Theoretical Study of Actinide Complexes with Macropa

Abstract

The complex formation of actinium (Ac 3+ ) and californium (Cf 3+ ) ions with macropa (a promising ligand for medical applications, e.g., in targeted α therapy) has been studied by means of density functional theory (DFT) calculations. This work is focused on the structural and bonding properties, the latter on the basis of charge transfer data and topological properties of the electron density distribution. The effect of water solvent on the energetics has been investigated using the SMD model. A comparative analysis with the related properties of two representative lanthanide (La, Lu) complexes has been performed.

Metal-ligand bonding in bispidine chelate complexes for radiopharmaceutical applications

“…It should be noted that the dissociation energies are likely underestimated by the LC pseudopotential of Ac. In a recent study of the Ac(macropa) complex [34], underestimation by 50 and 48 kJ/mol was found for the electronic (in vacuum) and Gibbs free energies (in solution) of dissociation by the LC pseudopotential (unpublished results). An underestimation in this magnitude would not change the trends in Fig.…”

“…Unfortunately, severe SCF convergence problems occurred with the SC pseudopotential (ECP-60MWB + (14s13p10d8f6g/10s9p5d4f3g) valence basis) of Ac [43,44]; therefore, for this metal, the large-core ECP-78MWB pseudopotential with the contracted (7s6p5d2f1g)/ (6s5p4d2f1g) valence basis [45] set was used. In a recent study on Ac(macropa) complexes including both the SC and LC pseudopotentials for Ac [34], differences in the magnitude of 0.01 Å in the metal-ligand distances and 50 kJ/ mol in the dissociation energies were observed comparing the results obtained by the two Ac pseudopotentials. All the applied pseudopotentials here cover the scalar relativistic effects, which are particularly important for the heavy metals.…”

“…The density functional theory (DFT) computations were carried out with the Gaussian 09 suit of programs [29]. On the basis of the reported good performance of the TPSSh meta-hybrid functional [30] for the molecular geometries and relative stabilities of various complexes [31][32][33][34][35], this functional was applied throughout the present study. The grid specification for the two-electron integrals was 150 radial shells and 974 angular points per shell (150,974; SuperFineGrid keyword) for H, C, N and O and (225,974) for the heavier elements.…”

“…The solvent effects were taken into account using the polarizable continuum model (PCM) [51,52] with radii and non-electrostatic terms from the SMD solvation model by Marenich et al [53]. For La 3+ , Lu 3+ and Ac 3+ , the PCM radii from literature were used (1.874 Å, 1.659 Å [31] and 1.933 Å [34], respectively). For In 3+ and Bi 3+ , no such radii are available; therefore, they were developed in the present study (1.507 Å and 1.723 Å, respectively) on the basis of literature hydration free energies [54].…”

The Evolving Coordination Chemistry of Radiometals for Targeted Alpha Therapy

“…Acyclic picolinates H 4 neunpa [20,21] N 5 O 4 RT, 1 h, pH 5.5, 10 À3 M G H 4 phospa [21] N 4 O 4 77 D RT, 1 h, pH 5.5, 10 À3 M H 4 noneunpa [20] N 4 O 5 90 D RT, 1 h, pH 5.5, 10 À6 M H 4 octapa [21] N 4 O 4 20.13 93 D RT, 1 h, pH 5.5, 10 À5 M H 4 CHXoctapa [21] PSMA; [25][26][27][28][29][30] tetrazine-TCO [31] H 4 DOTP [24] N 4 O 4 Capped inverted square prism 408C, 30 min, pH 10, 10 À2 M 18-Crown-6-based H 2 macropa [32,33] N 4 O 6 Irregular tridecahedron 14.99 99 E RT, 5 min, pH 6, 10 À7 M PSMA; [14,34] trastuzumab [14] H 4 crown N 4 O 6 90 RT, 10 min, pH 5-7, 10 À6 M aMSH [35] A From the La 3þ X-ray crystallographic structure.…”