Ideal Exciton Spectra in Single- and Double-Screw-Sense Helical Polysilanes

Fujiki, Michiya

doi:10.1021/ja00092a082

Cited by 163 publications

(111 citation statements)

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“…These result in the following unique spectroscopic features, which dif-fer significantly from those of random coiled polysilanes. [15][16][17]19 First, the Cotton CD spectral profile around 320 nm exactly matches the corresponding 320-nm UV absorption. The local helical conformation of 2's is assumed to be a 7 3 helix or its nearly equal loose helix.…”

Section: Results and Discussion Temperature Dependence Of Helical Conmentioning

confidence: 75%

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

et al. 1998

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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.

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Section: Results and Discussion Temperature Dependence Of Helical Conmentioning

confidence: 75%

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

et al. 1998

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“…In the last two decades, we have designed and synthesized a wide range of polysilanes comprising chiral and/or achiral side groups. [34][35][36][37][38][39][40][41][42][43][44][45][46][47][48] MF realized that polysilanes were gifted with unique features of exhibiting intense and sharp UV absorption, circular dichroism (CD), and photoluminescence (PL) spectra around 300-400 nm, characteristic of the r-conjugation in the helical silicon-catenated main chain. Individual rod-like helical polysilanes in solution afford a highly intense, narrow exciton absorption band along with a sharp mirror-imaged emission band.…”

Section: Helical Polysilanesmentioning

confidence: 99%

Nonclassical forces: Seemingly insignificant but a powerful tool to control macromolecular structures

Fujiki

Saxena

2008

J. Polym. Sci. A Polym. Chem.

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Strong chemical forces such as covalent and ionic bonds are responsible for building discrete molecules, nature dwells on noncovalent forces weaker by three orders in magnitude, like the hydrophobic effect, hydrogen bonding, and van der Waals forces. Despite being weak, they possess the potential to drive spontaneous folding or unfolding of proteins and nucleic acids and the recognition between complimentary molecular surfaces. The power of these forces lies in the cooperativity with which they act, thereby generating a cumulative effect of many bonding interactions occurring together. Many ongoing research aims to translate the potential of these forces to the synthetic world to create desired structures with specific chemical functions. Achieving this offers unlimited opportunities for designing and synthesizing the most complex structures with specific applications. This highlight aims to reflect the critical role these noncovalent forces play in controlling macromolecular structures, which hold immense untapped potential for applications defying conventions, and briefly touches on the concept of homochirality in nature based on chiral and weak noncovalent interactions in synthetic nonpolar Si‐catenated polymers. It sheds some light on the discovery and characterization of Si/F‐C interactions in fluoroalkylated polysilanes in chemosensing of fluoride ions and nitroaromatics with a great sensitivity and selectivity. © 2008 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 46: 4637–4650, 2008

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“…7,8 The mean length of the segments is controlled by steric hindrance of the side chains and/or thermal molecular motion. Several groups have reported the synthesis of a series of polysilanes or polygermanes with backbone conformations varying from random coil to stiff and rod-like by changing the polymer substitution pattern, [9][10][11] and the clear correlation between the conformation of the backbones and the characteristic electronic transition observed at near-UV region has been also reported. This is indicative that one can easily estimate the conformation of the -conjugated polymers in solvent at any temperatures by the simple spectroscopy of -conjugated polymer solutions.…”

Section: -4mentioning

confidence: 99%

Optoelectronic Properties and Nanostructure Formation of σ-Conjugated Polymers

Seki

Tagawa

2007

Polym J

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ABSTRACT:This paper reviews recent studies on the opto-electronic properties of -conjugated polymers as well as the nanostructure formation based on the polymeric materials by the single particle nanofabrication technique. The direct quantitative correlation has been found between backbone conformation of -conjugated polymers and delocalization of charge carriers along their conjugated backbones by transient spectroscopy of the ion radicals. The microwave conductivity measurement technique was applied to estimate the intra-chain mobility of the charge carriers, giving the value of isotropic mobility holes along the chains as ca.. This is suggestive that the potentials of rod-like conjugated backbones in polysilanes as 1-D semiconductor are competitive to those of amorphous silicon.Cross-linking reaction of the -conjugated polymers was firstly promoted by charged particle irradiation to the thin films in the present study. Non-homogeneous cross-linking reaction in the polymers gives clear nanowires whose sizes, length, and number density are fairly controlled by selecting particles, molecular weights, etc. We believe that the present technique is applicable to produce wire-like nanostructures based on a variety of polymeric materials via the simple cross-linking reaction schema.

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Ideal Exciton Spectra in Single- and Double-Screw-Sense Helical Polysilanes

Cited by 163 publications

References 0 publications

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

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

Nonclassical forces: Seemingly insignificant but a powerful tool to control macromolecular structures

Optoelectronic Properties and Nanostructure Formation of σ-Conjugated Polymers

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