Novel Pb(II), Zn(II), and Cd(II) Coordination Polymers Constructed from Ferrocenyl-Substituted Carboxylate and Bipyridine-Based Ligands

Treatment of two kinds of ferrocenyl-substituted carboxylate ligands (3-ferrocenyl-2-crotonic acid, HOOCCH(CH3)CFc (Fc(η5-C5H5)Fe(η5-C5H4)) or O-ferrocecarbonyl benzoic acid, o-HOOCC6H4COFc with Pb(OAc)2·3H2O,
Zn(OAc)2·2H2O, or Cd(OAc)2·2H2O) resulted in four novel ferrocene-containing coordination polymers {[Pb(μ2-η2-OOCCH(CH3)CFc)2]·MeOH}n (1), {[Zn(o-OOCC6H4COFc)2(4,4‘-bipy)(H2O)2]·2MeOH·2H2O}n (4,4‘-bipy = 4,4‘-bipyridine) (2), {[Cd(o-OOCC6H4COFc)2(bpe)(MeOH)2]·2H2O}n (bpe = 1,2-bis(4-pyridyl)ethene) (3), and [Pb(o-OOCC6H4COFc)(η2-o-OOCC6H4COFc)(bpe)]n (4). Their crystal structures have been characterized by single X-ray
determinations. In polymer 1, Pb(II) ions are bridged by tridentate FcC(CH3)CHCOO- anions, forming an infinite
chain [Pb(μ2-η2-OOCCH(CH3)CFc)2]n. In polymers 2−4, there are three kinds of components, metal ions,
o-FcCOC6H4COO- units, and organic bridging ligands. The bipyridine-based ligands connect metal ions leading to
a one-dimensional chain with o-FcCOC6H4COO- units acting as monodentate or chelate ligands in the side chain.
Such coordination polymers containing ferrocenyl-substituted carboxylate and bipyridine-based ligands are very
rare. The solution-state differential pulse voltammetries of polymers 1−4 were determined. The results indicate that
the half-wave potential of the ferrocenyl moieties is influenced by the Pb(II) ions in polymer 1 and strongly influenced
by Zn(II), Cd(II), or Pb(II) ions in polymers 2−4. The thermal properties of the four polymers were also investigated.