Coinage Metal Complexes Supported by the Tri- and Tetraphosphine Ligands

A Phosphorescent P/N/S Hybrid Ligand Stabilized Au2Cu Complex Selectively Senses Ammonia and Amines

Reaction of a P/N/S hybrid ligand dpppyatc (N,N-bis((diphenylphosphaneyl)methyl)-N-(pyridin-2-yl)-amino-thiocarbamide) with Au(tht)Cl (tht=tetrahydrothiophene) and [Cu(MeCN)4]BF4 afforded cluster complex [Au2Cu(dpppyatc)2](BF4)2Cl (1). Upon excitation at 480 nm, 1 emitted orange phosphorescence at 646 nm, which was red-shifted to ~698 nm selectively in the presence of ammonia or amine vapor. This chromic photoluminescent response toward ammonia was sensitive and reversible. Complex1 could detect ammonia in aqueous solution down to concentrations of 2 ppm (w/w).

Near-white light emission from single crystals of cationic dinuclear gold(I) complexes with bridged diphosphine ligands

Three cationic dinuclear Au(I) complexes containing acetonitrile (AN) as an ancillary ligand were synthesized: [μ-L_Me(AuAN)₂]·2BF₄ (1), [μ-L_Et(AuAN)₂]·2BF₄ (2), and [μ-L_iPr(AuAN)₂]·2BF₄ (3) (L_Me = {1,2-bis[bis(2-methylphenyl)phosphino]benzene}, L_Et = {1,2-bis[bis(2-ethylphenyl)phosphino]benzene}, and L_iPr = {1,2-bis[bis(2-isopropylphenyl)phosphino]benzene}). The unique structures of complexes 1-3 with two P-Au(I)-AN rods bridged by rigid diphosphine ligands were determined through X-ray analysis. The Au(I)-Au(I) distances observed for complexes 1-3 were as short as 2.9804-3.0457 Å, indicating an aurophilic interaction between two Au(I) atoms. Unlike complexes 2 and 3, complex 1 incorporated CH₂Cl₂ into the crystals as crystalline solvent molecules. Luminescence studies in the crystalline state revealed that complexes 1 and 2 mainly exhibited bluish-purple phosphorescence (PH) at 293 K: the former had a PH peak wavelength at 415 nm with the photoluminescence quantum yield Φ_PL = 0.12, and the latter at 430 nm with Φ_PL = 0.13. Meanwhile, complex 3 displayed near-white PH, that is dual PH with two PH bands centered at 425 and 580 nm with Φ_PL = 0.44. The PH spectra and lifetimes of complexes 2 and 3 were measured in the temperature range of 77-293 K. The two PH bands observed for complex 3 were suggested to originate from the two emissive excited triplet states, which were in thermal equilibrium. From theoretical calculations, the dual PH observed for complex 3 is explained to occur from the two excited triplet states, T_1H and T_1L: the former exhibits a high-energy PH band (bluish-purple) and the latter exhibits a low-energy PH band (orange). The T_1H state is considered ³ILCT with a structure similar to that of the S₀-optimized structure. Conversely, the T_1L state is assumed to be a ³MLCT with a T₁-optimized structure, which has a short Au(I)-Au(I) bond and two bent rods (Au-AN). The thermal equilibrium between the two excited states is discussed based on computational calculations and photophysical data in the temperature range of 77-293 K. With regard to the crystal of complex 1, we were unable to precisely measure the temperature-dependent emission spectra and lifetimes, particularly at low temperatures, because the cooled crystals became irreversibly turbid over time.

Controllable Synthesis and Luminescence Behavior of Tetrahedral Au@Cu4 and Au@Ag4 Clusters Supported by tris(2-Pyridyl)phosphine

We report herein a family of polynuclear complexes, [Au@Ag₄(Py₃P)₄]X₅ and [Au@Cu₄(Py₃P)₄]X₅ [X = NO₃, ClO₄, OTf, BF₄, SbF₆], containing unprecedented Au-centered Ag₄ and Cu₄ tetrahedral cores supported by tris(2-pyridyl)phosphine (Py₃P) ligands. The [Au@Ag₄]⁵⁺ clusters are synthesized via controlled substitution of the central Ag(I) ion in all-silver [Ag@Ag₄]⁵⁺ precursors by the reaction with Au(tht)Cl, while the [Au@Cu₄]⁵⁺ cluster is assembled through the treatment of a pre-organized [Au(Py₃P)₄]⁺ metallo-ligand with 4 equiv of a Cu(I) source. The structure of the Au@M₄ clusters has been experimentally and theoretically investigated to reveal very weak intermolecular Au-M metallophilic interactions. At ambient temperature, the designed compounds emit a modest turquoise-to-yellow luminescence with microsecond lifetimes. Based on the temperature-dependent photophysical experiments and DFT/TD-DFT computations, the emission observed has been assigned to an MLCT or LLCT type depending on composition of the cluster core.

Selective coordination of coinage metals using orthogonal ligand scaffolds

Group 11 metal complexes with their ability to form metallophilic interations are widely pursued to develop multifunctional luminescent materials. Heteronuclear coinage metal complexes are promising candidates to tune electronic and optical properties which are not readily accessed by their homometallic congeners. In this review, we present the concept of orthogonal ligands which are rationally designed to access heteronuclear coinage metal complexes and studied in terms of their photophysical properties. Bifunctional ligands containing soft and hard donor atoms have the potential of providing different coordination modes to selectively synthesise heterobimetallic complexes in a predictable manner. This review deals with ligand sets composed of pyridine, bipyridine- or iminopyridine-substituted NHCs featuring C-N coordination modes, phosphine-based N-heterocycles and amidinate ligand scaffolds comprising of P-N functionalities and mixed phosphine-phosphine oxide with P-O donor sites. Therefore, the scope of this perspective is the discussion of heteronuclear coinage metal complexes supported by recently developed bifunctional ligands in terms of their synthesis, coordination geometries and tunability of optical properties when compared to their homometallic analogues.

Synthesis and photophysical properties of multimetallic gold/zinc complexes of (P,N,N,N,P) and (P,N,N) ligands

Orthogonal coordination of gold and zinc yields mono- and bimetallic complexes, which are investigated concerning their photophysics.

Bright Luminescence in Three Phases-A Combined Synthetic, Spectroscopic and Theoretical Approach

Combining phase-dependent photoluminescence (PL) measurements and quantum chemical calculations is a powerful approach to help understand the influence of the molecular surroundings on the PL properties. Herein, a phosphine functionalized amidinate was used to synthesize a recently presented bimetallic gold complex, featuring an unusual charge separation. The latter was subsequently used as metalloligand to yield heterotetrametallic complexes with an Au-M-M-Au "molecular wire" arrangement (M=Cu, Ag, Au) featuring metallophilic interactions. All compounds show bright phosphorescence in the solid state, also at ambient temperature. The effect of the molecular environment on the PL was studied in detail for these tetrametallic complexes by comparative measurements in solution, in the solid state and in the gas phase and contrasted to time-dependent density functional theory computations.

Bi- and trinuclear coinage metal complexes of a PNNP ligand featuring metallophilic interactions and an unusual charge separation

A selective synthesis of bi- and trinuclear complexes featuring a tetradentate monoanionic PNNP ligand is presented. The binuclear coinage metal complexes show a typical fourfold coordination for Cu and Ag, which changes to a bifold coordination for Au. The latter is accompanied by an unusual charge separation. Optical properties are investigated using photoluminescence spectroscopy and complemented by time-dependent density-functional-theory calculations. All compounds demonstrate clearly distinguished features dependent on the metals chosen and differences in the complex scaffold.

Mechanochemical synthesis of mononuclear gold(I) halide complexes of diphosphine ligands with tuneable luminescent properties

A mechanochemical method is reported for the synthesis of Au(diphos)X complexes of diphosphine (diphos = XantPhos and N-XantPhos) ligands and halide ions (X = Cl and I). The Au(XantPhos)X (1: X = Cl; 2: X = I) and Au(N-XantPhos)Cl (3) complexes exhibited either yellowish green (1) or bluish green (2) emission, whereas 3 was seemingly non-emissive in the solid state at room temperature. Blue- (2B) and bluish green (2G) luminescent concomitant solvates of 2 were obtained by recrystallization. Luminescent colour changes from blue (2B) or bluish green (2G) to yellow were observed when these forms were subjected to mechanical stimulus, while the original emission colour can be recovered in the presence of solvent vapours. Moreover, the luminescence of 2B can be reversibly altered between blue and yellow by heating/cooling-cycles. These results demonstrate the power of mechanochemistry in the rapid (4 min reaction time), efficient (up to 98% yield) and greener synthesis of luminescent and stimuli-responsive gold(I) complexes.

Transition Metal Chain Complexes Supported by Soft Donor Assembling Ligands

The chemistry of discrete molecular chains constituted by metals in low oxidation states, displaying metal-metal proximity and stabilized by suitable metal-bridging, assembling ligands comprising at least one soft donor atom is comprehensively reviewed; complexes with a single (hard or soft) bridging atom (e.g., μ-halide, μ-sulfide, or μ-PR₂ etc.) as well as "closed" metal arrays (that fall in the realm of cluster chemistry) are excluded. The focus is on transition metal-based systems, with few excursions to cases combining transition and post-transition elements. Most relevant supporting ligands have neutral C, P, O, or S donor (mainly, N-heterocyclic carbene, phosphine, ether, thioether) or anionic donor (mainly phenyl, ylide, silyl, phosphide, thiolate) groups. A supporting-ligand-based classification of the metal chains is introduced, using as the classifying parameter the number of "bites" (i.e., ligand bridges) subtending each intermetallic separation. The ligands are further grouped according to the number of donor atoms interacting with the metal chain (called denticity in the following) and the column of the Periodic Table to which the set of donor atoms belongs (in ascending order). A complementary metal-based compilation of the complexes discussed is also provided in a concise tabular form.

Keep it tight: a crucial role of bridging phosphine ligands in the design and optical properties of multinuclear coinage metal complexes

Copper subgroup metal ions in the +1 oxidation state are classical candidates for aggregation via non-covalent metal-metal interactions, which are supported by a number of bridging ligands. The bridging phosphines, soft donors with a relatively labile coordination to coinage metals, serve as convenient and essential components of the ligand environment that allow for efficient self-assembly of discrete polynuclear aggregates. Simultaneously, accessible and rich modification of the organic spacer of such P-donors has been used to generate many fascinating structures with attractive photoluminescent behavior. In this work we consider the development of di- and polynuclear complexes of M(i) (M = Cu, Ag, Au) and their photophysical properties, focusing on the effect of phosphine bridging ligands, their flexibility and denticity.

Photochromism and photocatalysis of organic–inorganic hybrid iodoargentates modulated by argentophilic interactions

A series of organic–inorganic hybrid iodoargentates exhibit photochromic and photocatalytic properties, which could be effectively modulated by argentophilic interactions.

Linear Copper Complex Arrays as Versatile Molecular Strings: Syntheses, Structures, Luminescence, and Magnetism

The defined linear arrangement of metal atoms in discrete coordination complexes or polymers is still one of the most intriguing challenges in synthetic chemistry. These chain arrangements are of fundamental importance, because of their potential applications as molecular wires and single molecule magnets (SMM) in microelectronic devices on a molecular scale. Oligonuclear Group 11 metal complexes with suitable bridging ligands, specifically those that are based on copper as the first choice of a cheap precursor coinage metal, are of particular interest in this regard. This is due to the superior luminescence properties of these linear clusters that often show d¹⁰ ⋅⋅⋅d¹⁰ interactions in their molecular structures. The combination of Cu^I with heavier coinage metal ions results in tunable emissive arrays that are also stimuli-responsive. Thus, both linear multinuclear Cu^I and linear heteropolymetallic Cu^I /Ag^I as well as Cu^I /Au^I clusters are excellent candidates for applications in molecular/organic light-emitting devices (OLEDs). Alternatively, paramagnetic multinuclear cupric arrays are prominent as potential molecular wires with enhanced magnetic properties through multiple coupled d⁹ centers. This Review covers the whole range of linear multinuclear assemblies of cuprous and cupric ions in complexes and coordination polymers, their syntheses, photophysical behavior, and magnetic properties. Moreover, recent advances in the rapidly progressing field of hetero-Cu^I /Ag^I and Cu^I /Au^I molecular strings are also discussed.

Linear CuI2 Pd0 , CuI Pd02 , and AgI2 Pd0 Metal Chains Supported by Rigid N,N'-Diphosphanyl N-Heterocyclic Carbene Ligands and Metallophilic Interactions

Selective copper(I) to palladium(0) transmetallation of P-donors from the rigid N,N'-diphosphanyl-imidazol-2-ylidene C₃ H₂ [NP(tBu)₂ ]₂ (PC^NHC P) was observed when known [Cu₃ (μ₃ -PC^NHC P,κP,κC^NHC ,κP)₂ ](OTf)₃ was reacted with [Pd(PPh₃ )₄ ]. When 1.2 equivalents of [Pd(PPh₃ )₄ ] was used, the product [Cu₂ Pd(μ₃ -PC^NHC P,κP,κC^NHC ,κP)₂ ](OTf)₂ (2(OTf)₂ ) was obtained, which features a Cu^I -Cu^I -Pd⁰ chain and appears to be the first linear heterotrinuclear complex with d¹⁰ -d¹⁰ interactions between Pd⁰ and Cu^I . When the Cu₃ precursor was reacted with 3.0 equivalents of [Pd(PPh₃ )₄ ], the complex [CuPd₂ (μ₃ -PC^NHC P,κP,κC^NHC ,κP)₂ ](OTf)₂ (3(OTf)₂ ) was obtained, which, on the basis of magnetic measurements, DFT calculations, and computed nuclear shieldings, was formulated as containing a Pd⁰ -Cu^I -Pd⁰ chain with an electron hole delocalized over the whole cation, including the metal chain. Similarly, selective transmetallation of the P-donors in [Ag₃ (μ₃ -PC^NHC P,κP,κC^NHC ,κP)₂ ](OTf)₃ from silver to palladium (originating from [Pd(PPh₃ )₄ ]) gave the linear chain [Ag₂ Pd(μ₃ -PC^NHC P,κP,κC^NHC ,κP)₂ ](OTf)₂ (5(OTf)₂ ), which on the basis of NMR spectroscopy comprises an Ag^I -Ag^I -Pd⁰ metal core. However, X-ray diffraction data collected on various samples of 5(OTf)₂ were modeled with 50:50 metal disorder at the terminal positions, corresponding to a (Ag^I /Pd⁰ )-Ag^I -(Ag^I /Pd⁰ ) formulation. Upon standing in solution, 5(OTf)₂ transformed to 6(OTf)₂ , the regioisomer of 5(OTf)₂ in which the Pd center has migrated to the central position of an Ag^I -Pd⁰ -Ag^I chain. Prolonged standing in CH₂ Cl₂ or by reaction with [PtCl₂ (NCMe)₂ ] converts complex 6(OTf)₂ to the Ag^I /Pd^II complex [Ag₂ PdCl₂ (μ₃ -PC^NHC P,κP,κC^NHC ,κP)₂ ](OTf)₂ (7(OTf)₂ ). The structural data of 2(OTf)₂ , 3(OTf)₂ , and 7(OTf)₂ establish significant heterometallophilic interactions.

Electron-rich linear triplatinum complexes stabilized by a spinning tetraphosphine, tris(diphenylphosphinomethyl)phosphine

Linear triplatinum complexes with 48e(-), [Pt3(μ-tdpmp)2(RNC)2](PF6)2 (R = 2,6-xylyl (3), (t)Bu (4)), were synthesized by using a branched tetraphosphine, tris(diphenylphosphinomethyl)phosphine (tdpmp), and characterized by crystallographic and spectroscopic analyses to show their novel dynamic behaviour in the solution state, in which the linear Pt3 unit was stabilized by two spinning tetraphosphine ligands.

Adjustable coordination of a hybrid phosphine–phosphine oxide ligand in luminescent Cu, Ag and Au complexes

The mixed-donor ligand shows variable binding ability with respect to d¹⁰ metal ions to afford a series of mono- and dinuclear complexes with tunable photophysical characteristics.