  Little is so far known about the magnetism of the $\rm A_2B_2O_7$ monoclinic
layered perovskites that replace the spin-ice supporting pyrochlore structure
for $r_A/r_B>1.78$. We show that high quality monoclinic Pr$_2$Ti$_2$O$_7$
single crystals with a three-dimensional network of non-Kramers Pr$^{3+}$ ions
that interact through edge-sharing super-exchange interactions, form a singlet
ground state quantum paramagnet that does not undergo any magnetic phase
transitions down to at least 1.8 K. The chemical phase stability, structure,
and magnetic properties of the layered perovskite Pr$_2$Ti$_2$O$_7$ were
investigated using x-ray diffraction, transmission electron microscopy, and
magnetization measurements. Synthesis of polycrystalline samples with the
nominal compositions of Pr$_2$Ti$_{2+x}$O$_7$ ($-0.16 \leq x \leq 0.16$) showed
that deviations from the Pr$_2$Ti$_2$O$_7$ stoichiometry lead to secondary
phases of related, structures including the perovskite phase Pr$_{2/3}$TiO$_3$
and the orthorhombic phases Pr$_4$Ti$_9$O$_{24}$ and Pr$_2$TiO$_5$. No
indications of site disordering (stuffing and anti-stuffing) or vacancy defects
were observed in the Pr$_2$Ti$_2$O$_7$ majority phase. A procedure for growth
of high-structural-quality, stoichiometric single crystals of Pr$_2$Ti$_2$O$_7$
by the traveling solvent floating zone (TSFZ) method is reported.
Thermo-magnetic measurements of single-crystalline Pr$_2$Ti$_2$O$_7$ reveal an
isolated singlet ground state that we associate with the low symmetry crystal
electric field environments that split the $2J+1=9$-fold degenerate
spin-orbital multiplets of the four differently coordinated Pr$^{3+}$ ions into
36 isolated singlets resulting in an anisotropic temperature independent
van-Vleck susceptibility at low $T$. A small isotropic Curie term is associated
with 0.96(2)\% non-interacting Pr$^{4+}$ impurities.
