Study On Synthesis,Structures And Coordination Properties Of Pincer Pyridine-Pyrrole Multidentate Compounds

Nitrogen heterocyclic compounds are closely related to people’s daily life.At the same time,they are also the triggers of research in many fields.The development of new nitrogen heterocyclic structures and the expansion of their properties have provided a continuous stream of research motivation for various scientific fields.In the past three decades,polypyridine-type clamp ligands（such as terpyridine and terpyridyl）easily form large conjugated systems and have strongσelectron-donating ability.The complexes formed with metal ions exhibit redox,photophysical and catalytic properties.The pyrrole ring is an electron-rich aromatic ring.The introduction of a pyridine ring can provide uniqueπ-donor properties and more spatial structure for the pincer structure.In order to expand this type of ligand,in recent years people have begun to synthesize pyridine and molecular via molecular design methods.The flexible electronic distribution states and unique spatial structures make these new types of clamp ligands and their metal complexes more attractive in areas such as light emission,fluorescence sensing,and energy catalysis stronger application value.Therefore,from the perspective of molecular design,this paper designs,synthesizes and characterizes four pinch-pyridine-pyrrole polydentate compounds,and further studies their coordination with protons and silver ions.Compared with the extensive research and development of polypyridine compounds,the research on pyridine-pyrrole compounds is very lacking.An important reason is the limitation of synthesis.However,with the development of modern organic synthesis methods,the problems of synthesis have been gradually solved.The development and research of shaped compounds is ready.In this thesis,based on the previous synthesis work,an innovation was designed.A simple and high-yield general synthetic scheme was designed to prepare tetraphenyl-pyridine-dipyrrole compounds（named PDP-1）and three new pyridine-pyrrole clamp compounds（Named as:PDP-2,PDP-3,DPP）.Through the single crystal structure characterization and basic spectral analysis,we found that the electronic distribution state and spatial structure of this type of compound can effectively coordinate with cations,mainly including H+coordination（that is:protonation）and transition metal coordination.The cationic coordination can show the application value of fluorescence sensing and the new multi-core silver coordination system that accommodates multi-core silver structure,expanding the application range.Based on protonation,pyridine-pyrrole compounds have acid-base recognition properties.In further application research,we have also found that the compound PDP-1 has a selective recognition effect on HCl.HCl can be detected and identified at room temperature.The limit is 0.6 equivalent or more,and the quantitative identification range is 0.6 to 4.0 equivalent.It is an effective optical detection method with good selectivity,reversibility and real-time performance.The single crystal structure further reveals the selective recognition mechanism of HCl.In the pincer structure of a single molecule of PDP-1,the space size can just accommodate a Cl^-in HCl,and the molecule exhibits better planarity,which promotes the intramolecular charge transfer（ICT）and chelation effect.It is worth mentioning that this is also the first time a pyridine-pyrrole clamp compound has been found to have the efficacy of a fluorescent probe.In addition,we constructed a new multi-core silver coordination system and prepared two new types of multi-core silver complexes:[Ag₃（DPP）₃]and[Ag₄（PDP-2）2].Among them,[Ag4（PDP-2）2]is the first obtained pyridyl-pyrrole polynuclear silver complex with five coordination sites,with a thermal stability temperature of350℃.Both complexes exhibited a ligand-to-metal-metal charge transfer（LMMCT）luminescence property and are new blue light-emitting materials.