Yongguang Li

Synthesis, Characterization, and the Photochromic, Luminescence, Metallogelation and Liquid‐Crystalline Properties of Multifunctional Platinum(II) Bipyridine Complexes

A series of multifunctional platinum(II) bipyridine complexes were designed, synthesized, and characterized by (1)H NMR, fast atom bombardment mass spectrometry (FAB-MS), and elemental analysis. Their electrochemical and photophysical properties were investigated. The photochromic properties of the spironaphthoxazine-containing complexes were also studied. Some of these complexes were shown to be capable of forming stable thermoreversible metallogels in organic solvents. In contrast to typical thermotropic organogels and metallogels, one of the complexes could form metallogels in dodecane and is very stable towards external stimuli. The photochromic activation parameters for the bleaching reaction of a representative spironaphthoxazine-containing complex in a dodecane gel were determined through kinetic studies at various temperatures. Lamellar liquid-crystalline behavior was also observed in one of the complexes, and the liquid-crystalline properties were studied by thermogravimetry analysis (TGA), polarized optical microscopy (POM), differential scanning calorimetry (DSC), variable-temperature X-ray diffraction (XRD), and variable-temperature infrared (IR) spectroscopy.

Cholesterol-/estradiol-appended alkynylplatinum(II) complexes as supramolecular gelators: synthesis, characterization, photophysical and gelation studies.

A series of cholesterol-/estradiol-appended alkynylplatinum(II) complexes with tridentate N-donor ligands, based on 2,6-bis(1-alkylpyrazol-3-yl)pyridine, has been synthesized and characterized by (1)H NMR spectroscopy, FAB-mass spectrometry, and elemental analysis. Their photophysical properties have also been investigated. Computational studies have been performed to provide insights into the nature of the electronic transitions. Some of the complexes have been found to form stable thermo- and mechanoresponsive supramolecular gels.

Supramolecular Self-Assembly and Dual-Switch Vapochromic, Vapoluminescent, and Resistive Memory Behaviors of Amphiphilic Platinum(II) Complexes

A series of amphiphilic platinum(II) complexes with tridentate N-donor ligands has been synthesized and characterized. Different supramolecular architectures are constructed using the amphiphilic molecules as the building blocks through the formation of Pt···Pt and π-π stacking interactions in aqueous media. The aggregation-deaggregation-aggregation self-assembly behavior together with obvious spectroscopic changes could be fine-tuned by the addition of THF in aqueous media. More interestingly, one of the complexes is found to show fast response and high selectivity toward alcohol and water vapors with good reversibility, leading to drastic color and luminescence changes, and hence unique dual switching behavior, with the water molecules readily displaced by the alcohol vapor. Rapid writing and erasure have been realized via the control of a jet or a stream of alcohol vapor flow. In addition, it has been employed as active materials in the fabrication of small-molecule solution-processable resistive memory devices, exhibiting stable and promising binary memory performance with threshold voltages of ca. 3.4 V, high ON/OFF ratios of up to 105 and long retention times of over 104 s. The vapochromic and vapoluminescent materials are demonstrated to have potential applications in chemosensing, logic gates, VOC monitoring, and memory functions.

Helical Self-Assembly and Photopolymerization Properties of Achiral Amphiphilic Platinum(II) Diacetylene Complexes of Tridentate 2,6-Bis(1-alkylpyrazol-3-yl)pyridines

Amphiphilic platinum(II) diacetylene complexes of the 2,6-bis(1-butylpyrazol-3-yl)pyridine pincer ligand were designed and synthesized. Helical fibrous nanostructures were obtained through supramolecular assembly of the achiral platinum(II) diacetylene complexes via intermolecular hydrogen bonding, amphiphilic effects, Pt···Pt interactions, and π-π stacking interactions. In situ post-photopolymerization of the diacetylene unit was shown to occur in the preorganized helical fibers.

Directional Self-Assembly and Photoinduced Polymerization of Diacetylene-Containing Platinum(II) Terpyridine Complexes

A series of newly designed and synthesized diacetylene-containing platinum(II) terpyridine complexes exhibited intriguing self-assembly properties. Facilitated by Pt⋅⋅⋅Pt, π-π stacking, hydrogen-bonding and hydrophobic-hydrophobic interactions, these complexes are preorganized to readily undergo topochemical polymerization reactions upon photoirradiation. The in situ polymerization of the diacetylene units to form polydiacetylene, indicated by the UV/Vis spectral changes, gel permeation chromatography and dynamic light scattering, was found to alter their assembly behaviours, as revealed by TEM images.

Solvent-Induced and Temperature-Promoted Aggregation of Bipyridine Platinum(II) Triangular Metallacycles and Their Near-Infrared Emissive Behaviors

A series of bipyridine platinum(II) complexes with different sizes of triangular metallacycles and alkyl/oligoether chains has been synthesized and characterized. They are packed in a zig-zag fashion with the formation of dimeric structures according to their X-ray crystal structures. Different emission origins are observed due to the different sizes of the triangular ligands. Their morphologies could be tuned by the modification of the molecular structures with different metallacyclic alkynyl ligands and alkyl/oligoether chains and solvents. More interestingly, unusual electronic absorption changes and upfield shifts of the aromatic proton resonances are observed upon increasing the temperature, suggesting further aggregation of the architectures. Near-infrared (NIR) emission is also realized through the tuning of the π-π stacking, Pt⋅⋅⋅Pt interactions, and the packing of planar metallacycles.