Optical Spectra of Phthalocyanines and Related Compounds

Isago, Hiroaki

doi:10.1007/978-4-431-55102-7

Cited by 47 publications

(56 citation statements)

References 110 publications

(191 reference statements)

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“…a tetramer) and hence these spectral intensities are multiplied 4 times absorption band with its peak at 677 nm. This spectrum is typical for metalated phthalocyanines with C 4 symmetry [29][30][31] and the prominent band is generally called a "Q band" and assigned as a degenerate HOMO-LUMO transition in the macrocyclic ligand [29]. H 2 Pc in ethanol shows similarly sharp but twin bands in the same region (663 and 701 nm), which are characteristic of free-base phthalocyanines [29][30][31].…”

Section: Resultsmentioning

confidence: 99%

“…This spectrum is typical for metalated phthalocyanines with C 4 symmetry [29][30][31] and the prominent band is generally called a "Q band" and assigned as a degenerate HOMO-LUMO transition in the macrocyclic ligand [29]. H 2 Pc in ethanol shows similarly sharp but twin bands in the same region (663 and 701 nm), which are characteristic of free-base phthalocyanines [29][30][31]. The splitting of the Q band in H 2 Pc is attributed to the lower symmetry (C 2 ) of the macrocycle due to the presence of two hydrogen atoms in the cavity [29].…”

Section: Resultsmentioning

confidence: 99%

“…On the other hand, both of the compounds show a broad band with its peak around 615 nm in pure water. These spectra are characteristic of strongly aggregated phthalocyanines [29][30][31]. The significant broadening of the Q band in aqueous solutions reveals that H 2 Pc and Cu(Pc) molecules strongly aggregate therein.…”

Section: Resultsmentioning

confidence: 99%

“…However, as aggregationdisaggregation phenomena are basically equilibria involving monomer, dimer, trimer or higher aggregates, concentration study on the macrocyclic compound would be a more preferable approach to investigate such phenomena. Moreover, solvent study can give rise to misleading results due to unexpected reaction(s) with impurities contained in the solvent used [31].…”

Section: Aggregation In Aqueous Solutionsmentioning

confidence: 99%

“…Aggregation of dye molecules is quite an interesting subject from a viewpoint of supramolecular chemistry [28] because this gives rise to significant changes in their physical properties. Eventually aggregation of phthalocyanines produces dramatic spectral changes according to the manner of alignment of macrocycles due to exciton coupling between the chromophores [29][30][31]. However, this also may cause a serious problem in some of the aforementioned applications, in particular when their excited states are involved [12][13][14][15][16], because photo-excited dye molecules in aggregates are rapidly relaxed to their ground state and lifetimes of their excited states are significantly shortened and consequently their photochemical activities are considerably reduced [32,33].…”

Section: Introductionmentioning

confidence: 99%

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Solvent effects on molecular aggregation of highly water-soluble phthalocyanines

Isago

Fujita

2018

J. Porphyrins Phthalocyanines

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Molecular aggregation phenomena of a highly water-soluble, metal-free phthalocyanine, H 2 Pc, and its copper complex, Cu(Pc); where Pc denotes tetrakis{(2′,6′-dimethyl-4′-sulfonic acid) phenoxy}phthalocyaninate) in water, ethanol, and their mixed solvent systems have been investigated by spectroscopic approach. In both aqueous and ethanolic solutions, H 2 Pc molecules aggregate in a slipped-cofacial manner, although very weakly in ethanol. On the other hand, Cu(Pc) molecules aggregate in a cofacial manner in water while aligning in a slipped-cofacial manner in ethanol. Magnetic circular dichroism spectroscopy was undertaken to investigate aggregation behaviors of Cu(Pc) in water and ethanol. Presence of 4-phenylpyridine in ethanol effectively inhibited aggregation of Cu(Pc) molecules, although little affected the spectra of the monomers. In a mixed solvent system, where water/ethanol = 10/90 (v/v), Cu(Pc) is free from aggregation up to almost 10 -4 M. Driving forces of this molecular aggregation are discussed on the basis of p-p interaction and coordination chemistry involving copper ions. KEYWORDS:water-soluble, phthalocyanine, copper, metal-free, magnetic circular dichroism, aggregation-disaggregation, J-aggregation, solvent effects.

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Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Aggregation In Aqueous Solutionsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Solvent effects on molecular aggregation of highly water-soluble phthalocyanines

Isago

Fujita

2018

J. Porphyrins Phthalocyanines

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Thioethyl‐Porphyrazine/Nanocarbon Hybrids for Photoinduced Electron Transfer

Belviso

Capasso

Santoro

et al. 2018

Adv Funct Materials

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Running title: Hybrids of thioalkyl-porphyrazines with nanocarbons ABSTRACTWe designed a novel pyrene-substituted thioethyl-porphyrazine (PzPy) and the formation of supramolecular assembly with nanocarbons demonstrating photoinduced electron transfer ability. As revealed by spectroscopic and electrochemical studies, PzPy displays wide spectral absorption in the visible range, charge separation upon photoexcitation, as well as bandgap and highest occupied/lowest unoccupied molecular orbital (HOMO/LUMO) energy values, matching the key requirements of organic optoelectronic. Moreover, the presence of a pyrene moiety promotes attractive interactions with -conjugated systems. In particular, theoretical calculations show that in the PzPy the HOMO and LUMO are localized on different positions of the molecule, i.e., the HOMO on the pyrene moiety and the LUMO on the macrocycle. Therefore, HOMO-LUMO excitation gives rise to a charge separation, preventing excitons recombination. Two kinds of non-covalent hybrid composites are prepared by mixing the PzPy with single wall carbon nanotubes (SWNTs) and graphene nanoflakes (GNFs), respectively, and used for photocurrent generation through charge transfer processes between PzPy and nanocarbons. Photoconduction experiments show photocurrent generation upon visible light irradiation of both PzPy/SWNT and PzPy/GNF composites (0.78 and 0.71 mA/W at 500 nm, respectively), demonstrating their suitability for optoelectronic applications and light harvesting systems.widely used for this purpose. [12] More recently, carbon nanotubes (CNTs) have also been reported as acceptors, [13][14][15] and the use of graphene is rapidly raising too. [16][17][18][19][20][21] In particular, single wall carbon nanotubes (SWNTs) have been proposed as acceptor material since they possess nanoscale diameter and large aspect ratio in combination with favorable electrical transport properties. [14,19] Furthermore, SWNTs show unique optoelectronic properties, electrochemical stability, and energy levels that can be suitably coupled to those of conjugated polymers with long-range charge transport properties to make efficient composites for optoelectronic devices. [19] Similarly, graphene has high electron and hole mobility at room temperature, with reported values exceeding 15000 cm 2 V -1 s -1 . [20][21][22] Graphene is also electrochemically stable, with a very high specific surface area (∼ 2630 m 2 g −1 ), surpassing that of both SWNTs and graphite. [23,24] Moreover, graphene has an optical transmittance over the visible range of 97.7%, [25] and its work function (∼ 4.5 eV) [26] can be matched to the energy levels of organic donor materials. [22] Moving from these motivations, both SWNTs and functionalized graphene have been used as electron acceptors in combination with conjugated polymer donors, such as poly(3-octylthiophene) (P3OT), or poly(pphenylenevinylenes), and poly(3-hexylthiophene) (P3HT), [14,19,27,28] especially in organic bulk heterojunction (BHJ) solar cell devices. [19] Amongst the non-poly...

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The Redox‐Active Chromium Phthalocyanine System: Isolation of Five Oxidation States from Pc⁴⁻Cr^I to Pc²⁻Cr^III

Zhou

Thompson

Leznoff

et al. 2016

Chemistry A European J

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The preparation and structural characterization of a series of chromium phthalocyanine complexes with multiple metal and ring oxidation states were achieved using PcCr (1) (Pc=phthalocyanine) or PcCr (THF) (1⋅THF ) as starting materials. The reaction of soluble 1⋅THF with Br or I gave the PcCr halide complexes PcCrX(THF) (X=I/I , Br; 3, 4, respectively). Treatment of 1 with 0.5 equivalent of PhIO or air generated the dinuclear [PcCr(THF)] (μ-O) (5), whereas the addition of one equivalent of AgSbF to 1 resulted in oxidation to THF-solvated octahedral [PcCr (THF) ]SbF (6). The reduction of 1 with three sequential equivalents of KEt BH resulted in the isolation of [K(DME) ][Pc Cr ] (7), [K(DME) ] [Pc Cr ] (8) and [K (DME) ][Pc Cr ] (9), respectively. The reduced products are deep purple in colour, with visible absorption maxima between 500-580 nm. The ring-reduced complexes 7 and 8 are monomeric, whereas 9 is a 1D chain of dinuclear [PcCr] units with intercalated K cations and supported by Cr-Cr interactions of 2.988(2) Å. Addition of four equivalents of KC resulted in the demetallated product PcK (DME) (10), which has a 1D chain structure. The isolation and structural characterization of new PcCr complexes spanning five oxidation states, including rare examples of crystalline reduced Pc-ring species emphasizes the broad redox activity and stability of phthalocyanine-based complexes.

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Optical Spectra of Phthalocyanines and Related Compounds

Cited by 47 publications

References 110 publications

Solvent effects on molecular aggregation of highly water-soluble phthalocyanines

Solvent effects on molecular aggregation of highly water-soluble phthalocyanines

Thioethyl‐Porphyrazine/Nanocarbon Hybrids for Photoinduced Electron Transfer

The Redox‐Active Chromium Phthalocyanine System: Isolation of Five Oxidation States from Pc⁴⁻Cr^I to Pc²⁻Cr^III

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Optical Spectra of Phthalocyanines and Related Compounds

Cited by 47 publications

References 110 publications

Solvent effects on molecular aggregation of highly water-soluble phthalocyanines

Solvent effects on molecular aggregation of highly water-soluble phthalocyanines

Thioethyl‐Porphyrazine/Nanocarbon Hybrids for Photoinduced Electron Transfer

The Redox‐Active Chromium Phthalocyanine System: Isolation of Five Oxidation States from Pc4−CrI to Pc2−CrIII

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The Redox‐Active Chromium Phthalocyanine System: Isolation of Five Oxidation States from Pc⁴⁻Cr^I to Pc²⁻Cr^III