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A novel pyrrolopyrrole azadipyrrin (Janus-PPAD) with Janus duality was synthesized by a Schiff base-forming reaction of diketopyrrolopyrrole. The orthogonal interactions of the hydrogen-bonding ketopyrrole and metal-coordinating azadipyrrin moieties in Janus-PPAD enabled the metal ions to be arranged at regular intervals: zinc(II) and cobalt(II) coordination provided metal-coordinated Janus-PPAD dimers, which can subsequently form hydrogen-bonded one-dimensional arrays both in solution and in the solid state. The supramolecular assembly of the zinc(II) complex in solution was investigated by 1 H NMR spectroscopy based on the isodesmic model, in which a binding constant for the elongation of assemblies is constant. Owing to the tetrahedral coordination, in the solid state, the cobalt(II) complex exhibited a slow magnetic relaxation due to the negative D value of -27.1 cm-1 with an effective relaxation energy barrier Ueff of 38.0 cm-1 . The effect of magnetic dilution on the relaxation behavior is discussed. The relaxation mechanism at low temperature was analyzed by considering spin lattice interactions and quantum tunneling effects. The easy-axis magnetic anisotropy was confirmed, and the relevant wave functions were obtained by ab initio CASSCF calculations.

The presence of a new electronic interaction, which couples a 4 f-electronic system with a total angular momentum J and a photoexcited cyclic π-conjugated system with an orbital angular momentum L, in the bis(phthalocyaninato)dysprosium single-molecule magnet ([DyPc2 ]- ) is reported. Two π-π* excited states in the visible spectral region of the [DyPc2 ]- complex, which are denoted here as QL and QH , showed significantly different temperature and field dependences of the magnetic circular dichroism (MCD) A-term intensity. This phenomenon not only indicates the presence of a "J-L" interaction, but also that the interaction generates two different preferred orientations of the J-L pair, either parallel (for the QH band) or antiparallel (for the QL band), depending on the excitation energy. We have constructed a theoretical model that reproduces the temperature and field dependences, and quantitatively evaluated the J-L interaction.

Magnetic f-π interactions between localized 4f-electrons and itinerant π-electrons have been observed in a single crystal of bisphthalocyaninato yttrium(iii)/terbium(iii) tetrafluoroborate ([Pc2Y0.95Tb0.05][BF4]) by measuring electrical conductivity of the crystal in the presence of an external magnetic field.

A series of heavy lanthanide(III) and yttrium(III) monoporphyrinato complexes formulated in [Ln(TPP)(cyclen)]Cl (Ln = Tb, Dy, Ho, Er, Tm, Yb, and Y; TPP = 5,10,15,20-tetraphenylporphyrinato), with cyclen, 1,4,7,10-tetraazacyclododecane, as a capping ligand, have been prepared in mild conditions and studied using single-crystal X-ray diffraction crystallography. The complexes exhibit an electronic absorption band (B(0,0)) in the range of 421–423 nm, showing a bathochromic shift associated with the increase of the ionic radii of the lanthanide, as well as two peaks of Q(1,0) and Q(0,0) bands between 548–586 nm. All of the complexes are isostructural, where both TPP and cyclen are coordinated to a lanthanide(III) or yttrium(III) ion giving an eight-coordinate square-antiprismatic (SAP) geometry (average skew angles are in the range of 43.01°–43.67°). The mean plane of the four nitrogen atoms of TPP (N4t) and that of the cyclen (N4c) are virtually parallel with a dihedral angle of less than 1°. The lanthanide...

The first detection and characterization of magnetic interaction between two 4f electronic systems in the dinuclear "inverted-sandwich-type" phthalocyanine complex with terbium ions and that of dysprosium ions are presented. Temperature dependent magnetic measurements for the diterbium complex, (μ-phthalocyaninato)bis[di(2,2,6,6-tetramethylheptane-3,5-dionato)terbium], show that the value of magnetic susceptibility times temperature, χT, sharply decreases as temperature is lowered, indicating the presence of an antiferromagnetic-type interaction between the Tb 3+ ions in the dinuclear complex. Similar temperature dependence was observed for the corresponding dinuclear dysprosium complex. These results are completely opposite to those observed for Pc triple-decker dinuclear terbium or dysprosium complexes, which are known to function as single molecule magnets. The NMR signals for the protons on the Pc ligand of the diterbium complex show up-field paramagnetic shifts due to the partially-filled 4f shells of the metal ions. This again makes sharp contrast to the triple-deckers, for which large down-field paramagnetic shifts are observed. These intriguing results seen in the NMR and magnetic susceptibility measurements are explained assuming the ligand field potential of the inverted-sandwich complexes gives strong easy-plain-type magnetic anisotropy, where Jz value of the lowest sublevel has a small value, while sandwich-type Pc3Ln2 ( Ln = Tb or Dy ) complexes have a strong easy-axis-type magnetic anisotropy.

A trivalent manganese complex of a non-planar 1,4,8,11,15,18,22,25-octaphenylphthalocyanine derivative, 3, has been synthesized by treating metal-free 1,4,8,11,15,18,22,25-octaphenylphthalocyanine, 2, with manganese(II) chloride in refluxing DMF. X-ray crystallography has revealed that the complex adopts a highly-deformed skeletal conformation due to steric congestions between the substituted bulky phenyl groups. Although mass spectrometry results provide no indication of the presence of axial ligands, the crystal data clearly show that the manganese ion is coordinated axially by a chloride ion in addition to the four equatorial isoindole nitrogen atoms. The oxidation state of the manganese center of 3, therefore, has been assigned to 3+. Electronic absorption spectra revealed that the Q-band of 3 shows a significant bathochromic shift compared to that of the planar Mn ( III ) phthalocyanine 4 and non-planar metal-free phthalocyanine 2. The analysis of MCD and UV-vis spectra suggests that the absorption band observed at 555 nm for 3 is LMCT in origin. Electrochemical investigations indicate that the first oxidation couple is ligand-centered. Since the HOMO of 2 is destabilized due to the synergetic effects of the electron-donating phenyl groups at the non-peripheral positions and the deformed π-electronic skeleton, the resulting manganese complex 3, is anticipated to also have a ligand-centered HOMO. The results of spectroelectrochemistry confirm that the first oxidation process of 3 is indeed ligand-centered. DFT calculations indicate that the MO amplitudes of the HOMO and LUMO localize mainly on the Pc ligand and the manganese ion, respectively, also supporting the assignments of the cyclic voltammograms. By combining the manganese ion and non-planar Pc ligand, a novel, stable near-infrared (NIR)-absorbing material has been achieved in the present study.

Electrocatalytic properties of cobalt phthalocyanine (CoPc), cobalt tetra-carboxy phthalocyanine (CoTCPc) and cobalt octa-carboxy (CoOCPc), towards the detection of dicrotophos have been studied. Catalytic behavior towards the reduction of dicrotophos was found to be dependent on the pH, as well as the substitution on the phthalocyanine ring. Strong electron withdrawing groups on the phthalocyanine ring yielded best catalysis as evidenced by the enhancement of the reduction peak current, (~5 fold) compared to the bare glassy carbon electrode. The analysis gave a good detection limit of 1.25 × 10-7 M, and good linearity for the studied concentration range. A high Tafel slope value was obtained, indicating a strong interaction between dicrotophos and the cobalt phthalocyanine complex.

The tetramerization reaction of 2,5-diphenyl-3,4-dicyanothiophene (2) proceeded on treatment with ruthenium(III) trichloride, DBU, and 4-methylpyridine in 2-ethoxyethanol at 135 °C to give bis(4-methylpyridine)[1,3,5,7,9,11,13,15-octaphenyltetra(3,4-thieno)tetraazaporphyrinato]ruthenium(II)(3). Because the structure of this product cannot be represented by a usual bonding system, this molecule has to contain an unusual tetravalent sulfur atom in one of the four thiophene rings. In the 1H NMR spectrum of the product, signals from 4-methylpyridine coordinated to the central ruthenium atom showed an upfield shift. The structure of 3 was determined by X-ray crystallography, which revealed that 3 has four thiophene units linked at their 3,4-positions to the tetraazaporphyrin scaffold. Four pairs of phenyl groups are in close proximity and are sterically congested, which causes the four thiophene rings to deviate from the mean plane of the central four pyrrole nitrogen atoms. The UV/Vis spectrum of 3 shows a Q-band absorption at λmax = 758 nm. In the MCD spectrum of 3, dispersion-type absorptions (Faraday A term) are observed at 746 and 776 nm. The MCD spectra suggest that the two LUMOs of 3 could be degenerate even though its structure deviates from D4h symmetry. The electrochemical properties of 3 were examined by cyclic voltammetry with Ag/AgNO3 as the reference electrode. The optimized structure and the NMR shielding constants of a simplified model molecule were calculated by using density functional theory.

The reaction of phthalonitrile and lithium methoxide at 70 °C in methanol yields a half-phthalocyanine intermediate, which coordinates to a zinc(II) ion in a subsequent reaction step to afford a no...

The integration of phenylamine-functionalised SWCNTs (SWCNT-phenylamine) with a novel cobalt (II) octa[(3,5-biscarboxylate)-phenoxy] phthalocyanine (CoOBPPc) complex has been described. The physical and electrochemical properties of the CoOBPPc-SWCNT-phenylamine hybrid were evaluated using spectroscopy (IR and UV–vis), field emission scanning electron microscopy and electrochemistry (cyclic voltammetry and electrochemical impedance spectroscopy). Integration of SWCNT-phenylamine resulted in the physical transformation of the CoOBCPPc from the usually bluish colour of cobalt phthalocyanine complexes to a beautiful bright green colour. In addition, the heterogeneous electron transfer kinetics and electrocatalytic properties of the CoOBCPPc were greatly enhanced following the attachment of the SWCNT-phenylamine. The potential electrocatalytic application of the hybrid was tested using β-nicotinamide adenine dinucleotide (NADH) as a model biological analyte. Interestingly, the onset oxidation potential of this analyte was significantly reduced (300 mV) by this hybrid compared to the bare electrode.

Novel hexabutylsulphonyltribenzotetraazachlorin–fullerene (C60) complexes of iron (FeHBSTBTAC–C60) and cobalt (CoHBSTBTAC–C60) have been synthesized and their electrochemistry and oxygen reduction reaction (ORR) compared with their octabutylsulphonylphthalocyanine analogues (FeOBSPc and CoOBSPc). It is proved that electron-withdrawing substituents (–SO2Bu and C60) on phthalocyanine macrocycle exhibit distinct impact on the solution electrochemistry of these metallophthalocyanine (MPc) complexes. The more electron-withdrawing C60 substituent suppressed ORR compared to the –SO2Bu in alkaline medium. FeOBSPc showed the best ORR activity involving a direct 4-electron mechanism, a rate constant of ∼1 × 108 cm3 mol−1 s−1 and a Tafel slope of −171 mV dec−1. Keywords: Metal (Fe, Co) phthalocyanine–C60, Cyclic voltammetry, RDE experiment, Oxygen reduction

Two sandwich-type heteroleptic tetrapyrrole cerium complexes, Ce2(dap)2(pc) (1) [dap = 2,8,12,18-tetraethyl-3,7-13,17-tetramethyl-5,15-diazaporphyrinate; pc = phthalocyaninate] and Ce(dap)(oep) (2) (oep = octaethylporphyrinate), were prepared by a one-pot reaction of [Ce(acac)3]·nH2O (acac = acetylacetonate), metal-free diazaporphyrin H2dap, and Li2pc or H2oep in refluxing 1,2,4-trichlorobenzene. These sandwich double- and triple-decker complexes were characterized by a wide range of spectroscopic methods in addition to elemental analysis. Their electrochemistry was also studied by cyclic voltammetry and differential pulse voltammetry. The molecular structure of Ce2(dap)2(pc) (1) was determined by X-ray diffraction analysis, indicating an unexpected asymmetrical disposition of the ligands, with two adjacent dap moieties and one outer pc ring.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009)

Unexpected formation of seco-tribenzoporphyrazines from nickel- or palladium-template macrocyclization reaction of 1,3-diiminoisoindoline as a sole starting material has opened a novel access to this class of molecules. Seco-tribenzoporphyrazines exhibit strongly-split Q band absorption, basically typical of tetraazachlorin-like electronic structures, which are discussed in detail based on UV–Vis absorption and magnetic circular dichroism spectroscopies and theoretical calculations.

The first β-oxatetraazachlorin derivatives have been synthesized starting from phthalonitrile derivatives and 5,5-dimethyl-1,3-oxazolidine-2,4-dione instead of the previously employed tetramethylsuccinonitrile. Absorption and magnetic circular dichroism (MCD) spectral properties are similar to those obtained for the corresponding tetramethyl-substituted TAC derivatives, confirming the presence of the low-symmetry aromatic structures.

Absorption spectral changes observed during sodium mirror reduction of tribenzotetraazachlorin–fullerene (TBTAC–C60) conjugates have clarified that electronic communication between the TBTAC and C60 moieties is switched off upon reduction of the conjugates. Spectroscopy has suggested that the anionic species retains its aromatic character.

A sterically congested tetraphenyl-substituted dibenzo-tetraaza-isobacteriochlorinato nickel derivative unexpectedly reacts with methanol at room temperature to release internal molecular strains, leading to the formation of a ligand having a skeleton bearing two cis-methoxy substituents.

Free base and zinc 1,4,8,11,15,18,22,25-octa(p-methoxyphenyl) phthalocyanine have been synthesized. The Q-bands are located beyond 800 nm due to combined effects of red-shifts caused by ligand deformation and the electron-donating properties of the methoxy substituents. The phthalocyanines reported in this study could potentially replace naphthalocyanines as absorbers in the 800 nm region within practical applications.

Nuclear spin driven quantum tunneling of magnetization (QTM) phenomena, which arise from admixture of more than two orthogonal electronic spin wave functions through the couplings with those of the nuclear spins, are one of the important magnetic relaxation processes in lanthanide single molecule magnets (SMMs) in the low temperature range. Although recent experimental studies have indicated that the presence of the intramolecular f-f interactions affects their magnetic relaxation processes, little attention has been given to their mechanisms and, to the best of our knowledge, no rational theoretical models have been proposed for the interpretations of how the nuclear spin driven QTMs are influenced by the f-f interactions. Since quadruple-decker phthalocyanine complexes with two terbium or dysprosium ions as the magnetic centers show moderate f-f interactions, these are appropriate to investigate the influence of the f-f interactions on the dynamic magnetic relaxation processes. In the present paper, a theoretical model including ligand field (LF) potentials, hyperfine, nuclear quadrupole, magnetic dipolar, and the Zeeman interactions has been constructed to understand the roles of the nuclear spins for the QTM processes, and the resultant Zeeman plots are obtained. The ac susceptibility measurements of the magnetically diluted quadruple-decker monoterbium and diterbium phthalocyanine complexes, [Tb-Y] and [Tb-Tb], have indicated that the presence of the f-f interactions suppresses the QTMs in the absence of the external magnetic field (H(dc)) being consistent with previous reports. On the contrary, the faster magnetic relaxation processes are observed for [Tb-Tb] than [Tb-Y] at H(dc) = 1000 Oe, clearly demonstrating that the QTMs are rather enhanced in the presence of the external magnetic field. Based on the calculated Zeeman diagrams, these observations can be attributed to the enhanced nuclear spin driven QTMs for [Tb-Tb]. At the H(dc) higher than 2000 Oe, the magnetic relaxations become faster with increasing Hdc for both complexes, which are possibly ascribed to the enhanced direct processes. The results on the dysprosium complexes are also discussed as the example of a Kramers system.

Mixed condensation of 1,2-dicyanofullerene (1) and 4,5-dibutyloxyphthalonitrile (2a) in the presence of vanadium(III) chloride (VCl 3 ) in quinoline forms the hexabutyloxy-substituted tribenzotetraazachlorin (TBTAC) - fullerene (C 60 ) vanadyl complex (3). UV-vis absorption and magnetic circular dichroism (MCD) spectroscopy demonstrated that 3 shows two intense Q-band components, whereas the previously reported nickel complex possessing the identical peripheral substituents (4) shows one intense and two medium-intense bands in the 600-800 nm region, indicating that the electronic mixing states of 3 are different from those of the nickel complex (4). The metal effects on electronic structures of the conjugates were interpreted using density functional theory (DFT) calculations.

cis-3,4-Dicyano-3-hexene undergoes cyclotrimerization with BCl3 to form the new subtriazaporphyrin chloro[hexaethylsubtriazaporphyrinato]boron(III). The hydroxo derivative of this macrocycle has also been made, and the X-ray crystal structure of the hydroxy form was determined. Electronic absorption and magnetic circular dichroism spectra of the hydroxo monomer species were interpreted using time-dependent density functional theory calculations.

The synthesis of a series of zinc phthalocyanines partially phenyl-substituted at the 1-, 4-, 8-, 11-, 15-, 18-, 22-, and/or 25-positions (the so-called alpha-positions) is reported. Macrocycle formation based on 3,6-diphenylphthalonitrile, o-phthalonitrile, and zinc acetate predominantly yielded the near-planar disubstituted complex and opposite tetrasubstituted isomer, while the lithium method yielded the sterically hindered hexasubstituted complex and adjacent tetrasubstituted isomer. All compounds have been characterized by 1H NMR, MALDI-TOF-MS, and elemental analysis methods. In addition, crystal structures have been solved for the di-, hexa-, and octasubstituted complexes and the adjacent tetrasubstituted isomer. DFT geometry optimization calculations predict more highly deformed structures than those observed in the crystals. The packing force of the crystals cannot therefore be ignored, particularly for the less phenyl-substituted derivatives. The crystal structures have revealed that overlap of the phenyl groups causes substantial deformation of the phthalocyanine (Pc) ligands within the crystals, while strong pi-pi stacking in the remainder of the Pc moiety lacking phenyl substituents can suppress the impact of the deformation. Absorption spectra show sizable red shifts of the Q-band with increasing number of phenyl groups. Analysis of the results of absorption spectra and electrochemical measurements reveals that a substantial portion of the red shift is attributable to the ring deformations. Molecular orbital calculations lend further support to this conclusion. A moderately intense absorption band emerging at around 430 nm for highly deformed octaphenyl-substituted zinc Pc can be assigned to the HOMO-->LUMO+3 transition, which is parity-forbidden for planar Pcs, but becomes allowed since the ring deformations remove the center of symmetry.

The reaction of a double-decker phthalocyanine (Pc) complex, bis(phthalocyaninato)lutetium ([LuPc(2)](-)), with cadmium acetate at 400 degrees C for 30 min under argon provided the first example of a discrete quadruple-decker Pc complex, 1. The structure of 1 was unambiguously determined through the use of high-resolution mass spectrometry, elemental analysis, and NMR techniques such as (1)H-(1)H COSY, (13)C-(1)H COSY, and NOE experiments. The absorption and magnetic circular dichroism spectra of 1 resembled those of [LuPc(2)](-) and [Lu(2)Pc(3)] rather than those of the neutral double-decker species [LuPc(2)](0), since the formal charge on each Pc moiety is 2-. Electrochemical measurements exhibited a stacking effect based on the delocalization of the holes or electrons introduced by oxidation or reduction, respectively, over the entire complex.

The crystal structure of 5,10,15,20-tetramethyl-21H,23H-porphine vanadium(IV) oxide, VO(TMP), has been determined. Monoclinic, P21/a, a = 14.298(5), b = 13.445(4), c = 19.895(6)A, β = 97.487(2). Z = 8, C24H20N4OV.

A novel μ-oxo hetero dimer of silicon phthalocyanine and silicon naphthalocyanine was synthesized. Its unique optical properties, such as a single Q band, which is unusual for hetero dimer species, and solvatochromic behavior, were revealed to be better interpreted by taking interchromophore interactions into consideration.

A reaction of 1,2-dicyanobenzene and lithium methoxide at 70 °C in methanol yielded the half-phthalocyanine intermediate, which coordinates to a cadmium(II) ion in the subsequent reaction step to give the first example of a six-coordinate phthalocyanine analogue containing a divalent metal ion at the center.

Two terbium ions in a triple-decker complex (Pc)Tb(Pc)Tb(T(p-OMe)PP) (Pc = phthalocyaninato, T(p-OMe)PP = tetra-p-methoxyphenylporphyrinato) have shown sharply different magnetic behaviours depending on symmetry of the coordination polyhedron. The fast quantum tunnelling relaxation process in a square-prismatic site has been revealed to be hindered by magnetic-dipolar coupling between the f-electronic systems.

A novel platinum-based macrocycle, iron(II) tetrakis(diaquaplatinum)octacarboxyphthalocyanine (PtFeOCPc), was synthesised and characterised. The heterogeneous electron transfer and electrocatalytic properties of this functional material towards the oxidation of formic acid have been explored on a graphite electrode platform pre-modified with or without acid-functionalised multi-walled carbon nanotubes (MWCNTs). We prove that PtFeOCPc supported on a MWCNT platform (MWCNT–PtFeOCPc) exhibits enhanced electrochemical response in terms of (i) electron transfer towards outer-sphere redox probe, (ii) catalytic rate constant, and (iii) tolerance towards CO poisoning during formic acid oxidation. The results clearly suggest that the MWCNT–PtFeOCPc is a promising platform for potential application as an electrocatalyst for direct formic acid fuel cell.