A DMRG/CASPT2 Investigation of Metallocorroles: Quantifying Ligand Noninnocence in Archetypal 3d and 4d Element Derivatives.

Quan Manh Phung,Abhik Ghosh,Yasin Muchammad,Takeshi Yanai

doi:10.1021/jacsau.1c00417

Quan Manh Phung, Abhik Ghosh + Show 2 more

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https://doi.org/10.1021/jacsau.1c00417

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Journal: JACS Au	Publication Date: Oct 21, 2021
Citations: 12	License type: CC BY 4.0

Affiliation: Nagoya University, UiT The Arctic University of Norway

Abstract

Hybrid density functional theory (B3LYP) and density matrix renormalization group (DMRG) theory have been used to quantitatively compare the degree of ligand noninnocence (corrole radical character) in seven archetypal metallocorroles. The seven complexes, in decreasing order of corrole noninnocent character, are Mn[Cor]Cl > Fe[Cor]Cl > Fe[Cor](NO) > Mo[Cor]Cl2 > Ru[Cor](NO) ≈ Mn[Cor]Ph ≈ Fe[Cor]Ph ≈ 0, where [Cor] refers to the unsubstituted corrolato ligand. DMRG-based second-order perturbation theory calculations have also yielded detailed excited-state energetics data on the compounds, shedding light on periodic trends involving middle transition elements. Thus, whereas the ground state of Fe[Cor](NO) (S = 0) is best described as a locally S = 1/2 {FeNO}7 unit antiferromagnetically coupled to a corrole A′ radical, the calculations confirm that Ru[Cor](NO) may be described as simply {RuNO}6–Cor3–, that is, having an innocent corrole macrocycle. Furthermore, whereas the ferromagnetically coupled S = 1{FeNO}7–Cor•2– state of Fe[Cor](NO) is only ∼17.5 kcal/mol higher than the S = 0 ground state, the analogous triplet state of Ru[Cor](NO) is higher by a far larger margin (37.4 kcal/mol) relative to the ground state. In the same vein, Mo[Cor]Cl2 exhibits an adiabatic doublet-quartet gap of 36.1 kcal/mol. The large energy gaps associated with metal–ligand spin coupling in Ru[Cor](NO) and Mo[Cor]Cl2 reflect the much greater covalent character of 4d−π interactions relative to analogous interactions involving 3d orbitals. As far as excited-state energetics is concerned, DMRG-CASPT2 calculations provide moderate validation for hybrid density functional theory (B3LYP) for qualitative purposes, but underscore the possibility of large errors (>10 kcal/mol) in interstate energy differences.

Highlights

Over a half century ago, the Danish chemist C
Structural appreciation of corroles in that we do not have a comparative picture of the degree of noninnocence of different metallocorrole systems. We have addressed this knowledge gap here with a combined density functional theory (DFT) (B3LYP) and density matrix renormalization group (DMRG) study of seven archetypal middle transition metal corroles that may be reasonably expected to exhibit some degree of noninnocent character
CASPT2/CC calculations may be described as fair, even though KS-DFT is known for its inconsistent performance visa-̀ vis the spin state energetics of transition metal complexes.[106−111] B3LYP correctly predicts the ground state (GS) for all complexes, relative to DMRG-CASPT2/CC results and to experimental evidence,[6] namely, 3A′′ for Fe[Cor]Cl and Fe[Cor]Ph, 4A′′ for Mn[Cor]Cl and Mn[Cor]Ph, 1A for Fe[Cor](NO), 1A′ for Ru[Cor](NO), and 2A′ for Mo[Cor]

Summary

Introduction

Over a half century ago, the Danish chemist C. Aside from its intrinsic theoretical interest, chemists’ growing appreciation of the phenomenon has led to impressive applications in catalysis.[4,5]

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