Synthesis And Properties Of Benzimidazole Derivatives And Europium Complexes

Benzimidazole is a kind of heterocyclic compounds containing two nitrogen atoms,witha non-centrosymmetric structure. The introduction of different functional and structuralsubstituent on the imidazole ring forming the structure and function of differentbenzimidazole derivatives. Benzimidazole derivatives with a wide range of biological activityand more, good optical performance and coordination capabilities. Widely used in variousfields of chemistry,chemical engineering, aerospace, optoelectronic materials, life sciences,medicine. Europium as a rare earth element, with the advantages of inexpensive, readilyavailable.The benzimidazole and Europium coordination complexes, which can be applied tothe optoelectronic materials, biological simulation and other fields, was favored byresearchers.This paper mainly researched about Five kinds of2-substituted benzimidazolederivatives were synthesized successfully with1,2-diaminobenzene and aromatic aldehydes（or carboxylic acid） as raw materials in methanol. Five kinds of benzimidazole derivativeswere2-Phenylbenzimidazole（PBIM）,2-methyl benzimidazole （MBIM）,2-（4-methylphenyl）-benzimidazole（MPBIM）,2-（4-bromophenyl）-benzimidazole（BPBIM）,2,2’-bis-benzimidazoles（TBIM）. The products were characterized with FTIR,1H-NMR and elemental analysis. Onthis basis, the synthetic process of PBIM were optimized. After optimization, the best reactionconditions,, were as following: reaction temperature was45℃; the molar ratio of1,2-diaminobenzene to benzaldehyde,1:2; the reaction time,3h; the liquid solid ratio ofmethanol to1,2-diaminobenzene（mL/g）,37.0. And the highest yield of PBIM reaches 71.2%．Under optimal conditions, the yield of MPBIM, BPBIM reaches63%,67%. The yieldof MBIM,TBIM reaches79%,74%.With homemade four benzimidazole derivatives （PBIM, MBIM, MPBIM, BPBIM） asPrimary ligand,and Phen as auxiliary ligand, coordination with Europium complexesprepared by four benzimidazole-Eu complexes, followed respectively [Eu （Ⅲ）（Phen）（PBIM）] Cl₃·2H₂O （Complex1）,[Eu （Ⅲ）（Phen）（MBIM）] Cl₃·2H₂O （Complex2）,[Eu （Ⅲ）（Phen）（MPBIM）] Cl₃·2H₂O （Complex3）,[Eu （Ⅲ）（Phen）（BPBIM）] Cl₃·2H₂O （Complex4）.The products were characterized with FTIR,UV,TG, and elemental analysis. By conductivitymeasurement shows: Complexes1⁴were outside1:3type chloride. Cyclic voltammetryshowed that in HAc-NaAc buffer solution （pH≈6） for the base solution of the system,（vs.SCE） within the potential range of-1.0⁰.2V. Complexes1⁴exhibited electroehemicalactivity. Complexes1⁴reduction peak is proportionate to concentration,it showed that theeleetroehemical active center of Complexes1⁴is Eu+3. Complexes1⁴reduction peak wasproportionate to concentration,it showed that the eleetroehemical active center of Complexes1⁴was Eu+3. Moreover, Complexes1⁴peak potential with increasing scanning speedincreases, the oxidation peak postive shift and reduction peak negative shift, reduction peakcurrent Ipc and oxidation peak current Ipa ratio closer to1, indicating that oxidation of theComplexes1⁴with the increase scanning speed reduction system transform thequasi-reversible to reversible, and finally achieve stability. It also shows that when thebenzimidazole ligand more electron donating groups, electron-donating ability of thesubstituents the more the strong, a more number for△E p, conversely, the smaller the value of△Ep. It shows that benzimidazole ligand substituent electronic effects have a significantimpact on the redox properties of Eu. By adjusting the base replaced by electronic effects canbe achieved benzimidazole-Eu complex oxidation-reduction performance regulation,provide a suitable environment for the simulation of chemical redox ability of differentorganisms Eu.With homemade TBIM derivatives as Primary ligand,and DBM,o-phth as auxiliaryligand, coordination with Europium complexes prepared by two benzimidazole-Eu complexes, followed respectively Eu （Ⅲ）（DBM）₃TBIM, Eu （Ⅲ）（o-phth）₃TBIM. Theproducts were characterized with FTIR,UV,TG, and elemental analysis. In the process ofpreparation of ternary complexes, the type of base complexes have great influence onfluorescence properties of alkali NaOH conducive to coordinated reaction, with thefluorescence properties of complexes was best. Fluorescent complexes performance testsshowed that: compared with the binary complexes which was prepared with single auxiliaryligand,the fluorescence intensity of ternary complexes prepared by adding TBIM enhanced2.7³.1times. At room temperature, solid and DMF solution ternary complexes were emittedred fluorescence under ultraviolet light in the darkroom, is expected to be applied in the fieldof red fluorescent materials.