Electronic Structure of Radical Anions and Cations of Polysilanes with Structural Defects

C 3 symmetric chiral trimethylsumanene was enantioselectively synthesized through Pd-catalyzed syn-selective cyclotrimerization of an enantiomerically pure iodonorbornenone, ring-opening/closing olefin metathesis, and oxidative aromatization where the sp 3 stereogenic center was transmitted to the bowl chirality. Chiral HPLC analysis/resolution of the derivatives were also achieved. Based on theoretical calculations, the columnar crystal packing structure of sumanene and trimethylsumanene was interpreted as due to attractive electrostatic or CH³ interaction. According to the experimental and theoretical studies, the bowl depth and inversion energy were found to increase on methylation for sumanene in contrast to corannulene. Dissimilarities of the effect of methylation on the bowl structure and inversion energy of sumanene and corannulene were ascribed to differences in steric repulsion. A double-well potential model was fitted to the bowl structureinversion energy correlation of substituted sumanenes, with a small deviation. The effects of various substituents on the sumanene structure and bowl-inversion energy were analyzed by density functional theory calculations, and it was shown that the bowl rigidity is controlled by a combination of electronic and steric effects of the substituents. The electron conductivity of trimethylsumanene was investigated by time-resolved microwave conductivity method, compared with that of sumanene.In the wake of the discovery of fullerene, the chemical and physical properties of buckybowls have attracted a great deal of interest because of their unique bowl-shaped ³-conjugated structure. 13 The science of buckybowls has grown as a result of the development of practical routes for the synthesis of compounds such as sumanene (1) 4 and corannulene (2) have also been studied. With this background knowledge, we studied five aspects of C 3 symmetric trimethylsumanene (3), as listed below. Direct Selective Synthesis of C 3 Symmetric Substituted Sumanenes. One of the major difficulties in studying the properties of sumanene (1) is that of selective synthesis of its derivatives. Because sumanene is C 3v symmetric, the selective synthesis of C 3 symmetric trisubstituted derivatives through functionalization at either methylene or benzene is difficult to achieve. Functionalization of the parent compound 1 results in mixtures of regioisomers, with the desired C 3 symmetric derivatives as minor products that are difficult to separate. 6c,6i Because of the importance of C 3 symmetric trisubstituted derivatives for studies on the physical properties of sumanene (1) and its derivatives or for further transformation into ³-conjugated derivatives, functionalized sumanenes have to be

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“…Other details of the transient spectroscopy have been described elsewhere. 22 A typical instrument function was µ8 ns.…”

Section: Methodsmentioning

confidence: 99%

Trimethylsumanene: Enantioselective Synthesis, Substituent Effect on Bowl Structure, Inversion Energy, and Electron Conductivity

Higashibayashi

Tsuruoka

Soujanya

et al. 2012

Bulletin of the Chemical Society of Japan

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“…The synthesis details of monomers and polymers were described elsewhere. 13,19 The chemical structures of the synthesized polymers are shown in Figure 1. The other experimental details are described in each corresponding section as below.…”

Section: Methodsmentioning

confidence: 99%

“…13,[18][19][20][21][22] The degree of charge delocalization on -conjugated chains is discussed in terms of the molecular stiffness of -conjugated polymers, and the role of pendant rings in the charge carrier transport processes in polymer materials is addressed.…”

Section: -4mentioning

confidence: 99%

“…TAS provides direct information on the number of ion radicals of -conjugated polymers formed by electron beam irradiation, leading experimentally to the density of charge carriers in the media. 13,19,20,22 As the conductivity of the charge carriers can be measured by PR-TRMC, the combination of the two techniques represents a comprehensive approach to determining the intrinsic mobility on isolated Si chains. 27,40 The -conjugated polymers have also been focused on as the radiation sensitive polymeric materials since the discovery of the polymers soluble to several organic solvents, because their efficient main chain scission reactions upon exposure to UV light and ionizing radiation was capable to use them as resist materials in the field of micro-and nano-lithography.…”

Section: -4mentioning

confidence: 99%

“…The IR band of cation radicals of PHn also tend to shift dramatically with an elongation of n-alkyl substituents, despite of negligible small change observed for the IR bands of MEn and PDn anion radicals. 20 The peak energy of the IR band in relation to the binding energy of negative or positive polarons on the Si chains 19,71 is given by…”

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confidence: 99%

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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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An Isolable Radical Anion of an Organosilicon Cluster Containing Only σ Bonds

et al. 2015

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The radical anion of octa-tert-butyloctasilacubane was generated and isolated. The EPR spectrum showed the satellites due to the tertiary 13 Cn uclei of the eight tert-butyl groups.T he X-rayc rystallographic analysis showed that the SiÀSi bonds are shortened and the SiÀCb onds are elongated compared with those of octa-tert-butyloctasilacubane.T hese results are well explained by the distribution of an unpaired electron in the singly occupied molecular orbital (SOMO).

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Electronic Structure of Radical Anions and Cations of Polysilanes with Structural Defects

Cited by 74 publications

References 26 publications

Trimethylsumanene: Enantioselective Synthesis, Substituent Effect on Bowl Structure, Inversion Energy, and Electron Conductivity

Trimethylsumanene: Enantioselective Synthesis, Substituent Effect on Bowl Structure, Inversion Energy, and Electron Conductivity

Optoelectronic Properties and Nanostructure Formation of σ-Conjugated Polymers

An Isolable Radical Anion of an Organosilicon Cluster Containing Only σ Bonds

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