Miwako Higashi

Induced circular dichroism spectra of α-, β- and γ-cyclodextrin complexes with sodium 4′-hydroxy-3′-isopropylazobenzene-4-sulfonate and sodium 4′-hydroxy-3′,5′-diisopropylazobenzene-4-sulfonate

The induced circular dichroism (ICD) spectra of α-, β- and γ-cyclodextrin complexes with sodium 4′-hydroxy-3′-isopropylazobenzene-4-sulfonate, 3-Pri(4-OH)C6H3–NN–C6H4SO3–Na+5 and sodium 4′-hydroxy-3′,5′-diisopropylazobenzene-4-sulfonate, 3,5-(Pri)2(4-OH)C6H2–NN–C6H4SO3–Na+8 in aqueous solution have been measured. ICD is observed on the absorption bands of the achiral azo guest molecules 5 and 8 which are included in the dissymmetric field of the chiral cyclodextrin (CD) cavity. The ICD spectral patterns change drastically depending on the shape and size of the alkyl substituents (Ri and Rj) of the phenol moiety [RiRj(4-OH)C6H2–] of the azo guest molecules, RiRj(4-OH)C6H2–NN–C6H4SO3–Na+. The π→π* electronic transitions which are polarized along the long axis of the slim guest molecule 5 show almost a single positive ICD in all of the α-, β- and γ-CD inclusion complexes. This result indicates that the guest 5 is included from the long-axis side into the CD cavity. However, the ICD spectra of the β- and γ-CD complexes of the bulky guest molecule 8 show a split-type positive and negative ICD signal in the π→π* transition band. This splitting pattern may arise from the dimer formation of 8 in the form of the 2:2 (guest:CD)β- and γ-CD inclusion complexes.

Electronic spectra of carbazole, dibenzofuran and dibenzothiophene

Abstract The magnetic circular dichroism and electronic absorption spectra of carbazole, dibenzofuran and dibenzothiophene have been measured. The absorption bands of these compounds are interpreted by using these observed spectra and the results of molecular-orbital calculations.

Induced circular dichroism spectra of the cyclodextrin complexes with 2-Thioxo-1,3-benzodithiole and 2-Selenoxo-1,3-benzodithiole

The induced circular dichroism (ICD) spectra of β-cyclodextrin (β-CD) complexes with 2-thioxo-1,3-benzodithiole and 2-selenoxo-1,3-benzodithiole have been measured. From the signs of the ICD spectra of both complexes, the polarization directions for the excited states have been investigated.

Induced circular dichroism spectra of α-, β-, and γ-cyclodextrin complexes with π-conjugate compounds. Part 2. Chiral dimer formation and polarization directions of the π–π* transitions in some hydroxyazo guests having a naphthalene nucleus†

The absorption and circular dichroism spectra of some o- and p-hydroxyazo compounds having a naphthalene nucleus in the presence of α-, β-, and γ-cyclodextrin (CDx) have been measured in the wavelength region of 200–600 nm. The induced circular dichroism (ICD) is observed on the absorption bands of the π–π* transitions of the azo chromophore and the naphthalene moiety. The signs in the observed ICD spectra are discussed in terms of the orientation of the transition moment of the π–π* states to the axis of the CDx cavity and the polarization analysis by using the ZINDO approximation. Judging from the single positive sign of the ICD signal, the polarization directions of the first π–π* transitions of the azo chromophore are almost parallel to the CDx axis. Some β- and γ-CDx complexes of the title azo compounds show a split-type [(+) to (–) or (–) to (+)] ICD band at the π–π* transitions of the azo group, suggesting that a chiral dimer is trapped within the CDx cavity. The ICD bands of the naphthalene moiety may also be useful to detect the formation of the chiral dimer.

Circular dichroism spectra of 8H-3-oxaheptalen-8-one included in β-cyclodextrin

Abstract The circular dichroism (CD) spectra of β-cyclodextrin (β-CyD) complex with 8 H -3-oxaheptalen-8-one ( 1 ) are measured. From the signs of the CD spectra of the β-CyD complex with 1 , the polarization directions of the absorption bands are investigated.

Anomalous fluorescence spectra of azuleno[1,2-b]furan

Abstract The electronic and fluorescence spectra of azuleno[1,2- b ]furan, which is an iso-π-electron system of benz[ a ]azulene, have been measured. The anomalous fluorescence spectra have been observed for azuleno[1,2- b ]furan.

Anomalous fluorescence spectra of 1-isopropylidene-1H-cyclopent[a]azulene and 3-isopropylidene-3H-cyclopent[a]azulene

Abstract The electronic and fluorescence spectra of 1-isopropylidene-1 H -cyclopent[ a ]azulene and 3-isopropylidene-3 H -cyclopent[ a ]azulene, which are iso-π-electron systems of benz[ a ]azulene, have been measured. Anomalous fluorescence spectra have been observed for both compounds. It has been concluded that these compounds emit fluorescence from the second excited singlet state.

Anomalous fluorescence spectrum of azuleno[1,2-b]pyrrole

Abstract Electronic and fluorescence spectra of azuleno[1,2-b]pyrrole, which is an iso-π-electron system of benz[a]azulene, have been measured. The an

Inclusion effects of cyclodextrins on the photobleaching of coumarins

The effects of cyclodextrins (α-CD,β-CD andγ-CD) on the photobleaching of coumarin 120 (7-amino-4-methylcoumarin) (1) and coumarin 151 (7-amino-4-trifluoromethylcoumarin) (2) have been investigated by spectrophotometric measurement. It is concluded thatβ-CD andγ-CD decelerate the rates of photobleaching of1, whilstγ-CD accelerates the rate of2 andβ-CD has no effect on the rate of photobleaching of2.

Induced circular dichroiism spectra of benz[b]anthracene included inβ-cyclodextrin

The assignment of the absorption spectra of benz[b]anthracene (1) is reported by measuring the induced circular dichroism spectra of the β-cyclodextrin complex with1. It is concluded from the signs of the induced circular dichroism bands that the first absorption band (20.4–30.9×103 cm−1) has the transition dipole moment perpendicular to the long axis and the second absorption band (30.9–37.2×102 cm−1) has the transition dipole moment parallel to the long axis of1. Our assignments are in complete agreement with earlier assignments. The induced circular dichroism spectra exhibit Cotton splittings at 19.1×103 and 42.8×103 cm−1. It can be concluded from Cotton splittings of the induced circular dichroism spectra that the association of two 1:1 inclusion complexes forms a ground-state dimer.