Au Tetranuclear Complex

Article pubs.acs.org/IC

Tuning the Luminescent Properties of a Ag/Au Tetranuclear Complex Featuring Metallophilic Interactions via Solvent-Dependent Structural Isomerization Rocío Donamaría,† M. Concepción Gimeno,‡ Vito Lippolis,*,§ José M. López-de-Luzuriaga,*,† Miguel Monge,† and M. Elena Olmos*,† †

Departamento de Química, Universidad de La Rioja. Centro de Investigación de Síntesis Química. Complejo Científico-Tecnológico, 26004 Logroño, Spain ‡ Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), CSIC-Universidad de Zaragoza, E-50009 Zaragoza, Spain § Dipartimento di Scienze Chimiche e Geologiche, Università degli Studi di Cagliari, S.S. 554 Bivio per Sestu, 09042 Monserrato (CA), Italy S Supporting Information *

ABSTRACT: In this paper the reaction products of the basic gold(I) species [Au(C6Cl5)2]− against the acid salt Ag(OClO3) in the presence of the S-donor macrocyclic ligand 1,4,7-trithiacyclononane ([9]aneS3) are studied in different solvents. Two different isomers of stoichiometry [{Au(C6Cl5)2}Ag([9]aneS3)]2 were isolated depending on the solvent used, dichloromethane or tetrahydrofuran, which show different luminescence in the solid state. X-ray diffraction studies of these compounds reveals that both show the same heteropolynuclear Ag···Au···Au···Ag system but with different Au···Au interaction distances and different relative positions of the cationic fragment [Ag([9]aneS3)]+ in the structure with respect the bimetallic Au···Au core. This work includes a study of the optical properties of both isomers, as well as time-dependent density functional theory calculations that were performed to determine the origin of their different luminescence.

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INTRODUCTION The chemistry of hetero-polynuclear extended supramolecular systems built by secondary interactions has attracted physicists’ and chemists’ interest in recent years. This is mainly due to the particular characteristics of the chemical bonding in these systems and to the physical and chemical properties associated with them.1 In particular, the luminescence observed in these compounds seems to be closely related to the presence of metal···metal interactions, which have in many cases been implicated in these optical properties.2 For the synthesis of such derivatives, our research group has followed an acid−base strategy, and many gold(I) complexes with heterometals as silver(I), thallium(I) or copper(I), among others, have been synthesized.3 In particular, luminescent derivatives of stoichiometry [AuAg(C6X5)2L] (X = halogen, L = neutral ligand) can be obtained in a typical reaction between © XXXX American Chemical Society

basic NBu4[Au(C6X5)2] precursors and acid silver(I) salts in the presence of L, which have been revealed as a versatile family of complexes with a variety of structures and optical properties associated with them. These depend on a number of factors such as the donor properties of the perhalophenyl groups bonded to gold(I), the nature of the neutral ligands bonded to silver(I), the aggregation state, or the number and disposition of molecular units that form the supramolecular species through covalent ligand−metal or noncovalent metal−metal interactions. Some of these luminescent materials present practical applications, and, thus, for example, the diethyl ether derivatives [Au2Ag2(C6X5)4(OEt2)2]n (C6X5 = C6F5, 3,5-C6Cl2F3, C6Cl5) Received: August 2, 2016

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DOI: 10.1021/acs.inorgchem.6b01819 Inorg. Chem. XXXX, XXX, XXX−XXX

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Inorganic Chemistry

summary, this work includes a study of the optical properties of both isomers, as well as time-dependent density functional theory (TD-DFT) calculations that were performed to elucidate the origin of the luminescence.

featuring a rhombohedral disposition of the interacting metal centers can be employed as volatile organic compound sensors,4 while the structural analogous [Au2Ag2(C6F5)4(NCMe)2]n catalyzes the functionalization of several alkanes by means of the insertion of CHCO2Et into C− H bonds.5 Besides, [Au2Ag2(C6X5)4L2]n [X = Cl, F; L = Me2CO, MeCN] undergo molecular aggregation in solution through aurophilic interactions, showing a good correlation between the excitation spectra in solution at different concentrations and the absorption spectra in the solid state.4,6 Moreover, a study of the luminescence of related gold−silver clusters always showing a rhombohedral disposition of the metal centers and containing 4-C6F4I or 2-C6F4I as aryl groups has demonstrated that, by changing the ability of the aromatic ligand to induce aurophilic interactions and halogen bonds, the emission color can be tuned from green to deep red, and that the degree of cluster association in the 2-C6F4I derivatives can be reversibly switched by mechanochemical and/or vapochemical stimuli in the solid state.7 In addition, the weak interactions within the tetranuclear unit [Au2Ag2(C6X5)4L2] have been theoretically analyzed, concluding that in this type of polymeric system there is a preference for Ag···Cipso contacts in the pentafluorophenyl derivatives, while in the pentachlorophenyl ones Ag···Cl interactions are preferred.8 However, this is not applicable when L is a crown-thioether ligand, as we showed in a previous work.9a On the other hand, it is well-known that crown thioethers form stable coordination compounds with a great variety of metal ions, such as d10 closed-shell metal centers, which display different coordination environments, nuclearity, and dimensionality.10 These include some Ag(I) derivatives in which the polydentate S-donor ligands act as chelate, like in [Ag([9]aneS3)2]+ ([9]aneS3 = 1,4,7-trithiacyclononane),11 as bridge, like in [Ag2([24]aneS8)(CF3SO3)2(MeCN)2]∞ ([24]aneS8 = 1,4,7,10,13,16,19,22-octathiacyclotetracosane)12 or in both ways, like in the trinuclear [Ag3([9]aneS3)3]3+.13 Using similar crown thioethers as ligands, we recently published a series of heteronuclear AuI/MI (M = Ag, Tl) complexes obtained by reaction of [{Au(C6X5)2}M]n (X= Cl, F; M = Ag, Tl) with the crown thioether ligands [9]aneS3, [14]aneS4 (1,4,8,11tetrathiacyclotetradecane) or [24]aneS8. These complexes are formed by means of M−S bonds and metallophilic interactions and display different nuclearity (di-, tetra-, or polynuclear) and coordination mode for the S-donor ligands (mono- or polydentate and chelating or bridging).9 Furthermore, we studied the influence of different factors, such as the nature of the halogens present in the aryl group bonded to gold or the number of donor atoms in the thioether, on the stoichiometry and structural arrangement, as well as on the optical properties of the resulting products.9 Taking these precedents into account, we decided to study other factors that may influence the stoichiometry, structure, and optical properties of these types of complexes, such as the molar ratio of the reactants or the solvent employed in the synthesis. Specifically, we studied the reaction of [{Au(C6Cl5)2}Ag]n with 1 equiv of [9]aneS3 in different solvents, considering that the same reaction in a 1:2 molar ratio and in tetrahydrofuran (THF) led to [{Au(C6X5)2}Ag([9]aneS3)2]2.9a This reaction led to two different isomers, Z- or E[{Au(C 6Cl 5 ) 2}Ag([9]aneS 3)] 2, both featuring only one [9]aneS3 unit bounded to each Ag(I) center that shows different luminescence depending on the solvent employed in the synthesis, dichloromethane or THF, respectively. In

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SYNTHESIS AND CHARACTERIZATION In this paper we study the reactivity of the heterometallic gold(I)/silver(I) complex [{Au(C6Cl5)2}Ag2]n with the Sdonor polydentate ligand 1,4,7-trithiacyclononane ([9]aneS3) in equimolecular amounts and in different solvents. Surprisingly, while this reaction in THF leads to a yellow solid with green luminescence, E-[{Au(C6Cl5)2}Ag([9]aneS3)]2 (1), when the synthesis is performed in dichloromethane the second isomer, Z-[{Au(C6Cl5)2}Ag([9]aneS3)]2 (2), is obtained as an intense yellow solid with yellow luminescence (see Scheme 1). Scheme 1

Both solids show very similar elemental analyses and identical spectroscopic data, all of them in accordance with the proposed stoichiometry. Both complexes are stable to air and moisture for long periods, but luckily they have different solubility, which allows to obtain both isomers separately and pure. While complex 1 is soluble in THF and acetone and partially soluble in dichloromethane, diethyl ether, and acetonitrile, complex 2 is only soluble in THF. Thus, their IR spectra show, among others, bands arising from the pentachlorophenyl group bonded to gold(I) at 834 and 614 cm−1. Both 1H NMR spectra, recorded in [D8]-THF, display a unique singlet at 2.77 ppm, due to equivalent hydrogen atoms of [9]aneS3, and appear shifted if compared with the resonance of the free ligand, which appears at 3.21 ppm in the same solvent. This result is in accordance with our previous observations on related Au/Ag compounds containing [9]aneS3, in which the macrocycle remains coordinated to silver center in solution.9a On the other hand, the conductivity measurements of complexes 1 and 2 suggest that the counterparts are dissociated in solution in [Au(C6Cl5)2]− anions and [Ag([9]aneS3)]+ cations, since they behave as 1:1 electrolytes in THF. This result is again in accordance with our previous studies on crown thioether Au/Tl and Au/Ag compounds, in which dissociation is observed in solution.13 Finally, the MALDI(−) and MALDI(+) mass spectra of these two compounds show as base peaks those corresponding to the anion [Au(C6Cl5)2]− (m/z = 695) and cation [Ag([9]aneS3)]+ (m/z = 269), respectively, both of them B


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Inorganic Chemistry showing experimental isotopic distributions in agreement with the theoretical ones.

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Z/E ISOMERIZATION In view of these results and the different properties of these two compounds, we wondered if the transformation of one isomer into the other would be possible and whether this transformation would be reversible or not. For this purpose, both isomers were subjected to different environmental changes as pressure or temperature to see any change in their properties. Thus, the solids were first subjected to manual grinding in an agatha mortar. Nevertheless, this perturbation did not produce any modification in their photophysical properties. Next, upon heating, neither E-isomer nor Z-isomer showed a thermal polymorphic transformation, and both decomposed. It is noteworthy that the Z-isomer (more thermodynamically stable) decomposed at higher temperature (ca. 120 °C) than the Eisomer (ca. 80 °C). In contrast, if a small amount of the Z-isomer (2) is dissolved in THF, a yellow solid with green luminescence, which corresponds to the E-isomer (1), appears after evaporation of the solvent (see Figure 1).

Figure 2. E/Z isomerization through solution of 1 in dichloromethane after 24 h of stirring.

formation of the highly polar Z-isomer is favored in more polar solvents such as dichloromethane or acetone. Nevertheless, the almost similar polarity values between dichloromethane and THF makes it difficult to univocally assign a mechanism. Finally, to definitively confirm that both isomerizations occur quantitatively, we performed X-ray powder diffraction (XPD) studies of the pure compounds and of the materials obtained upon their treatment with the solvents as commented above. Figure 3 shows the patterns corresponding to both pure

Figure 3. XPD studies of both complexes under solution in the different solvents. Figure 1. Z/E isomerization by dissolution of Z isomer in THF and further evaporation (center) and its comparison with (left) crystals of Z-isomer and (right) crystals of E-isomer (used as reference).

isomers, which are clearly different, as well as their comparison with the patterns of the products resulting from the solution of 2 in THF and from treatment of 1 with dichloromethane or acetone. In all the cases, the pattern observed after each experiment is in accordance with a complete transformation of one isomer into the other. These results also demonstrate the reversibility of the Z/E isomerization by simple isolation of one of the isomers in the solid state and treatment with a different solvent (Scheme 2).

On the other hand, and considering the higher solubility of the E-isomer (1), which is soluble in acetone and partially soluble in dichloromethane among others, we added these two solvents to a couple of samples of 1. Regardless of the solvent used, in both cases, after 24 h of stirring, a yellow solid with yellow luminescence, the Z-isomer (2), appeared in the mother liquid (See Figure 2). Taking these results and the conductivity values found into account (see Experimental), the isomerization process could take place through the dissociation into the cation and the anion in solution, and the formation of the isomeric form occurs on the process of solid precipitation by recombination of the two ions. In this regard, we performed single-point energy calculations including dichloromethane as solvent for both isomers. The results obtained show that the Zisomer is thermodynamically more stable than E-isomer, which could promote the exchange of one isomer into the other in solution (see Supporting Information). Another possibility could be related to the polarity of the solvents used, since the

Scheme 2

C


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Inorganic Chemistry

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CRYSTAL STRUCTURES The crystal structures of both isomers were unequivocally determined by X-ray diffraction studies from single crystals obtained by slow diffusion of n-hexane into solution of the complex in THF (1) or in dichloromethane (2). Details of the data collection and refinement are given in Table 1, and selected bond lengths and angles appear in Table 2.

arrangement of charges, opposite to Coulomb’s rule, which was also observed in the crystal structures of [Au(C6F5)2Ag([9]aneS3)2]2 and [Au(C6F5)2Ag([14]aneS4)]2, recently reported by us.9a As can be seen in Figures 4 and 5, the main difference

Table 1. Data Collection and Structure Refinement Details for Complexes 1 and 2 compound chemical formula crystal habit crystal size/mm crystal system space group a/Å b/Å c/Å β/deg U/Å3 Z Dc/g cm−3 M F(000) T/°C 2θmax/deg μ(Mo Kα)/mm−1 No. of reflections measured No. of unique reflections Rint Ra (I > 2σ(I)) wRb(F2, all refl) No. of parameters No. of restraints Sc max Δρ/eÅ−3

1 C36H24Ag2Au2Cl20S6 yellow prism 0.38 × 0.20 × 0.14 monoclinic C2c 23.4283(5) 8.78750(10) 28.3331(6) 111.604(2) 5423.34(19) 4 2.410 1967.58 3712 −173 51 7.353 16 088 5021 0.0199 0.0167 0.0401 298 0 1.120 1.537

2 C36H24Ag2Au2Cl20S6 yellow prism 0.40 × 0.22 × 0.17 monoclinic C2c 24.2987(8) 15.5340(4) 17.1549(5) 124.092(1) 5362.4(3) 4 2.437 1967.58 3721 −100 55 7.437 41 391 6146 0.0651 0.0276 0.0607 346 0 1.040 2.105

Figure 4. Molecular structure of E-[Au(C6Cl5)2Ag([9]aneS3)]2 (1) with the labeling scheme for the atom positions. Ellipsoids are drawn at the 30% level. Symmetry transformations used to generate equivalent atoms: No. 1 −x, y, −z + 1/2.

R(F)= ∑||Fo| − |Fc||/∑|Fo|. bwR(F2) = [S{w(Fo2 − Fc2)2}/ ∑{w(Fo2)2}]0.5; w−1 = σ2(Fo2) + (aP)2 + bP, where P = [Fo2 + 2Fc2]/3, and a and b are constants adjusted by the program. cS = [∑{w(Fo2 − Fc2)2}/(n − p)]0.5, where n is the number of data and p the number of parameters. a

Figure 5. Molecular structure of Z-[Au(C6Cl5)2Ag([9]aneS3)]2 (2) with the labeling scheme for the atom positions. Ellipsoids are drawn at the 30% level. Symmetry transformations used to generate equivalent atoms: No. 1 −x + 1, y, −z + 3/2.

Both of them consist of two [Au(C6Cl5)2]− anions and two [Ag([9]aneS3)]+ cations connected by means of intermetallic Au···Au and Au···Ag interactions, the latter reinforced by additional Ag···Cipso contacts, and they show a pseudolinear Ag−Au−Au−Ag structural disposition. This leads to a + − − +

Table 2. Selected Bond Lengths [Å] and Angles [deg] for Complex 1 and Complex 2 Au(1)−C(1) Au(1)−C(11)/(7) Au(1)−Ag(1) Au(1)−Au(1)#1a C(1)−Au(1)−C(11)/(7) Ag(1)−Au(1)−Au(1)#1a S(1)−Ag(1)−S(2)

complex 1

complex 2

2.052(3) 2.063(3) 2.7501(2) 3.4136 (1) 172.57(11) 136.388(6) 83.83(2)

2.054(4) 2.062(4) 2.6772(3) 3.0397(3) 174.26(14) 159.311(10) 85.03(3)

Ag(1)−C(11)/(7) Ag(1)−S(1) Ag(1)−S(2) Ag(1)−S(3) S(1)−Ag(1)−S(3) S(2)−Ag(1)−S(3) Ag(1)−Au(1)−Au(1)#1a−Ag(1)#1a

complex 1

complex 2

2.461(3) 2.5778(8) 2.6859(8) 2.5698(8) 86.21(2) 84.83(2) 97.38

2.677(4) 2.6049(11) 2.6040(11) 2.5797(11) 85.20(3) 86.29(3) 65.48

Symmetry transformations used to generate equivalent atoms: No. 1 = −x, y, −z + 1/2 (for complex 1) and No. 1 = −x + 1, y, −z + 3/2 (for complex 2). a

D


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Inorganic Chemistry

which range from 2.7003(4) to 2.792(2) Å,4a,6,15−17 it is noteworthy that the Au−Ag distance observed in 2 (2.677 Å) is the shortest one described until now in these types of compounds. Finally, the analysis of the aurophilic interactions reveals the greatest difference between both crystal structures, showing values of 3.4136(1) Å in 1 and of 3.0397(3) Å in complex 2. Although the former distance is longer than the double of the van der Waals radius of gold (1.66 Å),18 according to the theoretical calculations (see below), it corresponds to a real Au···Au interaction, as occurs in the related pentafluorophenyl complex [{Au(C6F5)2}Ag([9]aneS3)2]2, which displays a Au−Au distance of 3.3702(3) Å.9a Taking all the above into account, we can conclude that the main differences between both isomers is the strength of the aurophilic contact and the relative position of the cationic [Ag([9]aneS3)]+ units. In this regard, it is worth mentioning that the Ag(1)−Au(1)−Au(1)#1−Ag(1)#1 torsion angles are significantly different: while 1 shows a torsion angle of 97.38°, its value in compound 2 is of only 65.48°. These differences in the Au−Au distances and the relative position of the cationic fragments could be the reason for the different optical properties that these two isomers display.

between both isomers is the relative positions of the cationic fragments [Ag([9]aneS3)]+, which leads to an E conformation in 1 and to a Z conformation in 2 with respect to the Au−Au direction. In both cases, the gold(I) centers are linearly coordinated to two aryl groups, showing identical Au−C distances of 2.052(3) and 2.063(3) Å in 1 and of 2.054(4) and 2.063(4) Å in 2, typical values for these types of derivatives. The deviation from the linearity, of 7.49° and 5.74° for 1 and 2, respectively, is probably related to the presence of an interaction between the silver center and the Cipso atom of one of the pentachlorophenyl groups. On the other hand, each silver atom is bonded to the three sulfur centers of a terminal [9]aneS3 crown thioether ligand and maintains additional nonbonding Ag···Au and Ag···C ipso interactions. These last contacts increase the coordination number of silver(I) to five, showing a distorted trigonal bipyramidal environment, as observed in the related derivatives [Au(C6F5)2Ag([9]aneS3)2]2 and [Au(C6F5)2Ag([14]aneS4)]2 previously described by us.9a It is noteworthy that there is a difference between these compounds and complexes 1 and 2. In complexes [Au(C6F5)2Ag([9]aneS3)2]2 and [Au(C6F5)2Ag([12]aneS4)]2 the silver atoms show a distorted square-based pyramidal environment with four sulfur atoms bonded to the silver center and the gold(I) at the vertex, while the distorted trigonal bipyramidal environment in 1 and 2 is formed through three Ag−S bonds and Ag···Au and Ag···Cipso contacts. The formation of the Ag···Cipso contact could be favored by the absence of more donor-sulfur atoms. The Ag−S distances, which range from 2.5698(8) to 2.6859(8) Å in 1 and from 2.5797(11) to 2.6049(11) Å in 2, lie in the range of Ag−S distances described for complexes containing the same ligand (2.443(2)−2.8907(11) Å),9a,10c,11,14 and they are more symmetrical than those observed in the related pentafluorophenyl complex [Au(C6F5)2Ag([9]aneS3)2]2, where there are three short [2.4727(10)−2.5965(11) Å] and one long [2.8907(11) Å] Ag−S distances.9a As commented above, in polymeric systems of the type [Au2Ag2(C6X5)4L2]n, Ag···Cipso contacts are frequently observed in the pentafluorophenyl derivatives, while the pentachlorophenyl ones usually display Ag···Cl interactions. In contrast, it is worth noting that, in Au/Ag derivatives containing crown thiothers, Ag···Cipso interactions usually appear when C6Cl5 is employed as ligand at gold, while this type of interaction is absent in the pentafluorophenyl complexes, which evidence the important role of the aryl group in the [Au(C6X5)2]−···[Ag([9]aneS3)]+ interaction. As commented above, in our case, both isomers E and Z display both Ag···Au and Ag···Cipso interactions, as well as aurophilic contacts, but there are significant differences in their strengths in both compounds. Thus, while complex 1 displays a shorter Ag−Cipso distance (2.461(3) Å) than that observed in 2 (2.677(4) Å), the metallophilic contacts are longer in 1 (Au···Ag = 2.7501(2); Au−Au = 3.4136(8) Å) than in 2 (Au−Ag = 2.6772(3); Au− Au = 3.0397(3) Å). The Ag−Cipso distances found both in 1 and 2 lie within the range of Ag−Cipso distances described for other Au/Ag compounds with bis(aryl)aurate(I) units, which vary from 2.4396(6) to 2.687(6) Å.4,6,7b,15 In contrast, while the Au−Ag distance in complex 1 (2.7501(2) Å) displays a typical value for Au−Ag distances in related compounds of stoichiometry [Au2Ag2R4L2]n (R = perhalophenyl group, L = neutral ligand),

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PHOTOPHYSICAL PROPERTIES The UV−vis absorption spectra of both derivatives 1 and 2 in THF solutions display bands that are also present in the heterometallic precursor [{Au(C6Cl5)2}Ag]n and the gold complex NBu4[Au(C6Cl5)2]. Thus, the band at higher energy is likely to arise from transitions located between π orbitals in the perhalophenyl groups, while the bands in the low-energy region are assigned to charge transfer transitions between gold and the pentachlorophenyl π* orbitals. The bands due to the [9]aneS3 ligand are probably masked by the more intense ones due to pentachlorophenyl groups (see Figure 6).

Figure 6. Absorption spectra in THF solution of complexes 1 and 2 and the Au(I), Au(I)−Ag(I), and [9]aneS3 precursors.

Both complexes display a very intense luminescence in the solid state at room temperature and at 77 K. Thus, complex 1 shows a green luminescence, while complex 2 shows a yellow one. The fact that they are not luminescent in solution is likely to be due to the rupture of the metal−metal interactions promoted by the solvent. This fact is in agreement with the molar conductivity values found, which are typical of 1:1 electrolytes (see Experimental). As we have commented, both complexes, although with similar compositions, display different Au−Au distances and relative positions of the [Ag([9]aneS3)]+ E


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Inorganic Chemistry fragments in their structures, and these factors could be in the origin of their different emissions. Thus, both complexes show a single emission at room temperature and at 77 K. For complex 1 excitation at 366 nm leads to an emission at 518 nm at room temperature; for complex 2 the emission maxima appears at 546 nm by excitation at 368 nm. (See Figure 7) The large Stokes shifts and

Table 3. Photophysical Properties of Complexes 1 and 2

a

solid RTa em (ex)

solid 77 K em (ex)

τ RTa (μs)

Φ RTa

1

518 (366)

518 (352)

2.5

79

2

546 (368)

561 (365)

3.9

98

kr/knr (s−1) 3.16 × 105/ 8.40 × 104 2.51 × 105/ 5.13 × 103

RT indicates room temperature.

samples provokes bond length contractions and, therefore, a change of the relative energy of orbitals generated in the intermetallic interaction, reducing the band gap between the frontier orbitals.20 Taking into account the complexes reported previously by our research group,[13a] it is important to discuss how the presence of the Au···Au contacts affects the emission energies as compared to complexes in which the aurophilic interactions are not present. Thus, complexes [{Au(C6Cl5)2}Ag([14]aneS4)] and [{Au(C6Cl5)2}2Ag2([24]aneS8)], which do not display Au···Au interactions in their solid-state structures, show emission bands at higher energy (450 and 476 nm, respectively), while the isomers reported herein, in which the Au···Au interaction is present, show lower emission energy (518 and 546 nm, respectively). Accordingly, the presence of Au···Au interactions red-shifts the emission energies having a strong influence in the frontier molecular orbitals responsible for their emissive behavior (see DFT and TD-DFT Calculations section).

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DFT AND TD-DFT CALCULATIONS To explain the origin of the emissive properties of complexes 1 and 2 in the solid state we performed DFT and TD-DFT calculations on representative models of these complexes. The model systems used for the calculations were built from the Xray diffraction structures of both complexes displaying a [{Au(C6Cl5)2}2Ag([9]aneS3)]2 stoichiometry. In a first stage, we fully optimized the tetranuclear models 1-S0 and 2-S0, which correspond to the ground-state structures for complexes 1 and 2, respectively. In addition, and taking into account the possible phosphorescent nature of the emissive properties of these complexes, we also fully optimized model systems 1-T1 and 2T1, which correspond to the lowest triplet excited-state structures for 1 and 2, respectively. The aim of these calculations is to gain insight into the nature of the structural distortions found for each complex when the S0→T1 transition occurs. Depending on the part of the molecule affected and the degree of distortion observed, an initial idea of the origin of the emissive properties can be proposed. The optimized structure for model 1-S0 is very similar to the structure found experimentally for complex 1 through X-ray diffraction studies. Thus, the computed intermetallic Au−Au#1 and Au−Ag distances are slightly shorter but comparable with the experimental ones. The calculated Ag−S distances also agree with the experimental ones, although in this case they are slightly longer. The rest of computed distances, angles, and dihedral angles also agree with the X-ray structure for complex 1. However, the 1-T1 optimized triplet excited-state structure shows an important shortening of the intermetallic Au−Au distance. Thus, in this T1 excited state the gold(I) centers approach each other from 3.289 Å in 1-S0 to 2.747 Å in 1-T1 (ca. 16% of length contraction). In addition, the optimized triplet excited structure displays a slight distortion around the

Figure 7. Luminescence in solid state at room temperature (top) and at N2 (liquid) temperature (bottom).

the lifetime measurements in the microsecond regime (2.5 μs for complex 1 and 3.9 μs for complex 2) suggest a significant difference between ground and excited states and that the emissions arise probably from spin-forbidden transitions. Nevertheless, the expected strong spin−orbit coupling due to the presence of gold in the complexes does not allow us to make a definitive assignment. Very interestingly, quantum yield measurements of both complexes in solid state at room temperature exhibit extremely high quantum yields with values of 79% in the case of complex 1 and 98% for complex 2. From these values together with the lifetimes, we can obtain the radiative constants whose values are also very high (1 or 2 orders of magnitude higher than the corresponding nonradiative constants, respectively; see Table 3). Finally, at liquid N2 temperature complex 1 displays an emission band at the same position, while in the case of complex 2 the emission band shifts to lower energies. The reason for the first is nowadays not well-understood, although it has been related to a rigidity of the structure (rigidochromism).19 In the case of the second it is a behavior common in complexes whose emissions arise from orbitals originated by intermetallic interactions. Thus, the cooling of the F


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Inorganic Chemistry

Table 4. Selected Experimental Structural Parameters for Complexes 1 and 2 and Optimized Parameters for Model Systems 1S0, 1-T1, 2-S0, and 2-T1

Au−Au#1 Au−Ag Ag−S1 Ag−S2 Ag−S3 Ag−C11 C11−Au−Ag C1−Au−Ag C11−Au−C1 Ag−Au−Au#1 Ag−Au−Au#1−Ag#1

X-ray Structure of 1

1-S0−Ground State S0

1-T1−Excited State T1

X-ray Structure of 2

2-S0−Ground State S0

2-T1−Excited State T1

3.4136(1) 2.7501(2) 2.5778(8) 2.6859(8) 2.5698(8) 2.461(3) 59.46(7) 120.85(7) 172.57(11) 136.388(6) −97.38

3.289 2.714/2.694 2.668/2.664 2.635/2.634 2.687/2.687 2.061/2.067 59.43/63.30 116.43/107.99 174.69/171.29 135.55/156.05 −115.46

2.747 2.715/2.718 2.639/2.648 2.700/2.706 2.667/2.662 2.056/2.056 58.46/58.37 108.95/109.15 167.37/167.49 156.50/156.51 −122.56

3.0397(3) 2.6772(3) 2.6049(11) 2.6040(11) 2.5797(11) 2.677(4) 67.34(10) 107.18(10) 174.26(14) 159.311(10) 65.48

3.061 2.674 2.621 2.637 2.658 2.624 65.64 107.66 173.17 151.13 114.86

2.741 2.713 2.643 2.655/2.701 2.701/2.655 2.395 58.10 109.58 167.27 154.72 64.77

larger increase in the Au−Ag distance than in complex 1, from 2.674 Å in S0 to 2.713 Å in T1; meanwhile, the C−Au−C angles appear distorted from the linearity from 173.17° to 167.27° (see Table 4 and Figure 8). From the analysis of the distorted structures 1-T1 and 2-T1 we can anticipate that the origin of the phosphorescent properties of complexes 1 and 2 could be related to metalcentered transitions involving, mainly, the interacting Au(I) centers and, to a lesser extent, the Ag(I) centers (vide infra). To verify the above-mentioned hypothesis, we computed the electronic structure for models 1-S0 and 2-S0 and the corresponding population analysis of the frontier molecular orbitals (MOs). In the case of model 1-S0 the highest occupied molecular orbital (HOMO) is located between the metal centers Au−Ag (60%) and in the aryl ligand (31%), and the HOMO−2 is mainly located at the [Au(C6Cl5)2]− anionic fragment (97%). Both occupied MOs show an antibonding character between the Au···Au interacting metals. This can be deduced by the analysis of the positive (red) and negative (green) phases of these MOs (see Figure S1 in Supporting Information).22 The lowest unoccupied molecular orbital (LUMO) is located at the [Au(C6Cl5)2]− units (100%) and displays a bonding character between the interacting gold centers. In the case of model 2-S0 the HOMO is mainly located at the metal centers Au−Ag (57%) and in the aryl ligand (36%), while HOMO−2 is located at the [Au(C6Cl5)2]− fragment (89%). Again, these orbitals display an antibonding character between gold centers. The LUMO orbital is also located at the [Au(C6Cl5)2]− fragment (90%) with a small contribution of the silver center (10%) and shows the same bonding character for the metals than the LUMO of model 1S0. If one looks at the energy of the frontier MOs of both isomers, we observe a clear LUMO stabilization and a HOMO destabilization as the gold centers approach each other in model 2-S0, as expected from the more efficient overlap of the empty 6s/6p or the filled 5dz2 atomic orbitals of closer gold centers that leads to the corresponding more stable σ-bonding orbital and less-stable σ-antibonding orbital, respectively. Therefore, the HOMO−LUMO gap is larger for model 1-S0 than for model 2-S0. In addition, the shape of the frontier MOs for the lowest triplet exited states for both complexes shows that for both cases of models 1-T1 and 2-T1, the highest singly occupied molecular orbital (SOMO) is of the same composition and nature as the LUMO orbitals in models 1-S0 and 2-S0, respectively. The same applies for SOMO-1 and HOMO

gold(I) coordination environment, which in a loss of linearity of the C−Au−C angles deviates from the linearity from 174.69°/171.29° in 1-S 0 to 167.37°/167.49° in 1-T1 , respectively. This trend has been previously described by some of us in the study of the lowest triplet excited-state distortion for model {[Tl(η6-benzene)][Au(C6Cl5)2]}.21 In addition, and as it was observed for the previously reported Au−Tl complex, one of the Au−Ag distances slightly increases from 2.694 to 2.718 Å (see Table 4 and Figure 8).

Figure 8. (top) Optimized model 1-S0 for complex 1 in the ground state S0 (left) and model 1-T1 in the triplet excited state T1 (right). (bottom) Optimized model 2-S0 for complex 2 in the ground state S0 (left) and model 2-T1 in the triplet excited state T1 (right).

In the case of complex 2, again the optimized model system in the ground state, 2-S0, is representative for the solid-state structure described for 2. In this case, both the calculated intermetallic Au−Au#1, Au−Ag, and Ag−S distances are very close to the experimental ones. In addition, the rest of computed distances, angles, and dihedral angles agree well with the X-ray structure of 2. In the case of optimized model 2-T1 we observe a decrease in the Au···Au distance from 3.061 Å in the ground state to 2.741 Å in the lowest triplet excited state (ca. 10% of length contraction) and a distortion in the gold center environment. The triplet excited state shows a slightly G


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Inorganic Chemistry

Figure 9. (left) MO diagram for the ground-state S0 (left) and the lowest triplet excited-state T1 (right) of complex 1. (right) MO diagram for the ground-state S0 (left) and the lowest triplet excited-state T1 (right) of complex 2.

Figure 10. Experimental UV−vis spectra in solid state; TD-DFT first singlet−singlet (red) excitation calculations for model system 1-S0 (left) and 2S0 (right); TD-DFT lowest singlet−triplet (blue) excitation for model system 1-S0 (left) and 2-S0 (right). The blue bars only represent the energy of the lowest singlet−triplet transitions, since the oscillator strength cannot be estimated.

orbitals when models 1-T1 and 2-T1 are compared with the corresponding 1-S0 and 2-S0, models, respectively. Therefore, in view of these results, we can state in both cases that the emission observed for complexes 1 and 2 (SOMO→SOMO-1 transition) can be assigned to a metal-centered transition mostly located at the interacting Au(I) centers, with a minor contribution of charge transfer transitions from the Ag moieties to the aurate units. The MOs diagrams for complexes 1 and 2 in the ground and lowest triplet excited state are depicted in Figure 9. To verify the possibility of electronic transitions involving the interacting metals the first 10 singlet−singlet excitation energies were calculated at the TD-DFT level of theory for models of complexes 1 and 2 as described in the Computational Details section. We performed an analysis of the energy and strength of the most intense vertical electronic excitations, and we compared them with the UV−vis solid-state spectra of the complexes. Moreover, since the emissive behavior of these complexes could arise from phosphorescent processes, we also computed the lowest singlet−triplet excitation at the TD-DFT level. The results including the most important excitations are shown in Table 6 and Figure 10. The first interesting observation is that the most intense singlet−singlet and the lowest singlet−triplet excitations are of the same nature for both models, but they appear at different

wavelengths depending on the studied model system. Thus, the S0→S1 transition is the most intense singlet−singlet excitation for both models 1-S0 and 2-S0 and consists of an HOMO→ LUMO transition. This transition appears at 377 nm for model 1-S0 and at 406 nm for model 2-S0. In both cases, these transitions consist of an admixture of a metal-centered transition on the interacting Au(I)···Au(I) centers with a contribution of a charge transfer from the [Ag([9]aneS3)]+ fragments to the interacting [Au(C6Cl5)2]− ones (see Tables 5 and 6). Moreover, the next intense singlet−singlet excitation for both models (S0→S3) consists of a HOMO−2→LUMO transition. In the case of model 1-S0 this transition appears at 320 nm; meanwhile, in the case of 2-S0 it is observed at 346 nm and takes place between the interacting [Au(C6Cl5)2]−··· [Au(C6Cl5)2]− fragments. In addition, the lowest singlet− triplet transition consists of an HOMO→LUMO transition and appears at 458 nm from model 1-S0 and at 492 from model 2S0. In view of these results, we can propose that the origin of the luminescence in both cases could be assigned to transitions involving the metals that are keeping intermetallic interactions. These results agree with the experimental UV−vis spectrum in solid state for each complex that displays a maximum at 281 and 290 nm and a shoulder at 390 and 400 nm for complexes 1 and 2, respectively. The shoulder at low energy found experimentally would be related to the forbidden lowest H


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Inorganic Chemistry

T1 emits at 548 nm and model 2-T1 at 577 nm. On the one hand, both values are slightly lower in energy than the values obtained experimentally, 518 nm for complex 1 and 546 for complex 2. On the other hand, if we compare the difference between the emissions obtained experimentally (546−518 = 28 nm) with the computed ones (577−548 = 29 nm), we show that they are almost equal, so we can establish that the results obtained theoretically are a good representation of the emissive properties observed experimentally. Figure 11 depicts a summary of all the computed data obtained at unrestricted DFT level (emissions) and at TD-DFT level (excitations) for both models.

Table 5. Population Analysis for Model Systems 1-S0 and 2S0a Contribution from Each Part of the Molecule to the Frontier Orbitals (%) model

orbitala

Au

Ag

[9]aneS3

C6Cl5

1-S0

LUMO+1 LUMO HOMO HOMO−2 HOMO−3 HOMO−4 HOMO−5 HOMO−7 HOMO−8 LUMO HOMO HOMO−1 HOMO−2 HOMO−3 HOMO−4 HOMO−6 HOMO−8

26 42 41 11 1 7 23 7 17 50 38 10 8 0 0 2 14

22 0 19 1 1 1 13 4 13 10 19 1 6 0 1 6 9

5 0 9 1 1 1 13 5 8 0 7 1 4 0 1 6 12

47 58 31 86 97 95 50 83 63 40 36 88 81 99 98 85 65

2-S0

Table 6. TD-DFT First Singlet−Singlet Excitation Calculations and Lowest Singlet-Triplet Excitations for Model Systems 1-S0 and 1-T1 model

exca

λcalc (nm)

f(s)b

contributionsc

1-S0

S0→S1 S0→S3 S0→S4

377 320 312

0.2772 0.0922 0.0463

HOMO→LUMO (100) HOMO(−2)→LUMO (91) HOMO(−3)→LUMO (22) HOMO(−4)→LUMO (31) HOMO(−5)→LUMO (21) HOMO(−3)→LUMO (60) HOMO(−4)→LUMO (35) HOMO→LUMO(+1) (13) HOMO(−5)→LUMO (14) HOMO(−7)→LUMO (51) HOMO(−8)→LUMO (75) HOMO→LUMO (53) HOMO→LUMO (98) HOMO(−1)→LUMO (97) HOMO(−2)→LUMO (97) HOMO(−3)→LUMO (98) HOMO(−4)→LUMO (96) HOMO(−6)→LUMO (86) HOMO(−8)→LUMO (86) HOMO→LUMO (100)

2-S0

S0→S5

307

0.0123

S0→S9

300

0.0199

S0→S10 S0→T1 S0→S1 S0→S2 S0→S3 S0→S4 S0→S5 S0→S8 S0→S9 S0→T1

293 458 406 361 346 338 329 312 309

0.0449 0.3298 0.0204 0.1730 0.0108 0.0173 0.0130 0.0125

Figure 11. Energy diagram of the computed results (DFT and TDDFT) for models of complex 1 (black) and complex 2 (red).

In summary, we have shown that the slight conformational difference in the solid-state structure of the isomers obtained for complexes 1 and 2 leads to subtle changes in the corresponding electronic structures, leading to the tuning of the emissive properties. The different emissive behavior observed experimentally can be supported be the use of DFT and TD-DFT computational tools, showing that the presence of the intermetallic interactions is a necessary condition for having luminescent properties and that the changes in these intermetallic distances, due to the different isomer configurations, lead to a higher or lower structural distortion of the lowest triplet excited state and, therefore, to lower-energy (yellow) or higher-energy (green) emissions.

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a

Only excitations with larger oscillator strength are included among the first 10 singlet excitation calculations. bOscillator strength ( f) shows the mixed representation of both velocity and length representations. cValue is 2[coeff]2 × 100.

EXPERIMENTAL SECTION

General. Thioether crown ligands23 and [{Au(C6Cl5)2}Ag]n16b were prepared according to the literature. Instrumentation. Fourier transform infrared (FT-IR) spectra were recorded in the 4000−200 cm−1 range on a Nicolet Nexus FT-IR using mineral oil mulls between polyethylene sheets. C, H, and S analyses were performed with PerkinElmer 240C microanalyzer. Molar conductivities were measured in ca. 5 × 10−4 M THF solutions with a Jenway 4510 conductimeter. Mass spectra were recorded with a Bruker Microflex MALDI-TOF using dithranol or 11-dicyano-4-tert-butylphenyl-3-methylbutadiene as matrix. 1H spectra were recorded with a Bruker Avance 400 in [D8]THF. Chemical shifts are quoted relative to SiMe4 (1H, external). Excitation and emission spectra in the solid state were recorded with a Jobin-Yvon Horiba Fluorolog 3−22 Tau-3 spectro-fluorimeter. Lifetime measurements were recorded with a Datastation HUB-B with a nanoLED controller and DAS6 software. The nanoLED employed

singlet−triplet transition described computationally for each model system, which is slightly red-shifted if compared to the experimental one (Figure 10). Finally, we computed through DFT calculations the energy of the emissions shown by both complexes. Thus, we calculated first the single-point energy corresponding to each model 1-T1 and 2-T1 in the triplet excited state, and we also computed the energy of these optimized models but in the ground state, that is, the energy of the ground state with the structure of the triplet excited state. In this way, we can estimate the emission energy for each model system. Thus, we obtained that model 1I


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Inorganic Chemistry *E-mail: [email protected]. (M.E.O.)

for lifetime measurements was one of 370 nm with pulse lengths of 0.8−1.4 ns. The lifetime data were fitted with the Jobin-Yvon software package. Measurements at 77 K were done with an Oxford Cryostat Optistat DN with an accessory for solid samples. Synthesis. E-[{Au(C6Cl5)2}Ag([9]aneS3)]2 (1). To a well-stirred solution of [{Au(C6Cl5)2}Ag]n (100 mg, 0.124 mmol) in THF [9]aneS3 (22 mg, 0.124 mmol) was added. The mixture was stirred at room temperature for 3 h; then the solvent was partially removed under reduced pressure, and finally, the addition of n-hexane led to the precipitation of product 1 as a yellow solid that was filtered and washed with n-hexane (108.4 mg, 89% yield). Elemental analysis (%) calcd for C36H24Ag2Au2Cl20S6 (1967.69): C 21.97, H 1.23, S 9.78. Found: C 21.94, H 1.22, S 10.05. ΛM = 67 Ω−1 cm2 mol−1. 1H NMR (400 MHz, [D8]THF, ppm): δ 2.77 ppm (s, 12 H, CH2). MALDITOF(−) m/z (%): 695 [Au(C6Cl5)2]− (100). MALDI-TOF(+) m/z (%): 269 [Ag([9]aneS3)]+ (100). FTIR (mineral oil): ν([Au(C6Cl5)2]−) at 834 and 614 cm−1. Z-[{Au(C6Cl5)2}Ag([9]aneS3)]2 (2). [9]aneS3 (22 mg, 0.124 mmol) was added to a suspension of [{Au(C6Cl5)2}Ag]n (100 mg, 0.124 mmol) in dichloromethane. After 3 h of stirring, a yellow solid appeared. Finally, the solvent was partially removed under reduced pressure, and then the yellow solid was filtered and washed with dichloromethane (86 mg, 71% yield). Elemental analysis (%) calcd for C36H24Ag2Au2Cl20S6 (1967.69): C 21.97, H 1.23, S 9.78. Found: C 22.26, H 1.22, S 10.24. ΛM = 64 Ω−1 cm2 mol−1. 1H NMR (400 MHz, [D8] THF, ppm): δ 2.77 ppm (s, 12 H, CH2). MALDI-TOF(−) m/z (%): 695 [Au(C6Cl5)2]− (100). MALDI-TOF(+) m/z (%): 269 [Ag([9]aneS3)]+ (100). FT-IR (mineral oil): ν([Au(C6Cl5)2]−) at 834 and 614 cm−1. Crystallography. Crystals were mounted in inert oil on glass fibers and transferred to the cold gas stream of a Nonius Kappa CCD diffractometer equipped with an Oxford Instruments low-temperature attachment. Data were collected using monochromated Mo Kα radiation (λ = 0.710 73 Å). Scan type ω and ϕ. Absorption effects were treated by semiempirical corrections based on multiple scans. The structures were solved by direct methods and refined on F2 using the program SHELXL-97.24 All non-hydrogen atoms were refined anisotropically, and hydrogen atoms were included using riding model. Computational Details. All calculations were performed using the Gaussian 09 package.25 DFT and TD-DFT calculations were performed using the PBE functional.26 The following basis set combinations were employed for the metals Au and Ag: the 19-VE pseudopotentials from Stuttgart and the corresponding basis sets augmented with two f polarization functions were used.27 The heteroatoms were treated by Stuttgart pseudopotentials,28 including only the valence electrons for each atom. For these atoms double-ζ basis sets of ref 28 were used, augmented by d-type polarization functions.29 For the H atom, a double-ζ, plus a p-type polarization function was used.30 All the calculations were performed on model systems built from their corresponding X-ray structures.

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Notes

The authors declare no competing financial interest. CCDC Nos. 1495339−1495340 contains the supplementary crystallographic data for this paper. These data can be obtained free of charge via www.ccdc.cam.ac.uk/conts/retriieving.html (or for the Cambridge Crystallographic Data Centre, 12 Union Road, Cambridge CB2 1EZ, UK; fax: (+44) 1223−336−033; or e-mail: [email protected]).

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ACKNOWLEDGMENTS D.G.I. MINECO/FEDER (Project Nos. CTQ2016-75816-C22-P and CTQ2016-75816-C2-1-P) is acknowledged for financial support. V.L. thanks Fondazione Banco di Sardegna for financial support. R.D. also acknowledges CAR for an FPI grant. We gratefully thank CESGA for computer support.

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(1) See, for example, Hoffmann, R. How Chemistry and Physics Meet in the Solid State. Angew. Chem., Int. Ed. Engl. 1987, 26, 846− 878. (2) See, for example, Fernández, E. J.; Garau, A.; Laguna, A.; Lasanta, T.; Lippolis, V.; López-de-Luzuriaga, J. M.; Montiel, M.; Olmos, M. E. Long-Chain Ketimine Synthesis in a Gold-Thallium Polymer. Organometallics 2010, 29, 2951−2959. (3) See, for example, (a) Fernández, E. J.; López-de-Luzuriaga, J. M.; Monge, M.; Rodríguez, M.; Crespo, O.; Gimeno, M. C.; Laguna, A.; Jones, P. G. Heteropolynuclear Complexes with the Ligand Ph2PCH2SPh: Theoretical Evidence for Metallophilic Au−M Attractions. Chem. - Eur. J. 2000, 6, 636−644. (b) Fernández, E. J.; López-de-Luzuriaga, J. M.; Monge, M.; Olmos, M. E.; Pérez, J.; Laguna, A. [Au2Tl2(C6Cl5)4]·(CH3)2CO: A Luminescent Loosely Bound Butterfly Cluster with a Tl(I)−Tl(I) Interaction. J. Am. Chem. Soc. 2002, 124, 5942−5943. (c) Fernández, E. J.; Laguna, A.; Lasanta, T.; López-de-Luzuriaga, J. M.; Montiel, M.; Olmos, M. E. 1,2Dibromo- and 1,2-Diiodotetrafluorobenzene as Precursors of Anionic Homo- and Heterometallic Gold Complexes. Organometallics 2008, 27, 2971−2979. (d) Fernández, E. J.; Laguna, A.; López-de-Luzuriaga, J. M.; Monge, M.; Montiel, M.; Olmos, M. E.; Rodríguez-Castillo, M. Unsupported Au(I)···Cu(I) interactions: influence of nitrile ligands and aurophilicity on the structure and luminescence. Dalton Trans. 2009, 7509−7518. (4) (a) Fernández, E. J.; López-de-Luzuriaga, J. M.; Monge, M.; Olmos, M. E.; Puelles, R. C.; Laguna, A.; Mohamed, A. A.; Fackler, J. P., Jr. Vapochromic Behavior of {Ag2(Et2O)2[Au(C6F5)2]2}n with Volatile Organic Compounds. Inorg. Chem. 2008, 47, 8069−8076. (b) Fernández, E. J.; Laguna, A.; López-de-Luzuriaga, J. M.; Olmos, M. E.; Puelles, R. C. Vapochromism in Complexes of Stoichiometry [Au2Ag2R4L2]n. Z. Naturforsch. 2009, 64b, 1500−1512. (5) Fuentes, M. A.; Rodríguez-Castillo, M.; Monge, M.; Olmos, M. E.; López-de-Luzuriaga, J. M.; Caballero, A.; Pérez, P. J. Intermetallic coinage metal-catalyzed functionalization of alkanes with ethyl diazoacetate: Gold as a ligand. Inorg. Chim. Acta 2011, 369, 146−149. (6) (a) Fernández, E. J.; Gimeno, M. C.; Laguna, A.; López-deLuzuriaga, J. M.; Monge, M.; Pyykkö, P.; Sundholm, D. Luminescent Characterization of Solution Oligomerization Process Mediated Gold−Gold Interactions. DFT Calculations on [Au2Ag2R4L2]n Moieties. J. Am. Chem. Soc. 2000, 122, 7287−7293. (b) Fernández, E. J.; Laguna, A.; López-de-Luzuriaga, J. M.; Monge, M.; Montiel, M.; Olmos, M. E.; Rodríguez-Castillo, M. Photophysical and Theoretical Studies on Luminescent Tetranuclear Coinage Metal Building Blocks. Organometallics 2006, 25, 3639−3646. (7) (a) Laguna, A.; Lasanta, T.; López-de-Luzuriaga, J. M.; Olmos, M. E.; Monge, M.; Naumov, P. Combining Aurophilic Interactions and Halogen Bonding To Control the Luminescence from Bimetallic Gold−Silver Clusters. J. Am. Chem. Soc. 2010, 132, 456−457. (b) Lasanta, T.; Olmos, M. E.; Laguna, A.; López-de-Luzuriaga, J.

ASSOCIATED CONTENT

S Supporting Information *

The Supporting Information is available free of charge on the ACS Publications website at DOI: 10.1021/acs.inorgchem.6b01819. Illustrated HOMO and LUMO for model systems, single-point energy calculations for model systems, coordinates of optimized structures for complexes 1 and 2 (PDF) X-ray crystallographic data for complex 1 (CIF) X-ray crystallographic data for complex 2 (CIF)

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REFERENCES

AUTHOR INFORMATION

Corresponding Authors

*E-mail: [email protected]. (V.L.) *E-mail: [email protected]. (J.M.L.) J


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Inorganic Chemistry

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M.; Naumov, P. Making the Golden Connection: Reversible Mechanochemical and Vapochemical Switching of Luminescence from Bimetalli-GoldSilver Clusters Associated through Aurophilic Interactions. J. Am. Chem. Soc. 2011, 133, 16358−16361. (8) López-de-Luzuriaga, J. M.; Monge, M.; Olmos, M. E.; RodríguezCastillo, M.; Laguna, A.; Mendizabal, F. Basicity of bisperhalophenyl aurates toward closed-shell metal ions: metallophilicity and additional interactions. Theor. Chem. Acc. 2011, 129, 593. (9) (a) Blake, A. J.; Donamaría, R.; Lippolis, V.; López-de-Luzuriaga, J. M.; Manso, E.; Monge, M.; Olmos, M. E. Influence of Crown Thioether Ligands in the Structures and of Perhalophenyl Groups in the Optical Properties of Complexes with Argentoaurophilic Interactions. Inorg. Chem. 2014, 53, 10471−10484. (b) Blake, A. J.; Donamaria, R.; Fernández, E. J.; Lasanta, T.; Lippolis, V.; López-deLuzuriaga, J. M.; Manso, E.; Monge, M.; Olmos, M. E. Heterometallic gold(I)−thallium(I) compounds with crown thioethers. Dalton Trans. 2013, 42, 11559−11570. (10) (a) Sanaullah; Kano, K.; Glass, R. S.; Wilson, G. S. Chemical and electrochemical investigation of redox-associated conformational changes in the bis(1,4,7-trithiacyclononane)copper(II/I) system and xray structure of the copper(I) complex. J. Am. Chem. Soc. 1993, 115, 592−600. (b) Wyer, E.; Gucciardo, G.; Leigh, V.; Muller-Bunz, H.; Albrecht, M. Comparison of carbene and imidazole bonding to a copper(I) center. J. Organomet. Chem. 2011, 696, 2882−2885. (c) Blake, A. J.; Champness, N. R.; Howdle, S. M.; Webb, P. E. Silver(I) Coordination Polymers Using Thioether Macrocycle Building Blocks. Inorg. Chem. 2000, 39, 1035−1038. (d) Parker, D.; Roy, P. S.; Ferguson, G.; Hunt, M. M. Crystal and molecular structure of chloro-1,4, 7-trithiacyclononane gold(I): Adoption of a strained [225] conformation by the macrocyclic ligand. Inorg. Chim. Acta 1989, 155, 227−230. (e) Helm, M. L.; Hill, L. L.; Lee, J. P.; VanDerveer, D. G.; Grant, G. J. Cadmium-113 NMR studies on homoleptic complexes containing thioether ligands: the crystal structures of [Cd([12]aneS4)2](ClO4)2, [Cd([18]aneS4N2)](PF6)2 and [Cd([9]aneS3)2](PF6)2. Dalton Trans. 2006, 3534−3543. (f) Wilhelm, M.; Deeken, S.; Berssen, E.; Saak, W.; Lutzen, A.; Koch, R.; Strasdeit, H. The First Structurally Authenticated Organomercury(1+) Thioether Complexes − Mercury−Carbon Bond Activation Related to the Mechanism of the Bacterial Enzyme Organomercurial Lyase. Eur. J. Inorg. Chem. 2004, 2004, 2301−2312. (11) Blake, A. J.; Gould, R. O.; Li, W. S.; Lippolis, V.; Parsons, S.; Radek, C.; Schröder, M. Silver−Thioether Crown Complexes as Templates for the Synthesis of Extended Polyiodide Networks: Synthesis and X-ray Crystal Structures of [Ag2([15]aneS5)2]I12, [Ag([18]aneS6)]I7, [Ag([18]aneS6)]I3, and [Ag([9]aneS3)2]I5. Inorg. Chem. 1998, 37, 5070−5077. (12) (a) Blake, A. J.; Schröder, M. Thioether macrocycles as spacers for crystal engineering: synthesis and crystal structures of [Ag2([24]aneS8) (CF3SO3)2(MeCN)2]∞ and [Ag([16]aneS4) (BF4)]∞([24]aneS8 = 1,4,7,10,13,16,19,22-octathiacyclotetracosane; [16]aneS4 = 1,5,9,13-tetrathiacyclohexadecane). Chem. Commun. 1997, 1943−1944. (b) Blake, A. J.; Li, W. S.; Lippolis, V.; Taylor, A.; Schröder, M. J., Mercury(II), silver(I) and gold(I) thioether crown chemistry: synthesis, electrochemistry and structures of [(HgBr2)2([24]aneS8)], [{Ag2([24]aneS8) (CF3SO3)2(MeCN)2}∞], [Ag2([28]aneS8)][NO3]2 and [Au2([28]aneS8)][PF6]2 ([24]aneS8 = 1,4,7,10,13,16,19,22-octathiacyclotetracosane; [28]aneS8 = 1,4,8,11,15,18,22,25-octathiacyclooctacosane). J. Chem. Soc., Dalton Trans. 1998, 2931−2938. (13) Küppers, H.-J.; Wieghardt, K.; Tsay, Y.-H.; Krüger, C.; Nuber, B.; Weiss, J. Crown Thioether Complexes of AgI and CuI: The Crystal Structures of [{Ag3L3}AgL{AgL2}](ClO4)4 and [LCuI] (L = 1, 4, 7Trithiacyclononane). Angew. Chem., Int. Ed. Engl. 1987, 26, 575−576. (14) (a) Blake, A. J.; Champness, N. R.; Howdle, S. M.; Morley, K. S.; Webb, P. B.; Wilson, C. Silver(I)−thioether coordination polymers constructed using asymmetric diketonate anions. CrystEngComm 2002, 4, 88−92. (b) Yamaguchi, T.; Yamazaki, F.; Ito, T. A cyclic tetramer of [Ag(1,4,7-tri-thia-cyclononane)]+, cyclo-tetra-kis-(μ-1,4,7tri-thiacyclononaneκ3S1,S4,S7:κS1)tetrasilver(I) tetra-kis-(tri-fluoromethane K


Article

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Au Tetranuclear Complex

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