Influence of ionic liquids on the syntheses and structures of Mn(II) coordination polymers based on multidentate N-heterocyclic aromatic ligands and bridging carboxylate ligands

摘要

Seven Mn(II) coordination polymers, namely {[Mn-2(ptptp)Cl-2(H2O)(3)]center dot H2O}(n) (1), {[Mn(mu-ptptp)(3)](2)[Mn-3-(mu(3)-Cl)](2)}center dot 2Cl center dot 16H(2)O (2), {[Mn-2(ptptp)(ip)(2)(H2O)(3)]center dot H2O}(n) (3), {[Mn-2(ptptp)(5-CH3-ip)(2)(H2O)(3)]center dot H2O}(n) (4), {[Mn-4(ptptp)(5-Br-ip)(3)(H2O)(3)]center dot 4H(2)O}(n) (5), {[Mn-2(ptptp)(Hbtc)(H2O)(2)]center dot 2H(2)O}(n) (6) and {[Mn-2(ptptp)(tdc)(H2O)(2)]center dot 1.5H(2)O}(n) (7), have been prepared based on multidentate N-heterocyclic aromatic ligands and bridging carboxylate ligands (H(2)ptptp = 2-(5-{6-[5-(pyrazin-2-yl)-1H-1,2,4-triazol-3-yl] pyridin-2-yl}-1H-1,2,4- triazol-3-yl) pyrazine; R-isophthalic acids, H(2)ip-R: R = -H (3), -CH3 (4), -Br (5); H(3)btc = trimesic acid (6); H(2)tdc = thiophene-2,5-dicarboxylic acid (7)), in order to further probe the multiple roles of [RMI]Br ionic liquids in the hydro/solvothermal synthesis (RMI = 1-alkyl-3-methylimidazolium, R = ethyl, or propyl, or butyl). The successful syntheses of complexes 2-6 suggest that in hydro/solvothermal synthesis the addition of a small amount of [RMI]Br plays a crucial role. Complex 1 exhibits single right-handed helices constructed by ptptp ligands and Mn(II) ions. Complex 2 possesses octanuclear helicate structures in which two propeller-shaped [Mn(mu-ptptp)(3)](4-) units embrace two [Mn-3(mu 3-Cl)](5+) cluster cores inside. Complexes 3 and 4 are isostructural and display a 1D double chain formed by two kinds of pseudo mesohelices: (Mn-ptptp)(n) and (Mn-5-R-ip)(n). Complex 5 has a 2D structure containing 1D Mn(II) ion chains formed through carboxylates and [ptptp](2-)-N,N bridges. Complex 6 shows a 2D structure formed by a meso-helix (Mn-ptptp) n and the partly deprotonated Hbtc ligands. Complex 7 features a heterochiral [2 + 2] coaxially nested double-helical column formed by using the outer double-helices (Mn-ptptp) n as a template to encapsulate the inner double-helices (Mn-tdc) n with opposite orientation. All complexes were characterized by elemental analysis, IR spectroscopy, thermogravimetric analysis, single-crystal X-ray crystallography and powder X-ray diffraction. The magnetic properties of 1-7 were also investigated.