Synthesis and Characterization of Bidentate Isonitrile Iron Complexes

Till, Marion; Kelly, John A.; Ziegler, Christoph G. P.; Wolf, Robert; Guo, Tianao; Ringenberg, Mark R.; Lutsker, Eugen; Reiser, Oliver

doi:10.1021/acs.organomet.1c00042

Cited by 6 publications

(8 citation statements)

References 75 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The C≡N stretching vibration in the solid-state IR spectrum of L pyr is located at 2112 cm –1 (Figure S11), and upon coordination to Cr 0 in [Cr(L pyr ) 3 ] it shifts to 1950 cm –1 . This is a manifestation of π-backbonding from the zerovalent metal center to the π* antibonding orbital of the isocyanide moiety, − and similar C≡N stretch frequencies have been reported for L H and [Cr(L H ) 3 ], respectively . Upon complexation of L pyr to chromium(0), a strong absorbance appears in the IR spectrum at 590 cm –1 , and this band is attributable to the Cr–C stretching vibration.…”

Section: Resultssupporting

confidence: 60%

Pyrene-Decoration of a Chromium(0) Tris(diisocyanide) Enhances Excited State Delocalization: A Strategy to Improve the Photoluminescence of 3d⁶ Metal Complexes

2021

View full text Add to dashboard Cite

There is a long-standing interest in iron(II) complexes that emit from metal-to-ligand charge transfer (MLCT) excited states, analogous to ruthenium(II) polypyridines. The 3d6 electrons of iron(II) are exposed to a relatively weak ligand field, rendering nonradiative relaxation of MLCT states via metal-centered excited states undesirably efficient. For isoelectronic chromium(0), chelating diisocyanide ligands recently provided access to very weak MLCT emission in solution at room temperature. Here, we present a concept that boosts the luminescence quantum yield of a chromium(0) isocyanide complex by nearly 2 orders of magnitude, accompanied by a significant increase of the MLCT lifetime. Pyrene units in the diisocyanide ligand backbone lead to an enlarged π-conjugation system and to a strongly delocalized MLCT state, from which nonradiative relaxation is less dominant despite a sizable redshift of the emission. While the pyrene moiety is electronically coupled to the core of the chromium(0) complex in the excited state, UV–vis absorption and 2D NMR spectroscopy show that this is not the case in the ground state. Luminescence lifetimes and quantum yields for our pyrenyl-decorated chromium(0) complex exhibit an unusual bell-shaped dependence on solvent polarity, indicative of two counteracting effects governing the MLCT deactivation. These two effects are identified as predominant deactivation either through an energetically nearby lying metal-centered state in the most apolar solvents, or alternatively via direct nonradiative relaxation to the ground state following the energy gap law in more polar solvents. This is the first example of a 3d6 MLCT emitter to benefit from an increased π-conjugation network.

show abstract

Section: Resultssupporting

confidence: 60%

Pyrene-Decoration of a Chromium(0) Tris(diisocyanide) Enhances Excited State Delocalization: A Strategy to Improve the Photoluminescence of 3d⁶ Metal Complexes

2021

View full text Add to dashboard Cite

show abstract

“…The CN stretching bands of [FeCl 2 ] and [Fe](PF 6 ) 2 are found at higher frequencies than L Pyr , namely at 2125 and 2159 cm –1 , respectively. Similar CN stretching frequencies have previously been reported for related manganese(I) and iron(II) isocyanide complexes. ,,, This change in the CN stretching frequencies is well reflected by the quantum chemical simulations performed for [Cr], [Mn] + , and [Fe] 2+ . Density functional theory (DFT) predicts the three strongly IR-active and almost degenerate CN stretching modes at 1942, 2050, and 2147 cm –1 for [Cr], [Mn] + and [Fe] 2+ (Table S15), respectively.…”

Section: Resultsmentioning

confidence: 99%

Controlling the Photophysical Properties of a Series of Isostructural d⁶ Complexes Based on Cr⁰, Mn^I, and Fe^II

Wegeberg,

Häussinger,

Kupfer

et al. 2024

J. Am. Chem. Soc.

View full text Add to dashboard Cite

Development of first-row transition metal complexes with similar luminescence and photoredox properties as widely used RuII polypyridines is attractive because metals from the first transition series are comparatively abundant and inexpensive. The weaker ligand field experienced by the valence d-electrons of first-row transition metals challenges the installation of the same types of metal-to-ligand charge transfer (MLCT) excited states as in precious metal complexes, due to rapid population of energetically lower-lying metal-centered (MC) states. In a family of isostructural tris(diisocyanide) complexes of the 3d6 metals Cr0, MnI, and FeII, the increasing effective nuclear charge and ligand field strength allow us to control the energetic order between the 3MLCT and 3MC states, whereas pyrene decoration of the isocyanide ligand framework provides control over intraligand (ILPyr) states. The chromium(0) complex shows red 3MLCT phosphorescence because all other excited states are higher in energy. In the manganese(I) complex, a microsecond-lived dark 3ILPyr state, reminiscent of the types of electronic states encountered in many polyaromatic hydrocarbon compounds, is the lowest and becomes photoactive. In the iron(II) complex, the lowest MLCT state has shifted to so much higher energy that 1ILPyr fluorescence occurs, in parallel to other excited-state deactivation pathways. Our combined synthetic-spectroscopic-theoretical study provides unprecedented insights into how effective nuclear charge, ligand field strength, and ligand π-conjugation affect the energetic order between MLCT and ligand-based excited states, and under what circumstances these individual states become luminescent and exploitable in photochemistry. Such insights are the key to further developments of luminescent and photoredox-active first-row transition metal complexes.

show abstract

“…While isonitrile is a potent and a common ligand to iron 36 – 39 , coordination of isonitrile to the iron in the active site inactivates PIsnB as demonstrated by Mössbauer spectroscopy previously 40 . The substrate-bound structure reveals how PIsnB prevents isonitrile chelation to the iron while maintaining catalytic efficiency.…”

Section: Resultsmentioning

confidence: 99%

Elucidation of divergent desaturation pathways in the formation of vinyl isonitrile and isocyanoacrylate

et al. 2022

View full text Add to dashboard Cite

Two different types of desaturations are employed by iron- and 2-oxoglutarate-dependent (Fe/2OG) enzymes to construct vinyl isonitrile and isocyanoacrylate moieties found in isonitrile-containing natural products. A substrate-bound protein structure reveals a plausible strategy to affect desaturation and hints at substrate promiscuity of these enzymes. Analogs are synthesized and used as mechanistic probes to validate structural observations. Instead of proceeding through hydroxylated intermediate as previously proposed, a plausible carbocation species is utilized to trigger C=C bond installation. These Fe/2OG enzymes can also accommodate analogs with opposite chirality and different functional groups including isonitrile-(D)-tyrosine, N-formyl tyrosine, and phloretic acid, while maintaining the reaction selectivity.

show abstract

Synthesis and Characterization of Bidentate Isonitrile Iron Complexes

Cited by 6 publications

References 75 publications

Pyrene-Decoration of a Chromium(0) Tris(diisocyanide) Enhances Excited State Delocalization: A Strategy to Improve the Photoluminescence of 3d⁶ Metal Complexes

Pyrene-Decoration of a Chromium(0) Tris(diisocyanide) Enhances Excited State Delocalization: A Strategy to Improve the Photoluminescence of 3d⁶ Metal Complexes

Controlling the Photophysical Properties of a Series of Isostructural d⁶ Complexes Based on Cr⁰, Mn^I, and Fe^II

Elucidation of divergent desaturation pathways in the formation of vinyl isonitrile and isocyanoacrylate

Contact Info

Product

Resources

About

Synthesis and Characterization of Bidentate Isonitrile Iron Complexes

Cited by 6 publications

References 75 publications

Pyrene-Decoration of a Chromium(0) Tris(diisocyanide) Enhances Excited State Delocalization: A Strategy to Improve the Photoluminescence of 3d6 Metal Complexes

Pyrene-Decoration of a Chromium(0) Tris(diisocyanide) Enhances Excited State Delocalization: A Strategy to Improve the Photoluminescence of 3d6 Metal Complexes

Controlling the Photophysical Properties of a Series of Isostructural d6 Complexes Based on Cr0, MnI, and FeII

Elucidation of divergent desaturation pathways in the formation of vinyl isonitrile and isocyanoacrylate

Contact Info

Product

Resources

About

Pyrene-Decoration of a Chromium(0) Tris(diisocyanide) Enhances Excited State Delocalization: A Strategy to Improve the Photoluminescence of 3d⁶ Metal Complexes

Pyrene-Decoration of a Chromium(0) Tris(diisocyanide) Enhances Excited State Delocalization: A Strategy to Improve the Photoluminescence of 3d⁶ Metal Complexes

Controlling the Photophysical Properties of a Series of Isostructural d⁶ Complexes Based on Cr⁰, Mn^I, and Fe^II