Tetradecanuclear and Octadecanuclear Gold(I) Sulfido Clusters: Synthesis, Structures, and Luminescent Selective Tracking of Lysosomes in Living Cells

Reactions of the phosphanyl-gold(I) precursor [(AuCl)₂(bdppmapy)] (1; bdppmapy = N,N-bis(diphenylphosphanylmethyl)-2-aminopyridine) with Na₂S in a 1:1 or 1:2 molar ratio gave rise to one tetradecanuclear and one octanuclear Au(I) sulfido cluster, [Au₁₄S₆(bdppmapy)₅]Cl₂ (2) and [Au₁₈S₈(bdppmapy)₆]Cl₂ (3), respectively. The former displays a new structural framework in gold cluster chemistry. Compounds 2 and 3 showed strong green luminescence and were employed as excellent imaging probes to selectively light up the lysosomes of living cells. Their long-term tracking of lysosomes can be achieved for up to 36 h, while tracking with commercial Lyso-Tracker Red under the same conditions was limited to 3 h. Our work demonstrated the possibility of constructing novel gold(I) sulfido clusters supported by special P-N hybrid ligands and the potential application of these clusters as long-term selective trackers of lysosomes in bioimaging.

New Pt→M (M = Ag or Tl) complexes based on anionic cyclometalated Pt(ii) complexes

Anionic cyclometalated complexes (NBu₄)[Pt(CNC)X] (X = Cl (1), CN (2), or S-2py (pyridine-2-thiolate) (3); -CNC- = 2,6-di(phen-2-ide)-pyridine) have been used as precursors in the synthesis of heteropolynuclear Pt-Ag or Pt-Tl complexes containing donor-acceptor metal-metal bonds. Their reaction with AgClO₄ or [Ag(OClO₃)(PPh₃)] produces complexes in which the nuclearity and structure seem to be determined by the ability of the ligand X to form bridges between the metals. Thus, the characteristic linear bridging of the cyano ligand leads to the formation of an octanuclear [{Pt(CNC)(μ-CN)}₄Ag₄] (4) or tetranuclear [{Pt(CNC)(μ-CN)}₂{Ag(PPh₃)}₂] (6) complex, with CN bridges between different "Pt-Ag" units. However, the S-2py ligand can act as a bridge between Pt and Ag of the same "Pt-Ag" unit, giving rise to the complex [{Pt(CNC)(S-2py)}₂Ag₂]·CH₂Cl₂ (5). On the other hand, the reaction of 1-3 with TlPF₆ yields the complexes [PtTl(CNC)Cl] (7), [PtTl(CNC)(CN)] (8), and (NBu₄)[{Pt(CNC)(S-2py)}₂Tl] (9), while with [Tl(S-2py)], [PtTl(CNC)(S-2py)] (10) is obtained. The structures of all these Pt-Tl complexes show great variation, with several geometric arrangements which sometime co-exist in the same crystal structure: discrete Pt-Tl, Pt-Tl-Pt and Pt-Tl-Pt-Tl units, as well as infinite Pt-Tl-Pt-Tl chains. This variability could be due to the lability of the Pt-Tl bonds and the ability of the thallium center to establish secondary interactions with donor atoms or aromatic π electron density from neighboring moieties.

Polymerization Isomerism in [{MFe(CO)4} n] n- (M = Cu, Ag, Au; n = 3, 4) Molecular Clusters Supported by Metallophilic Interactions

Triangular clusters [{MFe(CO)₄}₃]^3- (M = Cu, 4; Ag, 5; Au, 6) were selectively obtained by heating Fe(CO)₄(MIMes)₂ (M = Cu, 1; Ag, 2; Au, 3; IMes = C₃N₂H₂(C₆H₂Me₃)₂). 1-3 were synthesized by reacting Na₂[Fe(CO)₄]·2thf with 2 equiv of M(IMes)Cl. As previously described, the direct reactions of Na₂[Fe(CO)₄]·2thf with one equivalent of M(I) salts resulted in the triangular cluster [{CuFe(CO)₄}₃]^3- for Cu, whereas the square clusters [{MFe(CO)₄}₄]^4- were formed for Ag and Au. Thus, depending on the synthetic protocol adopted, both the triangular [{MFe(CO)₄}₃]^3- and square [{MFe(CO)₄}₄]^4- polymerization isomers can be selectively obtained, at least for Ag and Au. Polymerization isomerism, that is two compounds having the same elemental compositions but different molecular weights, was investigated in [{MFe(CO)₄} _n] ^n- ( n = 3, 4; M = Cu, Ag, Au) by means of structural and theoretical methods and the role of metallophilic interactions was computationally studied by means of the atoms-in-molecules (AIM) approach.

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.

Polynuclear Cu(i) and Ag(i) phosphine complexes containing multi-dentate polytopic ligands: syntheses, crystal structures and photoluminescence properties

A series of polynuclear metal complexes, [Cu2(L1)(PPh3)4](ClO4)2 (1), [Cu3(L2)(PPh3)6](ClO4) (2), [Cu3(L3)(PPh3)6] (3), [Ag2(L1)(PPh3)4](BF4)2 (4), [Ag4(L2)2(PPh3)6] (5) and [Ag3(L3)(PPh3)5] (6), have been obtained from the reactions of the highly conjugated bridging ligands 2,3-bis(2-pyridyl)pyrazine (L1), 2,3-bis(2-tetrazoyl)pyrazine (H2L2) and 2,3-bis(2-tetrazoyl)imidazole (H3L3) with [Cu(MeCN)4]ClO4 and AgBF4, respectively. Their crystal structures have been determined by X-ray crystallography and their photophysical properties have been investigated in detail. Complexes 1 and 3 show photoluminescence in CH2Cl2 solution, while all the complexes exhibit obvious luminescence in the solid state; detailed photophysical studies and density functional theory calculations of these complexes have revealed that their lowest energy absorptions and emissions are predominantly derived from either metal-to-ligand charge-transfer (MLCT) or intraligand (IL) excited states.

The reactivity of CO on bimetallic Ni3M clusters (M = Sc, Ti, V, Cr, Mn, Fe, Co, Cu, Rh, Ru, Ag, Pd and Pt) by density functional theory

Surface C and O overlap with bimetallic clusters in σ, π and δ-type bonding; for example, C is a σ-donor at −15.23 eV and a π-donor at −9.29 eV, and O is a δ-acceptor at −7.76 eV in Ni₃Fe clusters.

A 2D layer network assembled from an open dendritic silver cluster Cl@Ag11N24 and an N-donor ligand

A 2D layer network was synthesized from an N-donor ligand and a new silver cluster featuring an open dendritic structure with a high coordination ratio of N atom. Both the assembly process and luminescence properties of this complex was studied.

Water soluble cadmium selenide quantum dots for ultrasensitive detection of organic, inorganic and elemental mercury in biological fluids and live cells

CdSe QDs fluorescence is highly selective and sensitive to mercury.

Pyridylphosphine supported Ag(i) and Cu(i) complexes for detection of alcohols and nitriles via structural transformations from 1D to 0D

One-dimensional chain Ag(i) and Cu(i) complexes exhibit vapochromic luminescence for the detection of alcohols and nitriles via structural transformations from 1D to 0D.

Aurophilicity in action: stepwise formation of dinuclear Au(i) macrocycles with rigid 1,8-dialkynylanthracenes

1,8-Bis(gold(i)-ethynyl)anthracene units find stabilisation by maximising aurophilic contacts under formation of macrocyclic anions linked to cationic gold(i) fragments.

Phosphine-substituted 1,2,3-triazoles as P,C- and P,N-ligands for photoluminescent coinage metal complexes

A series of homo- and hetero-polynuclear coinage metal complexes based on a phosphine-substituted 1,2,3-triazole system was synthesized.

Luminescence mechanochromism of copper iodide clusters: a rational investigation

A photoluminescent copper iodide cluster has been characterized, and its luminescence mechanochromic properties have been anticipated.

Carba-closo-dodecaboranylethynyl ligands facilitating luminescent reversed charge-transfer excited states in gold/silver complexes

Homo- and heterometallic gold(i) and silver(i) complexes with the carba-closo-dodecaboranylethynyl ligand were obtained and the participation of the boron cluster to the photophysical properties was proven.

Intermolecular hydrogen bonding H···Cl in crystal structure of palladium(II)-bis(diaminocarbene) complex

The reaction of bis(isocyanide)palladium complex cis-[PdCl2(CNXyl)2] (Xyl=2,6-Me2C6H3) with excess of 4,5-dichlorobenzene-1,2-amine in a C2H4Cl2/MeOH mixture affords monocationic bis(diaminocarbene) complex cis-[PdClC{(NHXyl)=NHC6H2Cl2 NH2}{C(NHXyl)=NHC6H2Cl2NH2}]Cl (3) in moderate yield (42%). Complex 3 exists in the solid phase in the H-bonded dimeric associate of two single charged organometallic cations and two chloride anions according to X-ray diffraction data. The Hirshfeld surface analysis for the X-ray structure of 3 reveals that the crystal packing is determined primarily by intermolecular contacts H–Cl, H–H, and H–C. The intermolecular hydrogen bonds N–H···Cl and C–H···Cl in the H-bonded dimeric associate of 3 were studied by DFT calculations and topological analysis of the electron density distribution within the framework of QTAIM method, and estimated energies of these supramolecular contacts vary from 1.6 to 9.1 kcal/mol. Such non-covalent bonding means that complex 3 is an anionic receptor for the chloride anions.

Syntheses and Structures of d10 Coinage Metal Complexes of Electron-Accepting Phosphine Ligands Featuring a 3,3,4,4,5,5-Hexafluorocyclopentene Framework

Cu(I), Ag(I), and Au(I) complexes of monophosphine or bisphosphine ligands based on the 3,3,4,4,5,5-hexafluorocyclopentene skeleton were synthesized and structurally characterized by X-ray crystallographic analysis. The electron-withdrawing nature of these polyfluorinated phosphines was experimentally revealed via UV/vis absorption studies and crystal structure analysis. Successful catalytic application of the Au(I) complex for alkyne hydration reactions was investigated.

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.

A unique tetranuclear Ag(i) complex emitting efficient thermally activated delayed fluorescence with a remarkably short decay time

A novel tetranuclear Ag(i) complex, [Ag4(μ-DMPTP)2(POP)3][BF4]2 (Ag4N2P3), has been designed to achieve highly efficient thermally activated delayed fluorescence (TADF). Photophysical investigations show that the compound exhibits highly efficient TADF (Φ = 76%) and has a very short ambient-temperature TADF decay time of only 0.65 μs, corresponding to a radiative decay rate of k = Φ/τ = 1.2 × 106 s-1, a value belonging to the fast radiative rates in TADF materials.

Evaluation of Ligands Effect on the Photophysical Properties of Copper Iodide Clusters

Luminescent materials based on copper complexes are currently receiving increasing attention because of their rich photophysical properties, opening a wide field of applications. The copper iodide clusters formulated [Cu₄I₄L₄] (L = ligand), are particularly relevant for the development of multifunctional materials based on their luminescence stimuli-responsive properties. In this context, controlling and modulating their photophysical properties is crucial and this can only be achieved by thorough understanding of the origin of the optical properties. We thus report here, the comparative study of a series of cubane copper iodide clusters coordinated by different phosphine ligands, with the goal of analyzing the effect of the ligands nature on the photoluminescence properties. The synthesis, structural, and photophysical characterizations along with theoretical investigations of copper iodide clusters with ligands presenting different electronic properties, are described. A method to simplify the analysis of the ³¹P solid-state NMR spectra is also reported. While clusters with electron-donating groups present classical luminescence properties, the cluster bearing strong electron-withdrawing substituents exhibits original behavior demonstrating a clear influence of the ligands properties. In particular, the electron-withdrawing character induces a decrease in energy of the unoccupied molecular orbitals, that consequently impacts the emission properties. The modification of the luminescence thermochromic properties of the clusters are supported by density functional theory (DFT) calculations. This study demonstrates that the control of the luminescence properties of these compounds can be achieved through modification of the coordinated ligands, nevertheless the role of the crystal packing should not be underestimated.

Metal complexes with oxygen-functionalized NHC ligands: synthesis and applications

Ligand design has met with considerable success with both categories of hybrid ligands, which are characterized by chemically different donor groups, and of N-heterocyclic carbenes (NHCs). Their spectacular development and diversity are attracting worldwide interest and offers almost unlimited diversity and potential in e.g. coordination/organometallic main group and transition metal chemistry, catalysis, medicinal chemistry and materials science. This review aims at providing a comprehensive update on a specific class of ligands that has enjoyed much attention in the past few years, at the intersection between the two categories mentioned above, that of hybrid NHC ligands in which the functionality associated with the carbene donor is of the oxygen-donor type. For each type of oxygen-donor present in such chelating (Section 1) or bridging (Section 2) hybrid ligands, we will examine the synthesis, structures and reactivity of their metal complexes and their applications, with a special focus on homogeneous catalysis (Section 3). Thus, hydrogenation, C-H bond activation, C-C, C-N, C-O bond formation, hydrolysis of silanes, oligomerization, polymerization, metathesis, hydrosilylation, C-C bond cleavage, acceptorless dehydrogenation, dehalogenation/hydrogen transfer, oxidation and reduction reactions will be successively presented in a tabular manner, to facilitate an overview and a rapid identification of the relevant publications describing which metals associated with a given oxygen functionality are most suitable. The literature coverage includes the year 2015.

Intra-/Intermolecular Bifurcated Chalcogen Bonding in Crystal Structure of Thiazole/Thiadiazole Derived Binuclear (Diaminocarbene)PdII Complexes

The coupling of cis-[PdCl2(CNXyl)2] (Xyl = 2,6-Me2C6H3) with 4-phenylthiazol-2-amine in molar ratio 2:3 at RT in CH2Cl2 leads to binuclear (diaminocarbene)PdII complex 3c. The complex was characterized by HRESI+-MS, 1H NMR spectroscopy, and its structure was elucidated by single-crystal XRD. Inspection of the XRD data for 3c and for three relevant earlier obtained thiazole/thiadiazole derived binuclear diaminocarbene complexes (3a EYOVIZ; 3b: EYOWAS; 3d: EYOVOF) suggests that the structures of all these species exhibit intra-/intermolecular bifurcated chalcogen bonding (BCB). The obtained data indicate the presence of intramolecular S•••Cl chalcogen bonds in all of the structures, whereas varying of substituent in the 4th and 5th positions of the thiazaheterocyclic fragment leads to changes of the intermolecular chalcogen bonding type, viz. S•••π in 3a,b, S•••S in 3c, and S•••O in 3d. At the same time, the change of heterocyclic system (from 1,3-thiazole to 1,3,4-thiadiazole) does not affect the pattern of non-covalent interactions. Presence of such intermolecular chalcogen bonding leads to the formation of one-dimensional (1D) polymeric chains (for 3a,b), dimeric associates (for 3c), or the fixation of an acetone molecule in the hollow between two diaminocarbene complexes (for 3d) in the solid state. The Hirshfeld surface analysis for the studied X-ray structures estimated the contributions of intermolecular chalcogen bonds in crystal packing of 3a–d: S•••π (3a: 2.4%; 3b: 2.4%), S•••S (3c: less 1%), S•••O (3d: less 1%). The additionally performed DFT calculations, followed by the topological analysis of the electron density distribution within the framework of Bader’s theory (AIM method), confirm the presence of intra-/intermolecular BCB S•••Cl/S•••S in dimer of 3c taken as a model system (solid state geometry). The AIM analysis demonstrates the presence of appropriate bond critical points for these interactions and defines their strength from 0.9 to 2.8 kcal/mol indicating their attractive nature.

A stable thiolato-CuI-thiolato triple linkage that bridges two cobalt(iii) centres

Treatment of Λ-fac-[Co(d-pen-N,S)₃]^3- (d-H₂pen = d-penicillamine) with Cu⁺ in water gave a stable CoCu complex, ΛΛ-[Co₂Cu₃(d-pen)₆]^3- ([1]^3-), having three thiolato-copper(i)-thiolato moieties that bridge two cobalt(iii) centres. Complex [1]^3- was isolated as a coordination polymer of Na₃[1], which was converted to a complex salt of [Cr(H₂O)₆][1] by treatment with Cr(NO₃)₃.

Relevance of Orbital Interactions and Pauli Repulsion in the Metal-Metal Bond of Coinage Metals

The importance of relativity and dispersion in metallophilicity has been discussed in numerous studies. The existence of hybridization in the bonding between closed shell d¹⁰–d¹⁰ metal atoms has also been speculated, but the presence of attractive MO interaction in the metal–metal bond is still a matter of an ongoing debate. In this comparative study, a quantitative molecular orbital analysis and energy decomposition is carried out on the metallophilic interaction in atomic dimers (M⁺···M⁺) and molecular perpendicular [H₃P–M–X]₂ (where M = Cu, Ag, and Au; X = F, Cl, Br, and I). Our computational studies prove that besides the commonly accepted dispersive interactions, orbital interactions and Pauli repulsion also play a crucial role in the strength and length of the metal–metal bond. Although for M⁺···M⁺ the orbital interaction is larger than the Pauli repulsion, leading to a net attractive MO interaction, the bonding mechanism in perpendicular [H₃P–M–X] dimers is different due to the larger separation between the donor and acceptor orbitals. Thus, Pauli repulsion is much larger, and two-orbital, four-electron repulsion is dominant.

Attract and repel: Our computational studies on the metallophilic interaction in atomic dimers (M⁺···M⁺) and molecular perpendicular [H₃P−M−X]₂ (where M = Cu, Ag, and Au; X = F, Cl, Br, and I) prove that besides the commonly accepted dispersive interactions attractive and repulsive MO interactions play a crucial role in metallophilicity.

Reactivity Toward Ag+: A General Strategy to Generate a New Emissive Center from NIR-Emitting Gold Nanoparticles

We report a facile strategy for the transformation of single NIR-emitting AuNPs to dual-NIR-emitting bimetallic Ag@AuNPs based on the robust reactivity toward Ag(I) ions under mild conditions. The reactivities toward Ag(I) ions were found to be significantly different between visible- and NIR-emitting glutathione (GSH)-coated AuNPs: the high GSH surface coverage on the 610 nm-emitting AuNPs resulted in a reversible interaction due to enough surface steric hindrance to resist Ag(I) ions from interaction with the Au(0) core, whereas the low GSH surface coverage on the 810 nm-emitting AuNPs led to both antigalvanic reaction and Ag(I)-carboxylate shell formation on the surface of the AuNPs, which were responsible for the formation of a new emissive center at 705 nm. This strategy was also demonstrated to exhibit excellent generalization toward various NIR-emitting AuNPs with surface chemistries containing carboxyl groups, opening a new pathway of tailoring the optical properties of metallic NPs through surface reactivity.