Pyridine ligands are widely used for making transition metal complexes for catalysis and metal-organic frameworks (MOFs). 

Canadian chemists reasoned that the lack of interest in tetrahedral ligand geometries was due to synthetic difficulties.

They now have remedied that situation using a robust tetraphenylmethane framework as the core, which they suggest would overcome synthetic issues. They made tetra-(4-(4-pyridyl)phenyl)methane, TPPM, from simple starting materials and describe this as an excellent, rigid building block for MOFs with potential for catalysis, separations, and gas storage.

• A tetrapyridine ligand with a rigid tetrahedral core forms metal–organic frameworks with PtS type architecture,
  Christopher B. Caputo, V. Nicholas Vukotic, Natalie M. Sirizzotti and Stephen J. Loeb,
  Chem. Commun. 2011.
  DOI: 10.1039/C1CC12188J