[Ag21{S2P(OiPr)2}12]+: An Eight-Electron Superatom Dhayal, Rajendra S.; Liao, Jian-Hong; Liu, Yu-Chiao ...
Angewandte Chemie (International ed.),
March 16, 2015, Letnik:
54, Številka:
12
Journal Article
Recenzirano
A novel discrete Ag21{S2P(OiPr)2}12(PF6) nanocluster has been synthesized and characterized by single‐crystal X‐ray diffraction and also NMR spectroscopy (1H, 31P), ESI mass spectrometry, and other ...analytic techniques (XPS, EDS, UV/Vis spectroscopy). The Ag21 skeleton has an unprecedented silver‐centered icosahedron that is capped by eight additional metal atoms. The whole framework is protected by twelve dithiophosphate ligands. According to the spherical Jellium model, the stability of monocationic nanocluster can be described by an 8‐electron superatom with 1S2 1P6 configuration, as confirmed by DFT calculations.
Silver super skeleton: A single‐crystal X‐ray diffraction study of a novel Ag21{S2P(OiPr)2}12(PF6) nanocluster shows an unprecedented silver‐centered icosahedron with additional eight capping silver atoms to generate an Ag21 metal skeleton. DFT calculations indicate that this stable monocationic nanocluster is an eight‐electron superatom.
Three bimetallic platinum/silver nanoclusters, PtAg20(dtp)12 (1), Pt2Ag33(dtp)17 (2), and Pt3Ag44(dtp)22 (3) (dtp: dipropyl dithiophosphate), with cluster electron counts of 8, 16, and 22, ...respectively, were produced via a one-phase coreduction method. Single-crystal X-ray structures reveal that their inner cores can be visualized as consisting of one, two, and three centered icosahedral Pt@Ag12 units, respectively. In 2 and 3, these units are vertex-sharing and are assembled linearly. Intriguingly, the 22-electron alloy (3) is isolobal to the linear triiodide anion, I3 –, and represents the first example of a cluster made of three superatoms whose bonding characteristics are similar to those of a triatomic molecular species.
Luminescent materials based on copper complexes are currently receiving increasing attention because of their rich photophysical properties, opening a wide field of applications. The copper iodide ...clusters formulated Cu4I4L4 (L = ligand), are particularly relevant for the development of multifunctional materials based on their luminescence stimuli-responsive properties. In this context, controlling and modulating their photophysical properties is crucial and this can only be achieved by thorough understanding of the origin of the optical properties. We thus report here, the comparative study of a series of cubane copper iodide clusters coordinated by different phosphine ligands, with the goal of analyzing the effect of the ligands nature on the photoluminescence properties. The synthesis, structural, and photophysical characterizations along with theoretical investigations of copper iodide clusters with ligands presenting different electronic properties, are described. A method to simplify the analysis of the 31P solid-state NMR spectra is also reported. While clusters with electron-donating groups present classical luminescence properties, the cluster bearing strong electron-withdrawing substituents exhibits original behavior demonstrating a clear influence of the ligands properties. In particular, the electron-withdrawing character induces a decrease in energy of the unoccupied molecular orbitals, that consequently impacts the emission properties. The modification of the luminescence thermochromic properties of the clusters are supported by density functional theory (DFT) calculations. This study demonstrates that the control of the luminescence properties of these compounds can be achieved through modification of the coordinated ligands, nevertheless the role of the crystal packing should not be underestimated.
Three copper(I) iodide clusters coordinated by different phosphine ligands formulated Cu4I4(PPh3)4 (1), Cu4I4(Pcpent3)4 (2), and Cu4I4(PPh2Pr)4 (3) (PPh3 = triphenylphosphine, Pcpent3 = ...tricyclopentylphosphine, and PPh2Pr = diphenylpropylphosphine) have been synthesized and characterized by 1H and 31P NMR, elemental analysis and single crystal X-ray diffraction analysis. They crystallize in different space groups, namely, monoclinic P21/c, cubic Pa3̅, and tetragonal I4̅2m for 1, 2, and 3, respectively. The photoluminescence properties of clusters 1 and 3 show reversible luminescence thermochromism with two highly intense emission bands whose intensities are temperature dependent. In accordance to Density Functional Theory (DFT) calculations, these two emission bands have been attributed to two different transitions, a cluster centered (CC) one and a mixed XMCT/XLCT one. Cluster 2 does not exhibit luminescence variation in temperature because of the lack of the latter transition. The absorption spectra of the three clusters have been also rationalized by time dependent DFT (TDDFT) calculations. A simplified model is suggested to represent the luminescence thermochromism attributed to the two different excited states in thermal equilibrium. In contrast with the pyridine derivatives, similar excitation profiles and low activation energy for these phosphine-based clusters reflect high coupling of the two emissive states. The effect of the Cu–Cu interactions on the emission properties of these clusters is also discussed. Especially, cluster 3 with long Cu–Cu contacts exhibits a controlled thermochromic luminescence which is to our knowledge, unknown for this family of copper iodide clusters. These phosphine-based clusters appear particularly interesting for the synthesis of original emissive materials.
The isoelectronic doping of dichalcogenolato nanoclusters of the type Ag21{E2P(OR)2}12+ (E = S, Se) by any heteroatom belonging to groups 9–12 was systematically investigated using DFT calculations. ...Although they can differ in their global structure, all of these species have the same M@M12-centered icosahedral core. In any case, the different structure types are all very close in energy. In all of them, three different alloying sites can be identified (central, icosahedral, peripheral) and calculations allowed the trends in heteroatom site occupation preference across the group 9–12 family to be revealed. These trends are supported by complementary experimental results. They were rationalized on the basis of electronegativity, potential involvement in the bonding of valence d-orbitals and atom size. TD-DFT calculations showed that the effect of doping on optical properties is sizable and this should stimulate research on the modulation of luminescence properties in the dithiolato and diseleno families of complexes.
The first atomically and structurally precise silver‐nanoclusters stabilized by Se‐donor ligands, Ag20{Se2P(OiPr)2}12 (3) and Ag21{Se2P(OEt)2}12+(4), were isolated by ligand replacement reaction of ...Ag20{S2P(OiPr)2}12 (1) and Ag21{S2P(OiPr)2}12+ (2), respectively. Furthermore, doping reactions of 4 with Au(PPh3)Cl resulted in the formation of AuAg20{Se2P(OEt)2}12+ (5). Structures of 3, 4, and 5 were determined by single‐crystal X‐ray diffraction. The anatomy of cluster 3 with an Ag20 core having C3 symmetry is very similar to that of its dithiophosphate analogue 1. Clusters 4 and 5 exhibit an Ag21 and Au@Ag20 core of Oh symmetry composed of eight silver capping atoms in a cubic arrangement and encapsulating an Ag13 and Au@Ag12 centered icosahedron, respectively. Both ligand exchange and heteroatom doping result in significant changes in optical and emissive properties for chalcogen‐passivated silver nanoparticles, which have been theoretically confirmed as 8‐electron superatoms.
Silver surfer: A diselenophosphate‐protected heteronuclear Au@Ag20(dsep)12+ nanocluster was synthesized by a galvanic replacement reaction of Ag21(dsep)12+ with Au(PPh3)Cl. The Au@Ag125+ core of Ih symmetry, an 8‐electron superatom, is capped on 8 of its 20 triangular faces by silver atoms arranged in a cube.
The first structurally characterized copper cluster with a Cu13 centered cuboctahedral arrangement, a model of the bulk copper fcc structure, was observed in Cu13(S2CNnBu2)6(C≡CR)4(PF6) (R=C(O)OMe, ...C6H4F) nanoclusters. Four of the eight triangular faces of the cuboctahedron are capped by acetylide groups in μ3 fashion, and each of the six square faces is bridged by a dithiolate ligand in μ2,μ2 fashion, which leads to a truncated tetrahedron of twelve sulfur atoms. DFT calculations are fully consistent with the description of these Cu13 clusters as two‐electron superatoms, that is, a Cu1311+ core passivated by ten monoanionic ligands, with an a1 HOMO containing two 1S jellium electrons.
Just like in the metal: Cu13 clusters with a centered cuboctahedral unit, a model of the bulk Cu metal fcc structure, have been synthesized. The Cu1311+ core can be described as a two‐electron superatom; four of the eight triangular faces are capped by acetylide groups, and each of the six square faces is bridged by a dithiolate ligand to yield ideal tetrahedral symmetry.
DFT calculations were carried out on a series of cluster cores, the framework of which was made of the condensation of several Pt@Ag
12
-centered icosahedra. Icosahedral condensations through ...vertex-sharing, face-sharing, and interpenetration were considered and their favored electron counts were determined from their stable closed-shell configurations. A large number of the computed assemblies of
n
icosahedral superatomic units can be considered as isolobal analogs of stable, closed-shell
n
-atom molecules, most of them obeying the octet rule. The larger the degree of fusion between icosahedra, the stronger the interaction between them. For example, it was possible to design 3-icosahedral supermolecular cores analogous to CO
2
, SF
2
, or I
3
−
, but also to the not-yet-isolated cyclic O
3
. Supermolecules equivalent to non-stable molecules can also be designed. Indeed, differences exist between atoms and superatoms, and original icosahedra assemblies with no "molecular" analogs are also likely to exist, especially with compact structures and/or systems made of a large number of fused superatoms.
Making stable supermolecules isolobal to simple molecules.
An original copper(I) iodide cluster of novel geometry obtained by using a diphosphine ligand is reported and is formulated Cu6I6(PPh2(CH2)3PPh2)3 (1). Interestingly, this sort of “eared cubane” ...cluster based on the Cu6I6 inorganic core can be viewed as a combination of the two known Cu4I4 units, namely, the cubane and the open-chair isomeric geometries. The synthesis, structural and photophysical characterisations, as well as theoretical study of this copper iodide along with the derived cubane (3) and open-chair (2) Cu4I4(PPh3)4 forms, were investigated. A new polymorph of the cubane Cu4I4(PPh3)4 cluster is indeed presented (3). The structural differences of the clusters were analyzed by solid-state nuclear magnetic resonance spectroscopy. Luminescence properties of the three clusters were studied in detail as a function of the temperature showing reversible luminescence thermochromism for 1 with an intense orange emission at room temperature. This behavior presents different feature compared to the cubane cluster and completely contrasts with the open isomer, which is almost nonemissive at room temperature. Indeed, the thermochromism of 1 differs by a concomitant increase of the two emission bands by lowering the temperature, in contrast to an equilibrium phenomenon for 3. The luminescence properties of 2 are very different by exhibiting only one single band when cooled. To rationalize the different optical properties observed, density functional theory calculations were performed for the three clusters giving straightforward explanation for the different luminescence thermochromism observed, which is attributed to different contributions of the ligands to the molecular orbitals. Comparison of 3 with its Cu4I4(PPh3)4 cubane polymorphs highlights the sensibility of the emission properties to the cuprophilic interactions.
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