Enhancement with Hirshfeld surface analysis of structural, electrical, dielectric and luminescent performance of two bioactive V-substituted polytungstates

Abstract

Two new V-substituted polytungstates of piperazinium derivatives, (H2pip)2[V2W4O19]·4H2O (1) and (H2pipEtOH)2[V2W4O19]·4H2O (2), (H2pip = piperazin-1,4-dium; H2pipEtOH = 1-ethylhydroxy-piperazin-1,4-dium), were synthesized in aqueous solution and characterized by ICP and elemental analysis, X-ray diffraction, IR, Raman, UV–Visible, luminescence, DSC and conductivity measurements. X-ray structural and Hirshfeld surface analysis of 1 and 2 with fingerprint plots evidenced polymeric-3D-hydrogen bonded networks of porous extended polyanionic frameworks filled by H2pip and H2pipEtOH dications. Inspection of intermolecular interactions in crystal packing of 1 and 2, via Hirshfeld surface analysis reveals that about two-thirds of the close contacts are associated with O⋯H/H⋯O intermolecular interactions. The conductivity and dielectric behavior of both compounds have been studied as a function of temperature and frequency. The electrical analysis shows that the Nyquist plots (Z″ versus Z′) are well fitted to an equivalent circuit model which consists of a parallel combination of a bulk resistance R and constant phase elements CPE. Besides, the dielectric constants ε′, ε″ and loss tangent (tan(δ)) versus frequency, at several temperatures, show a distribution of relaxation times. Furthermore, the activation energy responsible for relaxation has been evaluated and found to be close to the conductivity. Moreover, the biological properties of both compounds were investigated showing promising antibacterial and antifungal activities.