Superatomic clusters are relevant species to further understanding of bonding and structural properties of atomically precise molecular nanoparticles. Here, we explore the characteristics of ...ligand-free Ba
@Sn
Zintl-ion, as a three-dimensional aggregate of clusters featuring four fused Ba@Sn
building units as an extension of the understanding in linear and cyclic superatomic cluster arrays. We provide a rational picture of the electronic shell in Ba
@Sn
as a cluster-of-clusters motif through the recently introduced second-order superatom approach, as a three-dimensional aggregation of superatomic clusters where their shells are able to interact. The electronic structure features both tangential and radial shells from the four building Ba@Sn
units, leading to a set of 1S'
1P'
1D'
1F'
and higher angular momentum shells and a second set of 2S'
2P'
2D'
2F'
2
'
second-order shells. Thus, the current approach serves to encourage the rationalization of molecular materials conceived from cluster building blocks toward a rational guide for synthetic efforts.
The characterized phenyl decorated closo-monocarboranes with variable sizes from 7- to 12-vertex cages, Ph-closo-CB n H n −, n = 6–11, allow us to address the role of the varying size and shape of ...the carborane cage in dual planar–spherical aromatic species. Our results show the formation of adjacent shielding cone characteristics enabled from both planar and spherical aromatic fragments, despite the different structures of the closo-monocarboranes. Under a field perpendicular to the phenyl ring, both shielding cones are enabled, which overlap at long-range regions, in contrast to other orientations leading to a short-range response from the planar aromatic fragment. Thus, a two- or one-aromatic circuit is enabled selectively within the same molecular unit, by controlling the orientation of the external field. Along with the series, a variable extension of the shielding cone from the carborane cage is observed, which is larger for the −CB11H11 case, decreasing toward −CB6H6, denoting a similar extension from both the planar and spherical aromatic regions at the 4-Ph-closo-4-CB8H8− (4) counterpart. The analysis of such multiple aromatic structures shows that, despite the different sizes and shapes of the closo cages, a similar aromatic behavior remains. In addition, the anisotropy of the induced magnetic field is given graphically, denoting a larger anisotropy for the planar aromatic moiety owing to its two-dimensional structure, which is suggested to discriminate between planar and spherical aromatic fragments within the same molecule.
The recent characterization of Au52-PAP cluster can be viewed as a three-dimensional arrangement featuring four Au13 motifs. As a result, a new set of superatomic orbitals are built up from the ...superatomic shell of each constituent unit, denoted by 1S′21P′62S′21D′102P′61F′6 and, thus, referred to as a second-order superatomic shell structure. This favors the rationalization of larger species toward the formation of cluster-assembled materials of different sizes.
A unique four‐coordinate, classical gold(I)‐carbonyl complex with substantial backdonation from gold has been isolated by using a B‐methylated and fluorinated tris(pyridyl)borate chelator. Its ...lighter silver(I) and copper(I) analogs enabled a study of trends in the coinage‐metal family. The B‐arylated ligand version also afforded a gold–carbon monoxide complex that displays a notably low C−O stretch value, but with trigonal planar geometry at the gold. A computational analysis shows that the AuI−CO bonds of these tris(pyridyl)borate ligand‐supported molecules consist of electrostatic attraction, OC→Au σ‐donation, and very significant Au→CO π‐back‐bonding components. The latter is responsible for the observed C−O stretching frequencies, which are lower than in free CO.
Pyridyl‐borate scorpionates decorated with anionic and fluoro‐alkyl groups serve as ideal ligands to capture gold(I)‐carbon monoxide fragments in trigonal planar and tetrahedral environments that display remarkably low C−O stretching frequencies, and have significant Au−CO π‐bond character.
Sterically loaded, anionic pyridine has been synthesized and utilized successfully in the stabilization of a homoleptic series of coinage metal complexes. The treatment of 4-(Ph3B)-2,6-Trip2PyK ...(Trip =2,4,6-iPr3C6H2) with CuBr(PPh3), AgCl(PPh3) or AuCl(PPh3) (Py = pyridine) afforded the corresponding 4-(Ph3B)-2,6-Trip2PyM(PPh3) (M = Au, Ag, Cu) complexes, via salt metathesis, as isolable, crystalline solids. Notably, these reactions avoid the facile single electron transfer chemistry reported with the less bulky ligand systems. The X-ray structures revealed that they are two-coordinate metal adducts. The M-N and M-P bond distances are longest in the silver and shortest in the copper adduct among the three group 11 family members. Computational analysis revealed an interesting stability dependence on steric bulk of the anionic pyridine (i.e., pyridyl borate) ligand. A comparison of structures and bonding of 4-(Ph3B)-2,6-Trip2PyAu(PPh3) to pyridine and m-terphenyl complexes, {2,6-Trip2PyAu(PPh3)}SbF6 and 2,6-Trip2PhAu(PPh3) are also provided. The Au(I) isocyanide complex, 4-(Ph3B)-2,6-Trip2PyAu(CNBut) has been stabilized using the same anionic pyridylborate illustrating that it can support other gold-ligand moieties as well.
The induced magnetic field of C
2
N
(
N
= 3-14) carbon rings was dissected to contributions from out-of-plane and in-plane π orbitals revealing two concurrent long range shielding or deshielding ...cones as a manifestation of the dual aromatic and antiaromatic character of C
4
n
+2
and of C
4
n
rings respectively. Aromaticity based on the magnetic criterion was evaluated with regard to the bonding pattern and geometrical characteristics that elucidate the influence of bond length and bond angle alteration on out-of-plane and in-plane magnetic responses. Ground state polyynic geometries of C
4
n
+2
rings exhibit comparable shielding cones to annulenes, decreasing the magnetic response with regard to the ring size and similar π
out
and π
in
diatropicity. Transition state cumulenic rings display increased aromaticity expressed by a very strong constant magnetic response and augmented π
out
diatropicity with regard to π
in
. The variations of the induced magnetic field are explained on the basis of frontier orbital interactions through rotational excitations, which enable further rationalization of the aromatic/antiaromatic behavior.
Two orthogonal sets of π orbitals induce concurrent (de)shielding cones demonstrating the double (anti)aromaticity of sp-hybridized carbon rings.
Structural characterization of the discrete Sn@Cu12@Sn2012− cluster exposed a fascinating architecture composed of three concentric structural layers in which an endohedral Sn atom is enclosed in a ...Cu12 icosahedron, which in turn is embedded in an Sn20 dodecahedron. Herein, the possibility of sustaining aromatic behavior for this prototypical multilayered species was evaluated, in order to extend this concept to more complex clusters on the basis of magnetic response and bonding analysis by the AdNDP approach. This revealed characteristic features of spherical aromatics, given by the ability to sustain the shielding cone property, similar to archetypal aromatics. The favorable bonding pattern in the Sn@Cu12@Sn2012− cluster fulfills the 2(N+1)2 Hirsch rule for aromaticity; thus, the cluster could be regarded as a first member of aromatic multilayered structures. The set of four 13c–2e aromatic bonds that was identified in the internal SnCu12 structure results in spherical aromatic character of this multilayered cluster. This insight builds a bridge between the traditional concept of Hückel's aromaticity and the aromaticity of complex and stable 3D systems that may be explored on the basis of magnetic response and bonding analysis. It also may open a way to novel findings in bottled clusters displaying aromatic behavior in multilayer structures, which are of great interest for inorganic nano‐ and material sciences due to their unprecedented stability.
Russian doll aromatic: The Sn@Cu12@Sn2012− cluster, in which an endohedral Sn atom is enclosed in a Cu12 icosahedron, which in turn is embedded in an Sn20 dodecahedron, was shown by theoretical calculations to exhibit spherical aromaticity. Its shielding cone, which remains parallel to applied fields aligned in different orientations, resembles that of the classical planar aromatic compound benzene (see figure).
Atomically precise gold superatoms are useful building blocks whose properties can be tuned by the proper choice of ligands in the protecting ligand layer. Herein, different N-heterocyclic carbene ...(NHC) derivatives of the prototypical Au
(PPh
)
Cl
cluster were evaluated by the replacement of a single ligand, which led to isoelectronic Au
(PPh
)
(NHC)Cl
species, enabling further understanding of the possible changes in the resulting cluster properties. Our results reveal the great variation in the HOMO-LUMO gap and optical features when going from strong to weak σ-donor NHC ligands. The Au
core retains similar features throughout the series, and the lowest unoccupied orbital (LUMO) is further stabilized, indicating greater π*-NHC character for the weaker σ-donor ligands, which favors directional core-ligand optical charge transfer to a single ligand. The ligand-tailored behavior of the Au
(PPh
)
LCl
cluster underlies its tunable characteristics, indicating its potential use in novel devices as building blocks of nanostructured materials, which favors further versatility and applications of superatomic clusters.
Gold clusters are useful templates for nanosized species retaining a distinctive size-dependent behavior. Usually, a ligand-protected shell passivates such clusters, where their properties can be ...potentially tuned by introduction of versatile ligands. Here, we explored the recent addition to the well-explored gold–phosphine chemistry, introducing N-heterocyclic carbine (NHC) ligands as characterized by the octahedral carbon-centered CAu6 core, in CAu6(NHC)62+. Our results show their similar bonding patterns in such discrete clusters, with slight preference for the later ligands, enabling the proposition of medium-sized species featuring the predominant icosahedral Au13 structure. NHC counterparts for Au13Cl2(dppe) and Au25Cl2(PPh3)10(SR)5 clusters, denoting both icosahedral and bi-icosahedral central cores, where the bonding features patterns and favorable stability, remain similar to that observed for their phosphine parents and CAu6(NHC)62+ clusters, shedding light on other feasible members for explorative synthetic efforts. Optical properties are modified when NHC is introduced instead of phosphine ligands, inducing a red-shift for the lowest-energy peak with a highest occupied molecular orbital lowest unoccupied molecular orbital character and a blue-shift for higher energy absorptions. Hence, NHC derivatives as a ligand-protected layer for medium-sized clusters can introduce useful alternatives for ligand-protected shells, which can be further explored owing to their recognition for well-established versatility in organometallic chemistry.
The title compound, which has a ten‐atom deltahedral cluster core of Ge9Pd, was synthesized through insertion of Pd(PPh3) into the tetrasubstituted nona‐germanium cluster (Me3Si)Si3EtGe9 through a ...reaction of the latter with Pd(PPh3)4. This first reaction of neutral tetrasubstituted nine‐atom clusters shows that they retain reactivity despite their neutral charge. The Ge9Pd core is the first that incorporates a 5‐connected transition metal other than from Group VI, a noble metal in this case. Single‐crystal X‐ray diffraction shows that the ten‐atom core is a closo‐cluster with the expected shape of a bicapped square antiprism. 1H and 13C NMR spectroscopy show that, in contrast to the parent tetra‐substituted (Me3Si)Si3EtGe9, the new compound does not exhibit dynamics. Relativistic DFT calculations are used to explain the differences.
Cage closed: The title compound, an uncharged single‐cage deltahedron with five functionalities, was synthesized through insertion of Pd(PPh3) into (Me3Si)Si3EtGe9. The ten‐atom core is a closo‐cluster with the expected shape of a bicapped square antiprism, and the Ge9Pd core is the first to incorporates a 5‐connected transition metal other than from Group VI. In contrast to the Pd‐free parent, the new compound is static in solution.
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