Ag Interactions Research Articles

Mechanism of the Palladium-Catalyzed C(sp3)–H Arylation of Aliphatic Amines: Unraveling the Crucial Role of Silver(I) Additives

DFT calculations have been combined with experiments to study the mechanism of γ-C(sp3)–H arylation of aliphatic amines promoted by palladium–glyoxylic acid cooperative catalysis, with a focus on the role of silver(I) additives. Glyoxylic acid (the cocatalyst) uses its aldehyde functionality to react with the amine substrate to form an iminoacetic acid. This acid acts as a transient directing reagent and metathesizes with Pd(OAc)2 (the precatalyst) to give a Pd(II)–diiminoacetate five-membered chelate, which has been shown computationally as the catalyst resting state and which has been experimentally synthesized and characterized. C(sp3)–H activation from the Pd(II)–diiminoacetate complex or its mononuclear derivatives would face a high kinetic barrier (>30 kcal/mol) arising mainly from breaking a stable five-membered N,O-chelate ring. The crucial role of the silver(I) carboxylate additive is in reacting with the Pd(II)–diiminoacetate complex to provide a heterodimeric Pd(II)–Ag(I) complex supported by bridging chelators and intermetallic Pd–Ag interaction, which would lead to a C(sp3)–H activation transition state with a considerably lower barrier (∼25 kcal/mol). The Pd(II)–Ag(I) complex has been detected by mass spectrometry, which provides the first experimental evidence of a Pd–Ag-containing active species in Pd-catalyzed C–H activation reactions using Ag(I) additives. After C(sp3)–H activation, the reaction proceeds through oxidative addition of Pd(II) and reductive elimination from Pd(IV) completing C–C formation, followed by ligand exchange to regenerate the catalyst resting state and release the arylated iminoacetic acid which continues on hydrolysis to give the final amine product and regenerate the glyoxylic acid cocatalyst. The computational and experimental findings taken together provide new mechanistic insight into the broad range of palladium-catalyzed C–H activation reactions that use silver(I) additives.

Electronic properties of OH–CNT–Ag composite: a combined first-principles and experimental study

Carbon nanotube-based silver (CNT–Ag) composite has recently proved to be a sensing material due to the excellent electrical characteristics and is being considered as one of the promising sensing material candidates for flexible strain sensors. However, understanding the effect of interaction ways between Ag and CNT on conductivity is limited. Based on first-principles calculations, it was studied and compared that whether the presence of hydroxyl group affects the electronic properties of CNT–Ag for the first time. The results give an explanation for that the hydroxyl group increases the interaction of Ag and CNT, which makes conductivity better while silver clusters are often formed stably with even-number atoms. The corresponding experiment further demonstrates that silver nanoparticles (Ag NPs) are relatively dispersed uniformly and bind to CNT tightly in hydroxyl-functionalized CNT (OH–CNT). Meanwhile, the conductivity of the CNT–Ag composite improves by 95.81% with OH–CNT compared to that without OH–CNT, which confirms the calculated results. The present work provides a theoretical guide for preparing highly conductive CNT–Ag composite and would promote the application of functionalized CNT in the field of sensors’ sensing materials.

A 3D inorganic-organic hybrid constructed from Strandberg-type polyoxometalates and silver complexes: Synthesis, structure and properties

A 3D Strandberg-type polyoxometalate-based inorganic-organic hybrid, [Ag4(H3L)2(P2Mo5O23)]·H2O (1) (H2L = 2,6-dimethyl-3,5-bis(pyrazol-3-yl)pyridine), has been synthesized under hydrothermal conditions and structurally characterized by single crystal X-ray diffraction, elemental analysis, IR, TG and powder X-ray diffraction. In compound 1, the adjacent [P2Mo5O23]6− clusters are linked by Ag1 into a 2D layer with left- and right-handed helical chains. And the layers are further linked together through organic ligands H2L and Ag⋯Ag interactions into a 3D framework with 1D channels extended along c axis. The luminescence, electrochemical properties and photocatalytic activities of compound 1 have also been investigated.

A DFT study on N-6-amino-hexylamide functionalized single-walled carbon nanotubes in interaction with silver ion in a gaseous environment

In this study, quantum mechanical calculations, such as density functional theory (DFT), have been employed to determine the active positions of nanosensor and thermodynamics functions of interaction between Ag+ and nanosensor have been calculated. HOMO and LUMO energies and energy difference between donor atoms (i) and acceptor atoms (j) have been evaluated. In addition, the effect of the number of substitution agents on the reactivity of the functional carbon nanotubes and the charge on the interacting atoms and Ag+ before and after interaction have been investigated. The geometry optimization and theoretical calculations have been carried out using B3LYP level of theory. Results show that the interaction of Ag+ with nanosensor is in terms of thermodynamically possible. The negative values of ΔG° denote a spontaneous reaction and the negative values of ΔH° represent an exothermic reaction. In addition, the nanosensor has two active positions and the product obtained through the interaction between Ag+ and oxygen of the carbonyl group is the most stable state. The interaction of Ag+ with the nanosensor is accompanied by a reduction in the energy gap (Eg) which increases the stability of the complex, causes indicating that a charge transfer occurred between the nanosensor and Ag+.

Replacing Mercury: Syntheses of Lanthanoid Pyrazolates from Free Lanthanoid Metals, Pentafluorophenylsilver, and Pyrazoles, Aided by a Facile Synthesis of Polyfluoroarylsilver Compounds

The polyfluorophenylsilver complexes [Ag2(C6F4Br‐4)2(py)3] (py = pyridine) (1) and [{Ag2R2(py)2}n] [R = C6F5 (2); C6F4Br‐3 (3); C6F4H‐4 (4)] were prepared in reasonable yields by reactions of silver(I) oxide with the appropriate polyfluorobenzenes in pyridine. This simple and convenient synthesis is selective and does not lead to debromination of C6HF4Br‐(3 or 4). Complex 1 is dinuclear with AgR2 and Ag(py)3 units linked by a bridging polyfluoroaryl group and Ag···Ag interactions, whereas 2–4 are polymeric with alternating AgR2 and Ag(py)2 units similarly linked. The trivalent lanthanoid pyrazolates, [Ln(Ph2pz)3(py)2]·2thf (Ph2pz = 3,5‐diphenylpyrazolate; Ln = Yb, 5, Er, 6, Dy, 7, Lu, 8; thf = tetrahydrofuran), [Ho(Ph2pz)3(py)(thf)] (9), [Ln(Ph2pz)3(py)(dme)]·solv (Ln = Tb, solv = 1.75PhMe, 10, Gd, solv = 1.5dme, 11; dme = 1,2‐dimethoxyethane; PhMe = toluene), [Ln(Ph2pz)3(thf)3] (Ln = La, 12, Ce, 13, Nd, 14), [Ln(tBu2pz)3(py)2] (tBu2pz = 3,5‐di‐tert‐butylpyrazolate; Ln = Yb, 15, Tm, 16, Ho, 17, Dy, 18), [Yb(Phtpz)3(py)2]·PhMe (19) (Phtpz = 3‐Phenyl‐5‐(2′‐thienyl)pyrazolate) and [Nd(ttfpz)3(dme)2] (20) (ttfpz = 3‐(2′‐thienyl)‐5‐(trifluoromethyl)pyrazolate) have been prepared by redox transmetallation/protolysis (RTP) reactions employing lanthanoid metals, pentafluorophenylsilver and the corresponding pyrazoles (pzH) in donor solvents. This is a new synthetic route in which AgC6F5 replaces the more commonly used Hg(C6F5)2 or HgPh2. Yields are good to excellent if long crystallization times are used but the heavier Ln metals require activation with iodine to induce reaction. The monomeric structures exhibit η2‐bound pyrazolate ligands with eight‐coordinate metal atoms for complexes 5–9 and 15–19, nine‐coordinate metal atoms for complexes 10–14, and ten‐coordinate metal atoms for complex 20.

Synthesis and Structural Characterization of a Series of One-Dimensional Heteronuclear Dirhodium-Silver Coordination Polymers.

Herein, we describe the preparation of heteronuclear dirhodium-silver complexes by reaction between molecular Rh(II)-Rh(II) compounds [Rh2(μ-O2CR)4L2] (R = Me, Ph (1), CH2OEt (2); L = solvent molecules) with paddlewheel structure and PPh4[Ag(CN)2]. One-dimensional coordination polymers of (PPh4)n[Rh2(μ-O2CR)4Ag(CN)2]n (R = Me (3), Ph (4), CH2OEt (5)) formula have been obtained by replacement of the two labile molecules in the axial positions of the paddlewheel structures by a [Ag(CN)2]− bridging unit. The crystal structures of 3–5 display a similar arrangement, having anionic chains with a wavy structure and bulky (PPh4)+ cations placed between the chains. The presence of the (PPh4)+ cations hinders the existence of intermolecular Ag-Ag interactions although several C-H····π interactions have been observed. A similar reaction between [Rh2(μ-O2CCMe3)4(HO2CCMe3)2] and PPh4[Ag(CN)2] led to the molecular compound (PPh4)2{Rh2(μ-O2CCMe3)4[Ag(CN)2]2} (6) by replacement of the axial HO2CCMe3 ligands by two [Ag(CN)2]− units. The trimethylacetate ligand increases the solubility of the complex during the crystallization favouring the formation of discrete heteronuclear species.

4-Pyridylisocyanide gold(i) and gold(i)-plus-silver(i) luminescent and mechanochromic materials: the silver role.

Crystallographic and DFT examination of the metalloligands [AuAr(CNPy-4)] (Ar = C6F5 (1), C6F3Cl2-3,5 (2)) and their silver complexes [Ag[AuAr(CNPy-4)]2](BF4) (3 and 4) support that the marked luminescence red-shifts observed on moving from 1 to 2, from 1,2 to 3,4, or upon grinding, are not caused by electronic differences (either by changing the aryls C6F5/C6F3Cl2, or by N coordination to silver), nor by non-existent AuAg interactions. They are always due to structural changes disturbing stronger π-π stackings in order to allow for shorter AuAu interactions.

Crystal Structures and Cytotoxicity of Four Silver(I)carboxylate Complexes with 1,2-Ethylenediamine Analogues

Four silver(I) compounds, [Ag(dapn)(dnbc)]n·1.5nH2O (1), [Ag(en)]n[Ag(dnbc)2]n·2nH2O (2), [Ag(en)]n[Ag(nbc)2]n·2nH2O (3) and [Ag(dapn)]n -(nbc)n·2nH2O (4), where dapn = 1,2-diaminopropane, dnbc = 3,5-dinitrobenzoate, en = 1,2-diaminoethane and nbc = 4-nitrobenzoate, have been synthesized and characterized by X-ray diffraction. The Ag(I) ions show T-shaped coordination geometry in compound 1 but linear coordination geometry in compounds 2, 3 and 4. There are ligand-unsupported Ag…Ag interaction in compounds 2 and 3 with Ag…Ag distance of 3.177 ~3.267 Å. All the four complexes showed high cytotoxicity properties.

Emerging investigator series: characterization of silver and silver nanoparticle interactions with zinc finger peptides.

In biological systems, chemical and physical transformations of engineered silver nanomaterials (AgENMs) are mediated, in part, by proteins and other biomolecules. Metalloprotein interactions with AgENMs are also central in understanding toxicity and antimicrobial and resistance mechanisms. Despite their readily available thiolate and amine ligands, zinc finger (ZF) peptides have thus far escaped study in reaction with AgENMs and their Ag(I) oxidative dissolution product. We report spectroscopic studies that characterize AgENM and Ag(I) interactions with two ZF peptides that differ in sequence, but not in metal binding ligands: the ZF consensus peptide CP-CCHC and the C-terminal zinc finger domain of HIV-1 nucleocapsid protein p7 (NCp7_C). Both ZF peptides catalyze AgENM (10 and 40 nm, citrate coated) dissolution and agglomeration, two important AgENM transformations that impact bioreactivity. AgENMs and their oxidative dissolution product, Ag(I)(aq), mediate changes to ZF peptide structure and metalation as well. Spectroscopic titrations of Ag(I) into apo-ZF peptides show an Ag(I)-thiolate charge transfer band, indicative of Ag(I)-ZF binding. Fluorescence studies of the Zn(II)-NCp_7 complex indicate that the Ag(I) also effectively competes with the Zn(II) to drive Zn(II) displacement from the ZFs. Upon interaction with AgENMs, Zn(II) bound ZF peptides show a secondary structural change in circular dichroism spectroscopy toward an apo-like structure. The results suggest that Ag(I) and AgENMs may alter ZF protein function within the cell.

Bis(6-diphenylphosphinoacenaphth-5-yl)telluride as a ligand toward coinage metal chlorides

The use of bis(6-diphenylphosphinoacenaphth-5-yl)tellurium (6-Ph2P-Ace-5-)2Te (6) as a ligand for complex formation reactions with CuCl and AgCl is reported, giving rise to the formation of 1 : 1 complexes (6-Ph2P-Ace-5-)2Te·CuCl (7) and (6-Ph2P-Ace-5-)2Te·AgCl (8). The reaction of 6 with (tht)AuCl or (CO)AuCl failed to provide the analogous complex (6-Ph2P-Ace-5-)2Te·AuCl (9), but gave the recently reported (6-diphenylphosphinoacenaphth-5-yl)gold dimer (6-Ph2P-Ace-5-Au)2 (10) and (6-diphenylphosphinoacenaphth-5-yl)tellurenyl chloride, (6-Ph2P-Ace-5-Te)Cl (11). The reaction of 6, 7 and 8 with PhICl2 provided diarylchlorotelluronium chloride [(6-Ph2P-Ace-5-)2TeCl]Cl (12). Compounds 7, 8 and 12 were characterized by multinuclear NMR spectroscopy and single-crystal X-ray crystallography. DFT computations of 6, 7, 8, [(6-Ph2P-Ace-5-)2TeCl]+ (12') and [(8-Me2N-Nap-1-)2TeCl]+ (13') were carried out including a variety of real-space bonding indicators (RSBI) derived from the Atom-In-Molecules (AIM) and the Electron Localizability Indicator (ELI-D) space partitioning schemes. Furthermore, the non-covalent interaction (NCI) index was applied to examine the nature of the Te-X interactions (X = Cu, Ag, P, N, Cl) and complement the AIM and ELI-D approaches.

Structural exploration of viral matrix protein 40 interaction with the transition metal ions (Ag+ and Cu2+)

Here, a theoretical and comprehensive study of the structural features and interaction properties of viral protein 40 is being briefed out to understand the mechanism of Ebola virus (EV) with structural and orbital analysis. In general, viral protein 40 is the key protein for the oligomerization, the N-terminal loop region in the viral protein 40 and it is essential for the viral replication in Ebola. The electronic structures of native N-terminal loop (His124-Asn134) and metalized (Mn+=Ag+ and Cu2+) complexes are optimized at the M06-2X/LANL2DZ level of theory. Among Mn+-interacted N-loop complexes, Cu2+-interacted N-terminal loop complex has the highest interaction energy of –973.519 kcal/mol and also it has the stabilization energy in the range of 9.92 kcal/mol. The cation-π interactions between His124, Pro131 and Arg134 residues are the important factor, which enhances the interaction energy of viral protein 40. Due to the chelation behavior of metal ions, the backbone and the side chains of N-terminal loop regions are deviated from the planarity that results in the formation of classical hydrogen bonds between N-terminal loop regions. Molecular dynamics simulation studies also revealed that the structural transformations of Nloop into a stable α-helix and β-sheet folded conformations due to the interaction of Ag+ and Cu2+ ions in the N-terminal loop region. The hydrogen bond formation and hydrophobic interactions are responsible for the stability and structural changes in N-terminal loop region. Therefore, it is clear that interaction of metal ion with viral protein-40 reduces the replication of the disease by inducing the secondary structural changes.Communicated by Ramaswamy H. Sarma

Smart Transformation of a Polyhedral Oligomeric Silsesquioxane Shell Controlled by Thiolate Silver(I) Nanocluster Core in Cluster@Clusters Dendrimers.

Using polyhedral oligomeric silsesquioxane (POSS) modified by a thiol group as a protected ligand, atom-precise multi-heteorocluster-based dendrimers Ag12 @POSS6 (1 a and 1 b) were assembled. Through the reactive -SH groups, six POSS shell ligands stabilize the central 12-core silver(I) cluster by diverse Ag-S interactions. When such Ag12 @POSS6 complex was stimulated by different solvents (acetone or tetrahydrofuran), the core Ag12 silver(I) cluster underwent reversible structural transformation between flattened cubo-octahedral (in 1 a) and normal cubo-octahedral (in 1 b); concomitantly shell POSS clusters rearranged from pseudo-octahedral to quasi-octahedral. Furthermore, the film matrix modified by 1 a or 1 b showed different hydrophobicity.

The Influence of Physical properties on the Antibacterial Activity of Lysine Conjugated Chitosan Functionalized Silver Nanoparticles

The antibacterial activity of chitosan/lysine/silver (Cht/lys/Ag) on pathogens was influenced by physical properties and morphology to a higher degree compared with that of chitosan/silver (Cht/Ag). The antibacterial activity of Cht/Ag and Cht/lys/Ag were evaluated against pathogens Gram negative (E. coli and P. aeruginosa) and Gram positive bacteria (S. aureus and B. subtilis) by Kirby Bauer disk diffusion assay method. Crystallite size values of the synthesized system was calculated from XRD analysis to study their dependency on antibacterial activity. The FTIR spectral analysis shows the presence of -OH and COO- groups of Cht and lys and the variation in intensities confirmed the interaction with Ag nanoparticles which are stabilized. Moreover, UV–Vis results show that the Cht/lys/Ag composition enhanced the stability and induced the symmetry of Ag nanoparticles which were observed from surface plasmon resonance (SPR) effect of Cht/lys/Ag. In addition, the induced higher symmetry, low hydrodynamic diameter and higher diffusion coefficient from dynamic light scattering (DLS) measurement of Cht/lys/Ag were found to yield maximum bacterial inhibition than Cht/Ag which were due to lysine interaction. Obviously surface morphological changes in the composites are due to Ag and lysine interaction as seen from SEM micrographs. The synthesized NCs exhibit efficient antipathogens against Gram negative bacteria and are promising candidates in diverse applications in biomedical industries.

A new modification of [Ag4Br4(PPh3)4]: synthesis, structure and properties

Abstract A new modification of the homometallic silver(I) cluster [Ag4Br4(PPh3)4] has been prepared and characterized by elemental analysis, UV/Vis and IR spectroscopy, and X-ray crystallography. The tetramer shows a polycyclic structure with a chair conformation. The bromine atoms adopt μ 2- and μ 3-bridging modes. The shortest Ag–Ag distance in the cluster is 3.159(2) Å, which indicates significant Ag–Ag interactions. A supramolecular structure is arranged by hydrogen bonds (C–H···Br). Cyclic voltammograms of the cluster indicate a quasi-reversible Ag+/Ag couple. The fluorescence properties of the ligand and the Ag(I) cluster were studied in the solid state. The emission peaks of the Ag(I) cluster are attributed to ligand-centered luminescence.

Qualified Biolayer Interferometry Avidity Measurements Distinguish the Heterogeneity of Antibody Interactions with Plasmodium falciparum Circumsporozoite Protein Antigens.

Ab avidity is a measure of the overall strength of Ab–Ag interactions and hence is important for understanding the functional efficiency of Abs. In vaccine evaluations, Ab avidity measurements can provide insights into immune correlates of protection and generate hypotheses regarding mechanisms of protection to improve vaccine design to achieve higher levels of efficacy. The commonly used Ab avidity assays require the use of chaotropic reagents to measure avidity index. In this study, using real-time detection of Ab–Ag binding by biolayer interferometry (BLI) technique, we have developed a qualified assay for measuring avidity of vaccine-induced Abs specific for Plasmodium falciparum circumsporozoite protein (CSP) Ags. Human mAb derived from plasmablasts of recipients of RTS,S/AS01 (RTS,S), the most advanced malaria vaccine candidate, were used in the assay development to measure Ag-specific binding responses and rate constants of association and dissociation. The optimized BLI binding assay demonstrated 1) good precision (percentage of coefficient of variation <20), 2) high specificity, 3) a lower limit of detection and quantitation in the 0.3–3.3 nM range, and 4) a range of linearity up to 50–100 nM for the CSP Ags tested. Analysis of polyclonal sera of malaria vaccinees demonstrated the suitability of this method to distinguish among vaccinees and rank Ab responses by avidity. These results demonstrate that precise, specific, and sensitive BLI measurements of Ab avidity in polyclonal sera from malaria vaccinees can map Ab response heterogeneity and potentially help to determine the role of Ab avidity as an immune correlate of protection for vaccines.

Theoretical modeling of argentophilic interactions in [Ag(CN)2−]3 trimer found in a copper(II) complex of cis-1,2-diaminocyclohexane (Dach), [Cu(Dach)2-Ag(CN)2-Cu(Dach)2][Ag(CN)2

Crystal structure study of a copper(II) complex of cis-1,2-diaminocyclohexane (Dach), [Cu(Dach)2-Ag(CN)2-Cu(Dach)2][Ag(CN)2]3 (1) reveals the presence of unsupported Ag⋯Ag⋯Ag interactions with the interatomic Ag⋯Ag distance of 3.230 Å. Detailed HF, MP2 and BLYP-D3 theoretical investigations of [Ag(CN)2−]3 trimer, together with AIM, NCI and EDA analyses verified these interactions as noncovalent AgAg bonds with the magnitude of a weak hydrogen bond, mainly electrostatically and dispersively driven.

First cyano-bridged coordination polymers based on N,N’-chelated Ag(I) ions and octahedral rhenium(III) chalcocyanide clusters exhibiting unusually long-lived photoluminescence

First examples of Ag(I)-containing coordination polymers based on octahedral rhenium(III) chalcocyanide clusters, namely [{Ag(bpy)}{Ag4(bpy)4(μ-CN)}{Re6Q8(CN)6}] (Q = S in 1 or Se in 2; bpy = 2,2′-bipyridine), have been hydrothermally synthesized and characterized by single-crystal X-ray diffraction, elemental and thermogravimetric analysis, EDS, IR and luminescence spectroscopy. The compounds are isostructural, crystallize in the orthorhombic system (space group Pccn, Z = 4) and possess a rigid 3D framework structure built up from {Re6Q8(CN)6}4– cluster anions and two distinct types of Ag(I)-containing cationic units, mononuclear {Ag(bpy)}+ and tetranuclear {Ag4(bpy)4(μ-CN)}3+, all of which are interconnected through cyanide bridging. The supramolecular structures of 1 and 2 are supported by argentophilic Ag⋯Ag interactions, but surprisingly show very limited π-π stacking of the pyridine rings. Both compounds are highly emissive in red region showing the longest lifetimes hitherto reported for the solid samples of hexarhenium cluster compounds.

Stabilization of Ag-Au Bimetallic Nanocrystals in Aquatic Environments Mediated by Dissolved Organic Matter: A Mechanistic Perspective.

Gold and silver nanoparticles can be stabilized endogenously within aquatic environments from dissolved ionic species as a result of mineralization induced by dissolved organic matter. However, the ability of fulvic and humic acids to stabilize bimetallic nanoparticles is entirely unexplored. Elucidating the formation of such particles is imperative given their potential ecological toxicity. Herein, we demonstrate the nucleation, growth, and stabilization of bimetallic Ag-Au nanocrystals from the interactions of Ag+ and Au3+ with Suwannee River fulvic and humic acids. The mechanisms underpinning the stabilization of Ag-Au alloy NPs at different pH (6.0-9.0) values are studied by UV-vis spectrophotometry, X-ray photoelectron spectroscopy (XPS), high-resolution transmission electron microscopy (HRTEM), and selected area electron diffraction (SAED). Complexation of free Ag+ and Au3+ ions with the Lewis basic groups (carbonyls, carboxyls, and thiols) of FA and HA, followed by electron-transfer from redox-active moieties present in dissolved organic matter initiates the nucleation of the NPs. Alloy formation and interdiffusion of Au and Ag atoms are further facilitated by a galvanic replacement reaction between AuCl4- and Ag. Charge-transfer from Au to Ag stabilizes the formed bimetallic NPs. A more pronounced agglomeration of the Ag-Au NPs is observed when HA is used compared to FA as the reducing agent. The bimetallic NPs are stable for greater than four months, which suggests the possible persistence and dispersion of these materials in aquatic environments. The mechanistic ideas have broad generalizability to reductive mineralization processes mediated by dissolved organic matter.

Ag/Cd coordination architecture and photoluminescence behaviors

Three coordination architectures, {[Ag4(pbmb)4·(BF4)4](CH3OH)2·H2O}n (1), {[Cd2(pbmb)4](ClO4)4·(CH3OH)5}n (2), and [Cd4(pbmb)4·I8(CH3OH)2]n (3) (pbmb = 1-((2-(pyridin-2-yl)-1H-benzoimidazol-1-yl)methyl)-1H-benzotriazole), are built up from Ag(I)/Cd(II) salts and a flexible pyridyl-benzimidazole-based organic spacer. Single-crystal analysis shows that 1 and 2 have 1-D chains, while 3 displays a tetranuclear structure. All complexes exhibit different coordination geometries and properties, which can be attributed to the difference between the metal centers or anions. In the case of 1 in particular, the Ag⋯Ag interactions play a crucial role in the formation of a supramolecular architecture. The binuclear-based complex consists of a pair of Ag⋯Ag contacts (ca. 2.953 Å), and it exhibits intense triplet emission with large Stokes shift and high thermal stability. Compared to pbmb, 2 has excellent high-energy fluorescence properties, while 1 and 3 exhibit mainly low-energy emission. Therefore, it can be concluded that the heavy atom effect has a causative influence in enhancing the triplet state radiative rate, resulting in large Stokes’ shift of the complex.

Role of Surface States in Silver-Doped CdSe and CdSe/CdS Quantum Dots

The effects of Ag doping of CdSe and CdSe/CdS quantum dots (QDs) have been studied as a function of the surface composition. Throughout these studies, static and time-resolved luminescence and transient absorption measurements are used to determine the nature and rates of radiationless decay mechanisms and how these vary with the concentration of Ag dopants. In tributylphosphine-ligated CdSe, the photoluminescence quantum yield (PL QY) varies nonmonotonically with dopant concentration, increasing at low concentrations of Ag+ then decreasing with further addition. The initial increase is assigned to the passivation of preexisting surface hole traps by interaction of interstitial Ag+ with surface Se2– ions, whereas the subsequent decrease is due to the introduction of substitutional Ag+ dopants, which act as a new source of hole traps. Ligation of the particle surface with alkyl amines largely passivates the surface hole traps and thereby eliminates the initial increase in PL QY upon doping. CdSe/CdS QDs li...