Supramolecular pattern of fullerene on 2D bimolecular "chessboard" consisting of bottom-up assembly of porphyrin and phthalocyanine molecules

Two-component adlayers consisting of zinc(II) phthalocyanine (ZnPc) and a metalloporphyrin, such as zinc(II) octaethylporphyrin (ZnOEP) or zinc(II) tetraphenylporphyrin (ZnTPP), were prepared by immersing either an Au(111) or Au(100) substrate in a benzene solution containing those molecules. The bimolecular adlayers thus prepared were investigated in 0.1 M HClO4 by cyclic voltammetry (CV) and electrochemical scanning tunneling microscopy (EC-STM). A supramolecularly organized "chessboard" structure was formed for the ZnPc and ZnOEP bimolecular array on Au(111), while characteristic nanohexagons were found in the ZnTPP and ZnOEP bimolecular adlayer. EC-STM revealed that the surface mobility and the molecular re-organization of ZnPc and ZnOEP on Au(111) were tunable by manipulating the electrode potential, whereas the ZnTPP and ZnOEP bimolecular array was independent of the electrode potential. A "bottom-up" hybrid assembly of fullerene molecules was formed successfully on an alternate array of bimolecular ZnPc and ZnOEP molecules. The bimolecular "chessboard" served as a template to form the supramolecular assembly of C60 by selective trapping in the open spaces. A supramolecular organization of ZnPc and ZnOEP was also found on the reconstructed Au(100)-(hex) surface. A highly ordered, compositionally disordered but alternate array of ZnPc and ZnOEP was formed on the reconstructed Au(100)-(hex) surface, indicating that the bimolecular adlayer structure is dependent on the atomic arrangement of underlying Au in the formation of supramolecular nanostructures composed of those molecules. On the bimolecular array consisting of ZnPc and ZnOEP on the Au(100)-(hex), no highly ordered supramolecular assembly of C60 was found, suggesting that the supramolecular assembly of C60 molecules is strongly dependent upon the bimolecular packing arrangement of ZnPc and ZnOEP.     

Graphene quantum dot-phthalocyanine polystyrene conjugate embedded in asymmetric polymer membranes for photocatalytic oxidation of 4-chlorophenol

The feasibility of using π–π stacking as a means of fixing unsubstituted Zn phthalocyanine (ZnPc) to a support prior to formation of photoactive polymer asymmetric membranes was explored. Stable ZnPc–graphene quantum dot-polystyrene conjugates (6.15 μmol/g ZnPc loading) were synthesized and embedded in polystyrene membranes which proved to be photoactive with a singlet oxygen quantum yield of 0.43 in ethanol and 0.37 in water. The membranes also proved to be active in the photocatalytic oxidation of 4-chlorophenol in water where the reaction followed second-order kinetics. At 3.24 × 10^?4 mol L^?1, the photo-oxidation of 4-chlorophenol was observed with a k_obs of 35.9 L mol^?1 min^?1 and a half-life of 86 min.     

Release of nitric oxide from a sol-gel hybrid material containing a photoactive manganese nitrosyl upon illumination with visible light

A polyurethane-coated sol-gel material containing the photoactive Mn nitrosyl [Mn(PaPy3)(NO)]ClO4 rapidly releases NO with high quantum efficiency when exposed to visible light of low intensity. This rigid and strongly colored hybrid material is a convenient point source of NO that can only be triggered with light. Successful delivery of NO to biological targets, such as proteins, by this material has also been demonstrated.     

Stabilization of charge-separated states in phthalocyanine-fullerene ensembles through supramolecular donor-acceptor interactions

A novel ZnPc-C60 dyad (3), in which two photoactive units are brought together by a phenylenevinylene spacer has been synthesized. The synthetic strategy en route toward 3 involves a Heck reaction to attach 4-vinylbenzaldehyde to a monoiodophthalocyanine precursor, followed by standard cycloaddition of azomethine ylides (generated from the formylPc derivative and N-methylglycine) to one of the double bonds of C60. Electrochemical studies reveal that in 3 the ZnPc is about 39 mV more difficult to oxidize than in the corresponding ZnPc reference, which points to appreciable electronic communication between ZnPc and C60 in the ground state. In the excited state, photoexcitation leads to the formation of a charge-separated ZnPc*+-C60*- state, for which a lifetime of 130 ns was determined in THF. Hetero-association between complementary Pcs (1 and 2 or 3 and 2), which carry different peripheral functionalities (i.e., either electron-donating alkoxy groups or electron-deficient alkylsulfonyl chains) was assessed by different techniques. They provided evidence for donor-acceptor 1:1 complex formation with a stability constant of ca. 10(5) M(-1) in CHCl3. Interestingly, hetero-association of ZnPc-C60 dyad 3 with an electron-deficient PdPc (2) allowed the construction of supramolecular triads, in which a substantial stabilization of the radical pair is seen relative to that of the covalently linked dyad ZnPc-C60 (3).     

Molecular photovoltaic system based on fullerenes and carotenoids co-assembled in lipid/alkanethiol hybrid bilayers

A hybrid molecular photovoltaic system, based on fullerene C(60) and lutein (a natural photosynthetic carotenoid pigment) that are assembled in a phospholipid/alkanethiol bilayer matrix, is described here. The assembly and photoconversion behaviors of such a system were studied by UV-vis spectroscopy, cyclic voltammetry, impedance spectroscopy, photoelectrochemical action spectroscopy, and photocurrent generation. While lutein itself is inefficient in generating photocurrent, it can strongly modulate photocurrents produced by fullerenes when coassembled in the lipid bilayer matrix presumably via photoinduced electron transfer. Our results thus provide a successful example of combining both synthetic and natural photoactive components in building molecular photovoltaic systems.     

Excited‐State Charge Transfer in Covalently Functionalized MoS2 with a Zinc Phthalocyanine Donor–Acceptor Hybrid

The functionalization of MoS₂ is of paramount importance for tailoring its properties towards optoelectronic applications and unlocking its full potential. Zinc phthalocyanine (ZnPc) carrying an 1,2‐dithiolane oxide linker was used to functionalize MoS₂ at defect sites located at the edges. The structure of ZnPc‐MoS₂ was fully assessed by complementary spectroscopic, thermal, and microscopy imaging techniques. An energy‐level diagram visualizing different photochemical events in ZnPc‐MoS₂ was established and revealed a bidirectional electron transfer leading to a charge separated state ZnPc^{. +} ‐MoS₂^.?. Markedly, evidence of the charge transfer in the hybrid material was demonstrated using fluorescence spectroelectrochemistry. Systematic studies performed by femtosecond transient absorption revealed the involvement of excitons generated in MoS₂ in promoting the charge transfer, while the transfer was also possible when ZnPc was excited, signifying their potential in light‐energy‐harvesting devices.     

ON THE SOURCE OF THE OSCILLATIONS OBSERVED DURING in vivo ZINC PHTHALOCYANINE FLUORESCENCE PHARMACOKINETIC MEASUREMENTS IN MICE

Surface-detected fluorescence spectroscopy can be used to monitor the pharmacokinetics of uptake and clearance of red-absorbing fluorophores such as zinc(II) phthalocyanine (ZnPc) in vivo. When this technique is applied to mice that have been fed on a normal chlorophyll-based diet, and particularly when measurements are performed in the abdominal region, oscillations are sometimes observed superimposed on the pharmacokinetic curve of the ZnPc. An oscillatory signal has also been observed arising from the abdominal region of control mice fed a normal diet but not injected with the ZnPc photosensitizer; this oscillatory component to the signal is reduced when mice are fed a chlorophyll-free diet. The oscillatory signal component has been attributed to fluorescence arising from chlorophyll derivatives (pheophorbide/pheophytin) contained in the rodent food, whose concentration in the measured abdominal region changes substantially with time, presumably due to digestive processes. Thus it is important to be aware of the possibility of such artifactual contributions to in vivo fluorescence pharmacokinetic measurements.     

Analysis and regulation of unusual adsorption of phthalocyanine zinc(II) into a Nafion film as investigated by UV-vis spectroscopic techniques

Phthalocyanine zinc(II) (ZnPc) was found to be adsorbed well into a Nafion (Nf) film. The kinetic analysis suggested that the adsorption of ZnPc into the Nf film is controlled by its diffusion in the Nf film with a diffusion coefficient of D = 1.9 x 10(-6) cm(2) s(-1) that is higher than those (10(-9)-10(-12) cm(2) s(-1)) of cationic redox molecules in the Nf film by 3-6 orders of magnitude. The adsorption isothermal was analyzed by a Brunauer-Emmett-Teller (BET) equation suggesting multilayer adsorption of ZnPc into the film. The BET analysis provided the amount of ZnPc for monolayer adsorption (w(m) = 1.50 x 10(-7) mol cm(-2)), from which the effective area for the ZnPc adsorption was estimated to be larger by a factor of 1.7 x 10(3) than the Nf film area (1.0 cm(2)). The absorption spectra of a Nf film adsorbing ZnPc ((Nf/ZnPc)(ads) film) exhibited two broad absorption bands at 385 and 680-750 nm without any structural features, which is significantly different from the absorption spectra of either ZnPc solution in DMF or a (Nf/ZnPc)(mix) film prepared from a DMF solution containing Nf and ZnPc by solvent evaporation. This is ascribed to the formation of a ZnPc aggregate in the (Nf/ZnPc)(ads) film. Photoluminescence data for the (Nf/ZnPc)(mix) film suggested the presence of a ZnPc monomer and dimer at equilibrium in the film with a concentration of 0.1 M and that energy transfer occurs from the monomer to the dimer in excitation of the monomer (at lambda(ex) = 609 nm) to yield emission from the dimer. By contrast, photoluminescence data for the (Nf/ZnPc)(ads) film suggested that the excited ZnPc is self-quenched significantly by the formation of the ZnPc aggregate in the film. The lesser electroactivity of ZnPc in the (Nf/ZnPc)(ads) film compared with that in the (Nf/ZnPc)(mix) film could be ascribable to more difficult diffusion of ZnPc in the former film due to the formation of the ZnPc aggregate. The adsorption of ZnPc into the Nf film was significantly regulated by simple pretreatments of the Nf film such as immersion in solvents and storage under solvent vapors. The regulation was explained by controlled physical and chemical properties of a channel for mass and ion transport that is formed by sulfonate groups, countercations, and solvent molecules in the Nf film.     

Formation of heterocaryotic and homonuclear bridged–dimeric complexes on surface

The formation of coordinated dimeric complexes bridged by axial ligands on surface is observed with the help of a 1,3,5-tris(10-carboxydecyloxy)benzene(TCDB) template through scanning tunneling microscopy(STM). STM images of molecular adlayers of zinc tetraphenylporphyrin(Zn TPP), zinc phthalocyanine(Zn Pc), and their mixture are reported. Zn TPP and Zn Pc can spontaneously form highly an ordered structure with a 1:1 molar ratio, which is different from that of individual Zn Pc. The coordinated bimolecular complexes bridged with axial ligands, simply as Zn Pc–DPP–Zn TPP and Zn Pc–DPE–Zn Pc, are presented and the corresponding surface structures are compared. Zn Pc and Zn TPP can be connected by an axial ligand DPP and formed assembled structures out of surface. Two types of arrays with entirely new structure are obtained for the Zn Pc–DPE–Zn Pc complex. These bridged hybrid complexes provide an example of design of self-organized crystals on the basis of coordination through non-covalent interactions.     

Molecular layers of ZnPc and FePc on Au(111) surface: Charge transfer and chemical interaction

We have studied zinc phthalocyanine (ZnPc) and iron phthalocyanine (FePc) thick films and monolayers on Au(111) using photoelectron spectroscopy and x-ray absorption spectroscopy. Both molecules are adsorbed flat on the surface at monolayer. ZnPc keeps this orientation in all investigated coverages, whereas FePc molecules stand up in the thick film. The stronger inter-molecular interaction of FePc molecules leads to change of orientation, as well as higher conductivity in FePc layer in comparison with ZnPc, which is reflected in thickness-dependent differences in core-level shifts. Work function changes indicate that both molecules donate charge to Au; through the π-system. However, the Fe3d derived lowest unoccupied molecular orbital receives charge from the substrate when forming an interface state at the Fermi level. Thus, the central atom plays an important role in mediating the charge, but the charge transfer as a whole is a balance between the two different charge transfer channels; π-system and the central atom.     

Steady state and time-resolved spectroscopic studies on zinc(II) phthalocyanine in liposomes.

Zinc(II) phthalocyanine (ZnPc), a potential second-generation phototherapeutic agent for tumours, has been incorporated into small unilamellar vesicles (SUVs) (diameter, 52 nm) and large unilamellar vesicles (LUVs) (diameter, 84 nm) of dipalmitoyl-phosphatidylcholine (DPPC). Absorption spectroscopy, as well as steady state and time-resolved fluorescence emission studies, indicate that ZnPc is monomeric in SUVs at a stoichiometric concentration below 0.25 microM (corresponding to an actual endoliposomal concentration of about 0.5 mM), while in LUVs it is monomeric below 2 microM. The fluorescence lifetime of the monomer is 3-3.5 ns. Upon increasing the ZnPc concentration, aggregated derivatives are formed, which are characterized by shorter fluorescence lifetimes (1.2-1.5 ns; 0.4-0.6 ns). The possible implications of these observations for the phototherapeutic efficiency of ZnPc are briefly discussed.     

Directly Linked Zinc Phthalocyanine–Perylenediimide Dyads and a Triad for Ultrafast Charge Separation

Directly linked to promote strong intramolecular interactions, donor–acceptor dyads and a donor–acceptor–donor triad featuring zinc phthalocyanine (ZnPc) as electron donor and perylenediimide (PDI) as electron acceptor have been synthesized and characterized. Owing to complementary absorption features of the entities, improved light absorption was witnessed in these conjugates. The optimized geometry and electronic structures showed the majority of the highest occupied molecular orbital (HOMO) on the ZnPc entity, whereas the lowest unoccupied molecular orbital (LUMO) was on the PDI entity, suggesting that the charge-separated states would be ZnPc ⁺ –PDI ^{. −}. The electrochemical and free-energy calculations suggested exothermic energy and/or electron transfer processes via the singlet states of PDI or ZnPc entities depending on the excitation wavelength of the laser used. The measured rates using femtosecond pump-probe spectroscopy coupled with global analysis of transient data revealed ultrafast energy transfer from ¹PDI* to ZnPc followed by charge separation. However, when ZnPc was selectively excited, only electron transfer was witnessed wherein the time constants for forward and reverse electron transfer processes followed Marcus predictions. The absorption in a wide section of the solar spectrum and the ultrafast charge separation suggest the usefulness of these systems as good photosynthetic models.     

Chemical Enhancement and Quenching in Single-Molecule Tip-Enhanced Raman Spectroscopy

Despite intensive research in surface enhanced Raman spectroscopy (SERS), the influence mechanism of chemical effects on Raman signals remains elusive. Here, we investigate such chemical effects through tip-enhanced Raman spectroscopy (TERS) of a single planar ZnPc molecule with varying but controlled contact environments. TERS signals are found dramatically enhanced upon making a tip–molecule point contact. A combined physico-chemical mechanism is proposed to explain such an enhancement via the generation of a ground-state charge-transfer induced vertical Raman polarizability that is further enhanced by the strong vertical plasmonic field in the nanocavity. In contrast, TERS signals from ZnPc chemisorbed flatly on substrates are found strongly quenched, which is rationalized by the Raman polarizability screening effect induced by interfacial dynamic charge transfer. Our results provide deep insights into the understanding of the chemical effects in TERS/SERS enhancement and quenching.     

Formation and Photoinduced Electron Transfer in Porphyrin- and Phthalocyanine-Bearing N-Doped Graphene Hybrids Synthesized by Click Chemistry

Graphene doped with heteroatoms such as nitrogen, boron, and phosphorous by replacing some of the skeletal carbon atoms is emerging as an important class of two-dimensional materials as it offers the much-needed bandgap for optoelectronic applications and provides better access for chemical functionalization at the heteroatom sites. Covalent grafting of photosensitizers onto such doped graphenes makes them extremely useful for light-induced applications. Herein, we report the covalent functionalization of N-doped graphene (NG) with two well-known electron donor photosensitizers, namely, zinc porphyrin (ZnP) and zinc phthalocyanine (ZnPc), using the simple click chemistry approach. Covalent attachment of ZnP and ZnPc at the N-sites of NG in NG−ZnP and NG−ZnPc hybrids was confirmed by using a range of spectroscopic, thermogravimetric and imaging techniques. Ground- and excited-state interactions in NG−ZnP and NG−ZnPc were monitored by using spectral and electrochemical techniques. Efficient quenching of photosensitizer fluorescence in these hybrids was observed, and the relatively easier oxidations of ZnP and ZnPc supported excited-state charge-separation events. Photoinduced charge separation in NG−ZnP and NG−ZnPc hybrids was confirmed by using the ultrafast pump-probe technique. The measured rate constants were of the order of 10¹⁰ s,⁻¹ thus indicating ultrafast electron transfer phenomena.     

Preparation and characterization of solution processable phthalocyanine‐containing polymers via a combination of RAFT polymerization and post‐polymerization modification techniques

In this work, a benzenedinitrile functionalized monomer, 2‐methyl‐acrylic acid 6‐(3,4‐dicyano‐phenoxy)‐hexyl ester, was successfully polymerized via the reversible addition‐fragmentation chain transfer method. The polymerization behavior conveyed the characteristics of “living”/controlled radical polymerization: the first‐order kinetics, linear increase of number‐average molecular weight with monomer conversion, narrow molecular weight distribution, and successful chain‐extension experiment. The soluble Zn(II) phthalocyanine (Pc)‐containing (ZnPc) polymers were achieved by post‐polymerization modification of the obtained polymers. The Zn(II) phthalocyanine‐functionalized polymer was characterized by FTIR, UV–vis, fluorescence, atomic absorption spectroscopy, and thermogravimetric analysis. The potential application of above ZnPc‐functionalized polymer as electron donor material in bulk heterojunction organic solar cell was studied. The device with ITO/PEDOT:PSS/ZnPc‐Polymer/PC₆₁BM/LiF/Al structure provided a power conversion efficiency of 0.014%, fill factor of 0.24, open circuit voltage (V_oc) of 0.21 V, and short‐circuit current (J_sc) of 0.28 mA/cm². © 2013 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 691–698     

聚乙二醇/羟基磷灰石纳米杂化材料的制备及表征

以聚乙二醇单甲醚(MPEG)为原料, 采用先磷酰化再水解的方法合成了聚乙二醇单甲醚磷酸酯(P-MPEG). 以P-MPEG为空间位阻剂, 采用共沉淀法合成了内核为纳米羟基磷灰石(nHA)、 壳层为MPEG链的纳米杂化材料. 用傅里叶变换红外光谱(FTIR)、 X射线衍射(XRD)、 透射电子显微镜(TEM)和激光粒度分析(LPSA)对材料结构进行了表征. 结果表明, 所合成的杂化材料不仅能在水中再分散, 而且可以在甲醇和二甲基甲酰胺(DMF)等有机溶剂中再分散.     

A Methylthio‐Functionalized‐MOF Photocatalyst with High Performance for Visible‐Light‐Driven H2 Evolution

Recently, the emergence of photoactive metal–organic frameworks (MOFs) has given great prospects for their applications as photocatalytic materials in visible‐light‐driven hydrogen evolution. Herein, a highly photoactive visible‐light‐driven material for H₂ evolution was prepared by introducing methylthio terephthalate into a MOF lattice via solvent‐assisted ligand‐exchange method. Accordingly, a first methylthio‐functionalized porous MOF decorated with Pt co‐catalyst for efficient photocatalytic H₂ evolution was achieved, which exhibited a high quantum yield (8.90 %) at 420 nm by use sacrificial triethanolamine. This hybrid material exhibited perfect H₂ production rate as high as 3814.0 μmol g^?1 h^?1, which even is one order of magnitude higher than that of the state‐of‐the‐art Pt/MOF photocatalyst derived from aminoterephthalate.     

A COMPARISON OF FLUORESCENCE METHODS USED IN THE PHARMACOKINETIC STUDIES OF Zn(II)PHTHALOCYANINE IN MICE

The pharmacokinetics of Zn phthalocyanine (ZnPc) encapsulated in dipalmitoyl-phosphatidylcholine (DPPC) liposomes, injected intravenously in Skh:HR-1 nude mice, was monitored by two in vitro techniques and one in vivo technique, all based on fluorescence spectroscopy. The in vitro methods involve either fluorescence measurements on thin tissue sections or on extracts from these tissues. The in vivo method involves the fluorescence measurement at the skin surface. Both in vitro techniques gave similar results which are consistent with previous findings on the pharmacokinetic behavior of ZnPc. The liver and spleen showed rapid ZnPc concentration increases, reaching a maximum level in 30 min. or less post drug administration. Relatively little ZnPc was detected in the skin, fat or muscle, the maximum concentration occurring at 12 h. In vivo fluorescence reached a maximum intensity approx. 6 h post injection at the mid-chest analysis site and at 12 h in the thigh. The in vivo measurements at two different anatomical sites showed pharmacokinetic behavior that reflects an overall integrated fluorescence originating from several tissue sites.     

Investigation on the orderly growth of thick zinc phthalocyanine films on Ag(100) surface

The growth of zinc phthalocyanine (ZnPc) on Ag(100) surface from monolayer to multilayer was investigated by low-energy electron diffraction, x-ray diffraction, and high-resolution electron energy loss spectroscopy (HREELS). At monolayer coverage, ZnPc molecules form an ordered film with molecular planes parallel to the substrate. The same structure is maintained as the film thickness increases. HREELS analysis shows that intermolecular π-π interaction dominates during the film growth from monolayer to multilayer. The π-d interaction between the adsorbates and the substrate is only applicable in the first adlayer. Stronger intermolecular-layer interaction is observed at higher coverages.     

Supramolecular Zinc Phthalocyanine–Imidazolyl Perylenediimide Dyad and Triad: Synthesis,Complexation, and Photophysical Studies

Two new supramolecular architectures based on zinc phthalocyanine (Pc) and imidazolyl‐substituted perylenediimide (PDI), ZnPc/DImPDI/ZnPc 1 and ZnPc/ImPDI 2 , have been prepared. A strong electron‐donor, 8 , which contained eight tert‐octylphenoxy groups was synthesized to ensure high solubility, thereby reducing aggregation in solution and providing σ‐donor features while avoiding regioisomeric mixtures. Also, PDI units were functionalized with tert‐octylphenoxy groups at the bay positions, which provide solubility to avoid aggregation in solution, together with one and two imidazole moieties in the amide position, 6 and 4 , respectively, to be able to strongly coordinate with the ZnPc complex. Supramolecular complexation studies by ¹H NMR spectroscopy and ESI‐MS demonstrate a high coordinative binding constant between imidazole‐substituted 4 or 6 and 8 . The same results were confirmed by UV/Vis and fluorescence titration studies. UV/Vis titration studies revealed the formation of a 1:1 complex ZnPc/ImPDI 2 for the systems 8 and 6 and a 2:1 complex ZnPc/DImPDI/ZnPc 1 for the interaction of 8 and 4 . The binding constant in both cases was determined to be on the order of 10⁵ M ⁻¹. Femtosecond laser flash photolysis measurements provided a direct proof of the charge‐separated state within both supramolecular assemblies by observing the transient absorption band at 820 nm due to the zinc phthalocyanine radical cation. The lifetimes of charge‐separated states are (9.8±3) ns for triad 1 and (3±1) ns for dyad 2 . As far as we know, this is the first time that a radical ion pair has been detected in a supramolecular assembled ZnPc–PDI system and has obtained the longest lifetime of a charge‐separated state published for ZnPc–PDI assemblies.