In summary, we investigated the magnetic properties of triangulene monomer, dimer and their analogues, and predicted their spin-polarization energy (ΔEspin) and magnetic coupling (J) with DLPNO-CCSD(T) and CASSCF/NEVPT2 methods. Our predictions of J for the triangulene dimer with and without the phenylene spacer, i.e. -7.88 meV and -2.42 meV, are consistent with experimental observations. We highlight the importance of including both dynamic and static correlations for the accurate calculation of magnetic interactions. We found that all the molecules, except the triangulene monomer, have open-shell-singlet ground states and AFM interactions with J < 0. On the basis of these results, we suggest a comprehensive dataset with highquality reference values, containing 25 metal-free magnetic molecules. This dataset covers a wide range of ΔEspin from -2.73 eV to -0.34 eV and J from -203 meV to -1.0 meV, which provides an extensive and reliable starting point for future research. In order to assess the performance of DFT functionals for the prediction of ΔEspin and J, we benchmarked 22 functionals for the triangulene monomer and dimer, and 10 functionals for the whole dataset. We found that, although qualitative prediction of ΔEspin and J could be achieved within the DFT framework by carefully choosing the functionals, quantitative accuracy has not been reached yet, especially for systems with relatively weak electron correlations. In general, PBE0, M06-2X and MN15 are recommended for calculating both J and ΔEspin of metal-free magnetic systems, as they have reasonable MAE of 11.74 meV, 12.66 meV and 10.64 meV respectively for J and 0.34 eV, 0.32 eV and 0.31 eV respectively for ΔEspin. On the contrary, most GGA and meta-GGA functionals will underestimate both parameters, for example, PBE with MRE of -144% and -78% for J and ΔEspin respectively. SCAN performs as accurately as many hybrid functionals for ΔEspin with MAE of 0.36 eV, and produces an accurate value for J of the triangulene monomer with a relative error of 2%, indicating its potential for describing systems with strong magnetic coupling and spin-polarization.