Vapochromic and mechanochromic tetrahedral gold(I) complexes based on the 1,2-bis(diphenylphosphino)benzene ligand

Tetrahedral gold(I) complexes containing the diphosphane ligand (dppb=1,2-bis(diphenylphosphino)benzene), [Au(dppb)(2)]X [X=Cl (1), Br (2), I (3), NO(3) (4), BF(4) (5), PF(6) (6), B(C(6)H(4)F-4)(4) (7)], and the ethanol and methanol adducts of complex 4, 8, and 9, were prepared to analyze their unique photophysical properties. These complexes are classified into two categories on the basis of their crystal structures. In Category I, the complexes (1-5) have relatively-small counter anions and two dppb ligands are symmetrically coordinated to the central Au(I) atom, and display an intense blue phosphorescence. Alternatively, the complexes (6-9) in Category II have large counter anions and two dppb ligands asymmetrically coordinated to Au(I) atom, and display a yellow or yellow orange phosphorescence. The difference in the phosphorescence color of the complexes between the Category I and II is ascribed to the change in the structure of the cationic moiety in the complex. According to DFT calculations, the symmetry reduction caused by the large counter anion of the complex in Category II gives the destabilization of HOMO (σ*) levels, leading to the red-shift of the emission peak. We have demonstrated that the symmetry reductions are responsible for the phosphorescence color alteration caused by external stimuli (volatile organic compounds and mechanical grinding).     

Highly photoluminescent nanocrystals based on a gold(I) complex and their electrophoretic patterning

The fabrication of nanocrystals (NCs) composed of the cationic Au(I) complex was demonstrated by the reprecipitation method in which the colloidal solution of the NCs showed brilliant green phosphorescence with a quantum yield of 83% in n-hexane. Characterization of the prepared NCs was performed by transmission electron microscopy observation and elemental analysis with energy-dispersive X-ray spectroscopy. The obtained Au(I) NCs were particles of random shapes with a diameter of 200-400 nm. The selected-area electron diffraction and X-ray diffraction measurements showed the characteristic diffraction patterns attributable to the crystal structure of the bulk crystal of the Au(I) complex. A similar method was performed with a different counteranion, leading to a colloidal solution of the microcrystals (MCs) with brilliant yellow phosphorescence and a quantum yield of 26% in n-hexane. Luminescence patterning of the NCs and MCs was also achieved successfully by electrophoretic deposition onto an indium tin oxide (ITO)-coated glass substrate, resulting in characteristic luminescence patterns on the ITO substrates with relatively high photoluminescence quantum yields.     

Intensely luminescent homoleptic alkynyl decanuclear gold(I) clusters and their cationic octanuclear phosphine derivatives

Treatment of Au(SC(4)H(8))Cl with a stoichiometric amount of hydroxyaliphatic alkyne in the presence of NEt(3) results in high-yield self-assembly of homoleptic clusters (AuC(2)R)(10) (R = 9-fluorenol (1), diphenylmethanol (2), 2,6-dimethyl-4-heptanol (3), 3-methyl-2-butanol (4), 4-methyl-2-pentanol (4), 1-cyclohexanol (6), 2-borneol (7)). The molecular compounds contain an unprecedented catenane metal core with two interlocked 5-membered rings. Reactions of the decanuclear clusters 1-7 with gold-diphosphine complex [Au(2)(1,4-PPh(2)-C(6)H(4)-PPh(2))(2)](2+) lead to octanuclear cationic derivatives [Au(8)(C(2)R)(6)(PPh(2)-C(6)H(4)-PPh(2))(2)](2+) (8-14), which consist of planar tetranuclear units {Au(4)(C(2)R)(4)} coupled with two fragments [AuPPh(2)-C(6)H(4)-PPh(2)(AuC(2)R)](+). The titled complexes were characterized by NMR and ESI-MS spectroscopy, and the structures of 1, 13, and 14 were determined by single-crystal X-ray diffraction analysis. The luminescence behavior of both Au(I)(10) and Au(I)(8) families has been studied, revealing efficient room-temperature phosphorescence in solution and in the solid state, with the maximum quantum yield approaching 100% (2 in solution). DFT computational studies showed that in both Au(I)(10) and Au(I)(8) clusters metal-centered Au → Au charge transfer transitions mixed with some π-alkynyl MLCT character play a dominant role in the observed phosphorescence.     

Synthesis, characterization and photophysical properties of PPh2-C2-(C6H4)n-C2-PPh2 based bimetallic Au(I) complexes

A family of the diphosphines PPh(2)C(2)(C(6)H(4))(n)C(2)PPh(2) (n = 0-3), which possess a dialkynyl-arene spacer between the phosphorus atoms, was used for the synthesis of a series of bimetallic gold(I) complexes 1-7. Unlike the corresponding polynuclear Au(i) clusters, which show unique phosphorescence, 1-7 reveal dual emissions consisting of fluorescence and phosphorescence. The results are rationalized, in a semi-quantitative manner, by the trace (1-3) to zero (4-7) contribution of MLCT varying with the number of conjugated phenylene rings. As a result, unlike typical polynuclear Au(I) clusters with 100% triplet state population, the rate constant of the S(1)→T(1) intersystem crossing is drastically reduced to 10(9) s(-1) (4-7)-10(10) s(-1) (1-3), so that the fluorescence radiative decay rate can compete or even dominates. The drastic O(2) quenching of phosphorescence demonstrates the unprotected nature of the emission chromophores in 1-7, as opposed to the well protected, O(2) independent phosphorescence in most multimetallic Au(I) clusters.     

Photophysical studies and excited-state structure of a blue phosphorescent gold-thallium complex

The dinuclear complex [[Tl(eta6-toluene)][Au(C6Cl5)2]] (1) displays very intense blue phosphorescence and a rigidochromic behavior in the solid state. The photophysical measurements in a glassy solution display an oligomerization process via metal-metal interactions. Density functional theory calculations show a distortion of the aurate-thallium T shape in the lowest triplet excited state, leading to a triplet metal-to-metal charge-transfer state.     

Controlling the solid-state luminescence of gold(I) <Emphasis Type="Italic">N</Emphasis>-heterocyclic carbene complexes through changes in the structure of molecular aggregates

Thermally stable, solid-state luminescent organic materials are highly desired for the development of practical applications. Herein we synthesized new gold(I) complexes with N-heterocyclic carbene ligands, which have the ability to form strong metal-organic bond. Consequently, their thermochemical stability is enhanced at temperatures around 300 °C. Precise design of the molecular structure of the ligands, with a focus on ensuring low steric hindrance around Au atoms in order to limit disturbances to Au/Au interactions, provided a complex with a densely packed crystal with a shorter intermolecular Au–Au distance (3.17 Å) than the typical distance. In the solid state, this complex exhibited strong aurophilic interactions, which generated intense phosphorescence even in air at room temperature (quantum yield=16%) in spite of absence of any phosphorescence in solution. This behavior is characteristic for solid-state luminescence referred to as aggregation-controlled emission. Furthermore, the gold (I) complex displays capacity for mechano- and vapo-chromism—that is, the ability to change color reversibly in response to the application of external stimuli. We believe that the proposed design framework, which involves controlling thermal stability and luminescence property separately, provides a new opportunity for the development of practical applications using solid-state luminescent organic molecules.     

Theoretical studies on metal-metal interaction and spectroscopic properties of a series of hetero-binuclear d(8)-d(10) complexes containing iridium(i) and gold(i)

The ground and triplet excited state geometries, metal-metal (Ir-Au) attractive interaction, electronic structures, absorptions, and phosphorescence of three d(8)-d(10) Ir(i)-Au(i) complexes [Ir(CO)ClAu(mu-dpm)(2)](-) (1), [Ir(CNCH(3))(2)Au(mu-dpm)(2)](2-) (2), and [Ir(CNCH(3))(3)Au(mu-dpm)(2)](2-) (3) [dpm = bis(diphosphino)methane] were investigated theoretically. Their ground and triplet excited states geometries were fully optimized at the MP2 and UMP2 (6-31G for H/C/N/O atoms, LANL2DZ for Ir/Au/P/Cl) levels, respectively, and the calculated geometries are well consistent with the X-ray results. The calculated results indicated that a weak Ir-Au interaction exists in the ground state of , moreover the interaction of and is strengthened by excitation, on contrast, the Ir-Au attractive interaction of in the excited state becomes little lower than that in the ground state. By adding one more CNMe group on complex , the bond type of HOMO can be changed from sigma*[d(z(2))(Ir/Au)] to sigma[d(z(2))(Ir/Au)]. Under the TD-DFT level with PCM model, the absorptions and phosphorescence of were calculated based on the optimized ground and excited states geometries, respectively. The lowest-lying absorptions of 1 and 2 are all attributed to sigma*[d(z(2))] --> sigma[p(z)] and that of 3 is assigned to sigma[d(z(2))] --> pi[p(z)] with MC/MMLCT transition characters. The phosphorescence of 1, 2 and 3 and are assigned to sigma[p(z)] --> sigma*[d], sigma[p(z)] --> sigma*[d], and pi[p(z)] --> sigma[d] transitions, respectively. The calculated results also indicated that with the increase of the Ir-Au bond distance both in the ground and the excited state, the absorptions and the emissions are red-shifted correspondingly.     

Metal effect on the supramolecular structure, photophysics, and acid-base character of trinuclear pyrazolato coinage metal complexes

Varying the coinage metal in cyclic trinuclear pyrazolate complexes is found to significantly affect the solid-state packing, photophysics, and acid-base properties. The three isoleptic compounds used in this study are [[3,5-(CF3)2Pz]M]3 with M = Cu, Ag, and Au (i.e., Cu3, Ag3, and Au3, respectively). They form isomorphous crystals and exist as trimers featuring nine-membered M3N6 rings with linear two-coordinate metal sites. On the basis of the M-N distances, the covalent radii of two-coordinate Cu(I), Ag(I), and Au(I) were estimated as 1.11, 1.34, and 1.25 angstroms, respectively. The cyclic [[3,5-(CF3)2Pz]M]3 complexes pack as infinite chains of trimers with a greater number of pairwise intertrimer M...M interactions upon proceeding to heavier coinage metals. However, the intertrimer distances are conspicuously short in Ag3 (3.204 angstroms) versus Au3 (3.885 angstroms) or Cu3 (3.813 angstroms) despite the significantly larger covalent radius of Ag(I). Remarkable luminescence properties are found for the three M3 complexes, as manifested by the appearance of multiple unstructured phosphorescence bands whose colors and lifetimes change qualitatively upon varying the coinage metal and temperature. The multiple emissions are assigned to different phosphorescent excimeric states that exhibit enhanced M...M bonding relative to the ground state. The startling luminescence thermochromic changes in crystals of each compound are related to relaxation between the different phosphorescent excimers. The trend in the lowest energy phosphorescence band follows the relative triplet energy of the three M(I) atomic ions. DFT calculations indicate that [[3,5-(R)2Pz]M]3 trimers with R = H or Me are bases with the relative basicity order Ag < Cu < Au while fluorination (R = CF3) renders even the Au trimer acidic. These predictions were substantiated experimentally by the isolation of the first acid-base adduct, [[Au3]2:toluene]infinity, in which a trinuclear Au(I) complex acts as an acid.     

Observation of a mixed-metal transition in heterobimetallic Au/Ag dicyanide systems

Crystals of the mixed-metal heterobimetallic Au/Ag dicyanide complex, K[AuxAg1-x(CN)2] (x = 0-->1), were obtained by slow evaporation. The mixed-metal complex K[Au0.44Ag0.56(CN)2] crystallizes in a rhombohedral crystal system, space group R. The crystal structure consists of layers of linear chains of Au(CN)2- and Ag(CN)2- ions and K+ ions that connect the layers through the N atoms. The excitation and emission spectra of single crystals of K[AuxAg1-x(CN)2] were recorded at 4.2-180 K using excitation wavelengths between 230 and 260 nm. Two emission bands due to Ag-Au interactions were observed at 343 and 372 nm. Lifetime measurements indicate the shorter-wavelength emission corresponds to fluorescence and the longer-wavelength band is phosphorescence. These new emission bands are not seen in the pure K[Ag(CN)2] or pure K[Au(CN)2] crystals. Extended Hückel calculations show that the LUMO of the mixed-metal system is bonding while the HOMO is antibonding or very weakly bonding. Moreover, excited-state extended Hückel calculations indicate the formation of exciplexes with shorter metal-metal distances and higher metal-metal overlap populations than the corresponding ground-state oligomers. The luminescence is assigned to a mixed-metal transition from a molecular orbital with Au character to a molecular orbital with Ag character.     

Synthesis and characterization of phenanthrylphosphine gold complex: observation of Au-induced blue-green phosphorescence at room temperature

A new 9-diphenylphosphinophenanthrene ligand (9DPP, 1), its oxide (9DPPO, 2), and its gold complex [(AuCl(9DPP)] (3) were synthesized. The Au(I) complex 3 was found to exhibit intense blue-green, room-temperature phosphorescence (Phip = 0.06 and tauT = 22.7 micros) originating in the locally excited triplet of the phenanthrene moiety (3LE) in degassed 2-methyltetrahydrofuran solution. On the assumption that PhiST = 1.0 for 3, the radiative rate constant (kr) in the triplet state is calculated to be 2.6 x 10(3) s(-1). This value is 4 orders of magnitude larger than the radiative rate constant of the triplet phenanthrene (0.26 s(-1)). Thus, the coordinated Au(I) atom is concluded to have a markedly large heavy-atom effect on kr of the phenanthrene chromophore in 3.     

Organic triplet emissions of arylacetylide moieties harnessed through coordination to [Au(PCy(3))]+. Effect of molecular structure upon photoluminescent properties

A family of mono- and binuclear Cy(3)P-supported gold(I) complexes containing various pi-conjugated linear arylacetylide ligands, including the two homologous series (Cy(3)P)Au(Ctbd1;CC(6)H(4))(n)()(-)(1)(Ctbd1;CPh) and (Cy(3)P)Au(Ctbd1;CC(6)H(4))(n)()Ctbd1;CAu(PCy(3)) (n = 1-4), have been prepared. X-ray crystal analyses revealed no intermolecular aurophilic interactions in their crystal lattice. The lowest-energy singlet transitions are predominately intraligand in nature and exhibit both phenyl and acetylenic (1)(pipi) character. Strong photoluminescence is detected in solid and solution states under ambient conditions, with lifetimes in the microsecond regime. For complexes with a single arylacetylide group, only phosphorescence from the arylacetylide (3)(pipi) state is observed. Vibrational spacings in the solid-state emission spectra can be attributed to a combination of phenyl ring deformation and symmetric phenyl ring and Ctbd1;C stretches. Additional delayed-fluorescence emission is recorded for complexes with multiple p-arylacetylide units, and this is attributed to a triplet-triplet annihilation process. The phosphorescence energy of these complexes are readily modified by altering the length of the conjugated arylacetylide system, while the intensity of phosphorescence relative to fluorescence decreases when the p-arylacetylide chain is elongated. Information regarding the nature and relative energies of arylacetylide singlet and triplet excited states has been derived from the two homologous series and extrapolated to polymeric arylacetylide species. The (3)(pipi) excited-state reduction potentials E degrees [Au(+)/Au] (Au = 1a, 2, and 4) are estimated to be -1.80, -1.28, and -1.17 V versus SSCE, respectively.     

External heavy-atom effect of gold in a supramolecular acid-base pi stack

The nucleophilic trinuclear Au(I) ring complex Au3(p-tolN=COEt)3, 1, forms a sandwich adduct with the organic Lewis acid octafluoronaphthalene, C10F8. The 1.C10F8 adduct has a supramolecular structure consisting of columnar interleaved 1 ratio 1 stacks in which the Au3(p-tolN=COEt)3 pi-base molecules alternate with the octafluoronaphthalene pi-acid molecules with distances between the centroid of octafluoronaphthalene to the centroid of 1 of 3.458 and 3.509 A. The stacking with octafluoronaphthalene completely quenches the blue photoluminescence of Au3 (p-tolN=COEt)3, which is related to inter-ring Au-Au bonding, and leads to the appearance of a bright yellow emission band observed at room temperature. The structured profile, the energy, and the lifetime indicate that the yellow emission of the 1.C10F(8) adduct is due to monomer phosphorescence of the octafluoronaphthalene. The 3.5 ms lifetime of the yellow emission of 1.C10F8 is two orders of magnitude shorter than the lifetime of the octafluoronaphthalene phosphorescence, thus indicating a strong gold heavy-atom effect. The diffuse-reflectance spectrum of the solid adduct shows new absorptions that are red-shifted from the absorptions of the monomeric organic and inorganic components alone, indicating charge transfer. Luminescence excitation spectra suggest that these new absorptions represent the major excitation route that leads to the yellow luminescence of 1.C10F8, which is different from the conventional heavy-atom effect in which the phosphorescence route entails simply the enhancement of the S1-T1 intersystem crossing of the organic compound.     

Aggregation-Enhanced Room-Temperature Phosphorescence from Au(I) Complexes Bearing Mesogenic Biphenylethynyl Ligands

Gold(I) complexes, enabling to form linear coordination geometry, are promising materials for manifesting both aggregation-induced emission (AIE) behavior due to strong intermolecular Au–Au (aurophilic) interactions and liquid crystalline (LC) nature depending on molecular geometry. In this study, we synthesized several gold(I) complexes with rod-like molecular skeletons where we employed a mesogenic biphenylethynyl ligand and an isocyanide ligand with flexible alkoxyl or alkyl chains. The AIE behavior and LC nature were investigated experimentally and computationally. All synthesized gold(I) complexes exhibited AIE properties and, in crystal, room-temperature phosphorescence (RTP) with a relatively high quantum yields of greater than 23% even in air. We have demonstrated that such strong RTP are drastically changed depending on the crystal-size and/or crystal growth process that changes quality of crystals as well as the aggregate structure, of e.g., Au–Au distance. Moreover, the complex with longer flexible chains showed LC nature where RTP can be observed. We expect these rod-like gold(I) complexes to have great potential in AIE-active LC phosphorescent applications such as linearly/circularly polarizing phosphorescence materials.     

双核Au(Ⅰ)配合物[Y+]2[Au(i-mnt)]2(Y+=[n-Bu4N]+,K+,[Ph4As]+)发光机制的从头计算研究

用从头算方法研究[Au(i-mnt)]22-(i-mnt=i-marononitriledithiolate)的电子吸收和磷光发射性质,利用MP2和CIS方法分别优化了[Au(i-mnt)]22-基态和激发态几何结构.计算的基态Au(Ⅰ)—Au(Ⅰ)键长为0.2825nm,表明Au(Ⅰ)之间存在弱吸引作用.采用SCRF方法中IPCM模型模拟配合物在乙氰溶液中的行为,计算得到的最大吸收波长为315.5nm,指认X1Ag→A1Au来源于i-mnt配体内电荷转移跃迁.在436.2nm处得到具有B3Au→1Ag跃迁的磷光发射,指认为i-mnt配体内电荷转移和金属到配体电荷转移跃迁,与500nm乙氰溶液的发射相对应,为金属修饰的有机配体发光机制.     

Anomalous structure-luminescence relationship in phosphorescent gold(I) isonitrile neutral complexes

A new compound that exhibits the shortest intermolecular Au...Au distance ever reported for neutral RNCAuX complexes is found to exhibit a counterintuitive higher-energy Au-centered phosphorescence than that in an analogous compound with a much longer Au...Au distance, presumably due to a different extent of excited-state distortion in dimers vs. extended chains.     

Ambient-temperature metal-to-ligand charge-transfer phosphorescence facilitated by triarylboron: Bnpa and its metal complexes

A Cu(I) complex, 1, and a Pt(II) complex, 2a, of a triarylboron ligand, Bnpa, with bright ambient-temperature phosphorescence have been obtained. The phosphorescence of these complexes is highly sensitive toward molecular oxygen and has a distinct response to fluoride ions. For 1, the fluoride ion causes phosphorescent quenching and Bnpa dissociation, and for 2a, it switches phosphorescent color from yellow to green. The Cu(I) complex has an exceptionally high emission quantum yield (0.88) in the solid state.     

Syntheses, structures, and photophysical properties of mono- and dinuclear sulfur-rich gold(I) complexes

The dinuclear gold complexes [{Au(PPh 3)} 2(mu- dmid)] ( 1) ( dmid = 1,3-dithiole-2-one-4,5-dithiolate) and [{Au(PPh 3)} 2(mu- dddt)] ( 2) ( dddt = 5,6-dihydro-1,4-dithiine-2,3-dithiolate) were synthesized and characterized by X-ray crystallography. Both complexes exhibit intramolecular aurophilic interactions with Au...Au distances of 3.1984(10) A for 1 and 3.1295(11) A for 2. A self-assembly reaction between 4,5-bis(2-hydroxyethylthio)-1,3-dithiole-2-thione ( (HOCH 2 CH 2 ) 2 dmit) and [AuCl(tht)] affords the complex [AuCl{ (HOCH 2 CH 2 ) 2 dmit}] 2 ( 4), which possesses an antiparallel dimeric arrangement resulting from a short aurophilic contact of 3.078(6) A. This motif is extended into two dimensions due to intra- and intermolecular hydrogen bonds via the hydroxyethyl groups, giving rise to a supramolecular network. Three compounds were investigated for their rich photophysical properties at 298 and 77 K in 2-MeTHF and in the solid state; [Au 2(mu- dmid)(PPh 3) 2] ( 1), [Au 2(mu- dddt)(PPh 3) 2] ( 2), and [AuCl{( HOCH 2 CH 2 ) 2 dmit}] ( 4). 1 exhibits relatively long-lived LMCT (ligand-to-metal charge transfer) emissions at 298 K in solution (370 nm; tau e approximately 17 ns, where M is a single gold not interacting with the other gold atom; i.e., the fluxional C-SAuPPh 3 units are away from each other) and in the solid state (410 nm; tau e approximately 70 mus). At 77 K, a new emission band is observed at 685 nm (tau e = 132 mus) and assigned to a LMCT emission where M is representative for two gold atoms interacting together consistent with the presence of Au...Au contacts as found in the crystal structure. In solution at 77 K, the LMCT emission is also red-shifted to 550 nm (tau e approximately 139 mus). It is believed to be associated to a given rotamer. 2 also exhibits LMCT emissions at 380 nm at 298 K in solution and at 470 nm in the solid state. 4 exhibits X/MLCT emission (halide/metal to ligand charge transfer) where M is a dimer in the solid state with obvious Au...Au interactions, resulting in red-shifted emission band, and is a monomer in solution in the 10 (-5) M concentration (i.e., no Au...Au interactions) resulting in blue-shifted luminescence. Both fluorescence and phosphorescence are observed for 4.     

The effect of the antioxidant spermine on the photophysical reactions of tryptophan in aqueous solution at 77 K

Fluorescence, phosphorescence and electron paramagnetic resonance techniques were used to investigate the effect of the antioxidant spermine on the initial photophysical reactions of tryptophan (Trp) in aqueous salt solutions at 77 K. At low concentrations of Trp (3.5 X 10(-5) M) a ground state complex was formed between one Trp and two spermine molecules (a 1:2 complex). Complexed Trp was photodegraded at a rate 65% lower than the free molecule due to a change in the charge-transfer character of the excited 1La state. At high concentrations of Trp (3.5 X 10(-3) M) the phosphorescence was almost completely quenched due to hydrogen-bond formation between two neighbouring Trp molecules. A strong complex was formed between this Trp dimer and one spermine molecule on addition of spermine (a 2:1 complex). Spermine enhanced intersystem crossing in one of the two Trp molecules in the 2:1 complex and phosphorescence was observed. From this triplet state the tryptophyl radical was formed with high efficiency by hydrogen-atom transfer. The yield of radical formation from the triplet state in the 2:1 complex was much larger than from the excited singlet state in the 1:2 complex.     

Modulation of metallophilic bonds: solvent-induced isomerization and luminescence vapochromism of a polymorphic Au-Cu cluster

We report a homoleptic Au-Cu alkynyl cluster that represents an unexplored class of luminescent materials with stimuli-responsive photophysical properties. The bimetallic complex formulated as [Au(2)Cu(2)(C(2)OHC(5)H(8))(4)](n) efficiently self-assembles from Au(SC(4)H(8))Cl, Cu(NCMe)(4)PF(6), and 1-ethynylcyclopentanol in the presence of NEt(3). This compound shows remarkably diverse polymorphism arising from the modulation of metallophilic interactions by organic solvents. Four crystalline forms, obtained from methanol (1a); ethanol, acetone, or choloroform (1b); toluene (1c); and diethyl ether or ethyl acetate (1d), demonstrate different photoluminescent characteristics. The solid-state quantum yields of phosphorescence (Φ) vary from 0.1% (1a) to 25% (1d), depending on the character of intermetallic bonding. The structures of 1b-d were determined by single-crystal X-ray diffraction. The ethanol (1b, Φ = 2%) and toluene (1c, Φ = 10%) solvates of [Au(2)Cu(2)(C(2)OHC(5)H(8))(4)](n) adopt octanuclear isomeric structures (n = 2), while 1d (Φ = 25%) is a solvent-free chain polymer built from two types of Au(4)Cu(4) units. Electronic structure calculations show that the dramatic enhancement of the emission intensity is correlated with the increasing role of metal-metal bonding. The latter makes the emission progressively more metal-centered in the order 1b < 1c < 1d. The metallophilic contacts in 1a-d show high sensitivity to the vapors of certain solvents, which effectively induce unusual solid-state isomerization and switching of the absorption and luminescence properties via non-covalent interactions. The reported polymorphic material is the first example of a gold(I) alkynyl compound demonstrating vapochromic behavior.     

Trinuclear gold(I) triazolates: a new class of wide-band phosphors and sensors

A new cyclic gold(I) triazolate trimer, [Au(3,5-i-Pr2Tz)]3 (1), exhibits fully overlapping aurophilically bonded dimer-of-trimer units that lead to multiple phosphorescence bands in both the solid state and solution. The conformation of the hexanuclear unit exhibits reversible interconversion between C2 and D3 effective symmetries, depending on the crystal temperature or solution concentration, the variation of which leads to isoemissive and isosbestic points. Solutions of 1 exhibit remarkable quenching properties that demonstrate molecular recognition with high selectivity and hypersensitivity for some reagents, as influenced by protonation via Br?nsted acids, pi intercalation, and/or energy transfer. The quenched phosphorescence of 1 by acetic acids can be regenerated by NEt3.