Contrasting low-dimensional magnetism in the 3D metal-organic frameworks [Cu(VF$_{6})$(pyz)$_{2}$]\textbullet 4H$_{2}$O and [Cu(HF$_{2})$(pyz)$_{2}$]SbF$_{6}$ (pyz = pyrazine)*

[Cu(VF$_{6})$(pyz)$_{2}$]\textbullet 4H$_{2}$O (\textbf{1}) and [Cu(HF$_{2})$(pyz)$_{2}$]SbF$_{6}$ (\textbf{2}) form tetragonal frameworks that 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 data shows apparent paramagnetism, although not simple Curie-Weiss behavior, in \textbf{1}. For \textbf{2}, a broad maximum in $\chi (T)$ at 12.5 K and a sharp kink at 4.3 K indicate short- (SRO) and long-range (LRO) magnetic ordering, respectively. Additional experimental data for \textbf{1} (e.g., heat capacity and $\mu ^{+}$SR) however, indicate that a LRO state occurs below 3.6 K whereas pulsed-field magnetization data suggest a superposition of AFM Cu$^{2+}$ layers and fluctuating V$^{4+}$ moments. The structural and magnetic behavior of \textbf{1} and \textbf{2} will be described as well as possible new directions.