Anion-directed supramolecular assembly of cobalt(II)-fluconazole coordination polymers: Structural diversity, fluorescent and magnetic properties

Six fluconazole-bridged cobalt(II) coordination polymers, namely [Co(HFlu)2(H2O)2](ClO4)2 (1), [Co(HFlu)2(H2O)(AcO)](AcO)·2C2H5OH (2), [Co(HFlu)2Cl2]·2C2H5OH (3), [Co3(Flu)2(acac)4]·C2H5OH (4), [Co(HFlu)2(malo)(H2O)]·3H2O (5), and [Co(HFlu)2(fum)(H2O)2]·H2O (6) (HFlu = 2-(2′,4′-difluorophenyl)-1,3-bis(1,2,4-triazol-1-yl)-propan-2-ol, AcOH = acetate acid, Hacac = acetylacetonate, H2malo = malonate acid, H2fum = fumaric acid), have been synthesized and structurally characterized, and the thermal, fluorescent and magnetic properties investigated. The crystal structures display the one-dimensional cationic double-bridged chain consisting of 20-membered macrocycles to be parallel in 1 and perpendicular in 2. The structure of 3 consists of two-dimensional neutral rhombic grid in bc plane with (4,4) topology and alternative P/M helices intersecting at the Co sites along b direction. Complex 4 shows one-dimensional polymeric chain, in which binuclear Co2(Flu)2(acac)2 units act as bridging blocks to link Co(acac)2 nodes through triazolyl nitrogen atoms. The structure of 5 shows dimeric 20-membered macrometallacyclic motif. Complex 6 shows HFlu-bridged one-dimensional chain, which is stabilized by hydrogen-bonding interactions to produce alternative hydrophobic and hydrophilic architecture. Complexes 1–3 and 5–6 exhibit the similar electronic absorption and fluorescent spectra as those of HFlu, while complex 4 shows a fluorescent quenching phenomenon. Fluorescence titration of HFlu suggests that the fluorescent intensities at the maximal emission decrease upon the addition of Co(acac)2. The variable-temperature magnetic measurement of 4 reveals weak ferromagnetic interaction combined with the spin–orbit coupling effect in the 1-D Co(II) chain.

Six new cobalt(II) complexes with fluconazole have been prepared and fully characterized by physical methods. The coordination capabilities of anions to Co(II) ion have a great influence on the coordination mode of HFlu and molecular assembly to generate dimeric to two dimensional helical structure. The fluorescence, thermal stability and magnetic property have also been investigated.Figure optionsDownload as PowerPoint slide