Zinc dicarboxylate polymers and dimers: thiourea substitution as a tool in supramolecular synthesis

The reactions of the zinc thiourea complexes [Zn{SC(NHR)(NHR')}(4)] Cl-2(L=L-1, R=H, R'=Me; L=L-2, R=Me, R'=Me) with a range of dicarboxylates have been investigated. From these reactions eleven products-[Zn(L-1)(2)-(mu-terephthalate)](n), [Zn(L-1)(2)(mu-fumarate)](n), {[Zn(L-1)(2)(mu-isophthalate)].H2O}(n), [Zn(L-1)(2)(mu-1,3-phenylenediacetate)](n), [Zn(L-1)(2)(mu-phthalate)](2).4H(2)O, {[Zn(L-2)(2)(mu-terephthlate)].0.5H(2)O}(n), [Zn(L-2)(2)(mu-fumarate)](n), [Zn(L-2)(2)(mu-isophthalate)](2).2H(2)O, [Zn(L-2)(2)(mu-phthalate)](n), [Zn(L-2)(2)(mu-maleate)](2).2H(2)O and [Zn(L-2)(2)(mu-citraconate)](2).2H(2)O-have been crystallographically characterised. The structural characterisation of these compounds demonstrates that by increasing the number of methyl substituents on the thiourea ligand, the likelihood of forming a dimer as opposed to a coordination polymer also increases. Moreover, dimer formation is only favoured for non-linear dicarboxylates those in which the angle between the carboxylate groups is less than 180degrees.