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

Abstract

We report on the structural and luminescence properties of a series of d10 dicyanometallate compounds of formula K3(Me4N)2[M(CN)2]5 (M = Au and Ag). These double salts form isostructural 3D networks in which metallophilic bonding is observed between [M(CN)2]– subunits. Despite their similar structural features, stark differences in luminescence behavior between these crystals are observed. At room temperature Au‐containing crystals are bright emitters at 405 nm while the Ag analog is a weak emitter at 470 nm. At low temperatures the emission of both complexes becomes intense under UV light at a wavelength of 416 nm. Using lifetime measurements, X‐ray crystallography, and Density Functional Theory (DFT) calculations we have been able to assign these emission bands as a transition from a metal‐metal to ligand charge transfer.

Innovative Molecular Design Strategies in Materials Science Following the Aurophilicity Concept

“…Work on dicyanometalates [M­(CN) 2 ] has shown similar effects for both M = Ag and M = Au . Recent work with systems featuring both alkali and quaternary ammonium cations has further broadened the scope of these interactions and demonstrated that silver­(I) and gold­(I) centers induce very different photophysical performances …”

Synthesis and Luminescence of Optical Memory Active Tetramethylammonium Cyanocuprate(I) 3D Networks

“…This splitting is in agreement with the structural data of 1 which show two types of cyanides: those that bridge individual {Cu 2 (CN) 4 ] 2− rhomboids and those that bridge a {Cu 2 (CN) 4 ] 2− rhomboid with a trigonal planar Cu(I) center. We have established in other systems that the bidentate nature of the μ 2 -CN decreases the cyanide bond order, lowering the vibrational frequency in comparison to the bridging cyanide [31]. Thus, for 1 , we assign the ⱱ s (C≡N) at 2114 cm −1 and 2070 cm −1 to the bridging μ 1− and μ 2− CN group, respectively.…”

“…The quaternary ammonium ion Me 4 N + is not redox active and, therefore, is unable to participate in interionic charge transfer behavior, leaving only the CuCN 2 − subunits as the emissive species. We have observed interesting emissive behavior in analogous AuCN 2 − /AgCN 2 − materials but have not as yet investigated their optical memory potential [31]. Herein, we report on the structure and optical memory of two new 3D networks [NMe 4 ] 2 [Cu(CN) 2 ] 2 •0.25H 2 O ( 1 ) and [NMe 4 ][Cu 3 (CN) 4 ] ( 2 ).…”

Molecular gold strings: aurophilicity, luminescence and structure–property correlations

“…On the other hand, the low steric demand, the simple linear structure and not least the hydrogen bond acceptor ability of the cyanides facilitate a self-aggre-gation process. 129,130 In this context, the Attar and Balch groups investigated the formation and luminescence of dicyanoaurate strings comprising common ammonium counter cations. 131 ] (7d) salts, only the latter does not form a polymeric string in the solid state, presumably due to a lack of N-H groups suitable for hydrogen bonding to the cyanide moieties of the anions.…”