Multiple Template Site Nitrogen Atom Deletions from Rotaxanes, Catenanes, and a Molecular Knot.

We report the deletion of nitrogen atoms from multiple template sites in rotaxanes, catenanes, and a molecular knot. Nitrogen extrusion from secondary amines in the backbone of the interlocked structures is achieved using -diphenylphosphinylhydroxylamine (DPPH), forming carbon-carbon bonds while largely maintaining the integrity of the original mechanical bonding. We find that DPPH gives improved yields (up to 51%) for nitrogen atom deletions from template sites in rotaxanes compared to an anomeric amide nitrogen-deletion reagent and overcomes a major substrate limitation in that, using DPPH, only one of the substituents of the secondary amine in the rotaxane axle needs to be radical-stabilizing.

Crown Ether-Peptide Rotaxanes.

We report on the metal-free active template synthesis of crown ether-peptide rotaxanes. A 24-crown-8 ring is sufficiently small that the side chains of canonical branched amino acids act as barriers that trap the macrocycle on the particular glycine residue used to assemble the rotaxane. The resulting crown ether-tripeptide rotaxane can subsequently be extended from either or both N- and C-termini of the axle.

Fast and slow walking driven by chemical fuel.

We demonstrate the fast forward and slow backward motion of a biped on a tetrahedral track using chemical fuel, cooperative binding and kinetic selectivity. Walking of the biped is based on its dibenzyl amine feet that bind to zinc porphyrin units and, upon protonation, to dibenzo 24-crown-8 sites affording pseudorotaxane linkages.

Fluorescence enhancement structural rigidification inside a self-assembled Pd molecular vessel.

Restriction of intramolecular motion (RIM) is fundamental for the high emission of aggregation-induced emission (AIE)-active molecules in aggregates or the solid-state. However, they are weakly emissive in dilute solution, which limits their application in dilute solutions. A Pd molecular vessel (MP1) was constructed by assembling [-(en)Pd(NO)] (M) with a tetradentate donor (L) in a 2 : 1 molar ratio.

Heteroleptic metallosupramolecular aggregatescomplexation for supramolecular catalysis.

Supramolecular catalysis is reviewed with an eye on heteroleptic aggregates/complexation. Since most of the current metallosupramolecular catalytic systems are homoleptic in nature, the idea of breaking/reducing symmetry has ignited a vivid search for heteroleptic aggregates that are made up by different components. Their higher degree of functional diversity and structural heterogeneity allows, as demonstrated by Nature by the multicomponent ATP synthase motor, a more detailed and refined configuration of purposeful machinery.

Conformation-Selective Self-Assembly of Pd Trifacial Molecular Barrels Using a Tetrapyridyl Ligand.

A conformationally flexible tetrapyridyl ligand was assembled separately with three cis-blocked 90° Pd acceptors (, , and ) containing different blocking diamines. Surprisingly, different conformations of the donor were arrested by the acceptors depending on the nature of the blocking amine, leading to the formation of isomeric Pd barrels (, , and ). and with larger windows have been used to encapsulate polyaromatic hydrocarbons.

Toward Molecular Cybernetics - the Art of Communicating Chemical Systems.

The emerging field of molecular cybernetics has the potential to widely broaden our perception of chemistry. Chemistry will develop beyond its current focus that is mainly concerned with single transformations, pure compounds, and/or defined mixtures. On this way, chemistry will become autonomous, networked and smart through communicating molecules each of which serves a control engineering purpose, like the set of wheels in the machinery of life.

Guest-Induced Enantioselective Self-Assembly of a Pd Homochiral Octahedral Cage with a -Symmetric Pyridyl Donor.

Self-assembly of an achiral acceptor of square-planar Pd(II) or Pt(II) ion with a symmetric donor generally yields achiral architecture or a racemic mixture of chiral assemblies. Selective formation of an enantiopure assembly in such processes is very challenging. We report here a new approach of converting a dynamic mixture of multiple homochiral assemblies to an enantiopure architecture through the interaction of a chiral guest molecule.

Self-Assembled Pd Coordination Cage as Photoregulated Oxidase-Like Nanozyme.

Designing supramolecular architectures with uncommon geometries embedded with functional building units is of immense importance in contemporary research. In this report, we present a new water-soluble PdL supramolecular coordination nanocage () that was synthesized via self-assembly of a tetradentate donor () with ditopic acceptor -[(en)Pd(NO)] [en = ethylenediamine]. Self-assembly of a tetratopic donor with a cis-blocked 90° acceptor commonly produces tri/tetra- or hexagonal barrel-type structures.

Self-Assembly of a Pd Macrocycle and Pd Homochiral Tetrahedral Cages Using Poly(tetrazolate) Linkers.

A two-dimensional molecular square () was obtained by the self-assembly of a bis(tetrazole) linker, 4,4'-bis(1-tetrazol-5-yl)-1,1'-biphenyl (H), with a square-planar metal acceptor [ = (tmeda)Pd(NO), where tmeda = ,,','-tetramethylethane-1,2-diamine] in dimethyl sulfoxide (DMSO) followed by crystallization. The uncommon 2,3-binding mode through N atoms of the tetrazole rings in this assembly leads to the formation of an octanuclear molecular square. The molecular square [Pd()(NO)] is unstable in DMSO and slowly converts to a dynamic mixture of a 3D tetrahedral cage [Pd()(NO)] and the macrocycle .

Self-Assembly of Enantiopure Pd Tetrahedral Homochiral Nanocages with Tetrazole Linkers and Chiral Recognition.

Enantiopure acceptors (,) and () [where = (1,1,2,2-tetramethylcyclohexane-1,2-diamine)Pd(NO)] have been used to design enantiopure Pd(II) tetrahedral cages. Self-assembly of [1,4-di(1-tetrazol-5-yl)benzene] (H) with chiral acceptors (,) and (,) yielded enantiopure homochiral tetrahedral cages (ΛΛΛΛ) and (ΔΔΔΔ), respectively. This strategy was further extended by using [2,6-di(1-tetrazol-5-yl)naphthalene] (H) with (,) and (,) to obtain water-soluble enantiopure tetrahedral nanocages (ΛΛΛΛ) and (ΔΔΔΔ), respectively.

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 'cationic-cage' (CC-Ag).

Pyriplatin-Boron-Dipyrromethene Conjugates for Imaging and Mitochondria-Targeted Photodynamic Therapy.

Monofunctional pyriplatin analogues cis-[Pt(NH)(L)Cl](NO) (1-3) having boron-dipyrromethene (BODIPY) pendants (L) with 1,3,5,7-tetramethyl-8-(4-pyridyl)-4,4'-difluoroboradiazaindacene moieties were designed and synthesized, and their photocytotoxic properties were studied. The Pt-BODIPY conjugates displayed an absorption band within 505-550 nm and a green emissive band near 535 nm in 1% DMSO/DMEM (Dulbecco's modified Eagle's medium) buffer. Complex cis-[Pt(NH)(4-Me-py)Cl](NO) (4) was used as a control for determining the structural aspects by X-ray crystallography.

Correction: Face and edge directed self-assembly of Pd tetrahedral nano-cages and their self-sorting.

[This corrects the article DOI: 10.1039/C6SC02012G.].

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° ditopic acceptor [ cis-(tmeda)Pd(NO)] (M) with a tetradentate donor L [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' N'-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.

Preparation of a chiral Pt tetrahedral cage and its use in catalytic Michael addition reaction.

The reaction of chiral cis-[(1S,2S)-dch]Pt(NO3)2 (M) [where (1S,2S)-dch = (1S,2S)-1,2-diaminocyclohexane] with a hexadentate ligand (L) in 3 : 1 stoichiometric ratio yielded a [12+4] self-assembled chiral M12L4 molecular tetrahedron (T). The cage T features an internal 3D nanocavity with large open 'windows', enabling it to catalyze Michael addition reactions of a series of nitrostyrene derivatives with indole in a 9 : 1 water : methanol mixture.

A Self-Assembled Trigonal Prismatic Molecular Vessel for Catalytic Dehydration Reactions in Water.

A water-soluble Pd trigonal prism (A) was synthesized by two-component coordination-driven self-assembly of a Pd 90° acceptor with a tetraimidazole donor. The walls of the prism are constructed by three conjugated aromatic building blocks, which means that the confined pocket of the prism is hydrophobic. In addition to the hydrophobic cavity, large product egress windows make A an ideal molecular vessel to catalyze otherwise challenging pseudo-multicomponent dehydration reactions in its confined nanospace in aqueous medium.

Face and edge directed self-assembly of Pd tetrahedral nano-cages and their self-sorting.

Reactions of a -blocked Pd(ii) 90° acceptor [-(tmeda)Pd(NO)] () with 1,4-di(1-tetrazol-5-yl)benzene ( ) and [1,3,5-tri(1-tetrazol-5-yl)benzene] ( ) in 1 : 1 and 3 : 2 molar ratios respectively, yielded soft metallogels and [tmeda = ,,','-tetramethylethane-1,2-diamine]. Post-metalation of the gels and with yielded highly water-soluble edge and face directed self-assembled Pd tetrahedral nano-cages and , respectively. Such facile conversion of Pd(ii) gels to discrete tetrahedral metallocages is unprecedented.

Aggregation-Induced Emission of Platinum(II) Metallacycles and Their Ability to Detect Nitroaromatics.

Two new acceptors containing platinum-carbazole (1) and platinum-triphenylamine (2) backbones with bite angles of 90° and 120°, respectively, have been synthesised and characterised. Reactions of the rigid acceptor 1 with linear dipyridyl-based donors (3 and 4) generated [4+4] self-assembled molecular squares (5 and 6), and similar treatments with acceptor 2 instead of 1 yielded [6+6] self-assembled molecular hexagons (7 and 8). The metallacycles were characterised by multinuclear NMR spectroscopy ((1) H and (31) P) and ESI-MS.

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

Two shape-persistent covalent cages (CC1(r) and CC2(r)) 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 CC1(r) and CC2(r) 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).

Urea-Functionalized Self-Assembled Molecular Prism for Heterogeneous Catalysis in Water.

Reaction of a ditopic urea "strut" (L1) with cis-(tmen)Pd(NO3)2 yielded a [3+3] self-assembled molecular triangle (T) [L1 = 1,4-di(4-pyridylureido)benzene; tmen = N,N,N',N'-tetramethylethane-1,2-diamine]. Replacing cis-(tmen)Pd(NO3)2 in the above reaction with an equimolar mixture of Pd(NO3)2 and a clip-type donor (L2) yielded a template-free multicomponent 3D trigonal prism (P) decorated with multiple urea moieties [L2 = 3,3'-(1H-1,2,4-triazole-3,5-diyl)dipyridine]. This prism (P) was characterized by NMR spectroscopy, and the structure was confirmed by X-ray crystallography.

Mechano-fluorochromic Pt(II) Luminogen and Its Cysteine Recognition.

A new triphenylamine-based organometallic Pt(II) luminogen (1) and its analogous organic compound (2) are reported. The molecules are decorated with aldehyde functionality to improve their photophysical properties by utilising donor-acceptor interactions. The single crystal X-ray structure analysis of Pt(II) analogue 1 revealed that the neighbouring molecules were loosely organised by weak intermolecular C-H⋅⋅⋅π interactions.

Conformation-selective coordination-driven self-assembly of a ditopic donor with Pd(II) acceptors.

Coordination-driven self-assembly of 3-(5-(pyridin-3-yl)-1H-1,2,4-triazol-3-yl)pyridine (L) was investigated with 90°cis-blocked Pd(II) acceptors and tetratopic Pd(NO3)2. Although the ligand is capable of binding in several different conformations (acting as a ditopic donor through the pyridyl nitrogens), the experimental results (including X-ray structures) showed that it adopts a particular conformation when it binds with 90°cis-blocked Pd(II) acceptors (two available sites) to yield [2 + 2] self-assembled macrocycles. On the other hand, with Pd(NO3)2 (where four available sites are present) a different conformer of the same donor was selectively bound to form a molecular cubic cage.