Syntheses, Structures And Photochromic Properties Of Dicarboxyl-containing Spiropyrans And Their Metal Complexes

Spiropyrans have been attached much attention, due to their potential applications in many areas such as photochromic spectacles, optical data storage, molecular switches, and biosensors. But most previous work was limited to the pure organic system, especially in solution. Their dissatisfied fatigue resistance and stability greatly impede the application of spiropyran compound. Although the study of their metal complex has been started recently, it is not progressing smoothly because of the weak coordination and the difficulty in the crystal growth. Our present research focused on the novel smart crystalline material based on the technology of single-crystal to single-crystal transition and the early accumulation on the research of spiropyran ligands. We proposed a new strategy by using the multicarboxyl spiropyran ligands, in which carboxyl group bound directly to the stable indoline group, to connect metal ions forming tunable photoresponsive coordination polymers in self-assemble way. This thesis includes a review of the literature concerning spiropyran compounds and the following three investigations:The second part of the thesis describes the design and synthesis of a series of dicarboxyl-containing novel spiropyran derivatives, namely 1',3',3'-trimethylspiro[chromene-2,2'-indoline]-4',6'-dicarboxylic acid?DCSP?, 6-methyl-1',3',3'-trimethylspiro[chromene-2,2'-indoline]-4',6'-dicarboxylic acid?MDCSP?, and 6-nitro-1',3',3'- trimethylspiro[chromene-2,2'-indoline]-4',6'-dicarboxylic acid?NDCSP?, were designed and synthesized. All the compounds were fully characterized by 1H NMR spectroscopy, 13 C NMR spectroscopy, IR spectroscopy, and high resolution mass spectrometry. In addition, the photochromic properties of the compounds were investigated by UV absorpti on spectroscopy.The third part of the thesis presents the construction of multifunctional crystalline material. The aforementioned photochromic spiropyran ligands were used to coordinate with transition metal to construct photochromic coordination polymer s. We have successfully achieved the single crystal of the metal-organic coordination polymer [Zn?CSP??DMF??H₂O?₃]_n from the reaction product of the zinc salt and dicarboxylic spiropyran. X-ray structural analysis indicated that the two Zn?II? atoms in coordination polymer [Zn?CSP??DMF??H₂O?₃]_n are bridged into binuclear unit by four carboxyl groups, then the binuclear unit is further connected into two-dimensional layer by the double carboxyl bridge of the indoline aromatic ring. The axial ligand of DMF molecules are stretched to the holes?7 × 6 ?? in the layered structure. Finally, layered structure is further assembled into three-dimensional stacking by molecular interaction. It should be noted that this is the first report of photochromic spiropyran metal-organic coordination polymer.The fourth part of the thesis describes the investigation on the optical properties of spiropyran and its complex by UV absorption spectroscopy and fluorescence spectroscopy. Remarkable photochromism has been found in the coordination polymer [Zn?CSP??DMF??H₂O?₃]_n. Its behavior accounts for the reversible ring-opening/ring-closure process in response to light, solvent, p H, and temperature. Under UV excitation, the crystal of the coordination polymer emitted strong fluorescence. Morever, it shows well reversible negative photochromism and thermochromism not only in solution but also in crystalline state. And the process of color change can be recycled in the crystalline state with the stability and fatigue resistance.