Synthesis,Crystal Structure And Properties Of Rare Earth Complexes Based On 4-halophenylpyrimidinone Methanesulfonic Acid

Rare earth complexes have a wide range of biological activities,such as antibacterial,antioxidant,anti-inflammatory,antitumor and analgesic activities,so the design and synthesis of new rare earth complexes has important application value and theoretical significance.Albumin exists in a variety of organisms and has a variety of physiological functions,such as transporting substances,maintaining blood osmotic pressure and acid-base balance in the body,etc.The study of its mechanism of action with rare earth complexes is conducive to the development of rare earth complexes with application value.In this paper,dihydropyrimidinone methanesulfonic acid was synthesized by sulfonation of dihydropyrimidinone.4-halophenylpyrimidinone methanesulfonic acid was selected as the ligand for coordination reaction with rare earth chloride to synthesize the rare earth complex of pyrimidinone mesylate,and the mechanism of its interaction with Bovine Serum Albumin（BSA）was studied under simulated physiological conditions.The main contents of this paper are as follows:1.Eleven pyrimidinone methanesulfonic acid compounds were synthesized by sulfonation on the methyl group of pyrimidinone C-6,and their structures were characterized by Nuclear Magnetic Resonance(¹HNMR,¹³CNMR),Mass Spectrometry（MS）,and Fourier Transform Infrared Spectroscopy（FTIR）.2.With the ligand of[6-（4-fluorophenyl）-5-（ethoxycarbonyl）-2-oxo-1,2,3,6-tetrahydro-pyrimidin-4-yl]methanesulfonic acid（HL₁）,[6-（4-chlorophenyl）-5-（ethoxycarbonyl）-2-oxo-1,2,3,6-tetrahydropyrimidin-4-yl]methanesulfonic acid（HL₂）,[6-（4-bromophenyl）-5-（ethoxycarbonyl）-2-oxo-1,2,3,6-tetrahydropyrimidin-4-yl]methanesulfonic acid（HL₃）carried to have coordination reactionwith rare earth（La,Ce,Pr,Nd,Er）chloride,six rare earth complexes（La 1,Ce 2,Pr 3,Nd 4,Er 5,Er 6）were synthesized.The single crystal of six complexes was cultured with solution evaporation method.The structures and properties of the complexes were characterized by X-ray Diffraction,X-ray Polycrystal Diffraction（XRD）,Thermogravimetric Analyzer（TGA）,and Fourier Transform Infrared Spectroscopy（FTIR）.Results of crystal structure analysis were as follows:Firsly,the crystals of the four rare earth complexes[La（L₂）₂（H₂O）₆]（L₂）（C₂H₅OH）₂·3H₂O,[Ln（L₃）₂（H₂O）₆]（L₃）（C₂H₅OH）₂·3H₂O（Ln=Ce,Pr,Nd）are isomorphic and monoclinic,the space group is P2（1）/n,and the central ion Ln³⁺coordination number is nine.Secondly,the complex[Er（L₁）（H₂O）₇]·[Er（H₂O）₈]·（L₁）₅·7H₂O belongs to the triclinic system,and its space group is P-1,and the central ion Er³⁺coordination number is eight.Thirdly,the complex[Er（L₂）（H₂O）₈]·（L₂）₃·4H₂O is a tetragonal crystal system,and its space group is I4（1）/a.Thermogravimetric Analysis results show that complex water in complexes is also easier to lose.3.The conformational changes of BSA after the addition of rare earth complex（taking complex Er 5as an example）were studied by UV-vis Absorption Spectroscopy and Synchronous Fluorescence Spectrometry.The results showed that the complex Er 5 changed the microenvironment of amino acid residues in BSA.By measuring the quenching rate constants[11.47 x 10¹² L/（mol·s）（300 K）and14.79 x 10¹² L/（mol·s）（310 K）]in the process of fluorescence quenching caused by the binding of complex Er 5 to BSA at different temperatures,it is showed that the mechanism of fluorescence quenching caused by the binding of complex Er 5 and BSA is the dynamic quenching accompanied by static quenching.In addition,according to Forster’s theory,the binding distance r（r=3.01 nm）between BSA and the complex Er 5 was calculated,indicating that non-radiative energy transfer occurred between BSA and complex Er 5.The emission fluorescence spectra of six rare earth complexes（La 1,Ce 2,Pr 3,Nd 4,Er 5,Er 6）interacting with BSA were studied at temperatures of 300 K and 310 K.The research showed that:Firstly,the interaction between the six rare earth complexes and BSA are spontaneous processes,and the combination of complexes La 1,Nd 4,Er 5 and BSA is mainly hydrophobic.Secondly,the binding of complexes Ce 2 and Pr 3 to BSA is dominated by hydrogen bond or van der Waals force.Thirdly,the combination of complex Er 6 and BSA is dominated by hydrogen bond and hydrophobic force.