Synthesis, Characterization, and Electronic Structures of Porphyrins Fused with Polycyclic Aromatic Ring Systems.

A series of porphyrins fused with acenaphthylene, phenanthroline, and benzofluoranthene polycyclic aromatic rings were prepared by means of a 3+1 porphyrin synthesis approach and subsequent retro-Diels-Alder reaction of bicyclo[2.2.2]octadiene-fused precursors. Analysis of the magnetic circular dichroism spectra and the results of time-dependent DFT calculations are used to identify the reasons for the trends observed in the wavelengths and relative intensities of the Q bands of the products. Michl's perimeter model is used as a conceptual framework to explain the changes in the relative energies of the frontier π-molecular orbitals.

Retro-Diels-Alder approach to the synthesis of π-expanded azuliporphyrins and their porphyrinoid aromaticity.

Bicyclo[2.2.2]octadiene (BCOD) fused azuliporphyrins were synthesized by 3+1 porphyrin synthesis of azulitripyrranes with diformylpyrroles. Subsequent retro-Diels-Alder reaction of the BCOD-fused azuliporphyrins afforded azulibenzo-, azulidibenzo-, and azulitribenzoporphyrins 1-5. NMR and UV/Vis spectra, as well as nucleus-independent chemical shift (NICS) calculations revealed that 1-5 and their diprotonated dications exhibit relatively low porphyrinoid aromaticity, which was dependent on the position and number of fused benzene rings present.

Highly pure synthesis, spectral assignments, and two-photon properties of cruciform porphyrin pentamers fused with benzene units.

Tetrameric porphyrin formation of 2-hydroxymethylpyrrole fused with porphyrins through a bicyclo[2.2.2]octadiene unit gave bicyclo[2.2.2]octadiene-fused porphyrin pentamers. Thermal conversion of the pentamers gave fully pi-conjugated cruciform porphyrin pentamers fused with benzene units in quantitative yields. UV/Vis spectra of fully pi-conjugated porphyrin pentamers showed one very strong Q absorption and were quite different from those of usual porphyrins. From TD-DFT calculations, the HOMO level is 0.49 eV higher than the HOMO-1 level. The LUMO and LUMO+1 levels are very close and are lower by more than 0.27 eV than those of other unoccupied MOs. The strong Q absorption was interpreted as two mutually orthogonal single-electron transitions (683 nm: 86 %, HOMO-->LUMO; 680 nm: 86 %, HOMO-->LUMO+1). The two-photon absorption (TPA) cross section value (sigma((2))) of the benzene-fused porphyrin pentamer was estimated to be 3900 GM at 1500 nm, which is strongly correlated with a cruciform molecular structure with multidirectional pi-conjugation pathways.

Synthesis, structures, and optical and electrochemical properties of benzoporphycenes.

The first facile syntheses of free-base di- and tetrabenzoporphycenes and their metal complexes are reported, based on retro-Diels-Alder reactions of the corresponding bicyclo[2.2.2]octadiene-fused porphycenes, prepared by McMurray coupling of alpha,alpha'-diformyldipyrrole. The photophysical and electrochemical properties are analyzed based on UV/Vis absorption, magnetic circular dichroism (MCD), and fluorescence emission, lifetime and quantum yield measurements, cyclic and differential pulse voltammetry (CV and DPV) and time-dependent DFT calculations based on B3LYP geometry optimizations. Benzoporphycenes are found to be prime candidates for future use in photodynamic therapy.

Synthesis of tetraglucosyl- and tetrapolyamine-tetrabenzoporphyrin conjugates for an application in PDT.

This paper reports the synthesis and characterization of a new class of tetrabenzoporphyrins bearing glucosyl or polyamine units on meso positions to improve the targeting of cancer cells. Photocytotoxic activity of these photosensitizers was tested on cell lines HaCaT and MCF-7 and compared to Photofrin II.

Synthesis and characterization of tetraanthroporphyrins.

Linearly pi-expanded novel tetraanthroporphyrins with and without aromatic rings at the meso-positions were prepared quantitatively for the first time from the corresponding precursors by a retro-Diels-Alder reaction.

Organic semiconductors based on small molecules with thermally or photochemically removable groups.

Solution processable organic semiconducting small molecules are desirable for the manufacture of low-cost, large-area electronic products on flexible substrates. This article provides an overview of recent progress in OFETs based on solution processable small molecules that can be converted to insoluble organic semiconducting materials on films by thermal or photochemical removal of leaving groups after fabrication of the film.

Soluble precursors of 2,3-naphthalocyanine and phthalocyanine for use in thin film transistors.

Soluble precursors of 2,3-naphthalocyanine (Nc) and phthalocyanine (Pc) were prepared and were converted into insoluble semiconducting thin films of Pc and Nc by heating after fabrication via spin-coating.

Novel one-pot synthesis of 5-alkenyl-15-alkynylporphyrins and their derivatisation to a butadiyne-linked benzoporphyrin dimer.

5-Alkenyl-15-alkynylporphyrins have been obtained unexpectedly by [2 + 2] acid-catalyzed condensation of dipyrrylmethane and TMS propynal in addition to 5,15-dialkynylporphyrin, and the unsymmetrical porphyrin can be converted to a butadiyne-linked dimer by selective desilylation of the alkynyl TMS.

Enlarged pi-electronic network of a meso-meso, beta-beta, beta-beta triply linked dibenzoporphyrin dimer that exhibits a large two-photon absorption cross section.

Enlargement of the pi-electronic network of meso-meso, beta-beta, beta-beta triply linked diporphyrin has been exploited by preparing a corresponding dibenzo-fused porphyrin dimer that exhibits a perturbed absorption spectrum and a large two-photon absorption cross section.

Novel preparation of beta,beta'-connected porphyrin dimers.

Porphyrin dimers were prepared from beta,beta'-dipyrrole derivatives via the double pyrrolylmethylation followed by double [2 + 2] MacDonald porphyrin synthesis.

First synthesis of a series of core-modified tetrabenzoporphyrins.

Successful synthesis of a series of highly conjugated porphyrin analogues, including thia-, dithia- and oxathia-tetrabenzoporphyrins, and their optical properties are reported.

Tuning the spectroscopic, electrochemical, and photovoltaic properties of triaryl amine based sensitizers through ring-fused thiophene bridges.

The ring-fused thiophene derivatives benzo[c]thiophene and its precursor bicyclo[2.2.2]octadiene (BCOD) have been introduced as π-conjugated spacers for organic push-pull sensitizers with dihexyloxy-substituted triphenylamine as donor and cyanoacrylic acid as acceptor (OL1-OL6). The effects of the fused ring on the spectroscopic and electrochemical properties of these sensitizers and their photovoltaic performance in dye-sensitized solar cells have been evaluated. Introduction of a binary benzo[c]thiophene and ethylenedioxy thiophene as π bridge caused a significant red shift of the characteristic intramolecular charge-transfer band to 642 nm. It is found that the sensitizer OL3, which contains one benzo[c]thiophene unit as π linker, gives the highest overall conversion efficiency of 5.03% among all these dyes.

FET performance and substitution effect on 2,6-dithienylanthracene devices prepared by photoirradiation of their diketone precursors.

Hole mobility was evaluated by top-contact bottom gate field effect transistor and time resolved microwave conductivity measurements in 2,6-dithienylanthracene and hexyl-substituted 2,6-dithienylanthracene films prepared by spin-coating of their α-diketone precursors followed by photoirradiation, revealing enough high potentials for semiconducting films with charge carrier mobilities of 0.8-0.9 cm(2) V(-1) s(-1) in the photo-irradiated films.

Synthesis, crystal structure, and photodynamics of π-expanded porphyrin-fullerene dyads synthesized by Diels-Alder reaction.

Free base and zinc porphyrins are linked with fullerene (C(60)) through ß,ß'-pyrrolic positions rather than meso-positions by Diels-Alder reaction of monoanthraporphyrins (H(2)P-mA and ZnP-mA) and C(60) to afford a π-expanded free base porphyrin-fullerene dyad (H(2)P-C(60)) and its zinc porphyrin-fullerene dyad (ZnP-C(60)) in 86 and 51% yield, respectively. The X-ray crystallographic analysis of ZnP-C(60) showed two comma-shaped swirls-like structure in a unit cell. The intramolecular center-to-center and edge-to-edge distances between the porphyrin and fullerene moieties were 11.5 and 2.5 Å, respectively. The porphyrins and fullerenes were packed in layer-by-layer structure and the porphyrins lied down in parallel. The intermolecular center-to-center distances between the neighboring fullerenes were 10.252, 10.028, and 10.129 Å, which were less than typical van der Waals distance and the π-π interaction spread two-dimensionally. The energy of the charge-separated (CS) state of ZnP-C(60) (1.11 eV) determined by differential-pulse voltammetry measurements in benzonitrile is significantly lower than those of zinc porphyrin-C(60) dyads linked at meso positions because of the low oxidation potential of the π-expanded ZnP moiety. The CS energy of ZnP-C(60) in a nonpolar solvent such as toluene (1.40 V) is lower than the triplet excited state of C(60) ((3)C(60)*), enabling us to attain a long lived triplet CS state (8.1 µs) in toluene, detected by nanosecond laser flash photolysis experiments. The distance between unpaired electrons in the triplet CS state was determined by the EPR spectrum to be 9.1 Å, which agreed with the distance between a zinc atom of the porphyrin and a carbon edge of C(60) in the crystal structure of ZnP-C(60). The rate constants of photoinduced electron transfer and back electron transfer of H(2)P-C(60) and ZnP-C(60), which were determined by femtosecond and nanosecond laser flash photolysis measurements, were analyzed in light of the Marcus theory of electron transfer.

First synthesis of porphyrin-fused 1,10-phenanthroline-ruthenium(II) complexes.

Synthesis of [Ru(phenP)(3)](PF(6))(2), where phenP = phenanthrolinoporphyrin, has been achieved by the reaction of phenanthrolinoporphyrins with RuCl(3) for the first time. The phenP reacted with Ru(II) to form RuL(2)(phenP)(2+) complexes (L = 2,2'-bipyridine or 1,10-phenanthroline), which were converted into the dyads Ru-phenP(Zn) on treatment with zinc acetate.

Electron transfer reaction of porphyrin and porphycene complexes of Cu(II) and Zn(II) in acetonitrile.

The outer-sphere one-electron oxidation reaction of the Cu(II) and Zn(II) complexes of nonplanar 2,3,7,8,12,13,17,18-octaethyl-5,10,15,20-tetraphenylporphyrin and planar porphycenes as well as those of 2,3,7,8,12,13,17,18-octaethylporphyrin and 5,10,15,20-tetraphenylporphyrin by Cu(2+) giving corresponding pi-cation radicals was investigated spectrophotometrically in acetonitrile. The electron self-exchange rate constants between the parent porphyrin and porphycene complexes and their pi-cation radicals were determined using the Marcus cross relation for the electron transfer reaction. The obtained rate constants are in the order of 10(9) to 10(11) M(-1) s(-1) for the planar porphyrin and porphycene complexes and 10(4) to 10(6) M(-1) s(-1) for the nonplanar OETPP complexes at T = 25.0 degrees C. The relatively slow self-exchange reaction of the distorted porphyrin complexes, as compared with those for the planar porphyrin and porphycene complexes, was ascribed to the significant deformation of the complex associated with the oxidation reaction from the parent complex to the corresponding pi-cation radical.

Cylindradines A and B: novel bromopyrrole alkaloids from the marine sponge Axinella cylindratus.

The novel alkaloids cylindradines A and B were isolated from Axinella cylindratus, and their structures were elucidated by spectroscopic analyses. Stereochemistries of these compounds were determined by X-ray analysis. Cylindradines showed moderate inhibitory activity against the murine leukemia cell line P388.