Highly Strained Iron(II) Polypyridines: Exploiting the Quintet Manifold To Extend the Lifetime of MLCT Excited States

Shepard, Samuel G.; Fatur, Steven M.; Rappé, Anthony K.; Damrauer, Niels H.

doi:10.1021/jacs.5b13524

Cited by 76 publications

(94 citation statements)

References 33 publications

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“…This model is, however, not supported by the available experimental and other theoretical evidence and is therefore unlikely. This does not mean, however, that the 5 MLCT should always be discounted in every system, as discussed earlier with respect to Damrauer's work [72]. Experimental studies of the [190].…”

Section: Excited States and Liesstmentioning

confidence: 97%

“…An unconventional approach to reaching the long-lived MLCT states in Fe(II) complexes was taken by Damrauer and coworkers, who designed a highly-strained [Fe(dctpy) 2 ] 2+ complex, in which the two terpyridine ligands were substituted at 6 and 6'' positions by Cl atoms [72]. While the bulky substituents resulted in a significant decrease of the ligand field strength of the complex, stabilizing the quintet ground state, this structural change resulted in a more than 100fold increase in the lifetime of the excited 5,7 MLCT states compared to [Fe(bpy) 3 Overall, these specific examples illustrate that electronic structure calculations are most powerful when utilized in tandem with experimental studies to explain, corroborate, or predict the experimental results.…”

Section: Systematic and Joint Experimental/computational Studies Of Fmentioning

confidence: 99%

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Ironing out the photochemical and spin-crossover behavior of Fe(II) coordination compounds with computational chemistry

Ashley

Jakubı́ková

2017

Coordination Chemistry Reviews

111

117

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Effective strategies for designing Fe(II) coordination complexes with specifically tailored spinstate energetics can lead to advances in many areas of inorganic and materials chemistry. These include, but are not limited to, rational development of novel spin crossover complexes, efficient chromophores for photosensitization of dye-sensitized solar cells, and multifunctional materials.As the spin-state ordering of transition metal complexes is strongly rooted in their electronic structures, computational chemistry has naturally played an important role in assisting experimental work in this area. Unfortunately, despite many advances, accurate determination of the spin-state energetics of Fe(II) complexes still poses a remarkable challenge for virtually all applicable forms of electronic structure theory due to being controlled by a delicate balancing between correlation and exchange effects. This review focuses on some of the more notable successes and failures of modern electronic structure theory in properly describing these systems in the absence of solid-state effects. The strengths and weaknesses of using traditional wavefunction based methods and density functional theory are considered, and illustrative examples are provided to demonstrate that the modern computational chemist should make use of experimental data whenever possible and expect to utilize a combination of methods to obtain the best results. The review closes by briefly surveying some of the many interesting combined computational and experimental studies of Fe(II) chemistry that have lead to greater fundamental insight and practical understanding of this challenging class of systems.

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Section: Excited States and Liesstmentioning

confidence: 97%

Section: Systematic and Joint Experimental/computational Studies Of Fmentioning

confidence: 99%

Ironing out the photochemical and spin-crossover behavior of Fe(II) coordination compounds with computational chemistry

Ashley

Jakubı́ková

2017

Coordination Chemistry Reviews

111

117

View full text Add to dashboard Cite

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“…Both groups reported record MLCT lifetimes of 16-18 ps. Additionally, Shepard et al used steric bulk in ligand sets within bis-dihaloterpyrdine Fe(II) complexes to change the spin of the ground state and to achieve a 16-ps lifetime in the high-spin (quintet or septet) MLCT manifold [51]. Recently, Liu et al reported observing a record excited state lifetime of 26 ps for the 3 MLCT state of an Fe(II) complex [52].…”

Section: Impacted Areas Of Sciencementioning

confidence: 99%

Ultrafast Time-Resolved Hard X-Ray Emission Spectroscopy on a Tabletop

et al. 2016

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Experimental tools capable of monitoring both atomic and electronic structure on ultrafast (femtosecond to picosecond) time scales are needed for investigating photophysical processes fundamental to light harvesting, photocatalysis, energy and data storage, and optical display technologies. Time-resolved hard x-ray (>3 keV) spectroscopies have proven valuable for these measurements due to their elemental specificity and sensitivity to geometric and electronic structures. Here, we present the first tabletop apparatus capable of performing time-resolved x-ray emission spectroscopy. The time resolution of the apparatus is better than 6 ps. By combining a compact laser-driven plasma source with a highly efficient array of microcalorimeter x-ray detectors, we are able to observe photoinduced spin changes in an archetypal polypyridyl iron complex ½Feð2; 2 0 -bipyridineÞ 3 2þ and accurately measure the lifetime of the quintet spin state. Our results demonstrate that ultrafast hard x-ray emission spectroscopy is no longer confined to large facilities and now can be performed in conventional laboratories with 10 times better time resolution than at synchrotrons. Our results are enabled, in part, by a 100-to 1000-fold increase in x-ray collection efficiency compared to current techniques.

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“…In a different approach, using high-spin ground state halogen-substituted Fe(terpy) 2 complexes, it was shown that the 5 T 2 to 5,7 MLCT transition can lead to ≈16 ps excited-state lifetimes, which presents a more than 100-fold increase with respect to traditional Fe-polypyridine complexes [29].…”

Section: Introductionmentioning

confidence: 99%

NHC-Based Iron Sensitizers for DSSCs

et al. 2018

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Nanostructured dye-sensitized solar cells (DSSCs) are promising photovoltaic devices because of their low cost and transparency. Ruthenium polypyridine complexes have long been considered as lead sensitizers for DSSCs, allowing them to reach up to 11% conversion efficiency. However, ruthenium suffers from serious drawbacks potentially limiting its widespread applicability, mainly related to its potential toxicity and scarcity. This has motivated continuous research efforts to develop valuable alternatives from cheap earth-abundant metals, and among them, iron is particularly attractive. Making iron complexes applicable in DSSCs is highly challenging due to an ultrafast deactivation of the metal-ligand charge-transfer (MLCT) states into metal-centered (MC) states, leading to inefficient injection into TiO 2 . In this review, we present our latest developments in the field using Fe(II)-based photosensitizers bearing N-heterocyclic carbene (NHC) ligands, and their use in DSSCs. Special attention is paid to synthesis, photophysical, electrochemical, and computational characterization.

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Highly Strained Iron(II) Polypyridines: Exploiting the Quintet Manifold To Extend the Lifetime of MLCT Excited States

Cited by 76 publications

References 33 publications

Ironing out the photochemical and spin-crossover behavior of Fe(II) coordination compounds with computational chemistry

Ironing out the photochemical and spin-crossover behavior of Fe(II) coordination compounds with computational chemistry

Ultrafast Time-Resolved Hard X-Ray Emission Spectroscopy on a Tabletop

NHC-Based Iron Sensitizers for DSSCs

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