Molecular mechanics for multiple spin states of transition metal complexes

Deeth, Robert J.; Foulis, D.L.; Williams-Hubbard, Benjamin

doi:10.1039/b305868a

Cited by 24 publications

(20 citation statements)

References 21 publications

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“…Diamagnetic Co III is mainly found in octahedral [18] and tetrahedral geometries, [19] or in tri- [20] and pentacoordinated [21] Co III complexes.T he less usual high spin state is found mainly in all types of geometry but in ad istorted and/orw eak-field environment. [18][19][20][21] Interestingly,t he Co III complexes with intermediate spin S = 1a re found mainly in square planar geometry, [19,22] and are attractive because of their remarkably large D magnitudes of up to 145 cm À1 . [23] Likewise, au nique distorted trigonal bipyramidal S = 1s ystem displaying a D value of + 107 cm À1 has also been reported.…”

Section: Introductionmentioning

confidence: 99%

An Experimental and Theoretical Investigation on Pentacoordinated Cobalt(III) Complexes with an Intermediate S=1 Spin State: How Halide Ligands Affect their Magnetic Anisotropy

Brazzolotto

Gennari

et al. 2015

Chemistry A European J

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What is the most significant result of this study? We report on the experimental and theoretical investigation of the magnetic behavior for as eries of Co III complexes displaying an intermediate S = 1s pin state. The magnetic anisotropy of these complexes , the zero-field splitting parameter (D), shows ad ependence on the nature of the halide:t he largest D value was obtained for the chloride compound and the smallest for the iodide one. Examples of such reported behavior are still very limited and in most of studies, it was observed that the D value increases from the chloride to the iodide metal complexes. By using quantum chemical methods (DFT and CASSCF calculations), we were able to predict and rationalize both the sign and magnitude of D for the three complexes. The DFT method appears as the most appropriate method if one wants to obtain structure-property relationships. No general rule can be extrapolated from the present study and magneto-structural correlations can only be defined though benchmark studies using ac ombination of experimental and theoretical approaches.

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Section: Introductionmentioning

confidence: 99%

An Experimental and Theoretical Investigation on Pentacoordinated Cobalt(III) Complexes with an Intermediate S=1 Spin State: How Halide Ligands Affect their Magnetic Anisotropy

Brazzolotto

Gennari

et al. 2015

Chemistry A European J

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“…In the absence of environmental effects, quantum calculations on anions often lead to occupied orbitals having physically unreasonable positive energies but ionization and/or ligand dissociation is prevented by the finite size of the basis set. 42 To counter this problem, environmental effects can be introduced into theoretical calculations either by explicit consid- eration of the complex surroundings, or by approximating these with a continuum dielectric field. Previous investigations have shown that COSMO solvation is a convenient way of mitigating the structural effects of excess charge on transition metal complexes, 42,64 so we chose this approach to investigate the performance of the RPBE functional further.…”

Section: Resultsmentioning

confidence: 99%

“…42 To counter this problem, environmental effects can be introduced into theoretical calculations either by explicit consid- eration of the complex surroundings, or by approximating these with a continuum dielectric field. Previous investigations have shown that COSMO solvation is a convenient way of mitigating the structural effects of excess charge on transition metal complexes, 42,64 so we chose this approach to investigate the performance of the RPBE functional further. While revPBE and RPBE results in vacuo are very similar, the theoretical superiority of the RPBE functional made this the functional of choice.…”

Section: Resultsmentioning

confidence: 99%

The performance of nonhybrid density functionals for calculating the structures and spin states of Fe(II) and Fe(III) complexes

Deeth

Fey

2004

J Comput Chem

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The local density approximation and a range of nonhybrid gradient corrected density functionals (PW91, BLYP, PBE, revPBE, RPBE) have been assessed with respect to the prediction of geometries and spin-state energy preferences for a range of homoleptic Fe(II)L6 and Fe(III)L6 complexes, where L = Cl-, CN-, NH3, pyridine, imidazole, H2O, O=CH2 and tetrahydrofuran. While the qualitative spin-state energies from in vacuo structure optimizations are reasonable the geometries are relatively poorly treated, especially for [FeCl6]3-/4-. Structural results for all the complexes are significantly improved by including environmental effects. The best compromise between structural and spin-state predictive accuracy was obtained for the RPBE functional in combination with the COSMO solvation approach. This approach systematically overestimates the energetic preference for a low spin state, which is partly due to the well-known effect of the lack of exact exchange in nonhybrid functionals and partly due to the larger solvation stabilization of low-spin complexes that have shorter bond lengths and thus smaller molecular volumes than their high-spin partners. Calculations on low spin [Fe(bipy)3]2+ and [Fe(phen)3]2+ and their ortho methyl substituted analogs, which are high spin at room temperature but cross over to low spin at low temperature, suggest the RPBE/COSMO combination generates low spin states which are too stable by approximately 13 kcal mol(-1).

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“…The strong d electron effects need to be taken into account explicitly and we achieve this by combining MM with a general, ligand field treatment of the stabilization energy associated with the open d shell electrons. [23] LFMM has been successfully applied to a range of problems in coordination, [14,16,17,23,24,44,46,47,[57][58][59] bioinorganic, [15,18,20,42,60] and even organometallic chemistry [61] and we extend it here to Cu-APC systems.…”

Section: Full Papermentioning

confidence: 99%

Molecular modeling for Cu(II)‐aminopolycarboxylate complexes: Structures, conformational energies, and ligand binding affinities

2013

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A ligand field molecular mechanics (LFMM) force field (FF) has been developed for d(9) copper(II) complexes of aminopolycarboxylate ligands. Training data were derived from density functional theory (DFT) geometry optimizations of 14 complexes comprising potentially hexadentate N2O4, tetrasubstituted ethylenediamine (ed), and propylenediamine cores with various combinations of acetate and propionate side arms. The FF was validated against 13 experimental structures from X-ray crystallography including hexadentate N2O4 donors where the nitrogens donors are forced to be cis and bis-tridentate ONO ligands which generate complexes with trans nitrogen donors. Stochastic conformational searches for [Cu{ed(acetate)n(propionate)(4-n)}](2-), n = 0-4, were carried out and the lowest conformers for each system reoptimized with DFT. In each case, both DFT and LFMM predict the same lowest-energy conformer and the structures and energies of the higher-energy conformers are also in satisfactory agreement. The relative interaction energies for n = 0, 2, and 4 computed by molecular mechanics correlate with the experimental log β binding affinities. Adding in the predicted log β values for n = 1 and 3 suggest for this set of complexes a monotonic decrease in log β as the number of propionate arms increases.

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Molecular mechanics for multiple spin states of transition metal complexes

Cited by 24 publications

References 21 publications

An Experimental and Theoretical Investigation on Pentacoordinated Cobalt(III) Complexes with an Intermediate S=1 Spin State: How Halide Ligands Affect their Magnetic Anisotropy

An Experimental and Theoretical Investigation on Pentacoordinated Cobalt(III) Complexes with an Intermediate S=1 Spin State: How Halide Ligands Affect their Magnetic Anisotropy

The performance of nonhybrid density functionals for calculating the structures and spin states of Fe(II) and Fe(III) complexes

Molecular modeling for Cu(II)‐aminopolycarboxylate complexes: Structures, conformational energies, and ligand binding affinities

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