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163. Arbuznikov AV, Kaupp M (2014) Towards improved local hybrid functionals by calibration
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164. Yu HS, He X, Li SL, Truhlar DG (2016) MN15: a Kohn–Sham global-hybrid exchange–
correlation density functional with broad accuracy for multi-reference and single-reference
systems and noncovalent interactions. Chem Sci 7:5032–5051. https://doi.org/10.1039/
c6sc00705h
165. Sun J, Perdew JP, Ruzsinszky A (2015) Semilocal density functional obeying a strongly
tightened bound for exchange. Proc Natl Acad Sci U S A 112:685–689. https://doi.org/10.
1073/pnas.1423145112
166. Feldt M, Phung QM, Pierloot K, Mata RA, Harvey JN (2019) Limits of coupled-cluster
calculations for non-heme iron complexes. J Chem Theor Comput 15:922–937. https://doi.
org/10.1021/acs.jctc.8b00963
167. Chen H, Lai W, Shaik S (2010) Exchange-enhanced H-abstraction reactivity of high-valent
nonheme iron(IV)-Oxo from coupled cluster and density functional theories. J Phys Chem Lett
1:1533–1540. https://doi.org/10.1021/jz100359h
168. Phung QM, Martín-Fernańdez C, Harvey JN, Feldt M (2019) Ab initio calculations for spingaps of non-heme iron complexes. J Chem Theor Comput 15:4297–4304. https://doi.org/10.
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169. Cao L, Ryde U (2018) Influence of the protein and DFT method on the broken-symmetry and
spin states in nitrogenase. Int J Quantum Chem 118:e25627. https://doi.org/10.1002/qua.
25627
170. Cao L, Caldararu O, Ryde U (2018) Protonation and reduction of the FeMo cluster in
nitrogenase studied by quantum mechanics/molecular mechanics (QM/MM) calculations. J
Chem Theor Comput 14:6653–6678. https://doi.org/10.1021/acs.jctc.8b00778
171. Cao L, Caldararu O, Ryde U (2017) Protonation states of homocitrate and nearby residues in
nitrogenase studied by computational methods and quantum refinement. J Phys Chem B
121:8242–8262. https://doi.org/10.1021/acs.jpcb.7b02714
172. Cao L, Ryde U (2019) Extremely large differences in DFT energies for nitrogenase models.
Phys Chem Chem Phys 21:2480–2488. https://doi.org/10.1039/C8CP06930A
173. Roithova J (2016) Multiple spin-state scenarios in gas-phase reactions. In: Swart M, Costas M
(eds) Spin states in biochemistry and inorganic chemistry: influence on structure and reactivity. Wiley, Chichester, pp 157–183
174. Zhang Q, Bowers MT (2004) Activation of methane by MH
+ (M ¼ Fe, Co, and Ni): a
combined mass spectrometric and DFT study. J Phys Chem A 108:9755–9761. https://doi.
org/10.1021/jp047943t
175. Schwarz H (2004) On the spin-forbiddeness of gas-phase ion–molecule reactions: a fruitful
intersection of experimental and computational studies. Int J Mass Spectrom 237:75–105.
https://doi.org/10.1016/j.ijms.2004.06.006
176. Shaik S, de Visser SP, Ogliaro F, Schwarz H, Schroder D (2002) Two-state reactivity
mechanisms of hydroxylation and epoxidation by cytochrome P-450 revealed by theory.
Curr Opin Chem Biol 6(5):556–567
177. Usharani D, Wang B, Sharon DA, Shaik S (2015) Principles and prospects of spin-states
reactivity in chemistry and bioinorganic chemistry. In: Swart M, Costas M (eds) Spin states in
biochemistry and inorganic chemistry: influence on structure and reactivity. Wiley, Oxford, pp
131–156. https://doi.org/10.1002/9781118898277.ch7
178. Janardanan D, Usharani D, Shaik S (2012) The origins of dramatic axial ligand effects: closedshell Mn
V O complexes use exchange-enhanced open-shell states to mediate efficient H
224
M. Swart
evidence for the involvement of oxoiron(V) oxidants in cleaving strong C–H bonds. Angew
Chem Int Ed 59:7332–7349. https://doi.org/10.1002/anie.201906551
162. Radon M (2019) Benchmarking quantum chemistry methods for spin-state energetics of iron
complexes against quantitative experimental data. Phys Chem Chem Phys 21:4854–4870.
https://doi.org/10.1039/c9cp00105k
163. Arbuznikov AV, Kaupp M (2014) Towards improved local hybrid functionals by calibration
of exchange-energy densities. J Chem Phys 141:204101. https://doi.org/10.1063/1.4901238
164. Yu HS, He X, Li SL, Truhlar DG (2016) MN15: a Kohn–Sham global-hybrid exchange–
correlation density functional with broad accuracy for multi-reference and single-reference
systems and noncovalent interactions. Chem Sci 7:5032–5051. https://doi.org/10.1039/
c6sc00705h
165. Sun J, Perdew JP, Ruzsinszky A (2015) Semilocal density functional obeying a strongly
tightened bound for exchange. Proc Natl Acad Sci U S A 112:685–689. https://doi.org/10.
1073/pnas.1423145112
166. Feldt M, Phung QM, Pierloot K, Mata RA, Harvey JN (2019) Limits of coupled-cluster
calculations for non-heme iron complexes. J Chem Theor Comput 15:922–937. https://doi.
org/10.1021/acs.jctc.8b00963
167. Chen H, Lai W, Shaik S (2010) Exchange-enhanced H-abstraction reactivity of high-valent
nonheme iron(IV)-Oxo from coupled cluster and density functional theories. J Phys Chem Lett
1:1533–1540. https://doi.org/10.1021/jz100359h
168. Phung QM, Martín-Fernańdez C, Harvey JN, Feldt M (2019) Ab initio calculations for spingaps of non-heme iron complexes. J Chem Theor Comput 15:4297–4304. https://doi.org/10.
1021/acs.jctc.9b00370
169. Cao L, Ryde U (2018) Influence of the protein and DFT method on the broken-symmetry and
spin states in nitrogenase. Int J Quantum Chem 118:e25627. https://doi.org/10.1002/qua.
25627
170. Cao L, Caldararu O, Ryde U (2018) Protonation and reduction of the FeMo cluster in
nitrogenase studied by quantum mechanics/molecular mechanics (QM/MM) calculations. J
Chem Theor Comput 14:6653–6678. https://doi.org/10.1021/acs.jctc.8b00778
171. Cao L, Caldararu O, Ryde U (2017) Protonation states of homocitrate and nearby residues in
nitrogenase studied by computational methods and quantum refinement. J Phys Chem B
121:8242–8262. https://doi.org/10.1021/acs.jpcb.7b02714
172. Cao L, Ryde U (2019) Extremely large differences in DFT energies for nitrogenase models.
Phys Chem Chem Phys 21:2480–2488. https://doi.org/10.1039/C8CP06930A
173. Roithova J (2016) Multiple spin-state scenarios in gas-phase reactions. In: Swart M, Costas M
(eds) Spin states in biochemistry and inorganic chemistry: influence on structure and reactivity. Wiley, Chichester, pp 157–183
174. Zhang Q, Bowers MT (2004) Activation of methane by MH
+ (M ¼ Fe, Co, and Ni): a
combined mass spectrometric and DFT study. J Phys Chem A 108:9755–9761. https://doi.
org/10.1021/jp047943t
175. Schwarz H (2004) On the spin-forbiddeness of gas-phase ion–molecule reactions: a fruitful
intersection of experimental and computational studies. Int J Mass Spectrom 237:75–105.
https://doi.org/10.1016/j.ijms.2004.06.006
176. Shaik S, de Visser SP, Ogliaro F, Schwarz H, Schroder D (2002) Two-state reactivity
mechanisms of hydroxylation and epoxidation by cytochrome P-450 revealed by theory.
Curr Opin Chem Biol 6(5):556–567
177. Usharani D, Wang B, Sharon DA, Shaik S (2015) Principles and prospects of spin-states
reactivity in chemistry and bioinorganic chemistry. In: Swart M, Costas M (eds) Spin states in
biochemistry and inorganic chemistry: influence on structure and reactivity. Wiley, Oxford, pp
131–156. https://doi.org/10.1002/9781118898277.ch7
178. Janardanan D, Usharani D, Shaik S (2012) The origins of dramatic axial ligand effects: closedshell Mn
V O complexes use exchange-enhanced open-shell states to mediate efficient H
224
M. Swart