HETEROCYCLES

Paper | Regular issue | Vol. 85, No. 7, 2012, pp. 1683-1695
Received, 15th May, 2012, Accepted, 29th May, 2012, Published online, 6th June, 2012.
DOI: 10.3987/COM-12-12507

■ Synthesis and Complexation of Bis(1-azaazulen-2-yl)amines and Bis(1-azaazulen-2-yl) Sulfides

Eiko Yoshioka, Kazuya Koizumi, Kenji Nakashima, Hiroyuki Fujii, Toshihiro Murafuji, Takahiro Gunji, and Noritaka Abe*

Department of Pure and Applied Chemistry, Faculty of Science and Technology, Tokyo University of Science, 2641 Yamazaki, Noda, Chiba 278-8510, Japan

Abstract

Complexation of bis(3-phenyl-1-azaazulen-2-yl)amine with Zn(OAc)2 and Ni(OAc)2 was investigated, and four-coordinate bis-chelate complexes, M(II) bis[(3-phenyl-1-azaazule-2-yl)(3-phenyl-1-azaazulen-2-ylidene)aminate] (M = Zn, Ni), were obtained. Complexation of bis(1-azaazulen-2-yl) sulfide with CoCl2 gave 2 : 1 ligand-metal complex as major product and complexation of bis(3-iodo-1-azaazulen-2-yl) sulfide with CoCl2 gave 1 : 1 ligand-metal complex.

INTRODUCTION
Dipyrrins (1) (the molecule have been known by many names: dipyrromethene, dipyrrolemethene, diaza-s-indacene, etc.) are known because of their ability of the formation of charge-neutral chelated complexes with variety of metal cations.1a The chemistry of BODIPY (BF2-chelated dipyrrin) was extensively investigated1 as a new El Dorado for fluorescence tools.1b BODIPYs have found widespread applications from their property of highly fluorescent dyes and used as biolabels, light harvesters, sensitizers, for solar cells, fluorescent sensors, and energy-transfer reagent, etc.,1 as well as laser dyes,2 fluorescence probe for nitric oxide,3 and for acidic pH.4 For these utility, syntheses for many new type of BODIPY were investigated.5-8
Aza-dipyrrins (azadipyrromethenes) (3) are aza-analogues of dipyrrins (dipyrromethenes) and recently extensively investigated.1d Azadipyrromethene-BF2 complexes (aza-BODIPY dyes) (4)9-18 are modified BODIPY and showed fluorescent spectra at red to near-infrared (NIR) region, and used as phototherapeutic agents,9 molecular sensors,10-12 and NIR fluorescent probs.13

The complexes of azadipyrromethenes with metal cations other than BF2 are investigated from the interest for future designed uses in catalysis, metal-organic frameworks, optical data storage, and electrochromic devices, but the reports were few. Recently, it is reported that azadipyrromethene with divalent metals [Co(II), Ni(II), Cu(II), Zn(II), and Hg(II)] consisted four-coordinate bis-chelate complexes (5)19,20 and azadipyrromethene with monovalent metals [Cu(I), Ag(I), and Au(I)] formed tri-coordinate complexes (6).21

The chemistry of azaazulenes is attracted attention for their interest physical and chemical properties as well as physiological properties.22 The chemistry of heteroaryl-substituted 1-azaazulenes as ligands is of interested and some reports about the complexation with metal ions were made.23-25 It is reported that the complexes of 2-(2-pyridy)-1-azaazulene with metal cations23 and [2-(2-pyridy)](1-azaazulen-2-yl)amine with metal cations caused interesting emissions,24 where S2-S0 transition or S1-S0 transition occurred depend on the metal cation species. Recently, the investigation about synthesis and the emission spectra of 2-(2-hyddroxyphenyl)-1-azaazulene and its metal complexes was also reported.26 It is considered that bis(1-azaazulen-2-yl)amines (7) could exist its tautomeric form (8) in the heteroaryl-substituted 1-azaazulenes, which are formally cyclohepta-annulated aza-dipyrrins (cyclohepta-annulated azadipyrromethenes), therefore their complexation with metal cations is of interest.

RESULTS AND DISCUSSION
We previously reported the synthesis of bis(1-azaazulen-2-yl)amines (7) by Buchwald-Hartwig coupling, but their details about the structure were not discussed in the report.27 So, we investigated some properties of 7 in this paper. At first we examined the synthesis of bis(3-phenyl-1-azaazulen-2-yl)amine (9) from bis(3-iodo-1-azaazulen-2-yl)amine, but an iodinatation of bis(1-azaazulen-2-yl)amine with N-iodosuccinimide (NIS) or a coupling reaction of 2-amino-3-iodo-1-azaazulene and 2-chloro-3-iodo-1-azaazulene in the presence of Pd2(dba)3, Xantphos, and Cs2CO3 were failed. Finally, 9 was synthesized by the reaction of 2-amino-3-phenyl-1-azaazulene and 2-chloro-3-phenyl-1-azaazulene in the presence of Pd2(dba)3, Xantphos, and Cs2CO3 in 43% yield.

The 1H and 13C NMR spectra of bis(3-phenyl-1-azaazulen-2-yl)amine showed highly symmetrical feature. In the 1H NMR spectrum, an amine proton was appeared at rather lower field (δ 13.57). The UV-Vis spectrum of 9 shows strong and wide range absorptions at λmax 289 nm (log ε 4.64), 369 (4.29), 404 (4.08, sh), 468 (4.09, sh), 498 (4.19), 568 (4.40), 603 (4.41), and 650 (4.06, sh), and its feature was rather different from the ordinal 1-azaazulene form (Figure 1). Therefore, it is considered that bis(3-phenyl-1-azaazulen-2-yl)amine takes the tautomeric form 10 and 10A; 10B would be a more adequate form.
Consideration of the structure of 10b suggested that 10 could form complexes with metal cations. Therefore we examined the complexation of 10 with BF3 at first. When 10 was treated with BF3･OEt2 in the presence of Et3N, a fluorescent product was observed by TLC, but the product was changed to blue powders by the separation with column chromatography on silica gel and could not be isolated. So we

could not assign the structure of fluorescent product. Next, we treated 10 with Zn(OAc)2･2H2O in THF, and obtained 2 : 1 ligand-metal complex (11) as reddish brown powders in 62% yield. The 1H and 13C NMR spectra of 11 showed highly symmetrical feature. Its Uv-Vis spectrum was somewhat resembled to that of 10, but the absorption of longest wavelength of 11 was rather strong [λmax 634 nm (log ε 4.90)] than that of 10 (Figure 1). From these results as well as elemental analysis, we assigned the structure as Zn(II) bis[(3-phenyl-1-azaazule-2-yl)(3-phenyl-1-azaazulen-2-ylidene)amine], which has the four-coordinate structure. Because we could not obtain favorable crystals for X-ray crystallographic analysis unfortunately, we could not define the exact structure. But the presented structure would be reasonable from the consideration of the structure of 5.20 Similar treatment of 10 with Ni(OAc)2･4H2O in THF gave 12 in 24% yield. The UV-Vis spectrum of 12 was resembled to that of 11. Although the

intensity of the absorption of 12 was weak than that of 11 [λmax 627 nm (log ε 4.71)] (Figure 1), it was about twice of that of 10. The results suggested that two bis(3-phenyl-1-azaazulen-2-yl)amine moieties exist. The Ni(II) complex (12) would be paramagnetic and its 1H NMR spectrum was appeared at wide range and showed broadening signals: δ -2.55 (4H, br, H-4), 2.16 (8H, br, H-o-Ph), 4.95 (4H, br, H-p-Ph), 5.55 (8H, br, H-m-Ph), 9.43 (4H, br, H-5), 14.78 (8H, br, H-6 and 7), and 22.16 (4H, br, H-8).
Unlike the cases of Zn(II) and Ni(II) complexes of 10, the complexation of 10 with Zr(IV) showed a different feature. The reaction of 10 with 0.44 equivalent of ZrCl4･2THF gave 1 : 1 ligand-metal complex (13), which was determined by elemental analysis. Its 1H NMR spectrum showed symmetrical feature, and some bond alternation was observed from the consideration of coupling constants of the seven-membered ring protons (J 9.2~11.4), which would be owing to contribution of heptafulvene form. The UV-Vis spectrum of 13 was resembled to those of 11 and 12, but the absorption of longest wavelength was rather weak compared to those of 11 and 12 and is suitable as possessing one bis(3-phenyl-1-azaazulen-2-yl)amine moiety [λmax 635 nm (log ε 4.32)] (Figure 1). So we assigned the structure to formally penta-coordinate chelate complex (13). The resemblance of the UV-Vis spectra of 11, 12, and 13 suggested that the influences to the electronic state of (1-azaazule-2-yl)(1-azaazulen-2-ylidene)amine nuclei by coordination of metal cations would be basically similar.

Recently, Oda et al. reported about the synthesis of 14 and its UV-Vis spectrum and emission spectrum in the presence of Zn(ClO4)2.24 Although they did not discuss about the structure of 14-Zn(II) complex, the fact that the UV-Vis spectrum of 14 in the presence of metal cation was resembled to 11 is of interest for comparison with above mentioned results.

We next examined the complexation of bis(1-azaazulen-2-yl) sulfides. Bis(1-azaazulen-2-yl) sulfide (15a) was prepared by previously reported procedures.26 Bis(3-iodo-1-azaazulen-2-yl) sulfide (15b) was prepared by iodinatation of 15a with NIS in 56% yield. The UV-Vis spectrum of 15b shows absorptions at λmax (MeOH) 284 nm (log ε 4.48), 318 (4.27, sh), 397 (3.93), and 507 (3.52), and its feature was ordinal 1-azaazulene form (Fig. 2). Bis(3-phenyl-1-azaazulen-2-yl) sulfide was obtained only in trace yield by Suzuki coupling of 15b with phenylboronic acid in the presence of Pd(dppf)･CH2Cl2, BINAP, and Cs2CO3. Therefore we did not examine a complexation of this compound.
Reaction of 15a with ZrCl4･2THF gave reddish orange powders, but we could not assign its molecular formula from MS-ESI+, HRMS-ESI+ and 1H NMR spectrum. In its MS-ESI+, peaks appeared at m/z 641 (rel intensity 3), 639 (6), 386 (2), 311 ([15a + Na]+, 1), and 289 ([15a + H]+, 100); where distinct assignable peaks due to 15a – Zr(IV) complex were not observed. The 1H NMR spectrum showed slightly dissymmetric feature [δ 7.93 (2H, s, H-3,3’), 8.26-8.12 (4H, m, H-6,7,6’,7’), 8.35 (2H, dd, J 9.6 and 9.2, H-5,5’), 8.84 (1H, d, J 9.6, H-4), 8.86 (1H, d, J 9.6, H-4’), 8.93 (1H, d, J 8.8, H-8), and 8.94 (1H, d, J 8.8, H-8’)]. Reaction of 15b with ZrCl4･2THF gave unidentified red powders. Its 1H NMR spectrum was deferent from that of 15b. But its MS showed rather weak peak at m/z 585 (rel intensity 0.01) and a base peak at m/z 540 ([M + H] +) owing to 15b, and distinct assignable peaks were not found. These results suggested some kinds of complexation occurred, but we could not deduce the structures of the products.
Next, we examined the complexation of 15a with Co(II). Treatment of 15a with CoCl2･6H2O gave 16a as red powders in 52% yield. Its HRMS-ESI+ showed a peak at m/z 670.0466, owing to 12C361H2414N435Cl59Co32S2, and which structure was assigned to 17 ([16a - Cl + Na]+; rel intensity 22). In the MS, different from the case of Zr-complex, the peak owing to 15a was not observed. In the MS of 16a, a very weak peak (rel intensity 0.8) was found due to 18a (m/z 439.9315([M + Na]+, Calcd for 12C181H1214N235Cl259Co23Na32S : 439.9328). This showed that the 1 : 1-complex (18a) is also produced in only trace amount, and it is considered that observed peak in MS was a contaminant in 16a. The Co(II) complex (16a) would be paramagnetic and its 1H NMR spectrum was broadening and appeared at wide range of magnetic field: we could not obtain distinct spectrum. In the UV-Vis spectrum of 16a, a longest wavelength of absorption was slightly weak and the fact is suitable that 16a possessed two bis(1-azaazulen-2-yl) sulfide moieties [λmax 482 nm (log ε 3.78)] (Figure 2). So we assigned the structure. The Co-N bond in 16a would be consisted with coordination bonding and not covalent bond.
On the contrary, the treatment of 15b with excess CoCl2･6H2O gave 1 : 1-complex (18b) in 69% yield. Its HRMS-ESI+ showed a peak at m/z 691.7263 due to 12C181H1014N235Cl259Co127I223Na32S ([M + Na]+). The UV-Vis spectrum of 18b was resembled to that of 15b, and a longest wavelength of absorption appeared at λmax 526 nm (log ε 3.67) and it is suitable that 18b possessed one bis(3-iodo-1-azaazulen-2-yl) sulfide moiety (Figure 2). So we assigned the structure. Limited changes in the UV-Vis spectra between 15b and 18b suggested that the coordination of CoCl2 to 15b is weak and the metal cation did not affect substantially to the electronic state of the azaazulene rings.

CONCLUSION
We synthesized four-coordinate bis-chelate complexes (11 and 12) of bis(3-phenyl-1-azaazulen-2-yl)amine with divalent metal [Zn(II) and Ni(II)] and formally penta-coordinate chelate complex (13) with Zr(IV). We also synthesized bis-chelate complex (16) and mono-chelate complex (18) of bis(1-azaazulen-2-yl) sulfides with CoCl2. The UV-Vis spectra of 11 and 12 showed longer wavelength of strong absorptions owing to (3-phenyl-1-azaazulen-2-yl)(3-phenyl-1-azaazulen-2-ylidene)amine nuclei. Whereas the UV-Vis spectra of 16 and 18 were scarcely changed from those of bis(1-azaazulen-2-yl) sulfides.

EXPERIMENTAL
Melting points were determined with a Yanagimoto micro-melting point MP JP-3 apparatus and were uncorrected. 1H NMR spectra were recorded on a Bruker Avance 400S (400MHz) using CDCl3 as a solvent with tetramethylsilane as an internal standard unless otherwise stated; J value are recorded in Hz. Uv-Vis spectra were recorded with JASCO V-570 spectrophotometer. IR spectra were recorded for KBr pellets on a Nicolet FT-IR Impact 410. Mass Spectra (ESI+-MS) were taken with JEOL JMS-T100CS. Elemental analyses were taken with a Perkin Elmer 2400II. Alumina Activated 300 (Nacarai Tesque) was used for column chromatography. Bis(3-phenyl-1-azaazulen-2-yl)amine (10) and bis(1-azaazulen-2-yl) sulfide (15a) were prepared by previously reported procedures.

Synthesis of bis(3-phenyl-1-azaazulen-2-yl)amine
Under argon atmosphere, a mixture of 2-amino-3-phenyl-1-azaazulene (0.209 g, 0.95 mmol), 2-chloro-3-phenyl-1-azaazulene (0.520 g, 2.17 mmol), Cs2CO3 (0.444 g, 1.86 mmol), Xantphos (0.038 g, 0.065 mmol), and Pd2(dba)3 (0.052 g, 0.057 mmol) in dry dioxane (12 mL) was refluxed for 24 h, then water (20 mL) was added. The mixture was extracted with CHCl3. The extract was dried over Na2SO4, and evaporated. Chromatography of the residue with CHCl3-AcOEt (1 : 1) gave bis(3-phenyl-1-azaazulen-2-yl)amine (10) (0.173 g, 43%).
10: Dark red powders (from CHCl3-AcOEt), mp 255-256 ℃; 1H NMR (DMSO-d6) δ 7.29 (2H, like t, J 9.1, H-6 and 6’), 7.32 (2H, t, J 7.6, H-p-Ph), 7.34 (2H, like t, J 9.3, H-5 and 5’), 7.47 (4H, dd, J 7.6 and 7.3 H-m-Ph), 7.49 (2H, like t, J 10.0, H-7 and 7’), 7.78 (4H, d, J 7.3, H-o-Ph), 8.04 (2H, dm, J 10.0, H-8 and 8’) and 8.05 (1H, dm, J 9.3, H-4 and 4’) and 13.57 (1H, br, NH); 13C NMR (DMSO-d6) δ 120.33, 122.65, 126.80, 128.10, 128.60, 130.23, 131.12, 131.86, 131.92, 133.16, 140.05, 151.59, and 163.04; νmax / cm-1 3440 (NH); λmax (CH2Cl2) nm (log ε) 289 (4.64), 369 (4.29), 404 (4.08, sh), 468 (4.09, sh), 498 (4.19), 568 (4.40), 603 (4.41), and 650 (4.06, sh). Anal. Calcd for C30H21N3: C, 85.08; H, 5.00; N, 9.92. Found: C, 85.12; H, 5.13; N, 9.74.
Complexation of bis(3-phenyl-1-azaazulen-2-yl)amine with Zn(OAc)2
A mixture of 10 (0.033 g, 0.078 mmol) and Zn(OAc)2･2H2O (0.008 g, 0.036 mmol) in THF (20 mL) was stirred for 17 h at rt. The precipitate was filtered through a celite pad and washed with CH2Cl2 and MeOH. Evaporation of the combined filtrate gave bis[bis(3-phenyl-1-azaazulen-2-yl)amine] – zinc complex (11) as black powders, which was recrystallized from THF to give reddish brown powders (0.020 g, 62%).
11: Reddish brown powders (from THF), mp >300 ℃; 1H NMR δ 6.94 (4H, dd, J 10.5 and 8.8, H-7), 7.02 (4H, dd, J 10.5 and 9.6, H-6), 7.10 (4H, dd, J 10.7 and 9.6, H-5), 7.27 (4H, d, J 8.8, H-8), 7.38 (4H, dd, J 7.4 and 1.2, H-p-Ph), 7.52 (8H, dd, J 8.1 and 7.4, H-m-Ph), 7.96 (8H, dd, J 8.1 and 1.2, H-o-Ph), and 8.08 (4H, d, J 10.7, H-4); 13C NMR δ 121.69, 123.69, 126.70, 128.64, 130.18, 130.43, 131.89, 133.49, 141.43, 155.92, and 165.27; λmax (CH2Cl2) nm (log ε) 288 (4.87), 379 (4.54), 412 (4.36), 547 (4.54), 585 (4.83), and 634 (4.90). Anal. Calcd for C60H40N6Zn･2/3AcOEt: C, 77.67; H, 4.71; N, 8.67. Found: C, 77.55; H, 4.51; N, 8.84.
Complexation of bis(3-phenyl-1-azaazulen-2-yl)amine with Ni(OAc)2
A mixture of 10 (0.017 g, 0.040 mmol) and Ni(OAc)2･4H2O (0.005 g, 0.020 mmol) in THF (5 mL) was stirred for 18 h at rt. The precipitate was filtered through a celite pad and washed with CH2Cl2. Then the precipitate was washed with MeOH. Evaporation of the eluent of MeOH gave bis[bis(3-phenyl-1-azaazulen-2-yl)amine] – Ni(II) complex (12) as black powders, which was recrystallized from THF-pentane to give bronze needles (0.004 g, 24%).
12: Bronze needles (from THF-pentane), mp >300 ℃; 1H NMR δ -2.55 (4H, br, H-4), 2.16 (8H, br, H-o-Ph), 4.95 (4H, br, H-p-Ph), 5.55 (8H, br, H-m-Ph), 9.43 (4H, br, H-5), 14.78 (8H, br, H-6 and 7), and 22.16 (4H, br, H-8); 13C NMR δ 25.70, 67.97, 105.70, 125.97, 126.25, 137.59, and 204.24. λmax (CH2Cl2) nm (log ε) 290 (4.63), 384 (4.48), 412 (4.36, sh), 550 (4.47, sh), 583 (4.61), and 627 (4.71). Anal. Calcd for C60H40N6Ni: C, 79.74; H, 4.46; N, 9.30. Found: C, 80.02; H, 4.51; N, 9.13.
Complexation of bis(3-phenyl-1-azaazulen-2-yl)amine with ZrCl4
Under argon atmosphere, a mixture of 10 (0.056 g, 0.132 mmol) and ZrCl4･2THF (0.022 g, 0.058 mmol) in THF (5 mL) was stirred for 96 h at rt. The precipitate was filtered through a celite pad and washed with CH2Cl2. Then the precipitate was washed with MeOH. Filtrates of THF and CH2Cl2 were combined and evaporated. Chromatography of the residue (hexane : EtOAc = 5 : 1) gve recovered 10 (0.038 g, 68%). Evaporation of the filtrate of MeOH gave black powders, which was recrystallized from THF to give bis(3-phenyl-1-azaazulen-2-yl)amine – zirconium complex (13) (0.024 g, 67%, on the basis of ZrCl4･2THF ).
13: Black powders (from THF), mp 260 ℃ (decomp); 1H NMR δ 7.27-7.42 (10H, m, H-m,p-Ph, 6, 6’, 7, and 7’), 7.52-7.59 (6H, m, H-o-Ph, 5, and 5’), 8.11 (2H, d, J 11.4, H-4 and 4’), and 8.65 (2H, d, J 9.2, H-8 and 8’); δ (DMSO-d6), 7.31 (2H, t, J 7.4, H-p-Ph), 7.44 (4H, dd, J 7.7 and 7.6, H-m-Ph), 7.57- 7.63 (8H, m, H-o-Ph, 6, 6’, 7, and 7’), 7.68 (2H, dd, J 10.2 and 9.1, H-5 and 5’), 7.83 (2H, m, H-4 and 4’), and 8.11 (2H, d, J 10.1, H-8 and 8’); λmax (CH2Cl2) nm (log ε) 278 (4.57), 332 (4.27), 361 (4.25), 402 (3.88), 547 (4.27), 589 (4.32), 635 (4.31), and 635 (4.32). Anal. Calcd for C30H20N3Cl3Zr: C, 58.11; H, 3.25; N, 6.78. Found: C, 58.02; H, 3.77; N, 6.89.
Synthesis of bis(1-azaazulen-2-yl) sulfide
A mixture of 2-mercapto-1-azaazulene (0.151 g, 0.936 mmol) and 60% NaH (0.047 g, 1.17 mmol) in dioxane (10 mL) was stirred for 30 min at rt. To the mixture was added 2-chloro-1-azaazulene (0.212 g, 1.23 mmol), and the mixture was refluxed for 4 h, then water (20 mL) was added. The mixture was extracted with CHCl3. The extract was dried over Na2SO4, and evaporated. Chromatography on alumina of the residue with CHCl3-AcOEt (1 : 1) gave bis(1-azaazulen-2-yl) sulfide (15a) (0.240 g, 88%).
15a: Red micro-needles (from CH2Cl2-hexane), mp 217-219 ℃; 1H NMR δ 7.63 (2H, ddd, J 10.2, 9.9, and 1.3, H-7 and 7’), 7.76 (2H, ddd, J 10.2, 9.9 and 1.6, H-6 and 6’), 7.78 (2H, s, H-3 and 3’), 7.81 (2H, ddd, J 10.2, 9.9, and 1.0, H-5 and 5’), 8.41 (2H, d, J 9.9, H-4 and 4’), and 8.58 (2H, d, J 10.1 and 1.3, H-8 and 8’); 1H NMR (DMSO-d6) δ 7.77 (2H, dd, J 9.8 and 9.6, H-7 and 7’), 7.87 (2H, s, H-3 and 3’), 7.87 (2H, dd, J 10.0 and 9.8, H-6 and 6’), 7.96 (2H, dd, J 10.0 and 9.6, H-5 and 5’), 8.56 (2H, d, J 9.6, H-4 and 4’), and 8.60 (2H, d, J 9.6, H-8 and 8’); 13C NMR δ 114.5, 129.4, 130.0, 133.4, 134.0, 136.6, 146.8, 157.8, and 164.4; 13C NMR (DMSO-d6) δ 114.2, 130.2, 130.5, 134.3, 134.40, 137.8, 146.5, 157.1, and 162.5. Anal. Calcd for C18H12N2S: C, 74.97; H, 4.19; N, 9.71. Found: C, 74.75; H, 4.32; N, 9.84. MS: m/z (rel intensity) 289 ([M + H]+; 100).
Synthesis of bis(3-iodo-1-azaazulen-2-yl) sulfide
A mixture of 15a (0.259 g, 0.90 mmol), NIS (0.630 g, 2.80 mmol) and benzoyl peroxide (0.005 g, 0.05 mmol) in CHCl3 (5 mL) was stirred for overnight. To the mixture was added water and extracted with CHCl3. The extracted was dried over Na2SO4 and evaporated. The residue was chromatographed with CHCl3 to give red powders, and recrystallization from CH2Cl2-hexane gave bis(3-iodo-1-azaazulen-2-yl) sulfide (15b) (0.271 g, 56%) as red powders.
15b: Red micro-needles (from CH2Cl2-hexane), mp 140-141 ℃; 1H NMR δ 7.81 (2H, dd, J 10.4 and 9.6, H-5 and 5’), 7.82 (2H, dd, J 9.6 and 9.2, H-7 and 7’), 7.93 (2H, t, J 9.6, H-6 and 6’), 8.40 (2H, d, J 9.6, H-4 and 4’), and 8.66 (2H, d, J 9.6, H-8 and 8’); λmax (MeOH) nm (log ε) 284 (4.48), 318 (4.27, sh), 397 (3.93), and 507 (3.52). Anal. Calcd for C18H10N2I2S: C, 40.02; H, 1.87; N, 5.19. Found: C, 40.38; H, 2.11; N, 5.33. MS: m/z (rel intensity) 541 ([M + H]+; 100), 414 ([M + H – I]+; 25), 287 ([M + H – 2I]+; 6).
Reaction of bis(1-azaazulen-2-yl) sulfide with ZrCl4
Under argon atmosphere, a mixture of 15a (0.100 g, 0.27 mmol) and ZrCl4･2THF (0.085 g, 0.27 mmol) in THF (5 mL) was stirred for overnight at rt. The precipitate was collected by filtration and red powder (0.078 g) was obtained. Recrystallization from MeOH gave red orange powders, mp 280 ℃ (decomp); 1H NMR δ (DMSO-d6) 7.93 (2H, s, H-3,3’), 8.26-8.12 (4H, m, H-6,7,6’,7’), 8.35 (2H, dd, J 9.6 and 9.2, H-5,5’), 8.84 (1H, d, J 9.6, H-4), 8.86 (1H, d, J 9.6, H-4’), 8.93 (1H, d, J 8.8, H-8), and 8.94 (1H, d, J 8.8, H-8’); MS: m/z (rel intensity) 641 (3), 639 (6), 386 (2), 311 ([15a + Na]+, 1), and 289 ([15a + H]+, 100).
Reaction of bis(3-iodo-1-azaazulen-2-yl) sulfide with ZrCl4
Under argon atmosphere, a mixture of 15b (0.050 g, 0.093 mmol) and ZrCl4･2THF (0.040 g, 0.106 mmol) in THF (5 mL) was stirred for overnight at rt. The precipitate was collected by filtration and red powder (0.039 g) was obtained. Recrystallization from MeOH gave red orange powders, mp 160 ℃ (decomp); 1H NMR δ (DMSO-d6) 8.09-8.17 (4H, m, H-6,7,6’,7’), 8.27 (2H, dd, J 11.2 and 10.4, H-5,5’), and 8.59-8.69 (4H, m, H-4,4’,8,8’). MS: m/z (rel intensity) 585 (0.01), 541 ([15b + H] +; 100).
Complexation of bis(1-azaazulen-2-yl) sulfide with CoCl2
A mixture of 15a (0.100 g, 0.347 mmol) and CoCl2･6H2O (0.066 g, 0.277 mmol) in THF (10 mL) was stirred for 24 h at rt. The precipitate was collected by filtration and bis[bis(1-azaazulene-2-yl) sulfide] – cobalt complex (16a) was obtained as red powders, which was recrystallized from MeOH to give red powders (0.090 g, 52% on the basis of 15a).
16a: Red powders (from MeOH), mp >300 ℃; λmax (MeOH) nm (log ε) 261 (4.54), 282 (4.45, sh), 318 (4.29), 399 (4.08), and 482 (3.78); MS: m/z (rel intensity) 672 ([M - Cl]+; 10), 670 ([M - Cl]+; 22), 529 (11), 394 (21), 312 (31), and 247 (100). HRMS: Calcd for 12C361H2414N435Cl59Co32S2: 670.0463. Found: m/z 670.0466 ([M - Cl]+).
Complexation of bis(3-iodo-1-azaazulen-2-yl) sulfide with CoCl2
A mixture of 15b (0.100 g, 0.185 mmol) and CoCl2･6H2O (0.024 g, 0.101 mmol) in THF (10 mL) was stirred for 24 h at rt. The precipitate was collected by filtration and bis(1-azaazulene-2-yl) sulfide – cobalt complex (18b) was obtained as red powders, which was recrystallized from MeOH to give reddish brown powders (0.048 g, 69% on the basis of CoCl2･6H2O).
18b: Reddish brown powders (from MeOH), mp >300 ℃; λmax (MeOH) nm (log ε) 283 (4.59), 320 (4.40, sh), 396 (4.03), and 526 (3.67); MS: m/z (rel intensity) 694 ([M + Na]+; 13), 692 [M + Na]+; 21), 668 (31), 666 (84), and 563 (100). HRMS: Calcd for 12C181H1014N235Cl259Co127I223Na32S: 691.7261. Found: m/z 691.7263 ([M + Na]+).

ACKNOWLEDGEMENTS
This work was partially supported by Research Fund of Tokyo University of Science.

References

1. a) T. E. Wood and A. Thompson, Chem. Rev., 2007, 107, 1831; CrossRef b) R. Ziessel, G. Ulrich, and A. Harriman, New. J. Chem., 2007, 31, 496; CrossRef c) G. Ulrich, R. Ziessel, and A. Harriman, Angew. Chem. Int. Ed., 2008, 47, 1184; CrossRef d) A. Louded and K. Burgess, Chem. Rev., 2007, 107, 4891; CrossRef e) N. Boens, V. Leen, and W. Dehaen, Chem. Soc. Rev., 2011, DOI: 10.1039/c1cs15132k; CrossRef f) T. Rohand, E. Dolusic, T. H. Ngo, W. Maes, and W. Dehaen, ARKIVOC, 2007, 10, 307; g) R. P. Haugland, ‘The Handbook: A Guide to Fluorescent Probes and Labeling Technologies’, 10th edn,: Molecular Probes, Inc., Eugene, Oregon, 2005; h) Life Technologies (formerly Invitrogen.) Web site: http://probes invitrogen.com. In Molecular Probes; Invitrogen Corporation, 2006.
2. a) M. Shah, K. Thangraj, M.-L. Soong, L. T. Wolford, and J. H. Boyer, Heteroatom Chem., 1990, 1, 389; CrossRef b) J. H. Boyer, A. H. Haag, G. Sathyamoorthi, M.-L. Soong, and K. Thangaraj, Heteroatom Chem., 1993, 4, 39. CrossRef
3. Y. Gave, T. Ueno, Y. Urano, H. Kojima, and T. Nagano, Anal. Bioanal. Chem., 2006, 386, 621. CrossRef
4. Y.-W. Wang, A. B. Descalzo, Z. Shen, X.-Z. You, and K. Rurack, Chem. Eur. J., 2010, 16, 2887. CrossRef
5. M. R. Rao, M. D. Tiwari, J. R. Bellare, and M. Ravikanth, J. Org. Chem., 2011, 76, 7263. CrossRef
6. L. Wu and K. Burgess, Chem. Commun., 2008, 4933. CrossRef
7. V. P. Yakubovskyi, M. P. Shandura, and Y. P. Kovtun, Eur. J. Org. Chem., 2009, 3237. CrossRef
8. W. Wu, H. Guo, W. Wu, S. Ji, and J. Zhao, J. Org. Chem., 2011, 76, 7056. CrossRef
9. a) A. Gorman, J. Killoran, C. O’Shea, T. Kenna, W. M. Gallagher, and D. F. O’Shea, J. Am. Chem. Soc., 2004, 126, 10619; CrossRef b) S. O. McDonnell, M. J. Hall, L. T. Allen, A. Byrne, W. M. Gallagher, and D. F. O’Shea, J. Am. Chem. Soc., 2005, 127, 16360. CrossRef
10. M. J. Hall, L. T. Allen, and D. F. O’Shea, Org. Biomol. Chem., 2006, 4, 776. CrossRef
11. R. E. Gawley, H. Mao, M. M. Haque, J. B. Thorn, and J. S. Pharr, J. Org. Chem., 2007, 72, 2187. CrossRef
12. A. Coskun, M. D. Yilmaz, and E. U. Akkaya, Org. Lett., 2007, 9, 607. CrossRef
13. a) S. O. McDonnell and D. F. S’Shea, Org. Lett., 2006, 8, 3493; CrossRef b) J. Killoran, S. O. McDonnell, J. F. Gallagher, and D. F. O’Shea, New J. Chem., 2008, 32, 483; CrossRef c) A. Loudet, R. Bandichhor, K. Burgess, A. Palma, S. O. McDonnell, M. J. Hall, and D. F. O’Shea, Org. Lett., 2008, 21, 4771; CrossRef d) M. Tasior, J. Murtagh, D. O. Frimannsson, S. O. McDonnell, and D. F. O’Shea, Org. Biomol. Chem., 2010, 8, 522; CrossRef e) M. Tasior and D. F. O’Shea, Bioconjugate Chem., 2010, 21, 1130. CrossRef
14. W. Zhao and E. M. Carreira, Chem. Eur. J., 2006, 12, 7254. CrossRef
15. Q. Bellier, S. Pegaz, C. Aronica, B. L. Guennic, C. Andrqud, and O. Maury, Org. Lett., 2011, 13, 22. CrossRef
16. R. Gresser, M. Hummert, H. Hartmann, L. Leo, and M. Riede, Chem. Eur. J., 2011, 17, 2939. CrossRef
17. a) V. F. Donyagina, S. Shimizu, N. Kobayashi, and E. A. Lukyanets, Tetrahedron Lett., 2008, 49, 6152; CrossRef b) H. Lu, S. Shimizu, J. Mack, Z. Shen, and N. Kobayashi, Chem. Asian J., 2011, 6, 1026. CrossRef
18. A. Loudet, R. Bandichhor, L. Wu, and K. Burgess, Tetrahedron, 2008, 64, 3642. CrossRef
19. A. Palma, J. F. Gallagher, H. Muller-Bunz, J. Wolowska, E. J. L. KcInnes, and D. F. O’Shea, Dalton Trans., 2009, 273. CrossRef
20. T. S. Teets, D. V. Partyka, J. B. Updegraff III, and T. G. Gray, Inorg. Chem., 2008, 47, 2338. CrossRef
21. T. S. Teets, D. V. Partyka, A. J. Esswein, J. B. Updegraff III, M. Zeller, A. D. Hunter, and T. G. Gray, Inorg. Chem., 2007, 46, 6218. CrossRef
22. a) N. Abe and T. Gunji, Heterocycles, 2010, 82, 201; CrossRef b) N. Abe, ‘Recent Research Developments in Organic and Bioorganic Chemistry,’ ed. by S. G. Pandalai, 2001, 4, 14, Transworld Research Network, Trivandrum; c) N. Abe, ‘Trend in Heterocyclic Chemistry,’ 2001, 7, 25, Research Trends, Trivandrum; d) T. Nishiwaki and N. Abe, Heterocycles, 1981, 15, 547; CrossRef e) M. Kimura, Yuki Gosei Kagaku Kyokai Shi, 1981, 39, 4471. CrossRef
23. M. Oda, K. Ogura, N. C. Thanh, S. Kishi, S. Kuroda, K. Fujimori, T. Noda, and N. Abe, Tetrahedron Lett., 2007, 48, 4471. CrossRef
24. M. Oda, D. Miyawaki, N. Matsumoto, and S. Kuroda, Heterocycles, 2011, 82, 547. CrossRef
25. N. Abe, E. Hashimoto, H. Fujii, Y. Murakami, S. Tagashira, and A. Kakehi, Heterocycles, 2004, 63, 2341. CrossRef
26. M. Oda, A. Sugiyama, R. Takeuchi, Y. Fujiwara, R. Miyatake, T. Abe, and S. Kuroda, Eur. J. Org. Chem., 2012, 2231. CrossRef
27. E. Yoshioka, K. Koizumi, S. Yamazaki, H. Fujii, and N. Abe, Heterocycles, 2009, 78, 3065. CrossRef