sensitivity; 94.3%). In contrast, DWI showed negative findings in 15 of the 15 patients with diagnoses other than cerebral ischemia(selectivity; 100.0%). DWI detected ischemic changes in 16 out of 18 patients(88.6%) within 3 hours after the onset. In contrast, T 2-weighted image did not detect any ischemic changes in the same period. These results suggest that DWI is considered to be highly useful for the early diagnosis of cerebral ischemia.

[A case of primary brain-stem injury recovered from persistent vegetative state after L-dopa administration]

A 51-year-old male was transferred to our hospital just after traffic accident. On admission, the patient was comatose (Glasgow Coma Scale of 6) and showed a left hemiparesis with a left oculomotor nerve palsy. Computed tomography demonstrated a traumatic subarachnoid hemorrhage without mass lesion. Magnetic resonance imaging showed high intensity lesions on the left dorsolateral midbrain and the right cerebral peduncle. The distribution of lesions implied diffuse axonal injury involving dopaminergic systems such as the substantia nigra and the ventral tegmental area. After several months of conservative management, the patient showed no recovery and was diagnosed as persistent vegetable state. The administration of L-dopa was then started and the patient showed remarkable neurological improvement. Therefore the patient's neurological status was thought to be modified with primary brain stem injury and accompanying traumatic Parkinson's syndrome. It is important to understand "pseudo" persistent vegetative state in the management of patients showing prolonged consciousness disturbance. L-dopa should be considered as the drugs of pharmacological intervention for the patients of masked parkinsonism behind "pseudo" persistent vegetative state whose dopaminergic systems might have been damaged.

[Ketamine infusion therapy for refractory neuralgia in spinal disease: report of two cases]

We report two cases of refractory pain in a spinal disease. One case was a 60-year-old male who presented intractable pain in bilateral upper extremities after anterior fusion (C5/6, 6/7) for cervical spondylosis. The other was a 63-year-old female who also had intractable pain in the left anterio-lateral chest wall with no remarkable past history. Both cases were refractory to nonsteroidal anti-inflammatory drugs (NSAIDs) or minor tranquilizer or local anesthesia with bupivacaine. However, their pain was significantly relieved by the intravenous administration of a test dose (5mg) of ketamine which is a noncompetitive blocker of N-methyl-D-aspartate (NMDA) receptors. As for case 1, the effect of the injection of the test dose lasted, so continuing infusion therapy of ketamine was cancelled. In case 2, recurrence of the pain was recognized gradually. She underwent continuing infusion therapy of 2mg/kg of ketamine, and it brought about continued pain relief. We conclude that ketamine infusion therapy should also be considered for therapy of refractory neuralgia in spinal disease.