Synthesis, Characterization, and Photobehavior of .DELTA.- and .LAMBDA.-fac-Tris((S)-tryptophanato)chromium(III)

Photochemistry and Photophysics of Chromium(III) Complexes

“…It was argued that such a transition state was supported by angular overlap molecular orbital studies of Burdett. 26 A recent investigation 132 of Λand ∆-fac-Cr(S-tryp) 3 has been interpreted as providing strong evidence for such a photoinduced Bailar twist. On ligand-field excitation at 488 nm, the ∆-fac isomer is essentially photoinert while the Λ-fac isomer undergoes complete conversion to ∆-fac with a quantum yield of 0.03.…”

Separation of Isomers and Mechanisms of Inversion of Stereochemistry of Group 9 d6 Tris-Chelate Complexes of Hinokitiol

“…The normalized bite, the ratio of the distance between the chelating atoms, and the metal–ligand bond length allow predictions of the preferred mechanism. The Bailar twist is preferred when the normalized bite ratio is less than 1.5. − On the basis of DFT calculations, the normalized bite of Co­(hino) 3 is 1.33. On the basis of the crystal structure, the normalized bite of Rh­(hino) 3 is 1.30.…”

Quantitative 2D EXSY and Dynamic19F-NMR Studies of the Dynamic Behaviour of the Bidentate Chelate Complex Ga(fox)3 (fox = 5-fluoro-8-hydroxyquinoline)

“…We can see that the metalnitrogen b bonds are the shortest in relation with the b site, which ''sees'' no change in the Bailar-type process. More precisely, as discussed in several papers, [4,7] the pertinent parameter for these studies is the bite size (also called the normalised bite), defined as the ratio of the distance between the donor atoms of the chelate ring divided by the metal-donor atom distance. When this value is less than 1.5, the Bailar twist is energetically preferred over a Rây-Dutt twist.…”

“…When this value is less than 1.5, the Bailar twist is energetically preferred over a Rây-Dutt twist. [4,7] From literature data in Table 3, this bite value is included in 1.244 to 1.384 values for the gallium complex and 1.212 and 1.360 for the iron one. These values are calculated as: the higher ratio for gallium (1.384) was obtained as the ratio of the highest distance between the donor atoms (265.8 pm) divided by the smallest metal-donor atom distance (192.1 pm); the lowest ratio (1.244) was obtained as the ratio of the shortest distance between the donor atoms (263.3 pm) divided by the largest metal-donor atom distance (211.6 pm), and the same for the iron case.…”

“…Several examples in the literature show that NMR spectroscopy is well adapted for kinetic measurements of such molecular rearrangements in complexes of appropriate metal cations: [1] chromium(III) complexes with the unsymmetrical bidentate (S)-tryptophan ( 1 H NMR), [7] ruthenium hydrides with triphenylphosphanes as other ligands ( 31 P NMR) [8] and several tris(unsymmetrical bidentate ligand)-metal(III) complexes of group 13 metals such as tris(trifluoroacetylacetonato)-Ga(III) complexes ( 19 F NMR), [9] tris-(substituted-tropolonato)metal(III) complexes ( 1 H NMR), [10] tris [2-(2'-hydroxyphenyl [12] tris(substituted-catecholato)metal(III) complexes ( 1 H NMR). [13] Previously, we studied a new tripodal iron chelator, OTrensox, based on 8-hydroxyquinoline.…”