Metal-organic frameworks (MOFs) is the generic term for a class of relatively novel
type of porous materials which have attracted considerable attention over the last two decades
owing to their interesting properties and useful potential applications such as methane1 or
hydrogen2 storage, CO2 capture,3 selective gas separation4 and chemical sensing or explosive
detection5. Also known as porous coordination polymers or crystalline coordination networks,
MOFs are formed through the coordination of metal ions or metal clusters by organic
molecular building blocks usually called spacers, organic linkers or bridging ligands.
One of the most common type of organic linkers employed in the construction of
coordination polymers and MOFs has a rigid aromatic hydrocarbon-based ring assembly as
core and a variable number of carboxylate functions (e.g., terephthalic acid, [1,1′]-biphenyl-
4,4′-dicarboxylic acid, naphthalene-1,5-dicarboxylic acid, etc.). Suzuki coupling of a suitable
halogen-substituted substrate with 4-carboxyphenylboronic acid (or its esters) is often the key
step in building such carboxylate-substituted linkers. The present work deals with the multistep
synthesis and structural characterization of two novel dicarboxylate-type linkers, namely
the symmetrical, terphenyl-based ligand 1, and the unsymmetrical, heterocyle-containing
ligand 2. Organic linker 1 was obtained from 1,2,4,5-tetramethylbenzene through a double
nuclear bromination and Suzuki coupling, whereas linker 2 was prepared starting from 4-
bromoacetophenone through a succession of reaction comprising a Claisen condensation with
diethyl oxalate, pyrazole ring closure using phenylhydrazine and Suzuki coupling. All
intermediates and the final compounds have been fully characterized by NMR spectroscopy.
Acknoledgement: This research was supported by grant „Novel porous coordination polymers with organic
linkers of variable size for gas storage” (POCPOLIG), ID P_37_707, MySMIS code 104810, funding contract
67/8.09.2016.