Little is so far known about the magnetism of the $A_2{B}_2{\mathrm{O}}_7$ monoclinic layered perovskites that replace the spin-ice supporting pyrochlore structure for $r_A/r_B>1.78$. We show that high quality monoclinic ${\mathrm{Pr}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ single crystals with a three-dimensional network of non-Kramers ${\mathrm{Pr}}^{3+}$ ions that interact through edge-sharing superexchange 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 ${\mathrm{Pr}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ were investigated using x-ray diffraction, transmission electron microscopy, and magnetization measurements. Synthesis of polycrystalline samples with the nominal compositions of ${\mathrm{Pr}}_2{\mathrm{Ti}}_{2+x}{\mathrm{O}}_7$ ($-0.16\le x\le 0.16$) showed that deviations from the ${\mathrm{Pr}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ stoichiometry lead to secondary phases of related structures including the perovskite phase ${\mathrm{Pr}}_{2/3}{\mathrm{TiO}}_3$ and the orthorhombic phases ${\mathrm{Pr}}_4{\mathrm{Ti}}_9{\mathrm{O}}_{24}$ and ${\mathrm{Pr}}_2{\mathrm{TiO}}_5$. No indications of site disordering (stuffing and antistuffing) or vacancy defects were observed in the ${\mathrm{Pr}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ majority phase. A procedure for growth of high-structural-quality stoichiometric single crystals of ${\mathrm{Pr}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ by the traveling solvent floating zone method is reported. Thermomagnetic measurements of single-crystalline ${\mathrm{Pr}}_2{\mathrm{Ti}}_2{\mathrm{O}}_7$ 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 ${\mathrm{Pr}}^{3+}$ 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)% noninteracting ${\mathrm{Pr}}^{4+}$ impurities.

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• Crystal growth
• Crystal stoichiometry
• Crystal structure
• Magnetic phase transitions
• Polycrystals