Coordination polymers of the alkaline earth metals for applications in synthesis and gas storage
Date of Award
Doctor of Philosophy (PhD)
Physical Sciences and Mathematics
The work presented in this thesis outlines our efforts to synthesize alkaline earth metal
coordination complexes that could potentially serve as gas storage and synthetic precursor
materials. The properties of these complexes are heavily influenced by factors such as the
propensity to aggregate and the absence of energetically available d-orbitals which provide
directionality. These often pose a challenge in obtaining suitable, stable compounds.
Some challenges in the crystallization of alkaline earth coordination complexes involve
the precipitation of insoluble aggregates. Thus, a great part of the work focused on studying
suitable reaction conditions towards the formation of X-ray quality crystals for structural
elucidation. Slow concentration and hydro/solvothermal techniques, among others, were prime
crystallization methods in this work.
The bulk of this thesis is divided in two parts. The first part details our attempts to
synthesize metal organic frameworks (MOFs) of Mg, Ca, Sr and Ba. Our ligands of choice were
the p, m, o-pyridinecarboxylic acids which provide two different binding sites. These consist of
an N-donor and an anionic carboxylic acid, the N-donor located at different positions in the
pyridyl ring depending on the isomer. These are also of low cost and soluble in different organic
The use of pyridinecarboxylic acids resulted in the systematic isolation of five
magnesium coordination complexes, three of which exhibit open-framework character and
remain stable after removal of guests, and two of which are hydrogen bonded networks. Further,
systematic work with the heavier metals resulted in three fully 3-dimensional complexes based
on Ca, Sr and Ba and one hydrogen-bonded Ca complex. A pattern is observed when using the
linear p or angular m-pyridinecarboxylic acid in the presence of MeOH/DMF mixtures, in which
3-dimensional motifs with open-framework (p) and dense (m) character (Mg, Ca and Sr) are
displayed. The dimensionality decreases in the presence of water or strongly coordinating
donors, leading to the formation of hydrogen bound or 2-dimensional complexes.
The second part of this thesis involves the isolation of crown stabilized alkaline earth
tosylates. The work resulted in the isolation of four new crown stabilized alkaline earth tosylates.
Trends observed include an increase in coordination number as the size of the metal increases.
Variation of crown:metal stoichiometry was also studied and resulted in two different calcium
species displaying fully separated (1:1) and contact separated (1:2) ion association modes. For Sr
and Ba, (1:1) stoichiometries resulted in hydrogen bound contact species.
This thesis provides a selection of alkaline earth metal coordination complexes. The
preparation of these complexes has led to the elucidation of their synthetic routes. Full
characterization of the complexes is also provided.
Rosado Flores, Peter Josue, "Coordination polymers of the alkaline earth metals for applications in synthesis and gas storage" (2014). Dissertations - ALL. 200.