Search

The properties and antimicrobial efficacies of zinc complexes of tetrakis(N-methylpyridinium-4-yl) tetraiodide porphyrin and tetrakis(N-methylpyridinium-4-yl) tetraiodide phthalocyanine impregnated to paper were evaluated. Photo-inactivation of microbes using inexpensive consumer light-emitting diode lamp was assessed on surface of dyed papers. Antimicrobial experiments of phthalocyanine-dyed paper by live cell assessment through colony forming units counting demonstrated 3.72 and 4.01 log reduction against Escherichia coli (E. coli) and Acinetobacter baylyi (A. baylyi) respectively after 1 h of illumination with 35 mW/cm2 light. The porphyrin-dyed paper exhibited 1.66 and 2.01 log reduction in colony forming units against E. coli and A. baylyi respectively after 1 h exposure with 4 mW/cm2 light. Both dyed papers were photo-stable after 64 h of continuous exposure with 42 mW/cm2 light, while phthalocyanine-dyed paper exhibited superior leaching stability in phosphate-buffered saline.

We have synthesized novel phthalocyanine with four pyridyl substituents connected to α-phthalo-positions via direct C-C bond. The Zn complex and tetracationic derivatives of phthalocyanine were also synthesized and the dyes were impregnated into filter paper to prepare photoactive antimicrobial surface. The photodynamic antimicrobial efficacy of the dyed paper samples was evaluated by a simple and fast setup using bioluminescent microbes. Escherichia coli and Acinetobacter baylyi ADP1 strains carrying bacterial luciferase genes were used in the screening experiment. The most efficient compound, tetracationic zinc derivative 8, was investigated further. The compound was highly water soluble, had high molar absorptivity and exhibited good adhesion to the filter paper without leaching into the solution. The singlet oxygen quantum yield of tetracationic zinc derivative 8 in water was found out to be 30 ± 20%. According to the cell viability assay test performed on E. coli wild type in solution, the molecule had similar or better photo toxicity as the reference photosensitizer, tetrakis (1-methyl-pyridinium-4-yl)porphyrin (TMPyP). Antimicrobial efficacy of the dye 8 on photoactive surface was studied by live cell assessment through colony forming unit (CFU) counting. The colored surface demonstrated 3 log reduction in CFU against E. coli and A. baylyi ADP1 just after 1 h of illumination with the white light of low intensity.

Formation of self-assembled monolayers (SAMs) of three porphyrin and one phthalocyanine derivatives on thin ZnO film was studied by monitoring absorption spectra of the samples. The compounds were equipped with carboxylic or phosphate groups to bind to the surface. The SAM formation was found to be fast. The layer was formed in less than 15 min for all studied porphyrins, and 30 min was sufficient to form phthalocyanine layer. For porphyrins with different anchor groups the SAM formation was too fast to see any difference between the anchoring groups. The stability of SAMs was tested then by immersing the samples into neat solvents. Upon immersion the SAMs were gradually losing the absorbance for all the compounds with degradation trends being in line with p[Formula: see text] values of the binding groups of the same type. However, even for the weakest binding group the SAM was relatively stable after a few tens of minutes of washing, which was sufficient to remove physisorbed compounds but the SAM was essentially not destroyed. Comparison of SAMs on thin films with SAMs on ZnO nanorods and TiO2 nanoparticle films indicated the same fast layer formation but relatively weaker SAMs stability, showing 20–40% faster absorption losses during the washing.

Synthesis, characterization, molecular modeling, and photovoltage responses of four phthalocyanine–fullerene (Pc-C60) dyads with two polar (−OH) side chains are described. The synthesized dyads have polar tails either on the Pc (electron donor D) side or on the fullerene (electron acceptor A) side of the dyad, providing a possibility to produce oriented donor–acceptor (D–A) monolayers with revised electron transfer direction when deposited on an aqueous subphase or on a solid surface. In the dyads, phthalocyanine and fullerene have different mutual orientations: in the trans-dyads they have face-to-face orientation, while in the cis-dyads the orientation is face-to-edge. Molecular modeling was used to examine and confirm the spatial arrangements of the synthesized dyads. The Pc-C60 dyads were deposited successfully onto solid substrates as highly oriented monolayers using the Langmuir–Schafer method. Formation of a vertically oriented monolayer and the following electron transfer from the photoexcited pht...

Evidence of the Marcus inverted region behavior for the forward electron transfer reaction in a double-linked zinc phthalocyanine–fullerene dyad was found. The charge separation and recombination processes of the dyad were studied in an ionic environment. The chloride ion coordination to the central zinc of the phthalocyanine macrocycle decreases the energy of the charge separated state and increases the energy of the phthalocyanine first singlet excited state, and thus increases the driving force for the charge separation and decreases it for the recombination. The charge separation is slowed down whereas the charge recombination is accelerated upon the chloride coordination.

A series of CdSe quantum dot (QD)–phthalocyanine (Pc) hybrids were synthesized and their photophysics was studied using steady state and time-resolved spectroscopic methods. Emission of QDs was progressively quenched upon increasing the concentration of Pc in the hybrids. A detailed transient absorption study of the hybrids revealed that the mechanism of quenching is charge separation, resulting in the formation of hybrids with negatively charged QDs and the Pc cation. Direct photo-excitation of Pc did not show any detectable interaction between the excited state of Pc and the QD to which it is attached. An explanation is proposed, based on the suggestion that the energy of the lowest unoccupied molecular orbital (LUMO) of Pc is lower than the lower edge of the QD conduction band, while the energy of the highest occupied molecular orbital (HOMO) of Pc is sufficiently higher than the high energy edge of the QD valence band (VB), thus permitting hole transfer from the QD VB to the Pc HOMO after photo-excitation of QDs. acceptedVersion

We have synthesized a set of porphyrin and phthalocyanine compounds with two different silane anchors. Syntheses of the anchor-substituted chromophores have been carried out via hydrosilylation of alkene derivatives, catalyzed by platinum complexes. The reduction side-process was suppressed using specific anchor/catalyst pairs, and the silane-containing compounds were successfully isolated from hydrogenated by-products in pure form with good yields. The target porphyrinoids having stable reactive silane anchors possess the ability to self-assemble on metal oxides and quartz surfaces and optical fibers. Covalent attachment is done in one-step, which makes the bonding process fast and easy. Immobilized chromophores were further converted by on-surface reactions into Zn(II) and Mg(II) metal complexes. The metallation time was found to be as fast as 1 min for Zn ion. Bonding densities calculated from the absorbances of the deposited layers give rough estimations for packing of the molecules on various substrates and evidence for monomolecular layers formation.

Phthalocyanine-fullerene dyads have being under intensive development and investigation during past decade. Strong absorption of the phthalocyanine chromophore in the red part of the spectrum and ability of the dyad to perform efficient photoinduced charge transfer in non-polar media make them particularly attractive for organic optoelectronic applications. This microreview will focus on covalently linked phthalocyanine-fullerene conjugates in solutions and solid nanostructures. The covalent bonding enables sufficient degree of control over mutual organization of the donor and acceptor parts, and makes possible to investigate the relationships between molecular structure and functioning of single molecules and molecular assemblies.

Liquid phthalocyanine and fullerene derivative monomers were synthesized, which can be cationically polymerized either thermally or by light and are suitable for preparing complex solar cell structures, obtainable only by organic vacuum deposition till now. A sandwich solar cell with a bulk heterojunction layer between single layers was shown to produce higher currents and voltages than either pure bilayer or pure bulk heterojunction. The proposed in situ polymerization method can be applied to a variety of active layers for preparation of solution-processed solar cells.

Photoinduced electron transfer reactions of phthalalocyanine-fullerene dyads, in which donor and acceptor moieties are covalently linked to each other, with one or two malonic linkers, were studied. In the dyads with two linkers, phthalocyanine and fullerene have mutual orientations, face-to-face or face-to-tail, which differ from each other and influence photoinduced electron transfer processes. Quantitative spectroscopic and time-resolved spectroscopic measurements were done in polar and non-polar solvents at room temperature and at several reduced temperatures. The emission spectra of the double-linked dyads were different from that of the reference phthalocyanine showing a shoulder at the red part of the spectrum, emission decays were two-exponential and emission lifetimes depend on monitoring wavelengths. These facts support, for the dyads with two linkers, the formation of an emissive intramolecular exciplex preceding the charge separated state. For these dyads the formation times of the charge separated state, approximately 0.4 ps and 0.8 ps for the face-to-face and face-to-tail isomers, respectively, were independent of temperature and the reaction is considered to be quantum tunneling in nature. The charge recombination times were temperature dependent, but decreased with the decrease of temperature from roughly 1.2 ns at room temperature to 0.7 ns at 190 K.

We have developed three basic phthalocyanine structures, containing one, two, or four hydroxy groups, which are simple to synthesize and purify, as well as can be characterized well by NMR and MS. These building blocks can easily be further modified to have anchor groups, which make the molecules suitable for attachment to solid substrates. We have used thioacetate and pentafluorophenyl ester moieties, giving target phthalocyanines the ability to self-assemble on gold, metal oxides, and glass. Bonding densities calculated from the absorbances of the layers suggest mean molecular area to be in the range of 1–3 nm2, which can be partially controlled by side substituents and the number of linkers.

Interlayer energy transfer from perylene diimide (PDI12) layers to phthalocyanine layers was studied using steady-state absorption, fluorescence, and time-resolved fluorescence and microscopy methods. The layers were prepared by Langmuir–Schafer method, spaced by a few layers of octadecylamine deposited by Langmuir–Blodgett method, when required. The fluorescence lifetime microscopy method allowed to exclude defects from the energy transfer analysis and calculate the fluorescence lifetimes of PDI12 for the defect free areas. The estimated distance dependence of the interlayer energy transfer follows roughly second order dependences on the distance with the critical distance of 6.9 nm.

A novel method for the synthesis of dimeric and monomeric phthalocyanine silicon complexes using a one-pot method, from tetra-substituted free-base phthalocyanines in the presence of HSiCl3 at room temperature, is described. Silation was carried out using different bases and the reaction time and the order of addition of the chemicals were varied. It was found that by changing the reaction conditions, it was possible to synthesize either monomers or dimeric complexes with direct Si–Si bonds, selectively.

This paper combines the most important results on studies performed by the authors during the last decade on photoinduced electron transfer reactions of pheophytin-, phthalocyanine-, and porphyrin-fullerene dyads, in which donor and acceptor moieties are covalently linked to each other. Practically all studied molecules form an intramolecular exciplex as a transient state before the formation of the charge separation state or tight ion pair. When the center-to-center distance of the donor and acceptor pair is short (7–10 Å) both the exciplex formation and primary electron transfer are extremely fast with rate constants of 7–23 × 1012 s -1 and 40–1400 × 109 s -1, respectively. Rates become slower when the distance and orientational fluctuation increases. No systematic correlation between free energies and the rates of the formation and recombination of the exciplex and the charge separation state, respectively, were observed. The mechanism is discussed in frames of the Marcus electron transfer and the radiationless quantum transition theories.

A double-bridged phthalocyanine–fullerene dyad (H 2 Pc–C 60 ee) was used as photo-active intramolecular donor–acceptor system in a layered organic solar cell. In this device, a poly(3-hexylthiophene) (PHT) film was used as electron donor, whereas either C 60 or perylene tetracarboxylic diimide (PTCDI) film was selected as electron acceptor. The introduction of the dyad layer leads to an enhancement of the power conversion efficiency ( η ) in all the examples, mainly due to an increase of the open-circuit voltage. By introducing the dyad in PTCDI-containing cells, the efficiency (being 0.32%) was enhanced by almost three times compared to that of the reference (0.12%). In C 60 -containing cells, the efficiency of the dyad sample (being 0.30%) was over one and half times higher than that of the reference in the absence of the dyad (0.18%). The role of such a dyad in the solar cells is discussed in detail.

Efficient photoinduced interlayer electron transfer from a phthalocyanine derivative, ZnPH4 , to porphyrin cation of a porphyrin–fullerene donor–acceptor dyad was demonstrated by using time-resolved photovoltage technique. Multicomponent thin films with desired layer arrangements were constructed by the Langmuir–Blodgett and spin-coating methods in order to study charge transfer in solid state. As a contradiction to the photovoltage experiments, the dyad monolayer in the film structure did not enhance the current amplitude in electrochemical photocurrent measurements. This is associated with a weak electronic interaction between fullerene and aqueous electrolyte, reducing the photocurrent generation. The use of poly(3-hexylthiophene) as a hole conducting layer was shown to improve photocurrent yield of the device by forming efficient heterojunction together with the ZnPH4 layer.

Photoinduced interlayer energy and electron transfer from a thiophene derivative, PVT3, to a porphyrin−fullerene dyad, P-F, was demonstrated. The laser flash photolysis method was utilized to characterize photoinduced processes in layered thin films constructed by the Langmuir−Blodgett and spin-coating techniques. Poly(3-hexylthiophene), PHT, was used as an electron-donating layer to the dyad and PVT3. Electron transfer through a multilayer film with a PHT−PVT3−P-F layer sequence was shown, yielding the final charge-separated state where the positive charges are located in the PHT network and the electrons in the fullerene sublayer. The crucial role of excited P-F for the overall charge transfer efficiency of a bilayer film containing a phthalocyanine derivative, ZnPH4, as an electron-donating moiety to P-F was demonstrated. The lifetime of the electrical signal of the charge separation was shown to be prolonged compared to that of the optical signal.

We have synthesized a series of tetrakis(arylvinylene)phthalocyanines from the corresponding phthalonitriles. Substitution of the para-fluorine in the pentafluorphenyl ring with an alkoxy group from the solvent occurs during the synthesis. This substitution can be suppressed by the addition of zinc chloride or tin chloride to the reaction mixture. According to 1 H and 19 F NMR data, the cis- or trans-conformations of the starting materials are retained during condensation; thus the phthalocyanines formed are in all-cis or all-trans form. Cis-trans photoisomerization occurs easily for phthalonitriles, while phthalocyanines retain their conformations under UV beam.

Photoinduced electron transfer (ET) in films of the double-linked free-base phthalocyanine - fullerene dyads (Pc - C60) was studied in solid Langmuir - Blodgett (LB) films using femtosecond pump - probe and microsecond flash-photolysis methods. Excitation of the phthalocyanine (Pc) moiety of the dyad results in a rapid (0.8 ps) intramolecular ET from phthalocyanine to fullerene. The formed charge separated (CS) state relaxes in 35 ps, yielding an intermolecular CS state, which relaxes to the ground state in the microsecond time domain. The surface organization of the Pc - C60 dyad monolayers was studied by atomic force microscopy for·both pure Pc - C60 films and PC - C60 mixed films with matrix molecules, octadecylamine (ODA). This study together with the estimations done based on surface pressure-mean molecular area isotherms reveals that the dyads tend to aggregate rather than form a homogeneous mixture with the ODA molecules. This enforces intermolecular interactions and leads to the formation of a long-lived intermolecular CS state.

Vectorial photoinduced electron transfer was studied in Langmuir-Blodgett films. The monolayers of polythiophene and phthalocyanine were used as secondary electron donors in multilayers together with the monolayer of porphyrin-fullerene donor-acceptor dyad molecules mixed with octadecylamine (1:9). Simultaneous utilization of all the three compounds in the preparation of three-layer samples allowed us to widen the range of the visible light absorption by the structure. The relative sensitivity of the sample to the excitation laser light increased by about 350 times compared with that of a dyad monolayer.

Three new double-bridged phthalocyanine–fullerene dyads were studied with spectroscopic and electrochemical methods. The two-linker strategy was applied for the first time to phthalocyanine–fullerene dyads. Photoinduced electron transfer (ET) of the dyads was found to occur from the excited state of phthalocyanine both in polar and non-polar environment. Examination of ET energetics revealed that the phthalocyanine–fullerene dyads exist mainly in an extended conformation as opposed to a face-to-face orientation common for the similar double-bridged porphyrin–fullerene dyads.

In this study double linked porphyrin-fullerene and phthalocyanine-fullerene dyads and a single linked phthalocyanine-fullerene dyad were studied as components in inverted organic solar cells (OSCs) equipped with the well known P3HT:PCBM bulk heterojunction as the photoactive layer. The dyad monolayers were deposited onto a surface of P3HT:PCBM by using the Langmuir-Schafer method, therefore forming oriented monolayers in which the electron donor (D) and the acceptor (A) exist as a close proximity pair in a 1:1 molar ratio. As a result of this structure short circuit current density (J(sc)), open circuit voltage (V(oc)), and power conversion efficiency (η) increased, while the fill factor (FF) remained the same. The devices which contained dyads with double linkage produced higher efficiencies than the one with a single linked dyad. This result can be explained in terms of molecular orientation. It was also verified that the prepared OSC devices have promising long term air stability.

The synthesis of a new azafullerene C(59)N-phthalocyanine (Pc) dyad is described. The key step for the synthesis of the C(59)N-Pc dyad was the formation of the C(59)N-based carboxylic acid, which was smoothly condensed with hydroxy-modified Pc. The structure of the C(59)N-Pc dyad was verified by (1)H and (13)C NMR spectroscopy, IR spectroscopy, UV/Vis spectroscopy and MS measurements. The photophysical and electrochemical properties of the C(59)N-Pc dyad were investigated in both polar and non-polar solvents by steady state and time-resolved photoluminescence and absorption spectroscopy, as well as by cyclic voltammetry. Different relaxation pathways for the photoexcited C(59)N-Pc dyad, as a result of changing the solvent polarity, were found, thus giving rise to energy-transfer phenomena in non-polar toluene and charge-transfer processes in polar benzonitrile. Finally, the detailed quenching mechanisms were evaluated and compared with that of a C(60)-Pc dyad, which revealed that the different excited-state energies and reduction potentials of the two fullerene spheres (i.e. C(59)N vs. C(60)) strongly diverged in the deactivation pathways of the excited states of the corresponding phthalocyanine dyads.

Photoinduced processes in phthalocyanine-functionalized gold nanoparticles (Pc-AuNPs) have been investigated by spectroscopic measurements. The metal-free phthalocyanines used have two linkers with thioacetate groups for bonding to the gold nanoparticle surface, and the attachment was achieved using a ligand exchange reaction. The absorption spectrum of the Pc-AuNPs shows a broadening of the phthalocyanine Q-band absorption, probably due to a tight packing of the phthalocyanines on the gold nanoparticle surface. For the attached phthalocyanines, fluorescence is strongly quenched, and the fluorescence lifetimes determined by time-correlated single photon counting (TCSPC) are strongly reduced. The quenching mechanisms were studied in detail with time-resolved absorption (pump-probe) measurements. A selective excitation of the gold cores in the pump-probe experiment results in an energy transfer from the gold nanoparticles to the attached phthalocyanines in ∼2.4 ps. Photoexcitation of mainly the phthalocyanines in the functionalized nanoparticles leads to an electron transfer to the gold core in ∼3.0 ps. The recombination of charges in the Pc-AuNP takes place on a picosecond time scale. In addition, there is evidence of energy transfer from the photoexcited phthalocyanines to the gold nanoparticles.

Alternate bilayer structures of N,N'-bis(2,5-di-tert-butylphenyl)-3,4,9,10- perylene dicarboximide (PDI), freebase phthalocyanines (Pc), and double-linked free-base phthalocyanine-fullerene dyad (Pc-C 60) were prepared by the Langmuir-Schäfer method and studied using a range of optical spectroscopy methods including femtosecond pump-probe and up-conversion. An efficient quenching of the PDI fluorescence by Pc and Pc-C 60 dyad was observed in both steady-state and time-resolved fluorescence measurements. The quenching takes place in less than a few picoseconds, and is due to energy transfer from perylene dicarboximide to phthalocyanine chromophore in PDI|Pc and PDI|Pc-C 60 films. In the PDI|Pc-C 60 bilayer structure the energy transfer is followed by a charge separation in the Pc-C 60 layer, yielding a long-lived (a few microseconds) intermolecular charge separated state similar to that reported recently for Pc-C 60 Langmuir-Blodgett films (Lehtivuori, H.; et al. J. Phys. Chem. C 2008, 112, 9896-9902).

Evidences of an intramolecular exciplex intermediate in a photoinduced electron transfer (ET) reaction of double-linked free-base and zinc phthalocyanine-C-60 dyads were found. This was the first time for a dyad with phthalocyanine donor. Excitation of the phthalocyanine moiety of the dyads results in rapid ET from phthalocyanine to fullerene via an exciplex state in both polar and nonpolar solvents. Relaxation of the charge-separated (CS) state Pc center dot+-C-60(center dot-) in a polar solvent occurs directly to the ground state in 30-70 ps. In a nonpolar solvent, roughly 20% of the molecules undergo transition from the CS state to phthalocyanine triplet state Pc-3*-C-60 before relaxation to the ground state. Formation of the CS state was confirmed with electron spin resonance measurements at low temperature in both polar and nonpolar solvent. Reaction schemes for the photoinduced ET reactions of the dyads were completed with rate constants obtained from the time-resolved absorption and emission measurements and with state energies obtained from the fluorescence, phosphorescence, and voltammetric measurements.