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Vapochromic materials that exhibit color/luminescence changes induced by vapor exposure have attracted considerable attention. Herein, we report the grinding- and heating-induced ON-OFF switching of the vapochromic behavior of [Pt(ppyCl

Molecular crystals composed of platinum(ii) complexes exhibited elastic deformation without cracking and bright assembly-induced emission with an extremely high emission quantum yield of 0.94.

In this chapter, the characteristics and potentials of “soft crystals” are compared with those of conventional hard crystals after providing a historical background. In addition, representative examples of “soft crystals” are discussed, and their thermodynamic models are qualitatively described.

Superelasticity is the ability of a plastically deformed solid to spontaneously recover its shape upon unloading due to stress loading. From its discovery in Au–Cd alloys in 1932, superelasticity had been believed to be limited to certain alloys until the discovery of “organic superelasticity” in 2014, which revealed it to be a general phenomenon observed in organic crystals along with ferroelasticity—reversible plastic deformability that is not accompanied by spontaneous shape recovery. In this chapter, we will introduce the discovery of organic superelasticity and the shape-memory effect, discuss superelasticity and ferroelasticity, and explain the properties and characteristics of various molecular crystals, including metal complexes. Furthermore, “organic superplasticity”—irreversible plastic deformation of several hundred percent or more, accompanied by the retention of crystallinity—has also been described.

Vapochromism, a phenomenon in which the color or luminescence color of a substance changes in response to gaseous molecules, has potential for developing sensor materials to detect harmful substances in the environment. In addition, vapochromism is scientifically interesting for the direct visualization of interactions between gases and solids. The crystals of metal complexes involve diverse and flexible electronic interactions, such as metal–metal and metal–ligand interactions. It is expected that slight structural changes in such crystals will lead to distinct color or emission color changes, thus achieving highly sensitive and selective vapochromic responses. Consequently, highly ordered and flexible response systems (i.e., soft crystals) can be constructed. This chapter introduces the interesting and attractive features of vapor-responsive soft crystals by discussing platinum complexes that show color and luminescence changes in dilute vapor atmospheres while maintaining an ordered structure, nickel(II) complexes that change magnetic properties in conjunction with a color change, and copper(I) complexes that change luminescence color in response to N-heteroaromatic vapors.

In this chapter, we aim to explain the chromic phenomena observed in “soft crystals”. Accordingly, the basic principles for comprehending the fundamental photophysical properties of molecular monomers, such as electronic absorption spectra and luminescence properties, are introduced. Moreover, the photophysical properties of molecular dimers and molecular crystals are explained in terms of intermolecular interactions in excited states.

A Pt(ii) complex bearing N-heterocyclic carbene exhibits chromic triboluminescence during the process of rubbing and also vapor exposure.

In this chapter, to design functions of soft crystals, the relationships between gentle stimuli and the corresponding responses are classified based on the photofunctions, and the key terms are linked and then systematized. Also, trials of functionalization based on soft crystal-related phenomena are introduced toward the functionalization of soft crystals.

“Soft crystals” typically undergo structural transformations in response to weak stimuli while maintaining the crystalline structural order. These transformations are often manifested as visible phenomena, such as changes in optical properties (color and/or luminescence color). In this chapter, the structural order, activation energy, and softness of “soft crystals” are compared with those of conventional hard crystals and soft materials, including liquid crystals and gels. Based on the results of this comparison, “soft crystals” are defined more precisely.

Interfacial electron flow is crucial for an efficient two-step (Z-scheme) solar water-splitting reaction. Dye-sensitization of a wide-gap oxide semiconductor has attracted considerable attention for decades as a means of producing hydrogen from water; however, it suffers from back electron transfer reactions at solid-solid and solid-solution interfaces. Here, we demonstrate that a combination of two nano-architectures, Ru-dye double layering and Pt cocatalyst intercalation to layered niobate semiconductor, effectively suppresses the back electron transfers at interfaces, leading to the complete oxidation of the [Co(bpy)(3)]-type electron mediator (bpy = 2,2'-bipyridine) as a result of efficient photocatalytic hydrogen production. Our systematic study on the Ru-dye double layers revealed that the double layering of two different Ru dyes and surface modification with the Zr4+ cation not only suppress the back electron transfer from an electron-injected semiconductor to oxidized dye but also accelerate the electron injection from the mediator to the oxidized dye. In addition, the re-reduction of the oxidized Co(III) mediator at the Pt cocatalyst surface was effectively suppressed by intercalation of Pt to the layered niobate semiconductor. The present work clearly shows that double nano-architectures controlling the surfaces of the semiconductor and cocatalyst have great potential for photo-induced charge separation at the solid-solution interface and expands the possibilities of layered semiconductor materials toward Z-scheme water splitting.

Computational approach to elucidate the phase transitions in lanthanide complexes will support to understand their electronic structure changes by weak stimuli such as gas adsorptions. There are no...

A new vapochromic, proton-conductive Pt(II) complex, [PtBr(tpypyH)]Br2 ([1Br-H]Br, tpypy = 2,2′: 6′,2′′-terpyridine-4′,4′′′-pyridine) was synthesized to improve the proton conductivity and thermal ...

Vapochromic crystals of Ni(II)-quinonoid complexes were theoretically investigated using density functional theory (DFT) calculations. Kato et al. previously reported that the purple crystals of a four-coordinate Ni(II)-quinonoid complex (

A series of σ-π extended octamethyltetrasilanes, which have phenothiazine, 9,9-dimethyl-9,10-dihydroacridine, or phenoxazine (

Single crystals showing elastic flexibility have attracted increasing attention as next-generation soft materials. Herein, we successfully developed a series of polyhalogenated platinum(II)–bipyridine complexes showing solvent-of-crystallisation-dependent elastic flexibility. Notably, methanol-solvated crystals were the first examples of flexible crystals showing assembly-induced luminescence arising from the triplet metal–metal-to-ligand charge transfer (3MMLCT) excited state. Furthermore, factors inducing elastic deformability based on the packing structures of the crystals were explored.

Perineal recurrence after brachytherapy is an exceedingly rare complication. Moreover, ductal adenocarcinoma is a rare histological variant of prostate cancer. Herein, we describe a case of perineal recurrence from ductal adenocarcinoma of prostate after low-dose-rate brachytherapy (LDR-BT) in a 65-year-old male patient. The patient had localized prostate cancer, for which he received LDR-BT; however, he experienced perineal recurrence 2 years after receiving LDR-BT. Surgical excision was attempted, but we were unable to remove the whole tumor, owing to invasion to surrounding tissue. Pathological examination of resected tumor showed ductal adenocarcinoma of the prostate. External beam radiation therapy and high-dose-rate brachytherapy (HDR-BT) were performed for residual tumor. Mild mediastinal lymph node swelling was observed during clinical course of the disease. Hence, androgen deprivation therapy was administered with abiraterone after radiation therapy, and prostate-specific antigen level decreased to undetectable level. Biochemical failure after transperineal brachytherapy for prostate cancer should be considered as a perineal recurrence.

A complex comprising one [Re(CO)

The vapochromic single-crystal-to-single-crystal (SCSC) transformation of a highly luminescent Pt

To investigate the effect of the surface structure of dye-sensitized photocatalyst nanoparticles, we prepared three types of RuII -photosensitizer (PS)-double-layered Pt-cocatalyst-loaded TiO2 nanoparticles with different surface structures, Zr-RuCP6 -Zr-RuP6 @N wt %Pt-TiO2 , RuCP6 -Zr-RuP6 @N wt %Pt-TiO2 , and RuCP2 -Zr-RuP6 @N wt %Pt-TiO2 (N=0.2, 1, and 5), and evaluated their photocatalytic H2 evolution activity in the presence of redox-reversible iodide as the electron donor. Although the driving force of the electron injection from I- to the photo-oxidized RuIII PS is comparable, the activity increased in the following order: RuCP2 -Zr-RuP6 @1 wt %Pt-TiO2 < RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 < Zr-RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 . The apparent quantum yield of Zr-RuCP6 -Zr-RuP6 @1 wt %Pt-TiO2 in the first hour reached 1 %. Zeta-potential measurements suggest that the surface Zr4+ -phosphate groups attracted I- anions to the nanoparticle-solution interface. Our results indicate that the surface modification of dye-sensitized photocatalysts is a promising approach to enhance photocatalytic activity with various redox mediators.

A series of assembled PtII complexes comprising N-heterocyclic carbene and cyanide ligands was constructed using different substituent groups, [Pt(CN)2 (R-impy)] (R-impyH+ =1-alkyl-3-(2-pyridyl)-1H-imidazolium, R=Me (Pt-Me), Et (Pt-Et), i Pr (Pt-i Pr), and t Bu (Pt-t Bu)). All the complexes exhibited highly efficient photoluminescence with an emission quantum yield of 0.51-0.81 in the solid state at room temperature, originating from the triplet metal-metal-to-ligand charge transfer (3 MMLCT) state. Their emission colors cover the entire visible region from red for Pt-Me to blue for Pt-t Bu. Importantly, Pt-t Bu is the first example that exhibits blue 3 MMLCT emission. The 3 MMLCT emission was proved and characterized based on the temperature dependences of the crystal structures and emission properties. The wide-range color tuning of luminescence using the 3 MMLCT emission presents a new strategy of superfine control of the emission color.

The emission spectrum of the platinum(II) bipyridine complex [Pt(CN)2(bpy)] (bpy = 2,2′-bipyridine) interestingly exhibits blue shift and peak broadening in crystal as temperature increases from 15...

Photocatalytic H2 evolution activity of three types of Ru(II)-photosensitizer(PS)-multilayered Pt-cocatalyst loaded TiO2 nanoparticles, RuCP2@Pt–TiO2, RuCP2–Zr–RuP6@Pt–TiO2, and RuCP2–Zr–RuP4–Zr–RuP6@Pt–TiO2 were investigated in the presence of the redox-reversible iodide electron donor aqueous solution. The apparent quantum yield (AQY) significantly improved by about 40 times by increasing the number of Ru(II)–PS layers and decreasing the loading amount of Pt cocatalyst on the surface of TiO2 nanoparticles. The zeta potential measurement suggests that the Zr4+ cations between the PS-layers acted as the iodide capturing sites to promote the electron donation. Photocurrent–voltage characteristics of the Ru(II)–PS-multilayered photoelectrodes RuCP2@TiO2–ITO, RuCP2–Zr–RuP6@TiO2–ITO, and RuCP2–Zr–RuP4–Zr–RuP6@TiO2–ITO in aqueous I−/I3− electrolyte solution revealed that the thicker Ru(II)–PS-layer with the Zr4+ cations contributes not only to suppressing the back electron transfer from Pt–TiO2 surface to the oxidized iodine species but also to enhancing the photoinduced electron injection.

We synthesized new oxygen-evolving molecular Ru(II) catalysts with one or two carbazole moieties on the axial pyridyl ligands, namely [Ru(bda)(cbz-py)(py)] and [Ru(bda)(cbz-py)2] [C1 and C2; bdaH2 = 2,2′-bipyridyl-6,6′-dicarboxylic acid, py = pyridine, and cbz-py = 9-(pyridin-4-yl)-9H-carbazole] to investigate the effect of cbz modification on the photophysical and catalytic properties of the well-known molecular catalyst [Ru(bda)(py)2] (C0). The initial oxygen-evolving catalytic activities of C1 and C2 were higher than that of C0 in both a chemical reaction driven by the strong oxidant (NH4)2[Ce(NO3)6] (CAN = ceric ammonium nitrate) and photochemical oxidation using a [Ru(bpy)3]2+ (bpy = 2,2′-bipyridine) photosensitizer with Na2S2O8 as the sacrificial oxidant. The higher activities were ascribed to the electron-withdrawing cbz groups, which promoted the radical coupling reaction to form a RuIV–O–O–RuIV species. A unique oxygen-evolution rate change behaviour was observed for both C1 and C2 in the presence of a large excess of CAN, suggesting the competitive oxidation of the cbz moiety during the chemical oxygen evolution reaction. This work suggests that the cbz modification of an oxygen evolution molecular catalyst is a promising approach for integrating the hole accumulator near the oxygen evolution catalytic centre.