Solid-state luminescence of Au(I) complexes with external stimuli-responsive properties

In the last decade, the field of stimuli-responsive luminescent materials have been intensely emerged because of the high potential application to functional sensors or photoelectronic devices. In particular, luminescent molecular crystals constructed from Au(I) complexes have produced a wide range of examples of luminescent alterations when some external stimulations, such as heat, mechanical stress, vapor (or solvents), were applied to the solid samples. In this review, we describe the recent progress through a summary of the reported Au(I) complexes based on their utilized stimuli-responsive mechanisms, which are categorized in crystal phase transitions (“crystal-to-amorphous”, “crystal-to-crystal” and “single-crystal-to-single-crystal” transitions) and molecular rotation in crystalline media, respectively.     

Adduct effects on structure and luminescence in a series of new dithiocarbamatogold(I) complexes

Reaction of [AuCl(SMe₂)] with NaL·H₂O (L = ethyl(pyridine-4-yl methyl)dithiocarbamate (epdtc) or methyl(2-(pyridin-2-yl)ethyl)dithiocarbamate (mpdtc)) affords a series of neutral dinuclear gold(I) complexes bridged by each dithiocarbamate ligand, [Au(L)]₂. The successive reaction of [Au(L)]₂ with organic acids such as isophthalic acid (m-pa) and maleic acid (ma) produces 1:1 adducts, [Au(L)]₂·(organic acid). The crystal structure of [Au(L)]₂·(m-pa) is a 1D polymer formed via hydrogen bonds between the free pyridyl and the carboxylic acid moiety. For the dinuclear moiety, strong intradinuclear aurophilic interactions (Au(I)–Au(I) = 2.7783(8) Å and 2.7525(7) Å) exist, but interdinuclear interactions are weak (3.2551(8)–3.2733(8) Å). The dinuclear gold(I) complexes, [Au(epdtc)]₂ and [Au(mpdtc)]₂, show a bright luminescence at 562.5 and 552.0 nm in solid state, respectively, but their organic acid adducts, [Au(L)]₂·(organic acid), have no luminescent properties. This dramatic difference in properties between the gold(I) complexes and their adducts may be ascribed to the weakness of the internuclear Au(I)–Au(I) interaction including crystal packing.     

X-ray-excited optical luminescence (XEOL) and X-ray absorption fine structures (XAFS) studies of gold(I) complexes with diphosphine and bipyridine ligands

Synchrotron techniques, X-ray-excited optical luminescence (XEOL) combined with X-ray absorption fine structures (XAFS), have been used to study the electronic structure and optical properties of a series of luminescent gold(I) complexes with diphosphine and bipyridine ligands using tunable X-rays (in the regions of the C and P K-edges and the Au L3-edge) and UV from synchrotron light sources. The effects of gold-ligand and aurophilic interactions on the luminescence from these gold(I) complexes have been investigated. It is found that the luminescence from these complexes is phosphorescence, primarily due to the decay of the Au (5d) --> PR3 (pi*), metal to ligand charge transfer (MLCT) excitation as well as contributions from the conjugated pi-system in the bipyridine ligands via the gold-nitrogen bond. The large Au 5d spin-orbit coupling enhances the intersystem crossing. The elongation of the hydrocarbon chain of the diphosphine ligand does not greatly affect the spectral features of the luminescence from the gold(I) complexes. However, the intensity of the luminescence was reduced significantly when the bipyridine ligand was replaced with 1,2-bis(4-pyridylamido)benzene. The aurophilic interaction, as investigated by EXAFS at the Au L3-edge, is shown to be only one of the factors that contribute to the luminescence of the complexes.     

Supramolecular luminescent gold(I)-copper(I) complexes: self-assembly of the Au(x)Cu(y) clusters inside the [Au3(diphosphine)3]3+ triangles

The reactions between diphosphino-alkynyl gold complexes (PhC2Au)PPh2(C6H4)(n)PPh2(AuC2Ph) (n = 1, 2, 3) with Cu(+) lead to formation of the heterometallic aggregates, the composition of which may be described by a general formula [{Au(x)Cu(y)(C2Ph)2x}Au3{PPh2(C6H4)(n)PPh2}3](3+(y-x)) (n = 1, 2, 3; x = (n + 1)(n + 2)/2; y = n(n + 1)). These compounds display very similar structural patterns and consist of the [Au(x)Cu(y)(C2Ph)2x](y-x) alkynyl clusters "wrapped" in the [Au3(diphosphine)3](3+) triangles. The complex for n = 1 was characterized crystallographically and spectrally, the larger ones (n = 2, 3) were investigated in detail by NMR spectroscopy. Their luminescence behavior has been studied, and a remarkably efficient emission with a maximum quantum yield of 0.92 (n = 1) has been detected. Photophysical experiments demonstrate that an increase of the size of the aggregates leads to a decrease in photostability and photoefficiency. Computational studies have been performed to provide additional insight into the structural and electronic properties of these supramolecular complexes. The theoretical results obtained are in good agreement with the experimental data, supporting the proposed structural motif. These studies also suggest that the observed efficient long-wavelength luminescence originates from metal-centered transitions within the heterometallic Au-Cu core.     

某些Au(III)、Au(I)配离子在溶液中扩散的研究

用毛细管色谱在25℃测定了AuCl4、[Au(SO3)2]、[Au(CSN2H4)2]、[Au(CN)2]等配位体离子在HCl溶液中的扩散系数及AuCl4阴离子的扩散活化能, 并与文献中其它配阴离子的D值比较, 认为扩散离子的质量和所载电荷可能是决定配阴离子扩散系数的主要因素.     

Selenolate gold complexes with aurophilic Au(I)-Au(I) and Au(I)-Au(III) interactions

The gold(I) selenolate compound [Au(2)(SePh)(2)(mu-dppf)] (dppf = 1,1'-bis(diphenylphosphino)ferrocene) has been prepared by reaction of [Au(2)Cl(2)(mu-dppf)] with PhSeSiMe(3) in a molar ratio 1:2. This complex reacts with gold(I) or gold(III) derivatives to give polynuclear gold(I)-gold(I) or gold(I)-gold(III) complexes of the type [Au(4)(mu-SePh)(2)(PPh(3))(2)(mu-dppf)](OTf)(2), [Au(3)(C(6)F(5))(3)(mu-SePh)(2)(mu-dppf)], or [Au(4)(C(6)F(5))(6)(mu-SePh)(2)(mu-dppf)], with bridging selenolate ligands. The reaction of [Au(2)(SePh)(2)(mu-dppf)] with 1 equiv of AgOTf leads to the formation of the insoluble Ag(SePh) and the compound [Au(2)(mu-SePh)(mu-dppf)]OTf. The complexes [Au(4)(C(6)F(5))(6)(mu-SePh)(2)(mu-dppf)] and [Au(2)(mu-SePh)(mu-dppf)]OTf (two different solvates) have been characterized by X-ray diffraction studies and show the presence of weak gold(I)-gold(III) interactions in the former and intra- and intermolecular gold(I)-gold(I) inter-actions in the later.     

Progress in mechanochromic luminescence of gold(I) complexes

Photophysical properties of organic and organometallic luminophors are closely related with their molecular packings, enabling the exploitation of stimuli-responsive functional luminescent molecules. Mechanochromic molecules, which can change their luminescence characteristics after mechanical stimulus, have received an increasing interest due to their promising applications in multifunctional sensors and molecular switches. During the past two decades, the development of gold(I) chemistry has been attracting the attention of plenty of researchers. Indeed, a variety of gold(I) complexes with fascinating photophysical behaviors have been discovered. This review focuses on the research progress in the different types of mechanoluminochromic gold(I) complexes, including mono-, bi- and multi-nuclear gold(I) systems. Their interesting luminescence behaviors of these gold(I)-containing luminogens upon mechanical stimulus and the proposed mechanisms of their observed mechanochromic luminescence are summarized systematacially. Moreover, this review will put forward an outlook about the possible opportunities and challenges in this significative scientific field.     

Polymeric complexes of silver(I) with diphosphine ligands: self-assembly of a puckered sheet network structure

The syntheses and structures of polymeric silver(I)-diphosphine complexes are reported, in which the silver(I) center is surrounded by 1, 2, or 3 phosphorus atoms. When rigid diphosphine ligands are used in combination with weakly coordinating anions, linear polymers are obtained that contain both diphosphine and anion bridges. However, with excess of a diphosphine with a long, flexible, spacer group, a remarkable puckered sheet structure, comprised of fused giant 54-membered rings, is obtained that is a coordination polymer analogue of laminated materials such as micas and clays. The polymeric chain and sheet structures may be considered to be formed by ring-opening polymerization of cyclic precursors.     

Synthesis,structure, and luminescence of rhenium(I) complexes with substituted bipyridines

Two new rhenium(I) complexes chelated by a substituted 2,2′-bipyridine with general formula Re(CO)₃LCl, where L?=?6?-(2″-methoxyphenyl)-2,2′-bipyridine (L₁ ) and 6?-(4″-diphenylaminophenyl)-2,2′-bipyridine (L₂ ), are synthesized and characterized by IR, NMR, and elemental analysis. Structure of 1 was determined by single-crystal X-ray crystallography, revealing that rhenium is six-coordinate octahedral. The electrochemical, photophysical, and thermal properties of the two rhenium(I) complexes were investigated. Electroluminescent devices were fabricated by doping 1 in polymer blend host of poly(vinylcarbazole) and 2-tert-butylphenyl-5-biphenyl-1,3,4-oxadiazole using simple solution spin-coating technique. The device exhibits a maximum current efficiency of 2.97?cd?A^?1 and peak brightness in excess of 2390?cd?m^?2.     

Synthesis and characterization of neutral luminescent diphosphine pyrrole- and indole-aldimine copper(I) complexes

Heteroleptic copper(I) complexes of the types [Cu(N,N)(P,P)] and [Cu(N,O)(P,P)], where (P,P) = phosphine (PPh(3)) or diphosphine (dppb, DPEPHOS, XANTPHOS), (N,N) = pyrrole-2-phenylcarbaldimine, 2PyN: [Cu(2PyN)(PPh(3))(2)] (1), [Cu(2PyN) (dppb)] (2), [Cu(2PyN)(DPEPHOS)] (3), and [Cu(2PyN)(XANTPHOS)] (4), (N,N) = indole-2-phenylcarbaldimine, 2IndN: [Cu(2IndN)(DPEPHOS)] (8), and (N,O) = pyrrole-2-carboxaldehyde, 2PyO: [Cu(2PyO)(DPEPHOS)] (5), [Cu(2PyO)(XANTPHOS)] (6), or (N,O) = indole-2-carboxaldehyde, 2IndO: [Cu(2IndO)(DPEPHOS)] (7), were synthesized and characterized by multinuclear NMR spectroscopy, electronic absorption spectroscopy, fluorescence spectroscopy, and X-ray crystallography (1-3, 5-8). The complexes with aldimine ligands are thermally stable, and sublimation of 2-4 was possible at T = 230-250 °C under vacuum. All complexes exhibit long-lived emission in solution, in the solid state, and in frozen glasses. The excited states have been assigned as mixed intraligand and metal-to-ligand charge transfer (3)(MLCT + π-π*) transitions through analysis of the photophysical properties and DFT calculations on representative examples.     

Photochemistry of neutral isonitrile gold(I) complexes: modulation of photoreactivity by aurophilicity and pi-acceptance ability

This work demonstrates for the first time that aurophilicity and ligand pi-acceptance ability sensitize the photoreactivity of Au(I) complexes. Photolysis of LAu(I)Cl (L = RNC or CO) complexes leads to free L, Au(III), and Au(0) photoproducts. Solutions of (p-tosyl)CH(2)NCAuCl in dichloromethane undergo significant oligomerization leading to dimers and trimers with formation constants of 1.61 x 10(3) and 6.61 x 10(3) M(-1), respectively, representing the highest values reported to date for complexes that exhibit aurophilic association in solution. The photoproduct quantum yield (Phi) varies with the LAu(I)Cl concentration in solution. For (p-tosyl)CH(2)NCAuCl, metallic gold forms with Phi = 0.0065 and 0.032 in 4.0 x 10(-5) and 4.0 x 10(-3) M dichloromethane solutions, respectively. Meanwhile, irradiation of t-BuNCAuCl primarily produces t-BuNCAuCl(3) with Phi = 0.0045 and 0.013 for 5.0 x 10(-5) and 5.0 x 10(-3) M dichloromethane solutions, respectively. For Au(CO)Cl, metallic gold forms with Phi = 0.013 and 0.065 upon irradiation of 8.0 x 10(-5) and 8.0 x 10(-3) M dichloromethane solutions, respectively. Hence, *[LAuX](n) oligomeric species are more photoreactive than monomeric species. The results also demonstrate intuitive control of Phi via modulation of the pi-acceptance ability of L, as both follow CO > (p-tosyl)CH(2)NC > (alkyl)NC in LAuCl, a trend that is also commensurate with the relative long-term photosensitivity of the corresponding solids and solutions. A new method for preparing stable small gold nanoparticles is described based on the fundamental findings above. Thus, photolysis of different concentrations of LAuX in solutions containing a primary amine-terminated dendrimer leads to clear solutions exhibiting tunable visible plasmon absorptions of gold nanoparticles; these solutions maintain their colors and stability indefinitely. TEM measurements for representative samples prepared by photolysis of (p-tosyl)CH(2)NCAuCl solutions give rise to spherical nanoparticles as small as 5 nm.     

Selenourea complexes of Cu(I), Ag(I), and Au(I) chlorides

Russian Chemical Bulletin -     

Structural motifs of Au(I)-Cu(I) N-heterocyclic carbene halide complexes

A series of Au(I)–Cu(I) N-heterocyclic carbene (NHC) halide complexes [AuCu₂(im(CH₂py)₂)₂X]²⁺ where X?=?Cl (1), Br (2), I (3) was prepared by refluxing [AuCu₂(im(CH₂py)₂)₂(NCCH₃)₄]³⁺ with the appropriate halide in acetonitrile. The compounds were characterized by NMR, absorption, and fluorescence spectroscopy. They feature similar solution behavior and solid-state photoemissions. The solid-state structures feature a rhomboidal [AuCu₂X]²⁺ core which is influenced by the type of halide. Compared to other Au(I)–Cu(I) NHC complexes, 1–3 comprise a new structural motif containing a bridging halide. The benzimidazolium analog of 1 was also characterized crystallographically. The structure of [AuCu₂(benzim(CH₂py)₂)₂Cl]²⁺(4) features different coordination modes of the NHC ligands with the carbenic carbon bonded to both gold and copper and the pyridyl groups bonded to the same copper(I) ion.     

Trichlorostannato(diphosphine)rhodium(I) complexes. Crystal structure of [Rh(SnCl3)(1,5-cyclooctadiene)(dppp)]

The molecular structure of [Rh(SnCl₃)(1,5-cyclooctadiene)(dppp)] [dppp = 1,3-bis(diphenylphosphino)propane] has been determined to R_F = 3.6% single-crystal X-ray techniques. The crystal contains two discrete molecules 1 and 2 per asymmetric unit. Molecule 1 is best described as distorted trigonal bipyramidal with the diolefin and the diphosphine occupying both apical and equatorial positions and the SnCl₃ group on an equatorial position, and molecule 2 as distorted square pyramidal with the equatorial positions occupied by the diolefin and the diphosphine, respectively, and the SnCl₃ fragment in the apical position. In solution at room temperature, complexes [Rh(SnCl₃)(COD)(diphosphine)] exhibit tin dissociation and various intramolecular rearrangements.     

Gold(I) and platinum(II) complexes with a new diphosphine ligand based on the cyclotriphosphazene platform

A new diphosphine ligand assembled on the cyclotriphosphazene platform forms linear chelate and dimetallic bridged complexes with Au(I) and a cis-chelate complex with Pt(II).     

Cationic, linear Au(I) N-heterocyclic carbene complexes: synthesis, structure and anti-mitochondrial activity

Six linear, two-coordinate cationic Au(I) N-heterocyclic carbene complexes of the form [(R2Im)2Au]+ (R = Me 1, Me, Et 2, i-Pr 3, n-Bu 4, t-Bu 5 and Cy 6) have been prepared by the reaction of two equivalents of the appropriate dialkylimidazol-2-ylidene (R2Im) with (Me2S)AuCl in dmf. Single crystal structural studies for 1.PF6, 2.PF6), 3.Cl and 4-6.PF6 show that for all six complexes the gold(I) centres have quasi-linear C-Au-C coordination, with quasi-parallel pairs of aromatic imidazole planes, except in 5.PF6 where they are quasi-normal; in the latter, Au-C are 2.038(3), 2.033(3) A, cf. (e.g.) 2.027(2) A. Inter-cation Au...Au are close at 3.487(2), 3.525(2) A in 1PF6 and 2.PF6. The structural studies and low temperature NMR experiments provide no supportive evidence for the presence of pi back-bonding within this series of complexes. The lipophilicities of the six compounds, as estimated from the logarithm of the n-octanol-water partition coefficients (log P), varied across the series within the range -1.09 to 1.73. To investigate their potential as possible anti-mitochondrial anti-tumour agents, five of the compounds have been evaluated for their propensities to induce mitochondrial membrane permeabilization (MMP) in isolated rat liver mitochondria. At concentrations between 1-10 microM compounds 1.Br and 3-6.Cl induced dose-dependent, Ca2+-sensitive mitochondrial swelling at rates that increased with the lipophilicities of the complexes, with the most lipophilic compounds inducing the most rapid onset of swelling. The swelling was completely inhibited by cyclosporin A, the specific inhibitor of the mitochondrial permeability transition pore.