Syntheses And Photochronic Properties Of Viologen-templated Metal-Organic Complexes

Photochromic materials are widely involved in optical switches,second-order nonlinear optical materials,bioluminescent probes,optical information storage and anti-counterfeit marks.Metal-organic Frameworks(MOFs)materials are a kind of inorganic-organic hybrid materials which provide a good platform for photochromic design because of their porosity and dynamic properties.However,the photochromic inorganic-organic hybrid materials studied currently lack regulation of the discoloration properties and are less able to achieve the rapid reversible changes in the air.In this thesis,different viologen ions were introduced into the metal-organic framework to construct three series of photochromic MOFs by controlling the host-guest interaction between the framework and viologens.Firstly,three X-ray-induced host-guest photochromic MOFs were synthesized by solvothermal method using different viologen as template.Compound 1 and 2 were discolored by X-rays for 20-30 minutes,while compound 3(containing benzyl viologen)showed rapid response to both soft and hard X-rays at room temperature(about 2 min).The photoresponsive rate of 1,2 and 3 were 1.01 × 10-3 s-1,2.73 × 10-3 s-1 and 2.82 × 10-3 s-1,but three discolored compounds can quickly achieve reversible color change in the air condition(about 5 min).Then,three photochromic MOFs with fast reversible color changes in air were synthesized(compound 4,5 and 6)by incorporating the different guest molecules of viologens to the anionic metal organic frameworks.Among them,compound 6 with benzyl viologen as guest also responded to soft X-ray(Cu-K?,1.5418 A),at the same time,the photoresponsive rate of 6(k=4.44×10-3 s-1)is the largest among the three conpounds.Finally,we synthesized a host-guest photochromic metal-organic polyhedron by using benzyl viologen as template and analysised its crystal structure in detail(compound 7,k=2.9 ×10-3 s-1),it shows a rapid response to both soft and hard X-rays(Mo-Ka,0.71073 A)at room temperature and the discolored crystals can revert back to their original state within 2 minutes in the air,these properties make compound 7 an excellent material for X-ray detection.In summary,it is a feasible solution to regulate the interactions between different hosts and guests by introducing different viologen cations and changing different anion frameworks to adjust the photochromic behaviors.