Cage Encapsulated Gold Nanoparticles as Heterogeneous Photocatalyst for Facile and Selective Reduction of Nitroarenes to Azo Compounds

A discrete nanoscopic organic cage (OC1(R)) has been synthesized from a phenothiazine based trialdehyde treating with chiral 1,2-cyclohexanediamine building block via dynamic imine bond formation followed by reductive amination. The cage compound has been characterized by several spectroscopic methods, which advocate that OC1(R) has trigonal prismatic shape formed via 2 + 3] self-assembled imine condensation followed by imine reduction. This newly designed cage has aromatic walls and porous interior decorated with two cyclic thioether and three vicinal diamine moieties suitable for binding gold ions to engineer the controlled nucleation and stabilization of ultrafine gold nanoparticles (AuNPs). The functionalized confined pocket of the cage has been used for the controlled synthesis of AuNPs with narrow size distribution via encapsulation of Au(III) ions. Inductively coupled plasma mass spectrometric (ICP-MS) analysis revealed that the composite Au@OC1(R) has very high (similar to 68 wt %) gold loading. In distinction, reduction of gold salts in absence of the cage yielded structureless agglomerates. The fine-dispersed cage anchored AuNPs (Au@OC1(R)) have been finally used as potential heterogeneous photocatalyst for very facile and selective conversion of nitroarenes to respective azo compounds at ambient temperature in just 2 h reaction time. Exceptional chemical stability and reusability without any agglomeration of AuNPs even after several cycles of use are the potential features of this material. The composite Au@OC1(R) represents the first example of organic cage supported gold nanoparticles as photocatalyst

Self-assembly of a ``cationic-cage'' via the formation of Ag-carbene bonds followed by imine condensation

A new strategy for the synthesis of a ``cationic-cage'' (CC-Ag) has been developed via metal-carbene (M-CNHC) bond formation followed by imine bond condensation. Reaction of a trigonal trisimidazolium salt H3L(PF6)(3) functionalized with three flexible N-phenyl-aldehyde pendants with silver oxide yielded a trinuclear tricationic organometallic cage (OC-Ag). Subsequent treatment of the organometallic cage (OC-Ag) with 1,4-diaminobutane links the two tris-NHC ligands via imine bond condensation, which thus generates a 3D `cationiccage' (CC-Ag). Furthermore, post-synthetic replacement of the Ag(I) with Au(I) leading to the formation of CC-Au was achieved via trans-metalation, with the retention of the molecular architecture

Reversible Multistimuli Switching of a Spiropyran-Functionalized Organic Cage in Solid and Solution

A spiropyran-decorated covalent organic cage (<b>PC2</b>) has been designed, employing dynamic imine chemistry followed by imine bond reduction. The molecule is capable of altering its color upon exposure to external stimuli such as heat and light. Construction of a 3D organic cage introduces a new piece to the system by swapping the closed form with the open form in the solid state with diverse color change. Moreover, this material has high chemical stability and is capable of reversible stimuli-responsive color change without any degradation for an extended period

Building Block Dependent Morphology Modulation of Cage Nanoparticles and Recognition of Nitroaromatics

Morphology of nanomaterials has a strong impact on their chemical/physical properties, and controlled synthesis of such materials with desirable morphology is a major challenge. This article presents the role of a building block in the morphology of organic cage particles. In this context, three organic cages (A(3)X(2), B3X2, and C3X2) were devised from triphenylamine-based dialdehydes (A-C) and a flexible triamine (X) by utilizing dynamic imine chemistry. All of the synthesized cages were characterized by various spectroscopic techniques, which suggested the formation of 3+ 2] assembled architectures. Though the cages are isostructural, structural variation in the aldehyde building blocks imparted by the incorporation of phenyl moieties into the triphenylamine core produces morphologically diverse cage particles, as indicated by SEM. The synthesized cages were found to be fluorescent; the reduced analogue of cage A(3)X(2) (A(3)X(2)(r)) was tested to explore its use as a chemosensor for the detection of nitroaromatic explosives. The experimental findings suggest high selectivity and sensitivity of A(3)X(2)(r) towards picric acid (PA) among the various nitroaromatics tested. A theoretical investigation of fluorescence quenching suggested that formation of a ground-state charge-transfer complex with a resonance energy-transfer (RET) process could be the main reason behind such selectivity of the cage towards PA

Self-Assembled Pd(II) Barrels as Containers for Transient Merocyanine Form and Reverse Thermochromism of Spiropyran

Self-assembly of a cis-blocked Pd(II) 90\ub0 ditopic acceptor [cis-(tmeda)Pd(NO3)2] (M) with a tetradentate donor L1 [benzene-1,4-di(4-terpyridine)] in 2:1 molar ratio yielded two isometric molecular barrels MB1 and MB3 in DMSO [tmeda = N,N,N\u2032N\u2032-tetramethylethane-1,2-diamine]. Exclusive formation of the symmetrical tetrafacial barrel (MB1) was achieved when the self-assembly was performed in aqueous medium. The presence of a large confined cavity makes MB1 a potential molecular container. Spiropyran (SP) compounds exist in stable closed spiro form in visible light and convert to transient open merocyanine (MC) form upon irradiation with UV-light or upon strong heating. The transient MC form readily converts to the stable closed SP form in visible light. MB1 has been employed as a safe container to store the planar and unstable merocyanine isomers (MC1/2) of different spiropyran molecules (SP1/2) [SP1/2 = 6-bromo-spiropyran and 6- nitrospiropyran] for several days. The transient MC forms (MC1 and MC2) were found to be stable inside the molecular container MB1 under visible light and even in the presence of different stimuli such as heat and UV light for a long time. Such stabilization of MC forms inside the confined cavity of MB1 is noteworthy. This phenomenon was generalized by utilizing a carbazole-based molecular barrel (MB2) as a host, which also showed a similar stabilization of transient MC form in visible light at room temperature. Moreover, reverse thermochromism was observed as a result of heating of the MC1 82 MB2 complex, which de-encapsulates the guest in the form of SP1 to give a colorless solution. Moreover, both the host molecules (MB1, MB2) were capable of stabilizing transient MC2 even in the solid state. Such stabilization of transient MC forms in the solid state and transformation of SP forms to MC forms in the solid state in the presence of molecular barrel are remarkable, and these properties have been employed in developing a magic ink

Molecular Cage Impregnated Palladium Nanoparticles: Efficient, Additive-Free Heterogeneous Catalysts for Cyanation of Aryl Halides

Two shape-persistent covalent cages (<b>CC1</b>^<b>r</b> and <b>CC2</b>^<b>r</b>) have been devised from triphenyl amine-based trialdehydes and cyclohexane diamine building blocks utilizing the dynamic imine chemistry followed by imine bond reduction. The cage compounds have been characterized by several spectroscopic techniques which suggest that <b>CC1</b>^<b>r</b> and <b>CC2</b>^<b>r</b> are [2+3] and [8+12] self-assembled architectures, respectively. These state-of-the-art molecules have a porous interior and stable aromatic backbone with multiple palladium binding sites to engineer the controlled synthesis and stabilization of ultrafine palladium nanoparticles (PdNPs). As-synthesized cage-embedded PdNPs have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and powder X-ray diffraction (PXRD). Inductively coupled plasma optical emission spectrometry reveals that <b>Pd@CC1</b>^<b>r</b> and <b>Pd@CC2</b>^<b>r</b> have 40 and 25 wt% palladium loading, respectively. On the basis of TEM analysis, it has been estimated that as small as ∼1.8 nm PdNPs could be stabilized inside the <b>CC1</b>^<b>r</b>, while larger <b>CC2</b>^<b>r</b> could stabilize ∼3.7 nm NPs. In contrast, reduction of palladium salts in the absence of the cages form structure less agglomerates. The well-dispersed cage-embedded NPs exhibit efficient catalytic performance in the cyanation of aryl halides under heterogeneous, additive-free condition. Moreover, these materials have excellent stability and recyclability without any agglomeration of PdNPs after several cycles

Molecular Cage Impregnated Palladium Nanoparticles: Efficient, Additive-Free Heterogeneous Catalysts for Cyanation of Aryl Halides

Two shape-persistent covalent cages (<b>CC1</b>^<b>r</b> and <b>CC2</b>^<b>r</b>) have been devised from triphenyl amine-based trialdehydes and cyclohexane diamine building blocks utilizing the dynamic imine chemistry followed by imine bond reduction. The cage compounds have been characterized by several spectroscopic techniques which suggest that <b>CC1</b>^<b>r</b> and <b>CC2</b>^<b>r</b> are [2+3] and [8+12] self-assembled architectures, respectively. These state-of-the-art molecules have a porous interior and stable aromatic backbone with multiple palladium binding sites to engineer the controlled synthesis and stabilization of ultrafine palladium nanoparticles (PdNPs). As-synthesized cage-embedded PdNPs have been characterized by transmission electron microscopy (TEM), scanning electron microscopy (SEM), and powder X-ray diffraction (PXRD). Inductively coupled plasma optical emission spectrometry reveals that <b>Pd@CC1</b>^<b>r</b> and <b>Pd@CC2</b>^<b>r</b> have 40 and 25 wt% palladium loading, respectively. On the basis of TEM analysis, it has been estimated that as small as ∼1.8 nm PdNPs could be stabilized inside the <b>CC1</b>^<b>r</b>, while larger <b>CC2</b>^<b>r</b> could stabilize ∼3.7 nm NPs. In contrast, reduction of palladium salts in the absence of the cages form structure less agglomerates. The well-dispersed cage-embedded NPs exhibit efficient catalytic performance in the cyanation of aryl halides under heterogeneous, additive-free condition. Moreover, these materials have excellent stability and recyclability without any agglomeration of PdNPs after several cycles

Mixed-metal chalcogenide tetrahedral clusters with an exo-polyhedral metal fragment

The reaction of metal carbonyl compounds with group 6 and 8 metallaboranes led us to report the synthesis and structural characterization of several novel mixed-metal chalcogenide tetrahedral clusters. Thermolysis of arachno-[(Cp*RuCO)2B2H6], 1, and [Os3(CO)12] in the presence of 2-methylthiophene yielded [Cp*Ru(CO)2(μ-H){Os3(CO)9}S], 3, and [Cp*Ru(μ-H){Os3(CO)11}], 4. In a similar fashion, the reaction of [(Cp*Mo)2B5H9], 2, with [Ru3(CO)12] and 2-methylthiophene yielded [Cp*Ru(CO)2(μ-H){Ru3(CO)9}S], 5, and conjuncto-[(Cp*Mo)2B5H8(μ-H){Ru3(CO)9}S], 6. Both compounds 3 and 5 can be described as 50-cve (cluster valence electron) mixed-metal chalcogenide clusters, in which a sulfur atom replaces one of the vertices of the tetrahedral core. Compounds 3 and 5 possess a [M3S] tetrahedral core, in which the sulfur is attached to an exo-metal fragment, unique in the [M3S] metal chalcogenide tetrahedral arrangements. All the compounds have been characterized by mass spectrometry, IR, and 1H, 11B and 13C NMR spectroscopy in solution, and the solid state structures were unequivocally established by crystallographic analysis of compounds 3, 5 and 6

Instantaneous Gelation of a Self-Healable Wide-Bandgap Semiconducting Supramolecular Mg(II)-Metallohydrogel: An Efficient Nonvolatile Memory Design with Supreme Endurance

An efficient strategy for room-temperature, atmospheric-pressure synthesis of a supramolecular metallohydrogel of the Mg(II) ion, i.e., Mg@3AP, using the metal-coordinating organic ligand 3-amino-1-propanol as a low-molecular-weight gelator (LMWG) in a water medium has been developed. Through a rheological analysis, we looked into the mechanical properties of the supramolecular Mg(II)-metallohydrogel. The self-healing nature of the metallohydrogel is confirmed along with the thixotropic characteristics. Investigation using field emission scanning electron microscopy revealed the hierarchical network of the supramolecular metallohydrogel. The EDX elemental mapping confirms the primary chemical constituents of the metallohydrogel. The possible metallohydrogel formation strategy has been analyzed through FT-IR spectroscopic studies. In this work, Schottky diode structures in a metal–semiconductor–metal geometry structures based on a magnesium(II) metallohydrogel (Mg@3AP) have been constructed, and charge transport behavior has been observed. Furthermore, here, it is demonstrated that the resistive random access memory (RRAM) device based on Mg@3AP exhibits bipolar resistive switching behavior at room temperature and ambient conditions. We have also looked into the switching mechanism through the formation (rupture) of conductive filaments between the metal electrodes to understand the process of resistive switching behavior. With a high on/off ratio (∼100), this RRAM device exhibits remarkable switching endurance over 10,000 switching cycles. These structures are suitable for use in nonvolatile memory design, neuromorphic computing, flexible electronics, and optoelectronics, among other fields, due to their simple fabrication procedures, reliable resistive switching behavior, and stability of the current system