Structural Diversity and Luminescence Properties of Coordination Polymers Built With a Rigid Linear Dicarboxylate and Zn(II)/Pb(II) Ion

A rigid linear ligand incorporating
a carboxylic acid group at
either end, p-terphenyl-4,4″-dicarboxylic
acid, 2′,5′-dimethyl (H2L) has been used to construct four coordination
polymers with Zn­(II) through solvothermal techniques. The four products
formed are formulated as {[Zn3(L)2(OH)2]·8EtOH·4DMF}n (1), {[Zn­(L)­(bpmp)0.5]·EtOH·1/2DMF}n (2), {[(Zn)0.5(L)0.5(py)0.5]·5/2DMF·EtOH}n (3), and [Zn­(L)­(HNMe2)]n (4). With Pb­(NO3)2 the ligand affords two polymers, {[Pb2(L)1.5(O)0.5]·EtOH·2H2O}n (5) and {[Pb3(L)3(H2O)]·6H2O}n (6). All
of these compounds have been characterized by single crystal X-ray
diffraction, infrared spectroscopy, thermogravimetry, elemental analysis,
and powder X-ray diffraction measurements. Topological analyses reveal
that complex 2 is a 6-connected pcu net,
while complexes 3 and 4 are simplified as
a 4-connected sql net. In the case of complexes 1 and 6, one-dimensional rod-shaped metal carboxylate
based secondary building units have been obtained. However, an uncommon
structure and topology have been obtained in complex 5. Surprisingly, such type of parallel ladder-like packing is not
explored much in coordination polymers. Solid-state photoluminescence
studies have been carried out for all of the complexes upon excitation
at 347 nm at room temperature.