Synthesis And Luminescent Properties Of Cyclic Trinuclear Unit-based Supramolecular Cages

The metal organic supramolecular cages are a class of metal-organic materials constructed from the self-assembly of metal ions and organic linkers with high symmetry and inner cavity.Since the guest molecuales can be accomandated within their cavities,these materials can act as host and exhibit rich host-guest chemistry.Recently,the synthetic approach of fluorescent supramolecular cages and strategies for controlling their fluorescent properties are well explored.However,phosphorescent supramolecular cages are rarely reported,and fine-tuning of their phosphorescent behavior has not been systematically studied.The cyclic trinuclear complex(CTC)is a nine-membered cyclic structure formed by linear two-coordination between coinage metal cations and carbon or nitrogen atoms.Many cyclic trinuclear complexes exhibit excellent photophysical properties such as strong phosphorescence emission and adjustable luminescence properties.The photoluminescence properties of metal organic supramolecular cages depend on the chemical composition and photophysical properties of metal ions,organic linkers and guests.Therefore,we envisioned that the introduction of CTC is promising for constructing phosphorescent supramolecular cages.This thesis invovles the synthesis,luminescence properties and fine-tuning of luminescence properties of CTC-based supramolecular cage,which mainly includes three parts.In the first part,we synthesized a series of inclusion complexes composed of a phosphorescence Cu₆L₃ trigonal prismatic cage host and halobenzene guests.Interestingly,the quantum yield(QY)and emission lifetime of inclusion complexes can be tuned by the change of halogen atoms of the guests due to the increment of SOC and ISC processes via external heavy-atom effects.For instance,by increasing the atomic nubmer of halogen from F to I,the QY enhanced six times(from 12.6 to 74.3%)while the lifetime reduced near two times(33.11 to18.39?s)at room temperture.The time-dependent density functional theory(TDDFT)calculations reveals that the encapsulation of iodobenzene guests can greatly promote the ISC processes,which are well agree with experimental results.In the second part of this thesis,we synthesized four CTCs using pyrazole-4-carbaldehyde containing derivatives as ligands,and investigated their crystal structures and luminescence properties.We found that these four complexes both are emissive in solution.In the solid state,Ag₃(L1)₃ and Au₃(L2)₃ exhibited fluorescent emission.In addition,we tried to synthesize octahedral cage complexes with these CTCs as building blocks.However,we found that they showed poor reactivity,and their Schiff-base products were unstable.Moreover,the imine bond-containing bispyrazole ligand was unstable and was easily broken,thus the synthese was not successful under the reaction conditions used in this article.In the third part,4-amino containing pyrazole ligand was use to synthesize a cyclic trinuclear gold(I)complex,Au₃(L3)₃.A tetrahedral cage might be synthesized by self-assembly of Au₃(L3)₃,zinc salt and 2-formylpyridine.In the mass spectrometry,the fragment ion peaks of the target product tetrahedral cage were observed,and the number of proton species and the ratio of the corresponding peak area in the proton spectrum of complex 8 were consistent with the theoretical ones.The luminescence behavior was also studied and was found that both complexes7 and 8 exhibited fluorescence emission behavior in the liquid state.