Cd(II)-based fish-bone-like 1D coordination polymer: structural elucidation and computational study

{[Cd(L)2(PBT)2]}n (1) [H2L = 5-nitro-isophthalic acid; PBT = 2-pyridin-4-ylbenzothiazole], 1D Coordination Polymer (1D-CP), is characterized by single crystal X-ray diffraction. The structure of 1 contains carboxylate bridges of L2- to Cd(II), where one carboxylate chelates to Cd(II) and the other -COO bridges to two neighboring Cd(II) centers that then form eight-membered dinuclear metallacycles (Cd2C2O4). The 1D chains self-assemble via H-bonding and pi & sdot;& sdot;& sdot;pi interactions to form a supramolecular aggregate that resembles a fish-bone pattern. These interactions are further explored by Hirshfeld Surface Analysis. Density Functional Theory (DFT) computations using the crystallographic parameters of 1 predicted an energy gap, Delta E (EHOMO - ELUMO) of 3.67 eV, which is comparable to the experimental band gap obtained from a Tauc's plot, 3.73 eV. The band gap value demonstrates the semiconducting character and may be used for device fabrication. Furthermore, molecular electrostatic potential (MEP) shows strong electrophilic reaction potential and predicts reactive sites. The PBT ligand is emissive (370 nm) while H2L is non-emissive. DMF suspensions of 1 emit at 525 nm with a long lifetime, 0.715 ns compared to the lifetime of PBT (0.05 ns). This supports that extended conjugation occurs upon formation of the 1D-CP, altering the photophysics.