The Study Of Design And Synthesis Of Cu(Ⅱ)-Coordination Polymers As Catalysts Towards 2-Imidazolines

2-Imidazolines,an important class of bioactive molecules,are widely used in the fields of biology,chemistry and pharmaceuticals.However,the procedures for the construction of 2-imidazolines generally suffer from low product yields,poor functional-group tolerance,or expensive catalysts.So it is a major challenge for the synthesis of 2-imidazolines to design and synthesize new,efficient and low-cost catalysts.In recent years,it has been found that some Cu（Ⅱ）-coordiantion polymers（CPs）can initiate some organic reactions because the existence of the catalytic active sites in the structures.But up to now,Cu（Ⅱ）-CPs have not been fully developed in the fields of catalysis due to the absence of effecitient catalytic sites in the structures.Fortunately,the successful applications of single-crystal to single-crystal（SCSC）transitions provide new opportunities for the research in designing and synthesizing catalysis.A series of ligands,2,2’-bipyridine-3,3’,6,6’-tetracarboxylic acid（H₄BPTC）,3,9-bis（pyridin-4-yl）-2,4,8,10-tetraoxaspiro[5.5]undecane（BPTU）,[6,6’-（（1E,1’E）-（ethane-1,2-diylbis（azanylylidene））bis（methanylylidene））bis（2-methoxyphenol）(H₂L^ED),6,6’-（（1E,1’E）-（isopropane-1,2-diylbis（azanylylidene））bis（methanylylidene））bis（2-methoxyphenol）(H₂L^DAP),6,6’-（（1E,1’E）-（（1R,2S）-cyclohexane-1,2-diylbis（azanylylidene））bis（methanylylidene））bis（2-methoxyphenol）(H₂L^DAC)],4-（2-methyl-1H-benzo[d]imidazol-1-yl）isophthalicacid（H₂BIMD）were used to afford eight Cu（Ⅱ）-CPs,and their catalytic activities have been measured in the synthesis of 2-imidazolies.Among them,seven Cu（Ⅱ）-CPs presented effecient catalytic property.In this paper,the following aspects have been primarily discussed:（1）Based on H₄BPTC or BPTU,four Cu（Ⅱ）-CPs{[Cu（BPTC）_0.5H₂O]·H₂O}_n(1^1D),[Cu（BPTC）_0.5]_n(2^3D),[Cu（BPTU）Cl₂]·CH₃CN(3^Cl)and[Cu（BPTU）I]·I·CH₃CN（4^I）have been obtained.1D 1^1D undergoes an irreversible thermally triggered SCSC transformation to produce 3D 2^3D;By the anion exchange-induced（Cl^-→I^-）,1D 3^Cl has transformed into 4^I.The catalytic results demonstrate,even though both 1^1D and 2^3D present high catalytic activity in the coupling and cyclization reaction of aryl nitriles with ethylenediamine（ED）,the activation temperature of 1^1D is higher than that of 2^3D,which can be ascribrd to the different Cu（Ⅱ）coordiantion environments.The reaction of aryl nitriles and 1,2-diaminocyclohexane（DAC）can be effeciently catalyzed by 3^Cl,while no reaction occurs when adding 4^I in such reaction.（2）Based on three salen ligands with different substituents,three Cu^ⅡNa^I-CPs,[Cu₄Na₂(L^ED)₂（N₃）₅（OAc）（H₂O）]_n(6^ED),[Cu₅Na₂(L^DAP)₂（N₃）₆（OAc）₂（OMe）₂（H₂O）₂]·H₂O(7^DAP)and Cu₅Na₂(L^DAC)₂（N₃）₆（OAc）₂（OMe）₂(8^DAC)have been synthesized.The catalytic results demonstrate that 6^ED-8^DAC show various catalytic performances in the raction of aryl nitriles and 1,2-diaminopropane（DAP）.It was found that the catalytic activities of CPs can be affected by the diverse electronic and steric factors of substitutes of salen,and 7^DAP with small sterical hindered electron-donating substituent on salen displays the highest activity.Moreover,the density functional theory（DFT）calculations have been used to determine the most stable structure of these 2-imidazolines products with two equivalent tautomers.（3）A 3D Cu-MOF[Cu₂（BIMD）₂（H₂O）]·11H₂O（9）with high stability and highly tunable pore sizes undergoes an reversible thermally triggered SCSC transformation to produce the anhyrous 9’.Such SCSC transition was accompanied by the generation of the unsaturated metal coordination sites（UMCs）.All UMCs face toward the open spaces of the channel,providing an opportunity to study the catalytic activity and the postsynthetic modification of9’.Catalytic result exhibits that,compared to 9,9’show better activity in the coupling and cyclization reaction of 4-pyridyl nitrile（PYN）and DAP.Besides,the uniform catalytic sites available in 9’provide the possibility to directly study reaction mechanisms in heterogeneous catalysts.Based on the obtained single crystals of THF@9’and PY@9’,the PXRD,IR,UV-vis,TG and NMR have been ultilized to explore the catalytic mechanism of the coupling and cycling reaction of aryl nitriles and DAP,which provides significant information and way on the study of the reaction mechanism by the means of MOF.