Synthesis, solvatochromic tuning, and charge transport properties of bimetallic (m2(dpbd)(oac)2) (m = cu, ni, & zn) complexes: a study of magnetic hardness and semiconducting behavior

In this research, we report the synthesis and complete characterization of multiple bimetallic complexes that were based on the ligand 2,5-bis(pyridin-2-yl)benzene-1,4-diol (DPBD). The complexes (M2(DPBD)(OAc)2) (M = Cu(II), Ni(II), &Zn(II)) were prepared using an easy reflux process and analyzed by methods of UV-Vis, Photoluminescence (PL), and Thermogravimetric Analysis (TGA). Major ligand-to-metal charge transfer (LMCT) transitions and a small reduction of the optical band gap (Eg) from 3.48 eV in the free ligand to as low as 2.63 eV in the complexes were shown by UV-Vis spectroscopy. The photoluminescence studies showed a coordination-induced blue shift and suppression of Excited-State Intramolecular Proton Transfer (ESIPT), with the Zn (II) complex showing Chelation-Enhanced Fluorescence (CHEF) in protic media. VSM-based magnetic studies at 300 K demonstrated that (Ni2(DPBD)) was a magnetically harder material than (Cu2(DPBD)), displaying increased saturation magnetization (3.14 B.M.) and coercivity. In addition, AC conductivity and dielectric analyses verify the semi-conductivity of the frameworks, where (Cu2(DPBD)) has the highest conductivity (75 x 10-4 Ω-1m-1). Nyquist plots (temperature dependent) showed a thermally activated hopping mechanism with systematic resistance reduction; these bimetallic systems exhibit potential for both optoelectronic and temperature-sensing applications.