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Uncommon and Emissive {[Au(CHNS)][Au(CHNS)](PF)}, Mixed Au and Au Pseudo-Tetranuclear Crystalline Compound: Synthesis, Structural Characterization, and Optical Properties +

3+

Ana Paula Langaro, Ana Kely Rufino Souza, Claudio Yamamoto Morassuti, Sandro Marcio Lima, Gleison Antônio Casagrande, Victor Marcelo Deflon, Luiz Antônio de Oliveira Nunes, and Luis Humberto Da Cunha Andrade J. Phys. Chem. A, Just Accepted Manuscript • DOI: 10.1021/acs.jpca.6b08158 • Publication Date (Web): 19 Oct 2016 Downloaded from http://pubs.acs.org on October 21, 2016

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The Journal of Physical Chemistry

Uncommon and Emissive {[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2} Mixed Au+ and Au3+ Pseudo-Tetranuclear Crystalline Compound: Synthesis, Structural Characterization, and Optical Properties Ana P. Langaroa, Ana K. R. Souzaa, Claudio Y. Morassutia, Sandro M. Limaa, Gleison A. Casagrandeb, Victor M. Deflonc, Luiz A. O. Nunesd, Luis H. C. Andradea* a

Grupo de Espectroscopia Óptica e Fototérmica-GEOF, Centro de Estudos em Recursos

Naturais- CERNA, Universidade Estadual de Mato Grosso do Sul-UEMS, CP 351, Dourados, MS, Brazil; *[email protected], Tel +55-673902-2555 b

Instituto de Química, Universidade Federal de Mato Grosso do Sul – UFMS, Av. Senador Filinto Muller, 1555, 79074-460, Campo Grande, MS, Brazil

c

Instituto de Química, Universidade de São Paulo, São Carlos, CP 780, Av. do Trabalhador São Carlense, 400, Centro, 13560-970, São Carlos, SP, Brazil d

Laboratório de Laser e Aplicações, Instituto de Física de São Carlos, Universidade de São Paulo, São Carlos, SP, Brazil

ACS Paragon Plus Environment

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ABSTRACT:

An

uncommon

emissive

pseudo-tetranuclear

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compound,

{[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2}, was synthesized and characterized in terms of its structure and optical properties. The synthesis produced a crystalline compound composed of four gold atoms with two different oxidation states (Au+ and Au3+) in the same crystalline structure. The title complex belonged to a triclinic crystalline system involving the centrosymmetric 1 space group. X-ray diffractometry and vibrational spectroscopy (infrared, Raman, and SERS) were used for structural characterization of the new crystal. The vibrational spectroscopy techniques supported the X-ray diffraction results and confirmed the presence of bonds including Au–Au and Au–S. Optical characterization performed using UV-Vis spectroscopy showed that under ultraviolet excitation, the emissive crystalline complex presented characteristic broad luminescent bands centered at 420 and 670 nm.

Introduction The class of gold-based complexes is receiving much attention and is showing promising results in the area of anti-cancer drugs. The interest in this area is being encouraged by a variety of new gold complexes that have already been synthesized, or that are still waiting to be synthesized and evaluated. Research concerning gold complexes has so far mainly focused on complexes with gold in the (I) oxidation state, which are used in chrysotherapy for the treatment of rheumatoid arthritis. Other organometallic complexes also containing Au3+ have shown strong inhibitory effects on the growth of tumor cells,1 due to their cytotoxic activity.2-4 In developing new goldbased anti-cancer drugs, it is essential to design compounds that are capable of targeting specific biological sites and that have low or nonexistent toxic side effects. The synthesis of such gold complexes requires understanding of the behavior of gold ions in terms of the coordination chemistry and their biomolecular interactions, enabling the development of new ways to produce


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gold-based drugs.5 Due to their characteristic high reactivity, Au3+ complexes have received less attention than Au+ complexes. Under certain environmental conditions, Au3+ complexes can be easily reduced to Au+ and metallic gold in vivo, making them less effective as drugs. Despite this apparent instability, studies have found that the use of suitable ligands, such as multidentate compounds, can increase the stability of Au3+ complexes.5-7 The dithiocarbamates include a wide range of ligands that present rich and extensive coordination chemistry. Their importance arises from the ability to stabilize different metal ions, forming complexes that have varied oxidation states and geometries.8-9 Syntheses employing dithiocarbamate ligands and gold normally result in crystalline compounds containing S–Au bonds. The chelating effect and high capacity of dithiocarbamates to act as electron donors leads to substantial stabilization of the gold center in the (III) oxidation state, in different solvents. This is important when the compounds are used in biological systems for the treatment of arthritis and cancer.10 Hence, there is renewed interest in these complexes and the use of Au3+.11 In addition to the pharmacological properties of complexes involving Au+ and Au3+, these compounds can exhibit luminescence properties in both the solid state and in solution, with broad emission bands in the blue,12-13 yellow,14-15 and red spectral regions.16-17 The emission lifetimes can vary from nanoseconds to hundreds of microseconds.18 The broad emission bands also attract interest for the development of photonic materials.19 Considering the lack of reported studies concerning the synthesis and optical properties of mixed oxidation gold compounds, this work describes the synthesis and characterization of a new crystalline pseudo-tetranuclear compound with the formula {[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2}, using [(C6H5)3PAuCl] as the Au+ precursor and


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thiram as the ligand. The synthesized crystalline compound presented remarkable structural and luminescent features, including two Au+ atoms and two Au3+ atoms in the same crystalline structure and radiative lifetimes on the order of a few nanoseconds and microseconds. This compound could be an important material for use in the treatment of arthritis and cancer as well as in materials science. Experimental Synthesis of the crystalline compound {[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2} The synthesis was carried out in an opened flask in absence of inert (N2 or Ar) atmosphere and without further purification of solvents according to the methodologies already published in the literature.20-23 A good yield (57% (77.5 mg) in crystals) of the crystalline compound was obtained based on gold precursor and using a 1:1:1 molar ratio of [Au(C6H5)3PCl], thiram, and KPF6. To a solution containing 0.150 g (0.3 mmol) of the gold precursor ((C6H5)3PAuCl) dissolved in 6 mL of dichloromethane (CH2Cl2) at room temperature and with constant stirring during 5 min. To this same system, was added 0.06 g (0.3 mmol) of KPF6 was added with previously dissolved in 6 mL of methanol (CH3OH). After 5 min at room temperature and constant stirring, 0.08 g (0.3 mmol) of thiram (tetramethylthiuram disulfide, Aldrich®, 97%) was added to this system, followed by addition of 6 mL of acetonitrile (CH3CN). After 1 h of constant stirring, a red-brown suspension was observed and 2 mL of dimethyl sulfoxide ((CH3)2SO) as coordinating solvent was added aiming the complete dissolution of this suspension (after stirring for 15 min the system has become a red-brown limpid solution). Finally, in order to induce crystal growth, the solution was filtered and divided into two beakers covered by perforated plastic film, and kept to stand for slow volatilization of the solvent at room


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temperature. After 24 h it was observed the first crystals and 60 h after the preparation the remaining solution containing crystals was filtered and dried under vacuum condition. Properties: Air stable crystalline substance; Elemental analysis C/H/N (%) Calculated: 12.02/2.02/4.67; Found: 12.09/2.05/4.71. Figure 1(a) shows the precipitated crystals after performing the procedure described. The synthesized compound was analyzed using optical anisotropy. Figure 1(b) shows the {[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2} crystalline complex placed between two polarizers with crossed axes. The results indicated that single crystals were formed by following the synthesis procedure described. The compound was present as transparent brilliant red needles with optical anisotropy. X-ray diffraction X-ray data were collected using an Apex II CCD area detector diffractometer (Bruker) with graphite-monochromatized Mo Kα radiation. The crystal structure of the compound was solved by direct methods using SHELXS and refined with SHELXL28. All non-hydrogen atoms were localized from Fourier maps and refined with anisotropic displacement parameters. The hydrogen atoms were included at their theoretical ideal positions and treated with the “riding model” approximation, with C–H = 0.93 Å (aryl) as an option in SHELXL. Middle infrared absorption spectroscopy Spectra were obtained using photoacoustic Fourier transform infrared spectroscopy (FTIR-PAS), in the range 4000-400 cm-1, employing a spectrophotometer (Nexus 870, Nicolet) equipped with a photoacoustic detector (PAS). The photoacoustic cell was purged with helium gas to increase the gain of the photoacoustic signal. A black carbon reference was used to collect the spectrum


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of the infrared source for normalization. The spectra were obtained with a spectral resolution of 8 cm-1 and an average of 128 scans. Raman and SERS spectroscopy The Raman and surface-enhanced Raman scattering (SERS) experiments were performed using the same configuration setup and SERS substrates described elsewhere.24 In the Raman experiments, the samples were excited at 810 nm with a 22 mW Ti-sapphire laser (NBR 110, Coherent) pumped at 532 nm (Coherent Verdi G, 7 W power). This excitation wavelength was chosen in order to avoid luminescence interference. The SERS experiments were performed pumping the sample at 514.5 nm with a 20 mW argon laser (Innova 300 C, Coherent). A confocal setup using achromatic lenses with 8 mm focal length was used to focus the laser beam onto the samples, so that the SERS or Raman signals were detected from a spot size area of ~1 µm2. The scattered light at 514.5 nm and 810 nm was filtered using Semrock Razor Edge ultrasteep long-pass edge filters (models LP02-514RE-25 and LP02-808RE-25, respectively). The inelastic scattering was focused on a monochromator (iHR 320, Horiba Jobin Yvon). The crystal was deposited on a graphite support, and a PDA detector was used (Sygnature S39031024Q, Hamamatsu). Optical excitation and luminescence experiments For the optical excitation and luminescence experiments, the crystals were mechanically pressed over a graphite sample holder. The excitation spectrum was obtained using a fluorimeter fitted with a 150 W xenon lamp. The luminescence and excitation spectra were obtained using a SPEX Fluorolog spectrofluorometer (0.22 m, Spex/1680) equipped with a xenon lamp as the excitation source and a photomultiplier detector (R928, Hamamatsu). The time-resolved luminescence


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experiments were performed using an OPO laser (Vibrant 355, Opotek) with energy of 200 µJ per pulse and a 10 Hz repetition rate. Detection was performed using an ICCD (Andor Gen 2, W03 AGT, 512 x 512 pixels) coupled to a monochromator (iHR550, Horiba Jobin Yvon). 3

Results and Discussion

3.1

General considerations

The crystalline complex was obtained by the reaction of [(C6H5)3PAuCl] with KPF6 in a mixture of equal amounts of dichloromethane and methanol, followed by addition of the ligand. The Au(I)–Cl bond distance is approximately 2.276(13) Å, indicating that the chlorine atom is strongly bound to the Au+ metal center, so the bond is difficult to break. However, with the addition of KPF6, cleavage of the Au–Cl bond was promoted by the elimination of KCl, followed by the formation of the ionic [(C6H5)3PAu]+[PF6]– species in solution.12, 25-26 This new species was more electrophilic than [Au(C6H5)3PCl] and could easily react with the ligand by means of the sulfur atom, forming an Au–S coordination bond. The ligand was expected to be coordinated to the metal center (Lewis acid) via the sulfur atom (Lewis base), due to the high affinity between gold and sulfur atoms. The reaction consisted of an oxidation-reduction system where one Au+ atom was oxidized to Au3+, while the S–S disulfide bond was reduced to RS- (sulfide ion) in a two-electron process. The substitution of triphenylphosphine ligands from the coordination sphere of the Au+ center was achieved by bidentate chelation of the dithiocarbamate anion. 3.2 Structure of the crystalline complex According to the X-ray diffraction results, the crystal belonged to the triclinic system, with space group 1 (No. 2 - International Tables for Crystallography).27 The crystal structure was resolved


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by direct methods, using SHELX software.28-29 All the non-hydrogen atoms were refined with anisotropic displacement parameters, and the hydrogen atoms were included at their theoretical ideal positions. Detailed information about the structural determinations is provided in Table S1 (Supplementary Material). Since the observed reflection conditions were conducive to the symmetry operator (1), the space group 1 provided inversion centers as the sole symmetry element.

Figure

2

shows

the

crystalline

molecular

structure

of

the

{[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2} complex. The crystalline compound takes the form of a pseudo-tetranuclear compound containing Au+ and Au3+ (mixed oxidation state). It is an example of a mixed oxidation Au+ and Au3+ coordination compound. This kind of complex is not so common in the literature, to the best of our knowledge, few structures of this class of coordination compound have so far been characterized in X-ray studies.30-36 The molecular structure is presented as a cationic complex stabilized by a two [PF6]− anion. The subunit which contains two Au+ atoms Au2(C3H6NS2)2) is bonded concomitantly to two subunits [Au(C3H6NS2)2]2 which contain two Au3+ atoms) through µ2– S⋅⋅⋅Au secondary bonds (Au2–S2 and Au2#1–S2#1 of 3.4580(2) Å). We are considering that these µ2–S⋅⋅⋅Au secondary bonds are achieving the pseudo-tetranuclear crystalline structure. Pseudo-tetranuclear structures involving this kind of secondary bonds were reported for similar systems where µ2–alkoxo is the bridgeable group37. Bond angles for S1–Au1–S2 of 171.86(5)° and for S2–Au –Au1#1 of 94.48(3)° confirmed that the two Au+ atoms present in the structure adopted a “T” shaped coordination geometry. Two Au–S bonds of 2.2821(13) Å, followed by one strong metallophilic interaction (Au–Au1#1) of 2.7786(4) Å are completing the coordination sphere of the Au1 atoms (see Table 1).


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The Au2 atom presents an oxidation state Au3+ and consequently has coordination geometry different to that of Au+ atoms. From the analysis of the bond angles for S5–Au2–S3 (178.87(5)°), (S4–Au2–S6 (179.06(4)°), and S4–Au2–S3 (75.37(4)°), the coordination sphere of the Au2 atom could be described as a distorted square pyramid, a common coordination geometry presented by gold atoms with oxidation state Au3+. The S2 atom is occupying the apical position, via an Au2⋅⋅⋅S2 secondary bond of 3.4580(2) Å, whereas S3, S4, S5, and S6 are occupying the basal positions of the coordination polyhedron around the Au2 atom. The Au–S covalent bonds with lengths ranging from 2.3365(13) Å to 2.3462(13) Å (Table 1). Secondary bonds of the type Au⋅⋅⋅S were reported in the literature as been weaker than the Au–S covalent bonds, secondary bonds reported in the literature usually ranging from 3.365(3) to 3.951(2) Å 35-36, in the prepared complex herein presented the value 3.4580(2) Å is in accordance to the already published values. Figure 3 shows the unit cell content of the triclinic crystalline lattice. The full content comprised one entire molecule of the mixed oxidation Au+ and Au3+ coordination compound {[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2}. 3.3 Vibrational spectroscopy Vibrational spectroscopy was performed in order to enhance the characterization of the crystalline complex. Figure 4 shows the crystal and ligand (thiram) spectra obtained using FTIR, Raman spectroscopy, and SERS. The main bands identified and the associated functional groups are summarized in Table 2. The FTIR spectra of dithiocarbamate compounds show several vibrations of methyl groups, with bands at 828 cm-1 (-CH), 1041 cm-1 (ρ (CH3), ν (N-CH3)), 1149 cm-1 (ν (C-CH3), ν (CH3)), 2850 cm-1 (ν (N-CH3), N (CH3)2), and 2931 cm-1 (ν (CH3)).43 The main spectral regions used for the


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analysis are highlighted in the spectra for the crystal and the ligand (thiram). The region (a) in the ligand FTIR spectrum shows a peak at 848 cm-1, assigned to the PF6- linkage. The region (b) in the Raman spectrum of the crystal shows an intense peak at 185 cm-1, assigned to the vibration corresponding to the Au-Au linkage. The band at 828 cm-1 in region (c) shows additional peaks, corresponding not only to the CH vibrations, but also to stretching of PF6- present in the part of the molecules involving gold atoms, corroborating its presence in the structure. The SERS spectrum of the crystal, shown in Figure 4(III) (region (d)) presented a peak at 338 cm-1 corresponding to the δ (Au–S) bond. The SERS amplification bands are related to the bond angles of the different species at the nanorough silver surface, and comparison of the Raman and SERS spectra enabled determination of the geometry of the dissociated crystal molecules bound to the silver surface.45 A peak at 440 cm-1 could be assigned to δ (S–C–S) and was more intense than in the spectrum of the free ligand, reflecting a bond that was perpendicular to the silver nanostructure. It was expected that the pseudo-tetranuclear structure would dissociate in acetone, and when this solution was placed in contact with the nanorough silver surface, used for the SERS experiments, an Ag–S linkage was formed, due to the high known affinity of sulfur for silver atoms.40 Figures 5 show the possible configurations of this linkage. Other examples of disulfide cleavage during adsorption on a metal surface have been previously reported for other organic sulfur-containing compounds24. The presence of an intense SERS signal was due to the angle that S–Au–S–Ag makes with the surface, with bonds perpendicular to the surface being amplified due to the surface plasmon resonance. The peaks associated with the N–C–S bond, at 1474 and 1500 cm-1 (region (f) in Figure 4) were much smaller in the spectrum for the crystal, compared to the spectrum for the ligand. The very


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low intensity of this band in the SERS spectrum indicated that the bond was broken or was parallel to the Ag surface, resulting in a very weak influence of the vibrational modes associated with the surface plasmon resonance.40 3.4 Excitation and emission spectroscopy Figure 6 shows the excitation and emission spectra of the crystalline {[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2} complex. The excitation spectrum observed at 440 nm showed two broad excitation bands, one centered at 360 nm and another below 275 nm. A broad emission band from 340 to 600 nm was obtained when the crystalline complex was excited at 290 nm. This band presented a shoulder at 380 nm that coincided with the maximum of the excitation band, indicating that the intensity of this emission band could be influenced by reabsorption effects. This transition is the result of charge transfer from sulfur to Au(I) (S→Au, (dσ*)1 (pσ)1 or (dδ*)1 (pσ)1), under UV excitation.17, 46 The mechanism can involve two different sites of gold ions with S, together with the Au–Au pair (see Figures 2 and 3). The orbital calculations suggested that the HOMO-LUMO energy separation in the complex changed approximately linearly with Au–Au distance. In other words, the change in the Au–Au distance was accompanied by a shift of the visible emission to lower energies. This effect was in agreement with the structural characterization, confirming that the metal ligand emission was strongly perturbed by the Au–Au pairs.15, 47 3.5 Time-resolved luminescence spectroscopy Figure 7 shows the temporal evolution of the luminescence spectra obtained under pulsed excitation at 230 nm. Two broad emission bands centered at 430 and 670 nm were observed, covering the spectral regions 330-500 nm and 500-900 nm, respectively. As already discussed,


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the spectra shown in Figure 7(a) were related to the charge transfer from S atoms to Au+ (ligand to metal charge transfer, LMCT).17, 48 This blue emission could also have been caused by increased separation of the Au–Au linkage, due to an increase of the crystal temperature under excitation, which led to thermal expansion in the crystal and alteration of the HOMO-LUMO gap.15 In the case of the red emission (shown in Figure 6(b)), this could be attributed to the metal center (MC) of the Au–Au interaction.49 Figure 8(a) shows luminescence spectra recorded using two different time delays. At 0 s, the band was centered at 550 nm, while the emission recorded after this time showed a maximum at 680 nm. This behavior indicated the existence of two emission bands associated with different energy level configurations. Emission at 550 nm occurred rapidly (within nanoseconds), while the other presented a lifetime of 7.2 µs, as can be observed from the decay profile shown in Figure 8(b). The band with the short decay time was probably caused by LMCT that was not perturbed by the Au–Au pairs. In this case, the emission was likely to have been from Au2S(1,2,3,4), which was distant from the Au+ or Au3+. For the slower emission band, the lifetime was similar to those reported for other crystals doped with Au+ that present Au–Au interactions, 4

Conclusions

An uncommon and emissive {[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2} complex utilizing thiram and [(C6H5)3PAuCl] as a starting materials was synthesized in good yield using a simple and reproducible procedure. The synthetic procedures allowed the production of a new crystalline compound containing four gold atoms with different oxidation states. The structure of the crystalline compound was characterized, and good correlations were found between structural and spectroscopic features. Vibrational spectroscopy analyses enabled determination of the


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molecular crystal structure, which was consistent with the structural analysis. In optical measurements, two broad emission bands were observed, one centered in the blue region at 430 nm, due to LMCT excitations from S to Au+ atoms, and another centered at 670 nm, covering the visible and near-infrared region, due to LMCT perturbed by the Au–Au pairs. The presence of the broad blue emission band is promising for photonic applications, and the presence of both Au+ and Au3+ valences in the same crystalline structure should be very useful in medicine for the development of arthritis and anti-cancer drugs. 5

Supporting Information Available

Table of Crystal Data is provided. Acknowledgments The authors are grateful for the financial support provided by the Brazilian research support agencies CAPES, CNPq, and FUNDECT. Author Contributions The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript. ‡These authors contributed equally. (match statement to author names with a symbol)


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References (1) Ott, I. Review: On the Medicinal Chemistry of Gold Complexes as Anticancer Drugs. Coord. Chem. Rev. 2009, 253, 1670–1681. (2) Yamashita, M.; Ichinowatari, G.; Yamaki, K.; Ohuchi, K. Inhibition by Auranofin of the Production of Prostaglandin E2 and Nitric Oxide in Rat Peritoneal Macrophages; Eur. J. Pharmacol. 1999, 368, 251-258. (3) Erdogan, E.; Lamark, T.; Stallings-Mann, M.; Lee, J.; Pellecchia, M.; Thompson, E. A.; Johansen, T.; Fields, A. P. Aurothiomalate Inhibits Transformed Growth by Targeting the PB1 Domain of Protein Kinase Ciota. J. Biol. Chem. 2006, 281, 28450-28459. (4) Maruyama, T.; Sonokawa, S.; Matsushita, H.; Goto, M. Inhibitiory Effects of Gold(III) Ions on Ribonuclease and Deoxyribonuclease. J. Inorg. Biochem. 2007, 101, 180-186. (5) Milacic, V.; Ping Dou, Q.; The Tumor Proteasome as a Novel Target for Gold(III) Complexes: Implications for Breast Cancer Therapy. Coord. Chem. Rev. 2009, 253, 1649-1660. (6) Ronconi, L.; Giovagnini, L.C.; Marzano, F.; Bettio, R.; Graziani, G.; Pilloni, D.; Fregona, J. Gold Dithiocarbamate Derivatives as Potential Antineoplastic Agents: Design, Spectroscopic Properties, and in Vitro Antitumor Activity. Inorg. Chem. 2005, 44, 1867-1881. (7) Ronconi, L.; Marzano, C.; Zanello, P.; Corsini, M.; Miolo, G.; Macca, C.; Trevisan, A.; Fregona, D. J.. Gold(III) Dithiocarbamate Derivatives for the Treatment of Cancer: Solution Chemistry, DNA Binding, and Hemolytic Properties. Med. Chem. 2006, 49, 1648-1657. (8) Barone, G.; Chaplin, T.; Hibbert, T. G.; Kana, A. T.; Mahon, M.F.; Molloy, K. C.; Worsley, I. D.; Parkin, I. P.; Price, L. S. Synthesis and Thermal Decomposition Studies of Homo- and


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Heteroleptic Tin(IV) Thiolates and Dithiocarbamates: Molecular Precursors for tin Sulfides. J. Chem. Soc. Dalton Trans. 2002, 1085-1092. (9) Kana, A. T.; Hibert, T. G.; Mahon M. F.;, Molloy, K. C.; Parkin, I. P.; Price. L. S.; Organotin Unsymmetric Dithiocarbamates: Synthesis, Formation and Characterisation of tin(II) Sulfide Films by Atmospheric Pressure Chemical Vapour Deposition. Polyhedron 2001, 20, 2989-2995. (10) Ronconi, L.; Maccato, C.; Barreca, D.; Saini, R.; Zancatoc, M.; Fregona, D. Gold (III) Dithiocarbamato Derivatives of n-methylglycine: an Experimental and Theoretical Investigation. Polyhedron 2005, 24, 521–531. (11) Messori, L.; Marcon, G.; Orioli, P.; Gold(III) Compounds as New Family of Anticancer Drugs. Bioinorg. Chem. Appl. 2003, 87, 177-187. (12) Ferle, A.; Pizzuti, L.; Inglez, S. D;. Caires, A. R. L.; Lang, E. S.; Back, D. F.; Flores, A. F. C.; Júnior, A. M.; Deflon, V. M.; Casagrande. G. A. The First Gold (I) Complexes Based on Thiocarbamoyl-Pyrazoline Ligands: Synthesis, Structural Characterization and Photophysical Properties. Polyhedron 2013, 63, 9-14. (13) Bardají, M.; Calhorda, M. J.; Costa, P. J.; Jones, P. G.; Laguna, A.; Pérez, M. R.; Villacampa M. D. Synthesis, Structural Characterization, and Theoretical Studies of Gold(I) and Gold(I)Gold(III) Thiolate Complexes: Quenching of Gold(I) Thiolate Luminescence. J. Inorg. Chem. 2006, 45, 1059−1068. (14) Mansur, M. A.; Connick, W. B.; Cachicotte, R. J.; Gysling, H. J.; Eisenberg, R. Linear Chain Au(I) Dimer Compounds as Environmental Sensors: A Luminescent Switch for the Detection of Volatile Organic Compounds. J. Am. Chem. Soc. 1998, 120, 1329-1330.


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(22) Lang, E. S.; Oliveira, G. M.; Casagrande, G. A.; Vazquez-Lopez, E. M. Induced Crystallization of Polymeric Cd(II)-DMPYS Assemblies (DMPYS ¼ 4,6-dimethyl- pyrimidine2-thiolato): Synthesis and Chaining Structures of a- and b-[Cd(DMPYS)2] n. Inorg. Chem. Com. 2003, 6, 1297-1301. (23) Oliveira, G. M.; Casagrande, G. A.; Fernandes, R. M.; Faoro, E.; Lang, E. S.; Mayer, P. One Step Substitution of NO and Cl by a Metal-SCN-ring in CpCr (NO) 2 Cl: Synthesis and Molecular Structure of CpCr (NO)‘DMPYS’(Cp= π-C 5 H 5; DMPYS= 4, 6-dimethylpyrimidine-2-thiolato). J. Org. Chem. 2002, 656, 177-180. (24) Almeida, F. S.; Bussler, L.; Lima; S. M.; Andrade, L. H. C. High Surface-Enhanced Raman Scattering (SERS) Amplification Factor Obtained with Silver Printed Circuit Boards and the Influence of Phenolic Resins in Characterization of the Pesticide Thiram , Appl. Spectrosc. 2016, 70 (7), 1157-1164. (25) Kouroulis, K. N.; Hadjikakou, S. K.; Kourkoumelis, N.; Kubicki, M.; Male, L.; Hursthouse, M.; Skoulika, S.; Metsios, A. K.; Tyurin, V. Y.; Dolganov, A. V.; et al. Synthesis, structural characterization and in vitro cytotoxicity of new Au(III) and Au(I) complexes with thioamides. Dalton Trans. 2009, 10446-10456. (26) Kenji, N.; Ryusuke, N.; Katsunori, O.; Kazuhiro, T. Synthesis and Crystal Structure of Gold(I) Complexes With Triazole and Triphenylphosphine Ligands: Monomeric Complex [Au(1,2,3-L)(PPh3)] and Dimeric Complex [Au(1,2,4-L)(PPh3)]2 (HL = triazole) Through an Au–Au Bond in the Solid State. Dalton Trans. 1998, 4101-4108. (27) Hahn, T. International Tables for Crystallography, Vol. A Space-Group Symmetry, 1987.


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(28) Sheldrick, G.M. A Short History of SHELX. Acta Cryst. 2008, 64, 112-122. (29) Farrugia, L. J. ORTEP-3 for Windows - A Version of ORTEP-III With a Graphical User Interface (GUI). J. Applied Cryst. 1997, 30, 568-568. (30) Raptis, R. G.; Fackler, J. P. Synthesis and Crystal Structure of a Mixed-valence, Digold(I)/Gold(III), Pyrazolato Complex Stable in Aqua Regia. X-ray Photoelectron Study of Homo- and Heterovalent Gold-Pyrazolato Trimers. Inorg. Chem. 1990, 29, 5003-5006. (31) Raptis, R. G.; Emrich, R. J.; Porter, L. C.; Fackler, J. P.; Murray, H. H. Synthesis of a Mixed-Valence Gold(I)/Gold(III) Complex, [Au(CH2)2PPh2]2Br2, and its Characterization by Xray Crystallography and X-ray Photoelectron Spectroscopy. Inorg. Chem. 1990, 29, 4408-4412. (32) Mazany, A. M.; Fackler, J. P. Isomeric Species of the Dinuclear Iodogold Complex [AuCH2P(S)PhI]2. Mixed-Valent Gold(I)/Gold(III) and Isovalent Gold(II)-Gold(II) Complexes With the Same Methylenethiophosphinate Ligand. J. Am. Chem. Soc. 1984, 106, 801-802. (33) Rodina, T.A.; Ivanov, A. V.; Gerasimenko, A. V.; Loseva, O. V.; Antzutkin, O. N.; Sergienko, V. I. Fixation Modes of Gold(III) From Solutions Using Cadmium(II) Dithiocarbamates. Preparation, Supramolecular Structure and Thermal Behaviour of Polynuclear and Heteropolynuclear Gold(III) Complexes: Bis(N,N- dialkyldithiocarbamato-S,S`) Gold(III) Polychlorometallates, [Au(S2CNR2)2]nX (n = 1: X = [AuCl4]-; n = 2: X = [CdCl4]2-, [Cd2Cl6]2-). Polyhedron 2012, 40, 53-64. (34) Loseva, O. V.; Ivanov. A. V. Interaction of Binuclear Zinc Diethyldithiocarbamate with H[AuCl4]/2 M HCl: The Preparation, Supramolecular Self_Organization, and Thermal Behavior of the Heteropolynuclear Complex ([Au{S2CN(C2H5)2}2]2[ZnCl4]

1/2CO(CH3)2

1/2CHCl3)n. Russ. J. Inorg. Chem. 2014, 59, 1737-1746.


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(35) Ivanov, A. V.; Zinkin, S. A.; Sergienko, V. I.; Gerasimenko, A. V.; Zaeva, A. S.; Loseva, O. V. Gold(III) Preconcentration from Acid Solutions by Cadmium Diisopropyldithiocarbamate: Gold(III) Binding Species, Supramolecular Structure, and Thermal Properties of the Heteropolynuclear Complex ([Au{S2CN(iso-C3H7)2}2]2[CdCl4]

1/2C3H6O)n. Russ. J. Inorg.

Chem. 2011, 56, 409-417. (36) Lutsenko, I. A.; Ivanov, A. V.; Kiskin, M. A.; Ogil’ko, G. V. Gold(III) Ionic Complexes [Au{S2CN(C2H5)2}2]Cl and ([Au{S2CN(C2H5)2}2][AuCl4])n: Synthesis, Supramolecular Self_Assembly, Polymorphism, and Thermal Behavior. Russ. J. Inorg. Chem. 2015, 60, 92-99. (37) Lhoste, J.; Henry, N.; Roussel, P.; Loiseau, T.; Abraham, F. An Uranyl Citrate Coordination Polymer with a 3D Open-framework Involving Uranyl Cation-Cation Interactions. Dalton Trans. 2011, 40, 2422-2424. (38) Smith, B. Infrared Spectral Interpretation: A Systematic Approach. New York: CRC Press, 1999, 200. (39) Kang, J. S.; Hwang, S. Y.; Lee, C. J.; Bull, M. S. SERS of Dithiocarbamate Pesticides Adsorbed on Silver Surface; Thiram. Korean Chem. Soc. 2002, 23, 1604-1610. (40) Sánchez-Cortés, S.; Vasina, M.; Francioso, O.; García-Ramos, J. V. Raman and SurfaceEnhanced Raman Spectroscopy of Dithiocarbamates Fungicides. Vib. Spectrosc. 1998, 17, 133144. (41) Tong, M. C.; Chen, W.; Sun, J.; Ghosh, D.; Chen, S. Dithiocarbamate-Capped Silver Nanoparticles. J. Phys. Chem. B. 2006, 110, 19238-19242. (42) Alverdi, V.; Giovagnini, L.; Marzano, C.; Seraglia, R.; Bettio, F.; Sitran, S.; Graziani, R.; Fregona, D. Characterization Studies and Cytotoxicity Assays of Pt(II) and Pd(II)


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Dithiocarbamate Complexes by Means of FT-IR, NMR Spectroscopy and Mass Spectrometry. J. Inorg. Biochem. 2004, 98, 1117-1128. (43) Colthup, N. B.; Daly, L. H.; Wiberley, S. E. Introduction to Infrared and Raman Spectroscopy, 3rd ed. Academic Press, , New York, 1990, 1-74. (44) Ru, E. L.; Etchegoin, P. Principles of Surface Enhanced Raman Spectroscopy, 1st ed. Oxford: Elsevier, 2009, 1-27. (45) Leyton, P.; Sanchez-Cortes, S.; Campos-Vallette, M.; Domingo, C. ; Garcia-Ramos, J. V.; Saitz, C. Surface Enhanced Micro-Raman Detection and Characterization of Calix[4] ArenePolycyclic Aromatic Hydrocarbons (PAHs) Host-Guest Complexes. Appl. Spectrosc. 2005, 59, 1009-1015. (46) Van Zyl, W. E.; López-de-Luzuriaga, J. M.; Fackler, J. P.; Luminescence Studies of Dinuclear Gold(I) Phosphor-1,1-dithiolate Complexes. J. Molec. Struct. 2000, 516, 99–106. (47) Ma, Y.; Zhou, X.; Shen, J.; Chao, H.; Che, C. Triplet Luminescent Dinuclear-Gold(I) Complex-Based Lightemitting Diodes with Low Turn-on Voltage. Appl. Phys. Lett. 1999, 74, 1361-1363. (48) King, C.; Luminescence and Metal-Metal Interactions in Binuclear Gold(I) Compounds. J. Inorg. Chem. 1989, 28, 2145-2149. (49) King, C.; Khan, M. N. I.; Staples, R. J.; Fackler, J. P. Luminescent Mononuclear Gold(I) Phosphines. J. Inorg. Chem. 1992, 31, 3236-3238.


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Tables Table 1. Interatomic distances and angles involving Bond lengths and bond angles involving the Au+ and Au3+ atoms in the complex. Bond lengths(Å)

Bond angles (°)

Au1–S1

2.2821(13)

S1–Au1–S2

171.86(5)

Au1–S2

2.2812(13)

S2–Au–Au1#1

94.48(3)

Au–Au1#1

2.7786(4)

S5–Au2–S6

75.37(5)

Au2–S3

2.3417(12)

S4–Au2–S3

75.37(4)

Au2–S4

2.3365(13)

S5–Au2–S3

178.87(5)

Au2–S5

2.3365(13)

S4–Au2–S6

179.06(4)

Au2–S6

2.3462(13)

S3–Au2–S6

105.31(4)

Au2#1–S2#1

3.4580(2)

S2#1–Au2–S6

92.28(4)

Au2–S2

3.4580(2)

#1 -x+1, -y+2, -z


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Page 22 of 32

Table 2. Selected crystal peaks in each {[Au2(S2C3NH6)2][Au2(S2C3NH6)4](PF6)2} spectrum, and their corresponding functional groups.38-44 PAS-FTIR (cm-1)

Raman (cm-1)

SERS (cm-1)

Functional group

-

138

-

δ (Au-S-C)

-

185

-

ν (Au-Au)

-

328

-

ν (Au-S)

-

340

338

ν (Au-S)

-

358

357

ν (CH3-NC)

-

407

400

ν ((CH3)2-N)

439

-

-

δ (CH3NC)

-

440

440

δ (S-C-S)

556

550

553

ν (S-S)

563

532

541

δ (S-C-S)

790

-

-

C-S

828

-

868

C-H or v(P-F)

875

-

-

C-N

971

-

-

ν (CH3N) or ν (C-S)

1041

-

-

ρ (CH3) or ν (CH3-N)

1149

1134

1134

ρ (N-CH3), ν (CH3)

1234

-

-

δ (CH3-N-C)

-

-

1375

δs (CH3)

1496

-

1474

ν (C-N)

-

-

1500

ν (C=N)

1699

-

-

ν (C-N)

2850

-

-

ν N-CH3 or ν N-(CH3)2

2931

-

-

νs (CH3)


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Figure Captions Figure 1. (a) Synthesized transparent needle-shaped crystals. (b) Optical anisotropy test, with insertion of the crystals between two polarizers with crossed polarization axes. Figure 2. Molecular structure of the {[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2} complex. The hydrogen atoms were omitted for clarity. Symmetry transformations used to generate equivalent atoms: #1 -x+1, -y+2, -z; #2 –x+1, -y+1, -z.

Figure

3.

Unit

cell

content

of

the

triclinic

lattice

of

the

{[Au2(C3H6NS2)2][Au(C3H6NS2)2]2(PF6)2} complex. Gold and sulfur atoms are shown as red and yellow spheres, respectively. Hydrogen atoms are omitted for clarity. Figure 4. (I) FTIR spectra of the complex and thiram; (II) Raman spectra of the crystal and thiram, with excitation at 808 nm and 514.5 nm; (III) SERS spectra of the crystal and thiram, with excitation at 514.5 nm. Figure 5. Possible bond configuration of the gold complex on a nanorough silver surface. Figure 6. Crystal excitation spectra observed at 440 nm, and emission spectra recorded under excitation at 290 nm. Figure 7. Time-resolved luminescence spectroscopy with excitation at 230 nm: (a) emission band centered at 420 nm; (b) emission band centered at 660 nm. Figure 8. (a) Luminescence recorded using different time delays; (b) decay profile of the long emission band centered at 680 nm.


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Figure 1


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Figure 2


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Figure 3


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Figure 4


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Figure 5


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Figure 6


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(a)

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(b)

Figure 7


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(a)

(b)

Figure 8


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TOC Figure


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