Faculty Advisor

John C. MacDonald


The supramolecular chemistry and crystal structures of four Bis(imidazolium 2,4,6-pyridinetricarboxylate) metal(II)dihydrate complexes, where M=Co2+, Ni2+, Cu2+, or Zn2+ (1-4, respectively), are reported. These complexes serve as supramolecular building blocks that self-assemble when crystallized to generate a single, well defined structure in the solid state. 2,4,6-Pyridinetricarboxylate anions and imidazolium cations form strong ionic hydrogen bonds that dominate crystal packing in compounds 1-4 by forming three-dimensional (3-D) networks of molecules. These networks consist of hydrogen-bonded layers of molecules defined by N-H…O interactions that are joined in the third dimension by O-H…O interactions. This 3-D network provides a supramolecular framework with which to control and predict molecular packing by design for engineering the structures of crystals. Furthermore, compounds 1-4 create a robust organic host lattice that accommodates a range of different transition metals without significantly altering the molecular packing. Growth of crystals from solutions that contain two or more different metal complexes results in the formation of mixed crystals in which the different metal complexes are incorporated into the crystalline lattice in the same relative molar ratio present in solution. Epitaxial growth of crystals involving deposition of one metal complex on the surface of a seed crystal that contains a second metal complex generates composite crystals in which the different metal complexes are segregated into different regions of the crystals. Compounds 1-4 form crystalline solids that represent a new class of modular materials in which the organic ligands serve as a structural component that defines a single packing arrangement that persists over a range of structures, and in which the metal serves as an interchangeable component with which vary the physical properties of material.


Worcester Polytechnic Institute

Degree Name



Chemistry & Biochemistry

Project Type


Date Accepted





porous material, crystal engineering, Organometallic compounds, Porous materials, Transition metals