The Lead Coordination Polymers Containing Pyrazine-2,3-Dicarboxylic Acid: Rapid Structural Transformations and Cation Exchange

A new Pb-based coordination polymer
synthesized with pyrazine-2,3-dicarboxylic
acid (H2pzdc) is reported along with its structural characterizations.
The compound, Pb2Cl2­(Hpzdc)2­(H2O)2 (1), is synthesized
using a simple, aqueous-based dissolution–slow evaporation
method with optimized conditions. It crystallizes in the C2/m space group (a = 11.561(1)
Å, b = 8.4327(7) Å, c =
11.792(1) Å, β = 126.3070(8)°), with a 1D coordination
polymer consisting of Pb2Cl2 dimers with monoprotonated
dicarboxylic acids located between the chains. Soaking 1 in an aqueous solution of Hg­(II) or Co­(II) at room temperature resulted
in a structural transformation into a newly formed 2D or 3D structure,
respectively. The 2D compound, Pb­(pzdc)­(H2O) (2), crystallizes in the Pbca space group
(a = 9.2624(9) Å, b = 12.0268(9)
Å, c = 13.9430(8) Å), whereas the rapidly
formed 3D compound, Pb2.67Co0.33­(pzdc)3­(H2O) (3), crystallizes in the P21/n space group (a = 10.9665(7) Å, b = 8.1909(4) Å, c = 25.0238(1) Å, β = 91.593(5)°). A structure
similar to 3 without any dopant, Pb3(pzdc)3­(H2O) (3a), is also synthesized.
A rapid, room-temperature cation exchange is also observed when soaking 1 into an aqueous solution of Cu­(II), giving a known structure.
Systematic studies on the syntheses and characterizations of 1 and its remarkably rapid structural transformations and
cation exchange at room temperature are presented.