Observation of a Mixed-Metal Transition in Heterobimetallic Au/Ag Dicyanide Systems

Abstract

Crystals of the mixed-metal heterobimetallic Au/Ag dicyanide complex, K[AuxAg1-x(CN)2] (x = 0-->1), were obtained by slow evaporation. The mixed-metal complex K[Au0.44Ag0.56(CN)2] crystallizes in a rhombohedral crystal system, space group R. The crystal structure consists of layers of linear chains of Au(CN)2- and Ag(CN)2- ions and K+ ions that connect the layers through the N atoms. The excitation and emission spectra of single crystals of K[AuxAg1-x(CN)2] were recorded at 4.2-180 K using excitation wavelengths between 230 and 260 nm. Two emission bands due to Ag-Au interactions were observed at 343 and 372 nm. Lifetime measurements indicate the shorter-wavelength emission corresponds to fluorescence and the longer-wavelength band is phosphorescence. These new emission bands are not seen in the pure K[Ag(CN)2] or pure K[Au(CN)2] crystals. Extended Hückel calculations show that the LUMO of the mixed-metal system is bonding while the HOMO is antibonding or very weakly bonding. Moreover, excited-state extended Hückel calculations indicate the formation of exciplexes with shorter metal-metal distances and higher metal-metal overlap populations than the corresponding ground-state oligomers. The luminescence is assigned to a mixed-metal transition from a molecular orbital with Au character to a molecular orbital with Ag character.

Luminescence and simulation of mixed metal nanoclusters of dicyanoargentate(I) and dicyanoaurate(I) in alkali halides

“…Such phenomena are related to the heterometallic and homometallic metal-metal interactions [14] in these clusters. These metal-metal interactions are observed in the pure crystal case [7][8][9], in solution [6], and in doped alkali halides [5,10,12,13]. Recently, mixed nanoclusters of Au and Ag or Pt doped in zeolites have been reported to have enhanced catalytic effects on CO oxidation reactions in comparison to catalytic systems with only Au, Ag, or Pt nanoclusters present [15][16][17][18].…”

“…One important area of nanotechnology is the study of the clusters of d 8 and d 10 metal cyanide complexes [5][6][7][8][9][10][11][12][13][14]. These clusters show applications in optical memory [11], energy transfer [6], and emission tunability.…”

Photophysical Investigation of Silver/Gold Dicyanometallates and Tetramethylammonium Networks: An Experimental and Theoretical Investigation

“…Indeed, a prominent structural feature of both K 3 [Me 4 N] 2 [Au(CN) 2 ] 5 and K 3 [Me 4 N] 2 [Ag(CN) 2 ] 5 are the close metal ··· metal distances (Au ··· Au = 3.183 Å and Ag ··· Ag = 3.086 Å), falling well within the range of the sum of the van der Waals radii for argentophilic and aurophilic interactions , . Because of these close metal‐metal distances we can expect to observe MMLCT emission bands associated with metallophilic interactions in the luminescence spectra such as those observed in crystals of KAu(CN) 2 and KAg(CN) 2 …”

Stepwise Construction of Au4Ag2Cu2 Coinage Rings Supported by Linear Tetraphosphine Ligands

“…[1][2][3][4][5][6][7][8] In particular, appropriately designed heterometallic coinage clusters have the diverse potential to function as building blocks for molecular-based electronic devices and nanostructured materials including biological sensors and industrial catalysts. [4][5][6][7][8] 12 ] would be an exclusive one. [9] Since such molecular compounds have hardly been synthesized by usual self-assembling procedures, stepwise synthetic techniques with multidentate supporting ligands are highly required.…”

“…

Rapidly growing attention has been focused on homoand heterometallic compounds of coinage metals because of their versatile structures relating to d 10 closed-shell metallophilic attraction and photophysical properties concerning cluster-centered transitions. [1][2][3][4][5][6][7][8] In particular, appropriately designed heterometallic coinage clusters have the diverse potential to function as building blocks for molecular-based electronic devices and nanostructured materials including biological sensors and industrial catalysts. [4][5][6][7][8] However, successful examples that include three coinage metals in one molecule have been extremely limited; the supramolecular Au I Ag I Cu II compound with d-penicillamine (d-penH 2 ) bridging ligands, [Au I 6 Ag I 8 Cu II 6

…”