Literature Seminar

Modern Alchemy ??
the Chemistry of~ Cluster & Nanoparticle ~2011. 06.07. (Tue)Takuya Matsumoto (M1)

Introduction 1Alchemy
In a narrow sense, Alchemy is an ancient
tradition the objective of which is turningbase metals, such as lead or mercury, into
noble metals, especially gold, by chemical
reactions.
During it’s trials, many chemicals have beenfound and many equipments developed.
These accomplishments are succeeded bytoday’s chemistry.

Figure. Alchemist in medieval Europe(a cover picture of Aldrich catalog 2010)

Introduction 2
Modern Nucleosynthesis (Physics)
Today, atoms can be synthesized byaccelerators.
In fact, you can synthesized gold
from lead.
Lead accelerated up to 70% of thevelocity of light collides withberyllium and then turns into gold.

Figure. The Large Hadron Collider, the world's
largest and highest-energy particle accelerator

But, even if you use the strongest lead – beam, you will spend a
hundred trillion yen and a million year only to get 1g gold!!!

Today’s topic【1】 Super Atom

Al13 = Cl ?
【2】 Transition Metal Carbides

WC = Pt ??
【3】 Bimetallic Nanoparticles(Rh + Ag) ÷ 2 = Pd ???

Super Atom

What’s Super Atom ? (1)The formation of strong bonds or closed electronic
shells by groups of atoms can create
species that react as if they were one atom.
Familiar examples include ions such as CN–, which react as if it were halogens
in so many cases that it is referred to as ‚pseudohalogens.‛

C60
Figure | (left) A comparison of
the energy levels (shells) for
an atom and for a jellium
sphere. (right) Molecularorbital (MO) diagram for Al13-Super Atom

What’s Super Atom ? (2)Atomic orbital

Jellium orbital

Super Atom

What’s Super Atom ? (3)The superatom suggestion is that free electrons in the cluster occupy a new
set of orbitals that are defined by the entire group of atoms rather than byeach individual atom separately.

Super Atom

Discovery of Super Atom

Figure | Sodium cluster
Knight, W. D. et al., Phys. Rev. Lett. 1984, 52, 2141.
Castleman, A. W. et al., J. Chem. Phys. 1989, 91, 2753.

Figure | Aluminum cluster

Equipment

Figure | The Fast Flow Reactor.
Castleman, A. W. et al., Science 2009, 323, 492.

Super AtomIs Super Atom really ‘Super’ ? (1)Electron valence of AtomAl (3s2 3p1) Nb (4d4 5s1)

V (3d3 4s2)

Sum of electron in Cluster
1s2, 1p6, 1d10, 2s2, 1f14, 2p6, 1g18 ・・・
Al13- (40)

Al23- (70)

Al4Nb- (18)

Al5V- (18) (V provide two s electron)
Al7V- (8) (Al provide one p electron)
Al6Nb- (20) (Nb provide one s electron)
Figure | Substituting test toinvestigate the importance of theelectronic contribution to stability

Al6V- ???

Castleman, A. W. et al., J. Am. Chem. Soc. 1990, 112, 5673.

Super AtomIs Super Atom really ‘Super’ ? (2)Figure | (left) Spherical shell closings and the corresponding closed
shell neutral and negative clusters of trivalent Al. (middle) Photoelectron spectra of
Alx- (x = 1 ～12). (right) Photoelectron spectra of the expected closed shell
Alx- anions compared to those of the Alx+1- clusters.
Wang, L. S. et al., Phys. Rev. Lett. 1998, 81, 1909.

Super Atom

Al13 is ‘Ultra’ Super Atom

EA: electron affinity, IP: ionizing potential
Figure | (left) The calculated absolute HOMO and LUMO levels of the Aln- clusters as afunction of size (right) Ionization potentials and electron affinities for Aln (n=11−15).
A: Adiabatic, V: Vertical.

Among the elements of periodic table,
the highest EA element is Cl (3.61 eV) and the lowest 2nd IP element is Ba (10.0 eV).
Castleman, A. W. et al., Science 2009, 323, 492.
Han, Y. K. et al., J. Am. Chem. Soc. 2008, 130, 2.

Super Atom

Why is Al13- especially so stable?
Rao, B. K.; Jena, P., J. Chem. Phys. 1999, 111, 1890.

icosahedronSuper Atom

Reactions of Al13- cluster (1)Reaction with HI

Al13 is a SUPERHALOGENE!!!
Figure | (upper left) Electron charge density of the HOMO
in an Al13K cluster. Most of the electron density is locatedaround the Al13 cluster. (upper middle & right) Charge
density of the HOMO in Al13I- showing that most of thecharge is located around the Al13 moiety. (left) Mass
spectra showing the reaction of aluminumclusters with HI:(A)0 sscm, (B) 25 sccm, (C) and 200 sccm of 10% HI seededin He.
Castleman, A. W. et al., Science 2004, 304, 84.

Super AtomReactions of Al13- cluster (2)Reaction with I2 （１）Figure | Mass spectra of (A) Al cluster anions(B) reacted with I2 vapor and then (C) etchedby O2. Peaks shaded green fall into the Al13Ix–family, whereas peaks shaded blue fall into theAl14Ix– family.

Castleman, A. W. et al., Science 2005, 307, 231.

Super Atom

Reactions of Al13- cluster (3)Reaction with I2 （２）Al13Ix– families

Al14Ix– families

Super Atom

Recent examples of Magic cluster (1)Superatomic Architectures

Figure | (left) Structure binding energy (B.E.),
HOMO-LUMO gap (Gap), and ionization potentials(I.P.) for Al13(K3O) and Al13(Na3O) series. (upper)
Assemblies of (A) Al13K3O and (B) Al13Na3O
molecules
Khanna, S. N. et al., J. Am. Chem. Soc. 2007, 129, 10189.

Super Atom

Recent examples of Magic cluster (2)Designer Magnetic Superatom

Figure | (left) Ground-state geometries of VNan and VCsn clusters. a, VNan (n=1～12)
clusters. b, VCsn (n=1～12) clusters. Na: red, Ce: blue, V: grey. (right) Energetic andmagnetic trends of VNan and VCsn clusters. a,b, Variation of the gain in energy caused byalkali addition (DEA) with n in the (a) Vnan and (b) VCsn clusters. c,d, Variation of themagnetic moments (m) with n in the (c) Vnan and (d) VCsn clusters. The magnetic momentof the vanadium atom is also given as reference (dashed line).
Khanna, S. N. et al., Nature Chemistry 2009, 1, 310.

Super Atom

Recent examples of Magic cluster (3)Designer Magnetic Superatom & the Ligand-Stabilized Magic Gold Cluster

Jin, R. et al., J. Am. Chem. Soc. 2008, 130, 5883.

Khanna, S. N. et al., Nature Chemistry 2009, 1, 310.

Figure | (upper) Crystal structure of aAu25(SR)18- cluster (R = phenylethylgroup): (A) the icosahedral Au13 core; (B)the Au13 core plus the exterior 12 Au
atoms; (C) the whole Au25 cluster
protected by 18 thiolate ligands (S:magenta, Au; yellow). (lower) Total and net
spin electron density and density ofstates (DOS) of the MnAu24(SH)18 cluster.
(a) Total electron density, (b) net spinelectron density and (c) DOS obtained bybroadening the molecular levels by
Gaussians of width 0.017 eV (Mn: blue, Au:gold, S: yellow, H: white). The delocalized 1S
and 1P electronic shells and localized 3d
atomic orbitals are marked in orange,green and blue areas, respectively.

Super AtomRecent examples of Magic cluster (4)the Ligand-Stabilized Magic Gold Cluster
Au102 (p-MBA)44[Au69(PH3)20Cl12]-1

Jadzinsky, P. D. et al., Science 2007, 318, 430.

Walter, M. et al., Chem. Sci. ASAP.

Figure | (left) X-ray crystal structure determination of the Au102 (p-MBA)44 nanoparticle.
Au: yellow, p-MBA: framework with small spheres (S: cyan, C: gray, O: red) (p-MBA = pmercaptobenzoic acid). (right) (b) Structure of the [Au69(PH3)20Cl12]-1, (Au: yellow, Cl: green,
P: blue, H: white) and (c) the gold-core and (d) the split layers of different height
perpendicular to the paper plane.

Super Atom

Further study of Super AtomMini review
Castleman, A. W.; Khanna , S. N. J. Phys. Chem. C 2009, 113, 2664.
Reactions of Aluminum clusters withHClSchnockel, H. et al., J. Am. Chem. Soc., 2006, 128, 7904.
O2Schnockel, H. et al., Science, 2008, 319, 438.
Khanna, S. N. et al., J. Am. Chem. Soc. 2007, 51, 16098.
H2O
Castleman, A. W. et al., Science, 2009, 323, 492.
Is Superatom model realy suitable?
Han, Y. K. et al., J. Am. Chem. Soc. 2008, 130, 2.
Reimers, J. R.; Cankurtaran, B. O et al., J. Am. Chem. Soc. 2010, 132, 8378.
Han, Y. K. et al., J. Am. Chem. Soc. 2011, 133, 6090.

Super Atom

Summary of Super Atom
Although it seems too simple, Jellium
closing shell model explains well.
As far as I research, Al13 is the only nonligand-stabilized cluster which has beenstudied enthusiastically and therefore canbe regarded as ‘Superatom’.
To obtain extra ordinal stability, which isnecessary for the cluster functioning as‘Superatom’, the cluster needs bothclosing electron shell and highly
symmetric geometry.
This steric demand will cause mismatch
between clusters and small but relatively
complex molecule.

Transition Metal Carbides

What’s Transition Metal Carbides?

Figure | Calcium carbide

Transition Metal Carbides

Precedent work
Platinum-Like Behavior of Tungsten Carbide in Surface Catalysis

1.

2.

3.

Levy, R. B.; Boudart, M. Science, 1973, 181, 547.

Transition Metal Carbides

TMC & Pt-Group Metal Surface

Figure | the probe reactions to determine
whether TMC surfaces possessed the‚Pt-like‛ chemical properties.

① Ti/C showed the conversion of ethylene to ethylidyne.
② Mo/C showed the selective activation of the R-C-H bond of cis- andtrans-2-butene to 2-butyne.
③&④ TMCs showed the selective dehydrogenation of cyclohexene andcyclohexadiene to benzene.
The formation of carbides on groups 4-6 metals reduces the degree ofinteraction between adsorbates and TMC surfaces, leading to a modified
surface activity that more closely esembles the Pt-group metals than theparent metals.
Hwu, H. H.; Chen, J. G. Chem. Rev., 2005, 105, 185.

Transition Metal Carbides

WC- = Pt- ?

Figure | Energy level diagrams, binding
energy (BE) spectra, and raw
hotoelectron images of (upper left) Pt& WC-, (upper right) Ni- & TiO-, (left)
Pd- & ZrO-.

Castleman, A. W. et al., P.N.A.S 2010, 107, 975.

Transition Metal Carbides

Summary of TMC
Although carbon atom changes theproperties of early transition metals
and TMCs show similar catalytic
functionalities as Pt-group metals, theelectronic surface of both arecompletely different.
And, there aren’t any alchemicalelements in TMCs.
Recently, however, the reports isappearing that show the similarity ofthe photoelectron signatures andangular distributions in the acquired
Figure | Three dimensional periodic
images between negative ions of thetable of cluster elements!
group 10 noble metals and that of
their isoelectronic early transition
metal heterogeneous diatomic molecule.

Bimetallic Nanoparticles

What’s Bimetallic Nanoparticles?

Increasingly, the shape, size, composition, and architecture of a nanoparticle
are being recognized as important control parameters for tailoring new
bimetallic nanoparticle systems.
Kunitake, T. et al., J. Am. Chem. Soc. 2003, 125, 11034.
Ferrando, R. et al. Chem. Rev., 2008, 108, 845.

Bimetallic Nanoparticles

Pd-Ni
Hiyama coupling

Sonogashira coupling

Rothenberg, G. et al., Phys. Chem. Chem. Phys. 2006, 8, 151.

Hyeon, T. et al., J. A. C. S. 2004, 126, 5026.

Bimetallic Nanoparticles

Pd-Au

Figure | (upper left) Vinyl acetate (VA) formation rates(TOFs) as a function of Pd coverage on Au(100) andAu(111). (left) Schematic for VA synthesis fromacetic acid and ethylene. The optimized distance between
the two active centers for the coupling of surface
ethylenic and acetate species to form VA is estimatedto be 3.3 A°. With lateral displacement, coupling of an
ethylenic and acetate species on a Pd monomer pair ispossible on Au(100) but implausible on Au(111). (upperright) Comparison of the catalytic activity for alcoholoxidation to the corresponding aldehyde. Substrates
are oxidized without solventunless specified.
Goodman, D. W. et al., Science, 2005, 310, 291.
Hutchings, G. J. et al., Science, 2006, 311, 362.

Bimetallic Nanoparticles

Ru-Pt (1)Bimetallic Nanoparticles

Pd-Pt

Figure | (upper right) PC isotherms of Pd (red), Pt (blue), Pd79Pt21 core/shell (brown) andPd79Pt21 alloy (green). (lower right) PC isotherms of Pd, Pd92Pt8, Pd79Pt21, and Pd50Pt50 alloy.

Kitagawa, H. et al., J. Am. Chem. Soc. 2008, 130, 1818.
Kitagawa, H. et al., J. Am. Chem. Soc. 2010, 132, 5576.

Bimetallic Nanoparticles(Rh + Ag) ÷ 2 = Pd?

Figure | (left) (a) HAADF-STEM image, (b) Ag-L STEM-EDX map, and (c) Rh-L STEM-EDX
map obtained from a group of prepared Ag50Rh50 nanoparticles. (d) Reconstructed
overlay image of the maps shown in panels (b) and (c) (Rh; green, Ag: orange). The scalebars correspond to 10 nm. (right) Pressure-composition isotherms of (1) Ag40Rh60, (2)Ag50Rh50, and (3) Ag70Rh30 nanoparticles (open symbol: absorption at 303 K, close
symbol: desorption at 303 K).
Kusada, K.: Kitagawa, H. et al., J. Am. Chem. Soc. 2010, 132, 15896.

Bimetallic Nanoparticles

Summary of Bimetallic Nanoalloy
The shape, size, composition, andarchitecture of a nanoparticle arebeing recognized as important
control parameters for tailoringnew bimetallic nanoparticlesystems.
And, analyzing and tuning theseparameter are just enabledrecently.
In many cases, the minor metals
serve as ‘spice’.
But in some cases, two metals aremixed to show completely newproperties.
Yamamoto, K.; Nishihara, H. et al. Angew. Chem. Int. Ed. ASAP

SummaryCluster & Nanoparticle
have different properties
from bulk metals andhomogeneous catalysts.
Studies of these elements
are just getting started!

How do you think?

The Most Beautiful Periodic Table Poster in the World
By Theodore Gray