nescence changes from blue to yellow after grinding. Like other such compounds, its original lumi-nescent state is restored upon dissolution and recrystallization, and this process could be repeated for 20 cycles without any decrease in luminescence. Structural and spectroscopic studies indicate that the long-lived blue emission in the crystal is intramolecular in origin and phos-phorescent (a localized intraligand π-π* transition), whereas the yellow emission appears to arise from an amorphous phase characterized by aurophilic interactions: intermolecular interactions between gold atoms.-PDS

In the fields of fluid dynamics, aeronautical engineering, environment engineering, and energy technology, it is critical to accurately measure the physical parameters of a material surface. [1] Optoelectronic devices have generally been employed as temperature and pressure sensors. [2] However, their sensing area is limited to a single point on a surface. There is a need to measure entire surfaces and obtain multidimensional data for mapping surfaces. There are high expectations that materials for surface measurements, such as temperature and pressure-sensitive dyes, will overcome this intrinsic limitation of optoelectronic devices.We seek to design temperature-sensitive dyes using luminescent lanthanide complexes. Lanthanide complexes exhibit characteristic luminescence with narrow emission bands (full width at half maximum, fwhm < 10 nm) and long emission lifetimes (> 1 ms), [3] which make them suitable for use in sensing devices. In 2003, Amao and co-workers reported the first temperature-sensitive dye that employed an Eu III complex in a polymer film. [4] Khalil et al. demonstrated the high performance of an Eu III complex for a temperature-sensitive paint (temperature sensitivity: 4.42 % 8C À1 ). [5] We have reported a Tb III complex, Tb(hfa) 3 -(H 2 O) 2 (hfa: hexafluoro acetylacetonato), that is suitable as a temperature-sensing probe since it exhibits effective energy back transfer (BEnT) from the emitting level of the Tb III ion to the excited triplet state of the hfa ligand. [6] Since BEnT depends on the energy barrier of the process, the emission intensity varies with temperature.To improve the thermosensing performance, it is necessary to develop a thermostable structure for high-temperature sensing and to implement a dual sensing unit for a high sensing ability. First, we focused on a lanthanide coordination polymer to produce a thermostable structure. Thermally stable coordination polymers and metal-organic frameworks have been widely studied. [7] Carlos and co-workers recently reported novel three-dimensional lanthanide-organic frameworks with 2,5-pyridinedicarboxylic acid. [8] Marchetti et al. developed thermostable Eu III coordination polymers with 4acyl-pyrazolone ligands. [9] Here, we consider that introducing Tb III ion and hfa ligands to coordination polymer frameworks will produce a Tb III coordination polymer that can be used as a temperature-sensing probe. The triplet state of hfa (22 000 cm À1 ) is very close to the emitting level of the Tb III ion (20 500 cm À1 ), resulting in effective EnT1 and BEnT and thus high-performance thermosensing dyes (Figure 1 a). We also selected low-vibrational frequency phosphane oxide [10] as the linking part in the Tb III coordination polymer because lanthanide complexes with high emission quantum yields composed of hfa and bidentate phosphane oxide ligands have been reported. [11] Second, we attempted to impart ratiometric temperature sensing by using luminescent Eu III and Tb III ions in the frameworks of the coordination polymer to realize a high th...

A new material concept of soft crystals is proposed. Soft crystals respond to gentle stimuli such as vapor exposure and rubbing but maintain their structural order and exhibit remarkable visual changes in their shape, color, and luminescence. Various interesting examples of soft crystals are introduced in the article. By exploring the interesting formation and phase‐transition phenomena of soft crystals through interdisciplinary collaboration, new materials having both the characteristics of ordered hard crystals and those of flexible soft matter are expected.

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Extensive studies of luminescent copper(I) complexes were conducted, revealing that some of them exhibit interesting chromic luminescence in response to external stimuli such as temperature, vapor, light, and mechanical force. In this review, recent progress in the field of luminescent chromic copper(I) complexes is discussed. Tetranuclear copper(I) clusters with a cubane-type {Cu 4 I 4 } core are the most prominent group, which shows thermochromic, vapochromic, and mechanochromic luminescence, and their responsiveness to external stimuli greatly depends on coordinating organic ligands. Coordination polymerization of copper(I) cluster cores using organic linkers provides new luminescent thermochromic and vapochromic materials with behavior strongly dependent on the flexibility of the framework. The diversity of the cluster core structure and the lability to the ligand exchange are also useful to derive unique behaviors of photochromic and vapochromic response. In addition to such stimuli-responsive luminescence, the mechanochemical synthesis of highly luminescent copper(I) complexes is introduced, since the phenomenon is closely related to the mechanochromic luminescence and this approach allows the preparation of an emission layer directly on the substrate.

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A cyclometalated dinuclear platinum(II) complex bridged with pyridine-2-thiolate ions, [Pt2(ppy)2(pyt)2] (Hppy = 2-phenylpyridine, Hpyt = pyridine-2-thiol) and its oxidized platinum(III) complex, [Pt2Cl2(ppy)2(pyt)2] have been synthesized and characterized. The divalent complex exhibits intense red luminescence both in solution and in the solid states. Corresponding to the short Pt···Pt distance (2.849(1) Å) for [Pt2(ppy)2(pyt)2], the reversible conversion between the divalent and trivalent complexes occurs easily with appearance and disappearance of the luminescence.

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