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Reaction of [Au(tht) 2 ](ClO 4 ) (tht = tetrahydrothiophene), [Cu(CH 3 CN) 4 ](ClO 4 ), 3,6-di- tert -butyl-1,8-diethynyl-9 H -carbazole (H 3 decz), and bis(2-diphenylphosphinophenyl)ether (POP) in the presence of triethylamine (NEt 3 ) gave the cluster complex Au 4 Cu 2 (decz) 2 (POP) 2 as yellow crystals. As revealed by X-ray crystallography, the Au 4 Cu 2 cluster exhibits scissor-like structure sustained by two decz and two POP ligands and stabilized by Au-Cu and Au-Au interactions. The Au 4 Cu 2 cluster shows bright yellow to orange photoluminescence upon irradiation at >300 nm, arising from 3 [π (decz)→5d (Au)] 3 LMCT (ligand-to-metal charge transfer) and 3 [π→π* (decz)] 3 IL (intraligand) triplet states as revealed by theoretical and computational studies. When it is mechanically ground, reversible phosphorescence conversion from yellow to red is observed owing to more compact molecular packing and thus stronger intermetallic interaction. Variable-temperature luminescence studies reveal that it displays distinct red-shifts of the emission whether the temperature is elevated or lowered from ambient temperature, suggestive of exceptional thermochromic phosphorescence characteristics.

Two heteroctanuclear Au 4 Ag 4 cluster complexes of 4,5-diethynylacridin-9-one (H 2 L) were prepared through the self-assembly reactions of [Au(tht) 2 ](CF 3 SO 3 ), Ag(tht)(CF 3 SO 3 ), H 2 L and PPh 3 or PPh 2 Py (2-(diphenylphosphino)pyridine). The Au 4 Ag 4 cluster consists of a [Au 4 L 4 ] 4- and four [Ag(PPh 3 )] + or [Ag(PPh 2 Py)] + units with Au 4 L 4 framework exhibiting a twisted paper clip structure. In CH 2 Cl 2 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 3 IL (intraligand) of L ligand, 3 LMCT (from L ligand to Au 4 Ag 4 ) and 3 MC (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.