Monodisperse Iridium Clusters Protected by Phenylacetylene: Implication for Size-Dependent Evolution of Binding Sites

Abstract

Terminal alkynes form a variety of interfacial structures with the clusters and nanoparticles of Au, Ag, Cu, Ru, Pd, and Pt. In order to extend the scope of modification by alkynes, we herein report the synthesis and structure characterization of Ir clusters protected by phenylacetylene (PA). Small, monodisperse PA-protected Ir clusters (1.3 ± 0.2 nm) were obtained by biphasic ligand exchange from ethylene glycol-stabilized Ir clusters (1.5 ± 0.2 nm). High-resolution transmission electron microscopy, extended X-ray absorption fine structure analysis, and powder X-ray diffraction analysis indicated that Ir clusters exhibit a face-centered cubic structure. X-ray photoelectron spectroscopy and X-ray absorption spectroscopy indicated Ir atoms are almost in the zero valence state, which is in sharp contrast to the partial oxidation observed for Ir clusters stabilized by polymers. Absence of the terminal hydrogen of PA and red-shift of the CC stretching mode upon ligation observed by Fourier-transform infrared spectroscopy showed that the PA ligands are bound to Ir clusters via Ir−C bonds. Mass spectrometry revealed that the number of the Ir atoms in Ir n (PA) m has a much narrower distribution (n = 46−53) than that of the PA ligands (m = 19−33). This finding suggests a drastic change in the binding sites of PA ligands even with a small change of the size of Ir clusters. Surprisingly, the number of PA ligands (m) decreased with increase in the size of Ir clusters (n). Within the framework of the upright binding model of PA, this counterintuitive correlation between n and m values suggests that binding sites of PA are shifted dramatically from on-top sites to bridged sites with increase in the cluster size.

Stable iridium dinuclear heterogeneous catalysts supported on metal-oxide substrate for solar water oxidation

“…While the dinuclear nature of the structure is unambiguously confirmed by the HAADF data, an alternative arrangement to the proposed one could feature Ir-Ir bonding. In the in situ CO DRIFT experiment, the two arrangements are expected to be readily distinguished by the characteristic absorption features at ∼1,850 cm −1 , which is indicative of the bridge adsorption of CO at the Ir-Ir site (20). Indeed, the broad peak at ∼1,850 cm −1 was observed for Ir NPs control samples with known Ir-Ir bonding ( Fig.…”

An organometallic ruthenium nanocluster with conjugated aromatic ligand skeleton for explosive sensing

“…have been successfully used to synthesize different metal clusters and nanoparticles. [5][6][7][8][9][10][11][12][13] Contrary to other ligands as mentioned above, carbon-based ligands are attractive candidates because we could expect better electronic conjugation between ligand skeleton and metal core through conjugated metal-carbon bond. This anticipated electronic conjugation will substantially alter the electronic nature of the metal cluster and surface ligands and could prove valuable for catalysis 14 and nanoelectronics applications.…”

“…The replication of the sensing behavior of conjugated polymer system in a ligand-stabilized metal cluster will be interesting and appealing for explosive sensing viewpoint. The syntheses routes of various organometallic clusters and nanoparticles have been developed by Tsukuda and Maity, [8][9][10][11][12] Schriffrin, 5 Chen, 6,7 and Wang 13 in recent years via self-assembly, base-promoted direct ligation and ligand exchange based strategies with a major focus on gold clusters. In the present work, we are reporting the synthesis of an alkyne based pi electronrich aromatic ligand (9-ethynylphenanthrene) stabilized Ru cluster via facile ligand exchange strategy and its detail characterization including molecular weight determination through MALDI mass spectrometry.…”

Central Doping of a Foreign Atom into the Silver Cluster for Catalytic Conversion of CO2 toward C−C Bond Formation

“…For comparison, when Cs 2 CO 3 was added into the reaction system, an interesting phenomenon was observed: the peak at 3290 cm −1 disappeared and the peak at 2105 cm −1 shifted to 2145 cm −1 (Figure b). It reveals that the H atom of ≡C−H group is removed from the alkyne and the terminal of C≡C bond of alkyne interacts with clusters and becomes activated . The existence of Cs 2 CO 3 is thus crucial for the adsorption and activation of the terminal of C≡C bond of alkyne on the clusters.…”