Inorganic fullerene clusters have attracted widespread attention due to their highly symmetrical geometric structures and intrinsic electronic properties. However, cage-like clusters composed of heavy metal elements with high symmetry are rarely reported, and their synthesis is also highly challenging. In this study, we present the synthesis of a [K2(Bi@Pd12@Bi20)]4- cluster that incorporates a {Bi20} cage with pseudo-Ih symmetry, making it the largest main group metal cluster compound composed of the bismuth element to date. Magnetic characterization and theoretical calculations suggest that the spin state of the overall cluster is a quartet. Quantum chemical calculations reveal that the [Bi20]3- cluster has a similar electronic configuration to C606- and the [Bi@Pd12@Bi20]6- cluster exhibits a unique open-shell aromatic character.
We report here the synthesis and characterization of two endohedral Zintl-ion clusters, [Fe4Sn18]4- and [Fe4Pb18]4-, which contain rhombic Fe4 cores. The Fe-Fe bond lengths are all below 2.5 Å, distinctly shorter than in the corresponding Cu clusters, indicating the presence of Fe-Fe bonding. Subtle differences in the structure of the Fe4 core between the two clusters suggest that the change in tetrel element causes a change in electronic ground state, with a very short Fe-Fe bond length of 2.328 Å present across the diagonal of the rhombus in the lead case.
The endohedral Zintl-ion cluster [Fe3Sn18]4- contains a linear Fe3 core with short Fe-Fe bond lengths of 2.4300(9) Å. The ground state is a septet, with significant σ and π contributions to the Fe-Fe bonds. The Sn18 cage is made up of two partially fused Sn9 fragments, and is structurally intermediate between [Ni2CdSn18]6-, where the fragments are clearly separated and [Pd2Sn18]4-, where they are completely fused. It therefore represents an intermediate stage in cluster growth. Analysis of the electronic structure suggests that the presence of the linear Fe-Fe-Fe unit is an important factor in directing reactions towards fusion of the two Sn9 units rather than the alternative of oligomerization via exo bond formation.
The C60 fullerene molecule has attracted tremendous interest for its distinctive nearly spherical structure. By contrast, all-metal counterparts have been elusive: Fullerene-like clusters composed of noncarbon elements typically suffer from instability, resulting in more compact geometries that require multiple embedded atoms or external ligands for stabilization. In this work, we present the synthesis of an all-metal fullerene cluster, [K@Au12Sb20]5-, using a wet-chemistry method. The cluster's structure was determined by single crystal x-ray diffraction, which revealed a fullerene framework consisting of 20 antimony atoms. Theoretical calculations further indicate that this distinct cluster exhibits aromatic behavior.
Thousand and one amino acid kinase 2 (TAOK2) is a member of the mammalian sterile 20 kinase family and is implicated in neurodevelopmental disorders; however, its role in neuropathic pain remains unknown. Here, we found that TAOK2 was enriched and activated after chronic constriction injury (CCI) in the rat spinal dorsal horn. Meanwhile, cyclic guanosine monophosphate-adenosine monophosphate synthase (cGAS)-stimulator of interferon genes (STING) signaling was also activated with hyperalgesia. Silencing TAOK2 reversed hyperalgesia and suppressed the activation of cGAS-STING signaling induced by CCI, while pharmacological activation of TAOK2 induced pain hypersensitivity and upregulation of cGAS-STING signaling in naive rats. Furthermore, pharmacological inhibition or gene silencing of cGAS-STING signaling attenuated CCI-induced hyperalgesia. Taken together, these data demonstrate that the activation of spinal TAOK2 contributes to CCI-induced hyperalgesia via cGAS-STING signaling activation, providing new molecular targets for the treatment of neuropathic pain.
In this work, we report a low-valent Ga(I) complex, [Ga@Bi10(NbMes)2]3-, with a linear Nb-Ga-Nb fragment, representing the first compound with Nb-Ga and Nb-Bi bonds. Quantum-chemical calculations reveal that the complex is an electron-precise cluster. The possible fragmentation pathway of the title cluster was studied by using electrospray ionization mass spectrometry and theoretical calculations.
We report here the synthesis and structural characterization of the first binary iron arsenide cluster anion, [Fe3 (As3 )3 (As4 )]3- , present in both [K([2.2.2]crypt)]3 [Fe3 (As3 )3 (As4 )] (1) and [K(18-crown-6)]3 [Fe3 (As3 )3 (As4 )]â en (2). The cluster contains an Fe3 triangle with three short Fe-Fe bond lengths (2.494(1)â Å, 2.459(1)â Å and 2.668(2)â Å for 1, 2.471(1)â Å, 2.473(1)â Å and 2.660(1)â Å for 2), bridged by a 2-butene-like As4 unit. An analysis of the electronic structure using DFT reveals a triplet ground state with direct Fe-Fe bonds stabilizing the Fe3 core.
Groupâ 14 endohedral clusters containing a metal center inside usually possess a single cage topological structure, but here an unexpected single-metal-filled double-cage cluster, [Pt@Sn17 ]4- (1 a) is reported. It can be seen as a combination of the more extended Pt-filled [Pt@Sn9 ] cage and hollow [Sn9 ] cage sharing a central Sn atom, which is offset from the central position. This double-cage species represents the largest groupâ 14 intermetalloid cluster encapsulating a single transition metal atom. DFT calculations show that the capsule-like architecture of [Sn17 ]4- , similar to that found in [Pt2 @Sn17 ]4- , is unstable if filled with a single Pt atom and collapses to the title cluster 1 a upon geometry optimization. Deviation of the central Sn atom occurs due to the vibronic coupling as a consequence of pseudo-Jahn-Teller distortion leading to the bent Cs -symmetrical structure, in contrast to the more symmetrical D2d cage previously reported in [Ni2 @Sn17 ]4- .
During the past two decades, single-atom-centered medium-sized germanium clusters [M@Gen ] (M=transition metals, n>12) have been extensively explored, both from theoretical perspectives and experimental gas-phase syntheses. However, the actual structural arrangements of the Ge13 and Ge14 endohedral cages are still ambiguous and have long remained an unresolved problem for experimental implementation. In this work, we successfully synthesize 13-/14-vertex Ge clusters [Nb@Ge13 ]3- (1) and [Nb@Ge14 ]3- (2), which are structurally characterized and exhibit unprecedented topologies, neither classical deltahedra nor 3-connected polyhedral structures. Theoretical analysis indicates that the major stabilization of the Ge backbones arises due to the substantial interaction of Ge 4p-AOs with the endohedral Nb 4d-AOs through three/four-center two-electron bonds with an enhanced electron density accumulated over the shortest Nb-Ge13 contact in 1. Low occupancies of the direct two-center two-electron (2c-2e) Nb-Ge and Ge-Ge σ bonds point to a considerable degree of electron delocalization over the Ge cages revealing their electron deficiency.
The development of rational synthetic routes to inorganic arsenide compounds is an important goal because these materials are finding applications in many areas of materials science. In this paper, we show that the binary crown clusters [M@As8]3- (M = Nb, Ta) can be used as synthetic precursors which, when combined with ZnMes2, generate ternary intermetalloid clusters with 12-vertex cages, {M@[As8(ZnMes)4]}3- (M = Nb, Ta). Structural studies are complemented by mass spectrometry and an analysis of the electronic structure using DFT. The synthesis of these clusters presents new opportunities for the construction of As-based nanomaterials.
In this work, we synthesize naked tin cluster anion Sn368-, representing the first example of pure Sn nanowire assembled through oxidative coupling reactions of a super atomic cluster Sn94-. Theoretical analysis confirm the presence of aromaticity for each Sn9 unit showing four adjacent aromatic subunits bridged by parallel Sn-Sn bonds.
We report here the structure of an endohedral plumbaspherene, [Cu4Pb22]4-, the gold analogue of which was previously postulated to be a "missing link" in the growth of larger clusters containing three and four icosahedral subunits. The cluster contains two [Cu2Pb11]2- subunits linked through a Cu2Pb4 trigonal antiprism. Density functional theory reveals that the striking ability of mixed Pb/coinage metal Zintl clusters to oligomerize and, in the case of Au, to act as a site of nucleation for additional metal atoms, is a direct consequence of their nd10(n + 1)s0 configuration, which generates both a low-lying (n + 1)s-based LUMO and also a high-lying Pb-centered HOMO. Cluster growth and nucleation is then driven by this amphoteric character, allowing the clusters to form donor-acceptor interactions between adjacent icosahedral units or to additional metal atoms.
Understanding the structural changes taking place during the assembly of single atoms leading to the formation of atomic clusters and bulk materials remains challenging. The isolation and theoretical characterization of medium-sized clusters can shed light on the processes that occur during the transition to a solid-state structure. In this work, we synthesize and isolate a continuous 24-atom cluster Ge244-, which is characterized by X-ray diffraction analysis and Energy-dispersive X-ray spectroscopy, showing an elongated structural characteristic. Theoretical analysis reveals that electron delocalization plays a vital role in the formation and stabilization of the prolate cluster. In contrast with carbon atoms, 4 s orbitals of Ge-atoms do not easily hybridize with 4p orbitals and s-type lone-pairs can be localized with high occupancy. Thus, there are not enough electrons to form a stable symmetrical fullerene-like structure such as C24 fullerene. Three aromatic units with two [Ge9] and one [Ge6] species, connected by classical 2c-2e Ge-Ge σ-bonds, are aligned together forming three independent shielding cones and eventually causing a collapse of the global symmetry of the Ge244- cluster.
Inorganic metallocene derivatives containing only cyclo-Pn ligands have been targeted for more than 20 years, but their syntheses have never been achieved by pursuing the conventional route of using P4 phosphorus except for the generation of [Ti(η5-P5)2]2-. Herein, we report a facile one-step method for the synthesis of the homoleptic iron complex [Fe(P4)2]2- by the Zintl-phase-type precursor KP. 31P NMR analyses indicate that upon dissolving the KP phase in ethylenediamine P42- was generated only in the presence of 2,2,2-crypt. The amounts of cation-sequestering agents, the type of iron precursor, and their consuming ratio have a decisive impact on the yield of [Fe(P4)2]2-. Both the FeII and the FeIII precursors can oxidize P42- to give a concomitant product [(P7)Fe(P4)]3-, which can be partially inhibited by the addition of potassium to produce relatively pure crystalline [K(2,2,2-crypt)]2[Fe(P4)2].
The [Nb@As8]3- anion was first isolated from solution in 1986, and a number of isostructural [M@Pn8]n- clusters (M = Nb, Cr, or Mo; Pn = As or Sb; n = 2 or 3) have since been reported. We show here how anions of this class can be used as synthetic precursors that, in combination with sources of low-valent late transition metals (Cu and Ag), generate ternary polyarsenide cluster anions with unprecedented structural motifs. Chain type [MM'As16]4- (M = Nb or Ta; M' = Cu or Ag) units are found in compounds 2-5. These clusters contain a nortricyclane-like As7 cage and a [M@As8] crown, linked by a single As atom, and represent a fusion of two quite distinct branches of polyarsenide chemistry. Our analysis of the electronic structure confirms that the cluster retains many of the features of the component units. Electrospray ionization mass spectrometry reveals a series of smaller component ions containing 8-12 As atoms, the density functional theory-computed structures of which can be understood in terms of the pseudoelement concept. This work not only presents a new type of coordination mode for As clusters but also offers a point of entry for the rational design of multinary arsenic-based materials.
We report here a new double-cage endohedral Ge cluster, [Co2@(Ge17Ni)]4-, fused through two [Co@(Ge9Ni)] moieties with a shared Ni-Ge edge. This ternary Co-Ge-Ni species not only represents the first double-cage example of an 18-vertex Zintl cluster, but also fills in the missing link of the edge fusion model in the double-cage systems.
Density functional theory (DFT) calculations were employed to study the stabilities, electronic structures, and vibrational and bonding properties of dianionic pentacarbonyls [TM(CO)5]2- (TM = Cr, Mo, W). A D3h symmetry structure with singlet state was found to be the ground state and C-O stretching vibrational frequencies range from 1719 to 1766 cm-1, which are in excellent agreement with the experimental observations. The calculation results on bond dissociation energy for the CO loss revealed their stabilities. By employing energy decomposition analysis (EDA), the bonding nature between TM2- and (CO)5 was disclosed, in which the [TM(d)]2-â(CO)5π backdonations contribute largely to the orbital interactions while σ donation from the lone pair of CO to metal contributes moderately. Compared with those in the isoelectronic neutral hexacarbonyls TM(CO)6, the π backdonations are obviously larger in [TM(CO)5]2- because there are two extra electrons in (n- 1)d AOs of the center transition metal.
Heterometallic clusters have attracted broad interests in the synthetic chemistry due to their various coordination modes and potential applications in heterogeneous catalysis. Here we report the synthesis, experimental, and theoretical characterizations of four ternary clusters ([M2(CO)6Sn2Sb5]3- (M = Cr, Mo), and [(MSn2Sb5)2]4-, (M = Cu, Ag)) in the process of capturing the hypho- [Sn2Sb5]3- in ethylenediamine (en) solution. We show that the coordination of the binary anion to transition-metal ions or fragments provides additional stabilization due to the formation of locally σ-aromatic units, producing a spherical aromatic shielding region in the cages. While in the case of [Mo2(CO)6Sn2Sb5]3- stabilization arises from locally σ-aromatic three-centre and five-centre two-electron bonds, aromatic islands in [(AgSn2Sb5)2]4- and [(CuSn2Sb5)2]4- render them globally antiaromatic. This work describes the coordination chemistry of the versatile building block [Sn2Sb5]3-, thus providing conceptual advances in the field of metal-metal bonding in clusters.
The anionic cluster [Fe2@Ge16]4- has been characterized and shown to be isostructural to the known D2h-symmetric α isomer of the cobalt analogue [Co2@Ge16]4-. Together with the known pair of compounds [Co@Ge10]3- and [Fe@Ge10]3-, the title compound completes a set of four closely related germanium clusters that allow us to explore how the metal-metal and metal-cage interactions evolve as a function of size and of the identity of the metal. The results of spin-unrestricted density functional theory (DFT) and multiconfigurational self-consistent field (MC-SCF) calculations present a consistent picture of the electronic structure where transfer of electron density from the metal to the cage is significant, particularly in the Fe clusters where the exchange stabilization of unpaired spin density is an important driving force.
