Luminescent metal complexes containing naphthalene and anthracene units 2

Chapter Synthesis, Structures and Electronic Spectroscopy of Copper and Gold Complexes of NS22- 36 2.1 Introduction Described in this chapter are the reactions of Cu(I) and Au(I)/Au(III) with 1,8- naphthalenedithiolate anion (NS22-) and the structures and electronic spectroscopy of the resulting complexes. 2.2 Results and Discussion 2.2.1 Synthesis of 1,8-Napthalenedithiol (NS2H2) The ligand NS2H2 was synthesized according to the reported method.1 First of all, naphtho[l,8-cd]-1,2-dithiole was synthesized from reacting 1,8-diiodonaphthalene with nbutyllithium and elemental sulfur. The dithiol can be obtained by reducing naphtho[l,8-cd]-1,2dithiole with sodium borohydride followed by addition of hydrochloric acid ( yield= 32% for two steps). The synthetic routine is depicted in Figure 2.1. Figure 2.1 I I n-BuLi, S O2, THF 1,8-diiodonaphthalene S S NaBH4 SH SH HCl naphtho[l,8-cd]-1,2-dithiole 1,8-naphthalenedithiol As NS2H2 is highly air-sensitive and easily oxidized back to naphtho[l,8-cd]-1,2 – dithiole, it was not isolated. When required, the compound would be generated in situ by reducing naphtho[l,8-cd]-1,2 –dithiole with sodium borohydride. 2.2.2 Structure of [Cu4(µ2-dppm)3(µ2- µ2-NS2)( µ2- µ4-NS2)] (2.1) In distilled THF reacting NS22- and molar equiv. of [Cu2(µ2-dppm)2(CH3CN)2](PF6)2 at room temperature for 0.5 hour gave the tetranuclear complex [Cu4(µ2-dppm)3(µ2-µ2-NS2(µ2-µ4NS2)] (2.1) as the major product. The yield is 50% with high purity. Orange block crystal was grown by slowly evaporation diethyl ether in the MeOH/CH2Cl2 solution. The molecule shows a 37 planar Cu4 core to which two dppm and one NS22- coordinate in the equatorial positions. The other NS22- and dppm are nearly perpendicular to the plane of Cu4 core. The four Cu ions form an irregular quadrangle; the Cu(3)-Cu(4) distance of 2.641(2) Å is shorter than the distance between Cu(1)-Cu(2) (3.074(2) Å) and Cu(1)-Cu(4) (3.335(2) Å). This difference in metal–metal distance could be due to electronic effects3 as the Cu(3) and Cu(4) ions are bridged by µ2-S(3) and µ2-S(4) and a µ4-S(4) but the Cu(1) and Cu(2) are only bridged by one µ2-S(1) and one µ2-S(2). Of particular interest is the atom S(2) which is almost equidistant from the four Cu ions (Cu-S(2)= 2.392(2)-2.448(2) Å)). The Cu-µ4-S(2) distances are close to the Cu-µ2-S distance (2.321(2)2.424(2) Å) and similar bond distance are observed in other polynuclear CuI-thiolate complexes such as [Cu2(PPh3)4(µ2-SPh)2] (Cu-S=2.34 and 2.42 Å).5d That the S(2) coordinated to four CuI ion makes 2.1 be the first compound with a pentacoordinate sulfur. The bridging Cu-S-Cu angles range from 67.06(6) º to 80.95(7) º. These values are close to the Cu-S-Cu angles (70º - 80º) found in some CuI complexes which contain bridging thiolates. 4,5, Figure 2.2 ORTEP diagram of 2.1. Thermal ellipsoids are drawn with 50% probability. All the hydrogen atoms, phenyl rings and solvent molecules are omitted. 38 The ESI-MS of 2.1 shows the molecular peaks at m/z 1785.9 (M+, 57%). In addition, peak corresponding to [Cu2(dppm)(NS2)]+ is present at m/z 1086.8. In the 1H NMR (CD2Cl2), the proton on the naphthalene and phenyl group of dppm in the range of 6.14-9.09 ppm. The chemical shifts at 7.86 ppm (s, 1H), 7.98 ppm (dd, 1H) and 9.08 ppm (d, 1H) is assigned as proton on the NS2. The elemental analysis and H NMR all prove the existence of dichloromethane molecule at 5.3 ppm (s, 1H) in CDCl3, the integration and chemical shift is consistent with 0.5 dichloromethene molecular existing in the 2.1. Table 2.1 Selected bond length (Å) and angles (deg) for the compound 2.1 Bond length (Å) Cu(1)-S(1) Cu(2)-S(1) Cu(1)-S(2) Cu(2)-S(2) Cu(3)-S(2) Cu(4)-S(2) Cu(3)-S(3) Cu(4)-S(4) Cu(1)-P(1) Cu(1)-P(2) Cu(3)-P(5) Cu(1)-Cu(2) Cu(2)-Cu(3) Cu(3)-Cu(4) Cu(4)-Cu(1) 2.2.3 2.378(2) 2.357(2) 2.392(2) 2.392(2) 2.448(2) 2.419(2) 2.356(2) 2.341(2) 2.284(2) 2.272(2) 2.189(2) 3.074(2) 3.709(2) 2.641(2) 3.355(2) Bond angle (deg) Cu(1)-S(1)-Cu(2) Cu(1)-S(2)-Cu(2) Cu(1)-S(2)-Cu(3) Cu(3)-S(2)-Cu(4) Cu(1)-S(2)-Cu(4) Cu(3)-S(3)-Cu(4) Cu(3)-S(4)-Cu(4) S(4)-Cu(4)-S(3) S(2)-Cu(4)-S(3) S(4)-Cu(4)-Cu(3) S(2)-Cu(4)-Cu(3) S(3)-Cu(4)-Cu(3) 80.95(7) 79.97(7) 139.17(9) 65.71(6) 87.77(6) 67.06(6) 68.99(6) 87.81(7) 97.93(7) 55.15(5) 57.67(5) 55.24(5) Structure of [Cu5(µ2-dppm)4(µ3-µ3-NS2)2] PF6( 2.2•PF6) When the reaction of NS22- and [Cu2(µ2-dppm)2(CH3CN)2](PF6)2 was carried out in degassed THF for h at room temperature, another complex [Cu5(µ2-dppm)4(µ2-µ3-NS2)]•PF6 (2.2•PF6) was produced in moderate yield (35.8%). The most intriguing structural feature of the complex as revealed by X-ray crystallography is a square Cu5 core which consists of four Cu ions at the corners and one Cu ion at the center of the square (Figure 2.3 and 2.4). The Cu5 core, which is essentially planar, is connected to four equatorial dppm and two axial NS22- whose naphthalene rings are nearly orthogonal to each other with their planes slightly deviated from the middle lines of the square. The dppm are bent from the plane of Cu5, showing an alternate”updown” conformation. This gives the molecule a saddle-like configuration as observed in [Cu4(µ2dppm)4(µ2-CS3)2]5b and [Cu4(µ2-dppm)4(µ2-S)]2+. 7b The Cu-P bond lengths are similar to those 39 found in 2.1. Each sulfur atom of the two dithiolates bridges two Cu ions on each side of the square. The bridging is slightly asymmetric as the S atom is closer to one of the Cu ions than the other (Cu(1)-Cu(2)=2.5182(1) Å and Cu(2)-S(1)=2.3539(1) Å. As a result, the complex shows an approximate S4 symmetry with the S4 (and hence C2) axis passing through the central Cu ion which is also the center of inversion. Notably, the molecular structure of the cation 2.2+ is surprisingly similar to those of [Cu4(µ2-dppm)4(µ2-CS3)2]5b and {Cu4(µ2-dppm)4(µ2- S2CC(CN)P(O)(OEt)2)},5c both feature a square Cu4 capped symmetrically by two 1,1-ditholate ions. However, The Cu-Cu distances between the peripheral Cu ions in 2.2+ (3.881(2)-3.934(2) Å) are much longer than the corresponding ones in [Cu4(µ2-dppm)4(µ2-CS3)2] (3.305(6)-3.32(6) Å)5b and {Cu4(µ2-dppm)4(µ2-S2CC(CN)P(O)(OEt)2)} (3.186-3.395 Å)5c. Apparently, the parallel orientation of the two C-S bonds and the longer distance between the two S atoms in NS22- allow the Cu4S4P6 scaffold to undergo expansion to accommodate the fifth Cu ion. The central Cu(5) ion is coordinate to the four sulfur atoms in a tetrahedral geometry (Cu(5)-S=2.2721(1)-2.2844(1) Å and S-Cu-S=102/14(5)-114/26(5) º) and accordingly the S atoms are in bridging mode. The fact that Cu(5)-S bond lengths are significantly shorter than the peripheral Cu-S bond length indicates stronger bonding interaction between the S atoms and the central copper atom. Moreover, the central Cu is 2.7472(8)-2.7897(8) Å away from the four peripheral Cu ions. It is known that CuI•••CuI interaction is possible within such distances.8 An interesting way to interpret the structure is to consider the Cu4S4 core as metallacrown9 which traps a Cu in the center via S-Cu coordination and possible cuprophilic interaction. The few reported CuI5 complexs show regular bipyramidal (e.g. [Cu5(µ2- StBu)6])4a or open cubane (e.g. [Cu5(µ2SPh)7]2-)4b metal cores. As far as we are aware, the 2-D array Cu5 exhibited by 2.2+ is unprecedented. The S4 symmetry observed in the X-ray crystal structure could be resulted from crystal packing as the solution 31P{1H} NMR spectrum of the complex exhibits a singlet at 13.0 ppm. This indicates that the complex reverts to a higher symmetry, i.e. D2d, where all the P atoms are equivalent. The 1H NMR spectrum of 2.2 is very simple. The proton peak at 8.08 (dd, 4H), 7.60 (dd, 4H), 7.41 (dd, 4H) indicating the existence of NS2, there are two sets of proton peaks of phenyl ring prove the two kinds of geometry of dppm. Two CH2 peaks at 3.07 ppm (d, 4H) and 40 2.62 ppm (d, 4H) also prove the two kinds of dppm in the molecule. In 31P NMR, seven peaks in the range of -132.8 to -156.2 ppm (1JP, F = 708 Hz) show the PF6- anion in the CD2Cl2. Figure 2.3 ORTEP diagram of 2.2, Thermal ellipsoid are drawn with 50% Figure 2.4 ORTEP diagram of 2.2. Thermal ellipsoid is drawn with 50% probability. All the hydrogen atoms and phenyl carbon rings are omitted for clarity 41 The FAB Mass measurement showed a cation peak at m/z=2236.1 (5%), corresponding to the [Cu5(µ2-dppm)4(µ2-µ3-NS2)2] cations and an anion peak at m/z=145 indicating the existence of PF6- anion. Table 2.2 selected bond length (Å) and angles (deg) for the compound 2.2 Bond Lengths Cu(1)-S(4) Cu(1)-S(1) Cu(2)-P(2) Cu(2)-P(3) Cu(2)-S(1) Cu(2)-S(3) Cu(4)-S(2) Cu(4)-S(4) Cu(5)-S(2) Cu(5)-S(4) Cu(5)-S(1) Cu(5)-S(3) Cu(1)-Cu(5) Cu(3)-Cu(5) Cu(4)-Cu(5) Cu(2)-Cu(5) Cu(1)-Cu(2) Cu(2)-Cu(3) Cu(3)-Cu(4) Cu(4)-Cu(1) 2.2.4 2.3233(13) 2.5182(13) 2.2432(13) 2.2482(13) 2.3539(13) 2.4702(14) 2.3103(13) 2.5685(13) 2.2721(13) 2.2781(13) 2.2826(14) 2.2844(13) 2.7520(8) 2.7472(8) 2.7525(8) 2.7897(8) 3.881(1) 3.904(1) 3.934(1) 3.897(1) Bond angles Cu(1)-S(1)-Cu(2) S(1)-Cu(5)-S(2) S(3)-Cu(5)-S(1) S(1)-Cu(5)-S(4) S(4)-Cu(5)-S(2) P(1)-Cu(1)-P(2) Cu(1)-Cu(5)-Cu(2) S(3)-Cu(3)-S(2) P(8)-Cu(1)-S(4) P(1)-Cu(1)-S(1) 105.58(5) 102.14(5) 111.36(5) 113.14(5) 114.26(5) 123.67(5) 88.92(2) 103.39(4) 109.41(5) 99.09(5) Electronic and Luminescent Spectra of 2.1 and 2.2• PF6 Table 2.3 the photophysical data for complex 2.1-2.2• PF6 complex Solvent (T, 298 K) Absorption λmax (nm) Emission λmax (nm) 2.1 CH3CN 375 εmax (dm3mol-1cm-1) 49700 2.2• PF6 CH3CN 360 18100 489, 620 NS2 CH3CN 242nm 364nm 19700 10700 410 486, 620 As we suppose, tetranuclear and pentranuclear copper(I) clusters have rich photophysical and photochemical properties. Electronic spectrum of the NS2 ligand in CH3CN is illustrated in Figure 2.5. It is noted that apart from an intense π→π* transition at 242 nm (εmax = 1.90×104 M1 cm-1), 10 the spectrum of NS2 displays an absorption band at 364 nm (εmax = 1.07×104 M-1cm-1) 42 which is attributable to n(S) →π* transition. Compared absorption spectra of the complexes with NS2, the absorptions are easy to be assigned. 2.5x10 -1 -1 Extinction Coefficient (M .cm ) 2.0x10 1.5x10 1.0x10 5.0x10 0.0 200 250 300 350 400 450 Wavelength (nm) Figure 2.5 UV-vis spectrum of compound NS2 (9.47×10-5M) in CH3CN at room temperature The electronic absorption spectra of 2.1 and 2.2• PF6 display intense band at 375nm (εmax = 5.0×104 M-1cm-1) and 360nm (εmax = 1.8×104 M-1cm-1), respectively (Figure 2.6, Figure 2.7). In view of the similar energy and intensity with NS2, The absorption at 375 nm and 360 nm are assigned to intraligand n(S) → π* transitions. While NS2 does not absorb between 270 - 310 nm and beyond 400 nm, the two copper complexes show moderate absorption in 400-500 nm and strong absorption in 200- 400 nm. Previous spectroscopic studies7c of [Cu3(µ2-dppm)3(µ2-SR)(µ3X)] ( R=alkyl or aryl, X=SR or Cl) demonstrate that the ligand (RS-)-to-metal(Cu)-chargetransfer (LMCT) absorption extends from 290 nm to 400 nm. Possibly, the 400-500nm absorption of 2.1 and 2.2• PF6 is part of a LMCT (S-Cu) transition which overlaps with the intraligand absorption. 43 2.0x10 1.8x10 -1 1.4x10 Extinction Coefficient (M .cm ) -1 1.6x10 5 1.2x10 1.0x10 8.0x10 6.0x10 4.0x10 2.0x10 0.0 200 300 400 500 Wavelength (nm) Figure 2.6 UV-vis spectrum of compound 2.1 (C = 1.83×10-5 M) in CH3CN at room temperature -1 -1 Extinction Coefficient (M .cm ) 7x10 6x10 5x10 4x10 3x10 2x10 1x10 200 300 400 500 Wavelength (nm) Figure 2.7 UV-vis spectrum of compound 2.2• PF6 (C = 4.71×10-5 M) in CH3CN at room temperature 44 Photoexcitation of degassed CH3CN solution of NS2 (Figure 2.8), the complexes 2.1 (Figure 2.9) and 2.2• PF6 (Figure 2.10) at 380 nm gives emissions maximized at 410 nm, 486 nm and 489 nm, respectively. The 410 nm emission of NS2 is attributable to 1(nπ*) fluorescence. Poorly resolved vibronic structures with spacing of ~1100 cm-1 are seen in the 486 nm and 488 nm emissions of the complexes. The emissions are tentatively assigned to the spin forbidden (nπ*) phosphorescence on the basis of the large Stokes shift between the emission and the absorption. Close inspection of the emission spectra of the complexes reveals a weak emission band around 620 nm whose intensities increase as the excitation wavelength is changed from 380 nm to 450 nm. Notable, Emission of similar energy, which are assigned to 3LMCT excited state,7 have been widely observed polynuclear CuI-thiolates such as [Cu3(µ2-dppm)3(µ2-SR)(µ3-X)]+ 7c (λ = 610 nm) and [Cu(SC6H4-2-CH2NMe2)]2 (λ=610nm).7f Accordingly, the 620 nm luminescence of the present complexes could arise from a 3LMCT (S→Cu) excited state. 20 18 Emission Intensity(A.U.) 16 14 12 10 350 375 400 425 450 475 500 Wavelength(nm) Figure 2.8 Emission spectrum of NS2, Solvent: CH3CN, T = 298 K, excitation wavelength=300 nm, excitation and emission slit widths=3/3 nm. 45 conformed by elemental analyses, FEB, ESI mass spectrometry and 1H and 31 P NMR Spectroscopy. In complex 2.5, Except that two dithiolate ligands acted as tetradentate [η2(µ2-S,µ2-S)] ligand with six Au atoms, deprotonation of the bis-(dipheny1phosphino)methane also occurs, where the coordination of gold takes place through the carbon atom of bis(diphenylphosphino)methanide [Ph2PCHPPh2]- (obtained from deprotonation of dppm) which has also been widely used in the synthesis of polynuclear complexes.33 Figure 2.20 ORTEP diagram of 2.5. Thermal ellipsoid are drawn with 50% probability. All the hydrogen atoms, phenyl rings, anions and solvent molecule are omitted for clarity. The structure of the complex of 2.5 in the solid state was determined by X-ray crystallography (Figure 2.20). The cation in complex 2.5 is composed of two Au4dppm(Ph2PCHPPh2) units linked together by two NS2. From the X-ray structure, we can see one chair-like hexagon along C2. Au(1)-Au(2)=3.033 Å, Au(2)-S(1)=2.842(5) Å, S(1)Au(1A)=2.352(5) Å, S(1)-Au(2)-Au(1)=131.86 ˚, S(1A)-Au(1)-Au(2)=100.05 ˚ and Au(2A)S(1A)-Au(1)=112.62(18) ˚ (Figure 2.20). This hexagon includes two short Au-Au bonds and four different S-Au bonds as sides. Compared with other Au-S bond (the normal Au-µ 2-S is 56 about 2.3 Å21), S1 has quit different value of bond length with Au(1) and Au(2) and the latter shows a weak interaction. Such long Au(2)-S(1) bond is existed in Au2(3,4-S2C6H3CH3)(PPh3)2 (Au-S=2.714(3) Å),21 Au2(µ-MNT)(PPh3)2 (Au-S=2.811(3) Å).21 Au-P bonds range from 2.245(5) Å to 2.255(5) Å which is typical in gold phosphine complex.19 The angles, S(1)-Au(1A)P(1A)=169.5(2) °, S(2)-Au(2)-P(2)=168.33(19) °, S(2)-Au(4)-P(4)=164.9(2) ° and C(11)-Au(3)P(3)=170.7(6) °, are distorted by the linear geometry, are not uncommon.28 Two Au44+ tetrahedron cores are connected by two NS22- ligand. In the Au44+ unit, The distance separately is 3.033 Å (Au(1)-Au(2)), 3.076 Å (Au(2)-Au(4)), 3.398 Å (Au(1)-Au(4)), 3.653 Å (Au(3)-Au(4)) and 3.720Å (Au(2)-Au(3)). The distance of Au(1) to Au(3) is 4.156 Å. The Au-Au bond is quite weak when it closes to the van der waii radii (3.6 Å) though it could be attractive at such distance.25 If ignored the Au-Au interaction, the core is a 12-number ring formed by Au, P, and S atoms. The naphthalene ring is slightly curved with dihedral angle of 10.3 ° between the two lateral benzene rings. The torsion angle of two C-S bonds of one NS2 is 24.8 °. Between phenyl ring and naphthalene ring has offset π-π stacking with the distance shorter than 3.6 Å. When compared with S(1) and S(2) on one NS22-, we find the Au(1)-S(1)-Au(2) Å (112.62 ˚) which is surprising larger than the standard di(gold)sulfonium salt which does not associate interligomers and the Au(4)-S(2)-Au(2) is 81.67 ˚. The distance Au(2)-Au(3) is 3.07 Å which is recognized as existence strong aurophiclic interaction. Au(3) is linked with C(11) and C(11) is negative charged carbon. Au(3)-C(11) (2.1089 Å), which is similar to the common Au-C bond.26 Table 2.6 selected bond length (Å) and angles (deg) for the compound 2.5 Bond Lengths Au(1)-P(1) Au(1)-S(1)A Au(1)-Au(2) Au(3)-C(11) Au( 2)-S(1) Au(2)-Au(4) Au(2)-S(2) Au(2)-P(2) Au(4)-P(4) S(1)-C(1) Au(4)-P(4) 2.250(6) 2.321(6) 3.0332(12) 2.109(18) 2.842(5) 3.0763(11) 2.355(5) 2.255(6) 2.250(5) 1.76(2) 2.245(5) Bond angles P(1)-Au(1)-S(1A) P(1)-Au(1)-Au(2) P(2)-Au(2)-S(1) S(2)-Au(2)-S(1) S(2)-Au(2)-P(2) P(4)-Au(4)-S(2) Au(4)-S(2)-Au(2) C(11)-Au(3)-P(3) C(2)-C(1)-C(10) S(1)A-Au(1)-Au(2) P(2)-Au(2)-Au(1) 169.5(2) 89.36(15) 112.96(18) 77.29(17) 168.33(19) 164.9(2) 81.67(19) 170.7(6) 118(2) 100.95(14) 88.73(15) 57 The 31P{1H}NMR spectrum of 2.5 at ambient temperature shows one singlet peak at 29.1 ppm, two doublets at 33.2 ppm (2JP,P=73.2 Hz), 23.3 ppm (2JP,P = 73.2 Hz). This indicates the presence of three different phosphorus environments. From the X-ray structure, P(1) and P(2) belong to bis(diphenylphosphino)methane and P(3) and P(4) belong to bis(diphenylphosphino)methanide. The distance of P(3)- P(4) is 3.06 Å compared with 3.02 Å for P(1)-P(2). P(3) and P(4) have same chemical shift at 29.1 ppm although they are not strictly equivalent. However, P(1) and P(2) connect with Csp3(Au), though there are no apparent difference in the P-C bond length for four P atoms. The observation of a two–spin AB pattern is in line with result predicted when the difference in the chemical shifts have the same order of magnitude as coupling constant 2JP,P.23 The ESI MS spectrum shows the molecular peak at m/z= 1746 (M2+, 100%), 1550.2 1.6x10 1.4x10 1.2x10 1.0x10 8.0x10 6.0x10 4.0x10 2.0x10 -1 -1 Extinction Coefficient (M .cm ) (M2+-dppm, 62%) is assigned to one dppm lost in the molecule. and 1358.2 (M2+-2dppm 16%). 0.0 250 300 350 400 450 500 Wavelength (nm) Figure 2.21 UV-vis spectrum of compound 2.5 (C = 2.49×10-5 M) in CH2Cl2 at room temperature Like other Au complexes, 2.5 also show photophysical and photochemical properties. 350 nm (ε = 1.5×104 M-1cm-1) of 2.5 (Figure 2.21) is assigned to intraligand n(S)→π* 58 transitions. The electronic absorption spectrum in CH2Cl2 show moderate absorption at 400 nm (ε = 4500 M-1cm-1) and strong absorption in 200-400 nm. Since NS2 does not absorb between 270-310 nm and beyond 400 nm, the (Au4S2)2 spectroscopic studies demonstrated that the absorption at 400 nm which was absent in Au2(dppm)2(ClO4)227 is likely to originate from a ligand–to-metal charge transfer (LMCT) transition modified by an Au-Au interaction (LMMCT: S→Au). In Au6{µ-Ph2PN(p-CH3C6H4)PPh2}3(µ3-S)2](ClO4)2, has similar absorption in CH2Cl2, have two absorption shoulds and a low-energy absorption band at 264 nm (ε = 83283 M-1cm-1), 304 nm (ε = 4290 M-1cm-1) and 346 nm (ε=6320 M-1cm-1). The low energy band at 346 nm is likely to originate from ligand-to-metal charge transfer transition modified by Au•••Au interactions (LMMCT: S→Au).28 The intense absorption λ < 250 nm is assigned to a dppm intraligand transition.29 Photoexcitation of aerated Au(I) complex 2.5 in CH3CN at 340 nm give moderate emission band at 451 nm.( Figure 2.22). The broad 451nm emission of 2.5 is assigned to 1(nπ)* of NS2 ligand. 120 Emission Intensity (A.U.) 100 80 60 40 20 400 450 500 550 600 Wavelength (nm) Figure 2.22 Emission spectrum of 2.5, Solvent: degassed CH3CN, T = 298 K. Excited wavelength = 340 nm emission slit widths =5/5 nm. 59 2.2.8 Structure and Electronic Spectroscopy (AuPPh3)2(NS2) (2.6) Au2(PPh3)2(NS2) was synthesized by mixing ClAuPPh3 with NS22- in the ratio of 2:1 in THF for overnight at room temperature. The yield is 46%. The green color crystal was obtained by slowly evaporating diethyl ether into dichloromethane solution. The molecular structure of 2.6 conformed by X-ray diffraction analysis. The structure of the molecular is shown in Figure 2.23. From the data, the molecular is 2-fold symmetry. In this complex, two gold atoms are bridged by one NS2 bonded through the sulfur atoms. The distance of Au(1)-Au(1A) is 7.4242 Å and two gold atoms are on the opposite direction. The coordination of the gold atoms is essentially linear (P(1)-Au(1)–S(1) =176.48 º). The Au-P distances is 2.2565 Ǻ and Au-S bond lengths is 2.2927 Ǻ, which are similar to those found in other gold(I) complexes.27 To avoid the strong repulsion force brought by the huge PPh3 group connected with gold, the ring of naphthalene is a little distorted. The angle of C(6)-C(1)–S(1) is 123.3 º and the C(1)-C(6)-C(1D) is 126.7 º. The torsion angle of S(1A)-C(1D)-C(1)-S(1) is 9.90 º. Au(1A)-S(1A) has the dihedral angle with naphthalene ring of 34 °. Figure 2.23 The x-ray structure of compound 2.6. Thermal ellipsoid are drawn with 50% probability. All the hydrogen atoms are omitted for clearity. 60 Table 2.7 selected bond length (Å) and angles (deg) for the compound 2.6 Bond Lengths Au(1)-P(1) Au(1)-S(1) S(1)-C(1) P(1)-C(1A) P(1)-C(1B) P(1)-C(1C) C(1)-C(2) C(1)-C(6) 2.2565(7) 2.2227(7) 1.778(3) 1.804(3) 1.814(3) 1.818(3) 1.381(4) 1.450(3) Bond angles P(1)-Au(1)-S(1) C(1)-S(1)-Au(1) C(1A)-P(1)-C(1B) C(1A)-P(1)-C(1C) C(1B)-P(1)-C(1C) C(1A)-P(1)-Au(1) C(1B)-P(1)-Au(1) C(1C)-P(1)-Au(1) C(6)-C(1)-S(1) 176.48(3) 104.76(8) 108.23(13) 104.36(12) 105.17(13) 115.00(9) 111.17(9) 112.24(8) 123.3(2) Fugure 2.24 shows the crystal structure of the complex down the c axis. The phenyl rings participate in significant intermolecular C–H•••S interactions, with weak sulfur-hydrogen contacts [S1•••H=2.929 Å] between the neighboring molecular to form a chain along the c axis compared with 2.3 with a short intermolecular C–H•••S interactions [S•••H=2.728 Å]. In complex [NBu4]Au(tpdt)2(tpdt=3,4-thiophenedithiolate)14, the channels between the zig-zag chains of the anions are occupied by tetra-n-butyl ammonium (TBA) cations that are strongly held by a charge-assisted C-Hδ+•••Sδ+ hydrogen bond system with H•••S distances that range from 2.856 to 3.028 Å. The nearest gold-gold distance is 7.4242 Å. Table 2.7 gives some bond and angle data of compound 2.6. Figure 2.24 crystal structure showing hydrogen bonding and packing of compound 2.6 The mass spectrum (FAB+) for the neutral complexes Au2(PPh3)2(S2-naphalene) show she molecular peaks at m/z=1106 (M+, 5%). In addition peak corresponding to [M]+ is present 61 and the most intense peak arise from a specials [M+Au(PPh3)]+ (1566.9, 100%), There is only one single peak in 31 P NMR with chemical shift of 35.1 ppm for the two-fold symmetrical structure. Complex 2.6 also shows rich photophysical and photochemical properties. The electronic absorption of 2.6 in CH2Cl2 have one strong peak at 370 nm (ε = 1.09×104 M-1cm-1), which is assigned to intraligand n(S)-π* transitions. The strong peak at 244 nm (ε = 3.78×104 M-1cm-1) is intense π→π* transition. Compared with NS2, it has lower energy. Due to the same reason, the absorption of 2.6 of 244 nm assigns to π→π* transition. Irradiating aerated or degassed solution of the complexes leads to luminescence at 481 nm which is assigned to 1(nπ)* of NS2 ligand. Similar emissions have been observed in other complexes with NS2 ligand. AuPPh3+ has emission at 512 nm, so the broad peak of 2.5 also contains emission of dp triplet state.31 4.0x10 -1 -1 Extinction Coefficient (M .cm ) 3.5x10 3.0x10 2.5x10 2.0x10 1.5x10 1.0x10 5.0x10 0.0 250 300 350 400 450 Wavelength (nm) Figure 2.25 UV-vis spectrum of compound 2.6 (C = 8.39×10-5 M) in CH2Cl2 at room temperature 62 120 Emission Intensity (A.U.) 100 80 60 40 20 400 420 440 460 480 500 520 540 560 580 600 Wavelength (nm) Figure 2.26 Emission spectrum of 2.6, Solvent: degassed CH2Cl2, T = 298 K. Excited wavelength=280 nm Emission slit widths= 10/10 nm. 63 2.3.1 Experimental section General Method: All of the syntheses were carried out in N2 atmosphere with standard Schlenck techniques. 1,8-diiodonaphthalene, [Cu2(µ-dppm)2(MeCN)2](PF6)2, Au2(µ2-dppm)2(ClO4)2, Au(PPh3)Cl, 9,10-Bis(diphenylphosphino)anthracene (PAnP) and Au2(µ-PAnP)Cl2 were synthesized according to the reported methods.1, 2, 18b, 32 KAuCl4 was purchased from Oxkem. PPh3 was purchased from Acros Organics Company. The solvents used were purified according to the literature procedures. Physical measurements: The UV/Vis absorption and emission spectra of the complexes were recorded on a Hewlett-Packard HP8452A diode array spectrophotometer and a Perkin-Elmer LS50D fluorescence spectrophotometer, respectively. 1H and 31P{1H} NMR spectra were recorded at on either a Bruker ACF 300 spectrometer or a Bruker AMX500 spectrometer. All chemical shifts are quoted relative to SiMe4 (1H) or H3PO4 (31P). Variable temperature spectra were obtained by using a Bruker variable temperature unit B-VT2000 to control the probe temperature. The sample temperature is considered accurate to ±1ºC. Elemental analyses of the complexes were carried out in the microanalysis laboratory in the department of chemistry, the National University of Singapore. Synthesis of naphtho[1, 8-cd]-1,2-dithiole: A solution of BuLi in hexane (62.5 mL, 100 mmol) was added over 15 min. to a solution of 1,8-diiodonaphthalene (18.9 g, 50 mmol) in THF (200 mL) at -78ºC under nitrogen. After stirring hours, elemental sulfur (3.2 g, 100 mmol) was added and stirred 45 by which time all the sulfur had dissolved. The mixture was quenched by addition of saturated ammonium chloride (50 mL) and warmed in room temperature. Air was passed through this mixture for hours. Then it was diluted with CH2Cl2 (300 mL) and the organic layer was separated washed with water (100 mL), saturated NaCl (100 mL) and dried by MgSO4, evaporation of solvents gave a crude product (10 g), which was purified by chromatography on a silica gel column(300 g) with hexane to give naphtho[1, 8-cd]-1,2-dithiole 3.15 g. Yield: 33.2%; 1H NMR (300 MHz, CDCl3, δ/ppm): 7.35(d, 3JH, H= 7.2 Hz, 2H, naphthane H2, H7 ), 7.27(dd, 3JH, H= 3JH, H= 7.2 Hz, 2H, naphthane H3, H6), 7.15(d, 3JH, H= 7.2Hz, 2H, naphthane H4, H5); EI MS: m/z:190 (M+,, 100%). 64 Synthesis of 1,8-naphthlenedithiol NS2H2: to a solution of naphtho[1,8-cd]-1,2-dithiole (0.19 g, mmol) in dry THF (10 mL), was added NaBH4 (0.0756 g, mmol). The mixture was stirred in r.t. for 30 min, during which time the color of the solution changed from orange red to colorless. Excess NaBH4 was quenched by 10% hydrochloric acid (20 mL) and the product was extracted with CHCl3. The organic solution was dried by MgSO4 then evaporated to get a crude product (0.19 g) and can use for synthesis without further purification. Yield: 95 %. Synthesis of [Cu4(µ2-dppm)3(µ2- µ2-NS2)( µ2- µ4-NS2)] 2.1: To a solution of naphtha[1,8-cd]1,2-dithiole (0.10 g, 0.5 mmol) in THF (60mL) was added sodium borohydride (0.024 g, 0.5 mmol). The mixture was stirred for 30 min, during which time the color of the solution changed from orange red to colorless. The solution was cannulated to a schlenck flask containing [Cu2(dppm)2(MeCN)2](PF6)2 (0.590 g, 0.5 mmol). After stirring 40 mins, the solution was filtered and the filtrate was evaporated to mL and treated with excess diethyl ether to precipitate the product as orange solid. Orange crystal was obtained from slow diffusion of diethyl ether into a CH2Cl2/MeOH (1:1). Yield: 50%. (C95H78Cu4P6S4)• 0.5CH2Cl2: Calcd (%) for C, 62.65; H, 4.35. S, 7.01; found (%); C, 62.24; H, 4.25; S, 6.57. 1H NMR(500 MHz, CD2Cl2 δ/ppm): 9.20-6.14(m, 72H, Ph and naphthalene protons), 3.18-1.13(m, 6H, CH2 in dppm); 31 P{1H}NMR(121.5 MHz, CD2Cl2, δ/ppm): -8.75(d, 2P), -12.05(m, 2P), -22.04(d, 2P). ESI MS: m/z: 1785([M+1]+, 60%). Synthesis of [Cu5(µ2-dppm)4(µ3-µ3-NS2)2] (PF6) 2.2: [Cu2(dppm)2(MeCN)2](PF6)2 (0.590 g, mmol), NaBH4 ( 0.02 g, 0.5 mmol) and naphtho[1, 8-cd]-1,2-dithiole (0.1 g, 0.5 mmol) was reacted similar to complexes 2.1. Reaction time is hours. Yellow crystals were obtained from slow diffusion of diethyl ether into a CH2Cl2/MeOH (1:1) solution of the compounds. Yield; 38%; C120H100Cu5P9S4: Calcd (%). C, 60.54; H, 4.20; S, 5.29 Found (%); C, 60.15; H, 4.07; S, 5.32. 1H NMR(500 MHz, CD2Cl2 δ/ppm): 8.08-6.26(m, 92H, Ph and naphthalene H), 2.60-3.10 (m, 8H, CH2); 31P{1H}NMR(121.5M Hz, CD2Cl2, δ/ppm): -13.0(s); FAB MS: m/z: 2236 ([M-PF6+1]+, ), -145 (PF6-). Synthesis of (Et4N)Au(NS2)2 2.3: 1,8-napthalenedithiol (0.1 g, 0.53 mmol) and 0.16 mL Et3N (1.06 mmol) was added in THF (30 mL) in schlenck flask and stirred for 5min. In the colorless 65 solution, KAuCl4 (0.1 g, 0.26 mmol) was added and stirred for another 30 min. Then 0.2 g Et4NCl was added in red solution and stirred for a further 30 min. the red solution was concentrated to dryness and CH2Cl2 was used to extract the red product from water. CH2Cl2 portion was reduced to mL. Addition of excess diethyl ether to the solution precipitated the product as red solids. Red crystal was obtained by slow diffusion of hexane into CH2Cl2 solution. Yield: 0.0244 g (13%). C28H32AuS4N: Calcd (%): C, 16.26; H, 3.82; Found (%): C, 16.57; H, 3.88. 1H NMR (300 M Hz, CDCl3, δ/ppm): 7.55(d, JH, H= 7.2 Hz, 4H, naphthane H2, H7), 7.26 (d, JH, H= 7.2 Hz ,4H), 6.78 (dd, JH, H= 7.2 Hz, 4H). ESI MS: m/z: -577 ([Au(NS2)2 +1], 100%). Synthesis of Au4(NS2)2(PAnP)2 2.4: In the mixture of 1,8-naphthalenedithiol and drops of Et3N in 30 mL methanol, PAnP(AuCl)2 (0.18 g, 0.18 mmol) was added into the colorless solution and stirred for 24 hours. The color changed to orange. All the solvent was removed in vacuum and CHCl3 was added to dissolve the entire solid. The solution was concentrated to mL and excess diethyl ether was added to form red participate. Red crystal was obtained by diffusion of hexane into the CHCl3 solution. Yield: 0.20(90%). C96H68Au4S4P4•CH2Cl2: Calcd (%): C, 49.96; H, 3.01. Found (%): C, 49.77; H, 2.63 1H NMR (300 M Hz, CDCl3, δ/ppm): 8.12 (m, 4H), 7.83 (d, JH, H= 7.2Hz, 31 2H), 7.55(m 10H), 7.32(m. 10H), 7.05(m. 2H), 6.65(m, 2H). P(CDCl3, 121.5M Hz, δ/ppm): 31.3 ppm(s). FAB MS m/z: 2267([M+1]+, 22%). Synthesis of [Au8(dppm)2(Ph2PCHPPh2)2(µ2-µ3-NS2)]2(ClO4)2 2.5 : 1.8- napthalenedithiolate(NS22-) was prepared in situ by reducing naptho[1,8-cd]-1.2-dithole(NS2) with NaBH4 in refluxing THF. Reacting NS22- and molar equivalent of Au2(µ2-dppm)2(ClO4)2 at room temperature of 20 hours gave 2.5 as major product. Recrystallization from dichloromethane/diethyl ether afforded 2.5 as pale yellow crystals. Yield: 0.20 g (90%) C120H98Au8Cl2O8P8S4•2CH2Cl2: Calcd(%): C, 49.96; H, 3.01. Found(%): C, 39.12; H, 2.80. 1H NMR (300M Hz, CD3CN, δ/ppm): 8.01-6.45(m, 94H), 4.46 (m, 1H, CH of dppm), 3.42(m. 2H, CH2 of dppm), 3.24(m. 1H, CH of dppm), 3.14 (m, 2H, CH2 of dppm), 31P(121.5 M Hz, CD3CN, δ/ppm): 29.1 ppm(s, 2P), 33.2(d, J=72.8 Hz, 1P), 23.3(d, J = 72.8 Hz, 1P). ESI MS: 1746([M2ClO4+1]2+,100%), 1550 ([M-2ClO4-dppm+1]2+,62%), -99(ClO4-, 100%). 66 Synthesis of (AuPPh3)2(NS2) 2.6: To a solution of naphtho[1, 8-cd]-1,2-dithiole (0.134 g, 0. mmol) in THF (30 mL), lithium aluminium hydride (0.027 g, 0.7 mmol) was added and the mixture was refluxed for 30 min, during which time the color of the solution changed from orange red to colorless. After cooling to r.t., excess lithium aluminum hydride was filtered under nitrogen. The colorless solution was transferred directly to the Au(PPh3)Cl (0.651 g, 1.3 mmol) in THF. The color was changed from white to dark purple. After stirring overnight, the solution was filtered and the filtrate was evaporated to mL and treated with excess diethyl ether, leading to brown precipitation. Brown crystal was obtained by slow evaporation diethyl ether in the dichloromethane solution. Yield: 44.9%. C46H36Au2P2S2: Calcd(%): C, 48.39; H, 3.74. Found(%): C, 48.96; H, 3.09. 1H NMR(500 M Hz, CDCl3, δ/ppm): 7.6(dd, JH, H= 8.3Hz, J= 0.95 Hz, 2H, H2,7 of naphthalene), 7.45-7.5(m, 30H), 7.42(dd, 2H, JH, H= 8.3 Hz, J= 0.95Hz H3,6 of naphthalene) 7.25(dd, 2H, JH, H= 8.3 Hz, J=0.95Hz, H4,5 of naphthalene); 31P{1H} NMR(202.5 MHz, CDCl3, δ/ppm): δ=35.6(s); FAB MS: m/z: 1108.9 ([ M+1]+, 5%)1566 ([M+Au(PPh3)]+, 100%). 67 Reference 1. Yui, K; Aso, Y.; Otsubo, T.; Ogura, F. Chem. Lett. 1986. 551. 2. Diez. J.; Gamasa. M. P.; Gimeno. J.; Tiripicchio. A.; Camellini, M. T. J. Chem. Soc., Dalton. Trans. 1987, 1275. 3. Bera, J. K.; Nethaji, M.; Samuelson, A.G. Inorg, Chem. 1999, 38, 218. 4. a)Dance, I. G. J. Chem. 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Organometallics 1993, 12, 3984. 71 [...]... compound 2. 4 along c axis Table 2. 5 selected bond length (Å) and angles (deg) for the compound 2. 4 Bond Lengths Au(1)-P(1) 2. 254 (2) Au(1)-S(1) 2. 321 (2) Au(1)-Au (2) 3.1479(5) Au (2) -P (2) 2. 239 (2) Au (2) -S (2) 2. 314(3) Au (2) -S(1) 2. 6 42( 2) P(1)-C(14) 1.831(8) P (2) -C (21 ) 1. 825 (8) S(1)-C(1) 1.781(8) S (2) -C(9) 1.767(9) Bond angles P(1)-Au(1)-S(1) P(1)-Au(1)-Au (2) S(1)-Au(1)-Au (2) P (2) -Au (2) -S (2) P (2) -Au (2) -S(1) S (2) -Au (2) -S(1)... bond lengths 2. 3019 -2. 3031 Å observed in 2. 3 are slightly shorter than those in other gold(III) derivation containing dithiolate ligand For example [Au(S2C2B10H10 )2] - (Au-S bond distance is 47 2. 321 (2) Å), 11a [N(PPh3 )2] [Au(C3S5 )2] (Au-S is in the range from 2. 321 (2) to 2. 326 (2) Å),11b [PPh3Cl][Au{S2C2(CF3 )2} 2] (Au-S is 2. 288 Å) and [Au(PEt3 )2] [Au(1 ,2- S2C6H4 )2] 12 (Au-S bond length is 2. 305 Å) Cationic... (%); C, 62. 24; H, 4 .25 ; S, 6.57 1H NMR(500 MHz, CD2Cl2 δ/ppm): 9 .20 -6.14(m, 72H, Ph and naphthalene protons), 3.18-1.13(m, 6H, CH2 in dppm); 31 P{1H}NMR( 121 .5 MHz, CD2Cl2, δ/ppm): -8.75(d, 2P), - 12. 05(m, 2P), -22 .04(d, 2P) ESI MS: m/z: 1785([M+1]+, 60%) Synthesis of [Cu5( 2- dppm)4(µ3-µ3-NS2 )2] (PF6) 2. 2: [Cu2(dppm )2( MeCN )2] (PF6 )2 (0.590 g, 5 mmol), NaBH4 ( 0. 02 g, 0.5 mmol) and naphtho[1, 8-cd]-1 ,2- dithiole... m/z: 22 67([M+1]+, 22 %) Synthesis of [Au8(dppm )2( Ph2PCHPPh2 )2( 2- µ3-NS2) ]2( ClO4 )2 2.5 : 1.8- napthalenedithiolate(NS 22- ) was prepared in situ by reducing naptho[1,8-cd]-1 .2- dithole(NS2) with NaBH4 in refluxing THF Reacting NS 22- and 2 molar equivalent of Au2( 2- dppm )2( ClO4 )2 at room temperature of 20 hours gave 2. 5 as major product Recrystallization from dichloromethane/diethyl ether afforded 2. 5 as... 2. 19 Emission spectrum of 2. 4 Solvent: CHCl3 (degassed), T = 29 8 K Excited wavelength = 26 0 nm excitation and emission slit widths 5/5 nm 2. 2.7 Structure and Electronic Spectroscopy [Au8(dppm) 2( Ph2PCHPPh2 )2( 2- µ3- NS2) ]2( ClO4 )2 (2. 5) 1.8-Napthalenedithiolate(NS 22- )2a was prepared in situ by reducing naptho[1,8-cd]-1.2dithole (NS2) with NaBH4 in refluxing THF Reacting NS 22- and 2 molar equiv of Au2(µ2dppm )2( ClO4 )2. .. C(11) and C(11) is negative charged carbon Au(3)-C(11) (2. 1089 Å), which is similar to the common Au-C bond .26 Table 2. 6 selected bond length (Å) and angles (deg) for the compound 2. 5 Bond Lengths Au(1)-P(1) Au(1)-S(1)A Au(1)-Au (2) Au(3)-C(11) Au( 2) -S(1) Au (2) -Au(4) Au (2) -S (2) Au (2) -P (2) Au(4)-P(4) S(1)-C(1) Au(4)-P(4) 2. 250(6) 2. 321 (6) 3.03 32( 12) 2. 109(18) 2. 8 42( 5) 3.0763(11) 2. 355(5) 2. 255(6) 2. 250(5)... 1.76 (2) 2. 245(5) Bond angles P(1)-Au(1)-S(1A) P(1)-Au(1)-Au (2) P (2) -Au (2) -S(1) S (2) -Au (2) -S(1) S (2) -Au (2) -P (2) P(4)-Au(4)-S (2) Au(4)-S (2) -Au (2) C(11)-Au(3)-P(3) C (2) -C(1)-C(10) S(1)A-Au(1)-Au (2) P (2) -Au (2) -Au(1) 169.5 (2) 89.36(15) 1 12. 96(18) 77 .29 (17) 168.33(19) 164.9 (2) 81.67(19) 170.7(6) 118 (2) 100.95(14) 88.73(15) 57 The 31P{1H}NMR spectrum of 2. 5 at ambient temperature shows one singlet peak at 29 .1... Yield: 0 .20 g (90%) C 120 H98Au8Cl2O8P8S4•2CH2Cl2: Calcd(%): C, 49.96; H, 3.01 Found(%): C, 39. 12; H, 2. 80 1H NMR (300M Hz, CD3CN, δ/ppm): 8.01-6.45(m, 94H), 4.46 (m, 1H, CH of dppm), 3. 42( m 2H, CH2 of dppm), 3 .24 (m 1H, CH of dppm), 3.14 (m, 2H, CH2 of dppm), 31P( 121 .5 M Hz, CD3CN, δ/ppm): 29 .1 ppm(s, 2P), 33 .2( d, J= 72. 8 Hz, 1P), 23 .3(d, J = 72. 8 Hz, 1P) ESI MS: 1746([M2ClO4+1 ]2+ ,100%), 1550 ([M-2ClO4-dppm+1 ]2+ , 62% ),... (Au-S =2. 714(3) Å) ,21 Au2(µ-MNT)(PPh3 )2 (Au-S =2. 811(3) Å) .21 Au-P bonds range from 2. 245(5) Å to 2. 255(5) Å which is typical in gold phosphine complex.19 The angles, S(1)-Au(1A)P(1A)=169.5 (2) °, S (2) -Au (2) -P (2) =168.33(19) °, S (2) -Au(4)-P(4)=164.9 (2) ° and C(11)-Au(3)P(3)=170.7(6) °, are distorted by the linear geometry, are not uncommon .28 Two Au44+ tetrahedron cores are connected by two NS 22- ligand In the... P (2) -Au (2) -S (2) P (2) -Au (2) -S(1) S (2) -Au (2) -S(1) P (2) -Au (2) -Au(1) S (2) -Au (2) -Au(1) S(1)-Au (2) -Au(1) Au(1)-S(1)-Au (2) 74.39(7) 127 .90(5) 55.30(5) 150.00(8) 119.13(7) 90.18(7) 118.33(6) 76. 32( 6) 46 .25 (5) 78.45(6) 53 The FAB mass spectrum shows the molecular peak at m/z= 22 67 (M+1 ,23 %), 20 69 ( 62% ) is assigned to one NS2 lost in the molecule and [(AuPAnPAu )2( NS2)S] at 21 05 (76%) The 31P{1H} NMR show a singlet . Cu(4)-Cu(1) 2. 323 3(13) 2. 51 82( 13) 2. 24 32( 13) 2. 24 82( 13) 2. 3539(13) 2. 47 02( 14) 2. 3103(13) 2. 5685(13) 2. 2 721 (13) 2. 2781(13) 2. 2 826 (14) 2. 2844(13) 2. 7 520 (8) 2. 74 72( 8) 2. 7 525 (8) 2. 7897(8). Cu(1)-P (2) Cu(3)-P(5) Cu(1)-Cu( 2) Cu (2) -Cu(3 ) Cu(3)-Cu(4 ) Cu(4)-Cu(1 ) 2. 378 (2) 2. 357 (2) 2. 3 92( 2) 2. 3 92( 2) 2. 448 (2) 2. 419 (2) 2. 356 (2) 2. 341 (2) 2. 284 (2) 2. 2 72( 2) 2. 189 (2) 3.074 (2) . 2. 254 (2) 2. 321 (2) 3.1479(5) 2. 239 (2) 2. 314(3) 2. 6 42( 2) 1.831(8) 1. 825 (8) 1.781(8) 1.767(9) P(1)-Au(1)-S(1) P(1)-Au(1)-Au (2) S(1)-Au(1)-Au (2) P (2) -Au (2) -S (2) P (2) -Au (2) -S(1) S (2) -Au (2) -S(1)