Introduction of a Biphenyl Moiety for a Solvent-Responsive Aryl Gold(I) Isocyanide Complex with Mechanical Reactivation

Postsynthetic Modification of Half-Sandwich Ruthenium Complexes by Mechanochemical Synthesis

A mild and environmentally friendly method to synthesize half-sandwich ruthenium complexes through the Wittig reaction between an aldehyde-tagged half-sandwich ruthenium complex and phosphorus ylide mechanochemically is reported herein. The mechanochemical synthesis of valuable half-sandwich ruthenium complexes resulted in a fast reaction, good yield with simple workup, and the avoidance of harsh reaction conditions and organic solvents. The synthesized half-sandwich ruthenium complexes exhibited high catalytic activity for transfer hydrogenation of ketones using 2-propanol as the hydrogen source and solvent. Density functional theory was carried out to propose a mechanism for the transfer hydrogenation process. The modeling suggests the importance of the labile p-cymene ligand in modulating the reactivity of the catalyst.

A polymorphic pentiptycene-containing gold(I) isocyanide complex: solvent- and conformation-dependent supramolecular luminescence

Four crystalline (pseudo)polymorphs of [Ph-Au-C[triple bond, length as m-dash]N-Phip-OC8H17] (1), where Phip = central phenylene of pentiptycene, reveal that the π-backbone conformation relative to the AuAu bonding axis is important in determining the energy and efficiency of the supramolecular luminescence, which offers mechanistic insights into the luminescence mechanochromism and vapochromism and the solvent-dependent aggregation-induced emission (AIE) of 1.

Synthesis and Photoluminescence of Tetracyanidonitridorhenium(V) Complexes with Five-Membered N-Heteroaromatic Ligands and Photoluminescence-Intensity Change

Novel tetracyanidonitridorhenium(V) complexes with five-membered N-heteroaromatic ligands, (PPh₄)₂[ReN(CN)₄L] [L = imidazole (Him) (2), 1-methylimidazole (Mim) (3), and pyrazole (pyz) (4)] and (PPh₄)₂[ReN(CN)₄L]·L [L = Him (5) and Mim (6)], were synthesized by the reactions of (PPh₄)₂[ReN(CN)₄] (1) with Him, Mim, and pyz, and their structures were determined by single-crystal X-ray analysis. The complexes 2, 3, 4, and 6 showed intense photoluminescence, with the emission quantum yields (Φ_em) being 0.65-0.75 in the solid state at 296 K. In contrast, the Φ_em and τ_em values of 5 are significantly smaller and shorter, respectively, than the relevant values of 2. The interconversion reactions among 1, 2, and 5 accompanied by large photoluminescence-intensity changes were accomplished by solvent-free reactions and exposure of water. The mechanochemical reaction of 2 with 1 mol equiv of Him in the solid state gave 5. Complex 5 was also obtained by the mechanochemical reaction of 1 with 2 mol equivalents of Him in the solid state. By placing solid of 5 in water, the solid showed intense photoluminescence to give 2. Complex 1 was produced under vacuum at 185 °C from 2 or 5.

The Impact of Crystal Packing and Aurophilic Interactions on the Luminescence Properties in Polymorphs and Solvate of Aroylacetylide-Gold(I) Complexes

The influence of the chemical substitution, crystal packing, and aurophilic interactions of the gold(I) acetylide complexes of the type (ArCOC≡C)_n AuPEt₃ (n=1,2) on their luminescent properties were examined. All described complexes undergo ligand scrambling in solution, which results in the formation of stable, easily isolated crystals that contain [ArCO(C≡C)_n ]₂ Au^- (Et₃ P)₂ Au⁺ homoleptic species. In particular, we observed that the (benzoylacetylide)gold(I) complex yields three crystal forms with strikingly different luminescence properties. We monitored the conversion pathway for these forms: an orange luminescent form of homoleptic complex upon drying undergoes spontaneous transformation to bright green fluorescent form and finally to the weakly blue emissive one. In addition, we report a rare example of a helical arrangement of Au⋅Au⋅Au chains that are observed for the first time in acetylide gold(I) complexes in the case of heteroleptic (benzoylacetylide)gold(I) complex. This is a very rare case in which crystal structures and ensuing electronic properties of the heteroleptic and Au^I complexes could be directly compared.

4-Pyridylisocyanide gold(i) and gold(i)-plus-silver(i) luminescent and mechanochromic materials: the silver role

X-Ray and DFT studies support that the red-shift of luminescence from [AuAr(CNPy-4)] (Ar = C₆F₅, C₆F₃Cl₂-3,5) to [Ag[AuAr(CNPy-4)]₂](BF₄) is not due to non-existent Au⋯Ag interactions but to adoption of structures with shorter Au⋯Au distances.

Crystallization-Induced Emission Enhancement of a Deep-Blue Luminescence Material with Tunable Mechano- and Thermochromism

Organic luminescent materials with the ability to reversibly switch the luminescence when subjected to external stimuli have attracted considerable interest in recent years. However, the examples of luminescent materials that exhibit multiresponsive properties are rarely reported. In this work, a new stimuli-responsive dye P1 is designed and synthesized with two identical chromophores of naphthalimide, one at each side of an amidoamine-based spacer. This amide-rich molecule offers many possibilities for forming intra- and intermolecular hydrogen bond interactions. Particularly, P1 has an intrinsic property of cocrystallizing with methanol. Compared with the pristine P1 sample, the as-prepared two-component cocrystalline material displays an exceptive deep-blue emission, which is extremely rare among naphthalimide-based molecules in the solid state. Furthermore, the target material exhibits an obvious mechanochromic fluorescent behavior and a large spectral shift under force stimuli. On the other hand, the cocrystalline material shows an unusual "turn off" thermochromic luminescence accompanied by solvent evaporation. Moreover, using external stimuli to reversibly manipulate fluorescent quantum yields is rarely reported to date. The results demonstrate the feasibility of a new design strategy for solid-state luminescence switching materials: the incorporation of solvents into organic compounds by cocrystallization to obtain a crystalline state luminescence system.

Distinct Mechanoresponsive Luminescence, Thermochromism, Vapochromism, and Chlorine Gas Sensing by a Solid-State Organic Emitter

In this study, we report a synthetically simple donor-acceptor (D-A)-type organic solid-state emitter 1 that displays unique fluorescence switching under mechanical stimuli. Orange and yellow emissive crystals of 1 (1O, 1Y) exhibit an unusual "back and forth" fluorescence response to mechanical force. Gentle crushing (mild pressure) of the orange or yellow emissive crystal results in hypsochromic shift to cyan emissive fragments (λ_em = 498-501 nm) with a large wavelength shift Δλ_em = -71 to -96 nm, while further grinding results in bathochromic swing to green emissive powder λ_em = 540-550 nm, Δλ_em = +40 to 58 nm. Single-crystal X-ray diffraction study reveals that molecules are packed by weak interactions, such as C-H···π, C-H···N, and C-H···F, which facilitate intermolecular charge transfer in the crystal. With the aid of structural, spectroscopic, and morphological studies, we established the interplay between intermolecular and intramolecular charge-transfer interaction that is responsible for this elusive mechanochromic luminescence. Moreover, we have also demonstrated the application of this organic material for chlorine gas sensing in solid state.

Low-temperature-selective luminescent mechanochromism of a thienyl gold isocyanide complex

The low-temperature-selective mechanochromism of a thienyl gold(i) isocyanide complex is reported.