ABSTRACT
Transition-metal (TM)-doped metallo-borospherenes exhibit unique structures and bonding in chemistry which have received considerable attention in recent years. Based on extensive global minimum searches and first-principles theory calculations, we predict herein the first and smallest perfect cubic metallo-borospherenes Oh TM8B6 (TM = Ni (1), Pd (2), Pt (3)) and Oh Ni8B6- (1-) which contain eight equivalent TM atoms at the vertexes of a cube and six quasi-planar tetra-coordinate face-capping boron atoms on the surface. Detailed canonical molecular orbital and adaptive natural density partitioning bonding analyses indicate that Oh TM8B6 (1/2/3) as superatoms possess nine completely delocalized 14c-2e bonds following the 18-electron principle (1S21P61D10), rendering spherical aromaticity and extra stability to the complex systems. Furthermore, Ni8B6 (1) can be used as building blocks to form the three-dimensional metallic binary crystal NiB (4) (Pm3Ìm) in a bottom-up approach which possesses a typical CsCl-type structure with an octa-coordinate B atom located exactly at the center of the cubic unit cell. The IR, Raman, UV-vis and photoelectron spectra of the concerned clusters are computationally simulated to facilitate their experimental characterization.
ABSTRACT
The recent discovery of lanthanide-metal-decorated metallo-borospherenes LM3B18- (LM = La, Tb) marks the onset of a new class of boron-metal binary nanomaterials. Using the experimentally observed or theoretically predicted borospherenes as ligands and based on extensive first-principles theory calculations, we predict herein a series of novel chiral metallo-borospherenes C2 Ni6 ∈ B39- (1), C1 Ni6 ∈ B41+ (3), C2 Ni6 ∈ B422+ (4), C2 Ni6 ∈ B42 (5), and C2 Ni8 ∈ B56 (6) as the global minima of the systems decorated with quasi-planar heptacoordinate Ni (phNi) centers in η7-B7 heptagons on the cage surfaces, which are found to be obviously better favoured in coordination energies than hexacoordinate Ni centers in previously reported D2d Ni6 ∈ B40 (2). Detailed bonding analyses indicate that these phNi-decorated metallo-borospherenes follow the σ + π double delocalization bonding pattern, with two effective (d-p)σ coordination bonds formed between each phNi and its η7-B7 ligand, rendering spherical aromaticity and extra stability to the systems. The structural motif in elongated axially chiral Ni6 ∈ B422+ (4), Ni6 ∈ B42 (5), and Ni8 ∈ B56 (6) can be extended to form the metallic phNi-decorated boron double chain (BDC) double-helix Ni4 ∈ B28 (2, 0) (P4Ìm2) (8), triple-helix Ni6 ∈ B42 (3, 0) (P3Ìm1) (9), and quadruple-helix Ni8 ∈ B56 (4, 0) (P4mm) (10) metallo-boronanotubes, which can be viewed as quasi-multiple-helix DNAs composed of interconnected BDCs decorated with phNi centers in η7-B7 heptagons on the tube surfaces in the atomic ratio of Ni : B = 1 : 7.
ABSTRACT
It is well-known that transition-metal-doping induces dramatic changes in the structures and bonding of small boron clusters, as demonstrated by the newly observed perfect inverse sandwich D8h [La(η8-B8)La] and D9h [La(η9-B9)La]-. Based on extensive global minimum searches and first-principles theory calculations, we predict herein the possibility of perfect endohedral trihedral metallo-borospherene D3h La@[La5&B30] (1, 3A'1) and its monoanion Cs La@[La5&B30]- (2, 2A') and dianion D3h La@[La5&B30]2- (3, 1A'1). These La-doped boron clusters are composed of three inverse sandwich La(η8-B8)La on the waist and two inverse sandwich La(η9-B9)La on the top and bottom which share one apex La atom at the center and six periphery B2 units between neighboring η8-B8 and η9-B9 rings, with three octo-coordinate La atoms and two nona-coordinate La atoms as integrated parts of the cage surface. Detailed adaptive natural density partitioning (AdNDP) and iso-chemical shielding surface (ICSS) analyses indicate that La@[La5&B30]0/-/2- (1/2/3) are spherically aromatic in nature. The one-dimensional nanowire La4B21 (4, P31m) constructed from D3h La@[La5&B30] (1) along the C3 axis of the system appears to be metallic. The IR and Raman spectra of La@[La5&B30] (1) and photoelectron spectroscopy of the slightly distorted Cs La@[La5&B30]- (2) are theoretically simulated to facilitate their spectroscopic characterizations.
ABSTRACT
Size-selected negatively-charged boron clusters (Bn-) have been found to be planar or quasi-planar in a wide size range. Even though cage structures emerged as the global minimum at B39-, the global minimum of B40- was in fact planar. Only in the neutral form did the B40 borospherene become the global minimum. How the structures of larger boron clusters evolve is of immense interest. Here we report the observation of a bilayer B48- cluster using photoelectron spectroscopy and first-principles calculations. The photoelectron spectra of B48- exhibit two well-resolved features at low binding energies, which are used as electronic signatures to compare with theoretical calculations. Global minimum searches and theoretical calculations indicate that both the B48- anion and the B48 neutral possess a bilayer-type structure with D2h symmetry. The simulated spectrum of the D2h B48- agrees well with the experimental spectral features, confirming the bilayer global minimum structure. The bilayer B48-/0 clusters are found to be highly stable with strong interlayer covalent bonding, revealing a new structural type for size-selected boron clusters. The current study shows the structural diversity of boron nanoclusters and provides experimental evidence for the viability of bilayer borophenes.
ABSTRACT
La-doped boron nanoclusters have received considerable attention due to their unique structures and bonding. Inspired by recent experimental observations of the inverse sandwich D 8h La2B8 (1) and triple-decker C 2v La3B14 - (2) and based on extensive global searches and first-principles theory investigations, we present herein the possibility of the perfect cubic La-doped boron clusters O h La6&[La@B24]+ (3, 1A1g) and O h La6&[La@B24] (4, 2A2g) which appear to be the embryos of the metallic one-dimensional La10B32 (5) nanowire, two-dimensional La3B10 (6) nanosheet, and three-dimensional LaB6 (7) nanocrystal, facilitating a bottom-up approach to build cubic lanthanide boride nanostructures from gas-phase clusters. Detailed molecular orbital and bonding analyses indicate that effective (d-p)σ, (d-p)π and (d-p)δ covalent coordination interactions exist in La6&[La@B24]+/0 (3/4) clusters, while the 1D La10B32 (5), 2D La3B10 (6), and 3D LaB6 (7) crystals exhibit mainly electrostatic interactions between the trivalent La centers and cubic B24 frameworks, with weak but discernible coordination contributions from La (5d) â B (2p) back-donations. The IR and Raman spectra of La6&[La@B24]+/0 (3/4) and band structures of La10B32 (5) and La3B10 (6) are computationally simulated to facilitate their future characterizations.
ABSTRACT
The first triazole-containing fluorescent probe with excellent water-solubility for Pd(2+) was presented. The results indicated that an amide-triazole-amide binding sequence was responsible for the unique affinity of PS-1 toward Pd(2+). Among the tested metal ions, only Pd(2+) could selectively quench the fluorescence of PS-1 under physiological conditions, while other common interference ions like Pt(2+) and Ru(3+) caused little changes. The successful fluorescence imaging of Pd(2+) in HeLa cells implied the potential applications of PS-1 in biological Pd(2+)-analysis.
ABSTRACT
A novel BINOL-based ratiometric fluorescent sensor (R2) is presented, which can selectively respond to Zn(2+) over Cd(2+) and other metal ions with fluorescence enhancement in aqueous solution. The R2 was successfully applied in the imaging of Zn(2+) in living cells. Additionally, the in situ generated R2-Zn(II) ensemble could further serve as a probe to distinguish histidine from other amino acids via a displacement mode.