| Square-planar d8platinum(Ⅱ) complexes show abundant spectroscopic properties, especially intriguing3MMLCT luminescence induced by Pt…Pt and π-π stacking interactions in their oligomeric structures. The3MMLCT luminescence usually occurs in the solid state. However, it is found to be nonemissive or weakly emissive in dilute aqueous solutions. The quenched excited states are attributed to efficient radiationless decay together with ionic solvation. It is always a hotspot to induce platinum(Ⅱ) complexes for higher ordered aggregates and thus controllable3MMLCT exited states in dilute solutions. We develop novel strategies to construct platinum(Ⅱ) aggregates by using supramolecular and dynamic hydrazone bond.1) The shift in the dissolution equilibrium can induce the reduction of the solubility and the ionization degree of the weak electrolyte upon the addition of the same salt ion into its solution. This universal physical phenomenon is defined as the common ion effect. In the corresponding solution, chloroplatinum(Ⅱ) complexes exist as monovalent cations ordinarily, which also follow the common ion effect as the weak electrolytes. On the other hand, ionic liquids are organic salts with wide liquid temperature ranges, negligibly small vapor pressure, low toxicity, high conductivity and excellent chemical and thermal stability, which are therefore applied excellently in the fields of green solvents, catalysis and functional materials. We synthesized three chloroplatinum(Ⅱ) complexes of2,6-bis(benzimidazol-2’-yl)pyridine (bzimpy) hexafluorophosphate salt bearing hexaethylene glycol groups. Upon the addition of equimolar different hexafluorophosphate salts to the dilute aqueous or ion liquid (BMIMPF6) solutions of the platinum(Ⅱ) complexes, Pt-2was found to show remarkable luminescence enhancement. And a remarkable quantum yield was achieved (0.46) after the addition NH4PF6, which even superiors to the values obtained from their solid state.2) Dynamic combinatorial library (DCL), constructed by the reversible nature of dynamic covalent bonds (disulfides, imines, Diels-Alder adducts et al), allows the exchange of molecular components to generate a dynamic library of products. The library composition can generate a new distribution of products so as to achieve a thermodynamic equilibrium of the system. Such a system is highly responsive to various physical and chemical stimuli, such as pH values, guest molecules, temperature, mechanical stress, solvent, etc. Because of excellent characters, including component exchanging, self-sorting, self-replicating and self-healing, we design a supramolecular polymer assembled by sulfonate-based acylhydrazone molecules via triple N-H…O hydrogen bonds in water. The electrostatic interaction between the negative supramolecular polyelectrolyte and positive platinum(Ⅱ) complexes leads to the formation of ordered oligomeric structures with remarkable3MMLCT luminescence enhancement. Based on the spectroscopic, DLS, and TEM data, the hydrazone component exchangings are discussed with the catalysis of different pH. Meanwhile, the controllable3MMLCT decays are achieved. Furthermore, upon the addition of9equiv. sodium2-formylbenzenesulfonate to the aldehyde exchange system, the emission intensity of the chloroplatinum(II) complex is recovered to78%in comparison to the initial date. Finally, tunable3MMLCT luminescence is realized by virtue of component exchanges of dynamic acylhydrazone.3) Supramolecular polymers, bridged via reversible noncovalent interactions, are a kind of dynamic materials by nature and undergo continuous assembly/disassembly processes. On basis of the dynamic and reversible nature of noncovalent interactions, supramolecular polymers possess a wide range of intriguing properties, such as degradability, shape-memory, self-healing, tunable polymerization degree and mechanical properties, making them unique candidates for conventional polymers. Complementary hydrogen bonds between barbituric acid (BA) and melamine (M) can form lots of supramolecular assemblies. The hydrogen-bond-directed assembly drives melamine and barbituric acid, in principle, to give rise to the formation of three different types of aggregates,(finite) cyclic rosettes,(infinite) linear tapes, or (infinite) crinkled tapes. We here combine luminescence of platinum(Ⅱ) complexes with complementary hydrogen bonds of BA and M in order to construct suprrmolecular polymer dyes with stimulative responsibility, adjustable phosphorescence emissions and rich morphologies. This work is in progress, so far. |
PDF Full Text Request