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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.

A series of the new monophthalocyaninato lanthanide complexes, [Ln(Pc)(cyclen)]Cl (Ln = Y, Tb, Dy, Ho, Er, Tm, and Yb; Pc = phthalocyaninato; cyclen = 1,4,7,10-tetraazacyclododecane) was synthesized and characterized. The crystallographic study of monophthalocyaninato complexes with a capping macrocyclic ligand having no π-conjugation while keeping the 4-fold symmetry is presented for the first time. All the six complexes were crystallized in a tetragonal structure of the I4mm space group. In addition to this, the Tb complex exhibited a triclinic crystal structure of the P1 space group. All of the complexes are isostructural, where both Pc and cyclen are coordinated to an Ln3+ ion giving an eight-coordinate square-antiprismatic geometry. The skew angle between the Pc and cyclen ligands was 45° in the tetragonal crystals and 41.5° in the triclinic crystal. The metal–nitrogen bond lengths were shorter on the Pc ligand side than cyclen side, presumably due to the difference in the charges of the ligands and...

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.

A new type of electronic interaction which couples two angular momenta, i.e. the angular momentum of a localized 4f system (J) and an orbital angular momentum generated in a cyclic π conjugated system by irradiation with a circularly-polarized light, has been identified in a lanthanide single molecule magnet.

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.

The 4f-electronic structures of the ground multiplet states of a series of lanthanide(iii) monoporphyrinato complexes with a cyclen as the capping ligand [Ln(TPP)(cyclen)]Cl (Ln = Tb, Dy, Ho, Er, Tm, and Yb; TPP = 5,10,15,20-tetraphenylporphyrinato; cyclen = 1,4,7,10-tetraazacyclododecane) have been determined using experimental NMR and magnetic susceptibility data. Magnetic susceptibilities of the microcrystalline samples of [Ln(TPP)(cyclen)]Cl were measured in the range of 1.8-300 K. NMR signals corresponding to the protons on the porphyrin ring show marked paramagnetic shifts (lower = Tb, Dy, Ho, and Yb; higher = Er and Tm) in comparison with the diamagnetic Y congener. A set of ligand-field parameters that simultaneously reproduces the magnetic susceptibilities and the paramagnetic shifts has been determined by using a self-developed multidimensional optimization program. In addition, CASSCF calculations were carried out for further insight into their electronic structures.

Syntheses of a novel pseudotetrahedral four-coordinate mononuclear Co(II) complex that has two halved phthalocyanine moieties as the ligands, [Co(half-Pc)2] (1), and its magnetic properties as a single molecule magnet (SMM) are reported. A one pot reaction of phthalonitrile and lithium methoxide followed by the coordination to a Co(II) ion gave 1 as an orange solid in a moderate yield. X-ray crystallography on 1 reveals tetragonally distorted coordination geometry around the Co(II) ion. The M- HT-1 plots suggest that 1 has large axial magnetic anisotropy. The ac magnetic susceptibility data of the magnetically diluted 1 (dil.1) clearly show that the complex acts as an SMM even in the absence of the external static magnetic field ( Hdc). The influence of intermolecular and intramolecular interactions for the magnetic relaxation behaviors has been discussed by comparison of the magnetic data of 1 and dil.1. The Orbach process is suggested as the predominant mechanism of magnetic relaxations in the high-temperature range, and the Arrhenius plots provide the effective relaxation energy barrier and pre-exponential factor of Ueff = 54.0 cm-1 and τ0 = 3.17 × 10-10 s, respectively. The direct estimation of the axial anisotropic parameter of 1 was successfully performed by high-field, multifrequency ESR measurements up to 55 T and 2.5 THz. The evaluated axial zero-field splitting (ZFS) energy of 57.0 cm-1 is comparable to the Ueff energy, confirming that the magnetic relaxations are initiated by the thermal excitation from the ground | M S⟩ = |±3/2⟩ states to the |±1/2⟩ states in the high-temperature range. The results of the ab initio calculations based on the CAS(7,5) SCF wave functions indicate that the ground states of 1 consist mainly of | M S⟩ = |±3/2⟩ states, while the first excited states are the mixture of | M S⟩ = |+1/2⟩ and |-1/2⟩.

Interactions of three different types of electronic angular momenta, namely, spin, orbital, and total angular momenta from different origins in a photoexcited neutral bis(phthalocyaninato)terbium single-molecule magnet (Pc2Tb, where Pc2- denotes a phthalocyaninato anion) have been studied. We have conducted varied-temperature and varied-magnetic-field magnetic circular dichroism (MCD) measurements on the highest occupied molecular orbital-lowest unoccupied molecular orbital electronic transition in the ligand side of the neutral Pc2Tb to reveal the quantum nature of the system composed of a π-radical with a spin angular momentum S, the 4f system with a total angular momentum J, and the cyclic π conjugate system with a photoinduced orbital angular momentum L. We have constructed a new theoretical model that gives a quantitative agreement to the temperature and magnetic field dependence of MCD. The theoretical analysis revealed that the system takes eight quantum states that can be expressed as | J z S z L z⟩ = |±±±⟩, where the three angular momenta are quantized along the fourfold symmetry axis. Thus, we have identified the existence of the magnetic interactions among the three angular momenta and quantitatively determined their magnitudes for the first time.

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 simple procedure for the preparation of microcrystals of insoluble copper phthalocyanine (CuPc) by thermolysis of a dimethoxy-substituted precursor has been developed. Although the morphologies of the resultant microcrystals are practically independent from initial solution concentrations higher than ca. 0.03 mM of the dimethoxy-precursor, crystals with increased width are obtained with increasing the initial concentration of the precursor.

The synthesis, and spectroscopic and magnetic properties of quadruple-decker phthalocyanines (Pcs) have been reviewed. While the presence of stacked mercury Pc oligomers was proposed as early as 1992, the isolation of a quadruple-decker Pc was first achieved in 2010. Herein, we review how the synthetic strategy for quadruple-decker Pcs has come to be conceived from the recent development of cadmium Pc oligomers, which will be followed by illustration of unique physicochemical properties originating from the structure of the quadruple-decker frameworks. In the spectroscopy section, the electronic structures of the quadruple-decker Pc are discussed based on the theoretical and experimental results. A simple molecular orbital (MO) method predicts that energy gaps among the occupied frontier MOs of the quadruple-decker Pc become smaller than those of double- or triple-decker Pcs, leading to the observation of exceptionally low-lying electronic transitions for the oxidized quadruple-decker Pcs. It has been confirmed that the corresponding lowest π–π* electronic transitions reach the infrared region for the one-electron oxidized quadruple-decker Pcs. In the magnetic property section, a clear evidence of the long-range magnetic dipole–dipole f–f interactions between two f-electronic centers of diterbium quadruple-decker Pc is provided, and its magnetic relaxation phenomena arising mainly from quantum tunneling magnetizations (QTMs) will be discussed by using the alternate current (ac) magnetic susceptibility data, and the numerically calculated Zeeman diagram of the f-electronic centers in the quadruple-decker Pc.

We fabricated copper phthalocyanine (CuPc)-based organic photovoltaic (OPV) devices via a solution process. CuPc was obtained through thermal conversion of its precursor CuPc(OMe) 2 , which has excellent solubility in various organic solvents, on a substrate. Solvent-dependent performance of the resulting devices was observed, which could be explained by considering film morphology. Using a 1:2 (wt/wt) mixture of chlorobenzene and chloroform produced a p–n type OPV device with a power conversion efficiency of 1.35% under 1 sun simulated AM1.5G solar illumination.

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.

New covalently C(60)-conjugated phthalocyanine (Pc) analogues in which the Pc and C(60) components are connected by means of a four-membered ring have been synthesized by taking advantage of a [2+2] cycloaddition reaction of C(60) with benzyne units generated from either a phthalocyanine derivative (8) or its precursor (1). The reaction of 1 with PhI(OAc)(2) and trifluoromethanesulfonic acid (TfOH) followed by the [2+2] cycloaddition of C(60) in the presence of tetra-n-butylammonium fluoride (TBAF) yielded the C(60)-substituted Pc precursor (3). Mixed condensation of 3 and 4,5-dibutylsulfonylphthalonitrile (4) in a thermally promoted template reaction using a nickel salt successfully gave the Pc-C(60) conjugate (5). Results of mass spectrometry and (1)H and (13)C NMR spectroscopy clearly indicate the formation of the anticipated Pc-C(60) conjugate. Direct coupling of C(60) with the Pc analogue that contained eight peripheral trimethylsilyl (TMS) groups (8) also proceeded successfully, such that mono and bis C(60)-adducts were detected by their mass, although the isolation of each derivative was difficult. The absorption and magnetic circular dichroism (MCD) spectra of 5 and the reference compound (7) differ from each other in the Q-band region, thereby suggesting that the presence of the C(60) moiety affects the electronic structure of the conjugate. The reduction and oxidation potentials of 5 and 7 obtained by cyclic voltammetry are comparative, except for the C(60)-centered reduction couple at -1.53 V versus Fc(+)/Fc in o-dichlorobenzene (o-DCB). A one-electron reduction of 5 and 7 in tetrahydrofuran (THF) by using the sodium mirror technique results in the loss of band intensity in the Q-band region, whereas the characteristic marker bands for Pc-ring-centered reduction appear at around 430, 600, and 900 nm for both compounds. The final spectral shapes of 5 and 7 upon the reduction resemble each other, thus indicating that no significant molecular orbital (MO) interactions between the C(60) and Pc units are present for the reduced species of 5. In contrast, the oxidized species of 5 and 7 generated by the addition of NOBF(4) in CH(2)Cl(2) show significantly different absorption spectra from each other. Whereas the broad bands at approximately 400-550 nm of 7(+) are indicative of the cationic π-radical species of metallo-Pcs and can be assigned to a transition from a low-lying MO to the half-filled MO, no corresponding bands were observed for 5(+). These spectral characteristics have been tentatively assigned to the delocalized occupied frontier MOs for 5(+). The experimental results are broadly supported by DFT calculations.

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...

Copyright: 2010 Elsevier. This is an ABSTRACT ONLY. The definitive version is published in Electrochimica Acta, vol. 55(22), pp 6367-6375, doi:10.1016/j.electacta.2010.06.056

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.

New covalently C60-connected zinc phthalocyanine (ZnPc) derivatives have been synthesized by utilizing successive cycloaddition reactions of C60 with a ZnPc derivative containing a pyridazine moiety employing Komatsu's method in reaction of C60 with phthalazine. The UV/Vis absorption spectrum of the fused conjugate (5) shows red shifts from the corresponding absorption of ZnPc derivative (8), indicating interactions between the ZnPc and C60 moieties. The DFT calculations under non-polar medium predict that the HOMO and LUMO of 5 localize on the ZnPc moiety, whereas LUMO+1 localizes on the C60 moiety, which reasonably explain the magnetic circular dichroism (MCD) and absorption spectra in toluene. Electrochemical redox potentials of 5 in polar solvents indicate the first-oxidation potential arises from the ZnPc moiety, whereas the first reduction potential is associated with the C60 moiety, suggesting the LUMO localizes on the C60 moiety in polar solvent. This reversal of the LUMO is supported by the ZnPc-fluorescence quenching with a nearby C60 moiety in benzonitrile, which leads to the charge-separation via the excited singlet state of the ZnPc moiety. In toluene on the other hand, such a ZnPc-fluorescence quenching owing to the photoinduced charge separation is not observed as predicted by the DFT-calculated LUMO on the ZnPc moiety.

Mixed condensation of 1,2-dicyanofullerene (1) and 3,6-dibutyloxyphthalonitrile (2a) in the presence of nickel chloride dihydrate ( NiCl2·2H2O ) in quinoline forms an α-hexabutyloxy-substituted tribenzotetraazachlorin (TBTAC)-fullerene ( C 60) conjugate (3). UV-vis absorption and magnetic circular dichroism (MCD) properties of 3 have been obtained, and the results compared with those of the β-substituted isomer (4). Although the absorption spectra of 3 and 4 are similar in shape, a significant band shift to longer wavelength is observed for 3. According to the results of DFT calculations, the observed spectroscopic differences are ascribed to differences in the distribution of the MO amplitudes at the α- and β-positions of the TBTAC moiety.

We introduce some representative studies from our laboratory, mostly from the 21st Century. We are interested in the synthesis, optical spectroscopy, such as magnetic circular dichroism (MCD), circ...

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

Mixed condensation of tetramethylsuccinonitrile and either 2,3-dicyano-5,6-diethylpyrazine, 2,3-dicyanopyridine, or 3,4-pyridinedicarboximide in the presence of nickel chloride forms novel pyrazine-, 2,3-pyridine-, or 3,4-pyridine-ring-fused tetraazachlorin (TAC), tetraazabacteriochlorin (TABC), and tetraazaisobacteriochlorin (TAiBC) derivatives. All possible structural isomers were separated using repeated thin-layer chromatography and have been investigated by absorption and magnetic circular dichroism spectroscopy. Similarly to previously reported TAC analogues, the TAC and TABC derivatives show large splitting of the Q band, while a single, intense absorption band is observed for the TAiBC derivatives. Although the absorption spectra are practically identical in shape for the separated structural isomers of TACs and TABCs, the Q-band maxima of the TAiBCs depend significantly on their structures. The observed spectroscopic properties were interpreted on the basis of electrochemical data and the results of (time-dependent) DFT calculations.

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)

Porphyrins (Por) and phthalocyanines (Pc) exhibit lightharvesting efficiency for producing charge-separated states as models of the reaction center in photosynthetic bacteria and photovoltaic cells for energy conversion. The use of supramolecular assemblies to model the functionality of the reaction center is an attractive and fruitful strategy to develop photofunctional materials and devices. Porphyrins exhibit strong Soret bands around 400 to 450 nm, whereas phthalocyanines show strong Q bands around 700 to 800 nm. Thus, the combination of those two p systems can cover nearly the whole range of the visible region and can be a useful strategy for development of photofunctional materials for efficient light-energy conversion. Attempts have so far been made to synthesize covalently linked Por–Pc heterodyad molecules and construct Por–Pc heterosupramolecules. Recently, ZnPor and ZnPc have been reported to form two-dimensional arrays on gold surfaces, and the formation of a cofacial ZnPor–ZnPc coordination tetrad has also been reported. However, a crystal structure determination of a discrete supramolecular assembly composed of both Por and Pc has yet to be reported. In addition, since the Q-band absorption of Pc usually overlaps the wavelength of fluorescence of Por, energy transfer is favored over electron transfer in most heterodyads. We have developed supramolecular assemblies based on a saddle-distorted nonplanar porphyrin, dodecaphenylporphyrin (H2DPP), and its metal complexes. [11–13] The saddle distortion facilitates protonation of pyrrole nitrogen atoms to allow access to a stable diprotonated porphyrin, which can act as an electron acceptor. In addition, the saddle distortion affords higher Lewis acidity at the metal center to maintain axial coordination of ligands, as a result of poor overlap of the pyrrole nitrogen lone pair orbitals with d orbitals of the metal center. In contrast, the Zn complex of the saddle-distorted phthalocyanine 1,4,8,11,15,18,22,25-octaphenylphthalocyanine (H2OPPc) exhibits a lower oxidation potential relative to the corresponding porphyrin complex. To construct supramolecular conglomerates composed of both porphyrin and phthalocyanine in a well-defined manner, we have taken advantage of saddle distortion of both components. Herein, we report formation of a discrete supramolecular assembly composed of H4DPP 2+ and [Zn(OPPc)] connected by 4-pyridinecarboxylate (4-PyCOO ) with coordination and hydrogen bonding (Figure 1). The supramolecular conglomerate [(H4DPP){Zn(OPPc)(k-N-4-PyCOO)}2] (1) was synthesized by reaction of [H4DPP](4-PyCOO)2 (2) and Zn(OPPc) (3) in toluene. We crystallized and isolated 1 in pure form by vapor diffusion of hexanes into solution of the mixture in toluene. X-ray crystallography of 1 unambiguously established its structure (Figure 2a).

The synthesis, and spectroscopic and magnetic properties of quadruple-decker phthalocyanines (Pcs) have been reviewed. While the presence of stacked mercury Pc oligomers was proposed as early as 1992, the isolation of a quadruple-decker Pc was first achieved in 2010. Herein, we review how the synthetic strategy for quadruple-decker Pcs has come to be conceived from the recent development of cadmium Pc oligomers, which will be followed by illustration of unique physicochemical properties originating from the structure of the quadruple-decker frameworks. In the spectroscopy section, the electronic structures of the quadruple-decker Pc are discussed based on the theoretical and experimental results. A simple molecular orbital (MO) method predicts that energy gaps among the occupied frontier MOs of the quadruple-decker Pc become smaller than those of double- or triple-decker Pcs, leading to the observation of exceptionally low-lying electronic transitions for the oxidized quadruple-decker Pcs. It has been confirmed that the corresponding lowest π–π* electronic transitions reach the infrared region for the one-electron oxidized quadruple-decker Pcs. In the magnetic property section, a clear evidence of the long-range magnetic dipole–dipole f–f interactions between two f-electronic centers of diterbium quadruple-decker Pc is provided, and its magnetic relaxation phenomena arising mainly from quantum tunneling magnetizations (QTMs) will be discussed by using the alternate current (ac) magnetic susceptibility data, and the numerically calculated Zeeman diagram of the f-electronic centers in the quadruple-decker Pc.

1,2-Naphthalene-ring-expanded tetraazachlorins (TACs), tetraazabacteriochlorins (TABCs), and tetraazaisobacteriochlorins (TAiBCs) have been synthesized. Procedures for the synthesis of the starting materials, that is, derivatives of 1,2-naphthalenedicarboxylic acid, have been reinvestigated and improved. Nine possible derivatives, including four, two, and three structural isomers of TACs, TABCs, and TAiBCs, respectively, were separated by using thin-layer chromatography (TLC) or high-performance liquid chromatography (HPLC), and the structure of each isomer was determined by (1)H NMR spectroscopy combined with the NOE technique. The formation ratio of each isomer was rationalized in terms of the intramolecular steric repulsion effect, which was predicted by geometry optimizations at the DFT level. The derived compounds were characterized by using IR, electronic, and magnetic circular dichroism (MCD) spectroscopy, and by electrochemical methods. Frequency calculations at the DFT level correctly reproduced the experimental IR spectra and, in particular, distinguished between the three isomers of the TAiBCs. In the electronic absorption and MCD spectra of the TAC and TABC species, the Q-band splits into two intense components similarly to the 2,3-naphthalene-fused derivatives described in our preceding paper, although no significant spectral differences were observed from species to species. On the other hand, the spectra of the TAiBCs showed moderate differences depending on the structure of the isomer. The spectroscopic properties as well as the electrochemical behavior of these chlorins resemble those of the corresponding benzene-fused derivatives rather than the 2,3-naphthalene-fused derivatives. Molecular-orbital and configuration-interaction calculations within the framework of the ZINDO/S method were helpful in the discussions of the above observations.

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.

A two dimensional colormap analysis program customized for phthalocyanines and related macrocyclic compounds has been developed in order to effectively visualize the atomic displacements from the mean plane. Eleven known phthalocyanine structures, including super- and subphthalocyanines, have been analysed as examples using the program, and the distribution of the skeletal deformations within the molecules surveyed.

A series of fourteen heteroleptic (phthalocyaninato)(porphyrinato) rare earth(III) double-decker complexes, [MIII(Pc)(TClPP)] [M=Y, La–Lu except Ce and Pm; Pc=phthalocyaninate; TClPP=meso-tetrakis(4-chlorophenyl)porphyrinate] has been prepared by base-promoted cyclization of phthalonitrile on the corresponding [MIII(TClPP)(acac)] (acac=acetylacetonate) as the template in refluxing n-octanol. The yields are highest for the mid-lanthanides, which have the optimum size to balance the stabilization due to π-π interactions and the destabilization due to axial compression of the two π systems. The whole series of double-decker complexes has been characterized by elemental analysis and a wide range of spectroscopic methods. The molecular structure of [GdIII(Pc)(TClPP)] has also been determined. All the electronic absorption bands are dependent on the size of the metal center, suggesting that all the transitions involve molecular orbitals with contributions from both Pc and TClPP ligands. This has been supported by a systematic investigation of the electrochemical properties of the whole series of complexes. All these studies indicate that there are substantial π-π interactions and the hole is mainly localized at the Pc ligand.

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.

Three isomeric 2[Pd(II)-Ni(II)] metal complexes, derived from indoleninyl meso-substituted dibenzotetraaza[14]annulene, were synthesized. The resulting dimers feature Ni···Ni or, alternatively, Ni···π interactions in staggered or slipped cofacial structures. A remarkable insertion of palladium into two different C-H bonds yielded a 4[Pd(II)-Ni(II)] rectangular complex with dimensions of 8.73 × 10.38 Å.

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.

Magnetic relaxations arising from spin-phonon interactions for a magnetically diluted double-decker terbium phthalocyanine single molecule magnet, dil1, in the nonthermally activated temperature range have been investigated. While the relaxation time, τ, is independent of the external static magnetic field, H(dc), in the high temperature range, where linear relationships between -ln τ and T(-1) are observed in the Arrhenius plot, magnetic field dependences for τ are observed in the lower temperature range. The τ(-1) vs H(dc) plot at 12 K fits the quadric curve when H(dc) < 12 kOe, while linear relationships are observed in the τ(-1) vs T plots in the temperature range of 12-20 K. These results indicate that the direct process is the dominant magnetic relaxation pathway in the nonthermally activated temperature range, while the contribution from the Raman process, if any, is not observable. We emphasize in this paper that the contribution from the thermal relaxation processes and the quantum tunneling of magnetizations (QTMs) to the experimentally observed magnetic relaxations must be evaluated carefully in order to avoid confusion between the thermal and quantum-mechanical relaxation pathways.

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.

Molecular self-assembly of porphyrin derivatives formed with intermolecular hydrogen bonding on the surface of Au(111) electrode in acidic solution can be controlled by varying the number of peripheral carboxy groups and the applied electrochemical potential.

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.

Spectroscopic investigations have been performed for the oxidized forms of two quadruple-decker phthalocyanine complexes in order to clarify the electronic structures of multiply stacked π-systems. Up to three-electron-oxidized species were isolated by using phenoxathiin hexachloroantimonate as the oxidant. As the oxidations proceed, the Q-bands in the visible region shift bathochromically along with the clear isosbestic points. The one- and three-electron-oxidized species exhibited typical π-radical signals in the ESR spectra, while the neutral and two-electron oxidized species gave no indication of the presence of π-radicals. The electronic transitions observed for the oxidized species reach even into the so-called fingerprint region in IR spectroscopy (~1000 cm(-1)). With the aid of theoretical calculations, these bands can be assigned to the π-π* transitions. Our results provide new insights into π-electronic systems having exceptionally small MO energy gaps.

A series of dialkoxy-substituted copper phthalocyanine (CuPc) precursors (4a-4d) have been prepared by treating phthalonitrile with the corresponding lithium alkoxide under mild conditions. The precursors exhibited high solubilities in common organic solvents, including acetone, toluene, tetrahydrofuran (THF), CH(2)Cl(2), and CHCl(3). Elongation of the alkoxy chains improved the solubilities of the precursors effectively, and accordingly, the butoxy-substituted derivative (4d) showed the highest solubility among 4a-4d. X-ray crystallography clarified that the conjugated skeletons of 4a-4d are all isostructural, and have two alkoxy groups in a syn-conformation fashion, leading to highly bent structures. Thermal conversions of the precursors examined by thermogravimetry (TG) and differential thermal analysis (DTA) demonstrate that 4a was converted into CuPc via two distinct exothermic processes in the 200-250 °C temperature range, while 4d exhibits only one exothermic signal in the DTA. In the field emission scanning electron microscopy (FESEM) images of 4a, the presence of two types of distinct crystal morphology (prismatic and plate-like crystals) can be recognized, implying that the two observed exothermic processes in the DTA can be attributed to the different crystal morphologies of the samples rather than the step-by-step elimination of the alkoxy groups. The thermal formation of CuPc from the precursors has been unambiguously confirmed by X-ray powder diffraction, UV-vis spectroscopy, and elemental analysis. The precursors were converted into CuPc at lower temperature with increasing chain length, presumably because of the increased void volume in the crystals. Thermal conversion performed in the solution phase results in a bright blue-colored solution with prominent absorption bands in the 650-700 nm region, strongly supporting the formation of CuPc.

Soluble copper phthalocyanine (CuPc) and naphthalocyanine (CuNc) precursors which can be converted thermally and photochemically into insoluble CuPc and CuNc, respectively, have been synthesized by a one-step reaction using commercially available chemicals.

Molecular adlayers of doubly C(60)-conjugated phthalocyanine derivatives ((C(60))(2)NiPc) were examined on bare and zinc(II) octaethylporphyrin (ZnOEP)- and coronene-modified Au(111) surfaces. Electrochemical scanning tunneling microscopy (EC-STM) has revealed the structure of the (C(60))(2)NiPc adlayer at single molecular level. The (C(60))(2)NiPc adlayer is strongly influenced by the underlying organic layers, i.e., a disordered, a packed structure of (C(60))(2)NiPc was found on a clean Au(111) surface because of the strong interaction between (C(60))(2)NiPc molecule and Au(111) substrate, whereas a single (C(60))(2)NiPc molecule was clearly distinguished both on ZnOEP and coronene adlayers at a low coverage of (C(60))(2)NiPc molecules. The obtained results in the present study suggest that the underlying organic adlayers play an important role in the formation process of the (C(60))(2)NiPc molecule adlayer.

We introduce some representative studies from our laboratory, mostly from the 21st Century. We are interested in the synthesis, optical spectroscopy, such as magnetic circular dichroism (MCD), circ...