Design, Synthesis And Photophysical Studies Of Photochromic Spirooxazine-Containing Ligands And Their Zinc(Ⅱ) And Rhenium(Ⅰ) Complexes

Photochromism is a chemistry and physical phenomenon and involves photo-chemistry and physical reaction that are relevant to the field of organic chemistry, inorganic chemistry, biochemistry and macromolecular science. In the development and investigation of organic photochromism and its material properties, spirooxazine is one of the well-known families of photochromic molecules which provide good photo-stability and high fatigue resistance properties and was studied widely. However, the studies of all these systems are confined to pure organic systems with very few precedents in the incorporation of such moieties into the metal-containing inorganic or organometallic counterparts. It is envisaged that incorporation of the photochromic moieties into the metal-containing framework would provide a new and alternative approach towards the design and synthesis of new photochromic materials with perturbed properties.Firstly, a spirooxazine-containing 2,2'-bipyridine ligand (L1) and a series of its zinc(II) thiolate complexes (1a–1e) have been designed and successfully synthesized. Their photophysical and photochromic properties in solution were studied. Upon excitation by UV light, all the ligands and complexes exhibit photochromic behavior. On conversion to the open photomerocyanine (PMC) form by UV excitation, the ligands and all zinc complexes display luminescence at ca. 720 nm in EtOH–MeOH (4:1 v/v) glass at 77 K. The thermal bleaching kinetics of the ligands and the complexes were studied in DMF at various temperatures. A linear relationship between the activation enthalpy and entropy was seen and an isokinetic temperature of 295.4±1.5 K was estimated. The photochemical quantum yields for the photochromic reactions of the ligands and complexes were also determined.In addition, a long hydrocarbon chain-containing spirooxazine (L2) and its zinc(II) bis-thiolate complex (2a) were synthesized for preparation of LB film. Photochromic properties of the LB film were also studied. Luminescent spirooxazine-containing Re(I) complexes with long hydrocarbon chains (Re-1, Re-2) were synthesized, and their photophysical and photochromic properties in solution and film (LB film and cast film) were studied. Both the UV-visible absorption and luminescence intensity of the LB films and cast films were found to be changed with ultraviolet light (365 nm) and visible light (610 nm) irradiation.Polyoxometalates (POMs) are the polyoxoanion of the early transition elements, especially vanadium, molybdenum and tungsten. They are discrete and uniform cluster anions that assembled from small metal oxysalt fragments in water solution with a certain pH value. The variety of their composition and structures endowed them with many functional properties, such as catalysis, proton conductivity, nonlinear optics, medicine, photophysics and magnetism. However, the development of materials and devices based on POMs was restricted because of their higher lattice energies, lower stability and poor processibility. In is necessary that new methods should be explored to combine, position and orient the clusters, indicative of the physical and chemical properties of the POMs. Organic/inorganic complex can be formed by using cationic surfactants to replace the counterions covered on the surface of POMs, it can be regarded as a novel supra-molecular soft material. Recent reports suggested that the different functions of the assembly are a direct result of the structure formed. However, the cationic surfactants employed are usually pure organic systems and cationic surfactants containing metal centers were rarely used. In chapter 4, rhenium (I) bipyridine surfactants with positively charged groups (RebpyNC₁₈) were designed and synthesized. It showed strong 3MLCT [Re(dÏ€)→π*(diimine)] luminescence. Different polyoxometalates [H₃PW₁₂O₄₀, H₄SiW₁₂O₄₀, Na₉EuW₁₀O₃₆, K₁₃Eu(SiW₁₁O₃₆)₂] were encapsulated with RebpyNC18 surfactant and the photophysical properties of the these SECs were studied. Different polyoxometalates were shown to change the luminescence properties of the Re(I)-bipyridine complexes.In summary, photochromic spirooxazine-containing ligands and their zinc(II) and rhenium(I) complexes were designed, synthesized and their photochromic properties in solution and films were studied. Surfactants containing rhenium(I) have been used to encapsulate different types of POMs and their luminescence properties have been found to be influenced by the nature of the POMs.