Comparison of density functionals for differences between the high- (5T2g) and low- (1A1g) spin states of iron(II) compounds. IV. Results for the ferrous complexes [Fe(L)('NHS4')].

Previous work testing density functionals for use in calculating high-spin-low-spin energy differences, deltaE(HL), for iron(II) spin-crossover transitions has tended to conclude that only properly reparametrized hybrid functionals can predict deltaE(HL) since it seems to depend critically on a correct description of the electron pairing energy governed by the exchange term. Exceptions to this rule are the previous three papers (I, II, and III in the present series of papers) where it was found that modern generalized gradient approximations (GGAs) and meta-GGAs could do as well as hybrid functionals, if not better, for this type of problem. In the present paper, we extend these previous studies to five more molecules which are too large to treat with high-quality ab initio calculations, namely, the series [Fe(L)('NHS(4)')], where NHS(4)=2.2'-bis(2-mercaptophenylthio)diethylamine dianion, and L=NH(3), N(2)H(4), PMe(3), CO, and NO(+). Since we know of no reliable experimental estimate of deltaE(HL), we content ourselves with a comparison against the experimentally determined ground-state spin symmetry including, in so far as possible, finite-temperature effects. Together with the results of Papers I, II, and III, this paper provides a test of a large number of functionals against the high-spin/low-spin properties of a diverse set of Fe(II) compounds, making it possible to draw some particularly interesting conclusions. Trends among different classes of functionals are discussed and it is pointed out that there is at least one functional, namely, the OLYP generalized gradient approximation, which is able to give a reasonably good description of the delicate spin energetics of Fe(II) coordination compounds without resorting to hybrid functionals which require the relatively more expensive calculation of a Hartree-Fock-type exchange term.

[1]  Parr,et al.  Development of the Colle-Salvetti correlation-energy formula into a functional of the electron density. , 1988, Physical review. B, Condensed matter.

[2]  P. Gütlich,et al.  Dynamics of spin state conversion processes in the solid state , 1989 .

[3]  Gustavo E. Scuseria,et al.  Performance of a kinetic energy density-dependent functional (VSXC) for predicting vibrational frequencies , 1999 .

[4]  A. Becke,et al.  Density-functional exchange-energy approximation with correct asymptotic behavior. , 1988, Physical review. A, General physics.

[5]  Axel D. Becke,et al.  Simulation of delocalized exchange by local density functionals , 2000 .

[6]  Wang,et al.  Generalized gradient approximation for the exchange-correlation hole of a many-electron system. , 1996, Physical review. B, Condensed matter.

[7]  Axel D. Becke,et al.  Density‐functional thermochemistry. IV. A new dynamical correlation functional and implications for exact‐exchange mixing , 1996 .

[8]  S. Seki,et al.  Phonon coupled cooperative low-spin 1A1high-spin 5T2 transition in [Fe(phen)2(NCS)2] and [Fe(phen)2(NCSe)2] crystals , 1974 .

[9]  Markus Reiher,et al.  Theoretical study of the Fe(phen)(2)(NCS)(2) spin-crossover complex with reparametrized density functionals. , 2002, Inorganic chemistry.

[10]  M. Reiher,et al.  Assertion and validation of the performance of the B3LYP* functional for the first transition metal row and the G2 test set , 2002 .

[11]  L. Lindoy,et al.  Complexes of iron(II),cobalt(II) and nickel(II) with α-diimines and related bidentate ligands , 1967 .

[12]  J. Perdew,et al.  Density-functional approximation for the correlation energy of the inhomogeneous electron gas. , 1986, Physical review. B, Condensed matter.

[13]  R. Dreizler,et al.  Density Functional Theory: An Approach to the Quantum Many-Body Problem , 1991 .

[14]  Fred A. Hamprecht,et al.  Development and assessment of new exchange-correlation functionals , 1998 .

[15]  L. Wiehl,et al.  Structure determination and investigation of the high-spin .tautm. low-spin transition of tris[2-(aminomethyl)pyridine]iron(2+) dibromide.monoethanol , 1986 .

[16]  Gustavo E. Scuseria,et al.  A novel form for the exchange-correlation energy functional , 1998 .

[17]  F. Neese,et al.  Comparison of density functionals for energy and structural differences between the high- [5T2g: (t2g)4(eg)2] and low- [1A1g: (t2g)6(eg)0] spin states of the hexaquoferrous cation [Fe(H2O)6]2+. , 2004, The Journal of chemical physics.

[18]  J. Harvey,et al.  DFT computation of relative spin-state energetics of transition metal compounds , 2004 .

[19]  T. Ziegler.  Approximate Density Functional Theory as a Practical Tool in Molecular Energetics and Dynamics , 1991 .

[20]  T. Hofmann,et al.  Transition metal complexes with sulfur ligands CVI. Phosphine and azido [Fe(L)(‘NHS4’)] complexes; structural characterization of the key complex [Fe(‘NHS4’)]·THF (L=PMe3, PBu3, PMe2Ph, PMePh2, N3−; ‘NHS4’2−=dianion of 2,2′-bis-(2-mercaptophenylthio)diethylamine) , 1994 .

[21]  M. Reiher,et al.  Reparameterization of hybrid functionals based on energy differences of states of different multiplicity , 2001 .

[22]  A. Schäfer,et al.  Fully optimized contracted Gaussian basis sets of triple zeta valence quality for atoms Li to Kr , 1994 .

[23]  F. Neese,et al.  Comparison of density functionals for energy and structural differences between the high- [5T2g:(t2g)4(eg)2] and low- [1A1g:(t2g)6(eg)0] spin states of iron(II) coordination compounds. II. More functionals and the hexaminoferrous cation, [Fe(NH3)6]2+. , 2005, The Journal of chemical physics.

[24]  N. Handy,et al.  Left-right correlation energy , 2001 .

[25]  J. Sancho‐García,et al.  Assessment of recently developed exchange-correlation functionals for the description of torsion potentials in pi-conjugated molecules. , 2004, The Journal of chemical physics.

[26]  H. Bolvin.  d → d Spectrum and High-Spin/Low-Spin Competition in d6 Octahedral Coordination Compounds: ab Initio Study of Potential Energy Curves , 1998 .

[27]  Jackson,et al.  Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation. , 1992, Physical review. B, Condensed matter.

[28]  Singh,et al.  Erratum: Atoms, molecules, solids, and surfaces: Applications of the generalized gradient approximation for exchange and correlation , 1993, Physical review. B, Condensed matter.

[29]  Wolfram Koch,et al.  A Chemist's Guide to Density Functional Theory , 2000 .

[30]  K. Burke,et al.  Erratum: Generalized gradient approximation for the exchange-correlation hole of a many-electron system [Phys. Rev. B 54 , 16 533 (1996)] , 1998 .

[31]  L. Duelund,et al.  Free energy of spin-crossover complexes calculated with density functional methods. , 2001, Inorganic chemistry.

[32]  Burke,et al.  Generalized Gradient Approximation Made Simple. , 1996, Physical review letters.

[33]  R. Parr.  Density-functional theory of atoms and molecules , 1989 .

[34]  J. Beattie,et al.  Partial molal volumes of spin-equilibrium metal complexes , 1986 .