Binary Cluster Anions Research Articles

Alkali Halide Cubic Cluster Anions ([Cs8X27]19-, X = Cl, Br) Isolated from Water.

Herein we report the syntheses and the X-ray structure of [Cs8X27]19- (X = Cl, Br) clusters, the first binary cluster anions isolated in bulk crystal structures. They were obtained by electrostatic capture and face-directed recognition of the prenucleation [CsmCln](n-m)- clusters from water solutions, using [M4(OH)8(OH2)16]8+ (M = ZrIV or HfIV) as the counter cations. These compounds have been thoroughly characterized with a variety of techniques including vibrational spectroscopy and superionic conductivity analysis. This work not only provides structural models for a better understanding of the nucleation of binary materials but also shows that magic number binary clusters adopting a cubic lattice structure do form, in agreement with the time-honored theoretical and spectroscopic predictions.

Photoelectron spectroscopy and ab initio calculations of small SinSm⁻ (n = 1,2; m = 1-4) clusters.

Binary cluster anions composed of silicon and sulfur elements, SinSm(-) (n = 1,2; m = 1-4), were investigated by using photoelectron spectroscopy and ab initio calculations. The vertical detachment energies and the adiabatic detachment energies of these clusters were obtained from their photoelectron spectra. The electron affinity of SiS molecule is determined to be 0.477 ± 0.040 eV. The results show that the most stable structures of the anionic and neutral SinSm (n = 1,2; m = 1-4) clusters prefer to adopt planar configurations except that the structures of Si2S4(-) and Si2S2 are slightly bent.

Experimental and theoretical investigation on binary anionic clusters of AlmBi

Al(m)Bi(n)(-) (m = 1-12; n = 1-4) binary cluster anions are generated by laser ablation of a sample composed of Al and Bi, and studied by reflectron time-of-flight mass spectrometry (RTOF-MS) in the gas phase. Some clusters with magic numbers are present in the mass spectrum. The structures of Al(m)Bi(n)(-) (m + n <or=7) clusters are investigated with the density functional theory (DFT) method and the most likely structures are obtained. The calculations of the binding energy (BE), energy gain (Delta) and HOMO-LUMO gaps confirm that the Al(2)Bi(3)(-) cluster has a very stable structure, which agrees well with the experimental results. It is further established that Al(2)Bi(3)(-) can be considered as a gas-phase Zintl analogue that follows Wade's rules and is the analogue of Ga(2)Bi(3)(-) and Sn(5)(2-) Zintl ions.

Experimental and theoretical investigation on binary semiconductor clusters of B/Si and Al/Si

AbstractASi (A = B and Al; n = 1–6) binary cluster anions were generated by laser ablation of samples composed of mixtures of Si and A (A = B and Al), and studied in the gas phase by tandem time‐of‐flight mass spectrometry. Some abundant ions are present in the mass spectrum, indicating that the clusters with these ions have stable structures. The structures of ASi clusters were investigated theoretically by the density functional theory (DFT) method and the energetically lowest‐lying structures were obtained. The binary clusters BSi and AlSi, with the same number of n, share different geometric structures except for ASi with n = 1 and 6, which have the same geometric structures in the ground state. For all the anionic clusters ASi, the lower spin state is lower in energy than the higher spin state in their optimized structures except for the linear ASi− anions, for which the triplet state is lower in energy than the singlet. Calculations of the bonding energy (BE), energy gain (Δ) and HOMO‐LUMO energy gaps confirm that the cluster ASi has a very stable structure, which agrees well with the experimental results. Copyright © 2007 John Wiley &amp; Sons, Ltd.

Experimental and Theoretical Investigation on Binary Semiconductor Clusters of Bi/Si, Bi/Ge, and Bi/Sn

Bi(m)M(n)- (M = Si, Ge, Sn) binary cluster anions are generated by using laser ablation on mixtures of Bi and M (M = Si, Ge, Sn) samples and studied by reflectron time-of-flight mass spectrometer (RTOF-MS) in the gas phase. Some magic number clusters are present in the mass spectra which indicate that they are in stable structures. For small anions (m + n < or = 6), their structures are investigated with the DFT method and the energetically lowest lying structures are obtained. For the binary anionic clusters with the same composition containing Si, Ge, and Sn, they share similar geometric and electronic structure in the small size except that BiSi3-, BiSi5-, Bi2Si2-, Bi2Si3-, and Bi4Sn2- are different for the lowest energetic structures, and the ground states for all the anions are in their lowest spin states. The calculated VDE (vertical detachment energy) and binding energy confirm the obviously magic number cluster of BiM4- (M = Si, Ge, Sn), which agrees with the experimental results.

Magic bimetallic cluster anions of M/Pb (M = Au, Ag and Cu) observed and analyzed by laser ablation and time-of-flight mass spectrometry.

By using laser ablation on mixtures of coinage metals M (Cu, Ag, Au) and lead, M/Pb binary cluster anions containing up to tens of atoms were produced and analyzed. Most of the magic clusters discovered can be described based on the electron shell models which were deduced from simple homogeneous metal cluster systems. The clustering activities of coinage metals and lead were also compared with the properties of their bulk binary alloys.

Formation, growth mechanism and packing sequences of binary alloy cluster anions from laser ablation of mixtures of lead and transition metals.

By using laser ablation of the mixtures of a transition metal (M: Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pd, Ag) plus lead, M/Pb binary cluster anions were observed except for Zn, and the number of transition metal atoms contained in the binary clusters is at most 4. This behavior is different from that reported previously for M/Ge binary clusters. The experiments indicate that it is also very difficult to form Al/Pb clusters. The distribution patterns of M/Pb binary alloy cluster anions are remarkably similar to those of pure Pb clusters, consistent with a formation mechanism in which transition metal atoms are sequentially attached to [M(x-1)Pb(y)](-) clusters and thus form [M(x)Pb(y)](-) clusters by a simple condensation process. As the number of transition metal atoms increases, the intensities of binary clusters gradually decrease. It is proposed that [MPb(4)](-) and [MPb(5)](-) cluster anions might be the unit building blocks of M/Pb binary cluster anions, and the layer packing sequences for magic clusters are predicted on this basis. The [M(x)Pb(y)](-) binary clusters containing 13 atoms (x + y = 13; x not equal 0) are proposed to have an icosahedral structure.

The Binary Anion Clusters of Ge/Sn, Ge/Pb, Sn/Pb, Co/Ge, Co/Sn and Co/Pb

The binary cluster anions of Ge/Sn, Ge/Pb, Sn/Pb, Co/Ge, Co/Sn and Co/Pb binary cluster ions, produced by direct laser ablation, were studied with a Tandem TOF mass spectrometer. The experiments show that E-1/E-2. (E-1/E-2 denotes Ge/Sn, Ge/Pb and Sn/Pb) binary clusters dominantly distribute in the lower mass region, in which the number of heavy atom is much larger than that of light atom. And composition and distribution of these binary clusters indicate that their structures and properties are similar to those pure group-14 elements cluster. By laser ablating the mixtures of transition metal cobalt and group-14 elements, mass spectra showed that abundance Co/E(E denotes Ge, Sn and Pb) cluster formed in higher mass range. Magic number CoGel(10)(-), CoSn10- and CoPb10- may have bi-capped tetragonal antiprism structure and CoPb12- is icosahedral structure. The difference between E-1/E-2 and Co/E binary cluster anions shows that all atoms for E-1/E-2 binary cluster anions are on the framework of the cage, while the cobalt atom for Co/E binary cluster is inside the cage of E.

Photoelectron spectroscopy of gold–silver binary cluster anions (AunAgm−; 2⩽n+m⩽4)

The electronic properties of gold–silver binary cluster anions (AunAgm−; 2⩽n+m⩽4) were studied by using photoelectron spectroscopy (PES) with a magnetic-bottle-type electron spectrometer. The AunAgm− cluster anions were generated by a laser vaporization of a gold–silver alloy rod. For triatomic AunAg3−n clusters, monotonous increases of electron affinity (EA) were observed by the replacement of Ag atom by Au atom. In contrast, the change in EA of tetratomic AunAg4−n clusters was irregular; for n=0–2 their EAs are almost the same around 1.5 eV, whereas for n=3,4 they increase to around 2.7 eV. This irregularity in EA of AunAg4−n can be attributed to the contribution of an ionic bonding. For Au1Ag3− and Au2Ag2−, moreover, the PES spectra show two components whose intensity ratio depends on cluster source conditions, showing that two isomers should coexist at these two compositions.

Studies on carbon/sulfur cluster anions produced by laser vaporization: Experiment (collision-induced dissociation) and theory (ab initio calculation). II C4Sm− (4⩽m⩽10)

Carbon/sulfur binary cluster anions with various compositions can be produced from laser vaporization of a sample mixed with sulfur and carbon powders in a 20:1 molar ratio. After mass-selection, their molecular formula was determined by collision-induced dissociation. The cluster anions consist of even carbon atoms only and their number of clustering sulfur atoms equals or exceeds that of carbon atoms. In this paper, we focus on mass spectrometry investigation and ab initio calculations on the cluster anions containing four carbon atoms, C4Sm− (4⩽m⩽10). Geometry of various isomeric structures of the clusters was optimized at the ROHF/6-31G* level and their energies were compared to find the most stable isomers. The structures of C4Sm− clusters computed in this paper were designed based on the structural features learned from the previous study on C2Sm− and the results of mass spectrometry experiments. Among the structures, four low-lying forms with two dangling sulfur atoms and two closed rings have the lowest energy. Based on the experimental and theoretical investigations, a ring shrinkage scheme is proposed to account for the dissociation process of the binary cluster anions observed in the experiment.

Studies on carbon/sulfur cluster anions produced by laser vaporization: Experiment (collision-induced dissociation) and theory (ab initio calculation). I. C2Sm− (1⩽m⩽11)

Binary cluster anions composed of carbon and sulfur atoms have been produced from laser vaporization of a sample mixed with sulfur and carbon powders in a 20:1 ratio. They were mass-selected and their molecular formula was determined by collision-induced dissociation. The clusters consist of even carbon atoms only and their number of clustering sulfur atoms equals or exceeds that of carbon atoms. Ab initio calculations at the ROHF/6-31G* level have been performed for the cluster anions containing two carbon atoms, C2Sm− (1⩽m⩽10). Geometries of various isomeric structures of the clusters were optimized and their energies were compared to find the most stable isomers. For the singly charged anions, attachment of an additional electron leads to break their sulfur rings, and the isomers with two dangling sulfur atoms and a closed ring have the lowest energy. According to the experimental and theoretical investigations, the two carbon atoms form the bone of the clusters, and ejection of two sulfur atoms is the most competitive dissociation pathway of the cluster anions.

Photoelectron spectroscopy of tin and lead cluster anions: application of halogen-doping method

Abstract Electronic properties of tin (Sn) and lead (Pb) cluster anions were studied using photoelectron spectroscopy (PES) with a magnetic bottle-type electron spectrometer, where the feasibility of a halogen-doping method we recently developed was explored. The binary cluster anions containing a chlorine atom (Cl) were produced by a laser vaporization of a target rod in a He carrier gas mixed with a small amount of CCl 4 gas. Comparing the PES of Sn n Cl − and those of Sn n − , it was found that the doped Cl atom in Sn n Cl − deprives each Sn n − cluster of the excess electron without any serious rearrangement of the Sn n framework, which is similar to our previous work on Si n F − and Ge n F − . The halogen-doping method enables us to reveal the HOMO–LUMO gap of the corresponding neutral cluster of the Sn n clusters, showing that the Sn n clusters are semiconductor clusters, especially below n =30, similar to the Si n and the Ge n clusters. For the Pb n clusters, however, the halogen-doping method was inapplicable, which implies that the Pb n clusters are different from the other group-14 clusters, probably exhibiting a metallic nature.

Mass spectrometry studies of carbon-nitrogen cluster anions produced by laser ablation Mass distribution and collision induced dissociation

Carbon-nitrogen cluster anions with various compositions were produced by laser ablating the K 3[Fe(CN) 6] sample and investigated by collision induced dissociation on a home-made tandem time-of-flight mass spectrometer. In addition to the previously studied C n N − ions, the binary clusters generated in the experiment can be composed of up to 11 nitrogen atoms. The species with similar mass distribution can also be created from organic compounds such as tetracyanoethylene, but K 4[Fe(CN) 6] and other cyanide coordination compounds could only produce binary cluster anions containing a single nitrogen atom. Based on the analysis of their fragmentation patterns, it is suggested that the cluster anions containing a single nitrogen atom are linear and those composed of more than two nitrogen atoms are mostly planar. Most of the species are highly conjugated, without or with very few dangling bonds.

Photoelectron spectroscopy of silicon- and germanium-fluorine binary cluster anions (Si n F m − , Ge n F m − )

Electronic properties of silicon-fluorine and germanium-fluorine cluster anions (SinFm−n = 1–9, m = 1–3, GenFm−; n =1–9, m = 1–3) were investigated by photoelectron spectroscopy using a magnetic-bottle type electron spectrometer. The binary cluster anions were generated by a laser vaporization of a silicon/germanium rod in an He carrier gas mixed with a small amount of SiF4 or F2 gas. Comparison between photoelectron spectra of SinF−/GenF− and Sin /Gen (n = 4–9) gives the insight that the doped F atom can remove one electron from the corresponding Sinn−/Gen− cluster without any serious rearrangement of Sin/Gen framework, because only the first peak of Sin−/Gen−, corresponding singly occupied molecular orbital (SOMO), disappears and other successive spectral features are unchanged with the F atom doping

Photoelectron spectroscopy of silicon–fluorine binary cluster anions (SinF−m)

Electronic properties of silicon–fluorine cluster anions (SinF−m; n=1–11, m=1–3) were investigated by photoelectron spectroscopy using a magnetic-bottle type electron spectrometer. The binary cluster anions were generated by a laser vaporization of a silicon rod in an He carrier gas mixed with a small amount of SiF4 or F2 gas. The highly abundant clusters are SiF−m (m=3 and 5) and SinF− (n=6, 7, and 10) in their mass spectra. In the photoelectron spectra of SiF−m (m=1–5), the clusters having odd m have higher electron affinity (EA) than those having even m, indicating that the even/odd alternation in EA is attributed to their electronic structures of a closed/open valence shell. Comparison between photoelectron spectra of SinF− and Si−n (n=4–11) gives the insight that the doped F atom can remove one electron from the corresponding Si−n cluster without any serious rearrangement of Sin framework, because only the first peak of Si−n, corresponding singly occupied molecular orbital (SOMO), disappears and other successive spectral features are unchanged with the F atom doping. In some clusters, furthermore, the vibrational structures could be resolved to determine a vibrational frequency and to presume the geometry with ab initio molecular orbital calculations.

Mass distributions of binary aluminium cluster anions Al nX m− (X = O, S, P, As, C)

Binary cluster anions of aluminium with some non-metallic elements, including oxygen, sulfur, phosphorus, arsenic and carbon, were generated by laser ablation of appropriate samples in high vacuum, and their mass distributions were recorded by mass spectrometry. Results show that the bonding nature and structural configuration of these cluster anions vary with their size and composition. As the non-metallic component varies from group VIA to VA and further to IVA, bonding of the clusters transforms from ionic to covalent. On the other hand, with increase of the cluster size, some aspects of the structures and properties of the clusters gradually approach those of their bulk compounds.