Coexistence of ordered and disordered magnetic moments in [Cu(pyz)$_{2}$(VF$_{6})$]\textbullet 4H$_{2}$O and comparison to [Cu(HF$_{2})$(pyz)$_{2}$]SbF$_{6}$ (pyz = pyrazine)

Quasi-2D [Cu(pyz)$_{2}$(VF$_{6})$]\textbullet 4H$_{2}$O (\textbf{1}) and [Cu(HF$_{2})$(pyz)$_{2}$]SbF$_{6}$ (\textbf{2}) have tetragonal symmetry and consist of 2D [Cu(pyz)$_{2}$]$^{2+}$ square lattices that are linked in 3D by bridging VF$_{6}^{2-}$ (\textbf{1}) or HF$_{2}^{-}$ (\textbf{2}) anions. Magnetic susceptibility shows apparent paramagnetism in \textbf{1} whereas a broad maximum at 12.5 K and sharp kink at 4.3 K indicate short- (SRO) and long-range (LRO) magnetic ordering, respectively, for \textbf{2}. Additional experimental data however, indicate that a LRO state occurs below 3.6 K for \textbf{1}. The observed LRO in \textbf{1} is confined to the Cu-sublattice while the V$^{4+}$ magnetic moments remain disordered. The structural and magnetic behavior of \textbf{1} and \textbf{2} will be described.