The role of the intermediate triplet state in iron-catalyzed multi-state C–H activation

Mirzanejad, Amir; Varganov, Sergey A.

doi:10.1039/d2cp02733j

Cited by 1 publication

(9 citation statements)

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“…Transferring electron density from the C–H bond to the d z 2 orbital of Fe stabilizes the singlet state, while the quintet and triplet state TSs are destabilized by the repulsion with the single electron already present on the d z 2 orbital. The more efficient C–H bond activation in the singlet state is also supported by the electronic structure calculations …”

Section: Iron-catalyzed Multistate C–h Bond Activationsupporting

confidence: 53%

“…Because the lowest energy TS is characterized by a different (singlet) spin state than the ground (quintet) state of the reactant, it is likely that the low-temperature C–H bond activation involves transitions between different spin states. The existence of the interstate crossings was confirmed by locating the MECPs between the quintet–triplet and triplet–singlet states . The calculated SOC values of 420 and 660 cm –1 at the MECP geometries between the quintet–triplet (MECP1) and triplet–singlet (MECP2) crossings indicate strong coupling between these electronic states.…”

Section: Iron-catalyzed Multistate C–h Bond Activationmentioning

confidence: 82%

“…The existence of the interstate crossings was confirmed by locating the MECPs between the quintet−triplet and triplet−singlet states. 73 The calculated SOC values of 420 and 660 cm −1 at the MECP geometries between the quintet−triplet (MECP1) and triplet−singlet (MECP2) crossings indicate strong coupling between these electronic states. This is in contrast to a very small SOC (zero according to the first-order perturbation theory) between the quintet and singlet states, responsible for the previously proposed two-state quintet−singlet reaction mechanism.…”

Section: ■ Spin-forbidden Transitions In Metal−sulfur Proteinsmentioning

confidence: 97%

“…■ IRON-CATALYZED MULTISTATE C−H BOND ACTIVATION Another important example of formally spin-forbidden reactions involving first-row transition metals is the spin-accelerated C(sp 2 )−H bond activation by the Fe(II) catalyst. 73 In this reaction, the direct phenylation of α-benzoquinoline is carried out in tetrahydrofuran (THF) solvent at 0 °C, while most of the catalyzed bond activation reactions require a much higher temperature. 74 A σ-bond metathesis mechanism governs this C−H activation through the formation of a four-membered metallacycle transition state (TS), without affecting the oxidation state of the iron center.…”

Section: ■ Spin-forbidden Transitions In Metal−sulfur Proteinsmentioning

confidence: 99%

“…The more efficient C−H bond activation in the singlet state is also supported by the electronic structure calculations. 73 Because the lowest energy TS is characterized by a different (singlet) spin state than the ground (quintet) state of the reactant, it is likely that the low-temperature C−H bond activation involves transitions between different spin states. The existence of the interstate crossings was confirmed by locating the MECPs between the quintet−triplet and triplet−singlet states.…”

Section: ■ Spin-forbidden Transitions In Metal−sulfur Proteinsmentioning

confidence: 99%

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Predicting Kinetics and Dynamics of Spin-Dependent Processes

Dergachev

Rooein

et al. 2023

Acc. Chem. Res.

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Metrics & MoreArticle Recommendations CONSPECTUS: Predicting mechanisms and rates of nonadiabatic spin-dependent processes including photoinduced intersystem crossings, thermally activated spin-forbidden reactions, and spin crossovers in metal centers is a very active field of research. These processes play critical roles in transition-metal-based and metalloenzymatic catalysis, molecular magnets, lightharvesting materials, organic light-emitting diodes, photosensitizers for photodynamic therapy, and many other applications. Therefore, accurate modeling of spin-dependent processes in complex systems and on different time scales is important for many problems in chemistry, biochemistry, and materials sciences. Nonadiabatic statistical theory (NAST) and nonadiabatic molecular dynamics (NAMD) are two complementary approaches to modeling the kinetics and dynamics of spin-dependent processes. NAST predicts the probabilities and rate constants of nonradiative transitions between electronic states with different spin multiplicities using molecular properties at only few critical points on the potential energy surfaces (PESs), including the reactant minimum and the minimum energy crossing point (MECP) between two spin states. This makes it possible to obtain molecular properties for NAST calculations using accurate but often computationally expensive electronic structure methods, which is critical for predicting the rate constants of spin-dependent processes. Alternatively, NAST can be used to study spindependent processes in very large complex molecular systems using less computationally expensive electronic structure methods.The nuclear quantum effects, such as zero-point vibrational energy, tunneling, and interference between reaction paths can be easily incorporated. However, the statistical and local nature of NAST makes it more suitable for large systems and slow kinetics. In contrast, NAMD explores entire PESs of interacting electronic states, making it ideal for modeling fast barrierless spin-dependent processes. Because the knowledge of large portions of PESs is often needed, the simulations require a very large number of electronic structure calculations, which limits the NAMD applicability to relatively small molecular systems and ultrafast kinetics.In this Account, we discuss our contribution to the development of the NAST and NAMD approaches for predicting the rates and mechanism of spin-dependent processes. First, we briefly describe our NAST and NAMD implementations. The NAST implementation is an extension of the transition state theory to the processes involving two crossing potential energy surfaces of different spin multiplicities. The NAMD approach includes the trajectory surface hopping (TSH) and ab initio multiple spawning (AIMS) methods. Second, we discuss several applications of NAST and NAMD to model spin-dependent processes in different systems. The NAST applicability to large complex systems is demonstrated by the studies of the spin-forbidden isomerization of the active sites of metal−sulfur pr...

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Section: Iron-catalyzed Multistate C–h Bond Activationsupporting

confidence: 53%

Section: Iron-catalyzed Multistate C–h Bond Activationmentioning

confidence: 82%

Section: ■ Spin-forbidden Transitions In Metal−sulfur Proteinsmentioning

confidence: 97%

Section: ■ Spin-forbidden Transitions In Metal−sulfur Proteinsmentioning

confidence: 99%

Section: ■ Spin-forbidden Transitions In Metal−sulfur Proteinsmentioning

confidence: 99%

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