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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.

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.

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.

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 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.

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...

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).

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.

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.

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.

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.

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.

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.

A tribenzotetraazachlorin (TBTAC)-C(60) conjugate having three 15-crown-5 units as substituents, , has been synthesized, and the electronic and supramolecular structure modulations in the presence of Na(+) or K(+) have been elucidated by means of massmetric and spectroscopic techniques.

Novel tetraazachlorin (TAC)-fullerene (C60) conjugates (TAC-C60) and their analogues (TAiBC-C60 and TABC-C60 where TAiBC = tetraazaisobacteriochlorin and TABC = tetraazabacteriochlorin) have been synthesized by condensing 1,2-dicyanofullerene (1) and phthalonitrile derivatives (2) in the presence of nickel chloride in quinoline, and fully characterized using mass spectrometry and 1H and 13C NMR. By arranging the TAC and C60 units at the minimum distance, and taking also into account the molecular symmetry, the resultant conjugates show on-off electronic communication behavior, depending on the push-pull properties of the peripheral substituents in the TAC moiety. Consequently, the UV-vis absorption spectrum of the electron-releasing butyloxy-substituted TAC-C60 (3a) contains an unusual group of three absorption bands in the Q-band region (500-900 nm) as a result of a strong electronic communication between the two moieties. On the other hand, the absorption spectrum of the electron-withdrawing butylsulfonyl-substituted TAC-C60 (3b) comprises a typically normal TAC spectrum with markedly split two-peak Q-bands. A similar phenomenon is observed between alkoxy-substituted TAiBC-C60 (4a) and butylsulfonyl-substituted TAiBC-C60 (4b). This study reveals that the electron-donating or -withdrawing nature of the peripheral substituents on an azachlorin moiety has an important effect on the electronic structures of our novel azachlorin-C60 conjugates, although the linking carbon atoms are aliphatic sp3 carbon atoms which generally do not contribute to aromaticity. The electronic structures of the conjugates have been investigated in detail using spectroscopic and electrochemical techniques with the aid of DFT 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.

Tetraazaporphyrins (TAPs), phthalocyanines (Pcs), naphthalocyanines (Ncs), and anthracocyanines (Acs) with four tert-butyl groups attached at similar positions have been synthesized, and their electronic absorption, magnetic circular dichroism (MCD), IR, and voltammetric properties were studied and interpreted with the help of quantum-mechanical calculations. Through the preparation of a series of compounds with the same number of the same substituent, the effects of the increase in the size of the ring system were clearly derived. The main results may be summarized as follows. 1) The Q band shifts to longer wavelength and its intensity increases, but with decreasing degree of change with increasing molecular size. If the size of the effect of benzene directly fused to the TAP skeleton is set at unity, the effects of the second and third benzene units are roughly 0.8 and 0.5, respectively. 2) The splitting of the Q bands in metal-free compounds decreases with increasing molecular size, so that the Q bands of H2Nc and H2Ac appear as single bands. 3) The magnitude of the orbital angular momentum of the excited state of the ligand decreases with increasing molecular size. 4) Interestingly, the ring current, as judged from the positions of pyrrole proton signals in the 1H NMR spectrum, appears to decrease with increasing molecular size. 5) The first reduction potential becomes less negative, but only slightly, whereas the first oxidation potential shows a marked shift to less positive values with increasing molecular size, indicating that the HOMO destabilizes significantly as the molecule becomes larger. 6) In 5), the extent of the HOMO destabilization with molecular size differs depending on the central metal, so metals producing smaller destabilization effects can allow larger macrocycles. Of the metals studied, the most effective is cobalt, and the practical size limit is represented by the Acs. 7) The IR spectra become simpler the larger the molecule, and the main bands were assigned by DFT calculations. 8) The trend in experimentally determined redox potentials and electronic absorption and MCD spectra were reasonably reproduced by MO calculations using the ZINDO/S Hamiltonian. 9) EPR data for several metallocomplexes are also reported.

A method which preferentially produces adjacently di-aromatic ring-substituted tetraazaporphyrins (TAPs) has been developed, and their electrochemical and spectroscopic properties have been studied and compared with those of the corresponding series of mono-aromatic ring-fused TAPs. Mono-aromatic ring-fused TAPs show a split Q-band, and the splitting energy increases with increasing size of the aromatic ring. In addition, for the split Q-bands, the relative intensity of the band at longer wavelength decreases with increasing molecular size of the fused aromatics, compared with the shorter wavelength band. In the di-aromatic ring-fused TAPs, this kind of splitting is not seen, and only a shift of the band is observed. The intensity and band position of the split or unsplit Q-bands are quantitatively evaluated by simultaneous band deconvolution analysis, using both electronic absorption and magnetic circular dichroism spectra. The preparation of these TAP compounds has made it possible to adjust the Q-band position in a stepwise manner between ca. 600 and 750 nm. The first reduction and oxidation potentials of the TAP ring shift negatively with increasing number and size of the fused aromatics. The extent of the shift is found to be very small for the LUMOs but significant for the HOMOs. These spectroscopic and electrochemical properties are almost perfectly reproduced by molecular orbital calculations within the framework of the Pariser-Parr-Pople approximation. In particular, a small variation of the LUMO level and large destabilization of the HOMO level on ring expansion are rationalized from the extent of stretch of molecular orbitals: i.e., since the LUMOs are localized in the central TAP moiety irrespective of the molecular size, while the HOMOs have appreciable coefficients even over the fused aromatics, the HOMO level destabilizes while the LUMO level remains constant with increasing molecular size. In one CoTAP derivative, Co(III/II) and the first ligand oxidation couples occur experimentally at the same potential.

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.

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.

Vibrational circular dichroism (VCD) spectra of (R)-(−)- and (S)-(+)-camphor-substituted tetrapyrazinoporphyrazines, which show a mirror-image relationship with respect to the line of intensity = 0...

Metal complexes of a highly deformed 1,4,8,11,15,18,22,25-octaphenylphthalocyanine have been synthesized, and found to show various colors ranging from bright green, ocher, and red depending on the central metal employed.

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.

Homo and heteronuclear quadruple-decker phthalocyanine tetramers containing Y(3+) and/or magnetically anisotropic lanthanide ions such as Tb(3+), Dy(3+), and Er(3+) have been synthesized, and their magnetic properties have been elucidated, giving clear evidence of the long-range interactions between two f-electronic centers.

The C2v isomer of Co(1,2-Nc-C2v) (1,2-Nc = 1,2-naphthalocyaninato) has been isolated by fractional crystallization of the crude mixture of four isomers (C4h, Cs, C2v, D2h), and its crystal structure, electronic absorption, and magnetic circular dichromism have been discussed.

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.

A subphthalocyanine (SubPc) dimer linked by racemic 1,1'-binaphth-2,2'-dioxy (BINOL), 1, has been synthesized and characterized by 1- and 2-D 1H NMR, high resolution mass spectrometry (FAB), X-ray crystallography and electronic absorption spectroscopy. Additionally, the dimer derived from optically-active (R)-(+)-BINOL, 2, has been made and studied using CD and MCD spectroscopies.

A highly deformed [1,4,8,11,15,18,22,25-octaphenylphthalo-cyaninato(2-)]iron(II) has been synthesized, and found to show absorption bands which may be assigned to metal-to-ligand charge transfer (MLCT) transitions in the near-IR region beyond the Q-band in pyridine, due to lowering of molecular symmetry to D2d from D4h symmetry of normal metallophthalocyanines.