Effect of substituents on the solvatochromism of stilbazolium merocyanines

Niedbalska, M.; Gruda, Ilona

doi:10.1139/v90-106

Cited by 58 publications

(30 citation statements)

References 10 publications

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“…Polarized spectra of merocyanines in MBBA + EBBA were reported previously [4]. The maximum at about 400 nm belongs to a protonated form of dye whereas both maxima in a 500-700 nm spectra range belong to a free base form of dye [5][6][7]. The absorption of the protonated form in a region of 380-420 nm for both dyes in k15 is low but for meroF ( Fig.…”

Section: Methodsmentioning

confidence: 58%

Photoelectrochemical Cell with Dye Molecules Oriented in Nematic Liquid Crystal

1997

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A photoelectrochemical cell consisting of two semiconducting electrodes covered by orienting SiO x layers and filled with merocyanine solutions in nematic liquid crystal was constructed. Dye molecules were oriented as a result of the guest-host effect. Generation of photocurrent by two components of polarized light gives different values of photocurrent"ampalitude but anisotropy of photocurrent is lower than that of absorption in the region of a free base form of dye. It is explained by dominant participation of a protonated form of dye in the photocurrent generation. The 1ast form exhibits a lower degree of orientation than the free base form of dye.

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Section: Methodsmentioning

confidence: 58%

Photoelectrochemical Cell with Dye Molecules Oriented in Nematic Liquid Crystal

1997

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“…[18] This particular probe, however, is prone to aggregation in this binary solvent mixture of low polarity and relative permittivity ε r , due to hydrogen bonding between its hydroxy groups, coupled with solvophobic effects.…”

Section: Auto-association Of the Probesmentioning

confidence: 99%

“…Possible explanations for the nonlinear behavior include: i. aggregation of the more lipophilic probes leading to solvent-dependent formation of dimers and higher aggregates; the measured values of λ max being those of dye monomers or aggregates in solvents of high and low solvent polarity, respectively, [17][18][19][20][21][22][23] ii. the dye undergoing solvent-dependent cis/trans photoisomerization, with values of λ max being those of the trans isomers in polar solvents and their cis counterparts in nonpolar ones, [24] and iii.…”

Section: Introductionmentioning

confidence: 99%

Thermo‐Solvatochromism of Merocyanine Polarity Probes – What Are the Consequences of Increasing Probe Lipophilicity through Annelation?

et al. 2008

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The question raised in the title has been answered by comparing the solvatochromism of two series of polarity probes, the lipophilicities of which were increased either by increasing the length of an alkyl group (R) attached to a fixed pyridine-based structure or through annelation (i.e., by fusing benzene rings onto a central pyridine-based structure). The following novel solvatochromic probes were synthesized:. The solvatochromic behavior of these probes, along with that of 2,6-dibromo-4-[(E)-2-(1-methylpyridinium-4-yl)ethenyl]phenolate (MePMBr 2 ) was analyzed in terms of increasing probe lipophilicity, through annelation. Values of the empirical solvent polarity scale [E T (MePMBr 2 )] in kcal mol -1 correlated linearly with E T (30), the corresponding values for the extensively employed probe 2,6-diphenyl-4-(2,4,6-triphenylpyridinium-1-yl)phenolate (RB). On the other hand, the nonlinear correlations of E T (MeQMBr 2 ) or E T (MeAMBr 2 ) with E T (30) are described by second-order polynomials. Possible reasons for this behavior include: i) self-aggregation of the probe, ii) photoinduced cis/trans isomerization of the dye, and iii) probe structure-and solvent-dependent contributions of the quinonoid and zwitterionic limiting formulas to the ground and excited states of the probe. We show that mechanisms (i) and (ii) are not operative under the experimental conditions employed; experimental evidence (NMR) and theoretical calculations are presented to support the conjec-

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“…This indicates that highly polar solvents are able to stabilize the ground state of these very polar donor-acceptor chromophores to a certain extent which leads to a widening of the optical gap. [8] PhN-OFOT(2)-DCN exhibits a weak fluorescence emission at 610 nm when recorded in toluene but the emission is not observed in polar solvents such as chloroform. Because of the very strong charge-transfer character of PhN-OFOT(n)-DCN for n ¼ 3 and 4, no detectable fluorescence emission is observed when measured in common organic solvents.…”

Section: à2mentioning

confidence: 99%

Donor‐Acceptor Oligothiophenes as Low Optical Gap Chromophores for Photovoltaic Applications

et al. 2008

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Organic and polymeric photovoltaic (PV) cells show promise as low-cost, lightweight, flexible, and renewable energy sources and have been extensively investigated during the past decade. [1] Recently, tremendous progress was made in the development of bulk heterojunction organic PV cells based on p-conjugated polymers as electron donor ( p-type) materials, i.e., regioregular poly(3-alkylthiophene)s (P3HTs), blended with soluble fullerenes (C 60 ) as electron acceptor (n-type) materials, i.e., [6,6]-phenyl C 61 -butyric acid methyl ester (PCBM). With an accurate control of the formation of the nanostructure of the interpenetrating donor/acceptor polymer network by means of limiting the solvent evaporation rate or by post-fabrication thermal annealing, power conversion efficiencies (PCE) greater than 5% were achieved.[2] Meanwhile, multilayer heterojunction PV cells that are based on small molecules also advanced significantly through the use of new optimized device architectures, e.g., tandem or dual dye-doped structures, with efficiencies reportedly being as high as 5.6%. [3] However, in order to further enhance the PCEs of heterojunction PV cells it is of paramount importance to develop novel organic and polymer semiconductors exhibiting a narrow optical gap as well as a high charge carrier mobility to harvest the majority of sunlight radiation and efficiently transport the photogenerated charges to the electrodes. [1d,e] Triarylamines, which are well-known to have high holetransport mobilities and form stable cation radicals, are widely used as hole-transporting materials in organic light emitting diodes (LED), [4] and show potential as molecular based magnets. [5] Recently, it was demonstrated that light emitting molecules/ polymers which are incorporated or end-capped with diarylamine/triarylamine moieties exhibit a greatly enhanced LED device performance. [6] In order to further improve the light harvesting efficiency of a hole-transporting triarylamine, hence enable its efficient application in photovoltaics, it is necessary to reduce its optical energy gap to better match the solar spectrum. The use of electron-accepting dicyanovinyl groups to introduce the low-lying LUMO of triarylamine derivatives into p-type semiconducting star-shaped molecules thereby reducing the optical energy gap has been reported.[7]Herein, we report the synthesis and characterization of novel hole-transporting and narrow HOMO-LUMO energy gap oligothiophenes that are asymmetrically endcapped with diphenylaminofluorenyl and dicyanovinyl groups, i.e., PhN-OFOT(n)-DCN (n ¼ 2-4), and their potential for photovoltaic applications. The incorporation of triarylamino-donors and dicyanovinylacceptors greatly reduces the optical energy gap of oligothiophene thin-films to 1.82-1.92 eV, while the first ionization energy remains high with $5.2 eV, which is important in obtaining high open-circuit voltages (V oc ) as well as improving air stability. An increase in oligothiophene length provides stronger light absorption and promotes better ...

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Effect of substituents on the solvatochromism of stilbazolium merocyanines

Cited by 58 publications

References 10 publications

Photoelectrochemical Cell with Dye Molecules Oriented in Nematic Liquid Crystal

Photoelectrochemical Cell with Dye Molecules Oriented in Nematic Liquid Crystal

Thermo‐Solvatochromism of Merocyanine Polarity Probes – What Are the Consequences of Increasing Probe Lipophilicity through Annelation?

Donor‐Acceptor Oligothiophenes as Low Optical Gap Chromophores for Photovoltaic Applications

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