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The reaction among [Au2Ag2(C6F5)4(OEt2)2]n, PbCl2 and terpyridine leads to the polymeric complex [{Au(C6F5)2}2{Pb(terpy)}]n (1). Its crystal structure reveals potential voids close to the lead centres large enough to hold different molecules. The availability of these free sites allows complex 1 to act as a VOC sensor. Thus, when 1 is exposed to different solvent vapours such as acetonitrile, toluene or THF, variations in its solid appearance and its photophysical properties are observed as a consequence of the formation of the new polymorphs [{Au(C6F5)2}2{Pb(terpy)(CH3CN)2}]n (2), [{Au(C6F5)2}2{Pb(terpy)}]n·Tol (3) and [{Au(C6F5)2}2{Pb(terpy)(THF)}]n·THF (4). Each polymorph displays a different emission energy depending on its structure and the presence of metallophilic interactions. In addition, the reversible solvent molecule exchange allows the tuning of the luminescence emissions in the greenish yellow–red range. DFT and TD-DFT calculations were performed to explain the origin of the luminescence of all these complexes. [ABSTRACT FROM AUTHOR]

The assembly of two different building blocks, [{Au(C6F5)2}{PbCl(terpy)}] (terpy=2,2′:6′:2′′‐terpyridine) and [{Au(C6F5)2}2{Pb(terpy)}]n, acting as terminal or central pieces, respectively, gives rise to a decanuclear complex built via metallophilic and π‐stacking interactions in which the number of AuI⋅⋅⋅AuI and AuI⋅⋅⋅PbII contacts is finely controlled. [ABSTRACT FROM AUTHOR]

The development of gold catalysis has allowed significant levels of activity and complexity in organic synthesis. Recently, the use of very active small gold subnanoclusters (Aun, n<10) has been reported. The stabilization of such nanocatalysts to prevent self-aggregation represents a true challenge that has been partially remediated, for instance, by their immobilization in polymer matrices. Here, we describe the transient stabilization of very small gold subnanoclusters (Aun, n < 5) by alkyl chains or aromatic groups appended to the reactive π bond of simple alkynes. The superior performance toward Brønsted acid-free hydration of medium to long aliphatic alkynes (1-hexyne and 1-docecyne) and benzylacetylene with respect to phenylacetylene is demonstrated experimentally and investigated computationally. A cooperative network of dispersive Au…C-H and/or Au…π interactions, supported by quantum mechanical calculations and time-resolved luminescence experiments, is proposed to be at the origin of this stabilization. [ABSTRACT FROM AUTHOR]

Two organometallic complexes, named [Hg(2-C6H4PPh2)2] (1) and [{Au(C6F5)}2{Hg(2-C6H4PPh2)2}] (2) have been studied as quenchers of the fluorescence of naphthalene. Positive deviations were observed in the Stern-Volmer (S-V) plots for both quenchers. The analyses of the data reveal the existence of transient components in the dynamic quenching. The diffusion coefficients of these complexes have been obtained by two different methods, through the Stokes-Einstein equation, and from ¹H PGSE NMR experiments. With these values, and taking into account the experimental KT constants, the radii of the transient quenching spheres were obtained, which show unusually large values. [ABSTRACT FROM AUTHOR]

A selected group of cationic three-coordinate Au(I)-NHC complexes of the form [Au(NHC)(dppbz)]OTf have been prepared from a commercially available bidentate phosphine. All complexes have been fully characterised by NMR and mass spectroscopy. The [Au(NHC)]+ fragment shows a pronounced tendency to form linear complexes which is confirmed by the molecular structure of [Au(IPr)(dppbz)]OTf in the solid state. The complexes are brightly luminescent and present very high quantum yield values in the solid state. The assignments of the electronic transitions involved in the emissions are of a phosphorescent nature and it is proposed that the origin of the emissions is derived from the ligand (dppbz) to metal-ligand (Au-NHC) charge-transfer (LML'CT) transition. [ABSTRACT FROM AUTHOR]

Tetrahedral Au¹ complexes [L3Au(SnCl3)l (L = PMe3 (1), PMe2Ph (2), PMePh2 (3), and PPh3 (4)) were prepared by treatment of the [(tht)Au(SnCl3)l (tht = tetrahydrothiophene) complex with three equivalents of the corresponding tertiary phosphine. The crystal structures of complexes 1-4 have been determined through X-ray diffraction studies showing, in all cases, [SnCl3]-fragments covalently bonded to the corresponding [Au(PR3)3]+ units, which leads to a tetrahedral coordination environment for gold. Complexes 3 and 4 show phosphorescence in the solid state at room temperature and 77 K that is largely redshifted relative to the free [Au(PR3)3]+ and [SnCl3]- counterparts. Correlated MP2, SCS-MP2, and ONIOM MP2/UFF calculations suggest a largely distorted lower triplet excited state (T,) for each model system. The AuP3+ moiety is distorted leading to a T-shape, whereas the SnCl3- unit is left almost unaltered. Molecular orbital and population analysis suggest that the emission of these tetrahedral Au1 complexes arises from a ³MC transition slightly perturbed by the SnCl3- fragment. [ABSTRACT FROM AUTHOR]

The polymeric Au/Tl compounds [{Au(C6X5)2}Tl]n (X = Cl, F) react with the crown thioethers 1,4,7-trithiacyclononane ([9]aneS3), 1,5,8,11-tetrathiacyclotetradecane ([14]aneS4), and 1,4,7,10,13,16,19,22-octathiacyclotetracosane ([24]aneS8) in an appropriate molar ratio to afford [{Au(C6X5)2}Tl(L)]2 [L = [9]aneS3, X = Cl (1), F (4); L = [14]aneS4, X = Cl (2), F (5)], [{Au(C6Cl5)2}2Tl2([24]aneS8)]n (3) or [{Au(C6F5)2}2Tl2([24]aneS8)] (6). X-ray diffraction studies of 3, 4 and 6 reveal polymeric (3) or tetranuclear (4, 6) structures formed via Tl–S bonds and Au…Tl or Au…Tl and Au…Au contacts. All the complexes are luminescent in the solid state, but not in solution, where the metal–metal interactions, which are responsible for the luminescence, are no longer present. DFT calculations on representative model systems of complexes 3, 4 and 6 have also been carried out in order to determine the origin of the electronic transitions responsible for their optical properties. [ABSTRACT FROM AUTHOR]

Heteronuclear complexes {[Hg(R)2][Au(R′)(PMe3)]2} n (R=R′=C6Cl2F3 ( 3); R=R′=C6F5 ( 4); R=C6Cl2F3, R′=C6F5 ( 5); R=C6F5, R′=C6Cl2F3 ( 6)) were prepared by the treatment of the corresponding organomercury compounds, [Hg(C6X5)2], with two equivalents of [Au(C6X5)(PMe3)]. Their crystal structures, as determined by using X-ray diffraction methods, display Au⋅⋅⋅Hg interactions. Although only compound 4 and 5 show luminescence in the solid state, all of these compounds quench the fluorescence of naphthalene in solution. Solution studies of these derivatives suggest a cooperative effect of the gold(I) center in switching on the quenching capabilities of the [Hg(C6X5)2] synthon with naphthalene. Theoretical studies confirmed the quenching ability of the organomercury species in the presence of gold. [ABSTRACT FROM AUTHOR]

By treatment of the polymeric species [AuTI(C6Cl5)2] n with ketones or with acetylacetone and 4,4′-bipyridine, the new tetranuclear complexes [Au2TI2(C6Cl5)4]·L (L = PhMeC=O, acacH) or [Au2TI2(C6Cl5)4 (bipy)]·(acacH) have been prepared. Their crystal structures have been determined by X-ray diffraction methods and they all present a central Au2TI2 core formed via one TI···TI and four Au···TI unsupported interactions resulting in a loosely bound butterfly cluster. These complexes are strongly luminescent in both the solid state and solution showing an optical behavior in agreement with the maintenance of the TI···TI contact even in solution. [ABSTRACT FROM AUTHOR]

The structures of the tetragold(I) formamidinate cluster complexes, [Au4(ArNC(H)NAr)4], Ar=C6H4-4-OMe (1), C6H3-3,5-C1 (2), C6H4-4-Me (3), have been characterized by x-ray crystallography. The range of Au···Au distances is 2.8-3.0 Å. The angles at Au···Au···Au are acute and obtuse 70 and 109% 88 and 91°, and 63 and 116° in 1, 2, and 3, respectively. The four gold atoms are located at the comer of a rhomboid with the formamidinate ligands bridged above and below the near plane of the four Au(I) atoms. The tetranuclear gold(I) complexes show a bright blue-green luminescence under UV light, with an emission at ∼490 nm and a weak emission at ∼530 nm in the solid state, at room temp and 77 K. The oxidation of the formamidinate cluster, 1, has been studied electrochemically in 0.1 M Bu4NPF6/CH2Cl2 at a Pt working electrode with different scan rates. Three waves were obtained, 0.75, 0.95, and 1.09 V vs. Ag/AgCl at a scan rate of 500 mV/s, the three waves are reversible. The potentials are independent of the scan rate in the range 50 mV/s to 3 V/s. The current at the third wave is larger than those at the first two. KEY WORDS: Gold; formamidinates; tetrameric; luminescence; electrochemistry. [ABSTRACT FROM AUTHOR]

The tetranuclear Au(I) pyrazolate complex, [(dppm)[sub 2]Au[sub 4](3,5-Ph[sub 2]Pz)[sub 2]](NO[sub 3])[sub 2] · H[sub 2]O, 1, has been synthesized and structurally characterized. It is the first tetranuclear pyrazolate of Au(I) to have been found, although the trinuclear pyrazolates of Au(I) are well known. Complex I exhibits luminescence at 77 K when excited at 333 nm with an emission maximum at 454 nm. The emission has been assigned to ligand to metal charge transfer, LMCT, based upon the vibronic structure that is observed. The complex crystallizes in the monoclinic space group P2[sub 1]/c, with a=19.33(3)Å, b=20.26(3)Å, c=19.80(3)Å, r= 106.74(2)°, V = 7425(17)ų, Z = 8, and R = 0.058. The Au...Au distances are Au(1)...Au(4) = 3.185(3) Å, Au(1)...Au(2) = 3.230(3) Å, Au(2)...Au(3) = 3.079(3) Å, and Au(3)... Au(4) = 3.280(3) Å. [ABSTRACT FROM AUTHOR]

Reaction of perhalophenylgold(I) complexes [AuR(tht)] (R = C 6 Cl 2 F 3 , C 6 Cl 5 ; tht = tetrahydrothiophene) with different number of equivalents of Xantphos (4,5-Bis(diphenylphosphino)-9,9-dimethylxanthene) leads to discrete complexes in which the metal atom displays very different coordination environments. Thus, the ionic complex [Au(Xantphos) 2 [Au(C 6 Cl 2 F 3) 2 (1) or the neutral [Au(C 6 Cl 5)(Xantphos)] (2) one are obtained when a 1:1 (Au:Xantphos) stoichiometry is used. However, similar compounds [Au 2 R 2 (μ-Xantphos)] (R = C 6 Cl 2 F 3 (3); C 6 Cl 5 (4)) are synthesized when the amount of gold is increased to a 2:1 ratio. The use of diphosphine Xantphos, which can act as bridging, chelate or even as mono-dentate ligand, together with the use of different perhalophenyl groups bonded to the gold(I) centres, allows the synthesis of cationic tetracoordinate gold(I) fragments (1), mononuclear (2) or dinuclear (3 – 4) dicoordinated gold(I) complexes. This structural diversity in the coordination arrangements as well as the different aryl groups present in the molecules directly affect their photophysical properties, giving rise to different luminescent emission energies ranging from 470 to 580 nm, and also to a different origin for the electronic transitions related to them such as 3IL (3) to 3MLCT (4) and also a mixture of them 3MLCT/3IL (1 and 2). The experimental photophysical results obtained for these gold(I) complexes were supported by DFT and TD-DFT calculations. On the other hand, the behaviour of these complexes in solution is different, losing their emissive properties for all complexes or displaying the co-existence of different structural arrangements in the case of complexes 1 and 2 , as observed through variable-temperature 31P{1H} NMR experiments. Image 1 • The use of Xantphos expands the coordination abilities of gold(I) centres. • Controlling the structural arrangements permits a tuning of the emissive properties. • TD-DFT shows 3IL and/or 3MLCT transitions as responsible for the luminescence. [ABSTRACT FROM AUTHOR]

The first three-coordinate gold(I) N-heterocyclic carbene (NHC) complexes have been prepared with the nido-carborane diphosphine. The complexes are brightly luminescent and present very high quantum yield values. The carbene ligand is able to modulate the energy of the emissions and, depending upon the substituent, the luminescence changes from blue to green. Theoretical calculations corroborate that the emissions are phosphorescence and arise from charge transfer (LML'CT) transitions from nido-carborane ligand (L) to metal/ligand group "gold(I)-NHC ligand" (ML'). [ABSTRACT FROM AUTHOR]

Abstract: The heteropolynuclear complexes [AuTl(C6X5)2] n (X=F, Cl) react with dimethylsulfoxide (DMSO) in different molar ratios leading to products of stoichiometry [Tl2{Au(C6F5)2}2{μ-DMSO}3] n (1), and [Tl2{Au(C6Cl5)2}2{μ-DMSO}2] n (2). These complexes have been structurally characterized and can be viewed as extended linear chains built with Tl–Au–Tl units in which the thallium atoms are bridged by the oxygen atoms of DMSO ligands. Additional [Au(C6X5)2]− fragments interact with one or two thallium centres, respectively, giving rise to two different types of metal–metal interactions in each molecule. Both of them show a strong luminescence in solid state and complex 2 also in solution. The thallium–thallium interaction in this complex is considered to be the responsible of its luminescence, which remains in solution. [Copyright &y& Elsevier]

[AuTl(C6F5)2(en)] (en = ethylenediamine) reacts with cyclic ketones as cyclopentanone (Cy5＝O), cyclohexanone (Cy6＝O) or cycloheptanone (Cy7＝O) in 1:1 or 1:2 molar ratio leading to products of stoichiometry [AuTl(C6F5)2{CyxN(CH2)2NH2}] (x = 5 1, 6 2 or 7 3), or [AuTl(C6F5)2{Cyx＝N(CH2)2N＝Cyx}] (x = 5 4, 6 5 or 7 6). Addition of ethylenediamine to the ketimine complexes in chloroform regenerates [AuTl(C6F5)2(en)], the starting material, and the free ketimines, as their NMR and mass spectra evidenced. The ketimine complexes display luminescence in solid state at room temperature and at 77 K at higher wavelengths than the diamine starting product (505 nm). The excited states responsible for this behaviour are assigned to orbitals due to the gold–thallium interactions. [Copyright &y& Elsevier]

Abstract: Gold(I) compounds have several potential roles in biologically related chemistry. The relatively low toxicity of gold and its lability allows human consumption of drugs formed with this element. Trinuclear and tetranuclear clusters look particularly interesting because of the strong basicity of the gold(I) centers in these molecules. Future studies are expected to lead to interesting new bio-related observations. The ability of gold(I) compounds to interact with themselves aurophilically and with other heavy element ions has produced spectroscopic properties which are sensitive to volatile organic compounds (VOCs) and other molecular interactions. Thus bio-applicability for sensing toxic components appears reasonable. [Copyright &y& Elsevier]