Circular dichroism, induced

Induced circular dichroism. Induced circular dichroism is observable for electronic transitions of an achiral molecule when, for example, it is associated in the form of a coordination complex with a chiral molecule. In the example given by Stang of a tetranuclear platinum complex where two achiral fragments are linked by two S,S)-tartrate anions (2.36) (Figure 2.59), a Cotton effect is observed for the transitions of the achiral anthracene unit. 

See also Biochemical Applications of Raman Spectroscopy Biomacromolecular Applications of Circular Dichroism and ORD Carbohydrates Studied by NMR Circularly Polarized Luminescence and Fluorescence Detected Circular Dichroism Induced Circular Dichroism Magnetic Circular Dichroism, Theory Nucleic Acids and Nucleotides Studied Using Mass Spectrometry Organometallics Studied Using Mass Spectrometry Polymer Applications of IR and Raman Spectroscopy Proteins Studied Using NMR Spectroscopy Vibrational CD Spectrometers Vibrational CD, Theory. 

Hatano, M. Induced Circular Dichroism in Biopolymer-Dye System. Vol. 77, pp. 1-121. 

Figure 14 shows the circular dichroism spectra for the LB films of p-CDNH C12-H25 including Naph-SOsNa molecules under the initial surface pressure of 30 mN/m. Different induced circular dichro-isms are clearly observed at1 Bbband of naphthalene, depending on the substituted position the negative and positive Cotton effects occur for 1 - and 2-Naph-SOaNa included in the cavity of the CD... 

Photochemically Triggered Induced Circular Dichroism in Liposomes When an optically inactive chromophore is subject to the effect of optically active environment, optical activity may be induced at the absorption wavelength of the optically inactive chromophore. This phenomenon of induced circular dichroism(ICD) is often observed in polypeptides bearing various achiral chromophores on the side chain( ). The strong chiral environment caused by the peptide helix structure is responsible for this. Distance from, and orientation to, the chiral field decide the degree of ICD appearing on the achiral chromophore. 

The first silver clusters made using DNA as template were reported by Dickson et al. in 2004 [32], The paper describes the time-dependent formation of silver clusters in a 12-base (5 -AGGTCGCCGCCC-3 ). The clusters have intense absorption in the region 400-550 nm (Fig. 2b) and emission at around 630 nm. The latter band could be decomposed as the emission bands of two distinct excitations at 540 and 580 nm, indicating the existence of two different emitters. As the clusters do not have inherent chirality, the induced circular dichroism associated with the silver cluster electronic transitions is evidence that the clusters are bound to DNA (Fig. 2c). 

Fig. 2 (a) Schematic of the formation of silver clusters using DNA oligonucleotide as scaffold. After complexation of DNA with silver cations, the mixture is reduced with NaBtL, and the fluorescent cluster is formed, (b) Absorption spectra of silver clusters acquired every 30 min using [5 -AGGTCGCCGCCC-3 ] = 10 uM. [Ag+] = 60 uM. and [BfLj-] = 60 pM. The foremost spectrum was acquired 9 min after adding the BH4, and it has at 426 nm. The inset spectrum shows the last spectmm in the series (692 min), with peaks at 424 and 520 nm. (c) Induced circular dichroism spectra. The cell path length was 5 cm. The spectra were collected 2 min (A, dashed-dotted line), 20 min (B, dotted line), 40 min (C,fine dashed line), 60 min (D, coarse dotted line), and 150 min (E, solid line) after adding the BH [32]... 

The induced circular dichroism and Cotton effect have been investigated for quaternary ammonium ions with N anchored on an asymmetric C, when hosted in calix[n]arene molecules (215, n = 4, 6, 8)430. 

A. Induced Circular Dichroism Spectropolarimetry of the Heme Group... 

The heme moiety provides de novo designed heme proteins with an intrinsic and spectroscopically rich probe. The interaction of the amide bonds of the peptide or protein with the heme macrocycle provides for an induced circular dichroism spectrum indicative of protein-cofactor interactions. The strong optical properties of the heme macrocycle also make it suitable for resonance Raman spectroscopy. Aside from the heme macrocycle, the encapsulated metal ion itself provides a spectroscopic probe into its electronic structure via EPR spectroscopy and electrochemistry. These spectroscopic and electrochemical tools provide a strong quantitative base for the detailed evaluation of the relative successes of de novo heme proteins. 

Table 1. The induced circular dichroism curves with achiral nitrosamines and chiral alcohols in isooctane.

Hie generality of the induced circular dichroism with the three nitrosamines and four alcohols (Table 1) indicates that this technique will provide a method for studying interactions of nitrosamines with biological systons such as enzymes. Hi is method furnishes a highly sensitive procedure for detecting an interaction of nitrosamines with any chiral hydrogen bonding donor. 

The absolute configuration of chiral nonracemic compounds can be established by forming a complex which can bind to the axial position of [Rh2(02CCF3)4] and thus induce circular dichroism within its electronic absorption bands. This method works well for chiral secondary alcohols and monoolefins. For these compounds tentative rules were proposed, which correlate the configuration of the starting materials with the sign of certain Cotton effects of their complexes178. 

As chiral molecules, CD hosts are one of the best chiral selectors [23]. They can also induce circular dichroism signal in an achiral guest. As shown by Zhang and Nau [24] for the complexes of p-CDwith bicyclic azaalkanes 290 or 291, this effect may allow one to determine the orientation of the latter molecule in the CD cavity. An interesting example of the influence of 11 on the guest conformation was reported by Brett and coworkers [25]. They have shown that p-amino-/ -nitrobiphenyl 292, which is planar in the solid state, becomes nonplanar in the solid state complex with 3-CD. 

The observed induced circular dichroism (ICD) is classified as follows ... 

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