Penetrated ion pairs: photochemistry of cyanine dyes within organic borates

Yang, Xiqiang; Zaitsev, Alexei; Sauerwein, Björn; Murphy, Sean T.; Schuster, Gary B.

doi:10.1021/ja00028a075

Cited by 59 publications

(32 citation statements)

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“…Once NaTPB (or NaTFPB) is added into the aqueous PIC-Br solution, TPB À (or TFPB À ) and PIC þ contact with each other to form an electrically neutral ion-pair because of the strong electrostatic attraction between the oppositely charged ions. 31 The contact ion-pairs will aggregate themselves by van der Waals attractive interaction to produce embryos or nuclei for the particle formation. 19 Note that the TPB (or TFPB) anion does not have a planar structure but rather a tetrahedral structure due to the phenyl rings, 39 so that the growth of nuclei caused by the agglomeration of such contact ion-pairs should lead to spherical nanoparticles.…”

Section: Resultsmentioning

confidence: 99%

Organic Nanoparticles of Cyanine Dye in Aqueous Solution

Ou¹,

Yao²,

Kimura³

2007

Bulletin of the Chemical Society of Japan

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Ion-based organic dye nanoparticles ranging from tens to hundreds of nanometers have been prepared in aqueous solution. The synthetic approach is based on ''ion-association'' (hydrophobic ion-pair formation) in water between the dye cation pseudoisocyanine (PIC) and the anion tetraphenylborate (TPB) or tetrakis(4-fluorophenyl)borate (TFPB) ion. Size tuning of spherical and amorphous PIC nanoparticles was accomplished by varying the molar ratio () of the loaded anion to the dye cation. Electrophoretic characterization revealed that the increase in surface adsorption of anions onto PIC particles brings about an increase in the negative surface charge density, causing a reduction in the surface tension and the mean size of nanoparticles. We found that the optical absorption properties of the PIC nanoparticles exhibited (i) matrix dependence, that is, the 0-0 band position of the PIC chromophore within similar-sized nanoparticles was dependent on the type of counter anions used, and (ii) size dependence, i.e., the 0-0 band position of the PIC chromophore was dependent on the mean nanoparticle diameter when the particles were prepared using the same counter anion.For more than a decade, inorganic nanoparticles, such as semiconductor and metal nanoparticles, have attracted a great deal of attention from experimentalists and theoreticians and have been studied extensively. This is due to the fact that such nanoparticles are intermediate in size between single molecules and bulk materials and have interesting physical/chemical properties that are size dependent.1-5 Organic nanoparticles consisting of small molecules, on the other hand, have not been as well investigated as inorganic nanoparticles probably because of the lack of well-defined synthetic approaches. In organic nanoparticles, weak van der Waals intermolecular and hydrogen-bonding interactions are responsible for the specific electronic/optical properties that are fundamentally different from those of inorganic metals or semiconductors. 6 Taking the diversity and physiological activity of organic molecules into consideration, scientific and technological interest in organic nanoparticle has been clearly increasing. 7-9To fabricate organic nanoparticles, a few methods have been applied so far, such as laser ablation, 10 sol-gel method, 11 and the reprecipitation method. 12 In particular, since the first report by Nakanishi and co-workers on the synthesis of organic nanoparticles by using the reprecipitation method, this technique has been widely employed to prepare organic nanoparticles of a wide variety of compounds.12-18 The reprecipitation method is based on the adjustment of inherent solubility of organic materials by adding electrolytes or organic co-solvents. Despite the simplicity in its operation, it is fraught with difficulties. For instance, organic solvents or surfactants are often used to control the particle size, and the obtained size distributions are relatively broad, which is in stark contrast to those for the well-controlled semiconductor or ...

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Section: Resultsmentioning

confidence: 99%

Organic Nanoparticles of Cyanine Dye in Aqueous Solution

Ou¹,

Yao²,

Kimura³

2007

Bulletin of the Chemical Society of Japan

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“…For these compounds, it has been found that they can photoactivate damage to cancer cells with high efficiency [8]. The compound PD1(I) is the familiar symmetric tricarbocyanine dye HITCI [14], PD1(ClO 4 ) is its cationic analog with the counterion ClO 4 − ; PD2(ClO 4 ) and PD2(Br) are cationic analogs (with the anions ClO 4 − and Br -) of the dye with a 4-chloro-3,5-substituted heptamethine conjugation chain and N-modified indolenine hetero residues [15]. As the solvents, we used deuterated chloroform, deuterated acetonitrile, chloroform, dichlorobenzene (DCB), ethanol, and methylene chloride.…”

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

“…The fluorescence quantum yield and the fluorescence lifetime of the polymethine dye molecules decrease symbatically with strengthening of the anion-cation interactions [2, 3]. In the ion pairs, the probabilities of torsional vibrations in the polymethine chain are higher and the yield for photoisomerization of the molecules is higher; the degree of vibronic interactions and the probabilities of rotation about bonds are higher as more stable ion pairs are formed [4][5][6].Despite the significant number of publications devoted to study of the photophysical properties of polymethine dyes in different types of solvents, due attention has not been paid to the effect of the state of ionic equilibria on the efficiency of singlet oxygen generation by polymethine dyes. At the same time, such a study is important from both a scientific and an applied viewpoint.…”

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Generation of singlet oxygen by indotricarbocyanine dyes in low-polarity media

et al. 2008

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We present the results of a study of the spectral luminescence properties of three groups of indotricarbocyanine dyes, each of which is formed from compounds with the same cation and different anions. In high-polarity solvents, in the absorption and emission spectra of the dyes we see one type of center; in low-polarity solvents, due to the presence of different ionic forms of the dyes (free ions, contact ion pairs), we observe either one type or two types of centers. By analysis of the luminescence of molecular oxygen in the 1.27 µm spectral region, we determined the efficiency of photosensitization of 1 O 2 formation by dyes in deuterated solvents. We have shown that in low-polarity solvents, the yield for singlet oxygen generation is higher for indotricarbocyanine dyes which are found in the contact ion pair state and which also contain a heavy atom (I) in the anion. We have observed that an increase in the fraction of contact ion pairs in solution as the dye concentration increases or when an additional salt is introduced leads to an increase in the quantum yield for generation of singlet oxygen. In polar deuterated acetonitrile, the counterion has no effect on the efficiency of photosensitization of oxygen by the dyes.Introduction. Most polymethine dyes are salts whose molecules in solutions can be found in the form of an equilibrium mixture of several types of ionic forms (free ions, contact and solvent-separated ion pairs) [1]. The equilibrium between these forms is shifted toward an increase in the fraction of one form when the temperature and the nature of the solvent are varied, when the anion is substituted, and when ionic and solvating additives are added to the solution. The state of the ionic equilibrium in solutions has an effect on the processes of dissipation of the electronic excitation energy in the polymethine dye molecules. The fluorescence quantum yield and the fluorescence lifetime of the polymethine dye molecules decrease symbatically with strengthening of the anion-cation interactions [2, 3]. In the ion pairs, the probabilities of torsional vibrations in the polymethine chain are higher and the yield for photoisomerization of the molecules is higher; the degree of vibronic interactions and the probabilities of rotation about bonds are higher as more stable ion pairs are formed [4][5][6].Despite the significant number of publications devoted to study of the photophysical properties of polymethine dyes in different types of solvents, due attention has not been paid to the effect of the state of ionic equilibria on the efficiency of singlet oxygen generation by polymethine dyes. At the same time, such a study is important from both a scientific and an applied viewpoint. The applied importance is due to prospects for using these dyes for photochemotherapy of cancer and as biological fluorescent labels [7][8][9], and also because in biological structures, their molecules are mainly found in the form of contact ion pairs [10]. In this case, the efficiency of polymethine dyes as photosensitizers...

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“…[18][19][20] Cy3 excited state dynamics in solution are strongly dependent on the nature of the counter-anion. [21][22][23][24][25] Cy3 hexauorophosphate (Cy3-P) tends to photoisomerize to the cisisomer and has a rather poor uorescence quantum yield. The excited state decays in a few hundreds of picoseconds, while the cis-isomer absorbing at 580 nm is characterized by a microsecond lifetime.…”

Section: 13mentioning

confidence: 99%

Ultrafast charge transfer in solid-state films of pristine cyanine borate and blends with fullerene

et al. 2015

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Photoinduced electron transfer in light-absorbing materials is the first step towards charge separation and extraction in small molecule-based organic solar cells. The excited state dynamics of the cyanine dye cation Cy3 paired with a tetraphenylborate counter-anion (Cy3-B) was studied in pristine solid-state films of the dye and in blends with the electron acceptor material PCBM. Here we show that photoexcited Cy3-B in pure films undergoes intra-ion pair reductive quenching on the picosecond time scale, while in blends with PCBM sub-picosecond formation of the Cy3 oxidized species is observed upon electron injection from the dye excited state into the fullerene. Kinetic competition between light-induced electron-and hole transfer processes strongly depends on the PCBM content in the blends. A high PCBM loading produces a fully intermixed phase, where the cyanine oxidized states appear on ultrashort (<160 fs) time scales. Lower PCBM contents, in contrast, lead to a Cy3-B segregated phase on top of the intermixed phase and slower excited state quenching. These findings show that the phase morphology indeed controls to a large extent the efficiency of primary photoinduced charge separation, on which small molecule-based organic photovoltaic cells rely.

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Penetrated ion pairs: photochemistry of cyanine dyes within organic borates

Cited by 59 publications

References 0 publications

Organic Nanoparticles of Cyanine Dye in Aqueous Solution

Organic Nanoparticles of Cyanine Dye in Aqueous Solution

Generation of singlet oxygen by indotricarbocyanine dyes in low-polarity media

Ultrafast charge transfer in solid-state films of pristine cyanine borate and blends with fullerene

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