RESUMEN
Groups 10-12 metalloporphyrins have been recognized for their numerous properties essential for the development of new sensing materials. In this work, accurate gas-phase enthalpies of formation, ΔfHm0(g,298.15), are predicted for the series of Ni, Cu, Zn, Pd, Ag, and Cd tetraphenylporphyrins (MTPPs) on the basis of the reaction-based Feller-Peterson-Dixon approach and high-level ab initio DLPNO-CCSD(T) calculations. Our recently developed automatic generator of the balanced chemical reactions was employed to reduce the bias of the theoretical ΔfHm0(g,298.15) toward a particular reaction. Theoretical ΔfHm0(g,298.15) for ZnTPP (227.0 ± 3.4 kcal mol-1) does not support the previously reported experimental value of 132 ± 2 kcal mol-1. The origin of the discrepancy probably lies in the experimental solid-state ΔfHm0(ZnTPP, cr,298.15) as it stems from our theoretical evaluations of the ΔfHm0(cr,298.15) values for the entire set of transition metal TPP complexes. The large discrepancy between experiment and theory also holds when different DFT functionals (ωB97M-V, PBE0-D4, and B3LYP-D4) paired with quadruple-ζ quality basis sets are used for the theoretical calculations. Experimental revisiting of the solid-state enthalpy of formation of ZnTPP and analogue measurements for other transition metal TPPs are needed to resolve the observed discrepancy. Based on the predicted enthalpies of formation of MTPPs, the relative energies of the metal-ligand bonding are evaluated and the trends are compared to those for the complexes of the unsubstituted porphyrin with the same set of metals derived in [Can. J. Chem., 2009, 87, 1063]. According to both studies, Pd complexes exhibit the strongest bonding, while the Cd species are the least stable metallocomplexes within the considered series.
RESUMEN
A new database, 16OSTM10, containing 10 conformations for each of 16 non-multireference realistic-size open-shell transition metal (OSTM) complexes has been developed. Contemporary composite density functional theory (DFT) (PBEh-3c and B97-3c), semiempirical (PM6 and PM7) and the GFNn-xTB/FF family methods were examined against conventional DFT (PBE-D3(BJ), PBE0-D3(BJ), M06 and ωB97X-V) to reproduce the conformational energies. While good performance is observed for the conventional (the average Pearson correlation coefficient is ρ = 0.91) and composite DFT (average ρ = 0.93), semiempirical and force-field methods should still be used with caution for these challenging compounds. The corresponding average ρ values are 0.53 (PM6 and PM7), 0.75 (GFN1-xTB and GFN2-xTB) and 0.62 (GFN-FF). Accounting for the intramolecular dispersion interactions turned out to be crucial for 4 OSTM complexes bearing bulky substituents in close proximity to each other. The influence of the scalar relativistic effects on the conformational energies is negligible for the considered 3d metal species.