Construction And Property Study Of Supramolecular Coordination Polymers Based On Argentophilic Interaction

Since 1980s,scholars have studied gold chemistry extensively and deeply,promoting the development of metallophilic interactions.Two closed-shell metal cations(such as Au+,Ag+ and Cu+)tend to have attractive interactions rather than repulsion when their distance are smaller than the sum of the van der Waals radii,as is the so-called metallophilic interaction(metal…metal interaction).During the research of related metal complexes,it has been found that luminescence,assigned to ligand-to-metal charge transfer transition modified by the metallophilic interaction(LMMCT),is usually induced,which makes it possible that the complexes can be developed into materials that are with unique photophysical properties.In recent years,metallophilic interaction,which has been widely used in the field of supramolecular chemistry as a non-covalent interaction,is employed to construct functional systems.Jiang's group has built up Ag(I)-SR coordination polymers as platforms for molecular sensing systems and supramolecular hydrogels facilitated by argentophilic interactions,based on in situ reaction of thiol-based ligands and Ag(I).Further investigations are carried out on the basis of previous work.By designing a series of thiol ligands,the application of Ag(I)-SR coordination polymers is extended for molecular/ion sensing,dual-chirality transfer,chiral supramolecular gels and an novel strategy for Forster resonance energy transfer(FRET).This dissertation consists of five chapters.Chapter 1 is the introduction for the metal…metal interaction in general.We review and discuss the categories of argentophilic interactions,and experimental evidence for it,including Ag-Ag distance and spectra criterion.Finally,the application of metallophilic interaction in chemosensors for molecule and/or ion sensing,supramolecular self-assembly and luminescent materials are shown in brief.In the second chapter,an achiral coordination polymer Ag(I)-MPBA(MPBA =p-mercaptophenylboronic acid)is developed to probe the chirality of saccharides.To achieve the target of binding and identifying saccharides,MPBA is chosen as the achiral thiol ligand,bearing a boronic acid group which can reversibly interact with saccharides in cyclic boronate ester mode.Thiol ligand usually has strong tendency to coordinate with Ag(I).Achiral polymer is formed in situ with repeating Ag(I)-MPBA units and silver chain skeleton facilitated by Ag(I)…Ag(I)interaction.CD spectra of varying profiles were observed with the tested saccharides such as glucose and fructose,confirming that the chirality of the saccharide is transferred to the Ag(I)…Ag(I)chromophore in the supramolecular sensory ensembles,which are induced to be chiral subsequently,upon interacting with the boronic acid group to form the cyclic boronate ester.Glucose that interacts with the supramolecular sensor in a 1:2 stoichiometry results in stronger CD signals whereas the monovalent fructose induced practically no or very weak CD signals,that could be acquired to correlate to the saccharide identity.As is shown in Chapter 3,a second chiral pool,phenylalanine,is introduced to Ag(I)-Cys framework to explore dual-chirality transfer and the spectra of resulting ensembles.The only structural difference is the variation in the configuration of the phe residue between homochiral dipeptide LLFC and heterochiral DLFC,but chemical environment of cysteine moiety changes a lot,making it could be observed through NMR spectra.The obvious spectroscopy differences between homo-and hetero-Ag(I)-FC could therefore make sense.Furthermore upon extension of the study to different amino acids,the strategy could be further developed for amino acids sensing.Chapter 4 represents Boc-protected dipeptides(BFC)by replacing acetyl-protected groups of FC presented in chapter three,enhancing its hydrophobic interaction.Upon coordination with Ag(I),ethanol solvent could be immobilized instantly by chain-like Ag(I)-BFC polymers facilitated by Ag(I)…Ag(I)interaction cooperated with other weak interactions,namely hydrogen-bond,hydrophobic interaction,and ?-? stacking.The highly thermodynamic-stable gels exhibit different colors between Ag(I)-LLBFC and Ag(I)-DLBFC arising from the difference in Ag-Ag distance.The addition of halide ions makes changes to heterochiral gel color,leaving homochiral gel color invariant.Owing to the well-organized construction of Ag(?)-LLBFC assemblies,the self-healing ability of homochiral gel tends to be weaker after being treated with I-and Ag+ in sequence.A brand-new pattern for Forster resonance energy transfer(FRET)is demonstrated in the last chapter.It is widely believed that the well spectral overlap of the emission and absorption spectra of the donor and acceptor,distance short enough between the donor and corresponding acceptor,and appropriate dipole moment orientation are three primary factors essential for fabricating an efficient FRET process.In view of the above conditions,we synthesized several thiol derivatives decorated by fluorophores,acting as energy donor and acceptor respectively,and the separated compounds are gathered through argentophilic interaction displaying FRET process upon the coordination with Ag(?).