Near-UV, circular dichroism, and fluorescence spectra of a rigid rodlike helical polysilane bearing trietheral moiety in ethanol/water

Abstract

An optically active, rigid rodlike helical polysilane with 6,9,12‐trioxatetradecyl and (S)‐2‐methylbutyl substituents (1) was newly obtained as a very high molecular weight polymer of several million. Due to the presence of trietheral substituent, 1 was readily soluble in a polar solvent such as ethanol and a mixture of ethanol and water, but was insoluble in pure water. Polysilane 1 in pure ethanol at room temperature exhibited an intense and narrow ultraviolet (UV) and circular dichroism (CD) absorptions at 323 nm, associated with an almost mirror imaged fluorescence (FL) at 328 nm, that are characteristic of rigid rodlike, single‐screw‐sense helical polysilanes reported previously. When solution temperature was changed from 60°C to −104°C, a global shape of 1 expanded associated with an increase of segment length, whereas a screw pitch tended to be wound tightly. On the other hand, as a solvent polarity became poor, a global shape of 1 shrunk associated with an decrease of segment length and formed a chiral motif with an M‐helicity between two helical segments with a kink. At a ratio of 50% of ethanol/water of 50:50 (v/v), 1 became insoluble and formed aggregates. Chirality 10:667–675, 1998. © 1998 Wiley‐Liss, Inc.

Optically Active Polysilylenes: State-of-the-Art Chiroptical Polymers

“…However, it is noted that chiral alkyl termini (a very small portion of the substituents on the main chain) also affect the overall screw-sense of a main chain with achiral side groups, and that the PSS of 15 was opposite to that of 4 bearing the same (S)-2-methylbutyl side groups (Figure 13). [60,62,63,72] …”

“…For this purpose, an optically active, rigid rod-like helical polysilylene having 6,9,12-trioxatetradecyl and (S)-2-methylbutyl side groups (17) of high molecular weight (M -w = 7.0 6 10 6 and M -n = 2.9 6 10 6 ) was prepared, [72] as shown in Figure 14. Several workers demonstrated that the introduction of oligoetheral side groups to the flexible polysilylene main chain is able to afford greater solubility in alcohol and water as well as hydrophilic properties, [101, 117 -119] whereas the family of 4 bearing alkyl side group is soluble hydrocarbons and tetrahydrofuran only.…”

Ionochromism and Increase in Fluorescence Quantum Yield of an Ether-Substituted Polysilylene upon Adding Lithium Ions in Solution

“…13 The addition of LiTFMS to a PTMS solution in methanol, ethanol, n-butanol, din-butyl ether, or THF did not result in any ionochromic behavior. PTMS also does not show any significant thermochromism, exhibiting only a gradual blue shift as the temperature decreases.…”

“…1-Chloro-5-(2-ethoxyethoxy)pentane was isolated by distilling the reaction mixture under vacuum. 13 The chloride (50 g) was reacted with magnesium (3 g) at 75°C. The mixture was added slowly to tetrachlorosilane (18 g) in dry diethyl ether at 40°C.…”

“…Di-6,9-dioxaundecyldichrolosilane (1) was isolated by distilling the reaction mixture in a vacuum. 13 The monomer 1 (3 g) was reacted with sodium metal (0.5 g) in toluene (30 mL) for 30 min at 110°C. After removal of toluene from the mixture in a vacuum, the resulting solids were dissolved in ethanol (100 mL) and filtered under an Ar gas pressure.…”