Raman spectra of conducting TCNQ salts; Estimation of the degree of charge transfer from vibrational frequencies

Matsuzaki, Susumu; Kuwata, R.; Toyoda, K.

doi:10.1016/0038-1098(80)90429-9

Cited by 118 publications

(60 citation statements)

References 9 publications

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“…The position of Raman bands is dependent on averaged charge density on TCNQ molecule. The most sensitive to charge density changes is the mode v4 (αg ) [11] which appears in the spectrum of VINΦ2(TCNQ)2 as a single line at 1424 cm -1 (not a doublet) and suggests that the TCNQ ionicity in both stacks is the same and equals about (1/2)e -; similar conclusion results from the analysis of the other TCNQ α g bands. This is in disagreement with the values estimated from bond lengths analysis [3] by the method of Flandrois and Chasseau [12].…”

Section: Vibrational Spectrasupporting

confidence: 77%

Spectroscopic Investigations of Charge Transfer Salt VINΦ₂(TCNQ)₂

et al. 1995

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VINΦ2(TCNQ)2 is a salt with two different, non-parallel TCNQ stacks. The polarized reflectance spectra from single crystals in the IR region 660-5200 cm-1, the powder absorption spectra 400-45000 cm -1 and FT-NIR Raman spectra of VINΦ2(TCNQ)2 are measured at room temperature. Moreover, the temperature dependence of powder absorption spectra in the frequency range 400-7900 cm -1 are studied. The nature of electronic bands, the anisotropy of optical conductivity, the temperature dependence of some vibrational bands and the charge distribution on different TCNQ stacks are discussed.

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Section: Vibrational Spectrasupporting

confidence: 77%

Spectroscopic Investigations of Charge Transfer Salt VINΦ₂(TCNQ)₂

et al. 1995

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“…The C=C stretching modes of TCNQ moieties of 9 and 10 in the Raman spectra (1403 and 1402 cm À1 , respectively, see Supporting Information) also corresponded to that of TCNQ À (1384 cm À1 ) rather than that of neutral TCNQ (1454 cm À1 ). 26 The C=O modes in the IR spectra (1750-1650 cm À1 ) of 9 and 10 (indicated by thick lines in Fig. 1b) exhibited similar features to those of 8, three broad peaks at 1726-1727, 1698-1706, and 1651-1653 cm À1 , and this observation indicated the presence of a CHC þ species or its analogs.…”

Section: Resultsmentioning

confidence: 74%

Complex Formation between a Nucleobase and Tetracyanoquinodimethane Derivatives: Crystal Structures and Transport Properties of Charge-Transfer Solids of Cytosine

Murata¹,

Saito²,

Nishimura³

et al. 2008

Bulletin of the Chemical Society of Japan

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Reaction between cytosine, a nucleobase, in methanol and several 7,7,8,8-tetracyanoquinodimethane derivatives (R-TCNQ) in acetonitrile yielded three kinds of ionic solids; (I) insulators composed of methoxy-substituted R-TCNQ anions, (II) semiconducting fully ionic R-TCNQ radical anion salts, and (III) conductive partially ionic or mixed-valent R-TCNQ radical anion salts. Electronic and chemical structures of these products were characterized by optical and magnetic measurements, and structural and elemental analyses. Cation units in all products were found to be protonated cytosine species. Crystal structures were determined for methoxy-substituted anion salts (R = F 4 and H) in Group I and R-TCNQ radical anion salts (R = H and Et 2 ) in Group II with hemiprotonated cytosine pairs formed by triple self-complementary hydrogen bonds. They established one-dimensional hemiprotonated cytosine ribbons by double complementary hydrogen bonds. Hydrogen bonds between cytosine and R-TCNQ anions exhibited high potential to regulate molecular arrangements producing a segregated layered structure and uniform arrangement of R-TCNQ radical anion columns stable down to low temperature. The partially ionic salt of MeTCNQ in Group III exhibited metallic behavior and the highest conductivity of 10 þ1 S cm À1 so far observed for charge-transfer complexes based on biological molecules.Biological molecules such as proteins, enzymes, DNA, etc., establish well-defined and complicated self-assembling structures which are important factors in the exhibition of their biological functions. This feature of biological molecules has attracted much attention from the viewpoint of supramolecular chemistry and crystal engineering in recent study of molecule-based materials.2 In research for organic conductors, several attempts to investigate charge-transfer (CT) complexes based on a variety of biological molecules have been also undertaken.

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“…A detailed normal mode analysis of TCNQ 0 and TCNQ  was reported by Bozio et al [2]. Matsuzaki et al, extended the application to the TCNQ salt with fractional charge [3]. Subsequently, vibrational spectroscopy was applied to mixed-valence compounds of TCNQ [4], where one of the CN stretching modes of TCNQ was utilized as the probe.…”

Section: Introductionmentioning

confidence: 99%

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

Yakushi

2012

Crystals

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This paper reviews charge ordering in the organic conductors, β″-(BEDT-TTF) (TCNQ), θ-(BEDT-TTF) 2 X, and α-(BEDT-TTF) 2 X. Here, BEDT-TTF and TCNQ represent bis(ethylenedithio)tetrathiafulvalene and 7,7,8,8-tetracyanoquinodimethane, respectively. These compounds, all of which have a quarter-filled band, were evaluated using infrared and Raman spectroscopy in addition to optical conductivity measurements. It was found that β″-(BEDT-TTF)(TCNQ) changes continuously from a uniform metal to a chargeordered metal with increasing temperature. Although charge disproportionation was clearly observed, long-range charge order is not realized. Among six θ-type salts, four compounds with a narrow band show the metal-insulator transition. However, they maintain a large amplitude of charge order (Δρ~0.6) in both metallic and insulating phases. In the X = CsZn(SCN) 4 salt with intermediate bandwidth, the amplitude of charge order is very small (Δρ < 0.07) over the whole temperature range. However, fluctuation of charge order is indicated in the Raman spectrum and optical conductivity. No indication of the fluctuation of charge order is found in the wide band X = I 3 salt. In α-(BEDT-TTF) 2 I 3 the amplitude of charge order changes discontinuously from small amplitude at high temperature to large amplitude (Δρ max~0 .6) at low temperature. The long-range chargeordered state shows ferroelectric polarization with fast optical response. The fluctuation of multiple stripes occurs in the high-temperature metallic phase. Among α-(BEDT-TTF) 2 MHg(SCN) 4 (X = NH 4 , K, Rb, Tl), the fluctuation of charge order is indicated only in the X = NH 4 salt. α′-(BEDT-TTF) 2 IBr 2 shows successive phase transitions to the ferroelectric state keeping a large amplitude of charge order (Δρ max~0 .8) over the whole temperature range. It was found that the amplitude and fluctuation of charge order in these compounds is enhanced as the kinetic energy (bandwidth) decreases. OPEN ACCESSCrystals 2012, 2 1292

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Raman spectra of conducting TCNQ salts; Estimation of the degree of charge transfer from vibrational frequencies

Cited by 118 publications

References 9 publications

Spectroscopic Investigations of Charge Transfer Salt VINΦ₂(TCNQ)₂

Spectroscopic Investigations of Charge Transfer Salt VINΦ₂(TCNQ)₂

Complex Formation between a Nucleobase and Tetracyanoquinodimethane Derivatives: Crystal Structures and Transport Properties of Charge-Transfer Solids of Cytosine

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

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Raman spectra of conducting TCNQ salts; Estimation of the degree of charge transfer from vibrational frequencies

Cited by 118 publications

References 9 publications

Spectroscopic Investigations of Charge Transfer Salt VINΦ2(TCNQ)2

Spectroscopic Investigations of Charge Transfer Salt VINΦ2(TCNQ)2

Complex Formation between a Nucleobase and Tetracyanoquinodimethane Derivatives: Crystal Structures and Transport Properties of Charge-Transfer Solids of Cytosine

Infrared and Raman Studies of Charge Ordering in Organic Conductors, BEDT-TTF Salts with Quarter-Filled Bands

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Spectroscopic Investigations of Charge Transfer Salt VINΦ₂(TCNQ)₂

Spectroscopic Investigations of Charge Transfer Salt VINΦ₂(TCNQ)₂