Phosphorescence at Low Temperature by External Heavy-Atom Effect in Zinc(II) Clusters

Synthesis of ω-Hydroxy Fatty Acid Alkyl Esters by Macrocyclic Lactones Alcoholysis Catalyzed by Homoleptic and Heteroleptic Zinc Aryloxides

A series of zinc aryloxides, [Zn4(sal-Me)8]⋅2.5(C7H8) (1), [Zn4(sal-Me)8]⋅CH2Cl2 (2), [Zn4(μ3-OR)2(sal-R)6] (3) (for R=Me (0.51), Et (0.49)), [Zn4(μ3-OMe)4(sal-Me)4(HOMe)4] (4), [Zn(sal-Me)2(py)2]⋅THF (5), {[Zn(sal-Me)2(tmbpy)] ⋅ 2(C6H5CH3)}n (6), [Zn2(sal-Me)2(THF)2Cl2] ⋅ 0.5(C6H5CH3) (7), and [Zn4(μ3-OMe)2(sal-Me)4Cl2] (8) (Hsal-Me=methyl salicylate, py=pyridine, tmbpy=4,4'-trimethylenedipyridine) were obtained that have different nuclearities and central core topologies and contain ligands of different basicity and coordination abilities.

Dual Emission with Efficient Phosphorescence Promoted by Intermolecular Halogen Interactions in Luminescent Tetranuclear Zinc(II) Clusters

The development of Zn-based phosphorescent materials, associated with a ligand-centered (LC) transition, is extremely limited. Herein, we demonstrated dual emissions including fluorescence and phosphorescence in luminescent tetranuclear Zn(II) clusters [Zn4LI4(μ3-OMe)2X2] (HLI = methyl-5-iode-3-methoxysalicylate; X = I, Br, Cl), incorporating iodine-substituted ligands. Single-crystal X-ray structural analyses and variable-temperature emission spectra studies revealed the presence of iodine substitutions, and intermolecular halogen interactions produced the internal/external heavy-atom effects and yielded strong green phosphorescence with a long emission lifetime (λmax = 510-522 nm, Φem = 0.28-0.47, τav = 0.78-0.95 ms, at 77 K). This work provided a new example that the introduction of halogen interactions is an advantageous approach for inducing phosphorescence in fluorescent metal complexes.

Capturing the Trajectory of Metal-Ion-Cluster Formation: Stepwise Accumulation of Zn(II) Ions in a Robust Coordination Space Formed by a Rigid Tridentate Carboxylate Ligand

Organic ligand-directed synthesis of metal-ion clusters with a well-defined number and arrangement of metal ions is an important subject toward the development of functional inorganic-organic nanohybrids. Here we report the synthesis of multinuclear Zn-oxo clusters using a triptycene-based rigid ligand (H₃L) featuring three metal-coordination sites arranged in a triangular shape. Upon complexation of H₃L with zinc acetate dihydrate, a decanuclear Zn-oxo cluster and multinuclear Zn-oxo clusters with a smaller number of Zn(II) ions were formed as the final product and its intermediates, respectively. A comparison of the X-ray structure of the final product with those of the intermediates revealed the cluster-formation process, where four triptycene ligands preorganize to form a robust coordination space to which Zn(II) ions accumulate in a stepwise manner. This stepwise metal-ion accumulation, along with the formation of a large tetrahedral decanuclear Zn-oxo cluster, highlights the potential of ligand design using 1,8,13-substituted triptycenes for the development of various metal-ion clusters.

Chaotic Organic Crystal Phosphorescent Patterns for Physical Unclonable Functions

Since the 4th Industrial Revolution, Internet of Things based environments have been widely used in various fields ranging from mobile to medical devices. Simultaneously, information leakage and hacking risks have also increased significantly, and secure authentication and security systems are constantly required. Physical unclonable functions (PUF) are in the spotlight as an alternative. Chaotic phosphorescent patterns are developed based on an organic crystal and atomic seed heterostructure for security labels with PUFs. Phosphorescent organic crystal patterns are formed on MoS₂ . They seem similar on a macroscopic scale, whereas each organic crystal exhibits highly disorder features on the microscopic scale. In image analysis, an encoding capacity as a single PUF domain achieves more than 10¹⁷ on a MoS₂ small fragment with lengths of 25 µm. Therefore, security labels with phosphorescent PUFs can offer superior randomness and no-cloning codes, possibly becoming a promising security strategy for authentication processes.

Diversifying the luminescence of phenanthro-diimine ligands in zinc complexes

Strongly blue fluorescent 1-phenyl-2-(pyridin-2-yl)-1H-phenanthro[9,10-d]imidazole (L1) is a facile block for the construction of multichromophore organic molecules, and simultaneously serves as a chelating diimine ligand.