Molybdate-Templated Luminescent Silver Alkynyl Nanoclusters: Total Structure Determination and Optical Property Analysis.

Two novel MoO42--templated luminescent silver alkynyl nanoclusters with 20-nuclearity ([(MoO42-)@Ag20(C≡CtBu)8(Ph2PO2)7(tfa)2]·(tfa-) (1)) and 18-nuclearity ([(MoO42-)@Ag18(C≡CtBu)8(Ph2PO2)7]·(OH) (2)) (tfa = trifluoroacetate) were synthesized with the green light maximum emissions at 507 and 516 nm, respectively. The nanoclusters were investigated and characterized by single-crystal X-ray crystallography, electrospray ionization mass spectrum (ESI-MS), X-ray photoelectron spectroscopy, thermogravimetry (TG), photoluminescence (PL), ultraviolet-visible (UV-vis) spectroscopy, and density functional theory calculations (DFT). The two nanoclusters differ in their structure by a supplementary [Ag2(tfa)2] organometallic surface motif, which significantly participates in the frontier molecular orbitals of 1, resulting in similar bonding patterns but different optical properties between the two clusters. Indeed, both nanoclusters show strong temperature-dependent photoluminescence properties, which make them potential candidates in the fields of optical devices for further applications.

Template-Free Synthesis of Two New Luminescent One-Dimensional High-Nuclearity Silver Polyclusters.

The metallophilic properties, spherical configuration, and flexible coordination of silver ions make them prone to create various coordination modes and structural features. Therefore, with the increase of the complexities of self-assembly, the effect of various synthetic conditions in the final structure of silver compounds becomes diverse and attractive. In this study, two new silver polyclusters, 16- and 21-nuclearity, protected by multiple ligands including alkynyl, trifluoroacetate, and diphenylphosphinate, were synthesized and characterized by single-crystal X-ray diffraction, powder X-ray diffraction, and Fourier transform infrared (FTIR) spectroscopy. The optical properties and thermal stability of the polyclusters were studied by solid-state ultraviolet-visible (UV-vis) absorption and solid UV-vis diffuse reflectance spectra and gravimetric analysis, respectively. The formation of the two polyclusters can be fine-controlled by simply adjusting the stoichiometric ratio of diphenylphosphinate ligands to silver precursors under the same synthetic condition, leading to the different coordination modes between ligands and Ag centers. This work shows a facile and template-free method to synthesize and control the silver polycluster assembly, encouraging further development of new polyclusters with the potential for various applications.

Synthesis and Study of Photothermal Properties of a Mixed-Valence Nanocluster CuI/CuII with Strong near-Infrared Optical Absorption Supported by 4-tert-Butylcalix[4]arene Ligand.

The first mixed-valence nanocluster CuI/CuII with the highest percentage of CuII ions was synthesized by using 4-tert-butylcalix[4]arene (Calix4), with the formula DMF2⊂[(CO3)2-@CuII6CuI3(Calix4)3Cl2(DMF)5(H3O)]•DMF (1), as a photothermal nanocluster. Its structure was characterized using single-crystal X-ray diffraction, Fourier-transform infrared spectroscopy, and powder X-ray diffraction. In addition, the charge state and chemical composition of the nanocluster were determined using electrospray ionization spectrometry and X-ray photoelectron spectroscopy (XPS) spectrum. The results of the XPS and X-ray crystallography revealed that there are two independent CuII and CuI centers in nanocluster 1 with the relative abundances of 66.6 and 33.3% for CuII and CuI, respectively. The nanocluster contains three four-coordinated CuI ions with a square-planar geometry and six five-coordinated CuII ions with a square pyramid geometry. The nanocluster shows strong near-infrared optical absorption in the solid state and excellent photothermal conversion ability (the equilibrium temperature ∼78.2 °C) with the light absorption centers in 286-917 nm over previous reported pentanucleus CuI4CuII clusters and CuII compounds.

Synthesis of Two Neutral Silver Alkynyl Nanoclusters by a Single Divalent Tetrahedral Anion Template and a Study of Their Optical Features.

The synthesis of nanoclusters from simple structural units is usually a challenging process because of the complexity and unpredictability of the self-assembly process of these types of compounds. Herein, two new neutral 19-nuclearity silver nanoclusters based on alkynyl ligands with the formulas [(CrO4)@Ag19(C≡CtBu)8(Ph2PO2)6(tfa)3(CH3OH)2] (1) and [(SO4)@Ag19(C≡CtBu)8(Ph2PO2)6(tfa)3(CH3OH)2] (2), in which tfa = trifluoroacetate, were synthesized, and their structures were investigated by single-crystal and powder X-ray diffraction, electrospray ionization mass spectrometry, elemental analyses, and Fourier transform infrared spectroscopy. The surface ligands of Ph2PO2H and trifluoroacetate were assembled through hydrogen bonding, metal-aromatic interactions, and coordination bonding around 19 silver atoms as the metal skeletons of the nanoclusters. Sulfate and chromate anions, as a template within the metal skeleton of clusters through bonding with silver atoms, stabilized the structure. In addition, the UV-vis absorption spectroscopy, luminescence properties, and thermal stability of the nanoclusters were investigated.

New 3D Porous Silver Nanopolycluster as a Highly Effective Supercapacitor Electrode: Synthesis and Study of the Optical and Electrochemical Properties.

A high-nucleus silver nanopolycluster as a new type of silver-based polymer supercapacitor (SSc) by a simple and single-step synthesis process was designed and synthesized. The structural, optical, and electrochemical properties of SSc-2 were determined. This highly stable conductive 3D nanopolycluster shows great cycling stability, large capacity, and high energy density without any modification or doping process and so acts as an excellent SSc (412 F g-1 at 1.5 A g-1). In addition, there was a stable cycling performance (94% capacitance) following 7000 cycles at 3 A g-1 current density. The presence of fluorinated groups, 3D expansion of high-nucleus metallic clusters, and porosity are the advantages of SSc-2 that lead to stability, conductivity, and high capacity, respectively. These results lead to the development of a novel kind of SSc by overcoming the low conductivity and limited capacity challenges without any modification.

Hexavalent Octahedral Template: A Neutral High-Nucleus Silver Alkynyl Nanocluster Emitting Infrared Light.

The first silver nanocluster with an octahedral template of TeO66- was synthesized as a neutral 36-nucleus nanocluster, and its structure was demonstrated using single-crystal X-ray diffraction, Fourier transform infrared spectroscopy, electrospray ionization mass spectrometry, and X-ray photoelectron spectroscopy. The peripheral ligands of the cagelike skeleton of the nanocluster are CF3COO- and tBuC≡C-. During the synthesis, the TeO66- template arranged the nanocluster, and a 36-nucleus nanocluster was formed. The effect of the template nature was displayed on the structural features of the nanocluster in comparison with an 8-nucleus cluster, with the same synthesis conditions. The photoluminescence and UV-vis absorption analyses of the nanocluster were also investigated. The nanocluster displayed near-infrared luminescence emission at 690 nm.

Investigation of the Effect of a Mixed-Ligand on the Accommodation of a Templating Molecule into the Structure of High-Nucleus Silver Clusters.

Advancement of the synthesis and control of the self-assembly process of new high-nucleus silver clusters with desired structures is important for both the material sciences and the many applications. Herein, three new silver clusters, 20-, 22-, and 8-nucleus, based on alkynyl ligands were constructed and their structures were confirmed by single-crystal X-ray diffraction, powder X-ray diffraction, elemental analyses, and Fourier-transform infrared spectroscopy (FT-IR). For the first time, the trivalent tetrahedron anion of AsO43-, as a template, and the surface ligand of Ph2PO2H, with new coordination modes, were employed in preparation of the silver clusters. The role of surface ligands and template anions in the size and structure of the clusters was investigated. The presence of the template in the structure of the clusters led to the formation of the high-nucleus clusters. Also, in this report, it was shown that the participation of the template in the assembly of a cluster can be controlled by the surface ligands. UV-vis absorption and luminescent properties of the clusters and the thermal stability of the 8-nucleus cluster were also studied.

Switching in Metal-Organic Frameworks.

In recent years, metal-organic frameworks (MOFs) have become an area of intense research interest because of their adjustable pores and nearly limitless structural diversity deriving from the design of different organic linkers and metal structural building units (SBUs). Among the recent great challenges for scientists include switchable MOFs and their corresponding applications. Switchable MOFs are a type of smart material that undergo distinct, reversible, chemical changes in their structure upon exposure to external stimuli, yielding interesting technological applicability. Although the process of switching shares similarities with flexibility, very limited studies have been devoted specifically to switching, while a fairly large amount of research and a number of Reviews have covered flexibility in MOFs. This Review focuses on the properties and general design of switchable MOFs. The switching activity has been delineated based on the cause of the switching: light, spin crossover (SCO), redox, temperature, and wettability.

Trivalent Tetrahedral Anion Template: A 26-Nucleus Silver Alkynyl Cluster Encapsulating Vanadate.

In order to study the charge effect on the formation of an anion-templated silver cluster, a trivalent tetrahedral anion was incorporated into the silver assembly. A 26-nuclear silver cluster was prepared, and its structure was confirmed by single-crystal X-ray diffraction. Also, the resulting structure was characterized by powder X-ray diffraction data. Its light absorption and photoluminescent properties were studied by solid-state UV diffuse-reflectance and fluorescence spectroscopy. Compared with the other reported silver clusters with tetrahedral anion templates, the more negative VO43- anion led to the formation of a bigger silver cluster. Also, the supramolecular motif O-H(CH3OH)···O(trifluoroacetate) was confirmed on the cluster surface for the first time.

Monocarboxylate-protected two-electron superatomic silver nanoclusters with high photothermal conversion performance.

The first series of monocarboxylate-protected superatomic silver nanoclusters was synthesized and fully characterized by X-ray diffraction, fourier-transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS), and electrospray ionization mass spectrometry (ESI-MS). Specifically, compounds [Ag16(L)8(9-AnCO2)12]2+ (L = Ph3P (I), (4-ClPh)3P (II), (2-furyl)3P (III), and Ph3As (IV)) were prepared by a solvent-thermal method under alkaline conditions. These clusters exhibit a similar unprecedented structure containing a [Ag8@Ag8]6+ metal kernel, of which the 2-electron superatomic [Ag8]6+ inner core shows a flattened and puckered hexagonal bipyramid of S6 symmetry. Density functional theory calculations provide a rationalization of the structure and stability of these 2-electron superatoms. Results indicate that the 2 superatomic electrons occupy a superatomic molecular orbital 1S that has a substantial localization on the top and bottom vertices of the bipyramid. The π systems of the anthracenyl groups, as well as the 1S HOMO, are significantly involved in the optical and photothermal behavior of the clusters. The four characterized nanoclusters show high photothermal conversion performance in sunlight. These results show that the unprecedented use of mono-carboxylates in the stabilization of Ag nanoclusters is possible, opening the door for the introduction of various functional groups on their cluster surface.

Stable supercapacitor electrode based on two-dimensional high nucleus silver nano-clusters as a green energy source.

Atomically precise silver nanoclusters (Ag-NCs) are known as a hot research area owing to their brilliant features and they have attracted an immense amount of research attention over the last year. There is a lack of sufficient understanding about the Ag-NC synthesis mechanisms that result in optimal silver nanoclusters with an appropriate size, shape, and morphology. In addition, the coexisting flexible coordination of silver ions, the argentophilic interactions, and coordination bonds result in a high level of sophistication in the self-assembly process. Furthermore, the expansion of clusters by the organic ligand to form a high dimensional structure could be very interesting and useful for novel applications in particular. In this study, a novel two-dimensional 14-nucleus silver poly-cluster was designed and synthesized by the combination of two synthetic methods. The high nucleus silver cluster units are connected together via tetradecafluoroazelaic acid (CF2) and this leads to the high stability of the polymer. This highly stable conductive poly-cluster, with bridging groups of difluoromethylene, displays a high energy density (372 F g-1 at 4.5 A g-1), excellent cycling stability, and great capacity. This nanocluster shows a high power density and long cycle life over 6000 cycles (95%) and can also tolerate a wide range of scan rates (5 mV s-1 to 1 V s-1), meaning it could act as a green energy source.

Ultrasonic-assisted synthesis of the nanostructures of a Co(II) metal organic framework as a highly sensitive fluorescence probe of phenol derivatives.

Nanostructures of a metal-organic framework with chemical formula, [Co(BDC)(L*)]n.DMF (TMU-40), BDC = 1,4-benzendicarboxylate, L* = 5,6-dipyridin-4-yl-1,2,3,4-tetrahydropyrazine, under ultrasonic irradiation at ambient temperature and atmospheric pressure were prepared and characterized by Fourier-transform infrared spectroscopy (FT-IR) and scanning electron microscopy (SEM). Sonication time, concentration of initial reagents and ultrasonic generator power effects on the size and morphology of nano-structured compounds were studied. TMU-40 (for Tarbiat Modares University) displayed a good potential as a luminescent sensor against phenol derivatives consist of phenol, 4-aminophenol, 4-methylphenol and 4-chlorophenol. Nano-sized TMU-40 showed the better sensing performance in comparison to its bulk phase. The nano TMU-40 displayed very selective and sensitive in detection of phenol derivatives. The detection limit amounts of 15 nM and 63 nM were achieved for 4-aminophenol in nano TMU-40 and bulk TMU-40, respectively. The special structure and fluorescent character of L* ligand and high surface area of nano MOF provide an effective interaction between MOF and phenolic analytes to selectively and sensitively detect of the analyte molecules.

Synthesis, Characterization and DNA Binding Investigations of a New Binuclear Ag(I) Complex and Evaluation of Its Anticancer Property.

AIM: A new Ag(I) complex (A3) was synthesized and evaluated for its anticancer activity against human cancer cell lines. MATERIALS AND METHODS: The complex A3 was characterized by 1H, 13C, and 31P nuclear magnetic resonance (NMR), infrared (IR) spectra, elemental analysis, and X-ray crystallography. The interaction of the complex with CT-DNA was studied by electronic absorption spectra, fluorescence spectroscopy, and cyclic voltammetry; cell viability (%) was assessed by absorbance measurement of the samples. RESULTS: The interaction mode of the complex A3 with DNA is electrostatic, and this complex shows good potential in anticancer properties against HCT 116 (human colorectal cancer cells) and MDA-MB-231 (MD Anderson-metastatic breast) cell lines with 0.5 micromolar concentrations. CONCLUSION: The Ag(I) complex could interact with DNA noncovalently and has anticancer properties.

Ultrasonic-assisted synthesis and DNA interaction studies of two new Ru complexes; RuO2 nanoparticles preparation.

AIM: To study of the interactions of two new ruthenium(II) complexes (C1 and C2) with calf thymus (CT)-DNA; production of RuO2 nanoparticles using the complexes precursor. MATERIALS & METHODS: Complex C1 was characterized by x-ray crystallography. The binding of the complexes with (CT)-DNA was studied using techniques that include electronic absorption spectra, fluorescence and redox behavior. The preparation of RuO2 nanoparticles was carried out by thermal decomposition. RESULTS: The interaction mode of DNA with complexes is the type of electrostatic. It was revealed that sonication of the samples, before thermal decomposition, has been affected the morphologies and sizes of the resulting nanoparticles. CONCLUSION: The complexes are capable of interaction with DNA molecules and they have a good potential to prepare nanostructures.

Ultrasonic assisted synthesis of a new one-dimensional nanostructured Mn(II) coordination polymer derived from azide and new multi-topic nitrogen donor ligand.

A new Mn(II) coordination polymer, [Mn(L1)2(N3)2]n (1), L1  = 3,4-bis(4-pyridyl)-5-(2-pyridyl)-1,2,4-triazole, was synthesized by the reaction of ligand L1 and mixtures of manganese(II) acetate and sodium azide via branched tube method. Compound 1 was structurally characterized by single-crystal X-ray diffraction. The results show that 1 is a 1D helix coordination polymer. Also nanostructures of 1 have been prepareded by sonochemical process at ambient temperature. The effects of two different concentrations of initial reagents on the size and morphology of the nanoparticles were studied and the products were characterized by X-ray powder diffraction and scanning electron microscopy (SEM). Also the comparison of the thermal stability of bulk form and nanoparticles of 1 was investigated by thermal gravimetric and differential thermal analyses.

Synthesis of a new Hg(II) coordination polymer: Ultrasonic-assisted synthesis and mechanical preparation of nanostructure.

A new mercury(II) coordination polymer, [Hg(4-bpmo)I2]n (1), (4-bpmo=N,N'-bis(pyridin-4-ylmethyl)oxalamide), was synthesized, by branched tube method, and structurally characterized by single-crystal X-ray diffraction. Compound 1 is a polymer with a distorted tetrahedral HgN2I2 coordination environment. The thermal stability of 1 was studied by thermal gravimetric (TG) and differential thermal (DTA) analyses. Also 1 was prepared by a sonochemical process at ambient temperature. Reaction time and concentration of initial reagents effects on the size and morphology were studied. Nanoparticles of 1, was synthesized easily by a mechanical method (neat grinding). The resulting structures were characterized by scanning electron microscopy (SEM), IR spectroscopy and X-ray powder diffraction (XRD).

Ultrasound-assisted synthesis of nano-structured Zinc(II)-based metal-organic frameworks as precursors for the synthesis of ZnO nano-structures.

A 3D, porous Zn(II)-based metal-organic framework {[Zn2(oba)2(4-bpmn)]·(DMF)1.5}n (TMU-21), (4-bpmn=N,N'-Bis-pyridin-4-ylmethylene-naphtalene-1,5-diamine, H2oba=4,4'-oxybis(benzoic acid)) with nano-rods morphology under ultrasonic irradiation at ambient temperature and atmospheric pressure was prepared and characterized by scanning electron microscopy. Sonication time and concentration of initial reagents effects on the size and morphology of nano-structured MOFs were studied. Also {[Zn2(oba)2(4-bpmn)] (TMU-21) and {[Zn2(oba)2(4-bpmb)] (TMU-6), 4-bpmb=N,N'-(1,4-phenylene)bis(1-(pyridin-4-yl)methanimine) were easily prepared by mechanochemical synthesis. Nanostructures of Zinc(II) oxide were obtained by calcination of these compounds and their de-solvated analogue as activated MOFs, at 550°C under air atmosphere. As a result of that, different Nanostructures of Zinc(II) oxide were obtained. The ZnO nanoparticles were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM) and FT-IR spectroscopy.

Ultrasonic effect on RuO2 nanostructures prepared by direct calcination of two new Ru(II)-organic supramolecular polymers.

Two novel Ru(II) complexes [(η6-p-cymene)RuCl(L1)]PF6 (R1) and [(η6-C6H6)RuCl(L1)]PF6 (R3) with ligand (E)-4-(methylthio)-N-((quinolin-2-yl)methylene)benzenamine (L1), were synthesized and investigated using elemental analysis, IR, 1H NMR, 13C NMR spectroscopy and X-ray crystallography. Complexes R1 and R3 have coordination environments with formulated (η6-p-cymene)Ru(N2Cl) and (η6-C6H6)Ru(N2Cl) respectively. The thermal stabilities of compounds R1 and R3 were studied by thermal gravimetric (TG) and differential scanning calorimetry (DSC). The binding of the complexes R1 and R3 to calf thymus DNA (CT DNA) was investigated by using electronic absorption spectra, fluorescence and redox behavior studies. Such experimental data showed that there are interactions between complexes and CT-DNA and the nature of this binding is electrostatic interaction type. Calcination of ultrasonic treated R1 and R3 results in the formation of nanoparticles of RuO2. The nanoparticles were characterized by IR spectroscopy and X-ray diffraction (XRD). Also size and morphology of nanoparticles were investigated by scanning electron microscopy (SEM).

Sonochemical effect on two new Ruthenium(II) complexes with ligand (E)-N-((6-bromopyridin-2-yl)methylene)-4-(methylthio)aniline precursors for synthesis of RuO2 nanoparticles.

Two novel Ru(II) complexes [(η6-p-cymene)RuCl(L2)]PF6 (R2) and [(η6-C6H6)RuCl(L2)]PF6 (R4), with ligand (E)-N-((6-bromopyridin-2-yl)methylene)-4-(methylthio)aniline (L2), were synthesized and characterized by elemental analysis, 1H NMR, 13C NMR and IR spectroscopy. Based on X-ray crystallography studies, complexes R2 and R4 have coordination environments with formulated (η6-p-cymene)Ru(N2Cl) and (η6-C6H6)Ru(N2Cl), respectively. The thermal stabilities of compounds R2 and R4 were studied by thermal gravimetric (TG) and differential scanning calorimetry (DSC). Thermal decomposition of these complexes was at 280°C and 260°C under air atmosphere respectively. The interaction of these complexes with calf thymus DNA (CT-DNA) was explored through electronic absorption spectra, fluorescence and redox behavior studies. The results showed that the complexes bind to CT-DNA with electrostatic interactions. Nanoparticles of RuO2 were prepared by calcination of R2 and R4. Also the role of the ultrasound waves on the characteristics of the RuO2 nanoparticles was studied. The nanoparticles were characterized by IR spectroscopy and X-ray diffraction (XRD). Also size and morphology of nanoparticles were studied by scanning electron microscopy (SEM).