Time filter

Source Type

Rybitví, Czech Republic

Vala M.,Brno University of Technology | Vynuchal J.,Research Institute of Organic Syntheses | Toman P.,Czech Institute of Macromolecular Chemical | Weiter M.,Brno University of Technology | Lunak Jr. S.,University of Pardubice
Dyes and Pigments | Year: 2010

Derivatives of diphenyl-diketo-pyrrolopyrrole, possessing electron-donating or withdrawing groups in the p-position of the phenyl, were synthesized and studied using optical characterization (absorption, fluorescence, time-resolved fluorescence) and quantum chemical calculation. An increase in absorption coefficient ≥105 dm3 mol-1 cm-1 was observed using electron-donor groups; a bathochromic shift in both absorption and luminescence peaks was observed as a result of increased conjugation. Soluble derivatives were obtained by the introduction of alkyl groups (by N-alkylation) in the central pyrrolopyrrole unit. Calculated phenyl torsion angles using HF and B3LYP methods showed that the loss of molecule planarity reduced the extent of overlap between the π-orbitals of the central pyrrolopyrrole unit and phenyls after N-alkylation. This treatment thus reduced both the bathochromic shift and increased absorption coefficient. The presence of the donor or acceptor groups in itself does not influence molecule planarity. © 2009 Elsevier Ltd. All rights reserved. Source

Lunak Jr. S.,University of Pardubice | Havel L.,University of Pardubice | Vynuchal J.,Research Institute of Organic Syntheses | Vynuchal J.,Synthesia A.s. | And 4 more authors.
Dyes and Pigments | Year: 2010

A series of five symmetrical and four unsymmetrical diaryl substituted diketo-pyrrolo-pyrroles was synthesized; two unsymmetrical derivatives are reported for the first time. The relationship between the theoretical excitation energies of the S0 → S1 transition, computed by time dependent density functional theory and the experimental positions of 0-0 vibronic bands in the visible absorption (or fluorescence excitation) spectra was studied. Experimental data were obtained from either solution or from low temperature organic solvent glass, in which the progressions of the vibrational structure enabled correct assignment of vibronic sub-bands in some cases. Theoretical calculations predicted that a linear bathochromic and hyperchromic shift would accompany substitution of each phenyl in the parent 3,6-diphenyl-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione by providing a more extensively conjugated aryl centre (2-naphthyl, biphenyl, stilbenyl) for the ensuing planar derivatives. Qualitatively, the experimental bathochromic shifts of the 0-0 vibronic sub-bands were in exact agreement with theory, whilst hyperchromic shifts were affected by the very low solubility of the planar, symmetrical derivatives. Deviations from this ideal behaviour were observed for non-planar derivatives (aryl = stilbenyl or 1-naphthyl), for which the dihedral angles describing the aryl, out-of-plane torsions were probably underestimated by DFT. © 2009 Elsevier Ltd. All rights reserved. Source

Lunak Jr. S.,University of Pardubice | Vynuchal J.,Research Institute of Organic Syntheses | Vynuchal J.,Synthesia A.s. | Horackova P.,University of Pardubice | And 4 more authors.
Journal of Molecular Structure | Year: 2010

A complete series of symmetrical and unsymmetrical isomeric pairs of 4- and 2-pyridyl substituted diketo-pyrrolo-pyrroles was synthesized. Both polymorphs of 3,6-bis-(4′-pyridyl)-2,5-dihydro-pyrrolo[3,4-c]pyrrole-1,4-dione were prepared. Asymmetrical 3-phenyl-6-pyridine-2′-yl-2,5-dihydro-pyrrolo[3,4- c]pyrrole-1,4-dione was synthesized for the first time and X-ray structure of its monocrystal was determined. Density functional theory calculations of the ground state geometry were compared with experimental X-ray diffraction data. Theoretical Raman spectra enabled to assign the main peaks of the experimental ones for all four pyridyl DPP derivatives. Crucial spectral features, which reflect the molecular and crystal (H-bond invoked) asymmetry are CO (pyrrolinone) stretching, NH (pyrrolinone) bending and trigonal (hetero)aryl bending. Sublimation temperatures of 2-pyridyl derivatives are significantly lower than for 4-pyridyl derivatives, in which stronger in-plane NH(pyrrolinone)CO(pyrrolinone) intermolecular H-bonding dominates. © 2010 Elsevier B.V. All rights reserved. Source

Kucerik J.,University of Koblenz-Landau | Kucerik J.,Brno University of Technology | David J.,Brno University of Technology | Weiter M.,Brno University of Technology | And 4 more authors.
Journal of Thermal Analysis and Calorimetry | Year: 2012

Crystalline structure, thermo-oxidative and thermal stability of symmetrical and asymmetrical piperidyl and morpholinyl derivatives of both N-substituted and non- N-substituted butyl diphenyl-diketo-pyrrolopyrrole (DPP) pigments were studied using differential scanning calorimetry (DSC) and thermogravimetry (TG). Except for the asymmetrical morpholine DPP derivative, all the samples showed melting peaks which were relatively close to their degradation temperatures (from 260 to 430 °C). Using DSC, monotropic polymorphism was revealed in the symmetrical piperidyl-N-butyl-derivative which confirmed earlier observation about tendency of symmetrical N-alkyl DPP derivates to form several crystalline structures. TG carried out under nitrogen atmosphere served for distinguishing of evaporation/sublimation and degradation temperatures. Temperatures of evaporation/sublimation were typically 10-30 °C lower in comparison with temperatures of thermal degradation. The highest thermal (450 °C) and thermo-oxidative stability (around 360 °C) showed the DPP derivatives containing morpholine moieties with no alkyl substitution on NH-group of DPP core. The presence of the latter was found to be the most destabilizing factor. Piperidyl group showed more stabilizing effect due to its polar character and its influence on π-π intermolecular interactions of neighbouring phenyl groups. The highest stabilizing effect of morpholine moiety on DPP structure was explained based on the presence of polar oxygen atom in that group. The preparations of 3,6-di-(4-morpholinophenyl)-2,5-dihydro-pyrrolo- [3,4-c]pyrrole-1,4-dione and 3-(phenyl)-6-(4-morpholinophenyl)- 2,5-dihydropyrrolo[3,4-c]pyrrole-1,4-dione are reported. © Akadémiai Kiadó, Budapest, Hungary 2011. Source

Lunak Jr. S.,University of Pardubice | Vala M.,Brno University of Technology | Vynuchal J.,University of Pardubice | Vynuchal J.,Research Institute of Organic Syntheses | And 6 more authors.
Dyes and Pigments | Year: 2011

Six soluble derivatives of 3,6-diphenyl-2,5-dihydro-pyrrolo[3,4-c]pyrrole- 1,4-dione N-alkylated on pyrrolinone ring with polar substituents in para positions of pendant phenyl rings were synthesized; five of them are reported for the first time. Absorption and fluorescence spectra were studied in solvents of different polarity. The compounds show small solvatochromism of absorption and a moderate positive solvatochromism of fluorescence, especially when substituted by strong electron-donating piperidino substituent. A significant decrease of fluorescence quantum yields and its biexponential decay for dipolar derivatives in polar solvents was tentatively ascribed to the formation of twisted intramolecular charge transfer (TICT) excited state. All six compounds show fluorescence in polycrystalline solid-state with the maxima covering a range over 200 nm in visible and near infrared region. © 2011 Elsevier Ltd. All rights reserved. Source

Discover hidden collaborations