Observation of zinc phthalocyanine aggregates on a water surface using grazing incidence X-ray scattering

Reported here are the structural properties of a zinc 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine Langmuir monolayer on a water surface under progressive lateral compression investigated by grazing incidence X-ray scattering. Grazing incidence diffuse X-ray scattering out of the specular plane (GIXOS) is exploited to determine specular reflectivity-like information where the phase change of flat-lying molecules on the surface to edge-standing molecules perpendicular to the surface is directly observed. Furthermore, grazing incident X-ray diffraction (GIXD) is used to investigate the in-plane ordering of the system where it has been found that in the high-density state (approximately 0.35 nm2 per molecule) the system can be considered to be a monolayer consisting of arrays of side-by-side lying cofacially aggregated cylindrical rodlike entities.     

Matrix effects on copper(II)phthalocyanine complexes. A combined continuous wave and pulse EPR and DFT study

The effect of the electron withdrawing or donating character of groups located at the periphery of the phthalocyanine ligand, as well as the influence of polar and nonpolar solvents are of importance for the redox chemistry of metal phthalocyanines. Continuous wave and pulse electron paramagnetic resonance and pulse electron nuclear double resonance spectroscopy at X- and Q-band are applied to investigate the electronic structure of the complexes Cu(II)phthalocyanine (CuPc), copper(II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuPc(t)), and copper(II) 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexadecafluoro-29H,31H-phthalocyanine (CuPc(F)) in various matrices. Isotope substitutions are used to determine the g values, the copper hyperfine couplings and the hyperfine interactions with the 14N, 1H and 19F nuclei of the macrocycle and the surrounding matrix molecules. Simulations and interpretations of the spectra are shown and discussed, and a qualitative analysis of the data using previous theoretical models is given. Density functional computations facilitate the interpretation of the EPR parameters. The experimental g, copper and nitrogen hyperfine and nuclear quadrupole values are found to be sensitive to changes of the solvent and the structure of the macrocycle. To elucidate the electronic, structural and bonding properties the changes in the g principal values are related to data from UV/Vis spectroscopy and to density functional theory (DFT) computations. The analysis of the EPR data indicates that the in-plane metal-ligand sigma bonding is more covalent for CuPc(t) in toluene than in sulfuric acid. Furthermore, the out-of-plane pi bonding is found to be less covalent in the case of a polar sulfuric acid environment than with nonpolar toluene or H2Pc environment, whereby the covalency of this bonding is increased upon addition of tert-butyl groups. No contribution from in-plane pi bonding is found.     

Phthalocyanine and polystyrene film nanocomposites

The organic solvent was shown to determine the structure of copper(II) 2,9,16,23-tetra-tert-butyl-29H,31H-phthalocyanine (CuPc) in the CuPc-polystyrene composite during the formation of the latter. The structure and morphology of the resulting nanocomposite films was studied by atomic force and transmission electron microscopy. Different physical structures of CuPc formed in different solvents (cyclohexane, toluene, chloroform, and trichloroethylene).     

Two-dimensional "nano-ring and nano-crystal" morphologies in Langmuir monolayer of phthalocyaninato nickel complexes

Three 1,8,15,22-tetrasubstituted phthalocyaninato nickel complexes Ni[Pc(alpha-OR)(4)] [H(2)Pc(alpha-OC(5)H(11))(4) = 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine; H(2)Pc(alpha-OC(7)H(15))(4) = 1,8,15,22-tetrakis(2,4-dimethyl-3-pentyloxy)phthalocyanine; H(2)Pc(alpha-OC(10)H(7))(4) = 1,8,15,22-tetrakis(2-naphthyloxy)phthalocyanine] (1-3) have been prepared by treating the corresponding metal-free phthalocyanines H(2)Pc(alpha-OR)(4) with Ni(acac)(2)2H(2)O in refluxing n-pentanol. Structures of the Langmuir monolayers of these compounds at different temperature have been investigated. Compound 1 formed nano-ring structures with the outer diameter of 70-150 nm and inner diameter of 50 nm at 25.0 degrees C while 2 and 3 formed round particles. This difference can be ascribed to the different substituents at alpha position. The morphologies of the aggregates of 1 in monolayers have been found to change with temperature. Decreasing in temperature induced the formation of regular quadrate crystals. UV-vis absorption spectra revealed strong intermolecular interactions in the nano-ring aggregates. Polarized UV-vis absorption spectra suggest a titled orientation with respect to the surface of substrate for phthalocyanine macrocycles in the nano-ring aggregates.     

Porphyrin, phthalocyanine and porphyrazine derivatives with multifluorenyl substituents as efficient deep-red emitters

The synthesis and photophysical properties are described for a series of porphyrin, phthalocyanine and pyrazinoporphyrazine derivatives which bear four or eight peripheral fluorenyl substituents as antennae. Representative examples are 5,10,15,20-tetra(9,9-dihexyl-9H-fluoren-2-yl)porphyrin (2), 5,10,15,20-tetrakis[4-(9,9-dihexyl-9H-fluoren-2-yl)phenyl]porphyrin (3), 2,3,9,10,16,17,23,24-octakis(9,9-dihexyl-9H-fluoren-2-yl)-29H,31H-phthalocyanine (8) and 2,3,9,10,16,17,23,24-octakis[4-(9,9-dihexyl-9H-fluoren-2-yl)phenyl]-29H,31H-tetrapyrazinoporphyrazine (9). Palladium-mediated Suzuki-Miyaura cross-coupling reactions have been key steps for attaching the substituents. The compounds are deep-red emitters: lambda(max)(em)=659 (3), 737 (8) and 684 nm (9). Their absorption and emission spectra, their fluorescence lifetimes and quantum yields are correlated with the structures of the macrocycles and the substituents. The solution fluorescence quantum yields of porphyrin derivatives substituted with fluorene (2-4) and terphenyl substituents (7) (Phi(f)=0.21-0.23) are approximately twice that of tetraphenylporphyrin. For phthalocyanine derivative 8, Phi(f) was very high (0.88). Specific excitation of the fluorene units of 8 produced emission from both of them (lambda(max)=480 nm) and also from the phthalocyanine core (lambda(max)=750 nm), indicating a competitive rate of energy transfer and radiative decay of the fluorenes. Organic light-emitting devices (OLEDs) were made by spin-coating techniques by using a polyspirobifluorene (PSBF) copolymer as the host blended with 3 (5 wt. %) in the configuration ITO/PEDOT:PSS/PSBF copolymer:3/Ca/Al. Deep-red emission (lambda(max)=663 nm; CIE coordinates x=0.70, y=0.27) was observed with an external quantum efficiency of 2.5 % (photons/electron) (at 7.5 mA cm(-2)), a low turn-on voltage and high emission intensity (luminance) of 5500 cd m(-2) (at 250 mA/ m(2)).     

Covalently Attached Monolayer of Phthalocyanine on Chemically Modified Silicon Oxide Surface

Highly stable monolayers of 2,9,16,23-tetracarboxyl phthalocyanine on 3-aminopropyl-triethoxysilane (ATS) modified silicon and quartz substrates were prepared by reaction of carboxyl and amine. The monolayers were characterized by UV-Vis spectra and AFM measurements. The results indicated that the ultra-thin films on silicon or quartz were smooth, and the ordered structures were observed in these films.     

Synthesis and electrochemistry of tetrakis(7-coumarinthio-4-methyl)-phthalocyanines,and preparation of their cinnamic acid and sodium cinnamate derivatives

Novel water soluble free-base, Zn(II) and Co(II) metallo phthalocyanines with four cinnamic acid moieties were prepared from the corresponding tetrakis(7-coumarinthio-4-methyl)-phthalocyanine by the lactone ring opening reaction. The new compounds were purified and characterized by elemental analysis, ¹H NMR, Maldi-TOF, FT-IR and UV–Vis spectral data. Cyclic and differential pulse voltammetry and in situ spectroelectrochemistry of the 2,9,16,23-tetrakis(7-coumarinthio-4-methyl) substituted free-base 1a, Zn(II) 1b and Co(II) 1c phthalocyanines, employed as the starting compounds have been studied. This allowed us not only to identify metal- and phthalocyanine ring-based redox processes of the complexes, but also the effect of aggregation on these processes.     

Characterization and physicochemical studies of the conjugates of graphene quantum dots with differently charged zinc phthalocyanines

Unsubstituted zinc phthalocyanine (ZnPc), 2,9,16,23-tetrakis[4-(N-methylpyridyloxy)]-phthalocyanine (ZnTPPcQ) and Zn tetrasulfo phthalocyanine (ZnTSPc) were non-covalently (electrostatic and/or π–π interaction) attached to graphene quantum dots (GQDs) to form GQDs-Pc nanoconjugates. Relative to Pcs alone, the presence of GQDs improved the triplet quantum yields with the following values: GQDs-ZnPc (0.73), GQDs-ZnTPPcQ (0.76) and GQDs-ZnTSPc (0.67). Respective Förster resonance energy transfer (FRET) efficiencies were calculated to be 0.81, 0.80 and 0.28. However, singlet oxygen generating abilities of the as-synthesized nanoconjugates were relatively low due to the screening effect of GQDs and quenching in water. This study shows that, the type of Pc, loading and solvent used are among the vital properties to consider when constructing GQD-nanoconjugate systems with optimal triplet quantum yield properties and investigation of their physicochemical properties.     

Absorption spectrophotometric, fluorescence, transient absorption and quantum chemical investigations on fullerene/phthalocyanine supramolecular complexes

The present paper reports the photophysical investigations on supramolecular interaction of a phthalocyanine derivative, namely, 2,9,16,23-tetra-tert-butyl-29H,31H-Pc (1) with C(60) and C(70) in toluene. The binding constants of the C(60) and C(70) complexes of 1 are estimated to be 27,360 and 25,205 dm(3), respectively. Transient absorption measurements in the visible region establishes that energy transfer from C60*T (and C70*T) to 1 occurs predominantly in toluene which is subsequently confirmed by the consecutive appearance of the triplet states of 1. Quantum chemical calculations at DFT level of theory explore the geometry and electronic structure of the supramolecules and testify the significant redistribution of charge between fullerenes and 1.     

Synthesis, structure, spectroscopic properties, and electrochemistry of (1,8,15,22-tetrasubstituted phthalocyaninato)lead complexes

Three (1,8,15,22-tetrasubstituted phthalocyaninato)lead complexes Pb[Pc(alpha-OR)(4)] [H(2)Pc(alpha-OC(5)H(11))(4) = 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine; H(2)Pc(alpha-OC(7)H(15))(4) = 1,8,15,22-tetrakis(2,4-dimethyl-3-pentyloxy)phthalocyanine; H(2)Pc(alpha-OC(10)H(7))(4) = 1,8,15,22-tetrakis(2-naphthyloxy)phthalocyanine] (1-3) have been prepared as racemic mixtures by treating the corresponding metal-free phthalocyanines H(2)Pc(alpha-OR)(4) (4-6) with Pb(OAc)(2).3H(2)O in refluxing n-pentanol. The molecular structure of Pb[Pc(alpha-OC(5)H(11))(4)] (1) in the solid state has been determined by single-crystal X-ray diffraction analysis. This compound, having a nonplanar structure, crystallizes in the monoclinic system with a P2(1)/c space group. Each unit cell contains two pairs of enantiomeric molecules, which are linked by weak coordination of the Pb atom of one molecule with an aza nitrogen atom and its neighboring oxygen atom from the alkoxy substituent of another molecule, forming a pseudo-double-decker supramolecular structure in the crystals with a short ring-to-ring separation, 2.726 A, and thus a strong ring-ring pi-pi interaction. The decreased molecular symmetry for these complexes has also been revealed by the NMR spectra of 1 and 2. The methyl protons of the 3-pentyloxy and 2,4-dimethyl-3-pentyloxy side chains of 1 and 2, respectively, are chemically inequivalent. In addition to the elemental analysis and various spectroscopic characterizations, these compounds have also been electrochemically studied. Two one-electron oxidations and up to five one-electron reductions have been revealed by cyclic voltammetry (CV) and differential pulse voltammetry (DPV) methods.     

Synthesis,electrochemistry, and <Emphasis Type="BoldItalic">in situ</Emphasis> spectroelectrochemistry of a new water-soluble zinc phthalocyanine substituted with naphthoxy-4-sulfonic acid sodium salt

A new water-soluble zinc phthalocyanine, 2,9,16,23-tetrakis[4-(1-naphthoxy-4-sulfonic acid sodium salt)] phthalocyaninato zinc NhtZnPc, where Nht indicates the naphthoxy-4-sulfonic acid sodium salt, was synthesized and its electrochemical and spectroelectrochemical properties were investigated in DMSO solution. The formation of NhtZnPc was monitored with the UV–vis spectral changes of NhtH₂Pc in MeOH solution. The electrochemical studies showed that NhtZnPc displayed two reduction waves assigned to Pc(3−)/Pc(2−) and Pc(4−)/Pc(3−) couples, while it also showed one oxidation wave which was assigned to Pc(−)/Pc(2−) couples. The half-wave potential of the first reduction is shifted by 0.067 V compared to that of unsubstituted metal-free phthalocyanine (H₂Pc). This result shows that the weak electron-withdrawing sulfonated-naphthoxy groups on macrocyle core make the reduction processes of NhtZnPc easier in DMSO solution. The spectroelectrochemical results showed that the first reduction product exhibited the characteristic spectral changes corresponding to mono-anionic species of zinc phthalocyanine having long-term stability during the reduction process. But, the second reduction product resulted in unstable di-anionic forms in DMSO.     

Synthesis and electrochemistry of new octa-substituted metal-free and metallophthalocyanines

The synthesis and characterization of metal-free (H₂-Pc) and metal-containing (Zn, Co, and Cu) derivatives of a symmetrically octa-substituted phthalocyanine derived from 4,5-bis[2-(phenylthio)ethoxy]phthalonitrile were carried out by microwave irradiation. The electrochemical properties of the metal-free phthalocyanine 4 and metallophthalocyanine complexes 5 and 6 were investigated by cyclic voltammetry and differential pulse voltammetry. We have previously investigated the electrochemical properties of the tetra substituted 2-(phenylthio)ethoxy phthalocyanines. The reduction potential of the octa-substituted metal-free phthalocyanine shifted to more negative potential as a result of the electron donating of the 2-(phenylthio)ethoxy groups on the periphery compared to those of tetra substituted. The H₂Pc and ZnPc demonstrated ligand-based electron transfer processes, while CoPc complex has a metal-based reduction process. Similar aggregation behavior was observed for octa-substituted phthalocyanines. The compounds were characterized using IR, ¹H NMR, ¹³C NMR, elemental analysis, and MS spectral data.     

Structure of synthetic transmembrane lipid membranes at the solid/liquid interface studied by specular X-ray reflectivity

We fabricated a new class of supported membranes based on monolayers of artificial bola (transmembrane) lipids. The lipids used in this study are symmetric bola lipids with two phosphocholine head groups, which resemble natural archaea lipids. To prevent bending of the hydrocarbon chains, stiff triple bonds are inserted in the middle of the hydrocarbon cores. The formation of homogeneous "monolayers" of transmembrane lipids over macroscopic areas can be monitored with fluorescence microscopy. Structures of such supported monolayers in bulk water were characterized with specular X-ray reflectivity using high energy X-ray radiation, which guarantees a high transmission through bulk water. Here, the vertical structure of single monolayers could be resolved from reconstructed electron density profiles. To verify the structural model suggested by the specular reflectivity, we also performed small- and wide-angle X-ray scattering of transmembrane lipid suspensions. The wide-angle patterns reflect a distorted chain-chain correlation, while the small-angle scattering allowed us to model an electron density profile which is consistent with the profile calculated from specular reflectivity.     

Structures and properties of 1,8,15,22-tetrasubstituted phthalocyaninato-lead complexes: the substitutional effect study based on density functional theory calculations

Density functional theory (DFT) and time-dependent DFT calculations were carried out to comparatively describe the molecular structures, molecular orbital energy gaps, atomic charges, infrared (IR) and Raman spectra, and UV-vis spectra of PbPc (1), PbPc(alpha-OC2H5)4 (2), and PbPc(alpha-OC5H11)4 (3) {Pc2- = dianion of phthalocyanine; [Pc(alpha-OC2H5)4]2- = dianion of 1,8,15,22-tetra-ethoxyphthalocyanine; [Pc(alpha-OC5H11)4]2- = dianion of 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine}. The calculated structural data of compounds 1 and 3 and the simulated IR and UV-vis spectra of 3 are compared with X-ray crystallography molecular structures and the experimental absorption spectra respectively to verify the performance of the B3LYP method and the LANL2DZ basis set. Substitution of bulky alkoxy groups at the nonperipheral positions of the phthalocyanine ring adds obvious effect to the molecular structure of phthalocyaninato lead compounds by deflecting the isoindole units in the direction that the isoindole units extends and distorting them in the C4 axis direction due to the steric hindrance. Both the calculated IR and UV-vis absorption spectra of 3 correspond well with the experimental results.     

Review on grazing incidence X-ray spectrometry and reflectometry

Grazing incidence X-ray techniques are now widely used for surface and thin film analysis. The present article overviews the recent advancement since 1993 of the grazing incidence X-ray spectrometry and reflectometry in both theoretical and experimental aspects. Every current topic related to the total reflection X-ray fluorescence spectrometry (TXRF) is described in detail through the introduction of numerous published works on the application in the various fields of the science and industrial technologies. Recent rapid growth in diffuse scattering at grazing incidence as well as in specular reflection is another important scope. The combined measurements of different grazing incidence X-ray techniques might be a future trend for realizing further advanced analysis of the surface and interfaces of materials.     

Controlling the nature of mixed (phthalocyaninato)(porphyrinato) rare-earth(III) double-decker complexes: the effects of nonperipheral alkoxy substitution of the phthalocyanine ligand

The half-sandwich rare-earth complexes [M(III)(acac)(TClPP)] (M = Sm, Eu, Y; TClPP = meso-tetrakis(4-chlorophenyl)porphyrinate; acac = acetylacetonate), generated in situ from [M(acac)3] x n H2O and H2(TClPP), were treated with 1,8,15,22-tetrakis(3-pentyloxy)phthalocyanine [H2{Pc(alpha-OC5H11)4}] (Pc = phthalocyaninate) under reflux in n-octanol to yield both the neutral nonprotonated and protonated (phthalocyaninato)(porphyrinato) rare-earth double-decker complexes, [M(III){Pc(alpha-OC5H11)4}(TClPP)] (1-3) and [M(III)H{Pc(alpha-OC5H11)4}(TClPP)] (4-6), respectively. In contrast, reaction of [Y(III)(acac)(TClPP)] with 1,4,8,11,15,18,22,25-octakis(1-butyloxy)phthalocyanine [H2Pc(alpha-OC4H9)8] gave only the protonated double-decker complex [Y(III)H{Pc(alpha-OC4H9)8}(TClPP)] (7). These observations clearly show the importance of the number and positions of substituents on the phthalocyanine ligand in controlling the nature of the (phthalocyaninato)(porphyrinato) rare-earth double-deckers obtained. In particular, alpha-alkoxylation of the phthalocyanine ligand is found to stabilize the protonated form, a fact supported by molecular-orbital calculations. A combination of mass spectrometry, NMR, UV-visible, near-IR, MCD, and IR spectroscopy, and X-ray diffraction analyses, facilitated the differentiation of the newly prepared neutral nonprotonated and protonated double-decker complexes. The crystal structure of the protonated form has been determined for the first time.     

SYNTHESIS AND PHOTOCYTOTOXICITY OF SOME NEW SUBSTITUTED PHTHALOCYANINES

Some new, ring-substituted phthalocyanines have been synthesized and underwent preliminary testing for photodynamic activity using the colony forming ability of Chinese hamster cells in culture as an endpoint. Using 4-(3-N,N-diethylaminopropyl)phthalonitrile as a precursor, the previously unknown metal-free 2,9,16,23-tetra-(3-N,N-diethylaminopropyl)phthalocyanine was prepared and converted to its zinc (II) and its cationic water-soluble 2,9,16,23-tetramethylammonium zinc (II) iodide derivatives. Other new phthalocyanine derivatives tested, include a 2,9,16,23-tetra(2-hydroxymethyl-2-methylbutoxy)phthalocyaninato zinc (II) and 2,3,9,10,16,17,23,24-octahydroxyphthalocyaninato zinc (II) derivatives. Boron tribromide cleavage of the newly prepared and fully characterized 2,3,9,10,16,17,23,24-octamethoxyphthalocyanine gave the unstable metal-free octahydroxyphthalocyanine, which could only be characterized by ultraviolet-visible, NMR and IR spectroscopy.     

LB films of rodlike phthalocyanine aggregates: specular X-ray reflectivity studies of the effect of interface modification on coherence and microstructure

We present here X-ray specular reflectivity (XRR) characterization of the ordering of Langmuir-Blodgett films of the liquid crystalline phthalocyanine (Pc) 2,3,9,10,16,17,23,34-octakis(2-benzyloxyethoxy)copper(II) phthalocyanine, 1, on Si(100) wafers with a native oxide layer and these same substrates modified with monolayers of varying percentages of methyl- and phenyl-terminated silanes. The central copper atom in these Pc's provides for high contrast in X-ray reflectivity for single-bilayer films of 1. The XRR data are modeled as arising from multiple layers of organic material, above and below the rows of copper atoms in the aligned Pc cores; variations in the total thickness of these films, and the spacing between the rows of copper atoms, are attributed to changes in the interaction with the substrate, and changes in the Pc orientation and side chain packing. The most pronounced effect on these parameters comes from variations in the ratio of the phenyl-silane versus methyl-silane content of the substrate modifiers and annealing of these films past their crystalline (K) --> liquid crystalline (LC) mesophase transition temperature. Transfer of multiple bilayers of this Pc leads to additional changes in the thickness of each layer, eventually forming a hexagonal close-packed array, reminiscent of bulk fibers of this material, as revealed by X-ray diffraction (XRD).     

Octalkoxy-substituted phosphorus(V) triazatetrabenzcorroles via ring contraction of phthalocyanine precursors

As part of efforts toward developing the synthesis of novel corrole analogues, the new triazatetrabenzcorrole (TBC) phosphorus(V) compounds (BuO)8(TBC)P(OCH3)2 (3), [(BuO)8(TBC)P(OH)]+OH- (4) ((BuO)8TBC=3,6,10,13,17,20,24,27-octabutoxytriazatetrabenzcorrolate), and [(BuO)8Cl8(TBC)P(OH)]+OH- (7) ((BuO)8Cl8TBC=3,6,10,13,17,20,24,27-octabutoxy-4,5,11,12,18,19,25,26-octachlorotriazatetrabenzcorrolate) were prepared. These TBCs were synthesized via a ring-contraction reaction mediated by PBr3 in pyridine in which a meso-nitrogen atom is extruded from an appropriate phthalocyanine precursor. Two of the compounds prepared, 3 and 4, are contracted analogues of the parent phthalocyanine (BuO8)PcH2 (1) 1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine, which has been shown for the first time to be susceptible to ring-contraction despite the potential steric crowding imposed by the butoxy substituents. Likewise, the octachloro-substituted (BuO8)Cl8PcH2 (6), 1,4,8,11,15,18,22,25-octabutoxy-2,3,9,10,16,17,23,24-octachlorophthalocyanine, has also been shown to smoothly afford 7 via the same ring-contraction method. In addition, a rare example of a bona fide phosphorus(V) phthalocyanine, [(BuO)8(Pc)P(OCH3)2]+OH- (2), has been prepared for spectroscopic comparisons with the TBC compounds. These molecules are all extremely soluble in common organic solvents because of the octabutoxy substituents and have been characterized in detail by 1H NMR, 31P NMR, UV-vis, MALDI-MS, elemental analysis, and electrochemical studies. A clear trend in the phosphorus chemical shifts for 5 versus 6 coordination has been delineated: 31P NMR for 2, -179.8; 3, -186.1; 4, -105.1; and 7, -105.1. These data are compared to the 31P chemical shifts for related porphyrinoid(P(V)) molecules. The MALDI-MS data reveal the tendency of the TBC macrocycles to ionize as the radical cations (M(+*)) and has been useful in determining the axial ligands at phosphorus. A consequence of ring-contraction is reflected in the dramatic red-shifts (approximately 200 nm) observed for the Soret bands of the TBC compounds relative to the parent phthalocyanines. The magnitude of the red-shift is much greater than that reported for other TBCs. In addition, insertion of phosphorus causes a large red-shift in the Q-band of 2 found at 889 nm compared to 760 nm for 1. Cyclic voltammetry of the compounds in this study reveals multiple oxidation and reduction waves for each compound, and some interesting trends in redox potentials have been observed. The CV data for the octachloro-substituted compounds 6 and 7 show that the Cl substituents have an expected strong electron-withdrawing effect on the macrocycles. In general, the TBC compounds are significantly easier to oxidize and harder to reduce than the Pc counterparts, supporting the notion that corrole-type macrocycles favor higher oxidation states.     

Photophysical and theoretical insights on non-covalently linked fullerene-zinc phthalocyanine complexes

The photo-physical aspects of non-covalently linked assemblies of a series of fullerenes, namely, C60, C70, tert-butyl-(1,2-methanofullerene)-61-carboxylate (1) and [6,6]-phenyl C70 butyric acid methyl ester (2) with a designed zinc phthalocyanine (ZnPc), viz., zinc-1,4,8,11,15,18,22,25-octabutoxy-29H,31H-phthalocyanine (3) in toluene medium are studied employing absorption spectrophotometric, steady state and time resolved fluorescence spectroscopic measurements. Of central interest in these investigations is the preferential binding of various fullerenes with ZnPc in toluene. The ground state interaction between fullerenes and 3 is first evidenced from UV-Vis measurements. Steady state fluorescence experiment reveals efficient quenching of the excited singlet state of 3 in presence of both underivatized and derivatized fullerenes. K values for the complexes of C60, C70, 1 and 2 with 3 are determined to be 6500, 22,230, 47,800 and 54,770 dm3 mol(-1), respectively. The magnitude of K suggests that 3 preferentially binds C70 and derivatized C70 in comparison to C60 and 1. Time resolved emission measurements establish that C(70)-3 and 2-3 complexes are stabilized much more in comparison to C(60)-3 and 1-3 systems in terms of charge separation process. Semi empirical calculations employing third parametric method substantiate the strong binding of C70 and its derivative with 3 in terms of heat of formation values of the respective complexes, and at the same time, determine the orientation of bound guest (here fullerenes) with the molecular plane of 3.