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Due to the reversible nature of coordination bonds and solvation effect, coordination self‐assembly pathways are often difficult to elucidate experimentally in solution, as intermediates and products are in constant equilibration. The present study shows that some of these transient and high‐energy self‐assembly intermediates can be accessed by means of ball‐milling approaches. Among them, highly aqueous‐unstable Pd3L11 and Pd6L14 open‐cage intermediates of the framed Fujita Pd6L14 cage and Pd2L22, Pd3L21 and Pd4L22 intermediates of Mukherjee Pd6L24 capsule are successfully trapped in solid‐state, where Pd=tmedaPd2+, L1=2,4,6‐tris(4‐pyridyl)‐1,3,5‐triazine and L2=1,3,5‐tris(1‐imidazolyl)benzene). Their structures are assigned by a combination of solution‐based characterization tools such as standard NMR spectroscopy, DOSY NMR, ESI‐MS and X‐ray diffraction. Collectively, these results highlight the opportunity of using mechanochemistry to access unique chemical space with vastly different reactivity compared to conventional solution‐based supramolecular self‐assembly reactions. [ABSTRACT FROM AUTHOR]

Recently, polymer mechanochemistry has attracted much scientific interest due to its potential to develop degradable polymers. When the two ends of a polymer chain experience a linear pulling stress, molecular strain builds up, at sufficiently strong force, a bond scission of the weakest covalent bond results. In contrast, bond‐breaking events triggered by conformational stress are much less explored. Here, we discovered that a Zn salen complex would undergo conformational switching upon allosteric complexation with alkanediammonium guests. By controlling the guest chain length, the torsional strain experienced by Zn complex can be modulated to induce bond cleavage with chemical stimulus, and reactivity trend is predicted by conformational analysis derived by DFT calculation. Such strain‐release reactivity by a Zn(salen) complex initiated by guest binding is reminiscent of conformation‐induced reactivity of enzymes to enable chemical events that are otherwise inhibited. [ABSTRACT FROM AUTHOR]

Pd‐based molecular square Pd4L4 and triangle Pd3L3 represent the molecular ancestors of metal‐coordination polyhedra that have been an integral part of the field for the last 30 years. Conventional solution‐based reactions between cis‐protected Pd ions and 2,2′‐bipyridine exclusively give Pd4L4 and/or Pd3L3 as the sole products. We herein show that, under solvent‐free mechanochemical conditions, the self‐assembly energy landscape can be thermodynamically manipulated to form an elusive cyclic dimer Pd2L2 for the first time. In the absence of solvent, Pd2L2 is indefinitely stable in the solid‐state, but converts rapidly to its thermodynamic products Pd3L3 and Pd4L4 in solution, confirming Pd2L2 as a short‐lived kinetic species in the solution‐based self‐assembly process. Our results highlight how mechanochemistry grants access to a vastly different chemical space than available under conventional solution conditions. This provides a unique opportunity to isolate elusive species in self‐assembly processes that are too reactive to both "see" and "capture". [ABSTRACT FROM AUTHOR]

Pd‐based molecular square Pd4L4 and triangle Pd3L3 represent the molecular ancestors of metal‐coordination polyhedra that have been an integral part of the field for the last 30 years. Conventional solution‐based reactions between cis‐protected Pd ions and 2,2′‐bipyridine exclusively give Pd4L4 and/or Pd3L3 as the sole products. We herein show that, under solvent‐free mechanochemical conditions, the self‐assembly energy landscape can be thermodynamically manipulated to form an elusive cyclic dimer Pd2L2 for the first time. In the absence of solvent, Pd2L2 is indefinitely stable in the solid‐state, but converts rapidly to its thermodynamic products Pd3L3 and Pd4L4 in solution, confirming Pd2L2 as a short‐lived kinetic species in the solution‐based self‐assembly process. Our results highlight how mechanochemistry grants access to a vastly different chemical space than available under conventional solution conditions. This provides a unique opportunity to isolate elusive species in self‐assembly processes that are too reactive to both "see" and "capture". [ABSTRACT FROM AUTHOR]

Pd‐based molecular square Pd4L4 and triangle Pd3L3 represent the molecular ancestors of metal‐coordination polyhedra that have been an integral part of the field for the last 30 years. Conventional solution‐based reactions between cis‐protected Pd ions and 2,2′‐bipyridine exclusively give Pd4L4 and/or Pd3L3 as the sole products. We herein show that, under solvent‐free mechanochemical conditions, the self‐assembly energy landscape can be thermodynamically manipulated to form an elusive cyclic dimer Pd2L2 for the first time. In the absence of solvent, Pd2L2 is indefinitely stable in the solid‐state, but converts rapidly to its thermodynamic products Pd3L3 and Pd4L4 in solution, confirming Pd2L2 as a short‐lived kinetic species in the solution‐based self‐assembly process. Our results highlight how mechanochemistry grants access to a vastly different chemical space than available under conventional solution conditions. This provides a unique opportunity to isolate elusive species in self‐assembly processes that are too reactive to both "see" and "capture". [ABSTRACT FROM AUTHOR]

Pd‐based molecular square Pd4L4 and triangle Pd3L3 represent the molecular ancestors of metal‐coordination polyhedra that have been an integral part of the field for the last 30 years. Conventional solution‐based reactions between cis‐protected Pd ions and 2,2′‐bipyridine exclusively give Pd4L4 and/or Pd3L3 as the sole products. We herein show that, under solvent‐free mechanochemical conditions, the self‐assembly energy landscape can be thermodynamically manipulated to form an elusive cyclic dimer Pd2L2 for the first time. In the absence of solvent, Pd2L2 is indefinitely stable in the solid‐state, but converts rapidly to its thermodynamic products Pd3L3 and Pd4L4 in solution, confirming Pd2L2 as a short‐lived kinetic species in the solution‐based self‐assembly process. Our results highlight how mechanochemistry grants access to a vastly different chemical space than available under conventional solution conditions. This provides a unique opportunity to isolate elusive species in self‐assembly processes that are too reactive to both "see" and "capture". [ABSTRACT FROM AUTHOR]