Density-Functional Theory Investigation of the Geometric, Energetic, and Optical Properties of the Cobalt(II)tris(2,2‘-bipyridine) Complex in the High-Spin and the Jahn−Teller Active Low-Spin States

Abstract

State-of-the-art generalized gradient approximation (GGA) (PBE, OPBE, RPBE, OLYP, and HCTH), meta-GGA (VSXC and TPSS), and hybrid (B3LYP, B3LYP*, O3LYP, and PBE0) functionals are compared for the determination of the structure and the energetics of the D3 [Co(bpy)3](2+) complex in the (4)A2 and (4)E trigonal components of the high-spin (4)T1g([Formula: see text] [Formula: see text] ) state and in the low-spin (2)E state of octahedral (2)Eg([Formula: see text] [Formula: see text] ) parentage. Their comparison extends also to the investigation of the Jahn-Teller instability of the (2)E state through the characterization of the extrema of C2 symmetry of this spin state's potential energy surface. The results obtained for [Co(bpy)3](2+) in either spin manifold are very consistent among the functionals used and are in good agreement with available experimental data. The functionals, however, perform very differently with respect to the spin-state energetics because the calculated values of the high-spin/low-spin energy difference Δ[Formula: see text] vary between -3212 and 3919 cm(-)(1). Semilocal functionals tend to give too large Δ[Formula: see text] values and thus fail to correctly predict the high-spin state as the ground state of the isolated complex, while hybrid functionals tend to overestimate the stability of the high-spin state with respect to the low-spin state. Reliable results are, however, obtained with the OLYP, HCTH, B3LYP*, and O3LYP functionals which perform best for the description of the isolated complex. The optical properties of [Co(bpy)3](2+) in the two spin states are also analyzed on the basis of electronic excitation calculations performed within time-dependent density functional response theory. The calculated absorption and circular dichroism spectra agree well with experimental results.

Spin-crossover in cobalt(II) imine complexes

“…Whereas as the broad band at 14,000 cm −1 and the shoulder at 18,000 cm −1 carry a substantial CD signal, the more intense bands at higher energy only carry a very small signal in relation to their intensity. Indeed, TD-DFT calculations clearly identify the band structure at higher energies as metal-ligand charge transfer transitions [32].…”

“…For cobalt(II) the vibrational frequency shift between the two spin states is much smaller than for iron(II) spin-crossover compounds. It is not expected to be more than 15% for the metal ligand vibrations based on DFT frequency calculations [32]. Alternatively, such frequency calculations in the high-spin and the low-spin state can be used calculate the product in Eq.…”

Characterizing the Solvated Structure of Photoexcited [Os(terpy)2]2+ with X-ray Transient Absorption Spectroscopy and DFT Calculations

“…Frontier Kohn-Sham orbitals were extracted from the converged wave function. In order to obtain accurate electronic energies of the GS and 3 MLCT states, the DFT optimizations were repeated using the B3LYP* [30]/ZORA-TZVP method, which provided accurate spin-state energetics for related transition metal complexes [31,32].…”

Influence of Guest−Host Interactions on the Structural, Energetic, and Mössbauer Spectroscopy Properties of Iron(II)tris(2,2′-bipyridine) in the Low-Spin and High-Spin States: A Density-Functional Theory Study of the Zeolite-Y Embedded Complex

“…However, although they perform quite well for the study of numerous properties of transition metal complexes, 59 they tend to dramatically fail when it comes to the accurate evaluation of the relative energies of the different spin-states of these systems. 6,7,[60][61][62][63][64][65][66][67][68][69][70][71][72][73][74][75][76] [L], respectively, where r Γ designates the average iron-nitrogen bond length in the Γ manifold (Γ ) LS, HS).…”