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Fluorescence properties of indolenium carbocyanine dyes in solid state
Tetrahedron 71 (2015) 3528e3534
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Fluorescence properties of indolenium carbocyanine dyes in solid state M. Matsui *, S. Ando, M. Fukushima, T. Shibata, Y. Kubota, K. Funabiki Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 3 February 2015 Received in revised form 5 March 2015 Accepted 6 March 2015 Available online 27 March 2015
The fluorescence intensity of indolenium carbocyanine dyes in the solid state depended on both the alkyl group on the nitrogen atoms in the indolenium rings and the kind of counter anions. The N-propyl derivative having a bis(trifluoromethylsulfonyl)imide anion, whose fluorescence maximum was observed at 657 nm with shoulder peaks, exhibited the highest fluorescence quantum yield of 0.31. The wave deconvolution of fluorescence spectrum indicated three components assigned to the S1,0/S0,0, S1,0/S0,1, and S1,0/S0,2 transitions. The X-ray structure of this compound indicates an isolated monomer-type packing, whereas the other derivatives shows the isolated dimer-type packing or consequent p/p stacking. The cyanine dye having the least p/p interactions among adjacent cationic fluorophores could exhibit the most intense fluorescence in the solid state. Ó 2015 Elsevier Ltd. All rights reserved.
Keywords: Fluorescence spectrum Indolenium carbocyanine dye Solid state Single X-ray structure Wave deconvolution
1. Introduction Cyanine dyes cover the wide range of absorption band from visible to near-infrared region. They have been used as probes,1 information recording materials,2 emitters,3 and sensitizers.4 Cyanine dye are one of the classical fluorescent dyes. Organic fluorescent dyes are classified into three types: neutral, anionic, and cationic derivatives. Among these types, a number of neutral solidstate fluorescent compounds have been reported.5 For the anionic derivatives, the relationship between the emission spectra and Xray structure of arylsulfonates have been reported.6 For cationic dyes, only the solid-state fluorescence of 1,2-azaborine cations,7 pyridinium dyes,8 and styryl dyes9 have been reported. To our knowledge, no detailed studies on the solid-state fluorescence of cationic cyanine dyes has been reported so far. We report herein the solid-state fluorescence of indolenium carbocyanine dyes.
were treated with lithium salts 19c, 19d, and 19e to afford the corresponding anion-exchanged derivatives 14d, 15d, 16c, 16d, 16e, 17d, and 18d.
2. Results and discussion 2.1. Synthesis The synthesis of indolenium carbocyanine dyes are shown in Scheme 1. 2,3,3-Trimethylindolenine (1) was N-alkylated with alkyl halides 2e7 to give 1-alkyl-2,3,3-trimethyl-3H-indolenium halides 8e12, which were further allowed to react with triethoxymethane (13) to produce 14b, 15b, 16a, 16b, 17b, and 18b. These compounds * Corresponding author. Tel.: þ81 58 293 2601; fax: þ81 58 293 2794; e-mail address: [email protected] (M. Matsui). http://dx.doi.org/10.1016/j.tet.2015.03.027 0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.
Scheme 1. Reagents and conditions: i) 1 (1.0 equiv), 2e7 (3.3 equiv), MeCN, reflux, 1e2 d, ii) 8e12 (1.0 equiv), 13 (0.6 equiv), pyridine, reflux, 6 h, iii) 14b, 15b, 16a, 16b, 17b, and 18b (1.0 equiv), 19 (1.2 equiv), acetoneewater, rt, 6 h.
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2.2. UVevis absorption and fluorescence spectra The UVevis absorption and fluorescence spectra of cyanine dyes in solution are shown in Fig. 1. Fig. 1a shows the effect of counter anion on the UVevis absorption and fluorescence spectra. Two absorption maxima (lmax) were observed at around 560 and 525 nm with a small shoulder peak at around 490 nm. The molar absorption coefficients (ε) were calculated in the range of 144,000 to 151,000 and 68,400 to 77,800 dm3 mol1 cm1, respectively. No remarkable differences in the UVevis absorption band were observed among 16a, 16b, 16c, 16d, and 16e. They showed the fluorescence maxima (Fmax) at around 575 and 620 nm with a shoulder peak at around 680 nm. The fluorescence quantum yield (Ff) was in the range of 0.04e0.20. The Stokes shift was very small, being ca. 15 nm.
Fig. 1. UVevis absorption and fluorescence spectra of indolenium carbocyanine dyes (1.0106 mol dm3) in toluene. Solid and dotted lines represents the fluorescence and UVevis absorption spectra, respectively. (a) N-propyl derivatives 16a, 16b, 16c, 16d, and 16e and (b) bis(trifluoromethylsulfonyl)imide derivatives 14d, 15d, 16d, 17d, and 18d.
Fig. 1b shows the effect of alkyl group on the UVevis absorption and fluorescence spectra. No marked differences in the UVevis absorption and fluorescence spectra were observed among 14d, 15d, 16d, 17d, and 18d. They also showed Fmax at around 575 and 620 nm with a shoulder peak at around 680 nm. The Ff was observed in the range of 0.07e0.14. Fig. 2 shows the fluorescence spectra in the solid state. The compounds were recrystallized from ethanol. The effect of the counter anion on the fluorescence spectrum is shown in Fig. 2a. The Fmax was observed at around 660 nm, being red-shifted compared with those in solution due to the intermolecular interactions in the solid state. A shoulder peak was also observed at around 690 nm. The fluorescence of bis(trifluoromethylsulfonyl)imide derivative (16d, Ff¼0.31) was remarkably intense compared with the bromide
Fig. 2. Fluorescence spectra of indolenium carbocyanine dyes in the solid state. Solid and dotted lines represents the fluorescence and excitation spectra, respectively. (a) Npropyl derivatives 16a, 16b, 16c, 16d, and 16e and (b) bis(trifluoromethylsulfonyl)imide derivatives 14d, 15d, 16d, 17d, and 18d.
(16a, Ff¼0.03), iodide (16b, Ff¼0.03), trifluoromethanesulfonate (16c, Ff¼0.06), and bis(perfluorpbutylsulfonyl)imide (16e, Ff¼0.02) derivatives. The effect of alkyl group on the solid-state fluorescence spectrum is indicated in Fig. 2b. The Fmax was observed at around 660 nm with a shoulder peak at around 690 nm. The fluorescence was more intense in the order of the alkyl group: Pr (16d, Ff¼0.31)>Et (15d, Ff¼0.19), Bu (17d, Ff¼0.17)>Me (14d, Ff¼0.03), Oct (18d, Ff¼0.02). Interestingly, compounds 15d, 16d, and 17d exhibited larger Ff value in the solid state than in toluene. The UVevis absorption and fluorescence spectra are also listed in Table 1. As the UVevis absorption spectra of cyanine dyes showed two absorption maxima with a shoulder peak, the wave deconvolution analyses of 16d, which showed the most intense fluorescence in the solid state, was performed using a Gaussian function. The result in solution is shown in Fig. 3. Fig. 3a shows that there are three components A0 , B0 , and C0 in the UVevis absorption band. Fig. 3b indicates the effect of concentration on the UVevis absorption spectrum of 16d. The normalized spectra were identical, indicating that the absorption peaks at 525 and 490 nm do not come from the dimers, oligomers and/or H-aggregates but from the monomer form. To assign the UVevis absorption band, the TDDFT calculations of 16d was performed. The results are shown in Fig. 4 and Table 2. The first and second absorption bands were predicted to be observed at 455 and 351 nm with the oscillator strengths of 1.27 and 0.01, respectively. Considering that the observed lmax at 560 nm is assigned to the S0/S1 transition, the observed lmax at 525 is too close to the first absorption band. Furthermore, the ε values at 525 nm (75,900) is too large to assign it to the S0 / S2 transition.
Table 1 UVevis absorption and fluorescence spectra of indolenium carbocyanine dyes Compd
Mp/ C
In toluenea
14d 15d 16a 16b 16c 16d 16e 17d 18d a b
132e133 170e172 255e257 260e262 201e202 203e204 80e82 170e171 81e83
524 523 525 528 526 525 526 525 526
(77,800), (77,000), (68,500), (68,700), (68,400), (75,900), (77,100), (76,700), (77,400),
Ff (solid)/Ff (toluene)
Solid state
lmax (ε)/nm 557 558 566 562 562 560 559 560 560
(146,000) (150,000) (147,000) (145,000) (144,000) (150,000) (151,000) (151,000) (151,000)
Measured at the concentration of 1.0 x 106 mol dm3. Measured by a Hamamatsu Photonics Quantaurus-QY instrument.
Fmax/nm
Ff b
lex/nm
Fmax/nm
Ff b
573 573 580 578 576 574 574 575 578
0.07 0.14 0.12 0.04 0.20 0.12 0.12 0.12 0.12
605 602 636 636 638 614 618 614 607
648 653 677 677 667 657 648 655 643
0.03 0.19 0.03 0.03 0.06 0.31 0.02 0.17 0.02
0.50 1.31 0.25 0.75 0.30 2.58 0.16 1.41 0.17
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2.3. X-ray crystallography
Fig. 3. UVevis absorption spectrum of 16d in toluene. (a) Wave deconvolution of UVevis absorption spectrum and (b) UVevis absorption spectra in different concentrations.
To understand why 16d exhibited the most intense fluorescence in the solid state, the X-ray crystallography of 16b, 16c, 14d, and 16d were performed. The X-ray structure of 16b is shown in Fig. 6. Molecules form a pair of head-to-tail dimers and are packed in a herring-bone fashion (overview (1)). A cationic fluorophore has Coulomb interactions with an iodine anion (overview (2)). The distance between the iodine anion and the cationic cyanine fluorophore is observed to be 4.07 A. Molecules A, B, and C are arranged in parallel (side view (1)). The tilt angle between B and D is 56 with CH/p interactions (side view (2)). The same result is observed for B and E (side view (3)). p/p Interactions are observed for A and B at the indolenium rings with interplanar distance of 3.62 A (top view (1) and side view (4)). Though two CH/p interactions are observed between B and C, the interplanar distance (4.93 A) is too long to have p/p interactions (top view (2) and side view (5)). Thus, 16b has isolated dimer-type packing.
Fig. 4. DFT calculations (B3LYP/6e31G(d,p)) for the cation of 16d.
Table 2 Excitation energies (eV, nm), main orbital transition, and oscillator strengths (f) for 16d calculated by TDDFT Transition
Ea (eV, nm)
Main orbital transitionb
f
lmax (ε)c/nm
S0/S1
2.73 (455)
HOMO to LUMO (0.71)
1.27
S0/S2
3.53 (351)
HOMO-1 to LUMO (0.68)
0.01
525 (75,900), 560 (150,000) d
a b c
Toluene was used as a solvent in the calculation. The coefficient of the wave function for each excitation is in absolute values. Observed lmax in toluene.
Therefore, components A0 , B0 , and C0 can be attributed to the transition comes from the vibration levels in the first transition, S0,0/S1,0, S0,0/S1,1, and S0,0/S1,2 transitions, respectively. The UVevis absorption bands come from the vibration level are observed in non-polar solvents.10 The wave deconvolution of the fluorescence spectrum of 16d is shown in Fig. 5. The fluorescence spectrum in toluene clearly shows a mirror image for the UV-vis absorption spectrum as depicted in Fig. 5a. Therefore, components A, B, and C are attributed to the S1,0/S0,0, S1,0/S0,1, and S1,0/S0,2 transitions, respectively. Fig. 5b depicts the fluorescence spectrum of 16d in the solid state. The wave deconvolution analyses also indicated three components A, B, and C, being similar to those in solution. It is concluded that the fluorescence spectrum of 16d in the solid state contains three components assigned to the S1,0/S0,0, S1,0/S0,1, and S1,0/S0,2 transitions.
Fig. 5. Wave deconvolution of fluorescence spectrum of 16d. (a) in toluene and (b) in the solid state.
Fig. 6. X-ray structure of 16b.
Fig. 7 indicates the X-ray structure of 16c. A pair of dimers are arranged in a herring-bone fashion (overview (1)). A cationic fluorophore has short contacts with one of the sulfonate-oxygen atoms and one of the trifluoromethyl-fluorine atoms of trifluoromethanesulfonate with 3.52 and 3.59 A, respectively (overview (2)). Molecules A, B, and C are arranged in parallel (side view (1)). CH/p interactions are observed between B and D with the tilt angle of 60 (side view (2)). The same result is observed for B and E (side view (3)). p/p Interactions are observed between A and B at the indolenium ring with the interplanar distance of 3.46 A (top view (1) and side view (4)), being slightly shorter than that of 16b (3.62 A). Two CH/p interactions are observed between B and C with 3.56 A (side view (5)). The interplanar distance between B and C is 4.80 A. The packing motif of 16c is similar to that of 16b. Thus, compound 16c also has isolated dimer-type packing.
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oxygen atoms and conjugated methine moiety and another one between one of the trifluoromethyl-fluorine atoms and the NA, respectively. Molecules B and C methyl-carbon with 3.32 and 3.18 are arranged in parallel and have weak p/p interactions between the indolenium moieties with interplanar distance of 3.74 A (top view (1) and side view (2)). Molecules A and B are not arranged in parallel, the tilt angle being 21 (side view (3)). p/p interactions as well as CH/p interactions (3.65 A) are observed at the indolenium moieties with interplanar distance of 3.60 A (top view (2) and side view (3)). The same results are observed for C and D (top view (3) and side view (4)). Thus, consequent p/p stacking is observed for 14d. The X-ray structure of 16d is shown in Fig. 9. Molecules are arranged in a zigzag form (overview (1)). A cationic fluorophore has two short contacts with a bis(trifluoromethylsulfonyl)imide anion, the distance being 3.50 and 3.51 A, respectively (overview (2)). The tilt angle between A and B is 4 (side view (1)). That between B and C is also 4 . The interplanar distance between A and B and A00 and B are 4.64 and 4.41 A, respectively (side view (2)). These lengths are too long to have p/p interactions. The same results are observed among B, C, and C00 (top view (2) and side view (3)). In the case of 16d, the long axis of the bis(trifluoromethylsulfonyl)imide anion molecule are aligned almost perpendicular to the long axis of the cationic cyanine fluorophore to inhibit p/p interactions between the fluorophores. Thus, compound 16d has isolated monomer-type packing.
Fig. 7. X-ray structure of 16c.
The X-ray structure of 14d is shown in Fig. 8. Molecules form a pair of dimers and are arranged in a zigzag form. A cationic fluorophore has two short contacts with bis(trifluoromethylsulfonyl) imide anion (overview (2)). One is between one of the sulfonyl-
Fig. 9. X-ray structure of 16d.
Fig. 8. X-ray structure of 14d.
There are two factors affecting the solid-state fluorescence intensity: melting point and packing motif. When the melting point is low, the stretching, vibration, and rotation processes of the molecule can occur to reduce the fluorescence intensity.9,11 The Ff of bis(perfluorobutylsulfonyl)imide derivative 16e (0.02) and N-octyl derivative 18d (0.02) are low. The melting points of 16e (80e82 C) and 18d (81e83 C) are significantly low compared with those of
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the other derivatives (170e171 to 260e262 C). Thus, low Ff of 16e and 18d can come from their low melting point. Coulomb forces are inversely proportional to the square of the distance between the cationic and anionic species. The short contact lengths between the cationic fluorophore and the anion species in 16c and 16d are 3.52 and 3.51 A, respectively, being similar. Nevertheless, the Ff of 16d (0.31) is significantly larger than that of 16c (0.06). Thus, no clear relationship between the short contact length and Ff is observed. In the case of neutral compounds, the consequent p/p stacking and intermolecular hydrogen bonds could reduce the solid-state fluorescence intensity.12 Compound 14d (Ff¼0.03) has consequent p/p stacking. Compounds 16b (Ff¼0.03) and 16c (Ff¼0.06) have isolated dimer-type packing with p/p interactions. Compound 16d (Ff¼0.31) has isolated monomer-type packing. It is concluded that the cyanine dyes having the least p/p interactions among adjacent cationic fluorophores could exhibit the most intense fluorescence in the solid-state. 3. Conclusion The solid-state fluorescence properties of indolenium carbocyanine dyes were examined. The cyanine dyes showed Fmax at around 660 nm in the solid state. The fluorescence intensity depended on both the counter anion and alkyl substituents on the indolenium nitrogen atoms. 1,10 -Dipropyl-3,3,30 3’-tetramethylindocarbocyanine bis(trifluoromethyl-sulfonyl)imide 16d exhibited the most intense fluorescence (Ff¼0.31) at Fmax 657 nm with shoulder peaks. The wave deconvolution indicated that S1,0/S0,0, S1,0/S0,1, and S1,0/S0,2 transitions were contained in the fluorescence spectrum. The X-ray crystallography suggests that the most intense fluorescence of 16d in the solid state can come from the isolated monomer-type packing, having the least p/p interactions among adjacent cationic fluorophores. Even in the case of cationic fluorophores, not Coulomb forces but the p/p interactions could reduce the fluorescence intensity in the solid state. 4. Experimental 4.1. Instruments Melting points were measured with a Yanagimoto MP-S2 micromelting-point apparatus. IR spectra were taken by a Shimadzu Affinity-1 spectrophotometer. NMR spectra were obtained by a JEOL ECX 400P spectrometer. MS spectra were measured with a JEOL MStation 700 spectrometer. Elemental analysis was performed with a Yanaco MT-6 CHN corder. UV-Vis absorption and fluorescence spectra were taken on Hitachi U-3500 and JASCO FP8600 spectrophotometers, respectively. 4.2. Materials 2,3,3-Trimethylindolenine (1), 1-propyl bromide (4), 1-propyl iodide (5), 1-butyl iodide (6), 1-octyl iodide (7), and triethoxymethane (13) were purchased from Tokyo Kasei Co., Ltd. Methyl iodide(2) was purchased from Nacalai Tesque Co., Ltd. Ethyl iodide (3), lithium bis(trifluoromethylsulfonyl)imide (19d) and lithium bis(1,1,2,2,3,3,4,4,4-nonafluoro-1-butanesulfonyl)imide (19e) were purchased from Wako Pure Chemical Industries. Lithium trifluoromethanesulfonate (19c) was purchased from Aldrich Chem. Co., Ltd. 1-Alkyl-2,3,3-trimethyl-3H-indolenium halides 8b, 9b, 10a, 10b, 11b, and 12b were prepared by the reaction of 1 with alkyl halides. Cyanine dyes 14b,13 15b,14 and 17b15 were prepared as described in the literature.
4.3. Synthesis of 3,3,30 30 -tetramethyl-1,10 -dialkylindocarbocyanine halides 16a, 16b, and 18b To a pyridine solution (10 mL) of 1-alkyl-2,3,3-trimethyl-3Hindolenium halides 10a, 10b, and 12b (6 mmol) was added triethoxymethane (13, 0.534 g, 3.6 mmol). The mixture was refluxed for 6 h. After the reaction was completed, to the mixture were added water (20 mL) and dichloromethane (50 mL). The dichloromethane layer was separated, washed with water (50 mL3), and dried over anhydrous sodium sulfate. The solvent was removed in vacuo. The resulting precipitate was washed with hexane. The product was purified by silica gel column chromatography (CH2Cl2 then CH2Cl2eMeOH¼10:1) and recrystallized from ethanol. 4.3.1. 1,10 -Dipropyl-3,3,30 30 -tetramethylindocarbocyanine bromide (16). Yield 68%; mp 255257 C; IR (KBr) n 1556 cm1; 1H NMR (CDCl3) d¼1.15 (t, J¼7.4 Hz, 6H), 1.72 (s, 12H), 1.96 (sex, J¼7.4 Hz, 4H), 4.26 (t, J¼7.4 Hz, 4H), 7.12 (d, J¼7.8 Hz, 2H), 7.24 (t, J¼7.8 Hz, 2H), 7.38 (d, J¼7.8 Hz, 2H), 7.39 (t, J¼7.8 Hz, 2H), 7.48 (d, J¼13.5 Hz, 2H), 8.46 (t, J¼13.5 Hz, 1H); 13C NMR (CDCl3) d¼11.5 (2C), 21.0 (2C), 28.1 (4C), 46.1 (2C), 48.8 (2C), 104.8 (2C), 110.9 (2C), 122.0 (2C), 125.0 (2C), 128.7 (2C), 140.5 (2C), 142.2 (2C), 150.7, 173.6 (2C); FABMS (NBA) m/z 413 (MþI); Anal. Found: C, 70.70, H, 7.63, N, 5.59%, Calcd for C29H37BrN2: C, 70.58; H, 7.56; N, 5.68%. iodide 4.3.2. 1,10 -Dipropyl-3,3,30 30 -tetramethylindocarbocyanine (16b). Yield 71%; mp 260e262 C; IR (KBr) n 1559 cm1; 1H NMR(CDCl3) d¼1.17 (t, J¼7.4 Hz, 6H), 1.74 (s, 12H), 1.95 (sex, J¼7.4 Hz, 4H), 4.26 (t, J¼7.4 Hz, 4H), 7.13 (d, J¼7.8 Hz, 2H), 7.25 (t, J¼7.8 Hz, 2H), 7.37 (d, J¼7.8 Hz, 2H), 7.39 (t, J¼7.8 Hz, 2H), 7.52 (d, J¼13.5 Hz, 2H), 8.45 (t, J¼13.5 Hz, 1H); 13C NMR (CDCl3) d¼11.8 (2C), 21.2 (2C), 28.3 (4C), 46.4 (2C), 49.0 (2C), 104.9 (2C), 111.1 (2C), 122.2 (2C), 125.3 (2C), 128.9 (2C), 140.8 (2C), 142.4 (2C), 150.9, 173.8 (2C); FABMS (NBA) m/z 413 (MþI); Anal. Found: C, 64.57, H, 6.99, N, 5.34%, Calcd for C29H37IN2: C, 64.44; H, 6.90; N, 5.18%. 4.3.3. 1,10 -Dioctyl-3,3,30 30 -tetramethylindocarbocyanine iodide (18b). Yield 67%; mp 86e88 C; IR (KBr) n 1559 cm1; 1H NMR (CDCl3) d¼0.86 (t, J¼7.4 Hz, 6H), 1.22e1.40 (m, 16H), 1.56 (quin, J¼7.4 Hz, 4H), 1.71 (s, 12H), 1.88 (quin, J¼7.4 Hz, 4H), 4.28 (t, J¼7.4 Hz, 4H), 7.11 (d, J¼7.8 Hz, 2H), 7.24 (t, J¼7.8 Hz, 2H), 7.36 (d, J¼7.8 Hz, 2H), 7.37 (t, J¼7.8 Hz, 2H), 7.46 (d, J¼13.6 Hz, 2H), 8.44 (t, J¼13.6 Hz, 1H); 13C NMR (CDCl3) d¼14.1 (2C), 22.6 (2C), 27.0 (2C), 27.7 (2C), 28.1 (4C), 29.1 (2C), 29.5 (2C), 31.8 (2C), 45.1 (2C), 48.8 (2C), 104.9 (2C), 111.0 (2C), 122.0 (2C), 125.0 (2C), 128.8 (2C), 140.7 (2C), 142.4 (2C), 150.8, 173.4 (2C); FABMS (NBA) m/z 553 (MþI); Anal. Found: C, 68.98, H, 8.56, N, 4.10%, Calcd for C39H57IN2: C, 68.81; H, 8.44; N, 4.11%. 4.4. Synthesis of 1,10 -dialkyl-3,3,30 30 -tetramethylindocarbocyanine dyes 14d, 15d, 16c, 16d, 16e, 17d, and 18d To an acetoneewater (1:1 vol, 10 mL) mixed solution of 1,10 dialkyl-3,3,30 30 -tetramethylindocarbocyanine iodides 14b, 15b, 16b, 17b, and 18b (0.5 mmol) was added lithium salts 19c, 19d, and 19d (0.6 mmol). The mixture was stirred at room temperature for 6 h. After the reaction was completed, to the mixture were added water (20 mL) and dichloromethane (50 mL). The dichloromethane layer was separated, washed with water (50 mL3), and dried over anhydrous sodium sulfate. The solvent was removed in vacuo. The product was purified by alumina column chromatography (CH2Cl2 then CH2Cl2eAcOEt¼20:1) and recrystallized from ethanol. 4.4.1. 1,10,3,3,30 30 -Hexamethylindocarbocyanine bis(trifluoromethylsulfonyl)imide (14d). Yield 86%; mp 132e133 C; IR (KBr) n 1562, 1354 cm1; 1H NMR(CDCl3) d¼1.73 (s, 12H), 3.66 (s,
M. Matsui et al. / Tetrahedron 71 (2015) 3528e3534
6H), 6.49 (d, J¼13.2 Hz, 2H), 7.14 (d, J¼7.7 Hz, 2H), 7.27 (t, J¼7.7 Hz, 2H), 7.37 (d, J¼7.7 Hz, 2H), 7.40 (t, J¼7.7 Hz, 2H), 8.43 (t, J¼13.2 Hz, 1H); 19F NMR (CDCl3) d¼78.5; 13C NMR (CDCl3) d¼28.1 (4C), 31.5 (2C), 49.2 (2C), 104.0 (2C), 110.9 (2C), 120.1 (q, J¼320 Hz, 2C), 122.2 (2C), 125.7 (2C), 129.0 (2C), 140.5 (2C), 142.7 (2C), 150.7, 174.8 (2C); FABMS (NBA) m/z 357 (Mþ(CF3SO2)2N); Anal. Found: C, 50.94; H, 4.66; N, 6.54%. Calcd For C27H29F6N3O4S2: C, 50.86; H, 4.58; N, 6.59%. 4.4.2. 1,10 -Diethyl-3,3,30 30 -tetramethylindocarbocyanine bis(trifluoromethylsulfonyl)imide (15d). Yield 87%; mp 170e172 C; IR (KBr) n 1559, 1354 cm1; 1H NMR(CDCl3) d¼1.45 (t, J¼7.2 Hz, 6H), 1.73 (s, 12H), 4.16 (q, J¼7.2 Hz, 4H), 6.44 (d, J¼13.4 Hz, 2H), 7.14 (d, J¼7.8 Hz, 2H), 7.28 (t, J¼7.8 Hz, 2H), 7.38 (d, J¼7.8 Hz, 2H), 7.41 (t, J¼7.8 Hz, 2H), 8.41 (t, J¼13.4 Hz, 1H); 19F NMR (CDCl3) d¼78.5; 13C NMR (CDCl3) d¼12.3 (2C), 28.0 (4C), 39.5 (2C), 49.2 (2C), 102.9 (2C), 110.7 (2C), 120.0 (q, J¼320 Hz, 2C), 122.3 (2C), 125.6 (2C), 128.9 (2C), 140.7 (2C), 141.5 (2C), 150.7, 173.7 (2C); FABMS (NBA) m/z 385 (Mþ(CF3SO2)2N); Anal. Found: C, 52.14; H, 5.01; N, 6.21%. Calcd for C29H33F6N3O4S2: C, 52.32; H, 5.00; N, 6.31%. tri4.4.3. 1,10 -Dipropyl-3,3,30 30 -tetramethylindocarbocyanine fluoromethanesulfonate (16c). Yield 75%; mp 201e202 C; IR (KBr) n 1559, 1354 cm1; 1H NMR (CDCl3) d¼1.09 (t, J¼7.3 Hz, 6H), 1.73 (s 12H), 1.92 (sex, J¼7.3 Hz, 4H), 4.16 (t, J¼7.3 Hz, 4H), 6.84 (d, J¼13.3 Hz, 2H), 7.12 (d, J¼7.8 Hz, 2H), 7.24 (t, J¼7.8 Hz, 2H), 7.37 (d, J¼7.8 Hz, 2H), 7.40 (t, J¼7.8 Hz, 2H), 8.41 (t, J¼13.3 Hz, 1H); 19F NMR (CDCl3) d¼78.0; 13C NMR (CDCl3) d¼11.3 (2C), 21.0 (2C), 28.2 (4C), 45.9 (2C), 49.3 (2C), 103.6 (2C), 111.1 (2C), 121.1 (q, J¼320 Hz), 122.4 (2C), 125.4 (2C), 128.9 (2C), 140.7 (2C), 142.2 (2C), 150.9, 174.3 (2C); FABMS (NBA) m/z 413 (MþCF3SO3); Anal. Found: C, 63.65; H, 6.59; N, 4.87%. Calcd for C30H37F3N2O3S: C, 64.04; H, 6.63; N, 4.98%. 4.4.4. 1,10 -Dipropyl-3,3,30 30 -tetramethylindocarbocyanine bis(trifluoromethylsulfonyl)imide (16d). Yield 78%; mp 203e204 C; IR (KBr) n 1558, 1354 cm1; 1H NMR(CDCl3) d¼1.06 (t, J¼7.3 Hz, 6H), 1.74 (s, 12H), 1.90 (sex, J¼7.3 Hz, 4H), 4.09 (t, J¼7.3 Hz, 4H), 6.46 (d, J¼13.3 Hz, 2H), 7.13 (d, J¼7.8 Hz, 2H), 7.26 (t, J¼7.8 Hz, 2H), 7.38 (d, J¼7.8 Hz, 2H), 7.40 (t, J¼7.8 Hz, 2H), 8.42 (t, J¼13.3 Hz, 1H); 19F NMR (CDCl3) d¼78.5; 13C NMR (CDCl3) d¼11.3 (2C), 20.9 (2C), 28.2 (4C), 45.9 (2C), 49.4 (2C), 103.1 (2C), 111.2 (2C), 120.1 (q, J¼320 Hz, 2C), 122.4 (2C), 125.7 (2C), 129.0 (2C), 140.7 (2C), 142.2 (2C), 150.7, 174.4 (2C); FABMS (NBA) m/z 413 (Mþ(CF3SO2)2N); Anal. Found: C, 53.65; H, 5.24; N, 6.16%. Calcd for C31H37F6N3O4S2: C, 53.67; H, 5.38; N, 6.06%. 4.4.5. 1,10 -Dipropyl-3,3,30 30 -tetramethylindocarbocyanine bis(perfluorobutylsulfonyl)imide (16e). Yield 85%; mp 80e82 C; IR (KBr) n 1556, 1357 cm1; 1H NMR (CDCl3) d¼1.06 (t, J¼7.3 Hz, 6H), 1.75 (s 12H), 1.89 (sex, J¼7.3 Hz, 4H), 4.07 (t, J¼7.3 Hz, 4H), 6.36 (d, J¼13.3 Hz, 2H), 7.14 (d, J¼7.8 Hz, 2H), 7.27 (t, J¼7.8 Hz, 2H), 7.40 (d, J¼7.8 Hz, 2H), 7.42 (t, J¼7.8 Hz, 2H), 8.45 (t, J¼13.3 Hz, 1H); 19F NMR (CDCl3) d¼80.7, 112.6, 120.9, 125.8; FABMS (NBA) m/z 413 (Mþ(C4F9SO2)2N); Anal. Found: C, 45.05; H, 3.65; N, 3.97%. Calcd for C37H37F18N3O4S2: C, 44.72; H, 3.75; N, 4.23%. bis(tri4.4.6. 1,10 -Dibutyl-3,3,30 30 -tetramethylindocarbocyanine fluoromethylsulfonyl)imide (17d). Yield 65%; mp 170e171 C; IR (KBr) n 1554, 1350 cm1; 1H NMR(CDCl3) d¼1.00 (t, J¼7.6 Hz, 6H), 1.49 (sex, J¼7.6 Hz, 4H), 1.73 (s, 12H), 1.82 (quin, J¼7.6 Hz, 4H), 4.10 (t, J¼7.6 Hz, 4H), 6.37 (d, J¼13.6 Hz, 2H), 7.13 (d, J¼7.7 Hz, 2H), 7.28 (t, J¼7.7 Hz, 2H), 7.38 (d, J¼7.7 Hz, 2H), 7.40 (t, J¼7.7 Hz, 2H), 8.43 (t, J¼13.6 Hz, 1H); 19F NMR (CDCl3) d¼78.5; 13C NMR (CDCl3) d¼13.9 (2C), 20.2 (2C), 28.1 (4C), 29.6 (2C), 44.5 (2C), 49.4 (2C), 103.0 (2C), 111.1 (2C), 120.1 (q, J¼319 Hz, 2C), 122.3 (2C), 125.7 (2C), 129.0 (2C), 140.7 (2C), 142.1 (2C), 150.7, 174.3 (2C); FABMS (NBA) m/z 441
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(Mþ(CF3SO2)2N); Anal. Found C, 54.67; H, 5.69; N, 5.75%. Calcd for C33H41F6N3O4S2: C, 54.91; H, 5.73; N, 5.82%. 4.4.7. 1,10 -Dioctyl-3,3,30 30 -tetramethylindocarbocyanine bis(trifluoromethylsulfonyl)imide (18d). Yield 80%; mp 81e83 C; IR (KBr) n 1556, 1354 cm1; 1H NMR (CDCl3) d¼0.86 (t, J¼7.1 Hz, 6H), 1.24e1.39 (m, 16H), 1.45 (quin, J¼7.1 Hz, 4H), 1.74 (s, 12H), 1.83 (quin, J¼7.1 Hz, 4H), 4.10 (t, J¼7.1 Hz, 4H), 6.39 (d, J¼13.6 Hz, 2H), 7.12 (d, J¼7.9 Hz, 2H), 7.27 (t, J¼7.9 Hz, 2H), 7.39 (d, J¼7.9 Hz, 2H), 7.40 (t, J¼7.9 Hz, 2H), 8.42 (t, J¼13.6 Hz, 1H); 19F NMR (CDCl3) d¼78.5; 13C NMR (CDCl3) d¼14.1 (2C), 22.7 (2C), 26.9 (2C), 27.6 (2C), 28.1 (4C), 29.1 (2C), 29.4 (2C), 31.8 (2C), 44.6 (2C), 49.3 (2C), 103.2 (2C), 111.2 (2C), 120.1 (q, J¼320 Hz, 2C), 122.3 (2C), 125.6 (2C), 129.0 (2C), 140.7 (2C), 142.2 (2C), 150.6, 174.2 (2C); FABMS (NBA) m/z 553 (Mþ(CF3SO2)2N); Anal. Found: C, 59.38; H, 6.94; N, 5.04%. Calcd for C41H57F6N3O4S2: C, 59.04; H, 6.89; N, 5.04%. 4.5. X-ray crystallographic analysis Single crystals were obtained by diffusion method using dichloromethane and hexane. The diffraction data were collected by using graphite monochromated Mo-Ka radiation (l¼0.71069 A). The structure was solved by direct methods SIR97 and refined by fill-matrix least-squares calculations. 4.5.1. Crystal data for 14d. C27H29F6N3O4S2, Mw¼637.65, orthorhombic, P212121, Z¼4, a¼11.713(4), b¼15.106(5), c¼16.252(5) A, Dcalcd¼1.473 g cm3, T¼123 K, 23,725 reflections were corrected, 6568 unique (Rint¼0.0558), 385 parameters, R1¼0.0508, wR2¼0.0890, G.O.F 1.096, CCDC (724452). 4.5.2. Crystal data for 16b. C29H37IN2, Mw¼540.51, monoclinic, P21/ c, Z¼4, a¼10.4987(16), b¼18.633(3), c¼16.604(1) A, b¼107.509(7), Dcalcd¼1.159 g cm3, T¼293 K, 31,523 reflections were corrected, 7035 unique (Rint¼0.0544), 290 parameters, R1¼0.1226, wR2¼0.3749, G.O.F 1.246. CDCC (963762). 4.5.3. Crystal data for 16c. C30H37F3N2O3S, Mw¼562.68, monoclinic, P21/c, Z¼4, a¼10.5524(17), b¼18.3636(19), c¼16.716(2) A, b¼106.965(6), Dcalcd¼1.206 g cm3, T¼293 K, 31,761 reflections were corrected, 7066 unique (Rint¼0.0402), 290 parameters, R1¼0.0999, wR2¼0.2883, G.O.F 1.021. CDCC (963763). 4.5.4. Crystal data for 16d. C31H37F6N3O4S2, Mw¼693.76, monoclinic, P21/n, Z¼8, a¼9.852(2), b¼20.888(3), c¼33.913(5) A, Dcalcd¼1.321 g cm3, T¼293(2) K, 66,349 reflections were corrected, 7968 unique (Rint¼0.1150), 421 parameters, R1¼0.1185, wR2¼0.3211, G.O.F 1.144. CDCC (963764). Supplementary data UVevis absorption and fluorescence spectra of 16d in various solvents, 1H spectra of 14b, 14d, 15b, 15d, 16a, 16b, 16c, 16d, 16e, 17b, 17d, 18b, and 18d, single X-ray data for 14d, 16b, 16c, and 16d. This material is available free of charge via internet. Supplementary data related to this article can be found at http://dx.doi.org/10.1016/ j.tet.2015.03.027. References and notes 1. (a) Haugland, R. Handbook of Fluorescent Probes and Research Chemicals, 8th ed.; Molecular Probes: Eugene, OR, 2001; (b) Galbraith, E.; James, T. D. Chem. Soc. Rev. 2010, 39, 3831e3842. 2. Nakazumi, H. J. Soc. Dye. Colour. 1988, 104, 121e125. 3. Chang, Y.-J.; Chow, T. J. J. Mater. Chem. 2011, 21, 3091e3099. 4. (a) Funabiki, K.; Mase, H.; Hibino, A.; Tanaka, N.; Mizuhata, N.; Sakuragi, Y.; Nakashima, A.; Yoshida, T.; Kubota, Y.; Matsui, M. Energy Environ. Sci. 2011, 4,
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2186e2192; (b) Maeda, T.; Mineda, S.; Fujiwara, H.; Nakao, H.; Yagi, S.; Nakazumi, H. J. Mater. Chem. A 2013, 1, 1303e1309. 5. (a) Ooyama, Y.; Matsugasako, A.; Hagiwara, Y.; Ohshita, J.; Harima, Y. Eur. J. Org. J.; Burschka, C.; Wu z, A. €rthner, F. Chem. 2012, 4853e4859; (b) Lin, M.-J.; Jimene Chem. Commun. 2012, 12050e12052; (c) Anthony, S. P. ChemPlusChem 2012, 77, 518e531; (d) Shimizu, M.; Takeda, Y.; Higashi, M.; Hiyama, T. Angew. Chem., Int. Ed. 2009, 48, 3653e3656; (e) Langhals, H.; Krotz, O.; Polborn, K.; Mayer, P. Angew. Chem., Int. Ed. 2005, 44, 2427e2428; (f) Fei, Z.; Kocher, N.; Mohrschladt, C. J.; Ihmels, H.; Stalke, D. Angew. Chem., Int. Ed. 2003, 42, 783e787. 6. (a) Hinoue, T.; Shigenori, Y.; Sugino, M.; Mizobe, Y.; Hisaki, I.; Miyata, M.; Tohtani, N. Chem.dEur. J. 2012, 18, 4634e4643; (b) Mizobe, Y.; Hinoue, T.; Yamamoto, A.; Hisaki, I.; Miyata, M.; Hasegawa, Y.; Tohnai, N. Chem.dEur. J. 2009, 15, 8175e8184; (c) Hinoue, T.; Mizobe, Y.; Hisaki, I.; Miyata, M.; Tohnai, N. Chem. Lett. 2008, 37, 642e643; (d) Mizobe, Y.; Hinoue, T.; Miyata, M.; Hisaki, I.; Hasegawa, Y.; Tohnai, N. Bull. Chem. Soc. Jpn. 2007, 80, 1162e1172; (e) Mizobe, Y.; Miyata, M.; Hisaki, I.; Hasegawa, Y.; Tohnai, N. Org. Lett. 2006, 8, 4295e4298; (f) Mizobe, Y.; Ito, H.; Hisaki, I.; Miyata, M.; Hasegawa, Y.; Tohnai, N. Chem. Commun. 2006, 2126e2128; (g) Mizobe, Y.; Tohnai, N.; Miyata, M.; Hasegawa, Y. Chem. Commun. 2005, 1839e1841; (h) Yamamoto, A.; Matsumoto, M.; Hinoue, T.; Mizobe, Y.; Hisaki, I.; Miyata, M.; Tohnai, N. Synth. Met. 2009, 159, 905e909; (i) Mizobe, Y.; Miyata, M.; Hisaki, I.; Tohnai, N. Chem. Lett. 2007, 36, 280e281.
7. Marwitz, A. J. V.; Jenkins, J. T.; Zakharov, L. N.; Liu, S.-Y. Angew. Chem., Int. Ed. 2010, 49, 7444e7447. 8. Ooyama, Y.; Oda, Y.; Hagiwara, Y.; Fukuoka, H.; Miyazaki, E.; Mizomo, T.; Ohshita, J. Tetrahedron 2013, 69, 5818e5822. 9. Matsui, M.; Ooiwa, K.; Okada, A.; Kubota, Y.; Funabiki, K.; Sato, H. Dyes Pigm. 2013, 99, 916e923. 10. (a) Kudo, K.; Momotake, A.; Kanna, Y.; Nishimura, Y.; Arai, T. Chem. Commun. 2011, 3867e3869; (b) Bondarev, S. L.; Tikhomirov, S. A.; Knyukshto, V. N.; Turban, A. A.; shchenko, A. A.; Kulinich, A. V.; Ledoux, I. J. Lumin. 2007, 124, 178e186; (c) Kubota, Y.; Sakuma, Y.; Funabiki, K.; Matsui, M. J. Phys. Chem. A 2014, 118, 8717e8729. 11. An, P.; Shi, Z.-F.; Dou, W.; Cao, X.-P.; Zhang, H.-L. Org. Lett. 2010, 12, 4364e4367. 12. (a) Matsui, M.; Ikeda, R.; Kubota, Y.; Funabiki, K. Tetrahedron Lett. 2009, 50, 5047e5049; (b) Kubota, Y.; Uehara, J.; Funabiki, K.; Ebihara, M.; Matsui, M. Tetrahedron Lett. 2010, 51, 6195e6198; (c) Ooyama, Y.; Nabeshima, S.; Mamura, T.; Ooyama, H. E.; Yoshida, K. Tetrahedron 2010, 66, 7954e7960; (d) Shirai, K.; Matsuoka, M.; Fukunishi, K. Dyes Pigm. 1999, 42, 95e101. 13. Fedyunyayava, I. A.; Klochko, O. P.; Semenova, O. M.; Khabuseva, S. U.; Povrozin, Y. A.; Sokolyk, O. O.; Stepanenko, O. U.; Terpetschnig, E. A. Dyes Pigm. 2011, 90, 201e210. 14. EI-Schishtawy, R. M.; Almeida, P. Tetrahedron 2006, 62, 7793e7798. 15. Sauerwein, B.; Schuster, G. B. J. Phys. Chem. 1991, 95, 1903e1906.
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Fluorescence properties of indolenium carbocyanine dyes in solid state M. Matsui *, S. Ando, M. Fukushima, T. Shibata, Y. Kubota, K. Funabiki Faculty of Engineering, Gifu University, 1-1 Yanagido, Gifu 501-1193, Japan
a r t i c l e i n f o
a b s t r a c t
Article history: Received 3 February 2015 Received in revised form 5 March 2015 Accepted 6 March 2015 Available online 27 March 2015
The fluorescence intensity of indolenium carbocyanine dyes in the solid state depended on both the alkyl group on the nitrogen atoms in the indolenium rings and the kind of counter anions. The N-propyl derivative having a bis(trifluoromethylsulfonyl)imide anion, whose fluorescence maximum was observed at 657 nm with shoulder peaks, exhibited the highest fluorescence quantum yield of 0.31. The wave deconvolution of fluorescence spectrum indicated three components assigned to the S1,0/S0,0, S1,0/S0,1, and S1,0/S0,2 transitions. The X-ray structure of this compound indicates an isolated monomer-type packing, whereas the other derivatives shows the isolated dimer-type packing or consequent p/p stacking. The cyanine dye having the least p/p interactions among adjacent cationic fluorophores could exhibit the most intense fluorescence in the solid state. Ó 2015 Elsevier Ltd. All rights reserved.
Keywords: Fluorescence spectrum Indolenium carbocyanine dye Solid state Single X-ray structure Wave deconvolution
1. Introduction Cyanine dyes cover the wide range of absorption band from visible to near-infrared region. They have been used as probes,1 information recording materials,2 emitters,3 and sensitizers.4 Cyanine dye are one of the classical fluorescent dyes. Organic fluorescent dyes are classified into three types: neutral, anionic, and cationic derivatives. Among these types, a number of neutral solidstate fluorescent compounds have been reported.5 For the anionic derivatives, the relationship between the emission spectra and Xray structure of arylsulfonates have been reported.6 For cationic dyes, only the solid-state fluorescence of 1,2-azaborine cations,7 pyridinium dyes,8 and styryl dyes9 have been reported. To our knowledge, no detailed studies on the solid-state fluorescence of cationic cyanine dyes has been reported so far. We report herein the solid-state fluorescence of indolenium carbocyanine dyes.
were treated with lithium salts 19c, 19d, and 19e to afford the corresponding anion-exchanged derivatives 14d, 15d, 16c, 16d, 16e, 17d, and 18d.
2. Results and discussion 2.1. Synthesis The synthesis of indolenium carbocyanine dyes are shown in Scheme 1. 2,3,3-Trimethylindolenine (1) was N-alkylated with alkyl halides 2e7 to give 1-alkyl-2,3,3-trimethyl-3H-indolenium halides 8e12, which were further allowed to react with triethoxymethane (13) to produce 14b, 15b, 16a, 16b, 17b, and 18b. These compounds * Corresponding author. Tel.: þ81 58 293 2601; fax: þ81 58 293 2794; e-mail address: [email protected] (M. Matsui). http://dx.doi.org/10.1016/j.tet.2015.03.027 0040-4020/Ó 2015 Elsevier Ltd. All rights reserved.
Scheme 1. Reagents and conditions: i) 1 (1.0 equiv), 2e7 (3.3 equiv), MeCN, reflux, 1e2 d, ii) 8e12 (1.0 equiv), 13 (0.6 equiv), pyridine, reflux, 6 h, iii) 14b, 15b, 16a, 16b, 17b, and 18b (1.0 equiv), 19 (1.2 equiv), acetoneewater, rt, 6 h.
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2.2. UVevis absorption and fluorescence spectra The UVevis absorption and fluorescence spectra of cyanine dyes in solution are shown in Fig. 1. Fig. 1a shows the effect of counter anion on the UVevis absorption and fluorescence spectra. Two absorption maxima (lmax) were observed at around 560 and 525 nm with a small shoulder peak at around 490 nm. The molar absorption coefficients (ε) were calculated in the range of 144,000 to 151,000 and 68,400 to 77,800 dm3 mol1 cm1, respectively. No remarkable differences in the UVevis absorption band were observed among 16a, 16b, 16c, 16d, and 16e. They showed the fluorescence maxima (Fmax) at around 575 and 620 nm with a shoulder peak at around 680 nm. The fluorescence quantum yield (Ff) was in the range of 0.04e0.20. The Stokes shift was very small, being ca. 15 nm.
Fig. 1. UVevis absorption and fluorescence spectra of indolenium carbocyanine dyes (1.0106 mol dm3) in toluene. Solid and dotted lines represents the fluorescence and UVevis absorption spectra, respectively. (a) N-propyl derivatives 16a, 16b, 16c, 16d, and 16e and (b) bis(trifluoromethylsulfonyl)imide derivatives 14d, 15d, 16d, 17d, and 18d.
Fig. 1b shows the effect of alkyl group on the UVevis absorption and fluorescence spectra. No marked differences in the UVevis absorption and fluorescence spectra were observed among 14d, 15d, 16d, 17d, and 18d. They also showed Fmax at around 575 and 620 nm with a shoulder peak at around 680 nm. The Ff was observed in the range of 0.07e0.14. Fig. 2 shows the fluorescence spectra in the solid state. The compounds were recrystallized from ethanol. The effect of the counter anion on the fluorescence spectrum is shown in Fig. 2a. The Fmax was observed at around 660 nm, being red-shifted compared with those in solution due to the intermolecular interactions in the solid state. A shoulder peak was also observed at around 690 nm. The fluorescence of bis(trifluoromethylsulfonyl)imide derivative (16d, Ff¼0.31) was remarkably intense compared with the bromide
Fig. 2. Fluorescence spectra of indolenium carbocyanine dyes in the solid state. Solid and dotted lines represents the fluorescence and excitation spectra, respectively. (a) Npropyl derivatives 16a, 16b, 16c, 16d, and 16e and (b) bis(trifluoromethylsulfonyl)imide derivatives 14d, 15d, 16d, 17d, and 18d.
(16a, Ff¼0.03), iodide (16b, Ff¼0.03), trifluoromethanesulfonate (16c, Ff¼0.06), and bis(perfluorpbutylsulfonyl)imide (16e, Ff¼0.02) derivatives. The effect of alkyl group on the solid-state fluorescence spectrum is indicated in Fig. 2b. The Fmax was observed at around 660 nm with a shoulder peak at around 690 nm. The fluorescence was more intense in the order of the alkyl group: Pr (16d, Ff¼0.31)>Et (15d, Ff¼0.19), Bu (17d, Ff¼0.17)>Me (14d, Ff¼0.03), Oct (18d, Ff¼0.02). Interestingly, compounds 15d, 16d, and 17d exhibited larger Ff value in the solid state than in toluene. The UVevis absorption and fluorescence spectra are also listed in Table 1. As the UVevis absorption spectra of cyanine dyes showed two absorption maxima with a shoulder peak, the wave deconvolution analyses of 16d, which showed the most intense fluorescence in the solid state, was performed using a Gaussian function. The result in solution is shown in Fig. 3. Fig. 3a shows that there are three components A0 , B0 , and C0 in the UVevis absorption band. Fig. 3b indicates the effect of concentration on the UVevis absorption spectrum of 16d. The normalized spectra were identical, indicating that the absorption peaks at 525 and 490 nm do not come from the dimers, oligomers and/or H-aggregates but from the monomer form. To assign the UVevis absorption band, the TDDFT calculations of 16d was performed. The results are shown in Fig. 4 and Table 2. The first and second absorption bands were predicted to be observed at 455 and 351 nm with the oscillator strengths of 1.27 and 0.01, respectively. Considering that the observed lmax at 560 nm is assigned to the S0/S1 transition, the observed lmax at 525 is too close to the first absorption band. Furthermore, the ε values at 525 nm (75,900) is too large to assign it to the S0 / S2 transition.
Table 1 UVevis absorption and fluorescence spectra of indolenium carbocyanine dyes Compd
Mp/ C
In toluenea
14d 15d 16a 16b 16c 16d 16e 17d 18d a b
132e133 170e172 255e257 260e262 201e202 203e204 80e82 170e171 81e83
524 523 525 528 526 525 526 525 526
(77,800), (77,000), (68,500), (68,700), (68,400), (75,900), (77,100), (76,700), (77,400),
Ff (solid)/Ff (toluene)
Solid state
lmax (ε)/nm 557 558 566 562 562 560 559 560 560
(146,000) (150,000) (147,000) (145,000) (144,000) (150,000) (151,000) (151,000) (151,000)
Measured at the concentration of 1.0 x 106 mol dm3. Measured by a Hamamatsu Photonics Quantaurus-QY instrument.
Fmax/nm
Ff b
lex/nm
Fmax/nm
Ff b
573 573 580 578 576 574 574 575 578
0.07 0.14 0.12 0.04 0.20 0.12 0.12 0.12 0.12
605 602 636 636 638 614 618 614 607
648 653 677 677 667 657 648 655 643
0.03 0.19 0.03 0.03 0.06 0.31 0.02 0.17 0.02
0.50 1.31 0.25 0.75 0.30 2.58 0.16 1.41 0.17
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2.3. X-ray crystallography
Fig. 3. UVevis absorption spectrum of 16d in toluene. (a) Wave deconvolution of UVevis absorption spectrum and (b) UVevis absorption spectra in different concentrations.
To understand why 16d exhibited the most intense fluorescence in the solid state, the X-ray crystallography of 16b, 16c, 14d, and 16d were performed. The X-ray structure of 16b is shown in Fig. 6. Molecules form a pair of head-to-tail dimers and are packed in a herring-bone fashion (overview (1)). A cationic fluorophore has Coulomb interactions with an iodine anion (overview (2)). The distance between the iodine anion and the cationic cyanine fluorophore is observed to be 4.07 A. Molecules A, B, and C are arranged in parallel (side view (1)). The tilt angle between B and D is 56 with CH/p interactions (side view (2)). The same result is observed for B and E (side view (3)). p/p Interactions are observed for A and B at the indolenium rings with interplanar distance of 3.62 A (top view (1) and side view (4)). Though two CH/p interactions are observed between B and C, the interplanar distance (4.93 A) is too long to have p/p interactions (top view (2) and side view (5)). Thus, 16b has isolated dimer-type packing.
Fig. 4. DFT calculations (B3LYP/6e31G(d,p)) for the cation of 16d.
Table 2 Excitation energies (eV, nm), main orbital transition, and oscillator strengths (f) for 16d calculated by TDDFT Transition
Ea (eV, nm)
Main orbital transitionb
f
lmax (ε)c/nm
S0/S1
2.73 (455)
HOMO to LUMO (0.71)
1.27
S0/S2
3.53 (351)
HOMO-1 to LUMO (0.68)
0.01
525 (75,900), 560 (150,000) d
a b c
Toluene was used as a solvent in the calculation. The coefficient of the wave function for each excitation is in absolute values. Observed lmax in toluene.
Therefore, components A0 , B0 , and C0 can be attributed to the transition comes from the vibration levels in the first transition, S0,0/S1,0, S0,0/S1,1, and S0,0/S1,2 transitions, respectively. The UVevis absorption bands come from the vibration level are observed in non-polar solvents.10 The wave deconvolution of the fluorescence spectrum of 16d is shown in Fig. 5. The fluorescence spectrum in toluene clearly shows a mirror image for the UV-vis absorption spectrum as depicted in Fig. 5a. Therefore, components A, B, and C are attributed to the S1,0/S0,0, S1,0/S0,1, and S1,0/S0,2 transitions, respectively. Fig. 5b depicts the fluorescence spectrum of 16d in the solid state. The wave deconvolution analyses also indicated three components A, B, and C, being similar to those in solution. It is concluded that the fluorescence spectrum of 16d in the solid state contains three components assigned to the S1,0/S0,0, S1,0/S0,1, and S1,0/S0,2 transitions.
Fig. 5. Wave deconvolution of fluorescence spectrum of 16d. (a) in toluene and (b) in the solid state.
Fig. 6. X-ray structure of 16b.
Fig. 7 indicates the X-ray structure of 16c. A pair of dimers are arranged in a herring-bone fashion (overview (1)). A cationic fluorophore has short contacts with one of the sulfonate-oxygen atoms and one of the trifluoromethyl-fluorine atoms of trifluoromethanesulfonate with 3.52 and 3.59 A, respectively (overview (2)). Molecules A, B, and C are arranged in parallel (side view (1)). CH/p interactions are observed between B and D with the tilt angle of 60 (side view (2)). The same result is observed for B and E (side view (3)). p/p Interactions are observed between A and B at the indolenium ring with the interplanar distance of 3.46 A (top view (1) and side view (4)), being slightly shorter than that of 16b (3.62 A). Two CH/p interactions are observed between B and C with 3.56 A (side view (5)). The interplanar distance between B and C is 4.80 A. The packing motif of 16c is similar to that of 16b. Thus, compound 16c also has isolated dimer-type packing.
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oxygen atoms and conjugated methine moiety and another one between one of the trifluoromethyl-fluorine atoms and the NA, respectively. Molecules B and C methyl-carbon with 3.32 and 3.18 are arranged in parallel and have weak p/p interactions between the indolenium moieties with interplanar distance of 3.74 A (top view (1) and side view (2)). Molecules A and B are not arranged in parallel, the tilt angle being 21 (side view (3)). p/p interactions as well as CH/p interactions (3.65 A) are observed at the indolenium moieties with interplanar distance of 3.60 A (top view (2) and side view (3)). The same results are observed for C and D (top view (3) and side view (4)). Thus, consequent p/p stacking is observed for 14d. The X-ray structure of 16d is shown in Fig. 9. Molecules are arranged in a zigzag form (overview (1)). A cationic fluorophore has two short contacts with a bis(trifluoromethylsulfonyl)imide anion, the distance being 3.50 and 3.51 A, respectively (overview (2)). The tilt angle between A and B is 4 (side view (1)). That between B and C is also 4 . The interplanar distance between A and B and A00 and B are 4.64 and 4.41 A, respectively (side view (2)). These lengths are too long to have p/p interactions. The same results are observed among B, C, and C00 (top view (2) and side view (3)). In the case of 16d, the long axis of the bis(trifluoromethylsulfonyl)imide anion molecule are aligned almost perpendicular to the long axis of the cationic cyanine fluorophore to inhibit p/p interactions between the fluorophores. Thus, compound 16d has isolated monomer-type packing.
Fig. 7. X-ray structure of 16c.
The X-ray structure of 14d is shown in Fig. 8. Molecules form a pair of dimers and are arranged in a zigzag form. A cationic fluorophore has two short contacts with bis(trifluoromethylsulfonyl) imide anion (overview (2)). One is between one of the sulfonyl-
Fig. 9. X-ray structure of 16d.
Fig. 8. X-ray structure of 14d.
There are two factors affecting the solid-state fluorescence intensity: melting point and packing motif. When the melting point is low, the stretching, vibration, and rotation processes of the molecule can occur to reduce the fluorescence intensity.9,11 The Ff of bis(perfluorobutylsulfonyl)imide derivative 16e (0.02) and N-octyl derivative 18d (0.02) are low. The melting points of 16e (80e82 C) and 18d (81e83 C) are significantly low compared with those of
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the other derivatives (170e171 to 260e262 C). Thus, low Ff of 16e and 18d can come from their low melting point. Coulomb forces are inversely proportional to the square of the distance between the cationic and anionic species. The short contact lengths between the cationic fluorophore and the anion species in 16c and 16d are 3.52 and 3.51 A, respectively, being similar. Nevertheless, the Ff of 16d (0.31) is significantly larger than that of 16c (0.06). Thus, no clear relationship between the short contact length and Ff is observed. In the case of neutral compounds, the consequent p/p stacking and intermolecular hydrogen bonds could reduce the solid-state fluorescence intensity.12 Compound 14d (Ff¼0.03) has consequent p/p stacking. Compounds 16b (Ff¼0.03) and 16c (Ff¼0.06) have isolated dimer-type packing with p/p interactions. Compound 16d (Ff¼0.31) has isolated monomer-type packing. It is concluded that the cyanine dyes having the least p/p interactions among adjacent cationic fluorophores could exhibit the most intense fluorescence in the solid-state. 3. Conclusion The solid-state fluorescence properties of indolenium carbocyanine dyes were examined. The cyanine dyes showed Fmax at around 660 nm in the solid state. The fluorescence intensity depended on both the counter anion and alkyl substituents on the indolenium nitrogen atoms. 1,10 -Dipropyl-3,3,30 3’-tetramethylindocarbocyanine bis(trifluoromethyl-sulfonyl)imide 16d exhibited the most intense fluorescence (Ff¼0.31) at Fmax 657 nm with shoulder peaks. The wave deconvolution indicated that S1,0/S0,0, S1,0/S0,1, and S1,0/S0,2 transitions were contained in the fluorescence spectrum. The X-ray crystallography suggests that the most intense fluorescence of 16d in the solid state can come from the isolated monomer-type packing, having the least p/p interactions among adjacent cationic fluorophores. Even in the case of cationic fluorophores, not Coulomb forces but the p/p interactions could reduce the fluorescence intensity in the solid state. 4. Experimental 4.1. Instruments Melting points were measured with a Yanagimoto MP-S2 micromelting-point apparatus. IR spectra were taken by a Shimadzu Affinity-1 spectrophotometer. NMR spectra were obtained by a JEOL ECX 400P spectrometer. MS spectra were measured with a JEOL MStation 700 spectrometer. Elemental analysis was performed with a Yanaco MT-6 CHN corder. UV-Vis absorption and fluorescence spectra were taken on Hitachi U-3500 and JASCO FP8600 spectrophotometers, respectively. 4.2. Materials 2,3,3-Trimethylindolenine (1), 1-propyl bromide (4), 1-propyl iodide (5), 1-butyl iodide (6), 1-octyl iodide (7), and triethoxymethane (13) were purchased from Tokyo Kasei Co., Ltd. Methyl iodide(2) was purchased from Nacalai Tesque Co., Ltd. Ethyl iodide (3), lithium bis(trifluoromethylsulfonyl)imide (19d) and lithium bis(1,1,2,2,3,3,4,4,4-nonafluoro-1-butanesulfonyl)imide (19e) were purchased from Wako Pure Chemical Industries. Lithium trifluoromethanesulfonate (19c) was purchased from Aldrich Chem. Co., Ltd. 1-Alkyl-2,3,3-trimethyl-3H-indolenium halides 8b, 9b, 10a, 10b, 11b, and 12b were prepared by the reaction of 1 with alkyl halides. Cyanine dyes 14b,13 15b,14 and 17b15 were prepared as described in the literature.
4.3. Synthesis of 3,3,30 30 -tetramethyl-1,10 -dialkylindocarbocyanine halides 16a, 16b, and 18b To a pyridine solution (10 mL) of 1-alkyl-2,3,3-trimethyl-3Hindolenium halides 10a, 10b, and 12b (6 mmol) was added triethoxymethane (13, 0.534 g, 3.6 mmol). The mixture was refluxed for 6 h. After the reaction was completed, to the mixture were added water (20 mL) and dichloromethane (50 mL). The dichloromethane layer was separated, washed with water (50 mL3), and dried over anhydrous sodium sulfate. The solvent was removed in vacuo. The resulting precipitate was washed with hexane. The product was purified by silica gel column chromatography (CH2Cl2 then CH2Cl2eMeOH¼10:1) and recrystallized from ethanol. 4.3.1. 1,10 -Dipropyl-3,3,30 30 -tetramethylindocarbocyanine bromide (16). Yield 68%; mp 255257 C; IR (KBr) n 1556 cm1; 1H NMR (CDCl3) d¼1.15 (t, J¼7.4 Hz, 6H), 1.72 (s, 12H), 1.96 (sex, J¼7.4 Hz, 4H), 4.26 (t, J¼7.4 Hz, 4H), 7.12 (d, J¼7.8 Hz, 2H), 7.24 (t, J¼7.8 Hz, 2H), 7.38 (d, J¼7.8 Hz, 2H), 7.39 (t, J¼7.8 Hz, 2H), 7.48 (d, J¼13.5 Hz, 2H), 8.46 (t, J¼13.5 Hz, 1H); 13C NMR (CDCl3) d¼11.5 (2C), 21.0 (2C), 28.1 (4C), 46.1 (2C), 48.8 (2C), 104.8 (2C), 110.9 (2C), 122.0 (2C), 125.0 (2C), 128.7 (2C), 140.5 (2C), 142.2 (2C), 150.7, 173.6 (2C); FABMS (NBA) m/z 413 (MþI); Anal. Found: C, 70.70, H, 7.63, N, 5.59%, Calcd for C29H37BrN2: C, 70.58; H, 7.56; N, 5.68%. iodide 4.3.2. 1,10 -Dipropyl-3,3,30 30 -tetramethylindocarbocyanine (16b). Yield 71%; mp 260e262 C; IR (KBr) n 1559 cm1; 1H NMR(CDCl3) d¼1.17 (t, J¼7.4 Hz, 6H), 1.74 (s, 12H), 1.95 (sex, J¼7.4 Hz, 4H), 4.26 (t, J¼7.4 Hz, 4H), 7.13 (d, J¼7.8 Hz, 2H), 7.25 (t, J¼7.8 Hz, 2H), 7.37 (d, J¼7.8 Hz, 2H), 7.39 (t, J¼7.8 Hz, 2H), 7.52 (d, J¼13.5 Hz, 2H), 8.45 (t, J¼13.5 Hz, 1H); 13C NMR (CDCl3) d¼11.8 (2C), 21.2 (2C), 28.3 (4C), 46.4 (2C), 49.0 (2C), 104.9 (2C), 111.1 (2C), 122.2 (2C), 125.3 (2C), 128.9 (2C), 140.8 (2C), 142.4 (2C), 150.9, 173.8 (2C); FABMS (NBA) m/z 413 (MþI); Anal. Found: C, 64.57, H, 6.99, N, 5.34%, Calcd for C29H37IN2: C, 64.44; H, 6.90; N, 5.18%. 4.3.3. 1,10 -Dioctyl-3,3,30 30 -tetramethylindocarbocyanine iodide (18b). Yield 67%; mp 86e88 C; IR (KBr) n 1559 cm1; 1H NMR (CDCl3) d¼0.86 (t, J¼7.4 Hz, 6H), 1.22e1.40 (m, 16H), 1.56 (quin, J¼7.4 Hz, 4H), 1.71 (s, 12H), 1.88 (quin, J¼7.4 Hz, 4H), 4.28 (t, J¼7.4 Hz, 4H), 7.11 (d, J¼7.8 Hz, 2H), 7.24 (t, J¼7.8 Hz, 2H), 7.36 (d, J¼7.8 Hz, 2H), 7.37 (t, J¼7.8 Hz, 2H), 7.46 (d, J¼13.6 Hz, 2H), 8.44 (t, J¼13.6 Hz, 1H); 13C NMR (CDCl3) d¼14.1 (2C), 22.6 (2C), 27.0 (2C), 27.7 (2C), 28.1 (4C), 29.1 (2C), 29.5 (2C), 31.8 (2C), 45.1 (2C), 48.8 (2C), 104.9 (2C), 111.0 (2C), 122.0 (2C), 125.0 (2C), 128.8 (2C), 140.7 (2C), 142.4 (2C), 150.8, 173.4 (2C); FABMS (NBA) m/z 553 (MþI); Anal. Found: C, 68.98, H, 8.56, N, 4.10%, Calcd for C39H57IN2: C, 68.81; H, 8.44; N, 4.11%. 4.4. Synthesis of 1,10 -dialkyl-3,3,30 30 -tetramethylindocarbocyanine dyes 14d, 15d, 16c, 16d, 16e, 17d, and 18d To an acetoneewater (1:1 vol, 10 mL) mixed solution of 1,10 dialkyl-3,3,30 30 -tetramethylindocarbocyanine iodides 14b, 15b, 16b, 17b, and 18b (0.5 mmol) was added lithium salts 19c, 19d, and 19d (0.6 mmol). The mixture was stirred at room temperature for 6 h. After the reaction was completed, to the mixture were added water (20 mL) and dichloromethane (50 mL). The dichloromethane layer was separated, washed with water (50 mL3), and dried over anhydrous sodium sulfate. The solvent was removed in vacuo. The product was purified by alumina column chromatography (CH2Cl2 then CH2Cl2eAcOEt¼20:1) and recrystallized from ethanol. 4.4.1. 1,10,3,3,30 30 -Hexamethylindocarbocyanine bis(trifluoromethylsulfonyl)imide (14d). Yield 86%; mp 132e133 C; IR (KBr) n 1562, 1354 cm1; 1H NMR(CDCl3) d¼1.73 (s, 12H), 3.66 (s,
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6H), 6.49 (d, J¼13.2 Hz, 2H), 7.14 (d, J¼7.7 Hz, 2H), 7.27 (t, J¼7.7 Hz, 2H), 7.37 (d, J¼7.7 Hz, 2H), 7.40 (t, J¼7.7 Hz, 2H), 8.43 (t, J¼13.2 Hz, 1H); 19F NMR (CDCl3) d¼78.5; 13C NMR (CDCl3) d¼28.1 (4C), 31.5 (2C), 49.2 (2C), 104.0 (2C), 110.9 (2C), 120.1 (q, J¼320 Hz, 2C), 122.2 (2C), 125.7 (2C), 129.0 (2C), 140.5 (2C), 142.7 (2C), 150.7, 174.8 (2C); FABMS (NBA) m/z 357 (Mþ(CF3SO2)2N); Anal. Found: C, 50.94; H, 4.66; N, 6.54%. Calcd For C27H29F6N3O4S2: C, 50.86; H, 4.58; N, 6.59%. 4.4.2. 1,10 -Diethyl-3,3,30 30 -tetramethylindocarbocyanine bis(trifluoromethylsulfonyl)imide (15d). Yield 87%; mp 170e172 C; IR (KBr) n 1559, 1354 cm1; 1H NMR(CDCl3) d¼1.45 (t, J¼7.2 Hz, 6H), 1.73 (s, 12H), 4.16 (q, J¼7.2 Hz, 4H), 6.44 (d, J¼13.4 Hz, 2H), 7.14 (d, J¼7.8 Hz, 2H), 7.28 (t, J¼7.8 Hz, 2H), 7.38 (d, J¼7.8 Hz, 2H), 7.41 (t, J¼7.8 Hz, 2H), 8.41 (t, J¼13.4 Hz, 1H); 19F NMR (CDCl3) d¼78.5; 13C NMR (CDCl3) d¼12.3 (2C), 28.0 (4C), 39.5 (2C), 49.2 (2C), 102.9 (2C), 110.7 (2C), 120.0 (q, J¼320 Hz, 2C), 122.3 (2C), 125.6 (2C), 128.9 (2C), 140.7 (2C), 141.5 (2C), 150.7, 173.7 (2C); FABMS (NBA) m/z 385 (Mþ(CF3SO2)2N); Anal. Found: C, 52.14; H, 5.01; N, 6.21%. Calcd for C29H33F6N3O4S2: C, 52.32; H, 5.00; N, 6.31%. tri4.4.3. 1,10 -Dipropyl-3,3,30 30 -tetramethylindocarbocyanine fluoromethanesulfonate (16c). Yield 75%; mp 201e202 C; IR (KBr) n 1559, 1354 cm1; 1H NMR (CDCl3) d¼1.09 (t, J¼7.3 Hz, 6H), 1.73 (s 12H), 1.92 (sex, J¼7.3 Hz, 4H), 4.16 (t, J¼7.3 Hz, 4H), 6.84 (d, J¼13.3 Hz, 2H), 7.12 (d, J¼7.8 Hz, 2H), 7.24 (t, J¼7.8 Hz, 2H), 7.37 (d, J¼7.8 Hz, 2H), 7.40 (t, J¼7.8 Hz, 2H), 8.41 (t, J¼13.3 Hz, 1H); 19F NMR (CDCl3) d¼78.0; 13C NMR (CDCl3) d¼11.3 (2C), 21.0 (2C), 28.2 (4C), 45.9 (2C), 49.3 (2C), 103.6 (2C), 111.1 (2C), 121.1 (q, J¼320 Hz), 122.4 (2C), 125.4 (2C), 128.9 (2C), 140.7 (2C), 142.2 (2C), 150.9, 174.3 (2C); FABMS (NBA) m/z 413 (MþCF3SO3); Anal. Found: C, 63.65; H, 6.59; N, 4.87%. Calcd for C30H37F3N2O3S: C, 64.04; H, 6.63; N, 4.98%. 4.4.4. 1,10 -Dipropyl-3,3,30 30 -tetramethylindocarbocyanine bis(trifluoromethylsulfonyl)imide (16d). Yield 78%; mp 203e204 C; IR (KBr) n 1558, 1354 cm1; 1H NMR(CDCl3) d¼1.06 (t, J¼7.3 Hz, 6H), 1.74 (s, 12H), 1.90 (sex, J¼7.3 Hz, 4H), 4.09 (t, J¼7.3 Hz, 4H), 6.46 (d, J¼13.3 Hz, 2H), 7.13 (d, J¼7.8 Hz, 2H), 7.26 (t, J¼7.8 Hz, 2H), 7.38 (d, J¼7.8 Hz, 2H), 7.40 (t, J¼7.8 Hz, 2H), 8.42 (t, J¼13.3 Hz, 1H); 19F NMR (CDCl3) d¼78.5; 13C NMR (CDCl3) d¼11.3 (2C), 20.9 (2C), 28.2 (4C), 45.9 (2C), 49.4 (2C), 103.1 (2C), 111.2 (2C), 120.1 (q, J¼320 Hz, 2C), 122.4 (2C), 125.7 (2C), 129.0 (2C), 140.7 (2C), 142.2 (2C), 150.7, 174.4 (2C); FABMS (NBA) m/z 413 (Mþ(CF3SO2)2N); Anal. Found: C, 53.65; H, 5.24; N, 6.16%. Calcd for C31H37F6N3O4S2: C, 53.67; H, 5.38; N, 6.06%. 4.4.5. 1,10 -Dipropyl-3,3,30 30 -tetramethylindocarbocyanine bis(perfluorobutylsulfonyl)imide (16e). Yield 85%; mp 80e82 C; IR (KBr) n 1556, 1357 cm1; 1H NMR (CDCl3) d¼1.06 (t, J¼7.3 Hz, 6H), 1.75 (s 12H), 1.89 (sex, J¼7.3 Hz, 4H), 4.07 (t, J¼7.3 Hz, 4H), 6.36 (d, J¼13.3 Hz, 2H), 7.14 (d, J¼7.8 Hz, 2H), 7.27 (t, J¼7.8 Hz, 2H), 7.40 (d, J¼7.8 Hz, 2H), 7.42 (t, J¼7.8 Hz, 2H), 8.45 (t, J¼13.3 Hz, 1H); 19F NMR (CDCl3) d¼80.7, 112.6, 120.9, 125.8; FABMS (NBA) m/z 413 (Mþ(C4F9SO2)2N); Anal. Found: C, 45.05; H, 3.65; N, 3.97%. Calcd for C37H37F18N3O4S2: C, 44.72; H, 3.75; N, 4.23%. bis(tri4.4.6. 1,10 -Dibutyl-3,3,30 30 -tetramethylindocarbocyanine fluoromethylsulfonyl)imide (17d). Yield 65%; mp 170e171 C; IR (KBr) n 1554, 1350 cm1; 1H NMR(CDCl3) d¼1.00 (t, J¼7.6 Hz, 6H), 1.49 (sex, J¼7.6 Hz, 4H), 1.73 (s, 12H), 1.82 (quin, J¼7.6 Hz, 4H), 4.10 (t, J¼7.6 Hz, 4H), 6.37 (d, J¼13.6 Hz, 2H), 7.13 (d, J¼7.7 Hz, 2H), 7.28 (t, J¼7.7 Hz, 2H), 7.38 (d, J¼7.7 Hz, 2H), 7.40 (t, J¼7.7 Hz, 2H), 8.43 (t, J¼13.6 Hz, 1H); 19F NMR (CDCl3) d¼78.5; 13C NMR (CDCl3) d¼13.9 (2C), 20.2 (2C), 28.1 (4C), 29.6 (2C), 44.5 (2C), 49.4 (2C), 103.0 (2C), 111.1 (2C), 120.1 (q, J¼319 Hz, 2C), 122.3 (2C), 125.7 (2C), 129.0 (2C), 140.7 (2C), 142.1 (2C), 150.7, 174.3 (2C); FABMS (NBA) m/z 441
3533
(Mþ(CF3SO2)2N); Anal. Found C, 54.67; H, 5.69; N, 5.75%. Calcd for C33H41F6N3O4S2: C, 54.91; H, 5.73; N, 5.82%. 4.4.7. 1,10 -Dioctyl-3,3,30 30 -tetramethylindocarbocyanine bis(trifluoromethylsulfonyl)imide (18d). Yield 80%; mp 81e83 C; IR (KBr) n 1556, 1354 cm1; 1H NMR (CDCl3) d¼0.86 (t, J¼7.1 Hz, 6H), 1.24e1.39 (m, 16H), 1.45 (quin, J¼7.1 Hz, 4H), 1.74 (s, 12H), 1.83 (quin, J¼7.1 Hz, 4H), 4.10 (t, J¼7.1 Hz, 4H), 6.39 (d, J¼13.6 Hz, 2H), 7.12 (d, J¼7.9 Hz, 2H), 7.27 (t, J¼7.9 Hz, 2H), 7.39 (d, J¼7.9 Hz, 2H), 7.40 (t, J¼7.9 Hz, 2H), 8.42 (t, J¼13.6 Hz, 1H); 19F NMR (CDCl3) d¼78.5; 13C NMR (CDCl3) d¼14.1 (2C), 22.7 (2C), 26.9 (2C), 27.6 (2C), 28.1 (4C), 29.1 (2C), 29.4 (2C), 31.8 (2C), 44.6 (2C), 49.3 (2C), 103.2 (2C), 111.2 (2C), 120.1 (q, J¼320 Hz, 2C), 122.3 (2C), 125.6 (2C), 129.0 (2C), 140.7 (2C), 142.2 (2C), 150.6, 174.2 (2C); FABMS (NBA) m/z 553 (Mþ(CF3SO2)2N); Anal. Found: C, 59.38; H, 6.94; N, 5.04%. Calcd for C41H57F6N3O4S2: C, 59.04; H, 6.89; N, 5.04%. 4.5. X-ray crystallographic analysis Single crystals were obtained by diffusion method using dichloromethane and hexane. The diffraction data were collected by using graphite monochromated Mo-Ka radiation (l¼0.71069 A). The structure was solved by direct methods SIR97 and refined by fill-matrix least-squares calculations. 4.5.1. Crystal data for 14d. C27H29F6N3O4S2, Mw¼637.65, orthorhombic, P212121, Z¼4, a¼11.713(4), b¼15.106(5), c¼16.252(5) A, Dcalcd¼1.473 g cm3, T¼123 K, 23,725 reflections were corrected, 6568 unique (Rint¼0.0558), 385 parameters, R1¼0.0508, wR2¼0.0890, G.O.F 1.096, CCDC (724452). 4.5.2. Crystal data for 16b. C29H37IN2, Mw¼540.51, monoclinic, P21/ c, Z¼4, a¼10.4987(16), b¼18.633(3), c¼16.604(1) A, b¼107.509(7), Dcalcd¼1.159 g cm3, T¼293 K, 31,523 reflections were corrected, 7035 unique (Rint¼0.0544), 290 parameters, R1¼0.1226, wR2¼0.3749, G.O.F 1.246. CDCC (963762). 4.5.3. Crystal data for 16c. C30H37F3N2O3S, Mw¼562.68, monoclinic, P21/c, Z¼4, a¼10.5524(17), b¼18.3636(19), c¼16.716(2) A, b¼106.965(6), Dcalcd¼1.206 g cm3, T¼293 K, 31,761 reflections were corrected, 7066 unique (Rint¼0.0402), 290 parameters, R1¼0.0999, wR2¼0.2883, G.O.F 1.021. CDCC (963763). 4.5.4. Crystal data for 16d. C31H37F6N3O4S2, Mw¼693.76, monoclinic, P21/n, Z¼8, a¼9.852(2), b¼20.888(3), c¼33.913(5) A, Dcalcd¼1.321 g cm3, T¼293(2) K, 66,349 reflections were corrected, 7968 unique (Rint¼0.1150), 421 parameters, R1¼0.1185, wR2¼0.3211, G.O.F 1.144. CDCC (963764). Supplementary data UVevis absorption and fluorescence spectra of 16d in various solvents, 1H spectra of 14b, 14d, 15b, 15d, 16a, 16b, 16c, 16d, 16e, 17b, 17d, 18b, and 18d, single X-ray data for 14d, 16b, 16c, and 16d. This material is available free of charge via internet. Supplementary data related to this article can be found at http://dx.doi.org/10.1016/ j.tet.2015.03.027. References and notes 1. (a) Haugland, R. Handbook of Fluorescent Probes and Research Chemicals, 8th ed.; Molecular Probes: Eugene, OR, 2001; (b) Galbraith, E.; James, T. D. Chem. Soc. Rev. 2010, 39, 3831e3842. 2. Nakazumi, H. J. Soc. Dye. Colour. 1988, 104, 121e125. 3. Chang, Y.-J.; Chow, T. J. J. Mater. Chem. 2011, 21, 3091e3099. 4. (a) Funabiki, K.; Mase, H.; Hibino, A.; Tanaka, N.; Mizuhata, N.; Sakuragi, Y.; Nakashima, A.; Yoshida, T.; Kubota, Y.; Matsui, M. Energy Environ. Sci. 2011, 4,
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