Petr Zimcik

Charles University in Prague, Praha, Praha, Czech Republic

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Publications (41)91.16 Total impact

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    ABSTRACT: Conditions for the Newman-Kwart rearrangement of phenols into thiophenols were investigated in relation to the bulkiness of substituents at the 2 and 6 positions of the starting phenol derivative with an emphasis on eliminating side reactions. Thiophenols with different 2,6-disubstitution patterns (including hydrogen, methyl, isopropyl or tert-butyl groups) were used for the synthesis of 5,6-bis(arylsulfanyl)pyrazine-2,3-dicarbonitriles that underwent cyclotetramerization leading to the corresponding zinc tetrapyrazinoporphyrazines (TPyzPz), aza-analogues of phthalocyanines. Several methods for the cyclotetramerization were attempted to eliminate problematic side reactions such as the exchange the arylsulfanyls with alkoxides from the initiator. Magnesium butoxide was found as the most suitable cyclotetramerization agent and afforded TPyzPzs in reasonable yields of approximately 30 % under mild conditions. The varying arrangements of the peripheral substitutions resulting from the different bulkiness of the substituents were demonstrated by the X-ray structures of the pyrazine-2,3-dicarbonitriles. The prepared zinc arylsulfanyl TPyzPzs showed an absorption maximum at a Q band over 650 nm, fluorescence quantum yields between 0.078-0.20, and singlet oxygen quantum yields ranging 0.58-0.69. TPyzPzs with isopropyl groups were found to be the best derivatives in this series as they combined facile cyclotetramerization, no aggregation and good photophysical properties, which makes them potentially suitable for photodynamic therapy.
    The Journal of Organic Chemistry 02/2014; · 4.56 Impact Factor
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    ABSTRACT: A series of unsymmetrical tetrapyrazinoporphyrazines (TPyzPzs) from the group of azaphthalocyanines with one peripherally attached amino substituent (donor) were synthesized, and their photophysical properties (fluorescence quantum yield and singlet oxygen quantum yield) were determined. The synthesized TPyzPzs were expected to undergo intramolecular charge transfer (ICT) as the main pathway for deactivating their excited states. Several structural factors were found to play a critical role in ICT efficiency. The substituent in the ortho position to the donor center significantly influences the ICT, with tert-butylsulfanyl and butoxy substituents inducing the strongest ICTs, whereas chloro, methyl, phenyl, and hydrogen substituents in this position reduce the efficiency. The strength of the donor positively influences the ICT efficiency and correlates well with the oxidation potential of the amines used as the substituents on the TPyzPz as follows: n-butylamine < N,N-diethylamine < aniline < phenothiazine. The ICT (with conjugated donors and acceptors) in the TPyzPz also proved to be much stronger than a photoinduced electron transfer in which the donor and the acceptor are connected through an aliphatic linker.
    Physical Chemistry Chemical Physics 02/2014; · 4.20 Impact Factor
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    ABSTRACT: Newly synthesized zinc phthalocyanine bearing sixteen quaternized imidazolyl moieties on the periphery displays high water-solubility, lack of aggregation and high singlet oxygen quantum yield in water (ΦΔ > 0.33). The in vitro tests indicated excellent anticancer photodynamic activity (EC50 = 36.7 nM) and low dark toxicity to non-cancerous cells (TC50 = 395 μM).
    Chemical Communications 09/2013; · 6.38 Impact Factor
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    ABSTRACT: Light up a red crown: Chelation of sodium and potassium cations by aza[15]crown-5 switches on strong red fluorescence in azaphthalocyanines. It is due to an inhibition of ultrafast intramolecular charge transfer by coordination of the cations to donor center. Sodium cations fit well into a cavity of the recognition moiety, while potassium forms supramolecular assemblies of azaphthalocyanines with 1:2 stoichiometry.
    Chemistry 03/2013; · 5.93 Impact Factor
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    ABSTRACT: The formation of self-assemblies between CdSe quantum dots (QDs) and Zn phthalocyanines (Pc) and azaphthalocyanines (AzaPc) bearing alkylsulfanyl substituents and the photophysical properties of these assemblies were studied using both steady-state and time-resolved luminescence/absorption spectroscopy. The formation of the self-assemblies was accompanied by a blue shift of the Q band of the dyes and by a quenching of the CdSe QDs luminescence. The largest spectral shift of the Q-band was approximately 7 nm and was observed for pentan-3-ylsulfanyl-functionalised phthalocyanine (). Assuming a 1 : 1 stoichiometry, the calculated binding constant was 4 × 10(4) M(-1). Pc substituted with the bulky tert-butylsulfanyl groups () exhibited a smaller shift of the Q band. The quenching of the CdSe QDs luminescence by was more effective than that observed for . The results indicated that the luminescence quenching may be due to a photoinduced charge transfer between or and the CdSe QDs. In contrast, the AzaPc () with the same substituents as had little effect on the QDs luminescence. For all cases, we found an inefficient resonance energy transfer between the attached dyes and the CdSe QD. The formation of the self-assemblies had negligible effects on the photogeneration of the singlet oxygen, O(2)((1)Δ(g)), that was fully controlled only by the absorption of the light by the macrocycles.
    Photochemical and Photobiological Sciences 01/2013; · 2.92 Impact Factor
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    ABSTRACT: Intramolecular charge transfer (ICT) was studied on a series of magnesium, metal-free and zinc complexes of unsymmetrical tetrapyrazinoporphyrazines and tribenzopyrazinoporphyrazines bearing two dialkylamino substituents (donors) and six alkylsulfanyl or aryloxy substituents (non-donors). The dialkylamino substituents were responsible for ICT that deactivated excited states and led to considerable decrease of fluorescence and singlet oxygen quantum yields. Photophysical and photochemical properties were compared to corresponding macrocycles that do not bear any donor centers. The data showed high feasibility of ICT in the tetrapyrazinoporphyrazine macrocycle and significantly lower efficiency of this deactivation process in the tribenzopyrazinoporphyrazine type molecules. Considerable effect of non-donor peripheral substituents on ICT was also described. The results imply that tetrapyrazinoporphyrazines may be more suitable for development of new molecules investigated in applications based on ICT.
    Dalton Transactions 07/2012; 41(38):11651-6. · 3.81 Impact Factor
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    ABSTRACT: A series of azaphthalocyanines (AzaPc) bearing one, two, four or eight isopropylidene-protected galactosyl units was prepared by azide-alkyne click reaction or by classical Pc template cyclotetramerization of the corresponding dicyanopyrazine and AzaPc properties important for photodynamic therapy were compared. All compounds absorbed at long wavelengths (above 650 nm) and belonged to strong singlet oxygen producers (Φ(Δ) = 0.58-0.64) retaining significant fluorescence emission (Φ(F) = 0.026-0.23). The only exception was the compound with four isopropyliden-protected galactosyl units where partial aggregation was observed. Removal of protecting groups increased the polar character of all AzaPc. However, only AzaPc bearing eight galactoses was found to be water-soluble (105 mg mL(-1)) but noticeably aggregated in water as well as in organic solvents (DMF, DMSO). Amphiphilic AzaPc bearing one deprotected galactose was incorporated into the lipidic bilayer of liposomes in a nonaggregated form. Liposomes may therefore be a suitable delivery system for this amphiphilic photosensitizer.
    Dalton Transactions 07/2012; 41(35):10596-604. · 3.81 Impact Factor
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    ABSTRACT: The presented work deals with synthesis and isolation of constitutional isomers of triazolo-fused azaphthalocyanines. Distribution of the isomers did not follow the statistical calculations due to steric effects of the substituents preferring the least sterically stressed C(4h) isomer.
    Chemical Communications 03/2012; 48(36):4326-8. · 6.38 Impact Factor
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    ABSTRACT: Magnesium(II), zinc(II), and metal-free phthalocyanines (Pcs) and azaphthalocyanines (AzaPcs) containing alkylsulfanyl, aryloxy, and dialkylamino peripheral substituents have been synthesized. The complexation of magnesium(II) by metal-free Pcs and AzaPcs has been studied in detail to determine the optimal reaction conditions necessary to ensure a complete conversion. Photophysical and photochemical measurements in tetrahydrofuran showed that magnesium(II) AzaPcs with aryloxy and alkylsulfanyl substituents have excellent fluorescent properties (Φ(F) up to 0.73) and that the corresponding zinc(II) Pcs are efficient singlet oxygen producers (Φ(Δ) up to 0.68). The presence of dialkylamino substituents causes intramolecular charge transfer within the molecule that competes with fluorescence and singlet oxygen formation. Alkylsulfanyl MgAzaPc and ZnAzaPc were the most photostable compounds among the series of studied derivatives. In addition, high molar absorption coefficients (ε ∼ 300,000 M(-1) cm(-1)), absorption (λ(max) ∼ 650 nm), and emission (λ(em) ∼ 660 nm, high Φ(F)) in the red region suggest that these molecules are potential fluorescent probes that are superior to the commercial red cyanine dye Cy5. MgAzaPc, when incorporated into lipidic bilayers of liposomes, maintains excellent fluorescence properties (Φ(F) = 0.64). Water-soluble MgAzaPc with quaternary ammonium peripheral substituents retained a high fluorescence quantum yield even in water (Φ(F) = 0.25). The described properties show that magnesium(II) AzaPcs are excellent red-emitting fluorophores with potential applications as fluorescent probes in sensing or in vitro imaging applications.
    Inorganic Chemistry 03/2012; 51(7):4215-23. · 4.59 Impact Factor
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    ABSTRACT: a b s t r a c t A series of zinc phthalocyanines and corresponding aza-analogues azaphthalocyanines substituted with peripheral 2,6-diisopropylphenoxy substituents containing different functional groups (Br, OCH 3 , and OH) were synthesized and their photophysical properties were investigated. UVevis and 1 H NMR analyses confirmed the non-aggregation behavior of the prepared complexes in most organic solvents. All investigated compounds showed good photophysical and photochemical properties in THF and DMF with F F values in the range of 0.22e0.44 and F D values ranging between 0.42 and 0.57. Hydroxylated compounds showed good solubility in polar solvents including ethanol, methanol, acetone and even in aqueous ethanol mixtures. Absorption spectra in aqueous ethanol indicated presence of only monomers even at very low ethanol content in water (0.5% of ethanol in water). Despite this, no fluorescence occurred from approximately 50% of ethanol in water suggesting presence of aggregates that do not differ from monomers in a shape of absorption spectra.
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    ABSTRACT: New unsymmetrical zinc azaphthalocyanines, bearing one substituted aniline as a peripheral substituent, were prepared by using a statistical condensation approach. Both fluorescence and singlet oxygen quantum yields were extremely low in DMF (Φ(F)<0.01, Φ(Δ)<0.02, respectively), but increased after the addition of sulfuric acid, reaching values comparable to controls without aniline substituents (Φ(F)=0.22-0.29, Φ(Δ)=0.40-0.59, respectively). This behavior was attributed to the deactivation of excited states by intramolecular charge transfer from a donor site (aniline), which was blocked after protonation in acidic media. In the protonated form, all of the compounds efficiently emitted light with λ(em) in the region of 662-675 nm. The investigated compounds were anchored to dioleoylphosphatidylcholine (DOPC) unilamellar vesicles and showed response to buffer pH. They were highly fluorescent at low pH values and almost nonfluorescent in neutral solutions. The pK(a) values were determined in DOPC vesicles and ranged between 2.2 and 4.2.
    Chemistry 11/2011; 17(50):14273-82. · 5.93 Impact Factor
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    ABSTRACT: An approach leading to unsymmetrical azaphthalocyanines (AzaPcs) bearing one aryloxy and seven butoxy substituents on the periphery is described. Several cyclotetramerization methods were tested, including the template effect of a metal salt in a melt/solution and the Linstead method, but only one was found to be suitable for the isolation of unsymmetrical alkyloxy/aryloxy-AzaPcs. Undesired transetherification with alkoxides, which is common with these types of compounds, was considered to be an advantage in this approach, and an unsymmetrical AzaPc was isolated in 10 % yield. An analysis of the transetherification process is also described. Unsymmetrical zinc(II) and magnesium(II) AzaPcs showed excellent spectral properties (λmax = 620 nm; ϵ = 1.5–2.2 × 105 dm3mol–1 cm–1) as well as promising singlet oxygen (ΦΔ = 0.44 and 0.26, respectively) and fluorescence quantum yields (ΦF = 0.50 and 0.65, respectively). The metal-free derivative (λmax = 603 and 640 nm; ϵ = 0.80 and 1.2 × 105 dm3 mol–1 cm–1) dissipated energy in a different way, and the ΦΔ and ΦF values were one order of magnitude smaller (0.030 and 0.053, respectively). All the parameters were comparable to the corresponding symmetrical AzaPcs containing eight butoxy substituents, which suggests that an unsymmetrical composition of AzaPc on the periphery has no negative effect on the photophysical or photochemical properties.
    Annalen der Chemie und Pharmacie 10/2011; 2011(29). · 3.10 Impact Factor
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    ABSTRACT: New unsymmetrical zinc azaphthalocyanine (AzaPc) was synthesized using statistical condensation of two precursors. Postsynthetic modifications led to incorporation of azide group that efficiently underwent Cu(I)-catalyzed azide/alkyne 1,3-dipolar cycloaddition with terminal alkyne on a solid phase. The modified solid phase was then used for synthesis of oligodeoxyribonucletides labeled with AzaPc. DNA hybridization assays confirmed high quenching efficiency (QE>96%) of zinc AzaPc quencher with six different fluorophores ranging in emission maxima from 517 nm to 701 nm (FAM, HEX, Cy3, Cy3.5, Cy5, and Cy5.5).Graphical abstract
    Tetrahedron. 01/2011; 67(33):5956-5963.
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    ABSTRACT: Mono-, di-, tri- and tetracarboxy-substituted metal-free azaphthalocyanines (AzaPc) were synthesized from 5,6-bis(diethylamino)pyrazine-2,3-dicarbonitrile and 6-(5,6-dicyano-3-(diethylamino)pyrazin-2-ylamino)hexanoic acid using a statistical condensation approach. AzaPc bearing eight diethylamino peripheral substituents was also isolated from the mixture. Analysis of the distribution of congeners in the statistical mixture using optimized HPLC method (Phenomenex Synergy RP Fusion column, acetonitrile/tetrahydrofuran/water (pH 5.5) 50:20:30) was performed. The analysis showed optimal ratios of starting materials to be 3:1 for AAAB, 1:3 for ABBB and 1:1 for AABB/ABAB types of the congeners. The distribution of the congeners corresponded well with calculated values indicating similar reactivity of both starting materials and no sterical constraint between adjacent isoindole units in the AzaPc ring. All investigated AzaPc showed no fluorescence, extremely low singlet oxygen quantum yields (Φ∆ < 0.005) in monomeric form and strong absorption in a wide range from 300 nm to almost 700 nm. Such properties are highly promising for future investigation of these compounds as dark quenchers of fluorescence in DNA hybridization probes.Highlights► Metal-free azaphthalocyanines with one to four peripheral carboxy substituents. ► Ratio of congeners from statistical condensation optimized by HPLC. ► Compounds exerted no fluorescence and very low singlet oxygen quantum yields. ► Strong absorption in a wide range from 300 nm to almost 700 nm for each compound. ► Properties of azaphthalocyanines are promising for dark quenchers of fluorescence.
    Dyes and Pigments 01/2011; 91(2):112-119. · 3.53 Impact Factor
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    ABSTRACT: In this work, we summarize the recent knowledge about the syntheses, UV-vis absorption properties, aggregation, protonation and deprotonation of macrocycle and singlet oxygen and fluorescence quantum yields in the group of azaphthalocyanines bearing pyrazine rings in their conjugated system. Precursors (pyrazine-2,3-dicarbonitriles) for tetramerization are usually built up by condensation from aliphatic starting materials thus enabling peripheral substitutions sometimes not available for phthalocyanines (Pc). Conditions of tetramerizations are discussed in the article too. Although tetrapyrazinoporphyrazines (TPyzPA) suffer from the hypsochromic shift comparing to corresponding Pc, several types of peripheral substituents can induce important bathochromic shift and eliminate this disadvantage. TPyzPA macrocycle tends to higher aggregation comparing to Pc molecules and a lot of aggregation inhibiting substituents have been developed. Protonation of the TPyzPA macrocycle in acidic media starts on azomethine nitrogens and at higher concentrations of acid also pyrazine nitrogens accept the proton. The central hydrogens in metal-free compounds are acidic (N-acids) and the macrocycle can be deprotonated in basic solutions. Singlet oxygen production as well as fluorescence emission are strongly dependent on peripheral substituents, namely on the heteroatoms connecting the core with the substituents.
    ChemInform 11/2010; 41(45).
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    ABSTRACT: Hydrophobic nonaggregating metal-free azaphthalocyanines (AzaPc) of the tetrapyrazinoporphyrazine type were synthesized, characterized, and used for oligonucleotide labeling. Both 3'-end and 5'-end labeling methods using solid phase synthesis suitable for automatic processes in the DNA/RNA synthesizer were developed. The hydrophobic character of AzaPc enabled the anchoring of the conjugates on reverse phase of the oligonucleotide purification cartridge, thus enabling their simple purification. AzaPc did not show any fluorescence and extremely low singlet oxygen quantum yields (Φ(Δ) = 0.015-0.018 in DMF) in a monomeric state due to ultrafast intramolecular charge transfer. That is why they were investigated as a new dark quencher structural type. They profit particularly from absorption in a wide range of wavelengths (300-740 nm) that covers all fluorophores used in hybridization assays nowadays. As an example, quenching efficiency was evaluated in a simple hybridization assay using monolabeled probes. AzaPc-based probes efficiently quenched both fluorescein and Cy5 fluorescence by both resonance energy transfer and contact quenching. The results were compared with three established dark quenchers, and the AzaPc exerted better (BHQ-1 and BHQ-2) or comparable (BBQ-650) quenching efficiencies for both fluorophores.
    Bioconjugate Chemistry 10/2010; 21(10):1872-9. · 4.58 Impact Factor
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    ABSTRACT: A series of octasubstituted zinc(II) tetrapyrazinoporphyrazines (TPyzPz), aza-analogues of phthalocyanines, differing in the number of peripheral N,N-diethylamino (n = 0-8) and tert-butylsulfanyl substituents (m = 8-n) has been synthesized. All possible congeners were characterized including adjacent and opposite isomers. Steady-state (UV-vis, fluorescence) and time-resolved (fluorescence, femtosecond transient absorption) spectroscopies, redox and photochemical (singlet oxygen formation) properties were investigated and compared. The peripheral tertiary amino substituents (donor) induce a new competitive relaxation pathway to fluorescence and intersystem crossing due to the mixing of the first excited state S(1) of the TPyzPz macrocycle with a nearby intramolecular charge transfer (ICT) state. The fluorescence quantum yield and fluorescence lifetime of 6Zn bearing one N,N-diethylamino substituent (n = 1, m = 7) decreased with increasing solvent polarity, while the same observables of 5Zn with no donor centre (n = 0, m = 8) were not affected. Protonation of the N,N-diethylamino substituent in 6Zn led to a strong increase of the fluorescence intensity. The cyclic voltammetry data, the steady-state and time-resolved emission and transient absorption studies revealed strong electronic coupling between the TPyzPz moiety and N,N-diethylamino substituents. ICT is an extremely rapid process occurring with a time constant of 10 ps and 7 ps in 6Zn (n = 1, m = 7) and 11Zn (n = 8, m = 0) in pyridine, respectively. The ICT efficiency decreased in non-polar solvents. The presence of two N,N-diethylamino substituents in 7Zn (n = 2, m = 6) considerably quenched the S(1) states in pyridine (polar, coordinating), toluene (non-polar, non-coordinating) and toluene-1% pyridine (v/v) (non-polar, coordinating). The photophysical properties of compounds with more donor substituents on the periphery (n > 2, m < 6) were similar to those of 7Zn.
    Physical Chemistry Chemical Physics 03/2010; 12(11):2555-63. · 4.20 Impact Factor
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    ABSTRACT: Octasubstituted zinc tetrapyrazinoporphyrazines bearing butyloxy, octyloxy, 2,6-diisopropylphenoxy and 4-(hydroxymethyl)phenoxy substituents were synthesized from the corresponding 5,6-disubstituted pyrazine-2,3-dicarbonitriles using Zn(quinoline)2Cl2 in yields varying from 14 to 44%. The reaction procedure proved to be efficient for the synthesis of both alkyloxy- and aryloxy- substituted zinc tetrapyrazinoporphyrazines and did not require strictly anhydrous conditions. Optimal cyclotetramerization conditions were identified for each derivative, in terms of reaction temperature, as overheating cleaved the ether bond leaving a vacant OH group on the macrocycle. The photochemical and photophysical properties of the synthesized compounds were investigated in pyridine. Singlet oxygen quantum yields (ΦΔ) ranged from 0.49 to 0.61 and high fluorescence quantum yields (ΦF) of ∼0.30 were observed for non-aggregated compounds.
    Dyes and Pigments. 01/2010;
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    ABSTRACT: Introduction of an azide group onto the periphery of a photodynamically effective phthalocyanine (Pc) derivative gives a useful building block for the preparation of Pc conjugates via Cu(I)-catalyzed azide-alkyne 1,3-dipolar cycloaddition (‘click chemistry’). In this way, Pc–mestranol and Pc–hept-1-yne conjugates (for comparison purposes) are synthesized and their absorption, photochemical, and photophysical properties are studied. The conjugate retains the advantageous photophysical and photochemical properties of Pc. Conjugation with mestranol may lead to improved localization in tumors whereas the Pc unit is responsible for the photodynamic effect.
    Tetrahedron Letters - TETRAHEDRON LETT. 01/2010; 51(7):1016-1018.

Publication Stats

118 Citations
91.16 Total Impact Points

Institutions

  • 2003–2014
    • Charles University in Prague
      • • Faculty of Pharmacy in Hradec Králové
      • • Katedra chemické fyziky a optiky
      • • Katedra farmaceutické chemie a kontroly léčiv (FF Hradec Králové)
      Praha, Praha, Czech Republic
  • 2013
    • Kuwait University
      • Department of Chemistry
      Kuwait, Muhafazat al `Asimah, Kuwait
  • 2006
    • Pierre and Marie Curie University - Paris 6
      Lutetia Parisorum, Île-de-France, France
  • 2004
    • University of Hradec Králové
      Königgrätz, Královéhradecký, Czech Republic