The development of molecular frameworks derived from binuclear platinum(II) aromatic Schiff base (salphen) complexes and their supramolecular chemistry have been undertaken. A series of axially rotating (Pt-salphen)₂ luminophores, tethered in a cofacial manner by a rigid linker (xanthene, 1; dibenzofuran, 2; biphenylene, 3), was synthesized in which the O(salphen) groups are potentially amenable for guest-binding. The molecular structures of 1 and 3 have been determined by X-ray crystallography, revealing intra- and intermolecular π-stacking interactions, as well as contrasting syn (1) and anti (3) configurations, for the (Pt-salphen)₂ moiety. All complexes are luminescent in solution at room temperature. Their photophysical and solvatochromic properties have been examined, and the emissions are assigned to mixed triplet O(p)/Pt(d)π*(diimine) excited states. The red-shifted fluid emissions and lower quantum yields of 1 and 3, relative to 2, are ascribed to enhanced intramolecular π-stacking interactions. Photophysical changes and selective responses to metal ions (particularly Pb²⁺) have been investigated by using various spectroscopic methods and DFT calculations, and through comparative studies with control complexes. A plausible binding mechanism is proposed based on occupation of the O(salphen)-binding cavity, which induces perturbation of intramolecular π–π interactions, and hence the self-quenching and emission properties, of the (Pt-salphen)₂ unit.

The nature and importance of CH⋅⋅⋅FC interactions is a topical yet controversial issue, and the development of spectroscopic methods to probe such contacts is therefore warranted. A series of Group 4 bis(benzyl) complexes supported by (σ-aryl)-2-phenolate-6-pyridyl [O,C,NR¹] ligands bearing a fluorinated R¹ group (CF₃ or F) in the vicinity of the metal has been prepared. The X-ray crystal structure of the CF₃-substituted Hf derivative features intramolecular C-H⋅⋅⋅F-C and Hf⋅⋅⋅F-C contacts. All complexes have been characterized by multinuclear NMR spectroscopy. The ¹H and ¹³C NMR spectra of [M(O,C,NCF₃)(CH₂Ph)₂] derivatives display coupling (assigned to ^1hJ_HF and ^2hJ_CF for Ti; ³J_HF and ²J_CF (through M⋅⋅⋅F) for Hf and Zr) between the benzyl CH₂ and CF₃ moieties. [¹H,¹⁹F]-HMBC NMR experiments have been performed for the M-[O,C,N-R¹] complexes and their [O,N,C] counterparts, revealing significant scalar coupling across the CH⋅⋅⋅FC interactions for Ti-[O,C,N] and [O,N,C] species.

The notion of weak attractive ligand–polymer interactions is introduced, and its potential application, importance, and conceptual links with “cooperative” ligand–substrate interactions are discussed. Synthetic models of weak attractive ligand–polymer interactions are described, in which intramolecular weak CH⋅⋅⋅FC interactions (the existence of which remains contentious) have been detected by NMR spectroscopy and neutron and X-ray diffraction experiments. These CH⋅⋅⋅FC interactions carry important implications for the design of catalysts for olefin polymerization, because they provide support for the practical feasibility of ortho-F⋅⋅⋅H_β ligand–polymer contacts proposed for living Group 4 fluorinated phenoxyimine catalysts. The notion of weak attractive noncovalent interactions between an “active” ligand and the growing polymer chain is a novel concept in polyolefin catalysis.