Formation of Zn(II) and Pb(II) coordination polymers of tetrakis(4-pyridyl)cyclobutane controlled by benzene and toluene

Reactions of Zn(NO3)(2)center dot 6H(2)O with tetrakis(4-pyridyl) cyclobutane (tpcb) in MeOH followed by addition of benzene or toluene gave rise to two two-dimensional (2D) coordination polymers {[Zn(tpcb)center dot NO3)(2)]center dot 2S}(n) (1: S = benzene; 2: S = toluene). The analogue reactions of Pb(NO3)(2) with tpcb in similar solvent systems resulted in the formation of {[Pb(tpcb)(0.5)(NO3)(2()MeOH)]center dot benzene}(n) (3) and [Pb(tpcb)(NO3)(2)(MeOH)](n) (4), respectively. Slow evaporation of the MeOH solution containing Pb.NO3) 2 and tpcb generated [Pb(tpcb)(NO3)2 center dot H2O)](n) (5). Compounds 1 and 2 show similar 2D networks but differ in their packing modes, namely "overlapping" and "crisscross" modes. Compound 3 exhibits a 3D porous framework in which its 1D channels are occupied by benzene molecules. Compound 4 consists of 1D [Pb(tpcb)(NO3)(2)(MeOH)] n chains which are linked by weak Pb. N secondary interactions to form a 2D gridlike network. Compound 5 has a 3D structure constructed by dinuclear [Pb-2(tpcb)(6)(NO3)(4()H2O)(2)] units and tpcb bridges with a Schlafli symbol of (4 center dot 6(2))center dot(4(2)center dot 6(10)center dot 8(2)). The solvent effects may be ascribed to the formation of the five 2D and 3D coordination polymers 1-5. The inclusion of benzene and toluene molecules in the frameworks of 1 and 2 along with the time lengths of their crystal growth may provide an interesting approach to the selective separation of benzene and toluene.