Metal core bonding motifs of monodisperse icosahedral Au13 and larger Au monolayer-protected clusters as revealed by X-ray absorption spectroscopy and transmission electron microscopy

The atomic metal core structures of the subnanometer clusters Au13[PPh3]4[S(CH2)11CH3]2Cl2 (1) and Au13[PPh3]4[S(CH2)11CH3]4 (2) were characterized using advanced methods of electron microscopy and X-ray absorption spectroscopy. The number of gold atoms in the cores of these two clusters was determined quantitatively using high-angle annular dark field scanning transmission electron microscopy. Multiple-scattering-path analyses of extended X-ray absorption fine structure (EXAFS) spectra suggest that the Au metal cores of each of these complexes adopt an icosahedral structure with a relaxation of the icosahedral strain. Data from microscopy and spectroscopy studies extended to larger thiolate-protected gold clusters showing a broader distribution in nanoparticle core sizes (183 +/- 116 Au atoms) reveal a bulklike fcc structure. These results further support a model for the monolayer-protected clusters (MPCs) in which the thiolate ligands bond preferentially at 3-fold atomic sites on the nanoparticle surface, establishing an average composition for the MPC of Au180[S(CH2)11CH3]40. Results from EXAFS measurements of a gold(I) dodecanethiolate polymer are presented that offer an alternative explanation for observations in previous reports that were interpreted as indicating Au MPC structures consisting of a Au core, Au2S shell, and thiolate monolayer.     

Synthetic strategies for the surface functionalisation of gold nanoparticles with metals and metal clusters

The reaction of the new ditopic thiol-phosphine compound HS(CH(2))(11)OOCC(6)H(4)PPh(2) (L) with an excess of dodecanethiol-protected gold nanoparticles gave the asymmetric gold complex [CH(3)(CH(2))(11)SAuPPh(2)C(6)H(4)COO(CH(2))(11)SH] (4), but no phosphine-protected gold nanoparticles were formed. However, by blocking the phosphine function in L with metal fragments, we have been able to produce gold nanoparticles functionalised with AuCl- and cluster [Fe(2)(CO)(7)Au] units on the surface by the method of ligand-place exchange reaction.     

Synthesis and electrochemical and spectroscopic characterization of biicosahedral Au25 clusters

The synthesis and electrochemical and spectroscopic characterization of biicosahedral Au(25) clusters with a composition of [Au(25)(PPh(3))(10)(thiolate)(5)Cl(2)](2+) are described. The biicosahedral Au(25) clusters protected with various types of thiol ligands including alkanethiols, 2-phenylethanethiol, 11-mercaptoundecanoic acid, and 11-mercapto-1-undecanol were synthesized in high yields using a one-step, one-phase procedure in which Au(PPh(3))Cl is reduced with tert-butylamine-borane in the presence of the thiol ligand in a 3:1 v/v chloroform/ethanol solution. All biicosahedral Au(25) clusters prepared exhibit characteristic optical absorption and photoluminescence properties. The emission energy is found to be substantially smaller than the optical absorption energy gap of 1.82 eV, indicating a subgap energy luminescence. The electrochemical HOMO-LUMO gap (~1.54 eV) of the clusters is also substantially smaller than the optical absorption energy gap but rather similar to the emission energy. These electrochemical and optical properties of the biicosahedral Au(25) clusters are distinctly different from those of the Au(25)(thiolate)(18) clusters.     

Alkylthio bridged 44 cve triangular platinum clusters: synthesis, oxidation, degradation, ligand substitution, and quantum chemical calculations

Acetylplatinum(II) complexes trans-[Pt(COMe)Cl(L)2] (L = PPh3, 2a; P(4-FC6H4)3, 2b) were found to react with dialkyldisulfides R2S2 (R = Me, Et, Pr, Bu; Pr = n-propyl, Bu = n-butyl), yielding trinuclear 44 cve (cluster valence electrons) platinum clusters [(PtL)3(mu-SR)3]Cl (4). The analogous reaction of 2a-b with Ph2S2 gave SPh bridged dinuclear complexes trans-[{PtCl(L)}2(mu-SPh)2] (5), whereas the addition of Bn2S2 (Bn = benzyl) to 2a ended up in the formation of [{Pt(PPh3)}3(mu3-S)(mu-SBn)3]Cl (6). Theoretical studies based on the AIM theory revealed that type 4 complexes must be regarded as triangular platinum clusters with Pt-Pt bonds whereas complex 6 must be treated as a sulfur capped 48 ve (valence electrons) trinuclear platinum(II) complex without Pt-Pt bonding interactions. Phosphine ligands with a lower donor capability in clusters 4 proved to be subject to substitution by stronger donating monodentate phosphine ligands (L' = PMePh2, PMe2Ph, PBu3) yielding clusters [(PtL')3(mu-SR)3]Cl (9). In case of the reaction of clusters 4 and 9 with PPh2CH2PPh2 (dppm), a fragmentation reaction occurred, and the complexes [(PtL)2(mu-SMe)(mu-dppm)]Cl (12) and [Pt(mu-SMe)2(dppm)] (13) were isolated. Furthermore, oxidation reactions of cluster [{Pt(PPh3)}3(mu-SMe)3]Cl (4a) using halogens (Br2, I2) gave dimeric platinum(II) complexes cis-[{PtX(PPh3)}2(mu-SMe)2] (14, X = Br, I) whereas oxidation reactions using sulfur and selenium afforded chalcogen capped trinuclear 48 ve complexes [{Pt(PPh3)}3(mu3-E)(mu-SMe)3] (15, E = S, Se). All compounds were fully characterized by means of NMR and IR spectroscopy, microanalyses, and ESI mass spectrometry. Furthermore, X-ray diffraction analyses were performed for the triangular cluster 4a, the trinuclear complex 6, as well as for the dinuclear complexes trans-[{Pt(AsPh3)}2(mu-SPh)2] (5c), [{Pt(PPh3)}2(mu-SMe)(mu-dppm)]Cl (12a), and [{{PtBr(PPh3)}2(mu-SMe)2] (14a).     

Gold and silver complexes with the ferrocenyl phosphine FcCH2PPh2

Linear gold(I) and silver(I) complexes with the ferrocenyl phosphine FcCH2PPh2 [Fc = (eta5-C5H5)Fe(eta5-C5H4)] of the types [AuR(PPh2CH2Fc)], [M(PPh3)(PPh2CH2Fc)]OTf, and [M(PPh2CH2Fc)2]OTf (M = Au, Ag) have been obtained. Three-coordinate gold(I) and silver(I) derivatives of the types [AuCl(PPh2CH2Fc)2] and [M(PPh2CH2Fc)3]X (M = Au, X = ClO4; M = Ag, X = OTf) have been obtained from the corresponding gold and silver precursors in the appropriate molar ratio, although some of them are involved in equilibria in solution. The crystal structures of [AuR(PPh2CH2Fc)] (R = Cl, C6F5), [AuL(PPh2CH2Fc)]OTf (L = PPh3, FcCH2PPh2), [Au(C6F5)3(PPh2CH2Fc)], and [Ag(PPh2CH2Fc)3]OTf have been determined by X-ray diffraction studies.     

Synthesis, structure, luminescence, and theoretical studies of tetranuclear gold clusters with phosphinocarborane ligands

Treatment of the tetranuclear gold cluster [Au4((PPh2)2C2B9H10)2(AsPh3)2] (1), which contains the nido-carborane-diphosphine [7,8-(PPh2)2C2B9H10]-, with various tertiary phosphines leads to derivatives [Au4((PPh2)2C2B9H10)2-(PR3)2] (PR3 = PPh3 (2), P(4-MeC6H4)3 (3), P(4-OMeC6H4)3 (4)). The X-ray crystal structure of complex 4 shows a tetrahedral framework of gold atoms, two of which are chelated by the diphosphine, and two are coordinated to one monophosphine ligand each. These compounds are very stable and are obtained in high yield. MP2 calculations suggest that the two types of chemically nonequivalent gold atoms can be formally assigned as Au(I) (those attached to the arsines or phosphines) and Au(0) (those bonded to the anionic diphosphine) and emphasize the role of correlation in the gold-gold interactions. The compounds are luminescent. The emission is assigned to a gold-centered spin-forbidden transition; the assignment of the oxidation state of the gold centers on this basis leads to results coincident with those obtained by theoretical calculations.     

Synthesis and characterisation of high-nuclearity osmium-silver mixed-metal clusters

The reaction of the triosmium cluster anion, [Os(3)(micro-H)(CO)(11)][PPN] (PPN = [N(PPh(3))2]+), with [AgPF(6)] in the presence of [Ir(PPh(3))2(CO)Cl] in THF at room temperature affords two new high-nuclearity osmium-silver clusters, [Os(13)Ag(9)(CO)48][PPN] (1) and [Os(9)Ag(9)(micro3-O)2(CO)30][PPN] (2), and an iridium complex, [Ir(PPh(3))2(CO)Cl(O(2))] (3).     

Synthesis, characterization, and X-ray structure determination of [Au18(P)2(PPh)4(PHPh)(dppm)6]Cl3

The reaction of [(AuCl)2dppm] (dppm=Ph2PCH2PPh2) with PhP(SiMe3)2 and P(SiMe3)3 leads to the formation of the gold cluster compound [Au18(P)2(PPh)4(PHPh)(dppm)6]Cl3 (1). The crystal structure investigation shows a central Au7P2 unit formed by two P centered gold tetrahedra sharing the central gold corner. This central unit is surrounded by a 10-membered Au5P5 ring which, together with the remaining six gold atoms, builds two Au4P rectangular and two Au3P trigonal pyramids. The different structure motifs are connected by the phosphine ligands. The compound has been characterized using microanalysis, IR spectroscopy, ESI-MS, and 31P NMR techniques. Luminescence measurements have also been carried out.     

Preparation and substitution chemistry of [Bu4N]2[W6Cl8(p-OSO2C6H4CH3)6]. A useful precursor for pseudohalide, acetate, and organometallic complexes containing the [W6Cl8](4+) core

The tosylate (p-toluenesulfonate) cluster [Bu4N]2[W6Cl8(p-OSO2C6H4CH3)6] (1) has been prepared and characterized by IR and NMR spectroscopy, elemental analysis, and an X-ray crystal structure. This cluster complex is shown to be a useful starting material for the preparation of pseudohalide clusters, [Bu4N]2[W6Cl8(NCQ)6] (Q = O (2), S (3), and Se (4)), in high yields. Cluster 1 also serves as a precursor to the new cluster compounds: [Bu4N]2[W6Cl8(O2CCH3)6] (5), [Bu4N]2[W6Cl8((mu-NC)Mn(CO)2(C5H5))6] (6), [W6Cl8((mu-NC)Ru(PPh3)2(C5H5))6][ p-OSO2C6H4CH3]4 (7), and [W6Cl8((mu-NC)Os(PPh3)2(C5H5))6][ p-OSO2C6H4CH3]4 (8). X-ray crystal structures are reported for 1, 4, and 5.     

Unprecedented gold-tellurolate clusters [Au(8)(mu-TeR)(8)(PR'(3))(4)

The reaction of [AuCl(PR'3)] with KTeR, prepared from RTeTeR and K-selectride, gives the gold-tellurolate clusters [Au8(mu-TeR)8(PR'3)4] (R = Ph, Tol; PR'3 = PPh3, PPh2py) in high yield. This result contrasts with the one obtained from the reaction with thiolates or selenolates, from which mononuclear complexes are synthesized. The structures of these species have been determined and consist on three layers of gold and tellurium atoms in the ratio Au3Te2:Au2Te4:Au3Te2. There are short gold...gold interactions ranging from 2.9463(7) to 3.31132(7) A, and the clusters are composed of di- and tri-coordinated gold centers. The result is unprecedented in gold-chalcogenolate chemistry from which mononuclear species are expected and represents one of the few examples of gold-tellurolate derivatives. These species show an interesting luminescent behavior in the solid state (at 77 K) and in solution (both at 298 and 77 K).     

Group 11 complexes with unsymmetrical P,S and P,Se disubstituted ferrocene ligands

The reaction of the unsymmetrical ligands 1-diphenylphosphino-1'-(phenylsulfanyl)ferrocene and 1-diphenylphosphino-1'-(phenylselenyl)ferrocene, Fc(EPh)PPh2(E = S, Se), with several group 11 metal derivatives leads to the synthesis of complexes of the type [MX{Fc(EPh)PPh2}](M = Au, X = Cl, C6F5; M = Ag, X = OTf), (OTf = trifluoromethanesulfonate), [M{Fc(EPh)PPh2}2]X (M = Au, X = ClO4; M = Ag, X = OTf), [M(PPh3){Fc(EPh)PPh2}]OTf (M = Au, Ag), [Au2{Fc(SPh)PPh2}2](ClO4)2, [Au(C6F5)2{Fc(SePh)PPh2}]ClO4, [Au(C6F5)3{Fc(EPh)PPh2}], [Au2(C6F5)6{Fc(SePh)PPh2}] or [Cu{Fc(EPh)PPh2}2]PF6(E = S, Se). In these complexes coordination depends upon the metal centre; with gold it takes place predominantly to the phosphorus atom and with silver and copper to both phosphorus and chalcogen atoms. The treatment of some of the gold complexes with other metal centres affords heterometallic derivatives that in some cases are in equilibrium with the homometallic derivatives. Several compounds have been characterized by X-ray diffraction, four pairs of homologous compounds, yet not a single pair is isotypic. In many of them a three dimensional network is formed through secondary bonds such as hydrogen bonds, Au...Cl or Au...Se interactions. The complex [Ag(OTf){Fc(SePh)PPh2}] forms one-dimensional chains through trifluoromethanesulfonate bridging ligands.     

Metal clusters as ligands. Substitution of fe ions in Fe/Mo/S clusters by thiophilic CuI ions

The reactivity of Fe/S and Fe/Mo/S clusters, similar or analogous to those occurring in biological systems, with thiophilic metal ions has not been explored. In this Communication, we demonstrate that synthesis of heteropolynuclear clusters with different coordination geometries for different metals at different sites is possible by metal substitution or by metal addition reactions. The two clusters we report herein ([(Cl4-cat)2Mo2Cu5Fe4S9(PnPr3)7(SPnPr3)2]PF6 and [(Cl4-cat)2Mo2Cu6Fe4S10(PnPr3)8]) contain Fe, Mo, and Cu, which display pseudotetrahedral, pseudooctahedral, and pseudotrigonal geometries, respectively. The synthesis of these clusters is achieved by the addition of appropriate amounts of [Cu(CH3CN)4]+ to [(Cl4-cat)2Mo2Fe8(PnPr3)6]. The formation of the different products is temperature- and solvent-dependent. The Cu(I) units incorporated into the metal cluster framework, either bind to available lone pairs of the already bridging S ligands or displace the less thiophilic Fe atoms. Among the essential features of these new molecules are recognizable Fe/S fragments including an Fe6S9 core in the first cluster and the pentlandite Fe4Cu4S6 core in the second cluster.     

A family of alkynylgold(III) complexes [AuI(mu-{CH2}2PPh2)2Au(III)(C triple bond CR)2] (R = Ph, tBu, Me3Si): facile and reversible comproportionation of gold(I)/gold(III) to digold(II)

The symmetric digold(II)dichloride bis(ylide) complex [Au2Cl2(mu-{CH2}2PPh2)2] reacts with acetylides to form the asymmetric heterovalent gold(I)/gold(III) complexes [AuI(mu-{CH2}2PPh2)2AuIII(CCR)2] [R = Ph, tBu, and SiMe3], the phenyl analogue of which was characterized by X-ray crystallography. These compounds represent the first examples of gold(III) complexes containing two acetylide ligands. [AuI(mu-{CH2}2PPh2)2AuIII(CCPh)2] undergoes a reversible comproportionation reaction upon treatment with [Ag(ClO4)tht] to give the symmetric digold(II) cationic complex [Au2(tht)2(mu-{CH2}2PPh2)2](ClO4)2. If this complex is treated with phenylacetylene in the presence of base, the heterovalent gold(I)/gold(III) complex is re-formed. This reversible interconversion between binuclear gold(I)/gold(III) and digold(II) bis(ylide) complexes is unprecedented.     

Synthesis, structures and theoretical investigation of

The silylated derivative of thiophosphoric acid (S)P(SSiMe3)3 is used as a convenient starting compound for the synthesis of multinuclear Cu and Au cluster complexes. (S)P(SSiMe3)3 reacts with CuCI/PPh3 and [AuCClPPh3] to give the following compounds: [Cu4(P2S6)(PPh3)4] (1), [Cu6(P2S6)Cl2-(PPh3)6] (2) and [Au4(P2S6)(PPh3)4](3). According to X-ray structure determination, these compounds contain P2S6(4-) ions, in which S atoms act as ligands for Cu+ and Au+ ions. Although 1 and 3 have the same stoichiometry, bonding of the metal ions to the P2S6 skeleton displays small but remarkable differences. Au is twofold coordinated, whereas Cu shows a threefold coordination. Ab initio calculations have been carried out to rationalise these structural differences. The theoretical treatment of the corresponding Ag compound indicates the latter to be less stable.     

Highly luminescent gold(I)-silver(I) and gold(I)-copper(I) chalcogenide clusters

The reactions of [AuClL] with Ag(2)O, where L represents the heterofunctional ligands PPh(2)py and PPh(2)CH(2)CH(2)py, give the trigoldoxonium complexes [O(AuL)(3)]BF(4). Treatment of these compounds with thio- or selenourea affords the triply bridging sulfide or selenide derivatives [E(AuL)(3)]BF(4) (E=S, Se). These trinuclear species react with Ag(OTf) or [Cu(NCMe)(4)]PF(6) to give different results, depending on the phosphine and the metal. The reactions of [E(AuPPh(2)py)(3)]BF(4) with silver or copper salts give [E(AuPPh(2)py)(3)M](2+) (E=O, S, Se; M=Ag, Cu) clusters that are highly luminescent. The silver complexes consist of tetrahedral Au(3)Ag clusters further bonded to another unit through aurophilic interactions, whereas in the copper species two coordination isomers with different metallophilic interactions were found. The first is analogous to the silver complexes and in the second, two [S(AuPPh(2)py)(3)](+) units bridge two copper atoms through one pyridine group in each unit. The reactions of [E(AuPPh(2)CH(2)CH(2)py)(3)]BF(4) with silver and copper salts give complexes with [E(AuPPh(2)CH(2)CH(2)py)(3)M](2+) stoichiometry (E=O, S, Se; M=Ag, Cu) with the metal bonded to the three nitrogen atoms in the absence of AuM interactions. The luminescence of these clusters has been studied by varying the chalcogenide, the heterofunctional ligand, and the metal.     

Penta- and hexaruthenium carbonyl 'raft' complexes supported by monocarborane cage ligands

Reaction between [PPh4][closo-4-CB8H9] and [Ru3(CO)12] in refluxing toluene affords the unprecedented hexaruthenium metallacarborane salt [PPh4][2,3,7-{Ru(CO)3}-2,6,11-{Ru(CO)3}-7,11,12-{Ru(CO)3}-3,6,12-(micro-H)3-2,2,7,7,11,11-(CO)6-closo-2,7,11,1-Ru3CB8H6] (1a), which contains a planar Ru6 'raft' supported by a {CB8} monocarborane cluster. Addition of [CuCl(PPh3)]4 and Tl[PF6] to a CH2Cl2 solution of 1a results in simple cation replacement, forming the analogous [Cu(PPh3)3]+ salt (1b). The phenyl-substituted monocarborane [NEt4][6-Ph-nido-6-CB9H11] reacts with [Ru3(CO)12] in refluxing 1,2-dimethoxyethane to afford the pentaruthenium cluster species [N(PPh3)2][2,3,7-{Ru(CO)3}-3,4,8-{Ru(CO)3}-7,8-(micro-H)2-1-Ph-2,2,3,3,4,4-(CO)6-hypercloso-2,3,4,1-Ru3CB8H6] (2), after addition of [N(PPh3)2]Cl. Treatment of 2 with [CuCl(PPh3)]4 and Tl[PF6] in CH2Cl2 forms the zwitterionic complex [10,12-{exo-Cu(PPh3)2}-2,3,7-{Ru(CO)3}-3,4,8-{Ru(CO)3}-7,8,10,12-(micro-H)4-1-Ph-2,2,3,3,4,4-(CO)6-hypercloso-2,3,4,1-Ru3CB8H4] (3). Substitution of CO by PPh3 with concomitant cation replacement occurs on introduction of [AuCl(PPh3)], Tl[PF6], and PPh3 to a CH2Cl2 solution of 2, forming [Au(PPh3)2][2,3,7-{Ru(CO)2PPh3}-3,4,8-{Ru(CO)2PPh3}-7,8-(micro-H)2-1-Ph-2,2,3,3,4,4-(CO)6-hypercloso-2,3,4,1-Ru3CB8H6] (4). Crystallographic studies confirmed the cluster architectures in 1b, 2, and 3.     

Reaction network governing diphosphine-protected gold nanocluster formation from nascent cationic platforms

We identify the reaction network governing gold monolayer protected cluster (MPC) formation during the reduction of Au(PPh(3))Cl and L(5) (L(5) = 1,5-bis(diphenylphosphino)pentane) in solutions. UV-vis spectroscopy and electrospray ionization mass spectrometry (ESI-MS) monitored the formation of ligated Au(x): 6 ≤ x ≤ 12 clusters, which comprise the reaction intermediates and final products. Initially, predominantly [Au(2)L(5)(2)](2+) complexes form through dissolution of Au(PPh(3))Cl. These complexes control the reduction and nucleation reactions that form nascent phosphine-ligated Au(8) and Au(10) ionic clusters. [Au(10)L(5)(4)](2+) is an observed growth platform for ligated Au(11) and Au(12) clusters. The data for syntheses of Au : L(5) systems evidence that the nascent reaction products (t < 3 days) are less dependent on the chosen reducing agent (borane tert-butylamine complex or NaBH(4)); instead, after reduction ceases, subsequent solution phase processing provides greater control for tuning cluster nuclearity.     

Unprecedented formation of novel phosphonodithioate ligands from diferrocenyldithiadiphosphetane disulfide

The reaction of the phosphetane disulfide, FcP(S)S 2P(S)Fc ( 1) (Fc = (eta (5)-C 5H 5)Fe(eta (5)-C 5H 4)), the ferrocenyl analogue of the Lawesson reagent, with gold and palladium complexes leads to the unprecedented formation of phosphonodithioate ligands upon coordination to the metal centers. The reaction of 1 with gold complexes such as [AuCl(PR 3)] affords the species [Au{S 2P(OH)Fc}(PR 3)] (PR 3 = PPh 3 ( 2), PPh 2Me ( 3)), in which the phosphonodithioate ligand Fc(OH)PS 2 (-) has been formed. The same ligand is present in the compound [Au 2{S 2P(OH)Fc} 2].[N(PPh 3) 2]Cl ( 4), obtained by reaction of 1 with [N(PPh 3) 2][AuCl 2]. It crystallizes with one molecule of [N(PPh 3) 2]Cl, whereby complex 4 acts as an anion receptor and forms strong hydrogen bonds between the chloro and the hydroxyl groups. The reaction with palladium derivatives is different; two complexes, [Pd 2(S 4OP 2Fc 2) 2] ( 5) and [Pd 4Cl 4(S 4OP 2Fc 2) 2] ( 6), are obtained in molar ratio 2:1 and 1:1, respectively. In these complexes a new phosphonodithioate ligand is present and probably arises from the condensation of two molecules of Fc(OH)PS 2 (-). Complex 5 has also been characterized by X-ray methods.     

Aurophilicity in gold(I) thiosemicarbazone clusters

The reaction of the phosphine thiosemicarbazone ligands HLPH and HLPMe with Au(I) ions yields the gold complexes [Au(3)(HLPH)(2)Cl(2)]Cl·2MeOH (1·2MeOH) and [Au(2)(HLPMe)Cl(2)] (2). The structures determined by X Ray diffraction, [Au(3)(HLPH)(2)Cl(2)]Cl·4MeOH (1·4MeOH) and [Au(2)(HLPMe)Cl(2)](2) (2), are the first examples of gold(I) thiosemicarbazone clusters showing aurophilicity. The structure of the trinuclear cation 1 contains the Au(1) atom located in an inversion centre, being connected to another gold(I) atom, Au(2), through a phosphino thiosemicarbazone molecule which acts as a S,P-bridging ligand. Additionally, every gold(I) atom in the trinuclear cation 1 assembles into trinuclear linear cluster units by means of close gold-gold interactions, being connected through the crystal cell in a 2D zigzag mode. The crystal structure of [Au(2)(HLPMe)Cl(2)](2) (2) contains one discrete molecule [(AuCl)(2)(HLPMe)] in the asymmetric unit, which is further assembled into tetranuclear [(AuCl)(2)(HLPMe)](2) units by means of close gold-gold interactions. Both clusters are highly luminescent in solution.     

How cationic gold clusters respond to a single sulfur atom

Results describing the interaction of a single sulfur atom with cationic gold clusters (Au(n) (+), n=1-8) using density functional theory are described. Stability of these clusters is studied through their binding energies, second order differences in the total energies, fragmentation behavior, and atom attachment energies. The lowest energy structures for these clusters appear to be three dimensional right from n=3. In most cases the sulfur atom in the structure of Au(n)S(+) is observed to displace the gold atom siting at the peripheral site of the Au(n) (+) cluster. The dissociation channels of Au(n)S(+) clusters follow the same trend as Au(n) (+) cluster, based on the even/odd number of gold atoms in the cluster, with the exception of Au(3)S(+). This cluster dissociates into Au and Au(2)S(+), signifying the relative stability of Au(2)S(+) cluster regardless of having an odd number of valence electrons. Clusters with an even number of gold atoms dissociate into Au and Au(n-1)(S)(+) and clusters with an odd number of gold atoms dissociate into Au(2) and Au(n-2)(S)(+) clusters. An empirical relation is found between the conduction molecular orbital and the number of atoms in the Au(n)S(+) cluster.