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An insoluble thin film of a coronene diimide (CDI) derivative was fabricated from a soluble precursor of perylene diimide (PDI) by photoirradiation. We prepared a 1,7-diarylated PDI (TP-PDI) that can be converted into a coronene diimide (TP-CDI) derivative via a Scholl-type photocyclization reaction. This reaction was accompanied by structural changes from a twisted structure to a π-extended planar molecule. It was found that this photoconversion reaction occurs for both solution-based and thin-film-based reactants investigated by the changes of UV-vis absorption spectra and 1 H NMR spectra. The photocyclization reactions were found to proceed smoothly in polar solvents. In the thin-film state, the solvent vapor annealing method is a key process for achieving photoconversion reaction. Additionally, the fabrication of multi-layered thin films was achieved without undesirable dissolution of the underlying layers because of different solubilities of TP-PDI and TP-CDI.

The structure and electronic features of neutral and positively charged pyrene and perylene derivatives were explored. The radical cation of 1,3,6,8-tetraarylpyrene 1 was examined by ESR, UV-vis-NIR spectroscopy and theoretical calculations. The addition of 2 equiv of oxidant to 1 resulted in the formation of dication 12+. The single-crystal X-ray structure of 12+ proved that the aromatic part relocates from biphenyl unit to naphthyl unit upon 2e- oxidation of 1. We have also investigated the oxidation processes of 3,9-diarylperylene 2 and 3,10-diarylperylene 3. The radical cations of 2・+ and 3・+ showed ESR signals and the spin densities were proven to delocalize at 3,4,9,10-positions. In the case of doubly charged 3,9-diarylperylene, we could find the anthracene structure in the core, while the phenanthrene skeleton appeared in two-electron oxidized 3,10-diarylperylene. Finally we validated this phenomenon to apply for the higher analogue terrylene, discovering its large aromaticity relocation upon the 2e- oxidation.

This Letter details a simple and effective method to synthesize a porphyrin(2.1.2.1)-based nanobelt NBNi3 via condensation reactions of 1,2,4,5-tetra(pyrrol-2-yl)benzene and benzaldehydes. NBNi3 consists of three arch-shaped porphyrins(2.1.2.1) and benzene linkages with a C3h-symmteric structure. The concave-shaped cavity of NBNi3 behaves as a C60 receptor by capturing two C60 cooperatively. Additionally, NBNi3 exhibits reversible oxidation and reduction peaks with five electrons in each peak, indicating that the shape of the nanobelt can stabilize multicationic and anionic states.

A sandwich complex of iridium(III) benzotriphyrin (2) has been synthesized from free-base benzotriphyrin (1) and [IrCl(cod)]2 (COD = 1,5-cyclooctadiene). The COD ring was transformed from 1,5-COD to an η1,η3-C8H12 unit as a π-allyl ligand associated with the valence change of iridium from IrI to IrIII, as revealed by X-ray diffraction analysis. The Soret-like band of 2 was blue-shifted and broadened compared with that of 1, indicating strong electronic interactions between triphyrin and the iridium ion. Compound 2 also showed very broad absorption in the range of 500–800 nm, which can be assigned to a mixture of Q and metal-to-ligand charge-transfer bands.

Porphycene dimers connected by [Formula: see text]-phenylene (DPc– m P) and 2,5-thienylene (DPc–T) linkages have been synthesized from 2,7,12,17-tetrahexyl-3-iodoporphycene by palladium-catalyzed cross-couplings. The crystal structures of porphycene dimers revealed that meta-phenylene linkage provides a highly twisted structure with the dihedral angel of 103° between two porphycene units, while thienylene linkage provides a nearly planar structure of two porphycene units. These porphycene dimers showed strong absorption thorough the visible to NIR regions and HOMO and LUMO energy levels of them are suitable as [Formula: see text]-type materials of organic solar cells (OSCs) in combination with P3HT as a [Formula: see text]-type material. The hole and electron mobilities of the blended films of the porphycene dimers and P3HT obtained by space-charge-limited-current (SCLC) method were 3.7 × 10[Formula: see text] and 0.26 × 10[Formula: see text] cm2.V[Formula: see text].s[Formula: see text] for DPc– m P :P3HT, and 3.2 × 10[Formula: see text] and 0.027 × 10[Formula: see text] cm2.V[Formula: see text].s[Formula: see text] for DPc–T :P3HT. Atomic force microscopy (AFM) and thin-film X-ray diffraction analysis (XRD) measurements indicated that the blended films of the porphycene dimers and P3HT formed amorphous films with smooth and low-roughness surfaces, whereas the blended film of porphycene monomer and P3HT created the highly crystalline film with huge domain structures. The OSCs composed of porphycene dimers and P3HT showed power conversion efficiencies of 0.08% was twice as high as that of monomer-based OSC.

A bisanthra-thianthrene has been synthesized and the oxidation property was studied to show that the bis(tetracene radical cation) linked by a dithiin ring is more stable than the π-expanded dithianonacene dication.

The synthesis and photophysical properties of new dibenzo[b,i]fluorone dye frameworks (BX and FBX) are described. Both BX and FBX display near-infrared sharp absorption and emission upon the addition of base due to the achievement of efficient π-conjugation based on the small bond alternation strategy.

Organic π-conjugated small molecules have attracted much attention for developing high performance organic photovoltaics (OPVs) due to their well-defined molecular structure, easily controlled energy levels and absorption, and more accurate simulation-experiment match. A novel small molecule combing a N-heteroacene (acceptor moiety) and benzo[1,2-b:4,5-b′]dithiophene (donor unit) together through a π-conjugated bridge (3,3″-dioctyl-2,2′:5′,2″-terthiophene), has been synthesized and characterized. The blended films of this small molecule with different acceptors have a wide absorption in visible region, which makes it possible for application in OPVs. The as-fabricated devices with PEDOT:PSS as an anode buffer layer show the power conversion efficiency at around 1%. By replacing PEDOT:PSS with MoO3, the power conversion efficiency is almost doubled up to 1.97%. AFM images and XRD patterns are employed to investigate the morphologies of the active layer. Consistent with the J–V curves and EQE spectra, the higher power conversion efficiency probably comes from the good alignment of the HOMO energy level of the small molecule with the work function of anode buffer layer and reduced chemical interactions between active layer and anode buffer layer.

Indolizino[5,6-b]quinoxaline derivatives (1 a and 1 b) with a push-pull structure were prepared to show intramolecular charge-transfer properties. Compounds 1 a and 1 b are strongly fluorescent in aprotic solvents while symmetrical derivatives (2?a and 2?b) were non-fluorescent. The π-expanded α-α linked dimer (10) of indolizino[5,6-b]quinoxaline 1 b was serendipitously obtained to show NIR absorption over 800 nm and the fluorescence edge reached to 1400 nm.

The butadiyne- and acetylene-linked 3,3′-porphycene dimers 1 and 2 were synthesized from the common intermediate, 3-ethynyl-2,7,12,17-tetrahexylporphycene 4. The butadiyne-linked dimer 1 was prepared from 4 by copper mediated Glaser-type homo-coupling. The acetylene-linked dimer 2 was synthesized by Sonogashira coupling of 4 and 2,7,12,17-tetrahexyl-3-iodoporphycene 5. These porphycene dimers were characterized by 1 H and 13 C NMR spectroscopies, mass spectroscopy, X-ray diffraction analysis, UV-vis absorption and fluorescence spectra, cyclic voltammetry and differential pulse voltammetry. Crystal structure of 1showed a coplanar structure of two porphycene units. The absorption spectra in CH 2 Cl 2 indicated the small interaction between the porphycene units through the linkage at 3,3′-positions. The electrochemical measurement showed two one-electron oxidation potentials and four one-electron reduction potentials indicating the electric interaction between the porphycene units.

Bicyclo[2.2.2]octadiene-fused (BCOD-fused) bis(benzoborondipyrromethene)s (bisbenzoBODIPYs) bearing electron-withdrawing groups such as fluorine and cyano groups were prepared either by incorporating tetrafluoroisoindole moieties into BODIPY chromophores or by introducing cyano or ethoxycarbonyl groups at the 3,5-positions. The BCOD-fused bisbenzoBODIPYs were quantitatively converted to the corresponding benzene-fused bisbenzoBODIPYs by a retro-Diels-Alder reaction. The π-fused bisbenzoBODIPYs were found to have intense absorption in the near-infrared region and not to have any strong absorption bands in the visible region. Moreover, the bisbenzoBODIPYs were stable under atmospheric conditions.

We have investigated the photophysical properties of alkyl-substituted triphyrin(2.1.1) (ATp) and benzotriphyrin(2.1.1) (BTp) by steady-state and time-resolved fluorescence spectroscopy. We focused on the effect of NH proton tautomerization, planarity of the macrocycles, and substituents on these properties. The fluorescence quantum yields (Φy) of ATp did not depend on solvent viscosity, whereas those of BTp increased with solvent viscosity, reaching a maximum value of 0.17 in paraffin. Interestingly, analyzing Φy showed that the non-radiative rate constant of BTp decreased sharply as the solvent viscosity increased. These results suggest that the substituted phenyl groups play a crucial role in suppressing molecular distortion, thus leading to decreased non-radiative relaxation in triphyrin(2.1.1). The hydrogen bond formed in the inner cavity potentially contributes to the suppression of the structural distortion, whereas the pyrrole rings in the macrocycle are close, as in porphycene.

Organogels: Dimerization of perylene bisimide dyes through an oligomethylene linker enabled the facile control over columnar and lamellar self-organized architectures by an odd/even effect with respect to the number of methylene groups. The difference in the self-organized architectures was shown to have an impact on their material morphologies, as well as charge-carrier mobilities (see scheme).

We prepared perylene dications 1(2+) and 2(2+) by using "capped" perylene derivatives, and for the first time, successfully obtained single crystals of a perylene dication 1(2+) that enabled us to perform its structural analysis. We realized that the substituted aryl groups on perylene control the positions of positive charges, thus the remaining electronic system satisfies Clar's sextet rule toward the highest number of localized sextets. Experimental and theoretical evidence proved that Clar's aromatic π-sextet rule could be applied even for the dicationic perylenes in a very simple way.

Facile synthesis of dibenzoporphyrins(2.1.2.1) has been successfully reported by the simple condensation reaction of o-dipyrrolylbenzene with various aldehydes in the presence of a Lewis acid. This reaction enables the preparation of various dibenzoporphyrin(2.1.2.1) derivatives with p-substituted phenyl groups, five-membered heterocycles, and ethynyl groups at the meso-positions. Dibenzoporphyrins(2.1.2.1) consist of two dipyrrin units that are connected by o-phenylene bridges, which adopt highly bent saddle-shaped structures; this was confirmed by X-ray diffraction analysis. We found that dibenzoporphyrin(2.1.2.1) can be described as a 20π antiaromatic conjugated system, but practically, it is not an antiaromatic macrocycle, which we revealed by (1) H NMR spectroscopy. The redox potentials had good correlations with Hammett substituent constant (σp ) of the substituents at the meso-positions. The free-base dibenzoporphyrin(2.1.2.1) was able to form the metal complexes with nickel(II), copper(II), palladium(II), platinum(II), and tin(IV) ions. These results suggested that dibenzoporphyrin(2.1.2.1) derivatives can be utilized as novel macrocyclic dianionic tetradentate ligands for various metal ions to give complexes with varying optical and electrochemical properties.

5,14-α-Diketopentacene, a structural isomer of 6,13-α-diketopentacene, was prepared from pentacene in three steps. In addition to the typical n-π* absorption of the diketone moiety at around 468 nm and the anthracene-like absorption at 333, 349, and 367 nm, a broad absorption was observed at around 386 nm, which could be assigned to an intramolecular charge-transfer absorption from anthracene to the diketone moiety. 5,14-α-Diketopentacene could be converted into pentacene quantitatively by photoirradiation at 405 and 468 nm in toluene with quantum yields of 2.3 and 2.4 %, respectively, and these values are higher than the quantum yield of 1.4 % obtained for 6,13-α-diketopentacene irradiated at 468 nm. The quantum yields in acetonitrile were lowered to 0.33 and 0.28 % with irradiation at 405 and 468 nm. The crystal structure of 5,14-α-diketopentacene showed a CH-π interaction and π-π stacking between neighbouring anthracene and benzene moieties. The lower solubility of 5,14-α-diketopentacene compared with the 6,13-isomer could be explained by this crystal structure.

A series of benzoporphycenes and naphthoporphycenes and their zinc complexes were prepared from bicyclo[2.2.2]octadiene fused porphycenes by a retro-Diels-Alder reaction and their photophysical properties were studied. Free-base tetranaphthoporphycene was not soluble in common organic solvents, but zinc tetranaphthoporphycene was slightly soluble in pyridine and showed B- and Q-bands at 507 and 690 nm, respectively. Dinaphthoporphycene showed broad B- and Q-bands due to its lower symmetry. Tetrabenzo-, dibenzo-, and dinaphthoporphycenes showed fluorescence at 673, 654, and 670 nm with quantum yields of 0.32, 0.42, and 0.31, respectively, although their precursors were non-fluorescent. Zinc complexes of tetrabenzo-, dibenzo-, tetranaphtho-, dinaphthoporphycenes and their bicyclo[2.2.2]octadiene-fused precursors revealed moderate fluorescence with quantum yields of 0.15–0.37. The crystal structures of tetrabenzo- and dibenzoporphycenes showed herringbone structures, while the zinc tetrabenzoporphycene showed a hexagonal box-structure with six pyridine ligands inside.

Sterically congested tetraarylpyrenes exhibited emission in both solution and the solid state. The monocationic species of pyrene 1 could be isolated because of the reasonably protected system. The aromaticity of 1 relocates from the biphenyl part to the naphthalene unit upon two-electron oxidation.

A synthesized vitamin K model compound, NQ-6 (2-hexyloxy-1,4-naphthoquinone) showed weak fluorescence around 440 nm in ethanol. Addition of antioxidants such as vitamin E to a NQ-6 solution suppressed the NQ-6 emission quantitatively. A kinetic study on the quenching of the NQ-6 emission by hydrogen-donor type antioxidants (three tocopherol analogues, catechin, and 2,6-di- tert -butyl-4-methylphenol) in ethanol was performed. The quenching rate constant obtained from the Stern–Volmer plots for the steady-state fluorescence intensity was consistent with the second-order rate constant of each antioxidant for the free-radical scavenging. The NQ-6 emission is thought to be the delayed fluorescence caused by the thermal population to the excited singlet state from the triplet state. Thus, the fluorescence quenching occurred through a hydrogen atom transfer reaction from an antioxidant to NQ-6 in the excited triplet state ( 3 NQ-6 * ). The second-order rate constant for the reaction between 3 NQ-6 * and α -tocopherol was estimated to be 1.2 × 10 10 M −1 s −1 from the quenching parameter and the 3 NQ-6 * lifetime in ethanol (1.2 μs) measured with the transient absorption. From the high reactivity of 3 NQ-6 * to the antioxidants and the amphiphilic property of NQ-6 as a vitamin K model, NQ-6 is applicable to the quantitative antioxidant assay as a new fluorescence probe.

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.

Stable 9,9′-anthryl-anthroxyl radicals were synthesized and isolated, and the structures were fully characterized by single crystal X-ray diffraction analysis and ESR measurement. The resonance structure and steric protection of the peripheral positions and the most reactive 9-position of anthracene prolong the half-life of the radical in solution to 11 days.

Boron complexes of [14]triphyrins(2.1.1) were prepared from free-base [14]triphyrins(2.1.1) with phenylboron dichloride. The absorption spectrum of the meso-free [small beta]-alkyl-triphyrin boron complex in CH2Cl2 showed a broad weak band at around 640 nm assigned to transition from B-phenyl to the triphyrin, while that of the meso-aryl benzotriphyrin boron complex showed only Soret and Q bands.

9,10-Quinoxaline-fused porphycenes 1a-H2 and 1b-H2 were synthesized by intramolecular McMurry coupling. As a result of the annulation of the quinoxaline moiety on the porphycene skeleton, 1a-H2 and 1b-H2 display absorption and fluorescence in the near infra-red (NIR) region. Additionally, the quinoxaline moieties of 1a-H2 and 1b-H2 act as electron-withdrawing groups, introducing lower reduction potentials than for pristine porphycene. The protonation occurred at the nitrogen atoms in the cavity of freebase porphycenes and at the quinoxaline moieties for their nickel complexes to give diprotonic species.

An optically and thermally responsive boron dipyrromethene (BODIPY) dye, namely, meso-2-(9,10-dihydro-9,10-ethanoanthracene-11,12-dione) (DK)-linked, bicyclo[2.2.2]octadiene (BCOD)-fused BODIPY (BCOD-DK), was synthesized. The weakly luminous structure of BCOD-DK can be changed quantitatively to that of the strongly fluorescent BODIPY BCOD-Ant by optical excitation at the DK unit, which induces double decarbonylation of the DK unit to give an anthracene unit. The solvent effect on the fluorescence properties of BCOD-DK suggests that the dramatic change in fluorescence intensity is controlled by intramolecular electron transfer from the BODIPY moiety to the meso-DK substituent. BCOD-DK is converted to meso-DK benzene-fused BODIPY (Benzo-DK) by heating at 220 °C with 64-70 nm redshift of absorption and fluorescence peaks without changing the fluorescence quantum yield of ΦF =0.08 in dichloromethane. Benzo-DK can be converted to strongly fluorescent meso-anthracene benzene-fused BODIPY Benzo-Ant by optical excitation. Thus, BCOD-DK can show four different optical performances simply by irradiation and heating, and hence may be applicable for optical data storage and security data encryption.

Double hydrogen transfer occurring in both ground and the lowest electronically excited singlet states was studied for a series of 19 differently substituted porphycenes. The rates of tautomerization have been determined using femtosecond pump–probe spectroscopy with polarized light. The values vary by over 3 orders of magnitude, suggesting the importance of tunneling. Good correlation exists between the values of the rates and the parameters characterizing the strength of two intramolecular hydrogen bonds: proton NMR shift, distance between the hydrogen-bonded nitrogen atoms, and the NH stretching frequency. While hydrogen-bond strength is the main factor determining the rate of double hydrogen transfer, other factors, such as static and dynamic symmetry breaking and the population of low-frequency vibrations also have to be taken into account.

A 2,6-distyryl-substituted boradiazaindacene (BODIPY) dye and a new series of 2,6-p-dimethylaminostyrene isomers containing both α- and β-position styryl substituents were synthesized by reacting styrene and p-dimethylaminostyrene with an electron-rich diiodo-BODIPY. The dyes were characterized by X-ray crystallography and NMR spectroscopy and their photophysical properties were investigated and analyzed by carrying out a series of theoretical calculations. The absorption spectra contain markedly redshifted absorbance bands due to conjugation between the styryl moieties and the main BODIPY fluorophore. Very low fluorescence quantum yields and significant Stokes shifts are observed for 2,6-distyryl-substituted BODIPYs, relative to analogous 3,5-distyryl- and 1,7-distyryl-substituted BODIPYs. Although the fluorescence of the compound with β-position styryl substituents on both pyrrole moieties and one with both β- and α-position substituents was completely quenched, the compound with only α-position substituents exhibits weak emission in polar solvents, but moderately intense emission with a quantum yield of 0.49 in hexane. Protonation studies have demonstrated that these 2,6-p-dimethylaminostyrene isomers can be used as sensors for changes in pH. Theoretical calculations provide strong evidence that styryl rotation and the formation of non-emissive charge-separated S1 states play a pivotal role in shaping the fluorescence properties of these dyes. Molecular orbital theory is used as a conceptual framework to describe the electronic structures of the BODIPY core and an analysis of the angular nodal patterns provides a reasonable explanation for why the introduction of substituents at different positions on the BODIPY core has markedly differing effects.

Benzene-fused bis-(borondipyrromethene)s (bis-BODIPYs) were synthesized by retro-Diels–Alder reaction of the corresponding bicyclo[2.2.2]octadiene-fused (BCOD-fused) bis-BODIPYs, which were, in turn, prepared from 4,8-ethano-4,8-dihydropyrrolo[3,4-f]isoindole derivatives. The π-fused bis-BODIPY chromophores were designed to show intensive absorption and strong fluorescence in the near-infrared region and not to have any strong absorption in the visible region. A 6,10-dibora-5a,6a,9a,10a-tetraaza-s-indaceno[2,3-b:6,5-b′]difluorene derivative (syn-bis-benzoBODIPY) obtained by a thermal retro-Diels–Alder reaction of the corresponding BCOD-fused BODIPY dimer has strong absorption and emission bands at 775 and 781 nm, respectively. The absolute quantum yield is 0.36. The absorption is more than 5.0 times stronger than other absorptions observed in the visible region. In the case of 6,15-dibora-5a,6a,14a,15a-tetraaza-s-indaceno[2,3-b:6,7-b′]difluorene derivatives (anti-bis-benzoBODIPY), the absorption and emission maxima exceed 840 nm.

Free base and zinc porphyrins are linked with fullerene (C(60)) through β,β'-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.

Correction for ‘9,9′-Anthryl-anthroxyl radicals: strategic stabilization of highly reactive phenoxyl radicals’ by Tatsuya Aotake et al., Chem. Commun., 2015, DOI: 10.1039/c4cc10104a.

The non-luminous precursor, 2-(1-pyrenyl)-9,10-dihydro-9,10-ethanoanthracene-11,12-dione, was photochemically converted to highly-fluorescent 2-(1-pyrenyl)anthracene quantitatively in solution and in the PMMA film and the fluorescence quantum yield of the acene in benzonitrile was as high as 0.99.

A new α-diketoporphyrin and the corresponding Pd complex were prepared from the monoanthroporphyins and their photochemical properties were investigated by measurements of absorption and emission spectra, fluorescence lifetimes, laser flash photolysis, cyclic voltammetry, and theoretical calculations. Intramolecular electron transfer from the porphyrin singlet excited state to the diketone moiety was observed for the free base α-diketoporphyrin in benzonitrile, but this was not observed in toluene. Photoreactivity of the α-diketoporphyrins was also examined by irradiation at the Soret and Q bands. When the Soret band of the freebase α-diketoporphyrin was irradiated, cleavage of the diketone moiety occurred to afford the monoanthroporphyrin with the release of two CO molecules quantitatively in both benzonitrile and toluene. When the Q band of the freebase α-diketoporphyrin was irradiated, no photocleavage reaction occurred in toluene. In contrast to the freebase α-diketoporphyrin, the photocleavage reaction of the Pd complex occurred with irradiation at the Q band as well as the Soret band to afford the monoanthroporphyrin quantitatively in toluene. The photocleavage reaction proceeded much more effectively in toluene than in benzonitrile. The occurrence of rapid photoinduced electron transfer from the singlet excited state porphyrin to the diketone moiety, which was detected by femtosecond laser flash photolysis measurements, results in a significant decrease in the singlet excited state lifetime, prohibiting the photocleavage reaction in benzonitrile. Thus, the Pd α-diketoporphyrin can act as an excellent precursor for the corresponding acene in toluene. The photocleavage process provides a convenient and inexpensive method to make the thin film.