Sunlight-Induced Covalent Marriage of Two Triply Interlocked Pd₆ Cages and Their Facile Thermal Separation

A template-free triply interlocked Pd₆ cage (<b>2</b>) was synthesized by two-component self-assembly of <i>cis</i>-blocked 90° acceptor <i>cis-</i>(tmen)­Pd­(NO₃)₂ (<b>M</b>) and 1,3,5-tris­((<i>E</i>)-2-(pyridin-3-yl)­vinyl)­benzene (<b>L</b>). Assembly <b>2</b> was characterized by ¹H NMR and ESI-MS, and the structure was confirmed by X-ray crystallography, which revealed a parallel conformation of the olefin double bonds belonging to the adjacent cages in the solid state at a distance of 3.656 Å, thereby indicating the feasibility of [2+2] photochemical reaction. Two adjacent interlocked cages were covalently married together by intermolecular [2+2] cycloaddition in a single crystal-to-single crystal fashion upon exposure to sunlight/UV irradiation. Most surprisingly, the covalently married pair was easily separated thermally in aqueous medium under mild reaction conditions

New Structural Topologies in a Series of 3d Metal Complexes with Isomeric Phenylenediacetates and 1,3,5-Tris(1-imidazolyl)benzene Ligand: Syntheses, Structures, and Magnetic and Luminescence Properties

In this article we present the syntheses, characterizations, magnetic and luminescence properties of five 3d-metal complexes, [Co­(tib)­(1,2-phda)]_<i>n</i>­·(H₂O)_<i>n</i> (<b>1</b>), [Co₃(tib)₂­(1,3-phda)₃­(H₂O)]_<i>n</i>­·(H₂O)_2<i>n</i> (<b>2</b>), [Co₅(tib)₃­(1,4-phda)₅­(H₂O)₃]_<i>n</i>­·(H₂O)_7<i>n</i> (<b>3</b>), [Zn₃(tib)₂­(1,3-phda)₃]_<i>n</i>­·(H₂O)_4<i>n</i> (<b>4</b>), and [Mn­(tib)₂­(H₂O)₂]_<i>n</i>­·(1,4-phdaH)_2<i>n</i>­·(H₂O)_4<i>n</i> (<b>5</b>), obtained from the use of isomeric phenylenediacetates (phda) and the neutral 1,3,5-tris­(1-imidazolyl)­benzene (tib) ligand. Single crystal X-ray structures showed that <b>1</b> constitutes 3,5-connected 2-nodal nets with a double-layered two-dimensional (2D) structure, while <b>2</b> forms an interpenetrated 2D network (3,4-connected 3-nodal net). Complex <b>3</b> has a complicated three-dimensional structure with 10-nodal 3,4,5-connected nets. Complex <b>4</b>, although it resembles <b>2</b> in stoichiometry and basic building structures, forms a very different overall 2D assembly. In complex <b>5</b> the dicarboxylic acid, upon losing only one of the acidic protons, does not take part in coordination; instead it forms a complicated hydrogen bonding network with water molecules. Magnetic susceptibility measurements over a wide range of temperatures revealed that the metal ions exchange very poorly through the tib ligand, but for the Co­(II) complexes the effects of nonquenched orbital contributions are prominent. The 3d¹⁰ metal complex <b>4</b> showed strong luminescence with λ_max = 415 nm (for λ_ex = 360 nm)

Covalent Postassembly Modification and Water Adsorption of Pd₃ Self-Assembled Trinuclear Barrels

Three new ditopic imidazole ligands (<b>2</b>–<b>4</b>) were synthesized in high yields and characterized by various spectroscopic techniques. These ligands resulted in the formation of [3 + 6] self-assembled trinuclear barrels (<b>5</b>–<b>7</b>) in quantitative yields by stoichiometric combination of individual ligands and Pd­(NO₃)₂ in DMSO. All the three assemblies (<b>5</b>–<b>7</b>) were characterized by ¹H NMR and ESI-MS analysis, and subsequently, structures of the complexes <b>5</b> and <b>6</b> were confirmed by single-crystal X-ray diffraction studies. Structure analysis reveals the presence of NO₃^– counteranions in the intermolecular channels/pockets, which could potentially act as H-bonding sites between adsorbed water molecules within the channels. In fact, both the assemblies (<b>5</b> and <b>6</b>) showed water uptake (136.58, and 123.78 cm³ g^–1, respectively) at ambient temperature under maximum allowable humidity. In addition, free aldehyde group present in the bridging ligand in complex <b>7</b> provides reactive site for postassembly modification. Herein, Knoevenagel condensation with Meldrum’s acid was utilized under mild conditions by targeting aldehyde group appended in prefabricated complex <b>7</b> and transformed into a different complex (<b>8</b>) with altered functional group. Such postassembly functionalization enables incorporation of a new functional group without disrupting the integrity of the trifacial structure

Covalent Postassembly Modification and Water Adsorption of Pd₃ Self-Assembled Trinuclear Barrels

Three new ditopic imidazole ligands (<b>2</b>–<b>4</b>) were synthesized in high yields and characterized by various spectroscopic techniques. These ligands resulted in the formation of [3 + 6] self-assembled trinuclear barrels (<b>5</b>–<b>7</b>) in quantitative yields by stoichiometric combination of individual ligands and Pd­(NO₃)₂ in DMSO. All the three assemblies (<b>5</b>–<b>7</b>) were characterized by ¹H NMR and ESI-MS analysis, and subsequently, structures of the complexes <b>5</b> and <b>6</b> were confirmed by single-crystal X-ray diffraction studies. Structure analysis reveals the presence of NO₃^– counteranions in the intermolecular channels/pockets, which could potentially act as H-bonding sites between adsorbed water molecules within the channels. In fact, both the assemblies (<b>5</b> and <b>6</b>) showed water uptake (136.58, and 123.78 cm³ g^–1, respectively) at ambient temperature under maximum allowable humidity. In addition, free aldehyde group present in the bridging ligand in complex <b>7</b> provides reactive site for postassembly modification. Herein, Knoevenagel condensation with Meldrum’s acid was utilized under mild conditions by targeting aldehyde group appended in prefabricated complex <b>7</b> and transformed into a different complex (<b>8</b>) with altered functional group. Such postassembly functionalization enables incorporation of a new functional group without disrupting the integrity of the trifacial structure

A Pd₂₄ Pregnant Molecular Nanoball: Self-Templated Stellation by Precise Mapping of Coordination Sites

We found that Pd­(II) ion (<b>M</b>) and the smallest 120° bidentate donor pyrimidine (<b>L</b>_<b>a</b>) self-assemble into a mononuclear <b>M</b>(<b>L</b>_<b>a</b>)₄ complex (<b>1a</b>) instead of the expected smallest <b>M</b>₁₂(<b>L</b>_<b>a</b>)₂₄ molecular ball (<b>1</b>), presumably due to the weak coordination nature of the pyrimidine. To construct such a pyrimidine bridged nanoball, we employed a new donor tris­(4-(pyrimidin-5-yl)­phenyl)­amine (<b>L</b>); which upon selective complexation with Pd­(II) ions resulted in the formation of a pregnant <b>M</b>₂₄<b>L</b>₂₄ molecular nanoball (<b>2</b>) consisting of a pyrimidine-bridged Pd₁₂ baby-ball supported by a Pd₁₂ larger mother-ball. The formation of the baby-ball was not successful without the support of the mother-ball. Thus, we created an example of a self-assembly where the inner baby-ball resembling to the predicted <b>M</b>₁₂(<b>L</b>_<b>a</b>)₂₄ ball (<b>1</b>) was incarcerated by the giant outer mother-ball by means of geometrical constraints. Facile conversion of the pregnant ball <b>2</b> to a smaller <b>M</b>₁₂(<b>L</b>_<b>b</b>)₂₄ ball <b>3</b> with dipyridyl donor was achieved in a single step

A Pd₂₄ Pregnant Molecular Nanoball: Self-Templated Stellation by Precise Mapping of Coordination Sites

We found that Pd­(II) ion (<b>M</b>) and the smallest 120° bidentate donor pyrimidine (<b>L</b>_<b>a</b>) self-assemble into a mononuclear <b>M</b>(<b>L</b>_<b>a</b>)₄ complex (<b>1a</b>) instead of the expected smallest <b>M</b>₁₂(<b>L</b>_<b>a</b>)₂₄ molecular ball (<b>1</b>), presumably due to the weak coordination nature of the pyrimidine. To construct such a pyrimidine bridged nanoball, we employed a new donor tris­(4-(pyrimidin-5-yl)­phenyl)­amine (<b>L</b>); which upon selective complexation with Pd­(II) ions resulted in the formation of a pregnant <b>M</b>₂₄<b>L</b>₂₄ molecular nanoball (<b>2</b>) consisting of a pyrimidine-bridged Pd₁₂ baby-ball supported by a Pd₁₂ larger mother-ball. The formation of the baby-ball was not successful without the support of the mother-ball. Thus, we created an example of a self-assembly where the inner baby-ball resembling to the predicted <b>M</b>₁₂(<b>L</b>_<b>a</b>)₂₄ ball (<b>1</b>) was incarcerated by the giant outer mother-ball by means of geometrical constraints. Facile conversion of the pregnant ball <b>2</b> to a smaller <b>M</b>₁₂(<b>L</b>_<b>b</b>)₂₄ ball <b>3</b> with dipyridyl donor was achieved in a single step