Torsional barriers in quinolinone hydroxylamine and sulfenamide derivatives

“…19 Mp 148-149 ЊC (lit., 20 1-Hydroxyquinolin-2-one, IIIH. A procedure similar to that reported by Raban et al 22 was used. To a solution of quinoline N-oxide (1.011 g, 6.97 mmol) in benzene (60 mL) was added calcium carbonate (0.6 g, 6 mmol) and lead tetraacetate (5 g, 11.28 mmol).…”

Section: Introductionmentioning

confidence: 99%

“…Yield 35%. Mp 190-191 ЊC (lit., 22 3-Hydroxy-2-methylquinazolin-4-one, IVH. This compound was prepared in three steps starting from isatoic anhydride.…”

Section: Introductionmentioning

confidence: 99%

Quantum chemistry-based interpretations on the lowest triplet state of luminescent lanthanides complexes. Part 1. Relation between the triplet state energy of hydroxamate complexes and their luminescence properties

et al. 2004

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In this paper, we evaluate the potential use of theoretical calculations to obtain an energy scale of the lowest ligand-centred triplet excited state in luminescent terbium(III) complexes. In these complexes, non-radiative deactivation of the terbium emitting state via a back-energy transfer process (T1<--Tb(5D4)) is a common quenching process. Consequently the prediction of the energy gap between these two excited states should be useful for programming highly luminescent Tb(III) systems. We report on a strategy based upon experimental and theoretical investigations of the excited state properties of a series of four simple aromatic hydroxamate ligands coordinated to Tb(III) and Gd(III) ions. By using previously reported crystallographic data, the structural and energies properties of these systems were investigated in the ground and first excited triplet states at the density functional theory (DFT) level of calculations. Our theoretical results are consistent with a triplet excited state T1 which is localised on one ligand only and whose the energy level is independent of the lanthanide ion nature (Tb(III), Gd(III)). A good agreement between the calculated adiabatic transition energies and experimental data derived from emission spectra is obtained when a corrective term is considered. These satisfactory results are an indication that this type of modelling can lead to discriminate in terms of the position of the lowest ligand triplet energy level the best antenna among a family of chromophoric compounds. In addition this theoretical approach has provided indications that the difference between the adiabatic transition energies of all the investigated complexes can be mainly explained by metal-ligand electrostatic interactions. The influence of the number of antennae on the quantum yield and the luminescence lifetime is discussed.

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“…Notably, evidence on related compounds suggests that such systems might possess substantial rotational barriers even in the absence of peri substituents (i.e., R = H in 4 ). Raban and co-workers have shown that although the 2-quinolinone sulfenamide 6 has an enantiomerization barrier of only 16.9 kcal mol -1 , in the 4-quinolinone derivative 5 this barrier is higher than 22 kcal mol -1 . The different barrier heights of 5 and 6 were interpreted as indicating that in both cases the lower energy rotational pathway involves passage of the dinitrophenyl group near the Me (or CO) substituent (an “exo” passage).…”

Section: Introductionmentioning

confidence: 99%

Resolution and Rotational Barriers of Quinolinone and Acridone Sulfenamide Derivatives: Demonstration of the S−N Chiral Axis

et al. 2000

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Achiral (8a) and chiral (8b) N-(2,4-dinitrobenzenesulfenyl)acridone derivatives were synthesized. Addition of the chiral solvating agent (S)- 2,2,2-trifluro-1-(anthryl)ethanol to 8a rendered the enantiotopic groups on the acridone ring diastereotopic and anisochronous, thus allowing the estimation of a lower limit for the rotational barrier about the S-N bond (18.7 kcal mol(-)(1)) by NMR spectroscopy. 8b and the previously reported chiral sulfenamide 5 (Raban, M.; Martin, V. A.; Craine, L. J. Org. Chem. 1990, 55, 4311) were resolved on a Chiracel OD HPLC column. This constitutes the first resolution of stereostable enantiomers of a compound in which the chirality is due only to the presence of the S-N chiral axis. The rotational barriers of both compounds are nearly equal (22.7-22. 8 kcal mol(-)(1) at 303.7 K) and are the largest determined to date for the rotation about the S-N bond in sulfenamides. The relatively high enantiomerization barrier for 8b is remarkable since the peri positions are unsubstituted.

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Torsional barriers in quinolinone hydroxylamine and sulfenamide derivatives

Cited by 20 publications

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The chemistry of sulfenamides

The chemistry of sulfenamides

Quantum chemistry-based interpretations on the lowest triplet state of luminescent lanthanides complexes. Part 1. Relation between the triplet state energy of hydroxamate complexes and their luminescence properties

Resolution and Rotational Barriers of Quinolinone and Acridone Sulfenamide Derivatives: Demonstration of the S−N Chiral Axis

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