The acid catalysed triple self-condensation of 1-thien-2-ylethanone (2-acetylthiophene) and five ... more The acid catalysed triple self-condensation of 1-thien-2-ylethanone (2-acetylthiophene) and five related compounds is presented. Tetrachlorosilane used as the Lewis acid produces dry hydrogen chloride which catalyzes the self-condensation process. Depending on the reaction conditions and the substitution of the carbonyl substrates, the reaction can proceed as a [2+2+2] cyclotrimerization towards C 3-symmetric 1,3,5trisubstituted benzenes, or as the single-type aldol condensation leading to 1,3-disubstituted (E)-β-methylchalcones. This is important for the design of new aromatic/olefinic compounds beyond the model structures. Synthesis of 4'-fluoro-3,5-di-(2-thienyl)biphenyl through a mixed-type aldol reaction using erbium triflate is discussed. Mechanistic rationale is provided.
Substituted thiophene-2-carbaldehydes 1a-d were utilized in the synthesis of symmetrically substi... more Substituted thiophene-2-carbaldehydes 1a-d were utilized in the synthesis of symmetrically substituted thiazolo[5,4-d]thiazoles 3a-d. Bis(5,4-d)thiazoles with thiophene core at the termini are the most employed in the chemistry of materials but exhibit insufficient solubility in majority of organic solvents with notable impact on the low yields of products. Accordingly, the synthetic approach towards 2,5-dithiophen-2-yl-thiazolo[5,4-d]thiazole (3a) and its substituted derivatives 3b-d is discussed under the various reaction conditions. Appropriate structural characterisations are included with emphasis on relationship between structure and physicochemical properties highlighting the UV-Vis and fluorescence.
Novel D–π–A type organic small-molecules with thiazolo[5,4-d]thiazole and spirobifluorene units. ... more Novel D–π–A type organic small-molecules with thiazolo[5,4-d]thiazole and spirobifluorene units. Optoelectronical properties suggests their applications in materials. Electroluminescent devices containing the novel TzTz-based derivatives 4b, 5b show affinitive emission.
Substituted 2,2′-bithiophenes with enhanced properties and suppressed aggregation in polymers are... more Substituted 2,2′-bithiophenes with enhanced properties and suppressed aggregation in polymers are revealed to be used as π-linkers in D–π–A materials.
Highlights Fully substituted and partially fluorinated N-heteroaryl compounds were achieved via... more Highlights Fully substituted and partially fluorinated N-heteroaryl compounds were achieved via the direct nucleophilic substitution of the polyflurorobenzene derivatives The course of the SNAr reaction of hexafluorobenzene, N-pyrrolylpentafluorobenzene and its derivatives assumes the gradual substitution of the particular fluorine atoms depending on the nature of the used nucleophile. The designed compounds are symmetric and could be of benefit in the design of well-defined chromophoric arrays and optoelectronic materials.
The synthetic methods leading to furo[3,2-b]pyrroles and thiazolo [5,4-d]thiazoles are reviewed h... more The synthetic methods leading to furo[3,2-b]pyrroles and thiazolo [5,4-d]thiazoles are reviewed herein. Furo-, thieno- and seleno [3,2-b]pyrroles are related to heteropentalenes, containing two heteroatoms in the entire structure, one each per core. The synthetic approach follows the Hemetsberger–Knittel protocol covering three reaction steps—the nucleophilic substitution of halogen-containing aliphatic carboxylic acid esters, Knoevenagel condensation and, finally, thermolysis promoting the intramolecular cyclocondensation to O,N-heteropentalene. The Hemetsberger–Knittel reaction sequence is also known for the preparation of O,N-heteropentalenes with three heteroatoms (2:1) and their sulphur and selen heteroatoms containing structural analogues and bispyrroles. The synthetic approach towards thiazolo [5,4-d] thiazoles represents a more straightforward route, according to the Ketcham cyclocondensation. Proceeding with the Ketcham process is more challenging since it occurs stepwise a...
Substituted 2,2′-bithiophenes with enhanced properties and suppressed aggregation in polymers are... more Substituted 2,2′-bithiophenes with enhanced properties and suppressed aggregation in polymers are revealed to be used as π-linkers in D–π–A materials.
Highlights Fully substituted and partially fluorinated N-heteroaryl compounds were achieved via... more Highlights Fully substituted and partially fluorinated N-heteroaryl compounds were achieved via the direct nucleophilic substitution of the polyflurorobenzene derivatives The course of the SNAr reaction of hexafluorobenzene, N-pyrrolylpentafluorobenzene and its derivatives assumes the gradual substitution of the particular fluorine atoms depending on the nature of the used nucleophile. The designed compounds are symmetric and could be of benefit in the design of well-defined chromophoric arrays and optoelectronic materials.
We present the synthesis and structure characterization of three novel symmetrical azomethines 3a... more We present the synthesis and structure characterization of three novel symmetrical azomethines 3a-c derived from 2,5-diamino-thiophene-3,4-dicarbonitrile together with the unexpected by-product 4 containing the saturated hemiaminal type bond. Photophysical properties (UVeVis and photoluminiscence) are shown to be affected mainly by the central thiophene unit with no influence from the type of linkage e unsaturated imine (-HC]N-) bond in 3a-c vs. the saturated hydroxymethylamino circuit [eHNeC(OH)H-] in 4. For the first time the electronic properties, such as distribution of the frontier molecular orbitals and resulting energy gaps, for compounds 3b,c and 4 are calculated by means of density functional theory methods and confirmed by an immediate experimental method-the energy-resolved electrochemical impedance spectroscopy.
Substituted thiophene-2-carbaldehydes 1a-dwere utilized in the synthesis of symmetrically substit... more Substituted thiophene-2-carbaldehydes 1a-dwere utilized in the synthesis of symmetrically substituted thiazolo[5,4-d]thiazoles 3a-d. Bis(5,4-d)thiazoles with thiophene core at the termini are the most employed in the chemistry of materials but exhibit insufficient solubility in majority of organic solvents with notable impact on the low yields of products. Accordingly, the synthetic approach towards 2,5-dithiophen- 2-yl-thiazolo[5,4-d]thiazole (3a) and its substituted derivatives 3b-d is discussed under the various reaction conditions. Appropriate structural characterisations are included with emphasis on relationship between structure and physicochemical properties highlighting the UV-Vis and fluorescence.
We introduce an energy resolved electrochemical impedance spectroscopy method to map the electron... more We introduce an energy resolved electrochemical impedance spectroscopy method to map the electronic density of states (DOS) in organic semiconductor materials. The method consists in measurement of the charge transfer resistance of a semiconductor/electrolyte interface at a frequency where the redox reactions determine the real component of the impedance. The charge transfer resistance value provides direct information about the electronic DOS at the energy given by the electrochemical potential of the electrolyte, which can be adjusted using an external voltage. A simple theory for experimental data evaluation is proposed, along with an explanation of the corresponding experimental conditions. The method allows mapping over unprecedentedly wide energy and DOS ranges. Also, important DOS parameters can be determined directly from the raw experimental data without the lengthy analysis required in other techniques. The potential of the proposed method is illustrated by tracing weak bo...
Novel D–π–A type organic small-molecules with thiazolo[5,4-d]thiazole and spirobifluorene units. ... more Novel D–π–A type organic small-molecules with thiazolo[5,4-d]thiazole and spirobifluorene units. Optoelectronical properties suggests their applications in materials. Electroluminescent devices containing the novel TzTz-based derivatives 4b, 5b show affinitive emission.
Abstract Available online-Thiazolo[5,4-d]thiazoles/TzTz are active moieties in photovoltaic and o... more Abstract Available online-Thiazolo[5,4-d]thiazoles/TzTz are active moieties in photovoltaic and optoelectronic materials. Initial TzTz synthesis relies on the Ketcham reaction that, however is ultimate possess number of challenges. Along with practical imperfections, most of the disadvantages arise from uncertain reaction proceeding. Our study have focused on more detailed reaction proccess that is accompained with the formation of stable intermediates. Structures of achieved side products were determined and correlated with the mechanism suggesting to more complex behaviour. Physico-chemical properties combined with theoretical DFT approaches have proved that the thiazolo[5,4-d]thiazoles are suitable to be incorporated as a parts of particular organic devices.
Abstract A convenient “one-pot” Friedel–Crafts reaction of mono -, bi - and tert -thiophenes with... more Abstract A convenient “one-pot” Friedel–Crafts reaction of mono -, bi - and tert -thiophenes with trifluoroacetic acid anhydride (TFAA) as an acylating agent and magnesium perchlorate dihydrate (anhydron) as catalyst affords trifluoroacetyl-substituted products in high yields. This method provides a novel approach for the synthesis of thiophene based derivatives bearing trifluoroacetyl group. The mechanism of this reaction is suggested.
The acid catalysed triple self-condensation of 1-thien-2-ylethanone (2-acetylthiophene) and five ... more The acid catalysed triple self-condensation of 1-thien-2-ylethanone (2-acetylthiophene) and five related compounds is presented. Tetrachlorosilane used as the Lewis acid produces dry hydrogen chloride which catalyzes the self-condensation process. Depending on the reaction conditions and the substitution of the carbonyl substrates, the reaction can proceed as a [2+2+2] cyclotrimerization towards C 3-symmetric 1,3,5trisubstituted benzenes, or as the single-type aldol condensation leading to 1,3-disubstituted (E)-β-methylchalcones. This is important for the design of new aromatic/olefinic compounds beyond the model structures. Synthesis of 4'-fluoro-3,5-di-(2-thienyl)biphenyl through a mixed-type aldol reaction using erbium triflate is discussed. Mechanistic rationale is provided.
Substituted thiophene-2-carbaldehydes 1a-d were utilized in the synthesis of symmetrically substi... more Substituted thiophene-2-carbaldehydes 1a-d were utilized in the synthesis of symmetrically substituted thiazolo[5,4-d]thiazoles 3a-d. Bis(5,4-d)thiazoles with thiophene core at the termini are the most employed in the chemistry of materials but exhibit insufficient solubility in majority of organic solvents with notable impact on the low yields of products. Accordingly, the synthetic approach towards 2,5-dithiophen-2-yl-thiazolo[5,4-d]thiazole (3a) and its substituted derivatives 3b-d is discussed under the various reaction conditions. Appropriate structural characterisations are included with emphasis on relationship between structure and physicochemical properties highlighting the UV-Vis and fluorescence.
Novel D–π–A type organic small-molecules with thiazolo[5,4-d]thiazole and spirobifluorene units. ... more Novel D–π–A type organic small-molecules with thiazolo[5,4-d]thiazole and spirobifluorene units. Optoelectronical properties suggests their applications in materials. Electroluminescent devices containing the novel TzTz-based derivatives 4b, 5b show affinitive emission.
Substituted 2,2′-bithiophenes with enhanced properties and suppressed aggregation in polymers are... more Substituted 2,2′-bithiophenes with enhanced properties and suppressed aggregation in polymers are revealed to be used as π-linkers in D–π–A materials.
Highlights Fully substituted and partially fluorinated N-heteroaryl compounds were achieved via... more Highlights Fully substituted and partially fluorinated N-heteroaryl compounds were achieved via the direct nucleophilic substitution of the polyflurorobenzene derivatives The course of the SNAr reaction of hexafluorobenzene, N-pyrrolylpentafluorobenzene and its derivatives assumes the gradual substitution of the particular fluorine atoms depending on the nature of the used nucleophile. The designed compounds are symmetric and could be of benefit in the design of well-defined chromophoric arrays and optoelectronic materials.
The synthetic methods leading to furo[3,2-b]pyrroles and thiazolo [5,4-d]thiazoles are reviewed h... more The synthetic methods leading to furo[3,2-b]pyrroles and thiazolo [5,4-d]thiazoles are reviewed herein. Furo-, thieno- and seleno [3,2-b]pyrroles are related to heteropentalenes, containing two heteroatoms in the entire structure, one each per core. The synthetic approach follows the Hemetsberger–Knittel protocol covering three reaction steps—the nucleophilic substitution of halogen-containing aliphatic carboxylic acid esters, Knoevenagel condensation and, finally, thermolysis promoting the intramolecular cyclocondensation to O,N-heteropentalene. The Hemetsberger–Knittel reaction sequence is also known for the preparation of O,N-heteropentalenes with three heteroatoms (2:1) and their sulphur and selen heteroatoms containing structural analogues and bispyrroles. The synthetic approach towards thiazolo [5,4-d] thiazoles represents a more straightforward route, according to the Ketcham cyclocondensation. Proceeding with the Ketcham process is more challenging since it occurs stepwise a...
Substituted 2,2′-bithiophenes with enhanced properties and suppressed aggregation in polymers are... more Substituted 2,2′-bithiophenes with enhanced properties and suppressed aggregation in polymers are revealed to be used as π-linkers in D–π–A materials.
Highlights Fully substituted and partially fluorinated N-heteroaryl compounds were achieved via... more Highlights Fully substituted and partially fluorinated N-heteroaryl compounds were achieved via the direct nucleophilic substitution of the polyflurorobenzene derivatives The course of the SNAr reaction of hexafluorobenzene, N-pyrrolylpentafluorobenzene and its derivatives assumes the gradual substitution of the particular fluorine atoms depending on the nature of the used nucleophile. The designed compounds are symmetric and could be of benefit in the design of well-defined chromophoric arrays and optoelectronic materials.
We present the synthesis and structure characterization of three novel symmetrical azomethines 3a... more We present the synthesis and structure characterization of three novel symmetrical azomethines 3a-c derived from 2,5-diamino-thiophene-3,4-dicarbonitrile together with the unexpected by-product 4 containing the saturated hemiaminal type bond. Photophysical properties (UVeVis and photoluminiscence) are shown to be affected mainly by the central thiophene unit with no influence from the type of linkage e unsaturated imine (-HC]N-) bond in 3a-c vs. the saturated hydroxymethylamino circuit [eHNeC(OH)H-] in 4. For the first time the electronic properties, such as distribution of the frontier molecular orbitals and resulting energy gaps, for compounds 3b,c and 4 are calculated by means of density functional theory methods and confirmed by an immediate experimental method-the energy-resolved electrochemical impedance spectroscopy.
Substituted thiophene-2-carbaldehydes 1a-dwere utilized in the synthesis of symmetrically substit... more Substituted thiophene-2-carbaldehydes 1a-dwere utilized in the synthesis of symmetrically substituted thiazolo[5,4-d]thiazoles 3a-d. Bis(5,4-d)thiazoles with thiophene core at the termini are the most employed in the chemistry of materials but exhibit insufficient solubility in majority of organic solvents with notable impact on the low yields of products. Accordingly, the synthetic approach towards 2,5-dithiophen- 2-yl-thiazolo[5,4-d]thiazole (3a) and its substituted derivatives 3b-d is discussed under the various reaction conditions. Appropriate structural characterisations are included with emphasis on relationship between structure and physicochemical properties highlighting the UV-Vis and fluorescence.
We introduce an energy resolved electrochemical impedance spectroscopy method to map the electron... more We introduce an energy resolved electrochemical impedance spectroscopy method to map the electronic density of states (DOS) in organic semiconductor materials. The method consists in measurement of the charge transfer resistance of a semiconductor/electrolyte interface at a frequency where the redox reactions determine the real component of the impedance. The charge transfer resistance value provides direct information about the electronic DOS at the energy given by the electrochemical potential of the electrolyte, which can be adjusted using an external voltage. A simple theory for experimental data evaluation is proposed, along with an explanation of the corresponding experimental conditions. The method allows mapping over unprecedentedly wide energy and DOS ranges. Also, important DOS parameters can be determined directly from the raw experimental data without the lengthy analysis required in other techniques. The potential of the proposed method is illustrated by tracing weak bo...
Novel D–π–A type organic small-molecules with thiazolo[5,4-d]thiazole and spirobifluorene units. ... more Novel D–π–A type organic small-molecules with thiazolo[5,4-d]thiazole and spirobifluorene units. Optoelectronical properties suggests their applications in materials. Electroluminescent devices containing the novel TzTz-based derivatives 4b, 5b show affinitive emission.
Abstract Available online-Thiazolo[5,4-d]thiazoles/TzTz are active moieties in photovoltaic and o... more Abstract Available online-Thiazolo[5,4-d]thiazoles/TzTz are active moieties in photovoltaic and optoelectronic materials. Initial TzTz synthesis relies on the Ketcham reaction that, however is ultimate possess number of challenges. Along with practical imperfections, most of the disadvantages arise from uncertain reaction proceeding. Our study have focused on more detailed reaction proccess that is accompained with the formation of stable intermediates. Structures of achieved side products were determined and correlated with the mechanism suggesting to more complex behaviour. Physico-chemical properties combined with theoretical DFT approaches have proved that the thiazolo[5,4-d]thiazoles are suitable to be incorporated as a parts of particular organic devices.
Abstract A convenient “one-pot” Friedel–Crafts reaction of mono -, bi - and tert -thiophenes with... more Abstract A convenient “one-pot” Friedel–Crafts reaction of mono -, bi - and tert -thiophenes with trifluoroacetic acid anhydride (TFAA) as an acylating agent and magnesium perchlorate dihydrate (anhydron) as catalyst affords trifluoroacetyl-substituted products in high yields. This method provides a novel approach for the synthesis of thiophene based derivatives bearing trifluoroacetyl group. The mechanism of this reaction is suggested.
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Papers by Zita Tokárová