Vanadium-Silsesquioxane Nanocages as Heterogeneous Catalysts for Synthesis of Quinazolinones.

The functionalization of polyoxovanadate clusters is promising but of great challenge due to the versatile coordination geometry and oxidation state of vanadium. Here, two unprecedented silsesquioxane ligand-protected "fully reduced" polyoxovanadate clusters were fabricated via a facial solvothermal methodology. The initial mixture of the two polyoxovanadate clusters with different colors and morphologies (green plate V14 and blue block V6) was successfully separated as pure phases by meticulously controlling the assembly conditions. Therein, the V14 cluster is the highest-nuclearity V-silsesquioxane cluster to date. Moreover, the transformation from a dimeric silsesquioxane ligand-protected V14 cluster to a cyclic hexameric silsesquioxane ligand-protected V6 cluster was also achieved, and the possible mechanism termed "ligand-condensation-involved dissociation reassembly" was proposed to explain this intricate conversion process. In addition, the robust V6 cluster was served as a heterogeneous catalyst for the synthesis of important heterocyclic compounds, quinazolinones, starting from 2-aminobenzamide and aldehydes. The V6 cluster exhibits high activity and selectivity to access pure quinazolinones under mild conditions, where the high selectivity was attributed to the confinement effect of the macrocyclic silsesquioxane ligand constraining the molecular freedom of the reaction species. The stability and recyclability as well as the tolerance of a wide scope of aldehyde substrates endow the V6 cluster with a superior performance and appreciable potential in catalytic applications.

Dicarboxylic Acids Induced Tandem Transformation of Silver Nanocluster.

Structural transformation of metal nanoclusters (NCs) is of great ongoing interest regarding their synthesis, stability, and reactivity. Although sporadic examples of cluster transformations have been reported, neither the underlying transformation mechanism nor the intermediates are unambiguous. Herein, we have synthesized a flexible 54-nuclei silver cluster (Ag54) by combining soft (tBuC≡C-) and hard (nPrCOO-) ligands. The existence of weakly coordinated nPrCOO- enhances the reactivity of Ag54, thus facilitating the dicarboxylic acid to induce structural transformation. X-ray structural analyses reveal that Ag54 transforms to Ag28 cluster-based 2D networks (Ag28a and Ag28b) induced by H2suc (succinic acid) and H2glu (glutaric acid), whereas with H2pda (2,2'-(1,2-phenylene)diacetic acid), a discrete Ag28 cluster (Ag28c) is isolated. The key intermediate Ag17 that emerges during the self-dissociation of Ag54 was isolated by using cryogenic recrystallization and characterized by X-ray crystallography. The "tandem transformation" mechanism for the structure evolution from Ag54 to Ag28a is established by time-dependent electrospray ionization mass spectrometry (ESI-MS) and UV-vis spectroscopy. In addition, the catalytic activity in the 4-nitrophenol reduction follows the sequence Ag28c > Ag28b > Ag28a > Ag54 due to more bare silver sites on the surface of the Ag28 cluster unit. Our findings not only open new avenues to the synthesis of silver NCs but also shed light on a better understanding of the structural transformation mechanism from one cluster to another or cluster-based metal-organic networks induced by dicarboxylates.

Preparation of Vinylphosphonates from Ketones Promoted by Tf2O.

An efficient triflic anhydride promoted phosphorylation of ketone was disclosed, and vinylphosphorus compounds were prepared under solvent- and metal-free conditions. Both aryl and alkyl ketones could perform smoothly to give vinyl phosphonates in high to excellent yields. In addition, the reaction was easy to carry out and easy to scale up. Mechanistic studies suggested that this transformation might involve nucleophilic vinylic substitution or a nucleophilic addition-elimination mechanism.

Visible-light-induced cyclization of cyclic N-sulfonyl ketimines to N-sulfonamide fused imidazolidines.

A visible-light-induced metal-free cascade cyclization of cyclic N-sulfonyl ketimines with N-arylglycines for the construction of N-sulfonamide-fused imidazolidines was developed. The procedure employed 3 mol% of eosin Y as the photocatalyst at room temperature under visible light irradiation, providing various N-sulfonamide-fused imidazolidines in good yields (32 examples, up to 86% yields).

Structural rearrangement of Ag60 nanocluster endowing different luminescence performances.

It is well known that structure determines property, but obtaining a pair of silver nanoclusters with comparable structures to understand the structure-property relationship is a very challenging task. A new 60-nuclei silver nanocluster (SD/Ag60a) protected by a mixed-ligand shell of tBuS- and o-CH3OPhCOO- was obtained and characterized. Single crystal x-ray diffraction reveals that SD/Ag60a has an identical metal nuclearity and core-shell structural type to SD/Ag1 previously reported by our group, whereas the compositions of the core and shell have undergone a rearrangement from an Ag12 cuboctahedron core and an Ag48 rhombicuboctahedron shell in SD/Ag1 to an Ag14 rhombic dodecahedron core and an oval Ag46 shell in SD/Ag60a. The core enlargement from Ag12 to Ag14 originates from the replacement of two S2- in Ag12S15 by two Ag+, which gives a new Ag14S13 core. This result indicates that the metal frameworks of silver nanoclusters have some extent flexibility despite the same nuclearity, which can be influenced by ligands, solvents, anion templates, and others in the embryonic stage of the assembly. Interestingly, different core-shell architectures of Ag60 nanoclusters also significantly endow the different optical absorption bands, photocurrent-generating properties, and luminesecent behaviors. This work not only realizes the regulation of the core-shell structure of silver nanoclusters with the same nuclearity but also provides a comparable model for investigating the relationship of structure-photoelectric properties.

Four alkoxohexavanadate-based Pd-polyoxovanadates as robust heterogeneous catalysts for oxidation of benzyl-alkanes.

Four alkoxohexavanadate-based Pd-POVs [Pd(dpa)(acac)]2[V6O13(OMe)6] (1), [Pd(dpa)(acac)]2[V6O11(OMe)8] (2), [Pd(dpa)(acac)]2[V6O11(OMe)8]·H2O (3), and [Pd(DMAP)2(acac)]2[V6O11(OMe)8]·H2O (4) (POV = polyoxovanadate; dpa = 2,2'-dipyridine amine; DMAP = 4-dimethylaminopyridine; acac = acetylacetone anion) have been synthesized and fully characterized by single crystal X-ray diffraction and powder X-ray diffraction analyses, Fourier transform infrared spectroscopy, element analyses, and X-ray photoelectron spectroscopy. In 1-4, Pd complexes and hexavanadate anions are assembled through electrostatic interactions. Interestingly, the [V6O11(OMe)8](2-) cores in 2 and 3 are a pair of isomers that can be isolated by controlling crystallization temperature. Moreover, to the best of our knowledge, the {V6} core in 3 represents a new octamethoxyhexavanadates cluster. It is notable that compounds 1-4 exhibit excellent heterogeneous catalytic performance in the oxidation of benzyl-alkanes with t-butylhydroperoxide as oxidant. Among them, the catalytic activity of 1 (conv. and selec. up to 99%, respectively) outperforms others and can be reused without losing its activity.

Dynamic and transformable Cu12 cluster-based C-H···π-stacked porous supramolecular frameworks.

The assembly of cluster-based π-stacked porous supramolecular frameworks presents daunting challenges, including the design of suitable cluster building units, control of the sufficient C-H···π interactions, trade-off between structural dynamics and stability as well as understanding the resulting collective properties. Herein, we report a cluster-based C-H···π interaction-stacked porous supramolecular framework, namely, Cu12a-π, consisting of Cu12 nanocluster as a 6-connected node, which is further propagated to a dynamic porous supramolecular frameworks via dense intralayer C-H···π interactions, yielding permanent porosity. In addition, Cu12a-π can be transformed into cluster-based nonporous adaptive crystals (Cu12b-NACs) via ligand-exchange following a dissociation-reassembly mechanism. Moreover, Cu12a-π can efficiently remove 97.2% of iodine from saturated iodine aqueous solutions with a high uptake capacity of 2.96 g·g-1. These prospective results positioned at cluster-based porous supramolecular framework and enlighten follow-up researchers to design and synthesize such materials with better performance.

Two triplet emitting states in one emitter: Near-infrared dual-phosphorescent Au20 nanocluster.

Intrinsic dual-emission (DE) of gold nanoclusters in the near-infrared (NIR) are fascinating for fundamental importance and practical applications, but their synthesis remains a formidable challenge and sophisticated excited-state processes make elucidating DE mechanisms much more arduous. Here, we report an all-alkynyl-protected gold nanocluster, Au20, showing a prolate Au12 tri-octahedral kernel surrounded by two Au2(CZ-PrA)3 dimers, four Au(CZ-PrA)2 monomers, and two CZ-PrA- bridges. Au20 exhibits distinguished photophysical properties including NIR DE at 820 and 940 nm, microsecond radiative relaxation, and 6.26% photoluminescent quantum yield at ambient environment in nondegassed solution. Combining systematic studies on steady/transient spectroscopy and theoretical calculation, we identified two triplet charge transfer (CT) states, ligand-to-kernel and kernel-based CT states as DE origins. Furthermore, this NIR DE exhibits highly independent and sensitive response to surrounding environments, which well coincide with its mechanism. This work not only provides a substantial structure model to understand a distinctive DE mechanism but also motivates the further development of NIR DE materials.

Cation-induced synthesis of new polyoxopalladates.

Seven polyoxopalladate compounds, [Pd(15)(SeO(3))(10)(µ(3)-O)(10)](10-), with Na(+) (1) and K(+) (2) as counterions, and Na(6)[M(II){Pd(12)(SeO(3))(8)(µ(4)-O)(8)}]·nH(2)O (M = Co (3), Zn (4), Ni (5), Cu (6), Mn (7); n = 7-9), have been prepared and characterized by SXRD, FT-IR, UV-vis, EA, TGA, and ESI-MS. These compounds comprise two distinct cluster configurations, {Pd(15)} and {M(II)Pd(12)}, which reveals the possibility of obtaining desired noble metal clusters with a certain nuclearity by using different cations as potential structural directing or template agents in synthesis. All compounds showed apparent absorptions in the visible light region, while 3 and 7 were found to show paramagnetic behavior typical of mononuclear Co(II) and Mn(II) complexes with zero-field splitting.

RhIII-Catalyzed C-H N-Heteroarylation and Esterification Cascade of Carboxylic Acid with Organoboron Reagents and 1,2-Dichloroethane in One-Pot Synthesis.

A RhIII-catalyzed C(sp2)-H N-heteroarylation and esterification cascade of aryl carboxylic acids with N-heteroaromatic boronates and 1,2-dichloroethane in a one-pot synthesis has been disclosed. The strong coordinating ability of ortho- and meta-substituted pyridine boronates and pyrazoles as well as unsubstituted pyrimidine allows them to serve as the coupling partners. This protocol allows late-stage modification of the key precursor of roflumilast and compounds of pharmaceutical interest, which highlights the potential application of this synthetic method.

One-Pot Construction of Heteroarylation/Esterification Products of Acrylic Acids via Iridium(III)-Catalyzed C-H Activation.

A carboxylate-assisted iridium(III)-catalyzed regioselective C(sp2)-H heteroarylation/esterification reaction of acrylic acid is disclosed herein for the first time. This catalytic protocol tolerates various α-substituted, ß-substituted, and α, ß-disubstituted acrylic acids as well as heteroaromatic boronates well. The resulting 3,4-dihydro-2H-pyran-6-carboxylic acid derivative 3r highlighted the AIE-active luminophore with multiple emission signal properties and a high quantum yield of 28%, exhibiting the potential application of this methodology for the synthesis of nitrogen-containing organic functional materials.

1-Acryloyl-2-cyanoindole: A Skeleton for Visible-Light-Induced Cascade Annulation.

1-Acryloyl-2-cyanoindoles were found to be novel and efficient skeletons in visible-light-induced persulfate-promoted cascade cyclization reactions. With this transition-metal-free photocatalytic procedure, various sulfonated/thiocyanated pyrrolo[1,2-a]indolediones were synthesized from 1-acryloyl-2-cyanoindoles with sulfonyl hydrazides/NH4SCN at room temperature under mild reaction conditions.

A novel thiophene-fused polycyclic aromatic with a tetracene core: synthesis, characterization, optical and electrochemical properties.

FeCl3-mediated oxidative cyclization was successfully used to construct an extended thiophene-pendant pyrene skeleton and synthesize a novel thiophene-fused polycyclic aromatic (THTP-C) with a tetracene core. The identity of the compound was confirmed by ¹H-NMR, ¹³C-NMR, MS, and elemental analysis. Meanwhile, a single crystal of THTP-C was obtained and analyzed by X-ray single-crystal diffraction. THTP-C has a "saddle" shaped π-conjugated 1-D supramolecular structure, and favors highly ordered self-assembly by π-π interactions as evidenced by its concentration-dependent ¹H-NMR spectra in solution. The optical properties of THTP-C were investigated by ultraviolet-visible (UV-Vis) and photoluminescence (PL) spectroscopy and its electrochemical properties were investigated by cyclic voltammetry (CV). The relatively large band gap (2.86 eV), low E(HOMO) level (-5.64 eV) and intermolecular π-π interactions imply that THTP-C has a high stability against photo-degradation and oxidation, and may be a promising candidate for stable hole-transporting materials.

Markovnikov-addition of H-phosphonates to terminal alkynes under metal- and solvent-free conditions.

An addition of H-phosphonates to aryl alkynes was realized under solvent- and metal-free conditions, affording Markovnikov-selective α-vinylphosphonates in moderate to good yields. A wide range of aryl alkynes could be applied for the reaction. A tentative mechanism of addition-substitution was proposed based on in situ 31P {1H} NMR studies.

Silver-catalyzed decarboxylative radical cascade cyclization toward benzimidazo[2,1-a]isoquinolin-6(5H)-ones.

A simple and efficient decarboxylative radical addition/cyclization strategy was developed, by which a wide range of benzimidazo[2,1-a]isoquinoline-6(5H)-ones were prepared in one-pot via reaction of functionalized 2-arylbenzoimidazoles and carboxylic acids in the presence of K2S2O8/AgNO3 under mild reaction conditions.

Metal-free sulfonyl radical-initiated cascade cyclization to access sulfonated indolo[1,2-a]quinolines.

A metal-free cascade reaction was developed for the synthesis of indolo[1,2-a]quinoline derivatives from arylsulfonyl hydrazides and 1-(2-(arylethynyl)phenyl)indoles in the presence of TBAI/TBHP. Impressively, these products exhibit excellent fluorescence properties, which is promising for cell imaging.

2,4-Bis(4-chloro-benzo-yl)-1-(4-chloro-phen-yl)-3,5-di-2-thienylcyclo-hexa-nol methanol hemisolvate.

The title compound, C(34)H(25)Cl(3)O(3)S(2)·0.5CH(3)OH, was synthesized by the reaction of thio-phene-2-carbaldehyde with acetophenone and NaOH under solvent-free conditions, using tetra-butylammonium bromide as a phase-transfer catalyst. The central six-membered ring adopts a chair conformation with the bulky thio-phene, 4-chloro-phenyl and 4-chloro-benzoyl substituents in equatorial positions. The hydroxyl group is in an axial position and forms an intra-molecular O-H⋯O hydrogen bond to the carbonyl group of an adjacent 4-chloro-benzoyl substituent. The methanol solvent mol-ecules are disordered equally over two positions within one-dimensional channels, with site occupancy factors of 0.25.

Tetrakis[(benzene-18-crown-6)potassium]bis[tris(thiocyanato)copper(I)].

The title complex, bis-(µ-benzene-18-crown-6)-3κ(6)O:4κO;4κ(6)O:3κO-bis-(benzene-18-crown-6)-1κ(6)O,6κ(6)O-tetra-µ-thiocyanato-1:2κ(2)S:N;2:3κ(2)N:S;4:5κ(2)S:N;5:6κ(2)N:S-dithio-cyanato-2κN,5κN-2,5-dicopper(I)-1,3,4,6-tetra-potassium(I), [K(4)Cu(2)(NCS)(6)(C(16)H(24)O(6))(4)] or {[K(C(16)H(24)O(6))](4)[Cu(NCS)(3)](2)}, consists of four [K(benzene-18-crown-6)](+) cations and two [Cu(NCS)(3)](2-) anions, forming a dimeric structure with site symmetry . In each [Cu(NCS)(3)](2-) anion, the Cu(I) atom is coordinated by three N atoms of thio-cyanate ligands in a trigonal-planar coordination geometry. Each [Cu(NCS)(3)](2-) anion bridges two [K(benzene-18-crown-6)](+) cations, with K-S distances of 3.317 (3) and 3.198 (3) Å, and two [K(benzene-18-crown-6)](+) cations are linked across a crystallographic centre of inversion, with K-O distances of 2.903 (5) Å.

3-Phenyl-1,5-di-2-thienylpentane-1,5-dione.

The asymmetric unit of the title compound, C(19)H(16)O(2)S(2), contains two independent mol-ecules with slightly different conformations. In the crystal structure, weak inter-molecular C-H⋯O hydrogen bonds [C⋯O = 3.279 (15) and 3.407 (16) Å] link the mol-ecules into chains extended along the c axis.

1,1'-[o-Phenyl-enebis(nitrilo-methyl-idyne)]di-2-naphthol ethanol hemisolvate.

The asymmetric unit of the title compound, C(28)H(20)N(2)O(2)·0.5C(2)H(5)OH, contains two independent mol-ecules of 1,1'-[o-phenyl-enebis(nitrilo-methyl-idyne)]di-2-naphthol, denoted A and B, and one ethanol solvent mol-ecule. The hydr-oxy groups are involved in intra-molecular O-H⋯N hydrogen bonds influencing the mol-ecular conformations, which are slightly different in mol-ecules A and B, where the two bicyclic systems form dihedral angles of 51.93 (9) and 58.52 (9)°, respectively. In the crystal structure, a number of short inter-molecular C⋯C contacts with distances of less than 3.5 Šsuggest the existence of π-π inter-actions, which contribute to the stability of the crystal packing.