Chromophore Alignment in a Chiral Host Provides a Sensitive Test for the Orientation – Intensity Rule of Induced Circular Dichroism
✍ Scribed by Xiangyang Zhang; Werner M. Nau
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 159 KB
- Volume
- 39
- Category
- Article
- ISSN
- 0044-8249
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✦ Synopsis
Circular dichroism is an essential spectral property for probing chirality. 2] An interesting effect arises when an achiral guest chromophore is complexed in a chiral host. The guest becomes optically active, a phenomenon referred to as ªinducedº circular dichroism (ICD). [3±5] The spectroscopic information resulting from this interaction is unique, since sign and magnitude of the ICD signal depend on the relative orientation of the chromophore in the host. Harata et al. have (d, 12 H; CH 3 3 d), 0.89 (d, 24 H; CH 3 135.8, 121.2, 110.3 (ArÀC 3 d), 142.3, 120.2, 110.1 (ArÀC (3 d) 2 ), 55.6 (NCH 2 3 d), 55.8 (NCH 2 (3 d) 2 ), 29.4 (CHMe 2 3 d), 26.1 (CHMe 2 3 d 3 d), 20.5 (CH 3 3 d), 20.9 (CH 3 (3d) 2 ). 3 c: Yellow crystals (m.p. 37 8C); 1 H NMR (C 6 D 6 ): d 7.18 (m, 4 H; ArÀH), 6.08 (m, 4 H; ArÀH), 4.52 (s, br, 4 H; NCH 2 ), 4.11 (s, 4 H; NCH 2 ), 0.97 (s, 18 H; C(CH 3 ) 3 ), 0.81 (s, 6 H; C(CH 3 ) 2 ); 13 C NMR (C 6 D 6 ): d 119.5 (N 2 CCN 2 ), 141.9, 141.8, 120.1, 119.4, 108.8, 105.8 (ArÀC), 58.6 (NCH 2 ), 22.4 (NCH 2 ), 36.7 (CMe 3 ), 33.6 (CMe 2 ), 29.4 (C(CH 3 ) 3 ), 25.0 (C(CH 3 ) 2 ).
5: A solution of [Mo(nor)(CO) 4 ] (300 mg, 1.0 mmol) was added dropwise to a solution of 3 c (336 mg, 0.80 mmol) in THF (30 mL) under argon. The yellow reaction solution was stirred for 12 h at ambient temperature. The solvent was removed in vacuo and the residue was dissolved in ethyl acetate (3 mL). This solution was purified by chromatography (SiO 2 , hexane/ethyl acetate 5/1) and the product solution was reduced in volume, yielding yellow crystals of 5. Yield 402 mg (80 %). 1 H NMR (CDCl 3 ): d 7. 53 ± 7.22 (m, 8 H; ArÀH), 5.55, 4.93, 4.32, 3.91 (d, 2 H; NCH 2 ), 1.10 (s, 18 H; C(CH 3 ) 3 ), 0.88 (s, 6; C(CH 3 ) 2 ); 13 C NMR (CDCl 3 ): d 219.9 (trans-CO), 210.0 (cis-CO), 208.2 (carbene-C), 136.4, 135.9, 122.6, 122.2, 113.2, 110.8 (ArÀC), 59.1, 52.4 (NCH 2 ), 41.0 (CMe 2 ), 35.0 (CMe 3 ), 29.6 (C(CH 3 ) 3 ), 24.8 (C(CH 3 ) 2 ).