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J Chem Phys 30:1139–1161. https://doi.org/10.1063/1.1730148
136. Baerends EJ, Ricciardi G, Rosa A, van Gisbergen SJA (2002) A DFT/TDDFT interpretation of
the ground and excited states of porphyrin and porphyrazine complexes. Coord Chem Rev
230:5–27
137. Andersson K, Roos BO (1992) Excitation energies in the nickel atom studied with the
complete active space SCF method and second-order perturbation theory. Chem Phys Lett
191:507–514. https://doi.org/10.1016/0009-2614(92)85581-T
138. Saitow M, Becker U, Riplinger C, Valeev EF, Neese F (2017) A new near-linear scaling,
efficient and accurate, open-shell domain-based local pair natural orbital coupled cluster
singles and doubles theory. J Chem Phys 146:164105. https://doi.org/10.1063/1.4981521
139. Flöser BM, Guo Y, Riplinger C, Tuczek F, Neese F (2020) Detailed pair natural orbital-based
coupled cluster studies of spin crossover energetics. J Chem Theor Comput 16:2224–2235.
https://doi.org/10.1021/acs.jctc.9b01109
140. Kats D, Manby FR (2013) The distinguishable cluster approximation. J Chem Phys
139:021102. https://doi.org/10.1063/1.4813481
222
M. Swart
https://doi.org/10.1016/j.cplett.2004.08.032
124. Kepenekian M, Robert V, Le Guennic B (2009) What zeroth-order Hamiltonian for CASPT2
adiabatic energetics of Fe(II)N 6 architectures? J Chem Phys 131:114702. https://doi.org/10.
1063/1.3211020
125. Suaud N, Bonnet M-L, Boilleau C, Labèguerie P, Guihéry N (2009) Light-induced excited
spin state trapping: Ab initio study of the physics at the molecular level. J Am Chem Soc
131:715–722. https://doi.org/10.1021/ja805626s
126. Daku LML, Aquilante F, Robinson TW, Hauser A (2012) Accurate spin-state energetics of
transition metal complexes. 1. CCSD(T), CASPT2, and DFT study of [M(NCH) 6 ]
2+ (M ¼ Fe,
Co). J Chem Theor Comput 8:4216–4231. https://doi.org/10.1021/ct300592w
127. Ma Y, Bandeira NAG, Robert V, Gao E-Q (2011) Experimental and theoretical studies on the
magnetic properties of manganese(II) compounds with mixed isocyanate and carboxylate
bridges. Chem Eur J 17:1988–1998. https://doi.org/10.1002/chem.201002243
128. Radon M, Rejmak P, Fitta M, Bałanda M, Szklarzewicz J (2015) How can [Mo
IV (CN) 6 ]
2À
, an
apparently octahedral (d)
2 complex, be diamagnetic? Insights from quantum chemical calculations and magnetic susceptibility measurements. Phys Chem Chem Phys 17:14890–14902.
https://doi.org/10.1039/c4cp04863f
129. Rudavskyi A, Sousa C, de Graaf C, Havenith RWA, Broer R (2014) Computational approach
to the study of thermal spin crossover phenomena. J Chem Phys 140:184318. https://doi.org/
10.1063/1.4875695
130. Zobel JP, Nogueira JJ, González L (2017) The IPEA dilemma in CASPT2. Chem Sci
8:1482–1499. https://doi.org/10.1039/C6SC03759C
131. Angeli C, Cimiraglia R, Evangelisti S, Leininger T, Malrieu J-P (2001) Introduction of
n-electron valence states for multireference perturbation theory. J Chem Phys
114:10252–10264
132. Phung QM, Wouters S, Pierloot K (2016) Cumulant approximated second-order perturbation
theory based on the density matrix renormalization group for transition metal complexes: a
benchmark study. J Chem Theory Comp 12:4352–4361. https://doi.org/10.1021/acs.jctc.
6b00714
133. Phung QM, Feldt M, Harvey JN, Pierloot K (2018) Toward highly accurate spin state
energetics in first-row transition metal complexes: a combined CASPT2/CC approach. J
Chem Theor Comput 14:2446–2455. https://doi.org/10.1021/acs.jctc.8b00057
134. Li Manni G, Kats D, Tew DP, Alavi A (2019) Role of valence and semicore electron
correlation on spin gaps in Fe(II)-porphyrins. J Chem Theor Comput 15:1492–1497. https://
doi.org/10.1021/acs.jctc.8b01277
135. Gouterman M (1959) Study of the effects of substitution on the absorption spectra of porphin.
J Chem Phys 30:1139–1161. https://doi.org/10.1063/1.1730148
136. Baerends EJ, Ricciardi G, Rosa A, van Gisbergen SJA (2002) A DFT/TDDFT interpretation of
the ground and excited states of porphyrin and porphyrazine complexes. Coord Chem Rev
230:5–27
137. Andersson K, Roos BO (1992) Excitation energies in the nickel atom studied with the
complete active space SCF method and second-order perturbation theory. Chem Phys Lett
191:507–514. https://doi.org/10.1016/0009-2614(92)85581-T
138. Saitow M, Becker U, Riplinger C, Valeev EF, Neese F (2017) A new near-linear scaling,
efficient and accurate, open-shell domain-based local pair natural orbital coupled cluster
singles and doubles theory. J Chem Phys 146:164105. https://doi.org/10.1063/1.4981521
139. Flöser BM, Guo Y, Riplinger C, Tuczek F, Neese F (2020) Detailed pair natural orbital-based
coupled cluster studies of spin crossover energetics. J Chem Theor Comput 16:2224–2235.
https://doi.org/10.1021/acs.jctc.9b01109
140. Kats D, Manby FR (2013) The distinguishable cluster approximation. J Chem Phys
139:021102. https://doi.org/10.1063/1.4813481
222
M. Swart