Multifunctional [(phenantroline-κ2 N, N′)-bis(6-phenylpyridine-2-carboxylate-κ2 N,O) cobalt(II)]monohydrate, single crystals: a platform for sustainable development goals

Cobalt(II) coordination compound [(phenanthroline-κ²N,N′)-bis(6-phenylpyridine-2-carboxylate-κ²N,O)cobalt(II)] H2O (PPPC) was produced in a mixed water–ethanol medium using a controlled slow-evaporation method, producing optically transparent and morphologically stable crystals appropriate for the assessment of multifunctional properties. An orthorhombic P2₁2₁2₁ structure with a deformed octahedral Co(II) coordination environment was established by single-crystal X-ray diffraction. Optical studies showed exceptional transparency throughout the visible spectrum and a clearly defined absorption edge at 336 nm, suggesting suitable for photonic components. Dielectric research revealed a distinctive drop in loss and permittivity with frequency, which is consistent with little space-charge contribution and strong insulating behaviour. While the figure of merit showed excellent responsivity in the 42–45 °C region, indicating stable thermally induced polarisation dynamics, pyroelectric investigations showed a distinct peak near 50 °C. Switchable polarisation and weak ferromagnetic ordering were verified by ferroelectric and magnetic hysteresis tests, confirming PPPC’s status as a polar multifunctional material. A second-harmonic output of 71.32 mV, roughly three times that of KDP, was obtained using nonlinear optical characterisation using the Kurtz–Perry method. Ultrafast excitation generated broadband terahertz radiation through optical rectification. PPPC is positioned as a promising coordination crystal for new optoelectronic, nonlinear optical, and multifunctional device applications according to these combined structural and functional findings.