Lai-Sheng Wang

• Brown University

Despite major progress in the investigation of boron cluster anions, direct experimental study of neutral boron clusters remains a significant challenge because of the difficulty in size selection. Here we report a size‐specific study of the neutral B9 cluster using threshold photoionization with a tunable vacuum ultraviolet free electron laser. Th...

Despite major progress in the investigation of boron cluster anions, direct experimental study of neutral boron clusters remains a significant challenge because of the difficulty in size selection. Here we report a size‐specific study of the neutral B9 cluster using threshold photoionization with a tunable vacuum ultraviolet free electron laser. Th...

Polyhedral boranes are a class of well-known boron molecular clusters widely used in energy, chemistry, medicine, and materials science because of their unique physical and chemical properties. Great efforts have been made in the past decades to find more effective synthetic methods for this important class of boron compounds. However, existing syn...

Due to its electron deficiency, boron triple bonds are relatively scarce. We use high-resolution photoelectron imaging to investigate the structures and bonding of EB 2 O ⁻ (E = P, As) type of...

Fullerenes, spherical molecules made entirely of carbon atoms, have played a foundational role in the birth of nanoscience. Despite extensive research, however, comparable structures composed of other elements remain elusive, highlighting the unique bonding properties of carbon that enable the formation of such remarkable nanoscale architectures. H...

The reactivity of Bi n ⁻ clusters ( n = 2 to 30) with O 2 is found to display even-odd alternations. The open-shell even-sized Bi n ⁻ clusters are more reactive than the closed-shell odd-sized clusters, except Bi 18 ⁻ , which exhibits no observable reactivity toward O 2 . We have investigated the structure and bonding of Bi 18 ⁻ to understand its r...

Polycyclic aromatic hydrocarbons (PAHs) are common atmospheric pollutants, and they are also ubiquitous in the interstellar medium. Here, we report the study of a complex O-containing PAH anion, the deprotonated 2-hydroxytriphenylene (2-OtPh–), using high-resolution photoelectron imaging and photodetachment spectroscopy of cryogenically cooled anio...

Copper has been shown to be an important substrate for the growth of borophenes. Copper-boron binary clusters are ideal platforms to study the interactions between copper and boron, which may...

SO 2 (Sulfur dioxide) is the major precursor to the production of sulfuric acid (H 2 SO 4 ), contributing to acid rain and atmospheric aerosols. Sulfuric acid formed from SO 2 generates light-reflecting sulfate aerosol particles in the atmosphere. This property has prompted recent geoengineering proposals to inject sulfuric acid or its precursors i...

Boron has been found to be able to form multiple bonds with the Pb atom. To probe the Pb–B bonding, here we report an investigation of three Pb-doped boron clusters,...

Polyhedral boranes are a class of well-known boron molecular clusters with unique physical and chemical properties, and great efforts have been made in the past decades to find more effective synthetic methods. However, the established synthetic methods suffer from low efficiency and low selectivity because the mechanism of the B–H bond condensatio...

Metal-boron triple bonds are rare due to the electron deficiency of boron. This study uncovers a simple electron-precise metal boryne complex, [BiBH]-, which is produced within an ion trap through chemical reactions of the open-shell BiB- anion with H2. Photoelectron imaging is used to investigate the electronic structure and chemical bonding of t...

We present an investigation on the structures and chemical bonding of two Bi-doped boron clusters BiBn− (n = 4, 5) using photoelectron spectroscopy and theoretical calculations. The electron affinities of BiB4 and BiB5 are measured to be 2.22(2) eV and 2.61(2) eV, respectively. Well-resolved photoelectron spectra are obtained and used to compare wi...

We report a study on the electronic structure and chemical bonding of the BiB molecule using high-resolution photoelectron imaging of cryogenically cooled BiB− anion. By eliminating all the vibrational hot bands, we can resolve the complicated detachment transitions due to the open-shell nature of BiB and the strong spin–orbit coupling. The electro...

Molecular anions with polar neutral cores can support highly diffuse dipole-bound states below their detachment thresholds due to the long-range charge-dipole interaction. Such nonvalence states constitute a special class of excited electronic states for anions and were observed in early photodetachment experiments to measure the electron affinitie...

Even though there is a critical dipole moment required to support a dipole-bound state (DBS), how molecular polarizability may influence the formation of DBSs is not well understood. Pyrrolide, indolide, and carbazolide provide an ideal set of anions to systematically examine the role of polarization interactions in the formation of DBSs. Here, we...

Copper has been found to be able to mediate the formation of bilayer borophenes. Copper-boron binary clusters are ideal model systems to probe the copper-boron interactions, which are essential to understand the growth mechanisms of borophenes on copper substrates. Here, we report a joint photoelectron spectroscopy and theoretical study on two di-c...

We report a temperature-controlled photoelectron imaging study of SbO2–, produced from a laser vaporisation source and cooled in a cryogenic 3D Paul trap. Vibrationally resolved photoelectron spectra are obtained for the ground state detachment transition, yielding the bending frequencies for both SbO2 and SbO2–. Franck-Condon simulations also allo...

The critical dipole moment to bind an electron was empirically determined to be 2.5 debye, even though smaller values were predicted theoretically. Herein, we report the first observation of a polarization-assisted dipole-bound state (DBS) for a molecule with a dipole moment below 2.5 debye. Photoelectron and photodetachment spectroscopies are cond...

Valence-bound molecular anions with polar neutral cores (μ > 2.5 D) can support highly diffuse dipole-bound states (DBSs) as electronically excited states just below the detachment threshold. Such weakly bound nonvalence excited states have little influence on the structure of the neutral core, and they usually have the same vibrational frequencies...

The 2-furanyloxy radical is an important chemical reaction intermediate in the combustion of biofuels and aromatic compounds. We report an investigation of its electronic and vibrational structures using photoelectron and photodetachment spectroscopy and resonant photoelectron imaging (PEI) of cryogenically cooled 2-furanyloxide anion. The electron...

The advent of ion traps as cooling devices has revolutionized ion spectroscopy as it is now possible to efficiently cool ions vibrationally and rotationally to levels where truly high-resolution experiments are now feasible. Here we report the first results of a new experimental apparatus that couples a cryogenic 3D Paul trap with a laser vaporizat...

Although the adiabatic potential energy surfaces defined by the Born-Oppenheimer approximation are the cornerstones for understanding the electronic structure and spectroscopy of molecular systems, nonadiabatic effects due to the coupling of electronic states by nuclear motions are common in complex molecular systems. The nonadiabatic effects were...

The concept of metalla-aromaticity proposed by Thorn-Hoffmann (Nouv. J. Chim. 1979, 3, 39) has been expanded to organometallic molecules of transition metals that have more than one independent electron-delocalized system. Lanthanides, with highly contracted 4f atomic orbitals, are rarely found in multiply aromatic systems. Here we report the disco...

The SO3 molecule and its radical anion SO3- are important chemical species atmospherically. However, their thermodynamic properties and electronic structures are not well known experimentally. Using cryogenically cooled anions, we have obtained high-resolution photoelectron images of SO3- and determined accurately the electron affinity (EA) of SO3...

Borophenes are atom-thin boron layers that can be grown on coinage metal substrates and have become an important class of synthetic 2D nanomaterials. The interactions between boron and substrates are critical to understand the growth mechanisms of borophenes. Here, we report an investigation of copper-boron interactions in the Cu 2 B 8 ⁻ bimetallic...

The hydridic hydrogen in nanogold catalysts has long been postulated as an important intermediate in hydrogenation reactions, but it has not been directly observed. Here, we report the synthesis of a new undecagold cluster with a bidentate phosphine ligand. The chelating effects of the bidentate ligand result in a more symmetric Au11 core with two...

Photoelectron spectroscopy combined with quantum chemistry has been a powerful approach to elucidate the structures and bonding of size-selected boron clusters (B n ⁻ ), revealing a prevalent planar world that laid the foundation for borophenes. Investigations of metal-doped boron clusters not only lead to novel structures but also provide importan...

It has been a long-standing challenge to create and identify the active sites of heterogeneous catalysts, because it is difficult to precisely control the interfacial chemistry at the molecular level. Here we report the synthesis and catalysis of a heteroleptic gold trihydride nanocluster, [Au22H3(dppe)3(PPh3)8]3+ [dppe = 1,2-bis(diphenylphosphino)...

High-resolution photoelectron imaging and photodetachment spectroscopy of cryogenically cooled pyrrolide and imidazolide anions are used to probe the electronic structure and spectroscopy of pyrrolyl and imidazolyl radicals. The high-resolution data allow the ground state vibronic structures of the two radicals to be completely resolved, yielding a...

Despite its electron deficiency, boron can form multiple bonds with a variety of elements. However, multiple bonds between boron and main-group metal elements are relatively rare. Here we report the observation of boron-lead multiple bonds in PbB2O– and PbB3O2–, which are produced and characterized in a cluster beam. PbB2O– is found to have an open...

Photoelectron spectroscopy and quantum chemistry studies are used to investigate the structures and bonding of AuB8–. Global minimum sturctural searches show that AuB8– possesses a chair-like structure, which can be...

Lanthanide (Ln) elements are generally found in the oxidation state +II or +III, and a few examples of +IV and +V compounds have also been reported. In contrast, monovalent Ln(+I) complexes remain scarce. Here we combine photoelectron spectroscopy and theoretical calculations to study Ln-doped octa-boron clusters (LnB8−, Ln = La, Pr, Tb, Tm, Yb) wi...

Negative ions do not possess Rydberg states but can have Rydberg-like nonvalence excited states near the electron detachment threshold, including dipole-bound states (DBSs) and quadrupole-bound states (QBSs). While DBSs have been studied extensively, quadrupole-bound excited states have been more rarely observed. 4-cyanophenoxide (4CP⁻) was the fir...

Boron displays many unusual structural and bonding properties due to its electron deficiency. Here we show that a boron atom in a boron monoxide cluster (B9O-) exhibits transition-metal-like properties. Temperature-dependent photoelectron spectroscopy provided evidence of the existence of two isomers for B9O-: the main isomer has an adiabatic detac...

We report the first joint anion photoelectron spectroscopy and theoretical study on how O2-binding affects the structures of medium even-sized gold clusters, Au n - (n = 20-34), a special size region that entails a variety of distinct structures. Under the temperature conditions in the current photoelectron spectroscopy experiment, O2-bound gold cl...

Valence-bound anions with a dipolar core can support dipole-bound states (DBSs) below the electron detachment threshold. The highly diffuse DBS observed is usually of σ symmetry with an s-like orbital. Recently, a π-type DBS was observed experimentally in the 9-anthrolate anion (9AT-) and it was shown to be stabilized due to the large anisotropic p...

Inverse-sandwich structures have been observed recently for dilanthanide boride clusters, in which two Ln atoms sandwich a monocyclic B x ring for x = 7-9. An interesting question is if larger B x rings are possible to form such inverse-sandwich clusters. Here we address this question by investigating La2B10- and La2B11- using photoelectron spectro...

We report an investigation of the 1-pyrenolate anion (PyO⁻) and the 1-pyrenoxy radical (PyO) using photodetachment spectroscopy and resonant photoelectron imaging of cryogenically cooled anions. The electron affinity of PyO is measured to be 2.4772(4) eV (19 980 ± 3 cm⁻¹) from high-resolution photoelectron spectroscopy. Photodetachment spectroscopy...

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 clu...

Anions cannot have Rydberg states, but anions with polar neutral cores can support highly diffuse dipole-bound states (DBSs) as a class of interesting electronically excited states below the electron detachment threshold. The binding energies of DBSs are extremely small, ranging from a few to few hundred wavenumbers and generally cannot support bou...

The boronyl anion (BO-) is isoelectronic to CO and CN-, but its metal complexes are rare. Here we report the observation of a boronyl complex with an early transition metal (TaBO-) produced by a laser vaporization supersonic cluster source. Its electronic structure and chemical bonding are investigated by photoelectron imaging and theoretical calcu...

Gold does not react with H2 to form bulk hydrides. Here we report the synthesis and characterization of a gold nanohydride protected by diphosphine ligands, [Au22H4(dppo)6]²⁺ [dppo=1,8‐bis(diphenylphosphino)octane]. The Au22 core consists of two Au11 units bonded by eight Au atoms not coordinated by the diphosphine ligands. The four H atoms are fou...

We report the observation of a symmetry-forbidden excited quadrupole-bound state (QBS) in the tetracyanobenzene anion (TCNB-) using both photoelectron and photodetachment spectroscopies of cryogenically-cooled anions. The electron affinity of TCNB is accurately measured as 2.4695 eV. Photodetachment spectroscopy of TCNB- reveals selected symmetry-a...

The hitherto largest gold nanohydride cluster, [Au22H4(dppo)6]²⁺, was synthesized and its structural, bonding, and chemical properties were elucidated. A wide range of hydrogen loss pathways were observed, providing critical information about hydrogen‐related chemical transformations catalyzed by gold nanoparticles. Abstract Gold does not react wi...

The diffuse electron in a dipole-bound state is spatially well separated from the valence electrons and is known to have negligible effects on the dipole-bound state's molecular structure. Here, we show that a dipole-bound state is observed in deprotonated 4-(2-phenylethynyl)-phenoxide anions, 348 cm-1 below the anion's detachment threshold. The ph...

We report an experimental and theoretical investigation of the electronic and optical properties of a series of icosahedral Au13 nanoclusters, protected by different halogen ligands (Cl, Br, I), as well as the 1,2-bis(diphenylphosphino)ethane (dppe) ligands. All three clusters are comprised of the same Au13 kernel with two halogens coordinated to t...

We report the observation of a π-type dipole-bound state (π-DBS) in cryogenically cooled deprotonated 9-anthrol molecular anions (9AT −) by resonant two-photon photoelectron imaging. A DBS is observed 191 cm −1 (0.0237 eV) below the detachment threshold, and the existence of the π-DBS is revealed by a distinct (s þ d)-wave photoelectron angular dis...

We report a high-resolution photoelectron imaging and photodetachment spectroscopy study of cryogenically-cooled IO−. The high-resolution photoelectron spectra yield a more accurate electron affinity (EA) of 2.3805(5) eV for IO, as well as a more accurate spin-orbit splitting energy between 2Π3/2 and 2Π1/2 of IO as 2093(5) cm-1. Photodetachment spe...

The B3 triangular unit is a fundamental bonding motif in all boron compounds and nanostructures. The isolated B3⁻ cluster has a D3h structure with double σ and π aromaticity. Here, we report an investigation of the bonding between a B3 cluster and a 3d transition metal using high-resolution photoelectron imaging and computational chemistry. Photoel...

Multiple bonds between boron and transition metals are known in many borylene (:BR) complexes via metal dπ→BR back‐donation, despite the electron deficiency of boron. An electron‐precise metal–boron triple bond was first observed in BiB2O⁻ [Bi≡B−B≡O]⁻ in which both boron atoms can be viewed as sp‐hybridized and the [B−BO]⁻ fragment is isoelectronic...

We report a photodetachment spectroscopy and high-resolution resonant photoelectron imaging study of cryogenically cooled 2-naphthoxide anions (C10H7O⁻). The photodetachment spectrum revealed a dipole-bound state (DBS) 202(4) cm⁻¹ below the detachment threshold and 38 resonances corresponding to the vibrational levels of the DBS. By tuning the deta...

The discovery of borospherenes unveiled the capacity of boron to form fullerene-like cage structures. While fullerenes are known to entrap metal atoms to form endohedral metallofullerenes, few metal atoms have been observed to be part of the fullerene cages. Here we report the observation of a class of remarkable metallo-borospherenes, where metal...

To bend or not to bend: Photoelectron spectroscopy and ab‐initio calculations show that IrB2O⁻ has a bent (⁻OB)Ir≡B structure and ReB2O⁻ has a linear structure, [Re≡B−B≡O]⁻. The latter is the first example of a transition‐metal borylyne complex. Abstract Multiple bonds between boron and transition metals are known in many borylene (:BR) complexes...

Boron can form strong bonds with transition metals in diatomic metal borides (MB), but the nature of the chemical bonding has not been well understood. Recently, a quadruple bond was discovered in Rh≣B, consisting of two σ bonds formed between the Rh 4dz² and B 2s/2p orbitals and two π bonds between the Rh 4dxz/4dyz and the B 2px/2py orbitals. The...

We report a study of the structure and bonding of a transition metal doped boron cluster, MnB6−, using high-resolution photoelectron imaging and quantum chemical calculations. Vibrationally-resolved photoelectron spectra indicate a significant geometry change between the anionic and neutral ground states of MnB6. The electron affinity of MnB6 is me...

Möbius aromaticity was developed for twisted-annulenes with electron counting rules opposite to those of Hückel aromaticity. The introduction of transition-metals makes it possible for planar cyclic systems to exhibit Möbius aroma-ticity. Here we report the first planar monocyclic metallaboron systems with Möbius aromaticity. The structures and bon...

The maximum bond order between two main-group atoms was known to be three. However, it has been suggested recently that there is quadruple bonding in C2 and analogous eight-valence electron species. While the quadruple bond in C2 has aroused some debates, an interesting question is: are main-group elements capable of forming quadruple bonds? Here w...

Since the discovery of the B40 borospherene, research interests have been directed to the structural evolution of even larger boron clusters. An interesting question concerns if the borospherene cages persist in larger boron clusters like the fullerenes. Here we report a photoelectron spectroscopy (PES) and computational study on the structures and...

We report photodetachment spectroscopy and high-resolution photoelectron imaging of para-halogen substituted phenoxide anions, p-XC6H4O− (X = F, Cl, Br, I). The dipole moments of the corresponding neutral radicals (p-XC6H4O) are calculated to be 2.56 D, 2.81 D, 2.96 D, 3.19 D, from X = F to I, providing a series of similar molecules to allow the ex...

Valence-bound anions with polar neutral cores (μ > ~2.5 D) can support dipole-bound excited states below the detachment threshold. These dipole-bound states (DBSs) are highly diffuse and the weakly bound electron in the DBS can be readily autodetached via vibronic coupling. Excited DBSs can be observed in photodetachment spectroscopy using a tunabl...

We report the observation of a dipole-bound state (DBS) 659 cm-1 below the electron detachment threshold of cryogenically-cooled deprotonated 4,4′-biphenol anion (bPh−) and nineteen of its lowest vibrational levels. Resonant two-photon photoelectron imaging (R2P-PEI) via the vibrational levels of the DBS display a sharp peak with a constant binding...

We report the observation of the first inverse triple-decker complex in a tri-lanthanide-doped boron cluster. Photoelectron spectroscopy of La3B14– reveals well-resolved photodetachment transitions. Quantum chemical studies show that the most stable structure of the La3B14– cluster exhibits a tilted La–B8–La–B8–La inverse triple-decker structure wi...

Transition-metal-centered monocyclic boron wheel clusters (M©Bnq) represent a family of interesting borometallic compounds with double aromaticity. A variety of early and late transition metal atoms have been found to form such structures with high symmetries and various ring sizes. Here we report a combined photoelectron spectroscopy and quantum c...

In a high‐resolution photoelectron imaging and theoretical study of the IrB3⁻ cluster, two isomers were observed experimentally with electron affinities (EAs) of 1.3147(8) and 1.937(4) eV. Quantum calculations revealed two nearly degenerate isomers competing for the global minimum, both with a B3 ring coordinated with the Ir atom. The isomer with t...

Tautomers of the nucleobases play fundamental roles in spontaneous mutations of DNA. Tautomers of neutral cytosine have been studied in the gas phase, but much less is known about charged species. Here, we report the observation and characterization of three tautomers of deprotonated cytosine anions, [trans‐keto‐amino‐N3H‐H8b] (tKAN3H8b⁻), [cis‐ket...

We report a high‐resolution photoelectron imaging and theoretical study of the IrB3‾ cluster. Two isomers are observed experimentally with electron affinities (EAs) of 1.3147(8) eV and 1.937(4) eV. Quantum calculations reveal two nearly degenerate isomers competing for the global minimum, both with a B3 ring coordinated with the Ir atom. One of the...

Chirality plays an important role in nature. Nanoclusters can also exhibit chiral properties. We report herein a joint experimental and theoretical investigation on the geometric and electronic structures of the B31 and B32 clusters, using photoelectron spectroscopy in combination with first-principles calculations. Two degenerate quasi-planar ch...

Tautomers of the nucleobases play fundamental roles in spontaneous mutations of DNA. Tautomers of neutral cytosine have been studied in the gas phase, but much less is known about charged species. Here we report the observation and characterization of three tautomers of deprotonated cytosine anions, [trans‐keto‐amino‐N3H‐H8b] (tKAN3H8b–), [cis‐keto...

Since the discovery of the first drum-like CoB16⁻ complex, metal-doped drum-like boron nanotubular structures have been investigated with various metal dopants and different tubular size, forming a new class of novel nanostructures. The CoB16⁻ cluster was found to be composed of a central Co atom coordinated by two fused B8 rings in a tubular struc...

Among coinage-metal nanoclusters with 55-atoms, only Ag55− and Cu55− are the geometric magic-number clusters, as both exhibit icosahedral symmetry. Au55−, however, exhibits much lower symmetry due largely to the strong relativistic bonding effect. In this study, we collect much larger population (> 10000 isomers) of low-energy isomers of Au55− to A...

Bismuth boride is a heavy member of the III-V semiconductors. Although there have been some theoretical interests in this material, it has not been synthesized experimentally. Here, we report a high-resolution photoelectron imaging study on a series of boron-bismuth binary clusters, Bi 2 B n⁻ (n = 2-4), produced by laser vaporization of a B/Bi mixe...

A facile synthesis of heavy alkali metal octahydrotriborates (MB3H8; M=K, Rb, and Cs) has been developed. It is simply based on reactions of the pure alkali metals with THF⋅BH3, does not require the use of electron carriers or the addition of other reaction media such as mercury, silica gel, or inert salts as for previous procedures, and delivers t...

A facile synthetic method of heavy alkali metal octahydrotriborates (MB3H8, M = K, Rb, and Cs) has been developed simply through reactions of pure alkali metals with THF·BH3 without using electron carriers or other reaction media, such as mercury, silca gel or inert salts as done previously, at room temperature with very high yields. However, no di...

Despite the importance of bulk lanthanide borides, nanoclusters of lanthanide and boron have rarely been investigated. Here we show that lanthanide-boron binary clusters, La2B x -, can form a new class of inverse-sandwich complexes, [Ln(η x -B x )Ln]- (x = 7-9). Joint experimental and theoretical studies reveal that the monocyclic B x rings in...

Among coinage metal nanoclusters with 55 atoms, only Ag55– and Cu55– are the geometric magic-number clusters, as both exhibit icosahedral symmetry. Au55–, however, exhibits much lower symmetry due largely to the strong relativistic bonding effect. In this study, we collect a much larger population (>10,000 isomers) of low-energy isomers of Au55– to...

Photoelectron spectroscopy in conjunction with theoretical calculations has been used to investigate size-selected boron clusters, uncovering interesting structures and bonding.

Lanthanide elements typically exhibit a +III oxidation state (OS) in chemical compounds with a few in +IV or even +V OS. Although lanthanides with +II OS have been observed recently in organometallic compounds, +I OS is extremely rare. Using a joint photoelectron spectroscopy and quantum theoretical study, we have found two low OS lanthanides in do...

Antiaromaticity, as introduced in 1965, usually refers to monocyclic systems with 4n π electrons. This concept was extended to all‐metal molecules after the observation of Li3Al4− in the gas phase. However, the solid‐phase counterparts have not been documented to date. Herein, we describe a series of all‐metal antiaromatic anions, [Ln(η4‐Sb4)3]3−(L...

A dipolar molecule can weakly bind an electron in a diffuse orbital. However, the spin-orbit coupling between this weakly-bound electron and the electrons in the molecular core is not known. Here we probe this coupling using the linear C2P⁻ anion with a ³Σ⁺ ground state, which possesses dipole-bound excited states because neutral C2P (²Π) has a suf...

We report photodetachment and resonant photoelectron-imaging studies of cryogenically cooled phenoxide (C6H5O-) and thiophenoxide (C6H5S-) anions. In a previous study [H. T. Liu et al. Angew. Chem., Int. Ed. 52, 8976 (2013)], a dipole-bound excited state was observed for C6H5O- at 97 cm-1 below the detachment threshold. Eight resonant photoelectron...