**6.3. Chiral induction behavior of chiral PSQ to dye compound**

These chiral ladder-like PSQs were applied to chiral inductors for hybridization with a dye compound such as an anionic achiral porphyrin by the ion-exchange reaction (Kaneko & Iyi, 2009; Kaneko et al., 2011). In this section, the author describes the chiral induction behavior from the aforementioned chiral ladder-like PSQs into an anionic achiral porphyrin such as tetraphenylporphine tetrasulfonic acid (TPPS).

In the UV–Vis spectra of TPPS/R6- and S6-PSQs aqueous mixtures (4 mol/L and 100 mol unit/L, respectively), absorptions due to the Soret band of TPPS in these mixtures were blueshifted (to 400 nm) compared with that of TPPS alone indicated monomeric state with protonated (at 434 nm) and deprotonated (at 414 nm) species (Fig. 4a). These results indicate that the negatively charged TPPS formed H-aggregates along the positively charged ammonium groups as side-chains of the PSQs.

The ECD spectra of these TPPS/PSQs aqueous mixtures showed the reversed absorptions due to the Soret bands of TPPS-aggregates, corresponding to R6- and S6-PSQs as templates, respectively (Fig. 4b), indicating that TPPS-aggregates have chiralities induced from the chiral PSQs.

However, these mixtures did not show fluorescence emissions due to self-quenching of the excited state of the TPPS-aggregate. Therefore, to inhibit the formation of H-aggregates of TPPS by extension of the distance between the ammonium chloride side chains of PSQs, same analyses were performed using R80- and S80-PSQs as chiral inductors.

ECD spectra of TPPS/R80- and S80-PSQs mixtures in methanol (4 mol/L and 100 mol unit/L, respectively) exhibited the reverse absorptions at 418 nm (Fig. 4d), corresponding to the absorptions assigned to the Soret bands of TPPS in the UV–Vis spectrum (Fig. 4c). The absorption wavelength of this mixture was almost same as that of dilute methanol solution of sole TPPS (concentration = 4 mol/L), indicating that TPPS maintained the monomeric state in the mixture. These results indicate that the chiral induction from PSQs to TPPS was achieved without formation of H-aggregate of TPPS. In the present mixture, because of no formation of H-aggregate, the fluorescence spectrum excited at 420 nm showed an emission peak at 654 nm.

**Figure 4.** (a) UV–Vis spectrum of aqueous mixture of TPPS/R6-PSQ, (b) ECD spectra of aqueous mixtures of TPPS/R6- and S6-PSQs, (c) UV–Vis spectrum of mixture in methanol of TPPS/R80-PSQ, and (d) ECD spectra of mixtures in methanol of TPPS/R80- and S80-PSQs.

### **7. Conclusion**

86 Ion Exchange Technologies

conformations of these PSQs.

the rigid structures of PSQs would be maintained.

tetraphenylporphine tetrasulfonic acid (TPPS).

ammonium groups as side-chains of the PSQs.

chiral PSQs.

The diffraction peaks in the XRD patterns of the PSQs were broadened compared with those of PSQ-NH3+Cl–. This is due to the decrease in the number of ion pairs, *i.e.*, ammonium chloride groups. The ion pair has an important role in the construction of a regular higherordered structure. However, because the XRD pattern of the product film showed diffraction peaks with *d*-value of 1.80 nm, indicating a relatively regular stacking structure,

The chiral conformations of many kinds of helical polymers are stabilized by intramolecular interaction, *e.g.*, hydrogen bonding (Zhao et al., 2004). Therefore, specific rotations of these polymers are generally changed by varying the solvents because their intramolecular interactions are affected by the nature of the solvent. The specific rotations []D22 of R80- and S80-PSQs in methanol were +17.4º and –18.9º, respectively, while those in DMF were +8.6º and –8.5º, respectively. Because these PSQs have urea groups as side chains, which are involved in intramolecular hydrogen bonding, their []D22 values were probably affected by solvent effects. Such a solvent effect on specific rotations indicates the presence of chiral

These chiral ladder-like PSQs were applied to chiral inductors for hybridization with a dye compound such as an anionic achiral porphyrin by the ion-exchange reaction (Kaneko & Iyi, 2009; Kaneko et al., 2011). In this section, the author describes the chiral induction behavior from the aforementioned chiral ladder-like PSQs into an anionic achiral porphyrin such as

In the UV–Vis spectra of TPPS/R6- and S6-PSQs aqueous mixtures (4 mol/L and 100 mol unit/L, respectively), absorptions due to the Soret band of TPPS in these mixtures were blueshifted (to 400 nm) compared with that of TPPS alone indicated monomeric state with protonated (at 434 nm) and deprotonated (at 414 nm) species (Fig. 4a). These results indicate that the negatively charged TPPS formed H-aggregates along the positively charged

The ECD spectra of these TPPS/PSQs aqueous mixtures showed the reversed absorptions due to the Soret bands of TPPS-aggregates, corresponding to R6- and S6-PSQs as templates, respectively (Fig. 4b), indicating that TPPS-aggregates have chiralities induced from the

However, these mixtures did not show fluorescence emissions due to self-quenching of the excited state of the TPPS-aggregate. Therefore, to inhibit the formation of H-aggregates of TPPS by extension of the distance between the ammonium chloride side chains of PSQs,

ECD spectra of TPPS/R80- and S80-PSQs mixtures in methanol (4 mol/L and 100 mol unit/L, respectively) exhibited the reverse absorptions at 418 nm (Fig. 4d), corresponding to the absorptions assigned to the Soret bands of TPPS in the UV–Vis spectrum (Fig. 4c). The

same analyses were performed using R80- and S80-PSQs as chiral inductors.

**6.3. Chiral induction behavior of chiral PSQ to dye compound** 

In this chapter, the author described the preparation of cationic ladder-like PSQs with hexagonally stacked structures by the sol–gel reaction of amino group-containing trialkoxysilane monomers using acid-catalysts. Then, their detailed characterizations were performed. The resulting PSQs indicated the anion-exchange properties due to existence of cationic functional groups as side-chains. Therefore, it is also described that the anion-exchange

behaviors with various organic and inorganic compounds such as anionic surfactants, a polymer, layered clay minerals, and a dye molecule to obtain the functional hybrid materials.

### **Author details**

Yoshiro Kaneko *Graduate School of Science and Engineering, Kagoshima University, Japan* 
