Miguel A. Soto

Cellulose nanocrystal gels containing deep eutectic solvents and paraquat function as stable radical reservoirs. The materials undergo colour changes upon UV-irradiation, and may be used to create patterned photonic materials.

Counterfeiting has emerged as an increasingly severe global concern, posing significant threats to the security of individuals and society. In this study, a series of multilayered information‐encrypted composite materials is developed by embedding a chiral nematic cellulose nanocrystal ( cn ‐CNC) film inside a shape‐memory polymer (SMP) matrix to produce pressure‐responsive photonic crystals. The design also incorporates a cellulose acetate film, as a thermoset information carrier, and graphene oxide (GO), as a secrecy filter. In its initial state, the composite shows no information, while a pattern becomes visible to reveal the information upon hot‐pressing, due to the region‐dependent differences in its photonic responsiveness caused by the rigid pattern. A discernible mark remains even after recovery, serving as tangible evidence of the decrypted information. Moreover, the high color fidelity of these materials is confirmed using reflectance spectroscopy and color analysis over multiple cycles, demonstrating their potential in cyclic information encryption. By harnessing thermal and mechanical stimuli for anti‐counterfeiting purposes, these composites diversify the strategies available for information encryption.

Pseudorotaxanes are host‐guest complexes where a guest molecule threads through a ring‐shaped host via noncovalent interactions. If the guest has two recognition sites, the host can dynamically shuttle between them. These complexes enable stimulus‐responsive molecular shuttles, where a stimulus, such as pH change, can control the position of the host, affecting properties like color and solubility. In this study, a guest molecule ( Gc ) with two recognition sites—1,4‐dialkoxyphenylene and pH‐sensitive 1,5‐diaminonaphthalene—is synthesized. These sites interact strongly with cyclobis(paraquat‐ p ‐phenylene) ( CBPQT ^{4 +} ), a cationic host. CBPQT ^{4 +} binds to the neutral diaminonaphthalene group to produce a green solution. Upon protonation of the diaminonaphthalene group, the host shifts to the dialkoxyphenylene site, turning the solution light orange. This color‐switching behavior remains stable over multiple protonation‐deprotonation cycles. The pseudorotaxane complex can also be disassembled via slow solvent diffusion, allowing recovery of the Gc and CBPQT ^{4 +} components. Additionally, cellulose nanocrystal films incorporating the Gc ⊂ CBPQT ^{4 +} complex show similar green‐to‐orange color shifts, demonstrating their potential for information encryption applications.

Electro-switchable chiral nematic films are developed by functionalizing CNCs with viologen derivatives. The films show electrochromic and chiroptical responses, and multi-responsiveness to heat, light, and base for smart optical applications.

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.

Combining methyl viologen dichloride with cellulose nanocrystals gave UV-responsive photochromic films that were applied to encrypton and sensing.

Humankind's manipulation of platinum dates back more than two millennia to burial objects. Since then, its use has evolved from purely decorative purposes in jewelry to more functional applications such as in catalysts, pharmaceuticals, and bioimaging agents. Platinum offers a range of properties arguably unmatched by any other metal, including electroactivity, photoluminescence, chromic behaviour, catalysis, redox reactivity, photoreactivity, and stimuli-controlled intermetallic interactions. The vast body of knowledge generated by the exploration of these and other properties of platinum has recently merged with other areas of chemistry such as supramolecular and host–guest chemistry. This has shown us that platinum can incorporate its responsive character into supramolecular assemblies (e.g., macrocycles and polymers) to produce materials with tailorable functions and responses. In this Perspective Article, we cover some platinum-powered supramolecular structures reported by us and others, hoping to inspire new and exciting discoveries in the field.