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Two heteroctanuclear Au4Ag4 cluster complexes of 4,5-diethynylacridin-9-one (H2L) were prepared through the self-assembly reactions of [Au(tht)2](CF3SO3), Ag(tht)(CF3SO3), H2L and PPh3 or PPh2Py (2-(diphenylphosphino)pyridine). The Au4Ag4 cluster consists of a [Au4L4]4− and four [Ag(PPh3)]+ or [Ag(PPh2Py)]+ units with Au4L4 framework exhibiting a twisted paper clip structure. In CH2Cl2 solutions at ambient temperature, both compounds show ligand fluorescence at ca. 463 nm as well as phosphorescence at 650 nm for 1 and 630 nm for 2 resulting from admixture of 3IL (intraligand) of L ligand, 3LMCT (from L ligand to Au4Ag4) and 3MC (metal-cluster) triplet states. Crystals or crystalline powders manifest bright yellow-green phosphorescence with vibronic-structured emission bands at 530 (568sh) nm for complex 1 and 536 (576sh) nm for complex 2. Upon mechanical grinding, yellow-green emission in the crystalline state is dramatically converted to red luminescence centered at ca. 610 nm with a drastic redshift of the emission after crystal packing is destroyed. [ABSTRACT FROM AUTHOR]

A feasible synthetic approach to achieve Ag8, Ag16 and Ag29 silver(i) nanoclusters is reported by the use of 1,8-diethynyl-9H-carbazole (H3decz) as a directing ligand. The silver(i) nanoclusters exhibit room-temperature photoluminescence in both solution and solid state. The emission band shows stepwise red-shifts from visible to near-infrared region with the increase of cluster nuclearity following 2 (Ag8, λem = 571 nm) →3 (Ag16, λem = 651 nm) →4 (Ag29, λem = 916 and 875sh nm) in fluid CH2Cl2. [ABSTRACT FROM AUTHOR]

[Display omitted] • The origin of luminescence thermochromism is briefly discussed. • The relationship between clusters and their electronic structures is described in detail. • The mechanism of luminescence thermochromism in silver clusters is highlighted. • The outcomes and important future aspects of silver(I) cluster are proposed. Stimuli-responsive materials have garnered significant attention in technology, sensors, and biological applications because of their quick response to various external factors. These include light, temperature, change in solvent, pressure fluctuations, mechanical friction, and alteration in pH values. Luminescence thermochromism, in particular, refers to the ability of materials to vary the color of their fluorescence emission as a function of temperature. Interestingly, silver clusters ranging from discrete to higher-dimensional structures show luminescence thermochromism due to strong argentophilic interactions and protecting ligands, affecting their emission position, intensity, and lifetime. These ultra-small materials possess superior photostability, biocompatibility, and low toxicity, holding great promise for potential applications. This review article provides valuable insights into the structural features of silver clusters for designing and developing luminescent thermochromic silver clusters. Additionally, this highlights the mechanisms behind luminescence thermochromism, including structural rigidity, competition between bathochromic and hypsochromic shifts, and thermally activated delayed fluorescence. The aim of this review is to inspire new ideas and concepts for developing new luminescent thermochromic silver cluster materials. [ABSTRACT FROM AUTHOR]