Platinum(II) complexes have square planar geometry that facilitates Pt‧‧‧Pt and π-π intermolecular interactions. This accounts for some cool properties such as tunable emission, self-assembly, stimuli-responsiveness, and solvatochromism.1
Our group uses platinium(II) complexes as building units to produce diverse metal-organic structures, such as macrocycles,2 linear polymers, and molecular emitters, all of which display intermolecular assembly (via Pt‧‧‧Pt or π-π interactions!). We have made Schiff base macrocycles that can form nanotubular assemblies,3 and synthesized a cyclometalated Pt(II) complex that shows solvatochromism in solid-state.4
Platinum containing species. (a) Chemical structures of Pt4 (left) and Pt3 (right) macrocycles. (b) Solid-state packing of Pt4 macrocycle with a side view of hexamer omitting peripheral substituents (left) and top-down view of single macrocycle with molecular dimensions (right). (c) Chemical structure of a cyclometalated Pt(II) complex and (d) solvatochromic behavior of this complex under exposure to different solvents.
The repeating units in traditional polymers (e.g. plastics or glass) are held together by strong covalent bonds. However, polymers can also be formed by linking units through weak interactions, such as H-bonding or π-π stacking; these are known as supramolecular polymers and we also make them in our lab!
We have used pentiptycene building blocks as repeating units to produce prospective molecular motors and diamondoid networks, relying on either charge-assisted hydrogen bonds or O-H···anion interactions.1,2 Moreover, we synthesize metal-organic structures3 and biomolecules and use them as monomers to fabricate tubes, sheets, and helical nanofibers, which could have potential applications in sensing, gas storage and catalysis.
Monomers and supramolecular polymers. Various structures obtained from supramolecular polymers synthesized in our lab: (a) 3-D diamondoid pentiptycene network, (b) 2-D sheetlike supramolecular polymer, (c) 1D helical nanofibers obtained from Zn-salophen complexes.
Rotaxanes are mechanically bound, interlocked species composed of a ring that encircles a dumbbell-shaped molecule. Although conventional rotaxanes cannot separate into the ring and dumbbell elements without breaking a covalent bond, the precise molecular design of both components allows rotaxanes to dissociate on demand by applying the right stimulus.
Using this concept, we have designed and synthesized rotaxanes that are programmed to dissociate, and once the loose components appear, they undergo either a supramolecular1 or chemical2 transformation. We are using this approach to develop new functional materials that exhibit unusual reactivity and modes of self-assembly.
Stimulation of a metastable rotaxane. Sequenced dissociation followed by molecular recognition.
Condensation of a primary amine with a carbonyl results in the formation of an imine group. Specifically, reacting salicylaldehyde with o-phenylenediamine (or o-hydroxyaniline) results in the formation of salphen 1 (or hemisalphen 2), which are famous ligands in coordination chemistry.
Our group makes macrocycles that contain those ligands, such as 3 (which we call a [3+3] macrocycle: 3 aldehyde units + 3 amine blocks = macrocycle), and 4, a “campestarene” (from the latin campester meaning flat).1,2 We use these conjugated and planar macrocycles for the binding of metals, which results in a variety of intriguing structures such as cluster complexes,3 capsules,4 and nanotubes.5 We have recently discovered that the use of uranyl clusters as inorganic templates results in cavity expansion! (5 and 6).6
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MacLachlan Group 2025.
