Single-crystal To Single-crystal Transformations Of Coordination Compounds Constructed From Pyridine Derivative Ligands

Four coordination compounds, based on isonicotinic acid,pyridine-2,5-dicarboxylic acid and 4-tetrazole pyridine, have been successfully synthesized by using templates under hydrothermal or solvothermal conditions.Sing-crystal to single-crystal(SCSC) transformations were carried out by external stimuli. A series of coordination compounds were obtained, and the SCSC transformations mechanisms were discussed in detail. In addition, the structures,photoluminescence, variable-temperature magnetic susceptibilities, and adsorption property of compounds were also investigated.1. Compound 1 was prepared by a hydrothermal reaction with Cu(NO3)2·3H2O,iodine, and isonicotinic acid in H2 O. Compound 1 shows the exceedingly rare example of solid-state SCSC transformation from a 2D layer to a 3D framework via lattice iodine release, which involves the formation of a new Cu-O ligand bond and a change in the metal coordination geometry.2. Templated by iodine molecules, the first example of an I2-containing In III-compound, [In2(PYDC)3(H2O)]·0.5I2·0.5H2O(3), has been prepared. It shows a rare SCSC transformation upon removal the lattice iodine molecules. The selective adsorption property of compound 4 [In2(PYDC)3(H2O)]·0.5H2 O is studied.3. A highly stable soft porous coordination polymer, namely[Cu3(TP)4(N3)2(DMF)2]·2H2O·2DMF(5), has been synthesized via an in situ synthesis of 4-tetrazole pyridine(TP) under solvothermal condition(DMF =N,N’-dimethylformamide). Remarkably, the solvent molecules in(5) can be respectively exchanged with cyclohexane(C6H12), cyclopentane(C5H10),decahydronaphthalene(C10H18), 1,4-dioxane(C4H8O2) and tetrahydropyrane(C5H10O)in SCSC manners to yield [Cu3(TP)4(N3)2(DMF)2]·3C6H12(5a),[Cu3(TP)4(N3)2(DMF)2]·2C5H10(5b), [Cu3(TP)4(N3)2(DMF)2]·H2O·C10H18(5c),[Cu3(TP)4(N3)2(DMF)2]·C4H8O2(5d), [Cu3(TP)4(N3)2]·3C4H8O2(5e) and[Cu3(TP)4(N3)2]·2H2O·C5H10O(5f). Further, the occluded cyclohexane molecules in(5a) can be removed by heating to give its porous guest-free form[Cu3(TP)4(N3)2(DMF)2](5g). Particularly, in water,(5) can lose its coordinated N3-anions to generate [Cu(TP)2(H2O)4]·4H2O(5h). More interestingly, the soft PCP(5)demonstrates the selective adsorption for the cycloalkane solvents, namely cyclohexane, cyclopentane and decahydronaphthalene, in SCSC manners for the firsttime, attributing to the synergy effect between the size and geometry of the solvent and the shape of the framework cavity. Moreover, the desolvated samples of(5e)show the highly selective gas adsorption of CO2 over N2, indicating its potential application in the separation of CO2/N2 mixture.4. Two isomorphous 3D frameworks with rutile topology based on isonicotinate acid,[Mn(IN)2]·H2O(6) and [Mg(IN)2]·H2O(7), were prepared. Compound 6 shows excellent stablity in alcohols, while compound 7 reveals a rare SCSC transformation from a 3D structure to a mononuclear molecule of [Mg(IN)2(CH3OH)4](8) by soaking in methanol. In addition, the magnetic property of 6 and the photoluminescent property of 8 have been studied.