Bond energies of ThO+ and ThC+: A guided ion beam and quantum chemical investigation of the reactions of thorium cation with O2 and CO

Abstract

Kinetic energy dependent reactions of Th(+) with O2 and CO are studied using a guided ion beam tandem mass spectrometer. The formation of ThO(+) in the reaction of Th(+) with O2 is observed to be exothermic and barrierless with a reaction efficiency at low energies of k/kLGS = 1.21 ± 0.24 similar to the efficiency observed in ion cyclotron resonance experiments. Formation of ThO(+) and ThC(+) in the reaction of Th(+) with CO is endothermic in both cases. The kinetic energy dependent cross sections for formation of these product ions were evaluated to determine 0 K bond dissociation energies (BDEs) of D0(Th(+)-O) = 8.57 ± 0.14 eV and D0(Th(+)-C) = 4.82 ± 0.29 eV. The present value of D0 (Th(+)-O) is within experimental uncertainty of previously reported experimental values, whereas this is the first report of D0 (Th(+)-C). Both BDEs are observed to be larger than those of their transition metal congeners, TiL(+), ZrL(+), and HfL(+) (L = O and C), believed to be a result of lanthanide contraction. Additionally, the reactions were explored by quantum chemical calculations, including a full Feller-Peterson-Dixon composite approach with correlation contributions up to coupled-cluster singles and doubles with iterative triples and quadruples (CCSDTQ) for ThC, ThC(+), ThO, and ThO(+), as well as more approximate CCSD with perturbative (triples) [CCSD(T)] calculations where a semi-empirical model was used to estimate spin-orbit energy contributions. Finally, the ThO(+) BDE is compared to other actinide (An) oxide cation BDEs and a simple model utilizing An(+) promotion energies to the reactive state is used to estimate AnO(+) and AnC(+) BDEs. For AnO(+), this model yields predictions that are typically within experimental uncertainty and performs better than density functional theory calculations presented previously.

Periodic trends in gas‐phase oxidation and hydrogenation reactions of lanthanides and 5d transition metal cations

“…As noted above, it is expected that the CeC + BDE is larger than listed in Table 1, and the comparison to ThC + is consistent with that hypothesis. Theory shows that the bonding character of these molecules parallels that described above (Cox, Armentrout, & deJong, 2016; Cox, Citir, et al, 2016).…”

“…Cross sections for reactions of CO to form MO + (part A) and MC + (part B) with Pr + (blue squares) (Ghiassee et al, 2021), Nd + (pink diamonds) (Ghiassee et al, 2019), Sm + (purple triangles) (Cox et al, 2015), Gd + (green inverted triangles) (Demireva et al, 2016), and Th + (black circles) (Cox, Citir, et al, 2016), as measured using GIBMS. The arrow indicates the BDE of CO at 11.111 eV [Color figure can be viewed at wileyonlinelibrary.com]…”

Hydrolysis of Metal Dioxides Differentiates d-block from f-block Elements: Pa(V) as a 6d Transition Metal; Pr(V) as a 4f “Lanthanyl”

“…12 The issue of differing influences of f-versus d-orbitals on bonding in lanthanide and actinide compounds has been deliberated extensively. [13][14][15][16][17][18][19][20][21] Thorium(IV) can be considered as the first 6d transition metal element, 22 and uranium(IV) as the first true 5f actinide, reflecting decreasing energy of 5f relative to 6d orbitals with increasing nuclear charge. 23 The shift from d-block ThO2 to f-block UO2 2+ suggests that isoelectronic PaO2 + could be intermediate in character, 11,21 raising the issue of whether it is more like a d-block transition metal dioxide or a 5f actinyl.…”

Highly Accurate CCSDT(Q)/CBS Reaction Barrier Heights for a Diverse Set of Transition Structures: Basis Set Convergence and Cost-Effective Approaches for Estimating Post-CCSD(T) Contributions

“…Normally, the CCSDT(Q) method is used for investigating relatively small transition structures (TSs) with pronounced multireference character. For instance, for reactions involving oxygen-rich species 25,26,27,28,29,30,31,32,33,34,35,36,37 and other small TSs. 38,39,40,41,42,43,44,45,46,47 The aim of the present work is to provide a systematic examination of basis set convergence of post-CCSD contributions (up to CCSDT(Q)) for a diverse set of reaction barrier heights.…”