Enantioselective Synthesis of Homochiral Hierarchical Nd8Fe3-Oxo Cluster from Racemic Nd9Fe2-Oxo Cluster.

Enantioselective synthesis of homochiral rare earth clusters is still a great challenge. In this work, we developed an efficient "cluster to cluster" approach, that is, a pair of enantiomerical R/S-{Nd8Fe3}-oxo clusters were successfully obtained from the presynthesized racemic {Nd9Fe2}-oxo cluster. R/S-hydrobenzoin ligands trigger the transformation of the pristine clusters by an SN2-like mechanism. Compared to the pristine cluster with an achiral core, the new cluster exhibits hierarchical chirality, from ligand chirality to interface chirality, then to helix chirality, and finally to supramolecular double helix chirality. The spectral experiments monitored the transformation and confirmed distinctly structure-related optical activity. The enantiomeric pure cluster also exhibits a potential asymmetric catalytic activity.

Homohelical Self-Assembly of Trimer of α-Cyclodextrin and Octamolybdate.

The ability to conceptually mimic biomolecules to construct emergency-functional homospiral aggregates remains a long-standing challenge. Herein, we report artificial homohelical assembly by blending inorganic polyoxometalates (POMs) and organic cyclodextrin molecules. The chiral double-helical chains have been achieved by a left-hand arrangement of trimer-trimer. The trimer is formed by three {Mo8}@α-CD inclusive complexes as a Whittaker-style paddle wheel. During the process of assembly, chiral transfer and amplification from molecule to superstructure were observed. The enantioselective adsorption of the homohelical aggregate toward (R/S)-1,1'-binaphthyl-2,2'-diamine was further demonstrated. The interaction of {Mo8} and α-CD in solution was investigated. This work opens a wide scope for the design of a homohelix, enriching POM-based inorganic-organic materials.

Selective Passivation of Surface toward Bright Yellow Defective Emission of CdS Quantum Dots.

CdE (E = S, Se) quantum dots (QDs) with a broad and large Stokes shift PL emission have emerged as potential materials for white-light LEDs. However, this surface-related emission of nanocrystals is currently limited by low quantum efficiency. Herein, a convenient noninjected one-pot method at a relatively low temperature to prepare CdS QDs was readily achieved. The CdS-368 QD displays intense broad yellow emission in both solution and the solid state at room temperature. The coligation of organic and inorganic ligands passivates the electron trap states at the QD surface and suppresses nonradiative recombination, which is responsible for the high stability of colloids in organic solvents and the distinct fluorescence quantum yield.

Doping transition metals to modulate the chirality and photocatalytic activity of rare earth clusters.

In this paper, we report the successful assembly of achiral {Ln6M} ([Ln6M(µ3-OH)8(acac)12(CH3O)x(CH3OH)y], Ln = La, M = Mn, Co, Fe) and chiral {Nd9Fe2} ([Nd9Fe2(µ4-O)(µ3-OH)14(acac)16(NO3)(CH3OH)2(H2O)3]) rare earth clusters using achiral rigid ligands and a transition metal doping strategy. {Ln6M} can be viewed as the fusion of two {Ln3M} tetrahedrons by sharing vertices. {Nd9Fe2} results from the fusion of four {Ln3M} tetrahedrons by vertice and edge sharing. The substitution of Ln with transition metal leads to changes in the coordination pattern around neighboring Ln, which triggers the switch of metal center chirality. This study demonstrates the potentiality of utilizing transition metal doping and rigid ligand to control the chirality of rare earth clusters. In addition, the photocatalytic CO2 activity of these transition metal-doped rare earth clusters has been studied.

The mystery of Ph3PS revealed in magic-size Ag-S cluster nucleation.

The synthesis of atomically precise semiconductors Ag-S clusters is a subject of intense research interest, yet the formation mechanism of such nanoclusters remains obscure due to their uncontrolled fast nucleation process in solution. Herein, we have investigated the reaction mechanism responsible for {Ag32S3} nucleation using UV, ESI-MS, NMR and SCXRD analyses. Triphenylphosphorus sulfide (PPh3S) was surprisingly found to slow down the kinetic process of the cluster nucleation. Furthermore, a key precursor [Ag2(Ph3PS)4]2+ was captured, which was attacked by Agn(CCBut)m and traces of water to generate {Ag32S3}. This mechanism provides valuable new insights into the synthesis of inorganic magic-size clusters.

Supramolecular hybrids of chiral Waugh polyoxometalate with cyclodextrins.

The development of novel systems for chiral polyoxometalates (POMs) is an attractive research field because of their fascinating topological structures and well-defined functions. Herein, we have developed a new reaction route for the synthesis of two unprecedented chiral Waugh POM-based supramolecular architectures. Single-crystal X-ray diffraction reveals that the architectures exhibit a wavy three-dimensional framework and bamboo-rod-connected framework upon regulating the size of the cyclodextrin and the stacking pattern of the D3 symmetric Waugh {MnMo9}. Solution studies using NMR, circular dichroism and isothermal titration calorimetry corroborate nicely the very weak interactions between the components. The intricate chiral microenvironment originating from the hybrid frameworks may be responsible for the selective recognition of the Λ-{MnMo9} enantiomer. This study highlights the importance of the asymmetric configuration of the POM for designing CD/POM assemblies and understanding their chirality.

A chloride-doped silver-sulfide cluster [Ag148S26Cl30(CCBut)60]6+: hierarchical assembly, enhanced luminescence and cytotoxicity to cancer cells.

The formation of high-nuclear silver(I) clusters remains elusive and their potential applications are still underdeveloped. Herein, we report an unprecedented gigantic Ag148 ([Ag148S26Cl30(CCBut)60](SbF6)6) cluster co-templated by Cl- and S2-, which was well-defined by single-crystal X-ray diffraction and high-resolution mass spectrometry. The cluster exhibits a hierarchical structure consisting of fused Ag24X16 kernel, Ag60X20 shell and "cluster of clusters assembling" of four pentagonal concave polyhedral {Ag16X5} units. Furthermore, the silver cluster emits red light at room temperature with a prominent 39.6% QY. The cellular uptake and cytotoxicity indicate that Ag148 induces apoptosis of cancer cells in a dose-dependent manner.

Unusual structural transformation and luminescence response of magic-size silver(I) chalcogenide clusters via ligand-exchange.

Structural transformations of nanoclusters provide a platform to tune their properties and understand the fundamental science due to their intimate structure-property correlation. Here, we present an alkynyl ligand-exchange induced growth of atomically precise silver(I) clusters, which are particularly of interest because of their luminescence response at room temperature. SCXRD and UV-vis map out the growth steps of the cluster from [Ag32S3(CCBut)23]3+ featuring a pseudo-D3h concave Ag32S3 to [Ag45S6(CCPhBr)32]+ with a pseudo-Oh core-shell Ag9S6@Ag24@Ag12, which is driven by a thermodynamic route under the disruption of ligands. To our knowledge, the findings in this work establish the first example of ligand-exchange as a versatile tool for tuning the size and luminescence of semiconductor silver(I) clusters.

Cluster From Cluster: A Quantitative Approach to Magic Gold Nanoclusters [Au25 (SR)18 ].

High-yield and large-scale synthesis are highly demanded for the studies of gold nanoclusters. We developed a "cluster from cluster" approach to assemble gold nanoclusters with preformed atomically precise Au13 precursors. This facile approach has proved to be very effective in the synthesis of the well-known magic cluster [Au25 (SR)18 ]- , which could prepare the target cluster in high yield (overall yield up to ≈100 %) at large scale (gram-scale based on gold). This method can be applied in the synthesis of 10 Au25 clusters with different R groups. This work presents an important approach that may be extended to high-yield and large-scale synthesis of other metal nanoclusters.

Solvent-driven crystal-crystal transformation and morphology change in a 2D layered inorganic POM-based framework.

In this paper, a pure 2D inorganic POM-based framework underwent a single crystal to single crystal conversion when soaked in organic solvents that are miscible with water, forming a more densely packed identical framework accompanying the formation of nanowires. The change in morphology is closely related to the surface tension of water, and the lower surface tension achieved by dehydration promotes the formation of nanowires, which is revealed by SXRD, PXRD, SEM, TGA and electrochemical impedance spectroscopy (EIS).

A nonconventional host-guest cubic assembly based on γ-cyclodextrin and a Keggin-type polyoxometalate.

Supramolecular self-assembly allows components to organize themselves into regular patterns by using non-covalent interactions to find the lowest-energy configuration. However, self-assembling organic and inorganic building blocks together into an ordered framework remains a challenge due to the difficulties in rationally interfacing two dissimilar materials. Herein, we report on the host-guest ensemble of polyoxometalates (POMs) using cyclodextrins (CDs) as the trapping agent to form POM@γ-CD entities. Two unprecedented super cubic isostructures, Co/Cu-PW12O40-γ-CD, were obtained. The self-assembly has been observed both in solution (MS, 1D NMR and 2D DOSY) and in the solid state. Single-crystal X-ray diffraction reveals that in a unit cell, the inner (POM@γ-CD)12 cube is encapsulated by the outer (POM@γ-CD)24 cube. Besides, due to the rather large spherical voids, two (POM@γ-CD)24 cubes are interspersed together. Preliminary investigations of the redox properties of the [PW12O40]3- encapsulated in the γ-cyclodextrins indicate that the redox properties of the trianion are largely retained, yet an additional electrochemical stabilization is observed. The adduct reported here opens the door to a new generation of hybrid materials with tuned structures and customized functionalities.

Assembly of silver alkynyl compounds with various nuclearities.

A convenient method for the synthesis of silver alkynyl compounds containing different nuclearities has been developed. The reaction of AgC[triple bond, length as m-dash]CBu(t) and AgX (X = CF3CO2(-), C2F5CO2(-)) in the presence of auxiliary ligands L (L = bipyridine, bipy; 1,10-phenanthroline, phen; 2-(diphenylphosphino)pyridine, dppy) under different conditions afforded a family of new silver alkynyl compounds, namely, [Ag3(bipy)(C[triple bond, length as m-dash]CBu(t))(CF3CO2)2]n (), [Ag4(bipy)2(C[triple bond, length as m-dash]CBu(t))(CF3CO2)3]n (), [Ag6(phen)3(C[triple bond, length as m-dash]CBu(t))2(C2F5CO2)4(MeOH)(EtOH)] (), [Ag8L4(C[triple bond, length as m-dash]CBu(t))2(C2F5CO2)6] (L = bipy, ; L = phen, ), [Ag10(dppy)2(C[triple bond, length as m-dash]CBu(t))6X4] (X = CF3CO2(-), ; X = C2F5CO2(-), ), [Ag12(bipy)2(C[triple bond, length as m-dash]CBu(t))8(C2F5CO2)4] () and [Ag12(phen)4(C[triple bond, length as m-dash]CBu(t))6(CF3CO2)6]·2EtOH (). Single-crystal X-ray analysis revealed that compounds and display infinite-chain structures, while the other seven compounds are discrete molecules containing silver nuclearities varying from 6 to 12. The formation of various structural motifs depends on the reactant ratios and the ligands/anions with different nature.

Cluster linker approach: preparation of a luminescent porous framework with NbO topology by linking silver ions with gold(I) clusters.

A cluster-based luminescent porous metal-organic framework has been constructed through a "cluster linker" approach. The luminescent gold(I) cluster, prefunctionalized with pyrazinyl groups, was used as a cluster linker, similar to an organic linker, to connect silver ions in order to form a 3D framework. 1D channels with 1.1 nm diameter were observed in the framework. The cluster with its intrinsic luminescence was incorporated into a porous framework to give a luminescent bifunctional NbO net. This MOF shows solvatochromic behavior, and the interactions between solvent molecules and silver ions inside the channels account for the changes in absorption and emission spectra.

[Ag(70)(PW(9)O(34))(2)((t)BuC[triple bond, length as m-dash]C)(44)(H(2)O)(2)](8+): ionothermal synthesis of a silver cluster encapsulating lacunary polyoxometalate ions.

A silver alkynyl cluster containing a Ag70 shell and two lacunary [PW9O34](9-) templating ions was synthesized by an ionothermal approach. Fast core-shell electronic communication between silver(i) centers and polyoxometalates was verified via cyclic voltammetry studies in [BMIm]BF4.

Poly[[bis-(2,2-bipyridine)-bis-[µ(6)-5-(carboxyl-atometh-oxy)benzene-1,3-dicarboxyl-ato]trimanganese(II)] monohydrate].

The title compound, {[Mn(3)(C(10)H(5)O(7))(2)(C(10)H(8)N(2))(2)]·H(2)O}(n), was synthesized under hydro-thermal conditions. Six carboxyl-ate groups of six 5-(carboxyl-atometh-oxy)benzene-1,3-dicarboxyl-ate anions (OABDC(3-)) join three Mn(II) ions into a trinuclear centrosymmetric [Mn(3)(µ(2)-COO)(6)] unit with one Mn site situated on a centre of inversion. The latter Mn(II) ion exhibits a distorted MnO(6) coordination, whereas the other Mn(II) ion has a trigonal-bipyramidal MnN(2)O(3) coordination environment resulting from three carboxylate O atoms and the two N atoms of the bipyridine ligand. Adjacent units are linked to each other by OABDC(3-) ligands into a layer parallel to (010). Within the layer, O-H⋯O hydrogen-bonding inter-actions involving the uncoordinated and half-occupied water mol-ecule and the free carboxyl-ate O atoms are observed. The layers stack along [010], constructing a three-dimensional structure through π-π inter-actions between adjacent pyridine rings, with a centroid-centroid distance of 3.473 (5) Å.