Distinct photodynamics of κ-N and κ-C pseudoisomeric iron(<scp>ii</scp>) complexes

Dierks, Philipp; Kruse, Ayla; Bokareva, Olga S.; Al–Marri, Mohammed J.; Kalmbach, Jens; Baltrun, Marc; Neuba, Adam; Schoch, Roland; Hohloch, Stephan; Heinze, Katja; Seitz, Michael; Kühn, Oliver; Lochbrunner, Stefan

doi:10.1039/d1cc01716k

Cited by 28 publications

(19 citation statements)

References 26 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…[41,42] Mesoionic carbene coordinating ligands were also shown to prevent LIEEST and to stabilize the 3 MLCT state in the range of � 10 ps. [43] A fully hexa-NHC coordinated Fe complex Fe(btz) 3 was synthesized by the Lund group with bidentate mesoionic triazoleÀ phenyl ligands (family D). Such mesoionic ligands have, in addition to the increased σ donation, a decreased π acceptance, which destabilizes the occupied "t 2g " HOMO levels and leads to a red-shifted absorption spectrum.…”

Section: Design Approaches and Best Performances -A Short Overviewmentioning

confidence: 99%

See 1 more Smart Citation

Ultrafast Spectroscopy of Fe(II) Complexes Designed for Solar‐Energy Conversion: Current Status and Open Questions

et al. 2022

View full text Add to dashboard Cite

One major challenge of future sustainable photochemistry is to replace precious and rare transition metals in applications such as energy conversion or electroluminescence by earth‐abundant, cheap, and recyclable materials. This involves using coordination complexes of first row transition metals such as Cu, Cr, or Mn. In the case of iron, which is attractive due to its natural abundance, fundamental limitations imposed by the small ligand field splitting energy have recently been overcome. In this review article, we briefly summarize the present knowledge and understanding of the structure‐property relationships of Fe(II) and Fe(III) complexes with excited state lifetimes in the nanosecond range. However, our main focus is to examine to which extent the ultrafast spectroscopy methods used so far provided insight into the excited state structure and the photo‐induced dynamics of these complexes. Driven by the main question of how to spectroscopically, i. e. in energy and concentration, differentiate the population of ligand‐ vs. metal‐centered states, the hitherto less exploited ultrafast vibrational spectroscopy is suggested to provide valuable complementary insights.

show abstract

Section: Design Approaches and Best Performances -A Short Overviewmentioning

confidence: 99%

“…Mesoionic carbene coordinating ligands were also shown to prevent LIEEST and to stabilize the 3 MLCT state in the range of ≈10 ps [43] . A fully hexa‐NHC coordinated Fe complex Fe(btz) 3 was synthesized by the Lund group with bidentate mesoionic triazole−phenyl ligands (family D).…”

Section: Background and Recent Achievementsmentioning

confidence: 99%

Ultrafast Spectroscopy of Fe(II) Complexes Designed for Solar‐Energy Conversion: Current Status and Open Questions

et al. 2022

View full text Add to dashboard Cite

show abstract

“…Most prominently, this occurs in Fe II complexes where efficient relaxation via low-energy MC states had precluded long MLCT lifetimes and phosphorescence for a long time [12][13][14][15][16][17][18][19][20]. An octahedral Fe II complex with tridentate N^N^N ligands showed a 3/5 MC lifetime of >1.6 ns and sensitized 1 O 2 [15] and an iron(II) complex with a hexadentate tren(py) 3 ligand reduces quinones by photoinduced electron transfer from its 5 MC state (tren(py) 3 = tris(2-pyridyl-methyliminoethyl)amine) [18]. An excited 3 CT state lifetime of 3 ns was achieved by an iron(II) complex with strongly covalent Fe-N amido bonds due to a high barrier for the 3 MC/ 3 CT interconversion [21].…”

Section: Introduction and Scope Of The Reviewmentioning

confidence: 99%

Spin-flip luminescence

Kitzmann

Moll

Heinze

2022

Photochem Photobiol Sci

Self Cite

149

View full text Add to dashboard Cite

In molecular photochemistry, charge-transfer emission is well understood and widely exploited. In contrast, luminescent metal-centered transitions only came into focus in recent years. This gave rise to strongly phosphorescent CrIII complexes with a d3 electronic configuration featuring luminescent metal-centered excited states which are characterized by the flip of a single spin. These so-called spin-flip emitters possess unique properties and require different design strategies than traditional charge-transfer phosphors. In this review, we give a brief introduction to ligand field theory as a framework to understand this phenomenon and outline prerequisites for efficient spin-flip emission including ligand field strength, symmetry, intersystem crossing and common deactivation pathways using CrIII complexes as instructive examples. The recent progress and associated challenges of tuning the energies of emissive excited states and of emerging applications of the unique photophysical properties of spin-flip emitters are discussed. Finally, we summarize the current state-of-the-art and challenges of spin-flip emitters beyond CrIII with d2, d3, d4 and d8 electronic configuration, where we mainly cover pseudooctahedral molecular complexes of V, Mo, W, Mn, Re and Ni, and highlight possible future research opportunities. Graphical abstract

show abstract

“…However, this is often contaminated by a second [Fe(L 3 ) 2 ] 2+ -containing product, which was crystallographically characterized but whose exact composition is uncertain (Figure S25). All three forms of 5[ClO 4 ] 2 contain low-spin [Fe(L 3 ) 2 ] 2+ cations at 120 K (Tables and S13), which is consistent with most other compounds of the [Fe(b3tp R ) 2 ] 2+ type. − The L 3 ligand binds exclusively as its di(1 H -1,2,3-triazol-4-yl)pyridine tautomer (Chart ), with extensive hydrogen bonding between the cations, anions, and solvent in the lattice.…”

Section: Resultsmentioning

confidence: 99%

“…The related 2,6-di(1,2,3-triazolyl)pyridine (b3tp R , R ≠ H; Chart ) ligands are easily prepared by Click chemistry and are being increasingly employed as metal-binding domains in supramolecular architectures and soft materials . Only a handful of [Fe(b3tp R ) 2 ] 2+ complex derivatives have been reported to date, however, and are mostly low-spin in solution and the solid state. − In contrast, isomeric [Fe(b4tp R ) 2 ] 2+ (R = H or Me) complexes are high-spin, with the onset of SCO being detected in one solid complex salt at very low temperature. − This is a much wider range of spin-state properties than that observed between analogous [Fe(1-bpp) 2 ] 2+ and [Fe(3-bpp) 2 ] 2+ derivatives under similar conditions …”

Section: Introductionmentioning

confidence: 99%

Structures and Spin States of Iron(II) Complexes of Isomeric 2,6-Di(1,2,3-triazolyl)pyridine Ligands

et al. 2021

View full text Add to dashboard Cite

Iron(II) complex salts of 2,6-di(1,2,3-triazol-1-yl)pyridine (L1) are unexpectedly unstable in undried solvent. This is explained by the isolation of [Fe(L1)4(H2O)2][ClO4]2 and [Fe(NCS)2(L1)2(H2O)2]·L1, containing L1 bound as a monodentate ligand rather than in the expected tridentate fashion. These complexes associate into 44 grid structures through O–H···N hydrogen bonding; a solvate of a related 44 coordination framework, catena-[Cu(μ-L1)2(H2O)2][BF4]2, is also presented. The isomeric ligands 2,6-di(1,2,3-triazol-2-yl)pyridine (L2) and 2,6-di(1H-1,2,3-triazol-4-yl)pyridine (L3) bind to iron(II) in a more typical tridentate fashion. Solvates of [Fe(L3)2][ClO4]2 are low-spin and diamagnetic in the solid state and in solution, while [Fe(L2)2][ClO4]2 and [Co(L3)2][BF4]2 are fully high-spin. Treatment of L3 with methyl iodide affords 2,6-di(2-methyl-1,2,3-triazol-4-yl)pyridine (L4) and 2-(1-methyl-1,2,3-triazol-4-yl)-6-(2-methyl-1,2,3-triazol-4-yl)pyridine (L5). While salts of [Fe(L5)2]2+ are low-spin in the solid state, [Fe(L4)2][ClO4]2·H2O is high-spin, and [Fe(L4)2][ClO4]2·3MeNO2 exhibits a hysteretic spin transition to 50% completeness at T 1/2 = 128 K (ΔT 1/2 = 6 K). This transition proceeds via a symmetry-breaking phase transition to an unusual low-temperature phase containing three unique cation sites with high-spin, low-spin, and 1:1 mixed-spin populations. The unusual distribution of the spin states in the low-temperature phase reflects “spin-state frustration” of the mixed-spin cation site by an equal number of high-spin and low-spin nearest neighbors. Gas-phase density functional theory calculations reproduce the spin-state preferences of these and some related complexes. These highlight the interplay between the σ-basicity and π-acidity of the heterocyclic donors in this ligand type, which have opposing influences on the molecular ligand field. The Brønsted basicities of L1–L3 are very sensitive to the linkage isomerism of their triazolyl donors, which explains why their iron complex spin states show more variation than the better-known iron(II)/2,6-dipyrazolylpyridine system.

show abstract

Distinct photodynamics of κ-N and κ-C pseudoisomeric iron(ii) complexes

Abstract: The photodynamics of two pseudoisomeric iron(ii) complexes reveal insights into reactive metal-centred states and hot branching dynamics. A new type of reactivity by triplet energy transfer from MC states enables oxygen sensitization activity.

Cited by 28 publications

References 26 publications

Ultrafast Spectroscopy of Fe(II) Complexes Designed for Solar‐Energy Conversion: Current Status and Open Questions

Ultrafast Spectroscopy of Fe(II) Complexes Designed for Solar‐Energy Conversion: Current Status and Open Questions

Spin-flip luminescence

Structures and Spin States of Iron(II) Complexes of Isomeric 2,6-Di(1,2,3-triazolyl)pyridine Ligands

Contact Info

Product

Resources

About