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Papers by Ivica Sigmundová
Journal of Physical Chemistry A, Oct 15, 2019
The Journal of Physical Chemistry, 2018
Arkivoc, Apr 4, 2008
New 2-styryl benzothiazolium salts substituted on the heterocyclic ring have been synthesised by ... more New 2-styryl benzothiazolium salts substituted on the heterocyclic ring have been synthesised by the condensation of 3-alkyl-2-methylbenzothiazolium halides with 4-substituted benzaldehydes. The intramolecular charge transfer from the electron-donor substituent to the benzothiazolium ring is a typical feature of the prepared compounds. This type of benzothiazolium derivatives can be used as pharmaceutical substances as well as compounds with nonlinear optical response. Antimicrobial in vitro activity was determined and the influence of substituents has been evaluated. The substituents on the heterocyclic ring in positions 5 and 6 do not increase the biological activity significantly.
Journal of Physical Chemistry C, Dec 1, 2014
The excited state and electron injection dynamics of three new organic sensitizers, comprising a ... more The excited state and electron injection dynamics of three new organic sensitizers, comprising a triphenylamine moiety connected by an ethenylene (C−C double-bond) or ethynylene (C−C triple-bond) π-spacer to an electron-withdrawing benzothiazole bearing a cyanoacrylic acid anchoring group, have been studied using a combination of steady-state and femtosecond-resolved spectroscopies. The measurements were carried out for the three dyes in predominantly neutral and completely deprotonated forms in liquid solutions and bound on nanocrystalline TiO 2 and Al 2 O 3 thin films. In addition, quantum-chemical calculations were performed to predict absorption spectra of the sensitizers and their corresponding cation radicals. Timeresolved fluorescence (TRF) measurements on TiO 2 indicate that electron injection takes place on a <0.2 ps time scale. Transient electronic absorption (TA) measurements provide evidence for the formation of radical cations not only in dye-sensitized TiO 2 films but also in Al 2 O 3 ones. The cation lifetime in Al 2 O 3 is significantly shorter compared to TiO 2 , indicating a faster recombination of injected electrons with the dye cations. In addition, the ground-state bleach band in dye-sensitized TiO 2 films experiences a gradual red-shift, which is indicative of a transient Stark effect. Finally, femtosecond transient absorption measurements in the IR region point to an ultrafast generation of injected electrons for all dyes. A faster recombination of the injected electrons with the dye cations is observed for the sensitizer decorated with auxiliary electron-donating methoxy groups on the triphenylamine moiety.
ChemPhysChem, May 22, 2023
Journal of Physical Chemistry C, Aug 7, 2018
ChemInform, Mar 22, 2005
For Abstract see ChemInform Abstract in Full Text.
Synthetic Communications, 2004
ABSTRACT Synthesis of N‐(4‐methylpentane‐2‐yl)‐N′‐[2‐(2‐phenylpropane‐2‐yl)]‐benzene1,4‐diamine i... more ABSTRACT Synthesis of N‐(4‐methylpentane‐2‐yl)‐N′‐[2‐(2‐phenylpropane‐2‐yl)]‐benzene1,4‐diamine in four steps starting from methyl 2‐bromobenzoate is described. Chromatographically homogeneous product was prepared in 25% overall yield.
Magnetic Resonance in Chemistry, 2007
The 15 N as well as 13 C and 1 H chemical shifts of eight push-pull benzothiazolium iodides with ... more The 15 N as well as 13 C and 1 H chemical shifts of eight push-pull benzothiazolium iodides with various p-conjugated chains between dimethylamino group and benzothiazolium moiety have been determined by NMR spectroscopy at the natural-abundance level of all nuclei in DMSO-d 6 solution. In general, the quaternary benzothiazolium nitrogen is more shielded [d(15 N-3) vary between −241.3 and −201.9 ppm] with respect to parent 3-methylbenzothiazolium iodide [d(15 N-3) = −183.8 ppm], depending on the length and constitution of the p-conjugated bridge. A larger variation in 15 N chemical shifts is observed on dimethylamino nitrogen, which covers the range of −323.3 to −257.2 ppm. The effect of p-conjugation degree has a less pronounced influence on 13 C and 1 H chemical shifts. Experimental data are interpreted by means of density functional theory (DFT) calculations. Reasonable agreement between theoretical and experimental 15 N NMR chemical shifts was found, particularly when performing calculations with hybrid exchange-correlation functionals. A better accord with experiment is achieved by utilizing a polarizable continuum model (PCM) along with an explicit treatment of hydrogenbonding between the solute and the water present in dimethylsulfoxide (DMSO). Finally, 13 C and 1 H NMR spectra were computed and analysed in order to compare them with available experimental data.
Synthesis, Dec 22, 2004
ABSTRACT The hitherto unknown 6-dimethylaminobenzothiazole-2-carbaldehyde was prepared as a start... more ABSTRACT The hitherto unknown 6-dimethylaminobenzothiazole-2-carbaldehyde was prepared as a starting compound for the synthesis of novel push-pull benzothiazole derivatives with reverse polarity. These compounds are substituted at the 2-position by strong electron-acceptor groups and at the 6-position by NMe2 as strong electron-donor. The new method for synthesis of 6-dimethylaminobenzothiazole involved the successful use of sonochemical reductive methylation. Expected non-linear optical properties of target molecules were studied by EFISH method.
ChemPlusChem, 2007
The synthesis of new benzothiazole push-pull systems as candidates for NLO-phores is described. S... more The synthesis of new benzothiazole push-pull systems as candidates for NLO-phores is described. Spectral (UV/VIS and solvatochromic) and theoretical studies (electronic properties based on semiempirical AM1 and PM3 methods) of the prepared compounds were carried out. The structure and physico-chemical parameters affecting the push-pull character and intramolecular charge transfer (ICT) of the studied compounds have been investigated and compounds with enhanced hyperpolarizability β have been predicted. The benzothiazolium salts were found to be much more effective NLO-phores in comparison with the corresponding neutral benzothiazoles. The 4-NPh2 group is the most effective donor. The extension of conjugated bridge improves the studied NLO characteristics. An additional acceptor group bonded to the heterocycle causes a red shift of λmax but does not increase hyperpolarizability.
ChemInform, Jan 8, 2008
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Physical Chemistry Chemical Physics
Unsymmetrical benzothiazole based dithienylethenes represent P-type photoswitches with high therm... more Unsymmetrical benzothiazole based dithienylethenes represent P-type photoswitches with high thermal stability, efficient photocyclization, good resistance to photodegradation and non-destructive readout possibility of coded information using vibrational spectroscopy.
Our contribution is focused on broadening of the spectrum of available non-linear optical (NLO)-p... more Our contribution is focused on broadening of the spectrum of available non-linear optical (NLO)-phores (contrast agents for nonlinear optical microscopy) by design and synthesis of new organic dyes with appropriate optical properties. One of the main pre-requisites of microscopy utilizing non-linear excitation is the existence of molecules that are able to provide NLO response for the second-harmonic generation (SHG) or for the two-photon excited fluorescence (TPEF). Many molecules naturally occurring in living tissue such as collagens or NAD(P)H were successfully used in this regard, but there is a natural interest in broadening of the spectrum of available NLO-phores. Gathered results confirm applicability of the newly synthesized dyes as new potential NLO-phores for confocal laser scanning microscopy with nonlinear excitation in rat aorta.
The Journal of Physical Chemistry C, 2018
Chemical Physics Letters, 2018
Two-photon absorption (TPA) cross sections of conjugated donor-p-acceptor dipolar structures cont... more Two-photon absorption (TPA) cross sections of conjugated donor-p-acceptor dipolar structures containing benzothiazole or benzobisthiazolium moieties are determined in a broad spectral range from 700 nm to 1000 nm using two-photon induced fluorescence technique. The TPA cross section values range from 150 GM to 4600 GM. The largest values are observed in near-infrared region. The dipolar derivative of benzothiazole has the largest TPA cross section of 4600 GM at wavelength of 890 nm. A combination of the large TPA in the near-infrared region and the high emission quantum yield makes these compounds excellent candidates for two-photon fluorescence microscopy.
The Journal of Physical Chemistry C, 2010
A series of push-pull chromophores comprising a dimethylamino or diphenylamino electron-donating ... more A series of push-pull chromophores comprising a dimethylamino or diphenylamino electron-donating functionality and a cationic benzothiazolium acceptor with an additional electron-withdrawing group (EWG) NO 2 or CN) at various positions of the heterocyclic benzene ring have been synthesized and comprehensively investigated for their linear and quadratic nonlinear optical (NLO) properties by means of UV-visible spectroscopy and hyper-Rayleigh scattering, as well as by quantum-chemical calculations at different levels of theory (B3LYP, CAM-B3LYP, MP2, and RI-CC2). In general, all chromophores under study display large static quadratic hyperpolarizabilities 0 , comparable to or in most cases even larger than their conventional stilbazolium-containing analogues, which makes these systems attractive for practical NLO applications. The introduction of an auxiliary EWG into the heterocyclic benzene ring causes a substantial red shift of the intramolecular charge-transfer band. Still, at the same time, this modification of the structure reduces the 0 values in systems with longer π-conjugated spacers. The unexpected negative impact of the EWG substitution pattern on the quadratic NLO activity is rationalized by quantum-chemical calculations as well as by experimentally determined one-photon absorption characteristics and is discussed in detail. Furthermore, computational studies revealed that push-pull benzothiazolium dyes with a "reverse" polarity with respect to the commonly used one would be a more worthwhile target for synthesis, because of their enhanced NLO response due to the positive effect of an auxiliary electron-withdrawing group.
Synthetic Communications, 2004
ABSTRACT Synthesis of N‐(4‐methylpentane‐2‐yl)‐N′‐[2‐(2‐phenylpropane‐2‐yl)]‐benzene1,4‐diamine i... more ABSTRACT Synthesis of N‐(4‐methylpentane‐2‐yl)‐N′‐[2‐(2‐phenylpropane‐2‐yl)]‐benzene1,4‐diamine in four steps starting from methyl 2‐bromobenzoate is described. Chromatographically homogeneous product was prepared in 25% overall yield.
Journal of Physical Chemistry A, Oct 15, 2019
The Journal of Physical Chemistry, 2018
Arkivoc, Apr 4, 2008
New 2-styryl benzothiazolium salts substituted on the heterocyclic ring have been synthesised by ... more New 2-styryl benzothiazolium salts substituted on the heterocyclic ring have been synthesised by the condensation of 3-alkyl-2-methylbenzothiazolium halides with 4-substituted benzaldehydes. The intramolecular charge transfer from the electron-donor substituent to the benzothiazolium ring is a typical feature of the prepared compounds. This type of benzothiazolium derivatives can be used as pharmaceutical substances as well as compounds with nonlinear optical response. Antimicrobial in vitro activity was determined and the influence of substituents has been evaluated. The substituents on the heterocyclic ring in positions 5 and 6 do not increase the biological activity significantly.
Journal of Physical Chemistry C, Dec 1, 2014
The excited state and electron injection dynamics of three new organic sensitizers, comprising a ... more The excited state and electron injection dynamics of three new organic sensitizers, comprising a triphenylamine moiety connected by an ethenylene (C−C double-bond) or ethynylene (C−C triple-bond) π-spacer to an electron-withdrawing benzothiazole bearing a cyanoacrylic acid anchoring group, have been studied using a combination of steady-state and femtosecond-resolved spectroscopies. The measurements were carried out for the three dyes in predominantly neutral and completely deprotonated forms in liquid solutions and bound on nanocrystalline TiO 2 and Al 2 O 3 thin films. In addition, quantum-chemical calculations were performed to predict absorption spectra of the sensitizers and their corresponding cation radicals. Timeresolved fluorescence (TRF) measurements on TiO 2 indicate that electron injection takes place on a <0.2 ps time scale. Transient electronic absorption (TA) measurements provide evidence for the formation of radical cations not only in dye-sensitized TiO 2 films but also in Al 2 O 3 ones. The cation lifetime in Al 2 O 3 is significantly shorter compared to TiO 2 , indicating a faster recombination of injected electrons with the dye cations. In addition, the ground-state bleach band in dye-sensitized TiO 2 films experiences a gradual red-shift, which is indicative of a transient Stark effect. Finally, femtosecond transient absorption measurements in the IR region point to an ultrafast generation of injected electrons for all dyes. A faster recombination of the injected electrons with the dye cations is observed for the sensitizer decorated with auxiliary electron-donating methoxy groups on the triphenylamine moiety.
ChemPhysChem, May 22, 2023
Journal of Physical Chemistry C, Aug 7, 2018
ChemInform, Mar 22, 2005
For Abstract see ChemInform Abstract in Full Text.
Synthetic Communications, 2004
ABSTRACT Synthesis of N‐(4‐methylpentane‐2‐yl)‐N′‐[2‐(2‐phenylpropane‐2‐yl)]‐benzene1,4‐diamine i... more ABSTRACT Synthesis of N‐(4‐methylpentane‐2‐yl)‐N′‐[2‐(2‐phenylpropane‐2‐yl)]‐benzene1,4‐diamine in four steps starting from methyl 2‐bromobenzoate is described. Chromatographically homogeneous product was prepared in 25% overall yield.
Magnetic Resonance in Chemistry, 2007
The 15 N as well as 13 C and 1 H chemical shifts of eight push-pull benzothiazolium iodides with ... more The 15 N as well as 13 C and 1 H chemical shifts of eight push-pull benzothiazolium iodides with various p-conjugated chains between dimethylamino group and benzothiazolium moiety have been determined by NMR spectroscopy at the natural-abundance level of all nuclei in DMSO-d 6 solution. In general, the quaternary benzothiazolium nitrogen is more shielded [d(15 N-3) vary between −241.3 and −201.9 ppm] with respect to parent 3-methylbenzothiazolium iodide [d(15 N-3) = −183.8 ppm], depending on the length and constitution of the p-conjugated bridge. A larger variation in 15 N chemical shifts is observed on dimethylamino nitrogen, which covers the range of −323.3 to −257.2 ppm. The effect of p-conjugation degree has a less pronounced influence on 13 C and 1 H chemical shifts. Experimental data are interpreted by means of density functional theory (DFT) calculations. Reasonable agreement between theoretical and experimental 15 N NMR chemical shifts was found, particularly when performing calculations with hybrid exchange-correlation functionals. A better accord with experiment is achieved by utilizing a polarizable continuum model (PCM) along with an explicit treatment of hydrogenbonding between the solute and the water present in dimethylsulfoxide (DMSO). Finally, 13 C and 1 H NMR spectra were computed and analysed in order to compare them with available experimental data.
Synthesis, Dec 22, 2004
ABSTRACT The hitherto unknown 6-dimethylaminobenzothiazole-2-carbaldehyde was prepared as a start... more ABSTRACT The hitherto unknown 6-dimethylaminobenzothiazole-2-carbaldehyde was prepared as a starting compound for the synthesis of novel push-pull benzothiazole derivatives with reverse polarity. These compounds are substituted at the 2-position by strong electron-acceptor groups and at the 6-position by NMe2 as strong electron-donor. The new method for synthesis of 6-dimethylaminobenzothiazole involved the successful use of sonochemical reductive methylation. Expected non-linear optical properties of target molecules were studied by EFISH method.
ChemPlusChem, 2007
The synthesis of new benzothiazole push-pull systems as candidates for NLO-phores is described. S... more The synthesis of new benzothiazole push-pull systems as candidates for NLO-phores is described. Spectral (UV/VIS and solvatochromic) and theoretical studies (electronic properties based on semiempirical AM1 and PM3 methods) of the prepared compounds were carried out. The structure and physico-chemical parameters affecting the push-pull character and intramolecular charge transfer (ICT) of the studied compounds have been investigated and compounds with enhanced hyperpolarizability β have been predicted. The benzothiazolium salts were found to be much more effective NLO-phores in comparison with the corresponding neutral benzothiazoles. The 4-NPh2 group is the most effective donor. The extension of conjugated bridge improves the studied NLO characteristics. An additional acceptor group bonded to the heterocycle causes a red shift of λmax but does not increase hyperpolarizability.
ChemInform, Jan 8, 2008
ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was e... more ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 200 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.
Physical Chemistry Chemical Physics
Unsymmetrical benzothiazole based dithienylethenes represent P-type photoswitches with high therm... more Unsymmetrical benzothiazole based dithienylethenes represent P-type photoswitches with high thermal stability, efficient photocyclization, good resistance to photodegradation and non-destructive readout possibility of coded information using vibrational spectroscopy.
Our contribution is focused on broadening of the spectrum of available non-linear optical (NLO)-p... more Our contribution is focused on broadening of the spectrum of available non-linear optical (NLO)-phores (contrast agents for nonlinear optical microscopy) by design and synthesis of new organic dyes with appropriate optical properties. One of the main pre-requisites of microscopy utilizing non-linear excitation is the existence of molecules that are able to provide NLO response for the second-harmonic generation (SHG) or for the two-photon excited fluorescence (TPEF). Many molecules naturally occurring in living tissue such as collagens or NAD(P)H were successfully used in this regard, but there is a natural interest in broadening of the spectrum of available NLO-phores. Gathered results confirm applicability of the newly synthesized dyes as new potential NLO-phores for confocal laser scanning microscopy with nonlinear excitation in rat aorta.
The Journal of Physical Chemistry C, 2018
Chemical Physics Letters, 2018
Two-photon absorption (TPA) cross sections of conjugated donor-p-acceptor dipolar structures cont... more Two-photon absorption (TPA) cross sections of conjugated donor-p-acceptor dipolar structures containing benzothiazole or benzobisthiazolium moieties are determined in a broad spectral range from 700 nm to 1000 nm using two-photon induced fluorescence technique. The TPA cross section values range from 150 GM to 4600 GM. The largest values are observed in near-infrared region. The dipolar derivative of benzothiazole has the largest TPA cross section of 4600 GM at wavelength of 890 nm. A combination of the large TPA in the near-infrared region and the high emission quantum yield makes these compounds excellent candidates for two-photon fluorescence microscopy.
The Journal of Physical Chemistry C, 2010
A series of push-pull chromophores comprising a dimethylamino or diphenylamino electron-donating ... more A series of push-pull chromophores comprising a dimethylamino or diphenylamino electron-donating functionality and a cationic benzothiazolium acceptor with an additional electron-withdrawing group (EWG) NO 2 or CN) at various positions of the heterocyclic benzene ring have been synthesized and comprehensively investigated for their linear and quadratic nonlinear optical (NLO) properties by means of UV-visible spectroscopy and hyper-Rayleigh scattering, as well as by quantum-chemical calculations at different levels of theory (B3LYP, CAM-B3LYP, MP2, and RI-CC2). In general, all chromophores under study display large static quadratic hyperpolarizabilities 0 , comparable to or in most cases even larger than their conventional stilbazolium-containing analogues, which makes these systems attractive for practical NLO applications. The introduction of an auxiliary EWG into the heterocyclic benzene ring causes a substantial red shift of the intramolecular charge-transfer band. Still, at the same time, this modification of the structure reduces the 0 values in systems with longer π-conjugated spacers. The unexpected negative impact of the EWG substitution pattern on the quadratic NLO activity is rationalized by quantum-chemical calculations as well as by experimentally determined one-photon absorption characteristics and is discussed in detail. Furthermore, computational studies revealed that push-pull benzothiazolium dyes with a "reverse" polarity with respect to the commonly used one would be a more worthwhile target for synthesis, because of their enhanced NLO response due to the positive effect of an auxiliary electron-withdrawing group.
Synthetic Communications, 2004
ABSTRACT Synthesis of N‐(4‐methylpentane‐2‐yl)‐N′‐[2‐(2‐phenylpropane‐2‐yl)]‐benzene1,4‐diamine i... more ABSTRACT Synthesis of N‐(4‐methylpentane‐2‐yl)‐N′‐[2‐(2‐phenylpropane‐2‐yl)]‐benzene1,4‐diamine in four steps starting from methyl 2‐bromobenzoate is described. Chromatographically homogeneous product was prepared in 25% overall yield.