Structural Characterization of a Base‐Stabilized [Zn<sub>2</sub>]<sup>2+</sup> Cation

Schulz, Stephan; Schuchmann, Daniella; Krossing, Ingo; Himmel, Daniel; Bläser, Dieter; Boese, Roland

doi:10.1002/anie.200902202

Cited by 81 publications

(85 citation statements)

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“…For the DNAstabilized silver clusters, pure solutions exhibit a single, narrow peak in the absorbance at an energy that depends on cluster size. [ 1 ] Corresponding to this qualitative spectral difference from BSA-Au 25 , our single emitter polarization measurements on Ag:DNA found no dependence on the excitation wavelength (within the tunable range of our laser, 575-595 nm). These marked differences in behavior may arise from the smaller s-d splitting in gold, which produces more complex optical properties in Au relative to Ag clusters due to mixing of d and s orbital transitions in the former.…”

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confidence: 81%

“…[ 1,2 ] Because these small clusters can be fl uorescent, [ 3 ] with high quantum yields, and because the specifi c DNA sequence strongly infl uences the optical properties of the stabilized clusters, these "Ag:DNAs" are beginning to be intensively studied for applications in sensing [ 4,5 ] and biolabelling. [ 6 ] Such silver "nanoclusters", with just tens of metal atoms, are in a different size regime from metal nanoparticles of several to tens of nanometers dimensions that are the focus of current nanoplasmonics research.…”

Section: Introductionmentioning

confidence: 99%

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Polarization Resolved Measurements of Individual DNA‐Stabilized Silver Clusters

Markešević

Oemrawsingh

Schultz

et al. 2014

Advanced Optical Materials

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hybrid materials at truly nanoscale dimensions, enabling functionality at enormously high spatial densities. [ 11,12 ] Given their nanometer size scale, such clusterbased materials may also combine desirable properties usually associated with the molecular regime, such as high fl uorescence quantum yields and large Stokes shifts, with emergent near-fi eld interactions arising from the polarizability of free electron systems, as currently exploited in surface-enhanced Raman spectroscopy [ 13 ] (SERS), and plasmonic coupling schemes with metal nanoparticles. [ 12 ] Despite the numerous Ag:DNA [ 3,[14][15][16][17][18][19] studies, little is known about the mechanism by which fl uorescent excitation and emission occur. It was previously established in the literature on small metal clusters that the excitation energies are considerably up-shifted from the particle-in-box energies, due to Coulomb interactions that lead to collective, phased oscillation of the cluster's valence electrons. [ 20,21 ] Recent experimental works [ 22,23 ] indicate that fl uorescent Ag:DNA contains a neutral silver core that is surrounded by base-bound silver ions. This arrangement is analogous to the known structure of gold clusters that are stabilized by small organic ligand molecules, [24][25][26] which possess both transitions associated with the gold core, and transitions involving charge transfer between the gold core and the surrounding ligands plus their directly attached gold atoms. [ 25,26 ] For Ag:DNAs, the specifi c mode of cluster-DNA binding is unknown, but given the existence of a neutral silver core one might expect both core-centered transitions and charge transfer transitions between the core and baseattached silver ions.In the case of such silver core-ligand transitions, small variations in the specifi c conformation of the DNA might be expected to affect directions of transition dipole moments. Thus it is of great interest to study individual Ag:DNAs under conditions that minimize environmental fl uctuations, using techniques that can probe such orientational effects.In this paper, we present single-cluster optical studies of Ag:DNAs that investigate both their response as a function of the polarization of the excitation light and the polarization of the light they emit. Single particle polarization studies have previously been used to investigate individual fl uorescent molecules, providing insight into the orientation of the emitters in the surrounding medium [ 27,28 ] as well as photophysical events of single molecules, such as rotational jumps of a single Polarization-resolved excitation and emission measurements on individual 10-15 atom silver clusters formed on DNA are presented. The emission is highly linearly polarized, typically around 90% for all emitters, whereas the polarization dependence of the excitation strongly varies from emitter to emitter. These observations support the hypothesis that the luminescence arises from collective electron oscillations along rod-shaped silver clusters, whereas the excitation ...

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confidence: 81%

Section: Introductionmentioning

confidence: 99%

Polarization Resolved Measurements of Individual DNA‐Stabilized Silver Clusters

Markešević

Oemrawsingh

Schultz

et al. 2014

Advanced Optical Materials

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“…The robustness, nonoxidizing and weak coordinating ability of the perfluoroalkoxyaluminate [Al(OC(CF 3 ) 3 ) 4 ]make it a very good candidate for stabilizing extremely sensitive and electrophilic cations, such as Ag(P 4 ) + 3 and related Ag salts, 4 P 5 X 2 + , 5 CI 3 + , 6 [Bi 4 OF 2 Cl 6 ] 2+ 7 and [Zn 2 ] 2+ . 8 Meanwhile, as is the case with perfluoroborates and carboranes, per/polyfluoroalkoxyaluminates are of great interest for catalysis, e.g. C-C bond formation, 1k enantioselective hydrogenation, 9 asymmetric cycloisomerization, 10 3 ) 4 ]show at least the same or superior catalytic activities than other types of WCAs.…”

Section: Introductionmentioning

confidence: 99%

Copper(ii) complexes incorporating poly/perfluorinated alkoxyaluminate-type weakly coordinating anions: Syntheses, characterization and catalytic application in stereoselective olefin aziridination

Li¹,

He²,

Khankhoje³

et al. 2011

Dalton Trans.

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The synthesis and characterization of a series of cationic copper(II) complexes of the type [Cu(NCR)(6)][Al(OC(CF(3))(2)R')(4)](2) (R = CH(3), Ph; R' = CF(3), Ph, PhCH(3)), incorporating poly/perfluoronated alkoxyaluminates as weakly coordinating anions (WCAs) is presented. Aziridination of various olefins, such as the unreactive olefins e.g. ethylhex-2-enoate and 1-decene, with N-tosyliminophenyliodinane catalyzed by [Cu(NCR)(6)][Al(OC(CF(3))(2)R')(4)](2) affords very good yields (up to 96%) and high TOFs (up to 5000 h(-1)) under mild conditions. Using disubstituted olefins as substrates, high stereoselectivities are obtained at room temperature. The to date highest cis : trans ratio (98 : 2) of the obtained aziridines is achieved for cis-stilbene in good yield (85%) as well as promising TOF (> 2000 h(-1)). The investigation of the solvent effect on yield and selectivity reveals that for certain oleophilic substrates (1-decene), less polar solvents, such as dichloromethane are a better choice than acetonitrile, which is commonly considered as the best solvent for olefin aziridination. Accordingly, a mechanism involving a paramagnetic copper nitrene intermediate with both concerted and stepwise pathways is proposed.

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“…Among the various bonding types, metal-metal (M-M) bonding has been one of the most important themes in inorganic chemistry since Cotton et al 3 [11][12][13][14][15][16][17][18][19][20][21][22][23] . However, these studies focus on the [Zn I 2 ] 2 þ dimeric species that are not sufficiently stable in air 11 .…”

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A multicentre-bonded [ZnI]8 cluster with cubic aromaticity

et al. 2015

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8 ] cluster fully occupy four bonding molecular orbitals and leave four antibonding ones entirely empty, leading to an extensive electron delocalization over the cube and significant stabilization. The bonding pattern of the cube represents a class of aromatic system that we refer to as cubic aromaticity, which follows a 6n þ 2 electron counting rule. Our finding extends the aromaticity concept to cubic metallic systems, and enriches Zn-Zn bonding chemistry.

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Structural Characterization of a Base‐Stabilized [Zn₂]²⁺ Cation

Cited by 81 publications

References 44 publications

Polarization Resolved Measurements of Individual DNA‐Stabilized Silver Clusters

Polarization Resolved Measurements of Individual DNA‐Stabilized Silver Clusters

Copper(ii) complexes incorporating poly/perfluorinated alkoxyaluminate-type weakly coordinating anions: Syntheses, characterization and catalytic application in stereoselective olefin aziridination

A multicentre-bonded [ZnI]8 cluster with cubic aromaticity

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Structural Characterization of a Base‐Stabilized [Zn2]2+ Cation

Cited by 81 publications

References 44 publications

Polarization Resolved Measurements of Individual DNA‐Stabilized Silver Clusters

Polarization Resolved Measurements of Individual DNA‐Stabilized Silver Clusters

Copper(ii) complexes incorporating poly/perfluorinated alkoxyaluminate-type weakly coordinating anions: Syntheses, characterization and catalytic application in stereoselective olefin aziridination

A multicentre-bonded [ZnI]8 cluster with cubic aromaticity

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Structural Characterization of a Base‐Stabilized [Zn₂]²⁺ Cation