Construction And Sensing Properties Of Complexes Derived From L-Amino Acid

In recent years,coordination complexes possess the characteristics of organic ligands and inorganic metals,and have become a hot research topic due to their excellent physical and chemical properties.Among them,complexes derived from amino acid usually have abundant hydrogen bond interactions,which not only provide design ideas of synthesizing supramolecular compounds,but also act as the structural basis for designing fluorescent sensors with high sensitivity.In this dissertation,amino acid derivatives are selected as ligands to react with transition metal and rare earth metal ions,respectively.Complexes with fluorescence sensing properties are synthesized under solvothermal condition,and their sensing mechanisms are explored in detail.Fluorescence sensors constructed from amino acid derivatives show high selectivity,visualization,rapidity towards heavy metals cations and residues of the organic molecules in aqueous system,which provide experimental and theoretical basis for protecting ecosystem balance and human health.All researches include:1.Seventeen novel complexes were synthesized based on1,4-bis（（L-serine）methyl）benzene（H₂bsmb）,（4-（1H-imidazol-1-yl）benzyl）-L-glutamic acid（H₂ibga）,N-（4-carboxylbenzyl）-L-aspartic acid（H₃caa）and different metal ions[Co（Ⅱ）,Ni（Ⅱ）,Cu（Ⅱ）,Zn（Ⅱ）,Cd（Ⅱ）and Ln（Ⅲ）]under solvothermal condition with different molar ratios,solvents and p H.Complexes 1-4 inherit the chirality from ligand H₂bsmb by single-crystal structure and CD spectra analysis,indicating enantiomeric purity complexes can be synthesized easily by H₂bsmb.The ligand H₂ibga cyclized in complex 5can be found by comparing with the structure and CD spectra of ligand and complex 5,which provides a design idea of complexes containing active cyclic peptide structure.Ligand H₃caa has seven different coordination modes in complexes 7-12（complexes12-17 were isomorphic）,implying complexes based on H₃caa have various structures.In addition,the weak interactions（hydrogen bonds andπ···π）in complexes 1-17 were analysized from values and graphics from crystal information and Hirshfeld surface,which provide experimental clues for synthesizing supramolecular complexes.2.Three complexes（4,10 and 11）were synthesized by H₂bsmb,H₃caa and metal ions with d¹⁰ electronic configuration and selected by fluorescence experiment.These complexes have good stabilities in water and acid and alkali resistance,in which complex11 might act as a thermal sensor in aqueous.Complexes 4 and 11 can specifically recognize Tb（Ⅲ）ions in aqueous system with low detection limits（LODs）of 11.4 n M and16.9 n M,respectively.Complex 10 can specifically detect tetracycline（TC）with LOD of5.53 n M.It provides a quantitative and visual method for detecting Tb（Ⅲ）ions and TC by analyzed color change of complexes and their strips before and after adding analytes.The sensing mechanisms of complex 4 and 11 are the energy transferred from complexes 4 and11 to Tb（Ⅲ）ions,respectively.There are resonance energy transfer and photo-induced electron transfer（PET）during the process of complex 10 in sensing TC,resulting in the characteristic peak of TC appeared at 530 nm and the peak of complex 10 at 420 nm decreased.3.We screened out three multifunctional fluorescent materials.For example,complex2 realizes bidirectional detection of Ce（Ⅲ）and Cu（Ⅱ）ions,complex 5 shows the multi-response detection behavior towards TC,Fe（Ⅲ）and AA,and complex 17 could sense Cr₂O₇^2-,Cr O₄^2-,TC and CTC by fluorescence and visual methods respectively.Among of them,complex 2 selectively senses Ce（Ⅲ）and Cu（Ⅱ）ions with LODs of0.388 n M and 8.134μM,respectively.The sensing mechanisms of complex 2 are the weak interactions exist between uncoordinated carboxylic group of complex 2 and Ce（Ⅲ）&Cu（Ⅱ）ions in solution,which promotes electrons transfer from complex 2 to Ce（Ⅲ）ions.And there is charge transfer or energy transfer between partially filled d orbital of Cu（Ⅱ）and complex 2.Complex 5 can sense TC,Fe（Ⅲ）and AA with LODs of 4.42 n M,3.49 n M and 0.38μM,respectively.There are competitive absorptions of excited state energy and resonance energy transfer in the process of complex 5 detection these three analytes.Besides,Fe（Ⅲ）ions may be adsorbed when it quenched the fluorescence intensity of 5.Complex 17 displays excellent sensing ability to Cr₂O₇^2-,Cr O₄^2-,TC and CTC with LODs of 3.66 n M,5.45 n M,0.25μM and 0.38μM,respectively.The competitive absorption of excited state energy and resonance energy transfer exists during the process of complex 17 sensing,and electrostatic interaction between Tb（Ⅲ）ions of complex 17and Cr（Ⅵ）may also contribute to the quenching effect.