The emission process of the o‐carborane dyad with anthracene originating from the twisted intramolecular charge transfer (TICT) state in the crystalline state is described. The anthracene‐o‐carborane ...dyad was synthesized and its optical properties were investigated. Initially, the dyad had aggregation‐ and crystallization‐induced emission enhancement (AIEE and CIEE) properties via the intramolecular charge transfer (ICT) state. Interestingly, the dyad presented the dual‐emissions assigned to both locally excited (LE) and ICT states in solution. From the mechanistic studies and computer calculations, it was indicated that the emission band from the ICT should be attributable to the TICT emission. Surprisingly, even in the crystalline state, the TICT emission was observed. It was proposed from that the compact sphere shape of o‐carborane would allow for rotation even in the condensed state.
The emission process of the o‐carborane–anthracene dyad arising from the twisted intramolecular charge transfer (TICT) state in the crystalline state is described. The dyad displays aggregation‐ and crystallization‐induced emission enhancement properties via the intramolecular charge transfer (ICT) state. Interestingly, rotation could occur even in the condensed state.
Our work on the characteristics of organoboron‐containing polymers is reviewed. The electronic interaction and correlation involving organoboron complexes are responsible for the optical and electric ...properties of the polymers. To understand the origins of these properties and apply them to the next generation of new materials, we have gathered not only fundamental knowledge on the electronic states and behaviors of each organoboron complex in the polymers but also on the functions of the polymers in devices. In this article, we introduce our findings obtained from a series of studies on polymers involving cyclodiborazane, quinolate, diketonate, dipyrromethene, pyrazabole, and carborane complexes. In particular, there is a focus on results from recent work.
Organoboron polymers can be a key material for constructing advanced optoelectronic devices. We have studied the fundamental chemistry of the electronic structures and behavior in the π‐conjugation through the polymer main chains. Moreover, we aim to develop practical advanced devices based on organoboron polymers. In this article, our work on organoboron polymers is reviewed.
We report a series of mechanofluorochromic (MFC) compounds based on organoboron complexes with aggregation‐induced emission (AIE) characteristics. We synthesized a variety of boron ketoiminates and ...investigated the effect of the substituents on the optical properties by altering the end groups in the compounds. The synthesized boron ketoiminates showed AIE properties and MFC behavior. Interestingly, the hypsochromic and bathochromic shifts of the emission bands individually observed for boron ketoiminates depended on the chemical structures of the end groups. From the X‐ray diffraction and differential scanning calorimetry analyses, it was confirmed that the MFC property of boron ketoiminates should be derived from a phase transition between crystalline and amorphous states. In addition, the direction of the peak shifts of the emission bands was controlled by the degree of steric hindrance of the end group.
Scratch that! A series of aggregation‐induced emission (AIE)‐active boron ketoiminates with mechanofluorochromic (MFC) properties have been synthesized. From the X‐ray diffraction and differential scanning calorimetry analyses, it was suggested that the MFC property derives from a phase transition between the crystalline and amorphous states, and the direction and extent of the peak shift can be controlled by changing the end group (see figure).
The molecular design based on o-carborane dyads is described for preparing multifunctional luminescent molecules such as dual emissions, aggregation and crystallization-induced emission enhancements, ...and luminescent color changes. The pyrene-substituted o-carborane dyads were synthesized via the insertion reaction between decaborane and 1-ethynylpyrene in the presence of Lewis base in a good yield. Finally, extremely bright luminescent compounds with solid-state emission properties (ΦPL > 0.99) were obtained.
This manuscript reports the multi‐functional boron complex presenting aggregation‐induced emission (AIE), crystallization‐induced emission enhancement (CIEE), and thermosalient behavior accompanying ...thermochromic luminescence during crystal–crystal transitions by employing the fused azomethine ligand. In particular, we propose that these properties can be explained by molecular “flexibility” toward external stimuli, including temperature changes and photo‐excitation, and two types of crystal polymorphs with different absorption and luminescent properties were obtained. Optical measurements indicated that both polymorphs showed individual AIE and strong CIEE properties. From the investigations, the boron complex showed large structural relaxation and formed the bent structure in the excited state, followed by emission annihilation in the absence of structural restriction. In addition, it was shown that interconversion between these polymorphs could be reversibly induced by heating and cooling. The data from the single‐crystal X‐ray analyses suggested that alteration of crystal packing and intermolecular interaction should influence the luminescent chromism. Moreover, we also found that the crystals showed unusual mechanical behavior, such as hopping and fragmentation by heating and cooling, respectively, which is called thermosalient behavior. It was suggested that the loosely‐fused structure could be responsible for expressing unique optical and mechanical properties.
A new boron complex with aggregation‐induced emission property was designed and synthesized based on the strategy to improve the flexibility of a molecular skeleton. The complex showed environment‐sensitive solid‐state emission and unexpectedly thermosalient effects with luminescent chromism.
A series of boron ketoiminate derivatives that exhibited clear aggregation‐induced emission (AIE) characteristics (in THF: ΦPL≤0.01; in the solid state: ΦPL=0.30–0.76) were prepared by the reactions ...of 1,3‐enaminoketone derivatives with boron trifluoride–diethyl etherate. The structures and optical properties were investigated by UV‐visible spectroscopy, photoluminescent (PL) spectroscopy, and X‐ray single‐crystal measurements. These results indicate that the AIE characteristics were derived from molecular motions of the boron‐chelating rings with a boronnitrogen (BN) bond. Furthermore, the optical properties were controllable by steric hindrance of the substituted groups on the nitrogen atom.
Molecules in motion: A series of boron ketoiminate derivatives that exhibited efficient aggregation‐induced emission (AIE) characteristics (in THF: ΦPL≤0.01; in the solid state: ΦPL=0.30–0.76) were synthesized (see figure). The results of investigations indicate that the AIE characteristics are derived from molecular motions of the boron‐chelating rings with a boronnitrogen bond.
An element-block is defined as a minimum functional unit composed of heteroatoms. The concept of 'element-block material' for designing advanced materials was proposed in 2015. In this review, the ...recent progress in material designs based on this concept is described. From our research, several element-blocks as representative examples are selected, and their roles in each material are explained. Initially, research on the development of 'designable hybrids' by employing polyhedral oligomeric silsesquioxane (POSS) is illustrated. Multiple functions of hybrids composed of modified POSS and the significant roles of POSS in bio-related polymeric materials for solving critical problems in conventional 19 F MR probes and for realizing new sensing technologies are demonstrated. Next, solid-state luminescent materials containing o-carborane and group 13 element-blocks are discussed. The materials' highly efficient emission in the solid state and their origins are explained. Furthermore, stimuli-responsive luminescent chromism is summarized. The sensing mechanisms and the application of these materials as sensors are presented in this study. In the last part, we mention optically active element-blocks containing chiral P-stereogenic phosphorus. In this review, the characteristics originating from each element-block are explained.
Although excimer emission is a useful luminescent phenomenon for fabricating optical sensors and probes, it is difficult to apply excimer emission for film sensors due to critical concentration ...quenching in the solid state. Therefore, robust molecular designs for solid-state excimer emission are still being explored. One of the key examples is the previously reported acridine-ethynyl-o-carborane AcE1, which showed a bright solid-state excimer emission assisted by characteristic CcageH···N interactions. In this paper, we report the newly synthesized acridine-diehynyl-o-carborane AcE2 and comprehensively compare it to AcE1. Both compounds had the same crystalline packing mode based on dimer formation, resulting in an efficient π-overlapping area and solid-state excimer emission. Variable-temperature photoluminescence (VT-PL) measurements revealed the consecutive thermochromic luminescence of these compounds. Finally, on the basis of the easily accessible spray-coating method, we constructed the thermochromic luminescent sensors on quartz substrates. According to the mechanistic studies, it is demonstrated that the design strategy based on a dimer-induced solid-state excimer should have great potential for applications as a molecular thermometer.
Polysilsesquioxanes are regarded as organicinorganic hybrid materials at a molecular level. We can readily tune the properties of the materials for realizing the desired ones by changing the contents ...or types of organic components. In addition, the hierarchical structures have potential for generating further characteristics distinctly different from those of the constituents. From this viewpoint, polyhedral oligomeric silsesquioxane (POSS) is attractive as a cornerstone in highly ordered materials. In this review, we survey recent studies on modified POSS-based functional materials and particularly explain the design concepts for applying the significant characteristics of POSS for the material properties. In the initial sections, we introduce the examples concerning intrinsic properties of POSS such as thermal stability, mechanical property, and structural features. In the latter sections, we describe the application of POSS-based materials for bio-relating functional materials. We describe the validity of POSS for molecular designing of the advanced imaging tools.
We survey recent studies about modified POSS-based functional materials and particularly explain the design concepts for applying the significant characteristics of POSS for the material properties. The preparation and characterization methods for key compounds are also described.
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