Quantum Chemistry of d- and f-Block Elements

How Much Electron Donation Is There In Transition Metal Complexes? A Computational Study

“…The donation in open-shell complexes is of course also impacted by the approximations in the theoretical model, and furthermore, there are very important consequences regarding the resulting spin density in open-shell systems. 7,5 The extent of donation overall, and in particular the balance of donation in the α and β spin channels, deserve further scrutiny and might benefit from a similar investigation as was carried out here for closed-shell complexes. However, an efficient "relaxed" CCSD(T) code for open-shell systems that can be applied to molecules of the size as studied herein appears not to be available at present.…”

“…For L-M donation, spectroscopic probes such as NMR chemical shifts or nuclear quadrupole interactions can be used, but their interpretation in terms of bonding/donation tends to require accurate supporting calculations. Taken together, the aforementioned points mean that quantum mechanics (QM) based calculations for metal complexes 5 applications of TM complexes, an important question is therefore this: How much donation is actually present in a given system, and do quantum chemical calculations at different levels of approximation represent it accurately? TM systems that are of practical interest tend to be large by the standards of numerical quantum chemistry.…”

“…TM systems that are of practical interest tend to be large by the standards of numerical quantum chemistry. 5 It is therefore extremely important that computational methods are accurate, but also feasible in terms of the computational cost associated with the calculations. Kohn−Sham (KS) density functional theory (DFT), abbreviated here as Kohn−Sham theory (KST), is presently the only electronic structure method that can be applied to TM systems of broad interest, in a variety of application fields, without compromising unduly in terms of the accuracy of the results or computational cost.…”

Uncovering Chemical Homology of Superheavy Elements: A Close Look at Astatine

“…In 2c-RDFT calculations, we employ the collinear version of the method in NWCHEM 56 and the non-collinear one implemented in TURBOMOLE 57,58 and a stand-alone program. 59 Choosing an appropriate XCF approximation for relativistic electronic-structure calculations of heavy-element species is a lingering problem 60 that persists in the case of At compounds. 61 In the absence of relativistic XCFs suitable for molecular quantum-chemical modelling, 62 we base our choice on previously documented successes and additional reliability tests in the present work.…”