A novel, triazine ring-containing succinonitrile-based mechanophore was designed and synthesized through radical stabilization energy calculations and molecular simulations. This mechanophore exhibits higher thermal stability than a classical mechanophore and a clear mechanochromic response via C-C bond cleavage. This enables its incorporation into polymers via radical polymerization. This study advances the design of thermally stable mechanophores and provides new insights into the relationship between structures and properties in radical-based mechanochemistry, offering new opportunities in polymer chemistry.

Fluorescent radicals have attracted great attention as luminescent materials, mostly on account of their potential to achieve higher luminescence efficiency than closed-shell molecules. However, analyzing fluorescent radicals at ambient conditions remains a challenging task, because radicals are usually unstable in air. In addition, to the best of our knowledge, research aimed at controlling fluorescence wavelengths through substituent changes has not yet been accomplished. Here, we report diverse metastable diarylacetonitrile (DAAN) radicals, which contain different substituents, generated by polymeric mechanochemical reactions. The DAAN radicals, generated by ball-milling powdered polystyrene together with DAAN derivatives, were dispersed within the polystyrene matrix, where they retained their radical state, which allowed measuring solid-state fluorescence spectra. These measurements revealed that a wide range of fluorescence wavelengths from green to red (λem,max = 517–635 nm) can be achieved only by changing the substituents on the aromatic rings in these DAAN radicals. This phenomenon has not been observed for the well-studied triarylmethyl radicals. The fluorescence wavelength of these DAAN radicals can be precisely estimated by time-dependent density-functional theory (TD-DFT) calculations. The amount of DAAN radicals generated upon ball-milling is discussed in conjunction with DFT calculations and experimental results. Our results suggest that the orbital interactions with polymeric mechanoradicals, the bond-dissociation enthalpy, and the steric protection of the radical center are of paramount importance for the generation of DAAN radicals. The results of this study can be expected to provide useful guidelines for the development of advanced fluorescent radicals.

Abstract Aim Schizophrenia is characterized by an abnormality in electroencephalography (EEG), which can be affected by antipsychotic drugs. Recently, the mechanism underlying these EEG alterations in schizophrenia patients was reframed from the perspective of redox abnormalities. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) can be calculated using a computational method and may be useful for evaluating the antioxidant/prooxidant effect of antipsychotic drugs. Thus, we examined the association between the effects of antipsychotic monotherapy on quantitative EEG and HOMO/LUMO energy. Methods We used medical report data including EEG results of psychiatric patients admitted to Hokkaido University Hospital. We extracted the EEG records of patients diagnosed with a schizophrenia spectrum disorder undergoing antipsychotic monotherapy during the natural course of treatment (n = 37). We evaluated the HOMO/LUMO energy of all antipsychotic drugs using computational methods. Multiple regression analyses were used to examine the relationship between the HOMO/LUMO energy of all antipsychotic drugs and spectral band power in all patients. Statistical significance was set at p < 6.25 × 10−4 adjusted with Bonferroni correction. Results We showed that the HOMO energy of all antipsychotic drugs had weak positive correlations with delta‐ and gamma‐band power (e.g., standardized β = 0.617 for delta in the F3 channel, p = 6.6 × 10−5; standardized β = 0.563 for gamma in the O1 channel, p = 5.0 × 10−4). Conclusion Although there may be unexpected bias and confounding factors, our findings suggest that the effect of antipsychotic drugs on EEG may be related to their antioxidant actions.

Radical-type mechanophores (RMs) are attractive molecules that undergo homolytic scission of their central C-C bond to afford radical species upon exposure to heat or mechanical stimuli. However, the lack of a rational design concept limits the development of RMs with pre-determined properties. Herein, we report a rational design strategy of RMs with high thermal tolerance while maintaining mechanoresponsiveness. A combined experimental and theoretical analysis revealed that the high thermal tolerance of these RMs is related to the radical-stabilization energy (RSE) as well as the Hammett and modified Swain-Lupton constants at the para-position (σp). The trend of the RSE values is in good agreement with the experimentally evaluated thermal tolerance of a series of mechanoresponsive RMs based on the bisarylcyanoacetate motif. Furthermore, the singly occupied molecular orbital (SOMO) levels clearly exhibit a negative correlation with σp within a series of RMs that are based on the same skeleton, paving the way toward the development of RMs that can be handled under ambient conditions without peroxidation.

Radical-type mechanophores (RMs) can undergo homolytic cleavage of their central C-C bonds upon exposure to mechanical forces, which affords radical species. Understanding the characteristics of these radical species allows bespoke mechanoresponsive materials to be designed and developed. The thermal stability of the central C-C bonds and the oxygen tolerance of the generated radical species are crucial characteristics that determine the functions and applicability of such RM-containing mechanoresponsive materials. In this paper, we report the synthesis and characterization of two series of arylfluorene-based RM derivatives, that is, 9,9'-bis(5-methyl-2-pyridyl)-9,9'-bifluorene (BPyF) and 9,9'-bis(4,6-diphenyl-2-triazyl)-9,9'-bifluorene (BTAF). BPyF and BTAF derivatives were synthesized without generating any peroxides initially, albeit that BPyF slowly converted to the corresponding peroxide in solution. DFT calculations revealed the importance of the thermodynamic stability and the values of the alpha-SOMO levels of the corresponding radical species for their thermal stability and oxygen tolerance. Furthermore, the mechanochromism of BTAF was demonstrated by ball-milling a BTAF-centered polymer, which was synthesized by atom-transfer radical polymerization (ATRP).

The exploration of mechanochemical reactions has brought new opportunities for the design of functional materials. We synthesized the novel organic peroxide mechanophore bis(9-methylphenyl-9-fluorenyl) peroxide (BMPF) and examined its mechanochromic properties. The mechanism behind its mechanofluorescence was clarified and harnessed in polymer networks that can release the small fluorescent molecule 9-fluorenone upon exposure to a mechanical stimulus. Additionally, polymer networks cross-linked with BMPF units are able to tolerate temperatures up to 110 °C without any change in optical properties or mechanical strength. As mechanophores based on organic peroxide have rarely been documented so far, these fascinating results suggest excellent potential for applications of BMPF in stress-responsive materials. The mechanochemical protocol demonstrated here may provide guiding principles to expand the field of mechanochromic peroxides.

A non-symmetric radical-type mechanophore (CF/ABF) was synthesized by molecular crossing between two radical-type mechanophores. The thermal stability and mechanoresponsiveness of CF/ABF were found to be tunable by altering the properties of the parent RMs. The CF/ABF-centred polymers showed mixed mechanochromism derived from the simultaneous generation of two radical species.

Mechanofunctional polymers that exhibit color change, fluorescence, and self-strengthening ability were developed by Hideyuki Otsuka et al. in their Communication on page 8406. It is the first example of force-induced cross-linking reactions achieved by only the extension or compression of a bulk film. The cross-linking reaction can be visualized via color change and fluorescence and evaluated by electron paramagnetic resonance spectroscopy.

Mechanofunktionelle Polymere , die einen Farbwechsel, Fluoreszenz und die Fähigkeit zur Selbstverfestigung aufweisen, werden von Hideyuki Otsuka et al. in ihrer Zuschrift auf S. 8487 vorgestellt. Es ist das erste Beispiel für kraftinduzierte Vernetzungsreaktionen, die nur durch Dehnung oder Kompression eines Bulk-Films erreicht werden. Die Vernetzungsreaktion kann über Farbumschlag und Fluoreszenz visualisiert und mittels elektronenparamagnetischer Resonanzspektroskopie verfolgt werden.

Mechanochromic elastomers that exhibit force-induced cross-linking reactions in the bulk state are introduced. The synthesis of segmented polyurethanes (SPUs) that contain difluorenylsuccinonitrile (DFSN) moieties in the main chain and methacryloyl groups in the side chains was carried out. DFSN was selected as the mechanophore because it dissociates under mechanical stimuli to form pink cyanofluorene (CF) radicals, which can also initiate the radical polymerization of methacrylate monomers. The obtained elastomers generated CF radicals and changed color by compression or extension; they also became insoluble due to the mechanically induced cross-linking reactions. Additionally, an SPU containing diphenylmethane units also exhibited highly sensitive mechanofluorescence. To the best of our knowledge, this is the first report to demonstrate damage detection ability and changes in the mechanical properties of bulk elastomers induced by simple compression or extension.

In this study, we report the synthesis of dithieno[2,3-d:2′,3′-d']anthra[1,2-b:5,6-b']dithiophene (DTADT) unit and donor-acceptor (D-A) conjugated copolymers incorporated with the DTADT unit as the repeating unit. The novel oligoheteroacene unit––DTADT––was synthesized through the [2+2+2] annulation, which is the key reaction, and its reaction pathway was theoretically revealed using the density functional theory calculation. The D-A conjugated copolymers, synthesized through the transition metal-catalyzed polycondensation, could be applied as a solution-processable thin-film transistor. The our own n-layered integrated molecular orbital and molecular mechanics calculation in conjunction with the second order perturbation theory, analyzed based on the natural bond orbital analysis, unveiled that the steric repulsion among the side chains of DTADT and thiophene spacer kept away from the planarization of polymers; this affected the hole mobility of organic field-effect transistor.

Artificial intelligence- and machine learning (ML)-assisted reaction/material development are an emerging research area in organic, organometallic, polymer chemistry and materials science. Quantum chemical descriptors (QCDs) that are classically constructed with steric/electrostatic parameters make the process of the prediction through ML easily understood and allow us to find new chemical pictures for reaction, materials and functionality. Herein, I present the development of novel QCDs—interactive-quantum-chemical-descriptors (IQCDs)—well-expressing an intermolecular interaction among target molecules. The use of IQCDs drastically improved the prediction-accuracy rather than the use of only the classical QCD. One of the IQCDs consists of natural energy decomposition analysis (NEDA), well-expressing a chemical interaction among the molecules/materials, which would be applicable for dynamic processes including formation of chemical bonding, organometallic complex, and supramolecular complex.

Herein, we report the synthesis of soluble, air-stable fully conjugated ladder polymers incorporating a BTBT structure as a repeating unit. The ladder polymers were synthesized through a simple process: A Migita-Kosugi-Stille polycondensation, followed by an intramolecular oxidative C–H annulation (Scholl reaction). Absorption and fluorescence spectrometric analyses, as well as theoretical analysis and model reaction revealed that the intramolecular Scholl reaction proceeded efficiently. Electrochemical studies combined with theoretical molecular orbital analysis indicated that the resultant ladder polymers are stable under ambient conditions, because the drastic ascension of the highest-occupied molecular orbital (HOMO) level was suppressed even after ladderization by the Scholl reaction. Furthermore, the bottom-gate top-contact organic thin-film devices that were fabricated from these ladder polymers operated as solution-processable p-type transistors.

The intramolecular direct arylation of N,N′‐dihexyl‐N‐(2‐bromophenyl)‐N′‐phenylurea using palladium catalyst gave BPU in 75 % yield. Longer terphenyl compound (TPbU) was likewise prepared. Other four conjugated oligomers (BPtU, BPU‐1Np, BPU‐2Np, and BPU‐Ant) were synthesized from BPU in short reaction steps. From the X‐ray crystallography, BPtU with the thiourea skeleton was suggested to have a quasi C=N double bond character. Each enantiomer was optically resolved on chiral HPLC to show mirroring Cotton effects and monosignate CD patterns. The enantiomeric excess (ee.) values were evaluated by HPLC, from which BPU and TPbU exhibited comparable racemization energy barriers (ΔG‡rac = 23.3 kcal mol–1 and 23.4 kcal mol–1). The racemization energy barrier of BPtU was considerably high (ΔG‡rac = 30.1 kcal mol–1) likely due to the quasi C=N double bond character. On the other hand, BPU‐2Np and BPU‐Ant having the π‐conjugated system exhibited ΔG‡rac of 23.8 kcal mol–1 and 24.0 kcal mol–1, respectively. These experimental results were well explained by theoretical analyses.

Pseudo-ladderized polystyrenes could be obtained in high yield by the palladium-catalyzed polymer direct arylation using poly(2-bromostyrene) as a prepolymer.

Herein we present a missing reactivity of trimethylsilyl reagents; dehalogenative activation, which involves abstracting a halogen atom and anionically activating the substrate similar to the halogen-metal exchange reaction in classical carbanion species. This missing reactivity allowed for the one-pot generation of aryne from 2-iodophenol.

Unlike classical polymers consisting of monomer units connected by a single covalent bond, ladder polymers having two covalent bonds between repeating units are considered to be new materials showing high thermal stability, and intrinsic porosity. In this mini-review, I focus recent synthetic/structural development of ladder polymers; 1. Pd catalyzed annulation reaction, 2. olefin metathesis reaction, and 3. a synthetic methodology for flexible ladder polymers. These developments will enable ladder polymers to apply for innovative porous materials, thin-film devices, and adhesive materials.

Several palladium catalysts with bulky phosphine ligands other than t-Bu3P were investigated for Suzuki-Miyaura catalyst-transfer condensation polymerization (CTCP). When the model reaction of 2,S-dibromothiophene with phenylboronic acid ester was carried out with a variety of Pd precatalysts in the presence of K3PO4 as a base, we found that the use of di-tert-butyl(4-dimethylaminophenyl)phosphine (AmPhos) Pd as a precatalyst resulted in exclusive formation of diphenyl-substituted thiophene. Polymerization of thiophene monomer and fluorene monomer with an initiator generated in situ from AmPhos Pd precatalyst and 4-iodobenzonitrile proceeded via the CTCP mechanism, affording polythiophene (P3HT) and polyfluorene with low dispersity and controlled polymer ends. Furthermore, (tolyl)PdAmPhos(Br) (7) was synthesized, and its polymerization properties were investigated. We found that polymerization of thiophene monomer with a mixture of 7 and CsF that had been stirred for 1 h prior to polymerization afforded P3HT with the dispersity of 1.18, which was considerably narrower than that in the case of CTCP with PhPd(t-Bu3P)Br. Block copolymerization of thiophene monomer and fluorene monomer with 7 proceeded irrespective of the polymerization order, in contrast to PhPd(t-Bu3P)Br-catalyzed block copolymerization, in which only chain extension with thiophene monomer from a polyfluorene propagating end took place and the reverse chain extension did not.

Carboxylic acid chlorides are useful substrates in organic chemistry. Many germanium analogues of carboxylic acid chloride have been synthesized so far. Nevertheless, all of the reported germathioacid chlorides use bidentate nitrogen ligands and contain germanium-nitrogen bonds. Our group synthesized germathioacid chloride, Ge(S)Cl{C6H3-2,6-Tip2}(Im-i-Pr2Me2), using N-heterocyclic carbene (Im-i-Pr2Me2). As a result of density functional theory (DFT) calculation, it was found that electrons are localized on sulfur, and the germanium-sulfur bond is a single bond with a slight double bond property.

The balance between the ring-walking process and the oxidative-addition state are key determinants of catalyst mobility in catalyst-transfer condensation polymerization.