Pyridinium Complexes. I. The Significance of the Second Charge-Transfer Band of Pyridinium Iodides

Kosower, Edward M.; Skorcz, Joseph A.; Schwarz, William M.; Patton, James W.

doi:10.1021/ja01494a025

Cited by 100 publications

(27 citation statements)

References 3 publications

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“…However, the CF 3 QI 3 CT is well below the Qs 3 π-π* state and thus a single exponent decay from 3 CT is observed. The results are consistent with a previous report by Kosower et al, 21 where the presence of multiple chargetransfer bands for pyridinium iodide is observed. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 10 To further understand the structure-photoluminescence properties relationship in the crystalline state, single-crystal X-ray Diffraction (SC-XRD) measurements were performed for all the carbazole and Qs compounds.…”

Section: Resultssupporting

confidence: 94%

External Heavy-Atom Effect via Orbital Interactions Revealed by Single-Crystal X-ray Diffraction

Sun¹,

Zhang²,

Li³

et al. 2016

J. Phys. Chem. A

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Enhanced spin-orbit coupling through external heavy-atom effect (EHE) has been routinely used to induce room-temperature phosphorescence (RTP) for purely organic molecular materials. Therefore, understanding the nature of EHE, i.e., the specific orbital interactions between the external heavy atom and the luminophore, is of essential importance in molecular design. For organic systems, halogens (e.g., Cl, Br, and I) are the most commonly seen heavy atoms serving to realize the EHE-related RTP. In this report, we conduct an investigation on how heavy-atom perturbers and aromatic luminophores interact on the basis of data obtained from crystallography. We synthesized two classes of molecular systems including N-haloalkyl-substituted carbazoles and quinolinium halides, where the luminescent molecules are considered as "base" or "acid" relative to the heavy-atom perturbers, respectively. We propose that electron donation from a π molecular orbital (MO) of the carbazole to the σ* MO of the C-X bond (π/σ*) and n electron donation to a π* MO of the quinolinium moiety (n/π*) are responsible for the EHE (RTP) in the solid state, respectively.

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Section: Resultssupporting

confidence: 94%

External Heavy-Atom Effect via Orbital Interactions Revealed by Single-Crystal X-ray Diffraction

Sun¹,

Zhang²,

Li³

et al. 2016

J. Phys. Chem. A

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“…An extra new band'with lower intensity is observed in the electronic spectra of compound I11 (Ar = C,H,OH(p)) at 490 nm. This band may be assigned to an intermolecular charge transfer transition (7,9,(10)(11)(12). Such an assignment is supported by the non-linear relationship obtained on plotting the absorbance of this band against the molar concentration of the compound.…”

Section: Resultsmentioning

confidence: 99%

Synthesis, electronic spectra, and solvatochromic behaviour of 4-arylidene-1-(2,4-dinitrophenyl)-3-methyl-2-pyrazolin-5-ones

Ibrahim¹,

Youssef²

1984

Can. J. Chem.

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“…Iodide is known to form adducts with aromatic acceptors (41)(42)(43)(44), and previously published crystal structures of ½RuðbpyÞ 2 ðdeebÞðIÞ 2 and ½RuðdeebÞ 3 ðIÞ 2 revealed that iodide was within 4 Å of the nearest carbon atom on the deeb ligands, whereas the Ru-I distance was determined to be approximately 6 Å (1,14). Direct coordination of iodide to ruthenium to form a seven-coordinate compound also cannot be ruled out; however, to our knowledge there is no precedence for such behavior with Ru-tris(diimine) compounds.…”

Section: δG°¼ E°ðimentioning

confidence: 99%

Visible light generation of I–I bonds by Ru-tris(diimine) excited states

Farnum

Jou

Meyer

2012

Proc. Natl. Acad. Sci. U.S.A.

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Seven Ru-tris(diimine) compounds were prepared to study the photooxidation of iodide. Iodide oxidation results in the formation of I-I bonds, and it is therefore relevant to the conversion and storage of solar energy. Iodide oxidation is also a key step for electrical power generation in dye-sensitized solar cells. The mechanistic details of iodide oxidation and I-I bond formation were elucidated through time-resolved spectroscopic measurements. Bimolecular electron-transfer reactions between Ru-tris(diimine) excited states and iodide first yielded the iodine atom that subsequently reacted with excess I − to yield the I-I bond of diiodide (I 2•− ). An important finding was that excited-state iodide oxidation was rapid (k > 10 9 M −1 s −1 ) even for thermodynamically uphill reactions. These results indicated that iodide oxidation to the iodine atom may account for a significant fraction of sensitizer regeneration within dye-sensitized solar cells. •− ) and triiodide (I 3 − ) (1-6). Photoinitiation of iodide oxidation with visible light thus provides a fundamental means by which solar photons can be converted to chemical energy in the form of I-I bonds. This bond formation chemistry is also of major importance in dye-sensitized solar cells where I − /I 3 − is the most widely used redox mediator (7-11). We have previously reported the photooxidation of iodide using Ru-tris(diimine) compounds in fluid solution (1,2,(12)(13)(14). These compounds are known for their exceptional absorption properties in the visible region, and their long-lived metal-toligand charge transfer (MLCT) excited states (15, 16). Visible light generation of Ru-tris(diimine) excited states in the presence of I − resulted in electron-transfer reactions that generated I-I bonds. In acetonitrile solutions, iodide oxidation proceeded through an iodine atom intermediate, and I 2•− appeared as a secondary reaction product (1, 2, 13). In dichloromethane solutions, iodide oxidation was greatly enhanced due to strong ion-pair interactions between the Ru-tris(diimine) compounds and iodide (1,12,14).A series of Ru-tris(diimine) photooxidants have been prepared to characterize photo-initiated I-I bond formation in acetonitrile. The diimine ligands employed in this study are shown in Fig. 1, where a vertical arrow is drawn to indicate increased electron donation of the chelating nitrogens to the ruthenium metal center. The compounds prepared allowed the free-energy change for electron transfer (ΔG°) to be systematically varied over a 400-meV range. A strong dependence of the observed rate constants for iodide oxidation on ΔG°was apparent and rate constants on the order of 10 9 M −1 s −1 were determined for ΔG°≥ 0 eV. ResultsThe series of Ru-tris(diimine) compounds was synthesized following literature procedures and are hereby referred to as Ru 2þ . To our knowledge, ½RuðdmbÞ 2 ðbpzÞðPF 6 Þ 2 and ½RuðbpmÞ 2 ðdeebÞðPF 6 Þ 2 are compounds that have not been previously reported. The photophysical properties for all other compounds have been well characterized i...

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Pyridinium Complexes. I. The Significance of the Second Charge-Transfer Band of Pyridinium Iodides

Cited by 100 publications

References 3 publications

External Heavy-Atom Effect via Orbital Interactions Revealed by Single-Crystal X-ray Diffraction

External Heavy-Atom Effect via Orbital Interactions Revealed by Single-Crystal X-ray Diffraction

Synthesis, electronic spectra, and solvatochromic behaviour of 4-arylidene-1-(2,4-dinitrophenyl)-3-methyl-2-pyrazolin-5-ones

Visible light generation of I–I bonds by Ru-tris(diimine) excited states

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