Structures And Properties Researches Of Homochiral Coordination Polymers Based On Different Pyridyl Alanine Derivative Ligands

As a novel type of chiral crystalline materials,chiral coordination frameworks have attracted significant attention recently in separation of enantiomers,enantioselective catalysis,magnetism and so on.Natural amino acids,as the inexpensive and readily available chiral sources,have been widely accepted to synthesize chiral MOFs materials.Currently,for the construction of chiral coordination frameworks,the semi-rigid amino acid derivatives were often used as chiral ligands.Beyond that,the semi-rigid and flexible polycarboxylic acid substituent groups have been exploited for the fabrication of chiral coordination frameworks with fascinating structures and interesting properties.Compared with the polycarboxylic acid,pyridine-based carboxylic acid,as substitutional group,modifies the amino group of amino acid to produce the amino acid derivative with semi-rigid and asymmetric configuration,which has been rarely reported.In this paper,we integrated L-alanine into different pyridine carboxylic acid groups via the amide condensation reaction,and then obtained three chiral ligands with different flexibility sturctures.Seven kinds of novel chiral coordination polymers with different dimensions have been synthesized by self-assembly reactions of different chiral ligands using linear pyridine auxiliary ligands and metal ions under suitable conditions.This paper mainly includes three section works:1.Chiral complexes constructed by the asymmetric structure of pyridyl disubstituted chiral alanine ligands and pyridine bridging ligands:In this part,we select the pyridine disubstituted chiral ligand,2,5-pyridine amide-di?L-alanine??H₂?2,5-PycdiAla??with asymmetric structure,and the transition metal Cd?II?,Cu?II?in the presence or absence of 4,4-bipy.According to the process of coordination self-assembly,two chiral coordination polymers{[Cd?2,5-PycdiAla??H₂O?₃]·2H₂O}_n?1?,{[Cu₃?2,5-PycdiAla?₂?4,4-bipy?₂?H₂O?₂]·10H₂O}_n?2?have prepared successfully.It can be seen from single crystal X-ray diffraction that the complex 1 is an orthorhombic system,the P2₁2₁2₁ chiral space group.Its structure is a simple one-dimensional helical chain structure formed by chiral ligands and Cd?II?.The complex 2 is a monoclinic crystal,the P2₁ chiral space group.The chiral ligands and ancillary ligands form a kind of left-handed helical chain,and the auxiliary ligands connect the helical chains to each other to support a two-dimensional layered structure.In this chapter,the fluorescence test and photocatalytic degradation dyes of the complex1 were carried out.The results show that the complex 1 has a strong fluorescence emission spectrum at 433 nm,and the complex 1 has a good photocatalytic degradation effect on MO and MB under ultraviolet light.2.Chiral complexes constructed by symmetric structure of pyridyl disubstituted chiral alanine ligands and pyridine bridging ligands:In this chapter,the pyridyl disubstituted chiral ligand 3,5-picolinamide-di?L-alanine??H₂?3,5-PycdiAla??with a symmetric structure and linear auxiliary ligands bpee and bpea were introduced,According to the process of coordination self-assembly,two chiral coordination polymers[Co?3,5-PycdiAla??bpea??H₂O?]_n?3?,{[M?3,5-PycdiAla??bpee??H₂O?₂]·5H₂O}_n?M=Ni,4;Co,5?have prepared successfully.According to the single crystal X-ray diffraction analysis,the complex 3 is monoclinic,P2₁ chiral space group,the chiral ligand directly forms a right-handed helical chain with Co?II?ions,and the auxiliary ligand bpea connects the helical chains to each other.A two-dimensional tile-shaped layered structure was constructed.Complexes 4-5 are isomorphic complexes of different metal centers,and the metal acts as a four-joining point to form a two-dimensional layer structure having a V-shaped window by alternately joining two chiral ligands and two ancillary ligands bpee.Due to the presence of the Co-O-Co chains in the complex 3,we performed a magnetic test on the complex 3,and the results showed that there was a strong antiferromagnetic effect between the Co?II?ions.3.Chiral complexs constructed by an asymmetric structure of a pyridyl monosubstituted chiral alanine ligand:Two novel chiral coordination frameworks,namely{[Cd?PycAla?₂?H₂O?]·4H₂O}_n?6?and[Co?PycAla?₂?H₂O?₂]_n?7?,have been successfully prepared via the chiral pyridine-4-carbonyl-?L-alanine??HPycAla?ligand reacting with Cd?II?and Co?II?ions under hydrothermal conditions.Complex 6 is a trigonal system,P3₂21 chiral space group,chiral ligands are freely twisted in space,forming a left-handed single-helix and a right-handed double-helical spiral chain,and the spiral chains share Cd?II?The ions are connected to each other to form a three-dimensional network of quartz topology with a topological symbol of?6⁴,8²?and a porosity of 22.4%.Complex 7 is a monoclinic system,P2₁ chiral space group.Due to the asymmetry of the chiral ligand,two right-handed spiral chains of spin anti-parallel are formed,and the two are alternately arranged to form a two-dimensional diamond network structure.The topology symbol is?4⁴,6²?.In this chapter,the photocatalytic degradation dyes of complex 6-7 were tested.The results show that compared with MO,both of them show very good photodegradation effect on MB,and the degradation efficiency reaches over98%.In addition,complex 6 exhibited good photoluminescence properties,and further subjected to metal cation fluorescence response experiments,the results showed that complex 6 can be used as a fluorescent probe to effectively detect Fe³⁺ions.