Investigating Solid-State Luminescent Properties of New Cadmium(II) and Lead(II) Oxamato-Based Coordination Polymers

Two novel coordination polymers were synthesized through the reaction of the Hpcpa2− ligand (H3pcpa = N-(4-carboxyphenyl)oxamic acid) with cadmium(II) and lead(II) metal ions, yielding [Cd2(Hpcpa)2(H2O)6]n⋅H2O (1) and [Pb(Hpcpa)(H2O)]n (2). Structural analysis by single-crystal X-ray diffraction revealed that 1 consists of one-dimensional zigzag polymeric chains, while 2 is a three-dimensional polymer network. Additionally, investigations of their optical properties were carried out in a comparative study involving the previously reported pcpa-based coordination polymers {[Zn(Hpcpa)(H2O)3]·0.5H2O}n and {[Gd2(Hpcpa)3(H2O)5]·H2O}n], called here as 3 and 4, respectively. Under 330 nm excitation wavelength, all compounds exhibited broad emission bands spanning from 350 to 650 nm. Particularly, 1 and 3 displayed notable external quantum yields of 15.4 and 12.8%, respectively, highlighting their potential in luminescent applications.