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Knots containing metal atoms as part of their continuous strand backbone are termed as metallaknots. While several metallaknots have been synthesized through one-pot self-assembly, the designed synthesis of metallaknots by controlling the arrangement of entanglements and strands connectivity remains unexplored. Here, we report the synthesis of metallaknots composed with Au(I)-bis(acetylide) linkages and templated by Cu(I) ions. Varying the ratio of the building blocks results in the switchable formation of two trefoil knots with different stoichiometries and symmetries ( C 2 or D 3 ) and an entangled metalla-complex. While the entangled complex formed serendipitously, the strand ends can be subsequently linked through coordinative closure to generate a 4 1 metallaknot in a highly designable fashion. The comparable structural characteristics of resulting metalla-complexes allow us to probe the correlations between their topologies and photophysical properties, showing the backbone rigidity of knots endows complexes with excellent phosphorescent properties. This strategy, in conjunction with the coordinative closure approach, provides a straightforward route for the formation of highly phosphorescent metallaknots that were previously challenging to access., Competing Interests: Competing interests statement:The authors declare no competing interest.

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.

In this work, rational design of highly soluble and phosphorescent Ag-Au cluster complexes with exceptional [2]catenane structures is conducted using 1,8-diethynyl-9 H -carbazole (H 3 decz) as a rigid U-shaped ligand with a distinguished hole-transport character. The self-assembly reaction of H 3 decz, Au + , and Ag + generated phosphorescent Ag 4 Au 6 cluster 1 (Φ em = 0.22 in CH 2 Cl 2 ) with H 2 decz - having a free ethynyl (-C≡CH) group. When the four free C≡CH groups in the Ag 4 Au 6 complex 1 are further bound to four (PPh 3 )Au + and four (PPh 3 )Ag + moieties through M-acetylide linkages, the formation of Ag 8 Au 10 cluster 2 not only eliminates nonradiative ethynyl C-H vibrational deactivation process but also improves dramatically the molecular rigidity so that the phosphorescent efficiency of the Ag 8 Au 10 cluster 2 (Φ em = 0.63) is nearly 3 times that of the Ag 4 Au 6 cluster 1 . The Ag 8 Au 10 cluster structure is further rigidified using diphsophine Ph 2 P(CH 2 ) 4 PPh 2 (dppb) in place of PPh 3 so that the phosphorescence of the Ag 8 Au 10 cluster 3 (Φ em = 0.77) is more efficient than that of 2 . Making use of the Ag 8 Au 10 clusters as phosphorescent dopants, high-efficiency solution-processed organic light-emitting diodes (OLEDs) were achieved with current efficiency (CE) and external quantum efficiency (EQE) of 47.2 cd A -1 and 15.7% for complex 2 and 50.5 cd A -1 and 14.9% for complex 3 .

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.