Structural aspects of oligothienyl series from X‐ray powder diffraction data

Porzio, William; Destri, Silvia; Mascherpa, Marco Carlo; Brückner, Sergio

doi:10.1002/actp.1993.010440602

Cited by 171 publications

(129 citation statements)

References 23 publications

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“…The "lowtemperature" (LT) structure, [17,18] which is monoclinic, space group P2 1 /n with Z = 4, and the "high-temperature" (HT) structure [19] also monoclinic, but with the space group P2 1 /a and Z = 2. To investigate polymorphism in T6, we have used confocal Raman microscopy in the lattice phonon region to discriminate different crystal lattices.…”

Section: Confocal Raman Mapping Of T6 Bulk Crystalsmentioning

confidence: 99%

“…[3,7,9,16] The two polymorphs in the bulk crystal of T6, previously identified by X-ray diffraction experiments, [17][18][19] have been recently studied by confocal Raman spectroscopy, [20] a versatile and powerful tool for in-situ discrimination of crystal structures. There, we have observed that mixed micro-domains of the two phases may be obtained simultaneously from the same sublimation process and can coexist even in the same crystallite, showing up as physical impurities of one phase inside the other.…”

Section: Introductionmentioning

confidence: 99%

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Confocal Raman Spectroscopy of α‐Sexithiophene: From Bulk Crystals to Field‐Effect Transistors

Brillante¹,

Bilotti²,

Albonetti³

et al. 2007

Adv Funct Materials

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We report confocal micro‐Raman spectra of the organic semiconductor α‐sexithiophene (T6) on bulk crystals and on thin films grown on technologically relevant substrates and devices. We show that the two polymorphs, which are clearly identified by their lattice phonon spectra, may coexist as physical impurities of one inside the other in the same crystallite. Spatial distribution of the two phases is monitored by Raman phonon mapping of crystals grown upon different conditions. Raman microscopy has then been extended to T6 thin films grown on silicon oxide wafers. We identify the crystal phase in thin films whose thickness is just 18 nm. The most intense total‐symmetric Raman vibration is still detectable for a two‐monolayer thick film. Comparative analysis between micro‐Raman and AFM of T6 thin films grown on field effect transistors shows that electrode‐channel steps favour the nucleation and growth of T6 molecules on the substrate, at least below 50 nm.

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Section: Confocal Raman Mapping Of T6 Bulk Crystalsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Confocal Raman Spectroscopy of α‐Sexithiophene: From Bulk Crystals to Field‐Effect Transistors

Brillante¹,

Bilotti²,

Albonetti³

et al. 2007

Adv Funct Materials

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“…Such molecules pack in a herringbone arrangement with at least 2 molecules in a unit cell. [20][21][22][23] Here, the lower Davydov component ͑alias J-band͒ is weakly allowed along the crystal b direction, 20,[24][25][26] leading to b-polarized superradiant 0-0 emission 27 which diminishes with increasing disorder. [28][29][30][31] In helical MOPVn aggregates, coherence affects the PL spectrum in a manner similar to the ideal linear H-aggregates described above.…”

Section: Introductionmentioning

confidence: 99%

Using circularly polarized luminescence to probe exciton coherence in disordered helical aggregates

Spano

Meskers

Hennebicq

et al. 2008

The Journal of Chemical Physics

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Circularly polarized emission from helical MOPV4 aggregates is studied theoretically based on a Hamiltonian including excitonic coupling, exciton phonon coupling, and site disorder. The latter is modeled via a Gaussian distribution of site energies. The frequency dependence of the circularly polarized luminescence dissymmetry g lum ͑͒ contains structural information about the low-energy-neutral ͑excitonic͒ polaron from which emission originates. Near the 0-0 emission frequency, g lum ͑͒ provides a measure of the exciton coherence length, while at lower energies, in the vicinity of the sideband frequencies, g lum ͑͒ probes the polaron radius. The present work focuses on how the 0-0 dissymmetry, g lum 0-0 , relates to the emitting exciton's coherence function, from which the coherence length is deduced. In the strong disorder limit where the exciton is localized on a single chromophore, g lum 0-0 is zero. As disorder is reduced and the coherence function expands, ͉g lum 0-0 ͉ increases more rapidly than the sideband dissymmetries, resulting in a pronounced surge in g lum ͑͒ near the 0-0 transition frequency. The resulting spectral shape of g lum ͑͒ is in excellent agreement with recent experiments on MOPV4 aggregates. In the limit of very weak disorder, corresponding to the motional narrowing regime, the coherence function extends over the entire helix. In this region, g lum 0-0 undergoes a surprising sign reversal but only for helices which are between n + 1 2 and n + 1 complete turns ͑n =0,1, ...͒. This unusual sign change is due to the dependence of the rotational line strength on long-range exciton coherences which are also responsible for a heightened sensitivity of g lum ͑͒ to long-range excitonic coupling.

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“…Reliable structural data currently available have shown that these oligomers are essentially planar with a fully conjugated carbon skeleton. 7,8 Much work has been devoted in past years to -substituted oligothiophenes to obtain soluble materials easy to characterize and process. [9][10][11][12][13][14] In comparison with the -substitution, the R,R′-disubstitution has the advantage of inducing only very small conformational distortions of the outermost rings, thus preserving the conjugation and the electronic properties of the materials.…”

Section: Introductionmentioning

confidence: 99%

A Combined Spectroscopic and Theoretical Study of a Series of Aminomethyl End-Capped Oligothiophenes with Potential Applications in Thin Film Devices

et al. 2000

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In this article, we investigate the vibrational properties of a series of π-conjugated R,R′-bis(aminomethyl)-oligothiophenes, in the pristine state, as solids. The FT-IR and FT-Raman spectra have been studied in relation to the effective conjugation length of the compounds. We have used ab initio calculations, at the B3LYP/ 6-31G** and RHF/6-31G** levels, as a support of the experimental analysis. Our study reveals that the aminomethyl end groups easily undergo a protonation process upon reaction with atmospheric moisture, although this does not affect the electronic structure of the π-conjugated spine. This structural characteristic of these oligothiophenes brings new practical applications for possible technological developments.

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Structural aspects of oligothienyl series from X‐ray powder diffraction data

Cited by 171 publications

References 23 publications

Confocal Raman Spectroscopy of α‐Sexithiophene: From Bulk Crystals to Field‐Effect Transistors

Confocal Raman Spectroscopy of α‐Sexithiophene: From Bulk Crystals to Field‐Effect Transistors

Using circularly polarized luminescence to probe exciton coherence in disordered helical aggregates

A Combined Spectroscopic and Theoretical Study of a Series of Aminomethyl End-Capped Oligothiophenes with Potential Applications in Thin Film Devices

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