para-Benzene disulfonic acid and its tetrachloro and tetrafluoro derivatives--studies towards polyhalogenated metal-organic-frameworks with sulfo analogues of terephthalic acid.

We developed convenient synthetic routes for the preparation of para-benzene disulfonic acid (H(2)BDS) and its tetrachloro (H(2)BDSCl(4)) and tetrafluoro (H(2)BDSF(4)) derivatives. The reaction of these acids with zinc nitrate in DMF led to single crystals of [Zn(BDS)(DMF)(2)] (triclinic, P ̄1[combining macron], Z=2, a=976.62(4), b=986.85(4), c=1014.40(4), α=69.106(2)°, β=68.746(2)°, γ=86.295(2)°, wR(2)=0.0627), [Zn(BDSCl(4))(DMF)(4)] (triclinic, P ̄1[combining macron], Z=1, a=831.5(1), b=905.2(1), c=989.6(1), α=90.44(2)°, β=91.41 (2)°, γ=106.72(2)°, wR(2)=0.0635), and [Zn(BDSF(4))(DMF)(4)] (monoclinic, P2(1)/c, Z=2, a=889.01(3), b=968.91(3), c=1633.07(5) pm, β=106.524(2)°, wR(2)=0.0948). While [Zn(BDS)(DMF)(2)] exhibits a layer structure, the disulfonate linkers connect the zinc ions into chains in the crystal structures of [Zn(BDSCl(4))(DMF)(4)] and [Zn(BDSF(4))(DMF)(4)]. Thermoanalytical investigations revealed that desolvation of the compounds occurs in a temperature range between 100 and 200 °C. The solvent free sulfonates show remarkably high stabilities, [Zn(BDS)(DMF)(2)] is stable up to nearly 600 °C. The halogenated acids were also used to prepare copper salts from aqueous solutions and Cu(2)(OH)(2)(CO(3)) (malachite) as a copper source. The crystal structure of [Cu(H(2)O)(6)](BDSF(4)) (triclinic, P ̄1[combining macron], Z=1, a=510.45(2), b=744.68(3), c=1077.77(4) pm, α=85.627 (2)°, β=77.449 (2)°, γ=76.015 (2)°) exhibits complex cations and uncoordinated sulfonate anions, while in [Cu(BDSCl(4))(H(2)O)(4)] (orthorhombic, Pnma, Z=4, a=721.27(2), b=2147.81(6), c=979.42(3) pm) the Cu(2+) ions are linked to infinite chains in the crystal structure. The most interesting structural feature of [Cu(BDSCl(4))(H(2)O)(4)] is the significant deviation from planarity of the disulfonate dianion. Theoretical investigations revealed that a boat conformation is favoured due to steric hindrance in cases where a syn coordination of the sulfonate groups occurs. The thermal behaviour of the copper compounds was also investigated by DTA/TG measurements and X-ray powder diffraction. © The Royal Society of Chemistry 2011