Francesco Lelj

Platinum(II) complexes have been thoroughly researched for applications in bioimaging and optoelectronics, often searching for potential uses after observing a complex's unique properties. Here, we investigate the role of the bridging atom on the resulting photophysical properties, comparing two tetradentate complexes bearing O and N elemental bridges between 2-phenylpyridine (phpy) units to the well-known unbridged Pt(phpy)₂. Unlike the O-bridged complex, single-crystal X-ray diffraction demonstrated no Pt···Pt interactions for the N-bridged complex in the solid state. As anticipated, the introduction of a bridging atom turns on room-temperature phosphorescence. Absorption and emission spectroscopy combined with density functional theory (DFT) calculations explained that the blue-shifted spectra of the O-bridged complex are a result of HOMO stabilization by the more electronegative bridging atom. The minor differences were found to result in macroscopic differences in the properties of the bridged complexes in the solid state and when aggregated. Notably, the N-bridged complex experienced significant aggregation-caused quenching, whereas the O-bridged complex displayed red-to-green aggregation-induced emission switching resulting from excimer emission. In this work, we investigate the photophysical properties of the core structures for a popular family of Pt complexes in hopes of streamlining the rational design of new functional molecules.

The field of platinum chemistry is ubiquitous in the research of anticancer drugs and new OLED materials. Within the vast library of existing compounds, the majority of work focuses on complexes in the +2 and +4 oxidation states, with comparatively few examples of Pt^III complexes reported without bridging ligands. Pt^III complexes with metal‐metal bonding can be made by mild oxidation of Pt^II complexes having bis(phenylpyridine) ligands. Here, we report the synthesis and characterization of two new Pt^II complexes bearing tetradentate N‐bridged bis(phenylpyridine) ligands with N^C*C^N and C^N*N^C coordinating atoms. Through chemical oxidation with PhICl₂ and N‐chlorosuccinimide, we obtained four new complexes containing Pt^IV and Pt^III centres. The dynamics of the Pt^III complexes were explored by variable‐temperature NMR studies and showed surprisingly free rotation of the appended N‐aryl group. This work uncovers the importance of the destabilizing nature of the bulky N‐aryl group on intermetallic bonds, and sheds light on how the molecular rotation observed in the Pt^III compounds could inspire new molecular rotors driven by intermetallic bonds.

Post‐synthetic modification of mechanically interlocked molecules (MIMs) is an attractive avenue to add complexity to already intricate systems. This remains an important, challenging topic that is under‐developed. In this paper, we report the synthesis and characterization of a [2]rotaxane molecule featuring a ring appended to an emissive cyclometalated Pt ^II unit. Modulation of the oxidation state at the metal center can transform the interlocked molecule into a new Pt ^IV [2]rotaxane or a Pt ^III [3]rotaxane held together by an intermetallic Pt−Pt bond – a first of its kind. These molecules display distinct structural and photophysical properties, as well as shuttling dynamics. This approach for post‐synthetic modification could be used to construct more complex MIMs and inorganic supramolecular assemblies with redox properties.

Post‐synthetic modification of mechanically interlocked molecules (MIMs) is an attractive avenue to add complexity to already intricate systems. This remains an important, challenging topic that is under‐developed. In this paper, we report the synthesis and characterization of a [2]rotaxane molecule featuring a ring appended to an emissive cyclometalated Pt ^II unit. Modulation of the oxidation state at the metal center can transform the interlocked molecule into a new Pt ^IV [2]rotaxane or a Pt ^III [3]rotaxane held together by an intermetallic Pt−Pt bond – a first of its kind. These molecules display distinct structural and photophysical properties, as well as shuttling dynamics. This approach for post‐synthetic modification could be used to construct more complex MIMs and inorganic supramolecular assemblies with redox properties.

Cyclometalated platinum complexes play a crucial role in catalysis, bioimaging, and optoelectronics. Phenylpyridines are widespread cyclometalating ligands that generate stable and highly emissive Pt complexes. While it is common practice to modify these ligands to fine-tune their photophysical properties, the incorporation of polycyclic aromatic hydrocarbons into the ligand's structure has been largely overlooked. This report describes the cyclometalation of naphthalenyl- and anthracenylpyridine ligands, which has resulted in ten new luminescent Pt^II and Pt^IV complexes. These species are enabled by a dual-binding behavior discovered in our polyaromatic-containing ligands. The introduction of naphthalenyl and anthracenyl groups unlocks dual binding modes, with the Pt center bonding to either of two distant carbon atoms within the ligand. These complexes exhibit both symmetric structures with two 5-membered metallacycles and asymmetric structures with 5- and 6-membered metallacycles. This work presents a strategy for the regioselective synthesis of Pt complexes with bespoke structures and photophysical properties. Our findings offer new opportunities in platinum chemistry and beyond, with potential implications for materials and technologies.

Complexes [MCl₂Cp*]₂ (M=Ir, Rh), [RuCl₂(p‐cymene)]₂ and [Ir(C^N)₂Cl]₂ (HC^N=a, phenylpyridine ; b, phenylpyrazole,) react with imine ligands derived from ο‐aminophenol to yield complexes with an exocyclic C=N bond which has a cis or trans configuration. The trans isomer is favoured except for sterically crowded complexes Cp*M (M=Ir, Rh) when the imine has a mesityl substituent, for which the cis isomer is favoured. The complexes undergo photoisomerisation in visible light but revert back to the original isomer over time or when heated. The rate of the thermal reverse isomerisation depends on the imine substituent and the metal fragment. DFT calculations correctly reproduce the favoured isomer and suggest that the reverse isomerisation occurs by a rehybridisation at the N atom as found in organic imines. In addition, a triplet state, thermally accessible by a Minimum Energy Crossing Point (MECP) provides a low energy pathway for reverse isomerisation in the case of the half‐sandwich complexes.

Metal‐metal bonds have rarely been explored as active elements in supramolecular assemblies despite their unique potential to introduce responsive behavior. In this report, a dynamic molecular container composed of two cyclometalated Pt units is constructed using Pt−Pt bonds. This molecule—the flytrap—has a flexible jaw composed of two [18]crown‐6 ethers that can adapt their shape to bind large inorganic cations with sub‐micromolar affinity. Along with the spectroscopic and crystallographic characterization of the flytrap, we report its photochemical assembly, which allows the capture of ions and their transport from solution to the solid state. In addition, we have been able to recycle the flytrap to regenerate its starting material due to the reversible nature of the Pt−Pt bond. We believe that other molecular containers and materials for harvesting valuable substrates from solution could be assembled using the advances presented here.