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A self-assembled coordination cage usually possesses one well-defined three-dimensional (3D) cavity whereas infinite number of 3D-cavities are crafted in a designer metal-organic framework. Construction of a discrete coordination cage possessing multiple number of 3Dcavities is a challenging task. Here we report the peripheral decoration of a trinuclear [Pd 3 L 6 ] core with one, two and three units of a [Pd 2 L 4 ] entity for the preparation of multi-3D-cavity conjoined-cages of [Pd 4 (L a) 2 (L b) 4 ], [Pd 5 (L b) 4 (L c) 2 ] and [Pd 6 (L c) 6 ] formulations, respectively. Formation of the tetranuclear and pentanuclear complexes is attributed to the favorable integrative self-sorting of the participating components. Cage-fusion reactions and ligand-displacement-induced cage-to-cage transformation reactions are carried out using appropriately chosen ligand components and cages prepared in this work. The smaller [Pd 2 L 4 ] cavity selectively binds one unit of NO 3 − , F − , Cl − or Br − while the larger [Pd 3 L 6 ] cavity accommodates up to four DMSO molecules. Designing aspects of our conjoined-cages possess enough potential to inspire construction of exotic molecular architectures.

Mimicking biological structures such as fruits and seeds using molecules and molecular assemblies is a great synthetic challenge. Here we report peanut-shaped nanostructures comprising two fullerene molecules fully surrounded by a dumbbell-like polyaromatic shell. The shell derives from a molecular double capsule composed of four W-shaped polyaromatic ligands and three metal ions. Mixing the double capsule with various fullerenes (that is, C60, C70 and Sc3N@C80) gives rise to the artificial peanuts with lengths of ∼3 nm in quantitative yields through the release of the single metal ion. The rational use of both metal–ligand coordination bonds and aromatic–aromatic π-stacking interactions as orthogonal chemical glue is essential for the facile preparation of the multicomponent, biomimetic nanoarchitectures.

Metal-driven self-assembly is one of the most effective approaches to lucidlydesign alarge range of discrete 2D and 3D coordinationa rchitectures/complexes. Palladium(II)-based self-assembled coordination architectures are usually preparedb yu sing suitable metal components, in either ap artially protected form (PdL')o rt ypical form (Pd; charges are not shown), and designed ligand components. The self-assembled moleculesp repared by using am etal component and only one type of bi-or polydentate ligand (L) can be classified in the homoleptic series of complexes. On the other hand, the less explored heteroleptic series of complexes are obtained by using am etal component and at least two different types of non-chelating bi-or polydentate ligands (such as L a andL b ). Methods that allow the controlled generation of single, discrete heteroleptic complexes are less understood.As urvey of palladium(II)-based self-as-sembled coordination cages that are heteroleptich as been made. This review article illustratesasystematic collection of such architectures and credible justification of their formation, along with reportedf unctional aspects of the complexes.T he collected heteroleptic assemblies are classified here into three sections:1 )[(PdL') m (L a ) x (L b ) y ]-type complexes, in which the denticity of L a and L b is equal; 2) [(PdL') m (L a ) x (L b ) y ]-type complexes, in which the denticity of L a and L b is different;a nd 3) [Pd m (L a ) x (L b ) y ]-type complexes,i n which the denticity of L a and L b is equal. Representative exampleso fs ome important homoleptic architectures are also provided, wherever possible, to set ab ackground for a better understanding of the related heteroleptic versions. The purpose of this review is to pave the way for the construction of severalu nique heteroleptic coordination assemblies that might exhibit emergents upramolecular functions.Review complexes is m + n and the total variety of components is only two. Applications of these homoleptic complexes in various fields, such as catalysis, [3] molecular recognition, [4a-c] sensing [4d] and encapsulationo fv aried guest molecules, [4c, 5] has been widely studied.Elegantarchitectures of biological multi-component systems, for example, metalloproteins and viral capsids,e xploit weak supramolecular interactions in ac ontrolled and harmonious mannerf or their construction by using relevant building blocks. [6] Occurrences of multicomponent systems in biology inspire chemistsw ho seek to advance structurala nd functional complexitieso fs upramolecular systems. Thus, in the field of metallo-supramolecular chemistry, noteworthy efforts have been directed towardt he rational design and controlled synthesis of discrete, heteroleptic structures. The methodsf or the synthesis of discrete, heteroleptic, self-assembled, coordination architectures from various metal components, such as Zn II ,F e II , Hg II ,C r III ,C o III ,R h III ,C u I ,C u II ,R u II and Pt II ,a re well explored by the groups of Lehn,F ujita, Zheng,S tang, Schm...

A self-assembled binuclear coordination cage of the PdL formulation has been constructed by complexation of Pd(NO) with N, N'-bis(3-pyridylmethyl)naphthalenediimide (L). The cage, i.e., [Pd(L)](NO) (1), displayed a further self-assembly phenomenon to afford a gel phase, upon dissolution in either dimethyl sulfoxide or acetonitrile-water (1:1) followed by standing at room temperature. It was observed that a synergy among the metal ion, ligand, counteranion, solvent, and concentration played a vital role for metallogel formation. The morphology of the metallogel as observed from microscopy studies revealed the formation of a rare variety of nanoscale metal-organic particles. Salient features of the gel include the thixotropic (mechanoresponsive) nature, in addition to the reversible chemical-stimuli-responsive behavior. The presence of naphthalenediimide moieties at the backbone of the cage and the cationic nature of the cavity of the cage could be exploited to study the functional aspects of the gel. The porous gel exhibited the abilities to uptake pyrene as a guest and to selectively remove anionic dyes from aqueous solutions. The gel could bind representative anionic dyes like "acid blue 93" and "methyl orange" in the absence or presence of certain cationic dyes, making the material suitable for selective dye removal applications.

The pyridine-appended nonchelating bidentate ligands 1,4-bis(3-pyridyl)benzene (1) and 4,4'-bis(3-pyridyl) biphenyl (2) were complexed with a naked Pd(II) ion for the construction of molecular cage compounds. Prior to these experiments, the complexation of the ligands with cis-[Pd(en)(NO3)2] was also examined, because self-assemblies from the cis-protected Pd(II) ion were expected to be simple motifs that constitute the assemblies from naked Pd(II) ion. The structures of the self-assembled compounds resulting from 1 and [Pd(en)(NO3)2] depended on the solvent employed. In aqueous solution, an M2L2 trenchlike compound was obtained. In dimethyl sulfoxide, however, a mixture of the M2L2 trench and an M3L3 macrocycle was found in equilibrium, the dynamic nature of which was confirmed by the concentration-dependent nature of the species. At higher concentration, an M4L4 macrocycle was mostly observed. The complexation of 1 with naked Pd(II) ions was expected to produce novel structures that are combinations of the M(n)L(n) type frameworks. A peculiar tetrahedral M4L8 assembly was obtained quantitatively from 1 and Pd(NO3)2, rather than the smallest possible M3L6 double-walled triangle. Interestingly, the use of Pd(CF3SO3)2 resulted in the sole formation of the latter structure. Thus, the anion is important as a template in the formation of these assemblies. Ligand 2, which contains an extra p-phenylene unit compared to 1, behaved in a similar manner when treated with [Pd(en)(NO3)2], but showed subtle differences with naked Pd(II) ions. With Pd(NO3)2, 2 gave mostly a tetrahedron along with a double-walled triangle. With Pd(CF3SO3)2, this longer ligand formed a double-walled triangle with a negligible amount of tetrahedra. A single discrete assembly of a perfect tetrahedron was obtained from 2 and Pd(II) ions by choosing p-tosylate as a counterion.

The stability constants of Cu(II) complexes that consist of either an oxaaza macrocycle with two triamine moieties linked by dioxa chains, or two macrocyclic ligands with a polyamine chain which are connecting the 2 and 9 positions of phenanthroline, have been determined by means of potentiometric measurements. The results are compared to those reported for other ligands with a similar molecular architecture. Of the complexes that contain phenanthroline in their macrocycle, the Cu(II) ion of the complex with the smallest and most rigid macrocycle (L3) has an unsaturated coordination sphere, while in the complex with the largest macrocycle (L5) the Cu(II) ion is coordinatively almost saturated. These results are corroborated by the crystal structure of the [CuL5](ClO4)2 complex. The affinity of the ligands and the complexes towards nucleic acids was studied by measuring the changes in the melting temperature, which showed that the affinity of the macrocyclic ligands towards double-stranded DNA or RNA is generally smaller than that of their linear analogues that bear a similar charge, with a strong preference for polyA-polyU, a model for RNA. However, the complexes of two of the changed macrocyclic ligands which contain a phenanthroline unit (L4, L5) showed a distinctly larger increase in their melting temperature deltaTm with DNA (polydA-polydT), which is reversed again in favor of RNA upon metallation to the dinuclear copper complex with L5. Experiments with supercoiled plasmid DNA showed a particularly effective cleavage with a mononuclear Cu(II) complex that contains a phenanthroline unit (L6). Related ligands showed less activity towards DNA, but not so towards the biocidic bis(p-nitrophenyl)phosphate (BNPP). In both cases (with DNA and BNPP) the activity seemed to increase with decrease of coordinative saturation of the Cu(II) ion, with the exception of one particular ligand (L6). Experiments with radical scavengers in the DNA experiments showed some decrease in cleavage, which indicates the participation of redox processes.