ИСТИНА

Triethylendiamine, also known as 1,4-diazabicyclo[2.2.2]octane (DABCO) is a rigid bicyclic tertiary amine with two equivalent nitrogen atoms. Its well-defined geometry, strong basicity, and ability to form stable hydrogen-bonded frameworks make it a versatile building block in crystal engineering, supramolecular chemistry, and molecular ferroelectrics. DABCO perrhenate (dabcoHReO4) is particularly interesting because it belongs to a rare class of hydrogen-bonded ferroelectrics: its spontaneous polarization originates from the collective ordering of parallel, bistable NH···N hydrogen bonds between DABCO cations [1]. This gives the material a relatively large and thermally stable polarization compared to many other molecular ferroelectrics. The crystal also shows distinct dielectric phase transitions and well-defined vibrational signatures of the ReO₄⁻ anion [2]. Beyond fundamental interest in proton-driven ferroelectricity, dabcoHReO₄ has been explored in flexible piezo- and pyroelectric nanogenerators, highlighting its potential for low-cost, lightweight energy-harvesting devices [3]. However, information about it technetium analogue is missing. Moreover, one can suggest the existence of structures with second hydrogen also substituted with another equivalent of DABCO, enhancing the knowledge of technetium-containing complexes. Besides that, physico-chemical properties of these type of compound might be of additional interest, both fundamental and applied. The current work is devoted to the structural properties of technetium- or rhenium-containing triethylenediamine complexes alongwith its thermal stability. Complexes were obtained from aqueous solutions as single crystals and investigated by X-ray diffraction, termogravimetry and IR-spectroscopy techniques. Moreover, for the compounds dabcoHTcO4 and dabco(TcO4)2 Geometry optimization and vibrational spectra calculations were performed using the DFT method and the Quantum ESPRESSO package. Non-valent interactions stabilizing the structure were analyzed for the optimized structures using Multiwfn software.