Two novel mononuclear compounds, formulated as [Co(phen)(Pae)(H2O)(3)]center dot H2O (1) and [Ni(phen)(pae) (H2O)(3)]center dot H2O (2) (phen = 1,10-phenanthroline, pae = o-pthalic acid), has been synthesized and structurally characterized. The magnetic measurement revealed that compound 1 and 2 could possess antiferromagnetic exchange interactions between Co-II/Ni-II ions through the hydrogen bonds-bridging. The low temperature heat capacity of compound 1 and 2 were measured using the heat capacity option of a Quantum Design Physical Property Measurement System (PPMS) in the temperature range between (1.9-300) K. The measured heat capacities were fitted to a series of theoretical and empirical models, and the corresponding thermodynamic functions were consequently calculated based on the fitting parameters. Moreover, the heat capacities of these two compounds behave an upturn below 10 K, which could be attributed to the Schottky effect occurring at this low temperature region.