Electronic transitions in chromium (III) complexes—III

DeArmond, Keith; Forster, Leslie S.

doi:10.1016/0371-1951(63)80166-6

Cited by 39 publications

(11 citation statements)

References 10 publications

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“…The associated experimental oscillator strengths, f exp (eq ), are on the order of 10 –7 , in agreement with previous data reported for related Cr(III) compounds, but significantly smaller than 10 –6 found in lanthanides complexes . This is due to the double forbidden character (electric-dipole and spin) of the d–d spin-flip transitions in Cr(III), whereas the large spin–orbit coupling constant relaxes the spin limitation for 4f block cations. In eq , m is the electron mass, c is the velocity of the light in vacuum, N A is Avogrado’s number, e is the electron charge, X = ( n 2 + 2) 2 /(9 n ) is the local correction where n is the refractive index of the medium, ṽ is the wavenumber, and ε is the molar absorption coefficient.…”

Section: Resultssupporting

confidence: 88%

“…The associated experimental oscillator strengths, fexp (eq. 1), are in the order of 10 -7 , in agreement with previous data reported for related Cr(III) compounds, 53 but significantly smaller than 10 -6 found in lanthanides complexes. 54 This is due to the double forbidden character (electric-dipole and spin) of the d-d spin-flip transitions in Cr(III), whereas the large spin-orbit coupling constant relaxes the spin limitation for 4f block cations.…”

Section: Absorption and Emission Properties Of Rac-[cr(dqp)2] 3+ (1)supporting

confidence: 92%

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Chiral Molecular Ruby [Cr(dqp)₂]³⁺ with Long-Lived Circularly Polarized Luminescence

et al. 2019

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The chiral resolution of a kinetically inert molecular ruby [Cr(dqp)2] 3+ (1, dqp = 2,6-di(quinolin-8-yl)pyridine) displaying strong dual light emission at room temperature has been achieved. The wrapped arrangement of the sixmembered dqp chelating ligands around the Cr(III) provided non-planar helical conformations leading to the diastereoselective assembly of chiral bis-tridentate monometallic Cr(III)-helix. The PP-(+)-[Cr(dqp)2] 3+ and MM-(-)-[Cr(dqp)2] 3+ enantiomers could be separated and isolated by using cation-exchange chromatography and subsequent saltmetathesis with KPF6. X-Ray crystallographic analysis based on Flack parameters assigned the absolute configurations of the two enantiomers. Circularly Polarized Luminescence (CPL) spectra showed two polarized emission bands within the NIR region corresponding to the characteristic metal-centered spin-flip Cr(2 E→ 4 A2) and Cr(2 T1→ 4 A2) transitions with exceptionally high dissymmetry factors, glum, of 0.2 and 0.1, respectively, which are comparable to those reported for rareearth chiral complexes. Photophysical properties also revealed an extremely long excited-state lifetime of 1.2 ms and a high quantum yield of 5.2% at room temperature in water. These properties make [Cr(dqp)2] 3+ an ideal sensitizer for the preparation of enantiopure luminescent supramolecular energy-converting devices and also open up the possibility of using chiral Cr(III) chromophores for the construction of NIR-CPL materials and polarized photonic devices based on earthabundant metals.

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Section: Resultssupporting

confidence: 88%

Section: Absorption and Emission Properties Of Rac-[cr(dqp)2] 3+ (1)supporting

confidence: 92%

Chiral Molecular Ruby [Cr(dqp)₂]³⁺ with Long-Lived Circularly Polarized Luminescence

et al. 2019

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“…However Chatterjee and Forster [25] and De Armond and Forster [26] have measured the lifetimes and quantum yields of the phosphorescence ~Eg-~4A2g in a series of octahedral and pseudo-octahedral complexes of Cr(I I I).…”

Section: The Vibrational Factor Fk(mr Ns)mentioning

confidence: 98%

“…To estimate the degeneracy factor d we follow Ross et al We have applied the theory to two series of Cr(III) compounds : (i) O h or pseudo-O h complexes with nitrogen or oxygen donor ligands [25] (ii) some /3-diketone complexes [26].…”

Section: The Vibrational Factor Fk(mr Ns)mentioning

confidence: 99%

Radiationless processes in transition-metal complexes

Robbins¹,

Thomson

1973

Molecular Physics

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This work applies recent theories of radiationless relaxation processes to the case of transition-metal complexes. Existing theories developed for understanding radiationless transitions in organic molecules separate coupling terms into electronic and vibrational factors. In this work the symmetry based selection rules on the coupling terms are examined since the high symmetry of many transition-metal complexes offers the possibility that strict selection rules will operate. First, the theoretical expressions have been extended to include the spin-orbit coupling operator in the zeroth order hamiltonian. This then allows application of the final expressions to transition metal ions of any atomic number and also permits derivation of selection rules for relaxation processes between spinor states. Secondly, the application of the vibrational factor, which is a product of a promoting term and an overlap factor or accepting term, to a series of octahedral and pseudooctahedral Cr(I I I) complexes, studied by Forster and co-workers, is described. It is shown that there is a good linear correlation between the radiationless transition rate ~Er and the number of active hydrogen atoms on the ligands. It is concluded that the highest frequency internal ligand modes are acting as promoting modes. This can be understood by examination of the selection rules on the electronic factors which show that, for the 2Eg~4A~g process in Cr(III), there are no vibrations of the metal-ligand framework likely to be efficient as promoting modes. Finally, the selection rules are given for the electronic coupling factors between the lowest excited and ground states of all the d configurations of both tetrahedral and octahedral complexes of the first row of transition metal ions. A comparison of these rules with available experimental data shows there is some correlation between the occurrence of emission and the absence of a promoting mode among the skeletal vibrations of the complex considered.

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“…The Figure 1 energy level diagram was used in 1964 and the need for evaluation of at least some of the rate constants was recognized (DeArmond and Forster, 1964). With the advent of commercially available instruments, viz., triggered oscilloscopes and fast analog-digital converters, recording emission lifetimes in the millisecond-microsecond range became routine.…”

mentioning

confidence: 99%

Chromium Photophysics – A Prototypical Case History

Forster

2006

Found Chem

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Science, in general, and chemistry in particular advances by methods that are difficult to codify. The availability of theories (models) and instrumentation play an important role but indefinable motivations to study individual phenomena are also involved. The area of chromium photophysics has a rich history that spans 150 years. A case history of the progression from the natural history stage to its present state reveals the way in which several factors that are common to much physical science research interact.KEY WORDS: phosphorscence, intermolecular rates, emission lifetimes, models in physical chemistry Both the history and philosophy of science tend to emphasize the major discoveries and conceptual developments. These constitute only a small fraction of the scientific enterprise. In particular, emphasis on ''grand science'' does not necessarily give an accurate description of the way in which the less spectacular scientific work actually proceeds. One thing is clearfew working scientists are concerned with the philosophical aspects of their work. They are generally very pragmatic and function intuitively. The case histories approach is a useful way to illuminate the essence of scientific research. Since scientific activities vary among the natural sciences, in general, and the physical sciences in particular, a single case history cannot illuminate their full range. But such a history can point to factors that have been involved in at least one area. Most scientific work is prosaic and a description of a mundane aspect of physical science can reveal much about the progression of an area from its crude beginnings to a mature phase.

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Electronic transitions in chromium (III) complexes—III

Cited by 39 publications

References 10 publications

Chiral Molecular Ruby [Cr(dqp)₂]³⁺ with Long-Lived Circularly Polarized Luminescence

Chiral Molecular Ruby [Cr(dqp)₂]³⁺ with Long-Lived Circularly Polarized Luminescence

Radiationless processes in transition-metal complexes

Chromium Photophysics – A Prototypical Case History

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Electronic transitions in chromium (III) complexes—III

Cited by 39 publications

References 10 publications

Chiral Molecular Ruby [Cr(dqp)2]3+ with Long-Lived Circularly Polarized Luminescence

Chiral Molecular Ruby [Cr(dqp)2]3+ with Long-Lived Circularly Polarized Luminescence

Radiationless processes in transition-metal complexes

Chromium Photophysics – A Prototypical Case History

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Product

Resources

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Chiral Molecular Ruby [Cr(dqp)₂]³⁺ with Long-Lived Circularly Polarized Luminescence

Chiral Molecular Ruby [Cr(dqp)₂]³⁺ with Long-Lived Circularly Polarized Luminescence