- Changes of phthalocyanine visible color caused by near-IR solvatochromism
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Herein, we show that the Zn complex of 1,4,8,11,15,18,22,28-octakis(butoxy)phthalocyanine exhibits solvatochromism and characterize the corresponding visible color changes. In particular, we reveal that although the variation of the solvent-dependent position of the Q band is relatively small (~100 nm), the solution colors change from red to yellow and green depending on the composition of the solvent mixture. Moreover, the above Q band was located at the border between the visible and near-IR regions, i.e. its red shift could not be directly recognized by the human naked eye. Substituents on oxygen atoms were shown to influence phthalocyanine aggregation and thus affect near-IR absorption, with the observed near-IR solvatochromism providing a new strategy of color change in response to weak external stimuli.
- Furuyama, Taniyuki,Uchiyama, Shiori,Iwamoto, Takayuki,Maeda, Hajime,Segi, Masahito
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- Preferential Formation of Side-Pocket-Substituted Zinc Phthalocyanines Emitting Beyond 800 nm
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A series of zinc (1,4,8,11,15,18,22,25-octabutoxy)phthalocyanine (2) complexes that spontaneously form 5-coordinate complexes with anionic axial ligands neutralized with side-pocket cations, of the form Cation-PcZnX (X=Cl, OAc; Cation=H+ or Li+), was synthesized and structurally characterized. The side-pocket protonation of the axial-chloride species pushed the emission maximum from 760 nm (for axial ligand-free 2) to 826 nm, well into the NIR region. A 1D-coordinated chain bridged by lithium and chloride atoms was isolated and structurally characterized, representing the first side-pocket metalated PcM species. This preferential formation of axially substituted [PcZnX]? “ate” complexes and their sequestration of both protons and lithium cations, opens a new series of materials with unique structural and electronic properties. Furthermore, their ability to both absorb and emit in the NIR region makes them desirable for numerous applications.
- McKearney, Declan,Roberts, Ryan J.,Mitchell, Devon,Cheung, Jeffrey C. F.,Williams, Vance E.,Leznoff, Daniel B.
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- Phthalocyanine Labels for Near-Infrared Fluorescence Imaging of Solid Tumors
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Diamagnetic metal complexes of phthalocyanines with n-butoxyl groups in all the α-benzo positions of the macrocycle skeleton, MPc(OBu)8, have strong near-infrared absorptions and intense fluorescences that are Stokes shifted by more than 15 nm. Interestingly, the silicon complex 6 is also remarkably photostable and nontoxic. The use of 6 in the fluorescence imaging of BALB/c mice bearing a 4T1-luc2 tumor in the mammary fat pad unambiguously revealed the presence of the tumor when it was only 1 mm in diameter and was not visible with the naked eye. Compound 6 has an intrinsic ability to accumulate in the tumor, adequate spectroscopic properties, and excellent stability to function as a NIR fluorescent label in the early detection of tumors.
- Lobo, Ana C. S.,Silva, Alexandre D.,Tomé, Vanessa A.,Pinto, Sara M.A.,Silva, Elsa F.F.,Calvete, Mário J.F.,Gomes, Célia M.F.,Pereira, Mariette M.,Arnaut, Luis G.
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- Predominant effect of connecting atom and position of substituents on azomethine nitrogens' basicity in phthalocyanines
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The basicity of azomethine nitrogens was studied on a series of phthalocyanines (Pcs) that differed in a position of substituent, i.e. peripherally (β-series) and non-peripherally substituted Pcs (a-series), and in a type of substituent (alkylsulfanyl, alkyloxy or alkyl). Appropriate 3,6-or 4,5-disubstituted phthalonitriles were prepared either by nucleophilic substitution or by Negishi coupling. Target zinc Pcs were synthesized by Linstead method. The basicity was studied by the mean of absorption and 1H NMR spectroscopies in chloroform upon titration with trifluoroacetic acid. Equilibrium constants (log K) indicated significant difference within the series. Basicity decreased as follows: α-alkyloxy > α-alkylsulfanyl > β-alkyloxy > β-alkyl > β-alkylsulfanyl ~ α-alkyl with log K higher than 7 down to 2.6 M-1. Increased basicity of a-alkyloxy and a-alkylsulfanyl Pcs is caused by the stabilization of trapped hydrogen at azomethine nitrogen via hydrogen bonding and van der Waals interactions, respectively. The basicity of b-series clearly correlated with the electronic effects of substituents. 1H NMR studies confirmed the possibility of the weak bonding interactions in a-alkyloxy and α-alkylsulfanyl Pcs, however, the position of the 1H NMR signal of azomethine-NH proton was even more influenced by the electronic effects of present substituents than by the weak interactions.
- Cidlina, Antonin,Svec, Jan,Ludvová, Lucie,Kune?, Ji?í,Zimcik, Petr,Novakova, Veronika
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- Temperature-dependent changes in the molecular orientation and visible color of phthalocyanine films
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A simple phthalocyanine zinc complex exhibits a visible color change in response to weak external stimuli, i.e., changes in solvent and temperature. Its chromism was attributed to its controlled aggregation via weak interactions between the central metal and peripheral oxygen atoms. In solution, intense absorption and fluorescence bands appeared in both the longer-wavelength and NIR region in non-coordinating solvents, while a simple sharp Q band was observed in coordinating solvents. Variable-temperature absorption spectra and fluorescence lifetime measurements were used to characterize the aggregation-induced absorption and emission in non-coordinating solvents. A selective aggregation-disaggregation process was also observed in thin films of this phthalocyanine zinc complex, and the optical properties of the film depend on the annealing temperature. The changes in the NIR region lead to a sizable visible color change that is recognizable by the naked human eye. The temperature-dependent control of the aggregation process in the thin film was confirmed using operando spectroscopy techniques. This journal is
- Chikamatsu, Tatsuki,Furuyama, Taniyuki,Horikawa, Takafumi,Maeda, Hajime,Segi, Masahito,Taima, Tetsuya,Takahashi, Hiromi,Uchiyama, Shiori
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p. 31348 - 31354
(2020/09/21)
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