Synthesis of near-infrared fluorescent 2,3-dicyano-6H-1,4-diazepines

Article abstract of DOI:10.1246/bcsj.78.316

A series of novel 5-(2-arylethenyl)-, 5-(4-arylbutadienyl)-, 5-(6-arylhexatrienyl)-, and 5-(8-octatetraenyl)-, 5-aryl-7-(2-arylethenyl)-, and 5,7-bis(2-arylethenyl)-2,3-dicyano-6H-1,4-diazepines were synthesized by the reactions of 2,3-dicyano-5-methyl-6H

Full text of DOI:10.1246/bcsj.78.316

316 Bull. Chem. Soc. Jpn., 78, 316–322 (2005)
Ó 2005 The Chemical Society of Japan
Synthesis of Near-Infrared Fluorescent 2,3-Dicyano-6H-1,4-diazepines
ꢀ
Emi Horiguchi, Kazumasa Funabiki, and Masaki Matsui
Department of Materials Science and Technology, Faculty of Engineering, Gifu University, Yanagido, Gifu 501-1193
Received August 5, 2004; E-mail: matsui@apchem.gifu-u.ac.jp
A series of novel 5-(2-arylethenyl)-, 5-(4-arylbutadienyl)-, 5-(6-arylhexatrienyl)-, and 5-(8-octatetraenyl)-, 5-aryl-
7-(2-arylethenyl)-, and 5,7-bis(2-arylethenyl)-2,3-dicyano-6H-1,4-diazepines were synthesized by the reactions of 2,3-
dicyano-5-methyl-6H-1,4-diazepines with aromatic aldehydes. These compounds showed intramolecular charge-transfer
chromophoric systems from the arylethenyl to the 2,3-dicyano-6H-diazepine moieties. The shifts in UV–vis absorption
bands were estimated by calculating the HOMO and LUMO energy levels. 2-(9-Julolidyl)ethenyl derivative showed the
most intense fluorescence. The 6-(9-julolidyl)-1,3,5-hexatrienyl and 8-(9-julolidyl)-1,3,5,7-octatetraenyl derivatives ex-
hibited the fluorescence maxima (Fmax) at 780 and 842 nm, respectively.
Near-infrared fluorescent dyes have potential applications as
R1 = Me
O
O
fluorescent labeling reagents, laser dyes, and biological
probes.1 Though several bathochromic fluorescence dyes such
as polymethines,2 cyanines,3 rhodamines,4 squaryliums,5 sty-
ryls,6 naphthalocyanines,7 and ytterbium(III) complexes8 have
been reported, they have either ionic structure or metal–com-
plex structure. To our knowledge, few bathochromic fluores-
cent dyes having a neutral structure are known. Only quaterry-
lene bisimides9 and pyrans10 have been reported. Therefore, it
is of significance to obtain neutral near-infrared fluorescent
compounds. In our series of studies on 2,3-dicyano-6H-1,4-di-
azepines, it was found that they showed Fmax around 600 nm
and that the introduction of a bulky substituent at the 6-posi-
tion enhanced fluorescence intensity in solid state.11 We report
herein the synthesis of near-infrared fluorescent 2,3-dicyano-
6H-1,4-diazepine derivatives.
Me
7
N
R1
Me 2a
NC
NC
NC
NC
NH2
NH2
i
5
N
R1
4a-d
1
R1 = Ar
R2
Me
iv
O
O
n
O
ii
H
5-14
iii
R1
2b-d
R2
R2
Me
H
N
N
NC
NC
n+1
N
N
NC
NC
NC
NC
+
R1
N
NH2
R1
O
R2
3b-d
15-24
15'-21'
1
1
2a, 4a: R = Me, 2b, 4b: R = Ph
Results and Discussion
1
1
2c, 4c: R = C H NMe (p), 2d, 4d: R = C H CN (p)
6
4
2
6 4
2,3-Dicyano-6H-1,4-diazepines 15–24 and 150–210 were
prepared as shown in Scheme 1. Diaminomaleonitrile
(DAMN, 1) reacted with acetylacetone (2a) in the presence
of oxalic acid to give 2,3-dicyano-5,7-dimethyl-6H-1,4-diaze-
pine (4a) in a 78% yield. Compound 1 also reacted with aroyl-
acetones 2b–d to afford the open-ring intermediates 3b–d,
which were cyclized in the presence of diphosphorus pentaox-
ide to provide 5-aryl-2,3-dicyano-7-methyl-6H-1,4-diazepines
4b–d in 27–67% yields. Then, the condensation of 4a–d with
aldehydes 5–14 gave the 5-(2-arylethenyl)-, 5-(4-aryl-1,3-bu-
tadienyl)-, 5-(6-aryl-1,3,5-hexatrienyl)-, and 5-(8-aryl-1,3,5,7-
octatetraenyl)-, 5-aryl-7-(2-arylethenyl), and 5,7-bis(2-aryl-
ethenyl)-2,3-dicyano-6H-1,4-diazepines 15–24 and 150–210.
The reactions of 4a–d with aromatic aldehydes 5–14 are
given in Table 1. When 4a reacted with a molar amount of un-
substituted and electron-deficient aromatic aldehydes 5 and 6
and heteroaromatic aldehydes 9, 10, and 11, 5,7-bis(arylethen-
yl) derivatives 150, 160, 190, 200, and 210 were obtained as main
products together with 5-(arylethenyl) derivatives 15, 16, 19,
20, and 21 (runs 1, 2, and 9–11). The yields of products in
the reaction of 4a with 5 and 6 were rather low, due to forma-
2
n = 0, 1, 2, 3 R = shown in Table 1
Scheme 1. Reagents and conditions: i) acetylacetone (1.0
mol. amt.), oxalic acid (trace), benzene, reflux, ii) aroyl-
acetones (1.0 mol. amt.), oxalic acid (trace), benzene, re-
flux, iii) diphosphorus pentaoxide, ethanol, reflux, iv)
2,3-dicyano-7-methyl-6H-1,4-diazepines (1.0 mol. amt.),
aldehydes (1ꢁ.0–2.0 mol. amt.), piperidine (a few drops),
benzene, 50 C–reflux.
tion of unidentified products which were not developed by col-
umn chromatography. Meanwhile, when 4a reacted with a mo-
lar amount of electron-donating aromatic aldehydes such as 7
and 8, 5-(2-arylethetnyl) derivatives 17 and 18a were obtained
as main products together with a trace amount of 5,7-bis(2-aryl-
ethenyl) derivatives 170 and 180a, respectively (runs 3 and 4).
These results suggest that the acidity of methyl-protons at both
the 5- and 7-positions in 4a is high enough to easily react with
aromatic aldehydes and that the product distribution depends
on the electronic effect of the aldehydes. Compound 4a reacted
with two molar amounts of 8 to give the 5,7-bis(2-arylethenyl)
Published on the web February 11, 2005; DOI 10.1246/bcsj.78.316

E. Horiguchi et al.
Bull. Chem. Soc. Jpn., 78, No. 2 (2005)
317
Table 1. Synthesis of 2,3-Dicyano-6H-1,4-diazepines
Starting materials
Products
Dicyanodiazepines
R1
Aldehydes
R2
Run
1
Compd
R1
R2
n
YieldaÞ/%
Compd
Compd
n
4a
4a
Me
5
0
15
150
16
Me
—
0
0
0
0
0
9
10
Cl
Cl
2
Me
6
0
Me
—
11
160
17
20
Cl
3
4
4a
4a
Me
Me
Me
50bÞ
NEt2
N
NEt2
7
8
0
0
20bÞ
50
N
N
N
N
N
18a
180a
18b
18c
Me
—
0
0
0
0
0
5cÞ
6
4a
4b
4c
Me
8
8
8
0
0
0
N
N
N
N
28
NMe2
NMe2
7
56
CN
CN
8
9
4d
4a
8
9
0
0
18d
38
Me
19
190
20
Me
0
0
0
0
6
50
7
S
S
—
Me
—
S
O
O
10
11
4a
4a
Me
Me
10
11
0
0
O
200
90
N
Et
21
Me
—
N
Et
0
0
6
210
N
Et
80
N
N
N
N
12
13
14
4a
4a
4a
Me
Me
Me
12
13
14
1
2
3
22
23
24
Me
Me
Me
1
2
3
10
18
16
N
N
a) Isolated yields. b) A trace amount of 5,7-bis(2-arylethenyl) derivative was also produced. c) Two molar amounts of 8 were used.
derivative 180a in a 50% yield (run 5). 5-Aryl-2,3-dicyano-7-
methyl-6H-1,4-diazepines 4b–d reacted with 8 to afford the
corresponding 5-aryl-7-(2-arylethenyl) derivatives 18b–d in
moderate yields (runs 6–8). Compound 4a also reacted with
olefinic aldehydes 12–14 to provide the 5-[4-(9-julolidyl)-
1,3-butadienyl)], 5-[6-(9-julolidyl)-1,3,5-hexatrienyl], and 5-
[8-(9-julolidyl)-1,3,5,7-octatetraenyl] derivatives 22–24 in
low yields along with formation of unidentified products which
were not developed by column chromatography (runs 12–14).
The UV–vis absorption and fluorescence spectra of 18a,
18c, and 180a are shown in Fig. 1. The ꢀmax of 18a was ob-
served at 519 nm with a molar absorption coefficient (") of
34800 dm3 molꢂ1 cmꢂ1. The Fmax was observed at 640 nm,
the Stokes shift being 121 nm (3643 cmꢂ1). The fluorescence
quantum yield was calculated to be 0.19. Compound 18c
showed two absorption bands in the visible region, the ꢀmax
being 399 and 530 nm. The Fmax was observed at 673 nm.
Compounds 180a showed the ꢀmax at 434, 494, and 568 nm.
The Fmax was observed at 726 nm. Interestingly, the fluores-
cence of 5-(2-arylethenyl) derivative 18a was most intense
among the 5-(2-arylethenyl), 5-aryl-7-(2-arylethenyl), and
5,7-bis(2-arylethenyl) derivatives 18a, 18c, and 180a.
The UV–vis absorption and fluorescence spectra of 18a, 22,
23, and 24 are depicted in Fig. 2. As expected, the ꢀmax caused
a bathochromic shift from 519 to 580 nm with the expansion of
olefinic unit. The bathochromic displacement by ca. 10–30 nm
was observed for the expansion of one ethylene unit. The Fmax
also showed a bathochromic shift from 640 to 842 nm. A shift

318 Bull. Chem. Soc. Jpn., 78, No. 2 (2005)
Near-Infrared Fluorescent Diazepins
1.0
1.0
4000
4000
FL
UV-Vis
18a
FL
UV-Vis
0.8
0.6
0.4
18a
18c
18a
0.8
0.6
0.4
0.2
0
3000
2000
3000
2000
1000
0
18'a
18c
23
22
18a
24
22
24 (x 10)
23
1000
0
0.2
0
18'a
300 400 500 600 700 800 900
300 400 500 600 700 800 900
Wavelength / nm
Wavelength / nm
Fig. 2. UV–vis absorption spectra of 18a, 22, 23, and 24.
Solid and dotted lines represent UV–vis absorption and
fluorescence spectra, respectively. Measured on 1 ꢃ 10ꢂ5
Fig. 1. UV–vis absorption and fluorescence spectra of 18a,
18c, and 180a. Solid and dotted lines represent UV–vis ab-
sorption and fluorescence spectra, respectively. Measured
ꢁ
mol dmꢂ3 of substrate at 25 C.
ꢁ
on 1 ꢃ 10ꢂ5 mol dmꢂ3 of substrate at 25 C.
Table 2. Observed and Calculated UV–Vis Absorption and Fluorescence Spectra of 2,3-Dicyano-6H-1,4-diazepines
ObsdaÞ
Stokes shift
nm (cmꢂ1
Calcd
Run
Compd
ꢀmax ("max
)
Fmax
RFI
<1
<1
26
ꢀ
max/nm(fbÞ
)
CI component
nm
nm
)
1
2
3
4
5
15
16
17
18a
18b
360 (28600)
364 (35200)
491 (40400)
519 (34800)
540 (34800)
412 (11300)
437
437
601
640
684
77 (4895)
73 (4590)
110 (3728)
121 (3643)
144 (3899)
331 (0.64)
331 (0.68)
349 (1.01)
352 (1.03)
360 (0.87)
308 (0.50)
HOMO to LUMO (83%)
HOMO to LUMO (84%)
HOMO to LUMO (75%)
HOMO to LUMO (72%)
HOMO to LUMO (71%)
HOMO to LUMO+1 (45%)
HOMOꢂ1 to LUMO (22%)
HOMO to LUMO (72%)
HOMO to LUMO+1 (48%)
HOMOꢂ1 to LUMO (18%)
HOMO to LUMO (74%)
HOMO to LUMO+1 (35%)
HOMOꢂ1 to LUMO (18%)
HOMO to LUMO (69%)
HOMO to LUMO+1 (54%)
HOMOꢂ1 to LUMO (43%)
HOMOꢂ2 to LUMO+1 (23%)
HOMO to LUMO (87%)
HOMO to LUMO (89%)
HOMO to LUMO (71%)
HOMO to LUMO (80%)
HOMO to LUMO (77%)
HOMO to LUMO (74%)
100
58
6
7
8
18c
18d
180a
530 (31500)
399 (39000)
673
725
726
143 (4009)
154 (3720)
158 (3832)
16
2
361 (0.78)
310 (0.79)
571 (40200)
445 (19500)
377 (1.19)
317 (0.38)
568 (28800)
494 (34000)
434 (48900)
7
368 (0.66)
321 (1.49)
306 (0.21)
9
10
11
12
13
14
19
20
21
22
23
24
392 (30800)
392 (36300)
443 (28800)
536 (35900)
568 (38300)
580 (44900)
436
438
556
705
780
842
44 (2574)
46 (2679)
113 (4587)
169 (4473)
212 (4785)
262 (5365)
<1
<1
2
57
14
1
349 (0.85)
357 (0.91)
344 (1.05)
385 (1.64)
397 (2.02)
407 (2.40)
a) Measured in chloroform at the concentration of 1 ꢃ 10ꢂ5 mol dmꢂ3. b) Oscillator strength.
of Fmax ca. 40–80 nm was observed for the expansion of one
ethylene unit. The Stokes shift of 24 was very large: 262 nm
(5365 cmꢂ1). The fluorescence intensity decreased by intro-
ducing a flexible olefinic moiety, in the order: 18a > 22 >
23 > 24. Thus, compounds 23 and 24 showed the Fmax in
the near-infrared region.
The UV–vis absorption and fluorescence spectra of the other
derivatives are indicated in Table 2. The ꢀmax of 5-(2-aryl-
ethenyl) derivatives having an electron-donating dialkylamino
group 17 and 18a were observed at 491 and 519 nm, respec-
tively; they are much more bathochromic than the unsubstitut-
ed and electron-withdrawing ones 15 (360 nm) and 16 (364)
(runs 1–4). Heteroaromatic ethenyl derivatives 19 (392), 20
(392), and 21 (443) were more bathochromic than the styryl
derivative 15 (360) (runs 1 and 9–11).
5-Aryl-7-(2-arylethenyl) derivatives were slightly more
bathochromic in the following order: 18d (571) > 18b (540),
18c (530), 18a (519) (runs 4–7). Thus, the introduction of an
electron-withdrawing group into the phenyl ring at the 5-posi-
tion caused a slight bathochromic shift. 5,7-Bis(2-arylethenyl)
derivative 180a (568) was more bathochromic than the 5-(2-
arylethenyl) derivative 18a (519) (runs 4 and 8).

E. Horiguchi et al.
Bull. Chem. Soc. Jpn., 78, No. 2 (2005)
319
-0.5
-1.0
-0.7951
-0.8147
-0.8387
-0.8996
-0.9120
-0.9906
-1.0488
Optimized structure
LUMO
HOMO
-7.0
-7.5
-8.0
-7.3167
-7.4730
-7.5413
-7.7195
-7.7534
-8.0039 -8.0708
Difference in electron density
15
16
17
18a 19
20
21
Gray: Decrease in electron density
Black: Increase in electron density
Fig. 4. Energy levels of 15–21.
Fig. 3. Schematic representation of optimized structure,
HOMO, LUMO, and difference in electron-density be-
tween ground and first excited state in 18a.
-0.5
-0.7587
-0.7951
5-(2-Arylethenyl) derivative 18a showed more intense fluo-
rescence than the 5-aryl-7-(2-arylethenyl) and 5,7-bis(2-aryl-
ethenyl) derivatives 18b–d and 180a (runs 4–8). The fluores-
cence intensity of 5-[2-(9-julolidyl)ethenyl] derivative 18a
was highest among the 5-(2-arylethenyl) and 5-(2-heteroaryl-
ethenyl) derivatives 15–21 (runs 1–4 and 9–11).
-1.0
-0.7996
-0.8530
-1.1234
To explain the absorption spectra of 2,3-dicyano-6H-1,4-di-
azepines, we carried out semi-empirical MO calculations using
the WinMOPAC 3.0 package (Fujitsu, Chiba, Japan).12 Geom-
etry optimizations were performed using the AM1 method.
Then the absorption spectra were calculated with the INDO/
S method. In the calculation, the parameters of the sulfur atom
(Es ¼ 21:02, Ep ¼ 10:97, Bsp ¼ 13:5, G ¼ 10:01) were add-
ed.13 One hundred configurations were considered for the con-
figuration interaction.
-7.0
-7.5
-7.1921
-7.2363
-7.2857
-7.3167
-7.3426
18a
18b
18'a
18c
18d
Fig. 5. Energy levels of 18a, 18b, 18c, 18d, and 180a.
The schematic representation of optimized geometry,
HOMO, LUMO, and the difference in electron density be-
tween the ground and first excited states in 18a are shown in
Fig. 3. Electrons are located around the julolidyl moiety in
the HOMO energy level due to its electron-donating nature.
Meanwhile electrons are located around the diazepine ring in
the LUMO energy level because of its electron-deficient prop-
erty. The difference in electron density clearly indicates that
the 5-(2-arylethenyl)-2,3-dicyano-6H-1,4-diazepines have an
intramolecular charge-transfer chromophoric system from the
2-arylethenyl to 2,3-dicyano-6H-diazepine moieties.
The results of calculated UV–vis absorption bands are also
indicated in Table 2. 5-(2-Arylethenyl), 5-(4-aryl-1,3-buta-
dienyl), 5-(6-aryl-1,3,5-hexatrienyl), and 5-(8-aryl-1,3,5,7-oc-
tatetraenyl) derivatives 15–24 showed the first absorption band
in the visible region. These absorption bands were attributed to
the HOMO to LUMO transition (runs 1–4 and 9–14). Mean-
while, the first and second absorption bands in the 5-aryl-7-
(2-arylethenyl) derivatives 18b, 18c, and 18d were character-
ized as the HOMO to LUMO and a mixture of HOMO to
next LUMO (LUMO+1) and next HOMO (HOMOꢂ1) to
LUMO transition, respectively (runs 5–7).
tives 15–21 are shown in Fig. 4. The bathochromic shift in
17 and 18a, compared with 15 and 16, can be ascribed to large
destabilization of HOMO energy level due to the introduction
of an electron-donating dialkylamino group into the chromo-
phore. The bathochromic shifts in the 5-[2-(heteroaryl)ethen-
yl]-7-methyl derivatives 19, 20, and 21, compared with that
in the styryl derivative 15, were also attributed to destabiliza-
tion of the HOMO energy level because of the electron-suffi-
cient heteroaromatic moiety.
The calculated energy levels of 5-(2-arylethenyl), 5-aryl-7-
(2-arylethenyl), and 5,7-bis(2-arylethenyl) derivatives 18a–
18d and 180a are shown in Fig. 5. The bathochromic shift in
the UV–vis absorption band of 18b and 180a, compared to that
of 18a, can be explained by slight destabilization of HOMO
and stabilization of LUMO energy levels, due to the expansion
of the ꢁ-conjugated system. The hypsochromic shift in 18c can
be ascribed to destabilization of LUMO energy level that
comes from the introduction of an electron-donating dimethyl-
amino group into the phenyl moiety. On the other hand, the
introduction of an electron-withdrawing cyano group in 18d
brought about a large stabilization of the LUMO level to give
the bathochromic shift.
The calculated energy levels for 5-(2-arylethenyl) deriva-
The calculated energy levels of 5-[2-(9-julolidyl)ethenyl],

320 Bull. Chem. Soc. Jpn., 78, No. 2 (2005)
Near-Infrared Fluorescent Diazepins
quinolizin-9-yl)propenal (12),18 5-(2,3,6,7-tetrahydro-1H,5H-ben-
zo[ij]quinolizin-9-yl)-2,4-pentadienal (13),18 and 7-(2,3,6,7-tetra-
hydro-1H,5H-benzo[ij]quinolinin-9-yl)-2,4,6-heptatrienal (14)18
were prepared as described in the literature.
-0.5
-0.7951
-1.0
Synthesis of 5-Aryl-2,3-dicyano-7-methyl-6H-diazepines 4c
and 4d. To a benzene solution (20 cm3) of DAMN 1 (1.08 g,
10 mmol) were added oxalic acid (50 mg) and an aroylacetone
2c or 2d (10 mmol). The mixture was refluxed for 10 h in a system
equipped with a Dean–Stark trap. After the solvent was removed,
the product was isolated by silica gel column chromatography (di-
chloromethane/ethyl acetate = 10/1). The open-ring intermedi-
ates 3c and 3d were refluxed again in the presence of diphospho-
rus pentaoxide (500 mg) in ethanol (20 cm3) for 13 h. After the
reaction was completed, the solvent was evaporated. The residual
brown syrup was treated with water and extracted with chloro-
form. After evaporation of the solvent in vacuo, the product was
isolated by silica gel column chromatography (dichloromethane/
ethyl acetate = 20/1) and recrystallized from benzene. The phys-
ical and spectral data are shown below.
-1.0342
-1.1222
-1.1863
-6.8977
-7.0
-7.0021
-7.1257
-7.3167
-7.5
18a
22
23
24
Fig. 6. Energy levels of 18a, 22, 23, and 24.
5-[4-(9-julolidyl)-1,3-butadienyl], 5-[6-(9-julolidyl)-1,3,5-hex-
atrienyl], and 5-[8-(9-julolidyl)-1,3,5,7-octatetraenyl] deriva-
tives 18a, 22, 23, and 24 are shown in Fig. 6. It is clear that
expansion of the olefinic unit results in the stabilization of
LUMO and destabilization of HOMO energy levels to cause
the bathochromic shift.
2,3-Dicyano-5-[4-(dimethylamino)phenyl]-7-methyl-6H-1,4-
diazepine (4c): Yield 67%; mp 204–205 ꢁC; 1H NMR (CDCl3) ꢂ
1.81 (br s, 1H), 2.14 (s, 3H), 3.11 (s, 6H), 4.89 (br s, 1H), 6.70 (d,
J ¼ 7:3 Hz, 2H), 7.89 (d, J ¼ 7:3 Hz, 2H); EIMS (70 eV) m=z (rel
intensity) (Mþ, 93), 276 (42), 146 (100), 145 (44), 77 (34).
2,3-Dicyano-5-(4-cyanophenyl)-7-methyl-6H-1,4-diazepine
1
(4d): Yield 27%; H NMR (CDCl3) ꢂ 1.94 (br s, 1H), 2.26 (s,
Conclusion
3H), 5.03 (br s, 1H), 7.83 (d, J ¼ 8:1 Hz, 2H), 8.13 (d, J ¼ 8:1
Hz, 2H). This product was used without further purification.
Reaction of 2,3-Dicyano-6H-1,4-diazepines 4 with Alde-
hydes 5–14. To a benzene solution (15 cm3) of 4 (1 mmol) were
added piperidine (a few drops) and aldehydes 5–14 (1 mmol). The
mixture was stirred (15: 50 ꢁC to reflux for 3 d; 16: 70 ꢁC for 10 h;
17, 18a, 180a, 21: reflux for 6 h; 18b: reflux for 8 h; 18c: reflux for
40 h; 18d: 50 ꢁC to reflux for 28 h; 19, 20: 50 ꢁC for 24 h; 22, 23,
24: 50 ꢁC for 20 h). After the reaction was completed, the solvent
was removed. The product was isolated by silica gel column chro-
matography (15, 16, 17, 18a, 19, 20, 21, 22, 23, 24: toluene/ethyl
acetate = 15/1; 180a, 18b, 18c, 18d: dichloromethane/ethyl ace-
tate = 20/1) and recrystallized from benzene. The physical and
spectral data are shown below.
2,3-Dicyano-5-methyl-7-styryl-6H-1,4-diazepine (15): Mp
177–179 ꢁC (dec); 1H NMR (CDCl3) ꢂ 1.82 (br s, 1H), 2.27 (s,
3H), 4.69 (br s, 1H), 6.93 (d, J ¼ 16:3 Hz, 1H), 7.44–7.45 (m,
3H), 7.53 (d, J ¼ 16:3 Hz, 1H), 7.58–7.59 (m, 2H); EIMS (70
eV) m=z (rel intensity) 260 (Mþ, 43), 259 (100), 258 (55), 219
(45), 218 (43), 217 (37), 128 (50), 77 (35), 51 (42). Found: C,
73.53; H, 4.83; N, 21.54%. Calcd for C16H12N4: C, 73.83; H,
4.65; N, 21.52%.
2,3-Dicyano-5,7-distyryl-6H-1,4-diazepine (150): Mp 276–
278 ꢁC (dec); 1H NMR (CDCl3) ꢂ 1.87 (br s, 1H), 4.99 (br s,
1H), 6.89 (d, J ¼ 16:1 Hz, 2H), 7.41–7.42 (m, 6H), 7.54–7.56
(m, 4H), 7.61 (d, J ¼ 16:1 Hz, 2H); EIMS (70 eV) m=z (rel inten-
sity) 348 (Mþ, 76), 347 (100), 129 (40), 128 (91), 127 (53), 77
(35), 51 (32).
5-(4-Chlorostyryl)-2,3-dicyano-7-methyl-6H-1,4-diazepine
(16): Mp 185–187 ꢁC (dec); 1H NMR (CDCl3) ꢂ 1.83 (br s, 1H),
2.27 (s, 3H), 4.66 (br s, 1H), 6.88 (d, J ¼ 16:2 Hz, 1H), 7.41 (d,
J ¼ 8:5 Hz, 2H), 7.48 (d, J ¼ 16:2 Hz, 1H), 7.52 (d, J ¼ 8:5 Hz,
2H); EIMS (70 eV) m=z (rel intensity) 296 (Mþ + 2, 18), 294
(Mþ, 52), 293 (100), 253 (36), 128 (62), 127 (38). Found: C,
65.16; H, 3.85; N, 19.15%. Calcd for C16H11ClN4: C, 65.20; H,
3.76; N, 19.01%.
We have synthesized a series of neutral fluorescent 2,3-di-
cyano-6H-1,4-diazepines. These compounds showed an intra-
molecular charge-transfer chromophoric system. Therefore,
as stronger was the electron-donating ability at the 5-(2-aryl-
ethenyl) moiety, the ꢀmax and Fmax could show more batho-
chromic shift. The expansion of ꢁ-conjugated system caused
bathochromic shifts in ꢀmax and Fmax because of destabiliza-
tion of HOMO and stabilization of LUMO energy levels. 5-
(2-Arylethenyl) derivative showed more intense fluorescence
than the 5-aryl-7-(2-arylethenyl) and 5,7-bis(2-arylethenyl) de-
rivatives. The fluorescence of 6-[2-(9-julolidyl)ethenyl] deriv-
ative was most intense among the 5-(2-arylethenyl) deriva-
tives. The 5-[6-(9-julolidyl)-1,3,5-hexatrienyl] and 5-[8-(9-
julolidyl)-1,3,5,7-octatetraenyl] derivatives showed the Fmax
in the near-infrared region at 780 and 842 nm, respectively.
Experimental
Instruments.
Melting points were measured with a
Yanagimoto MP-S2 micro-melting-point apparatus. EIMS spectra
were recorded on a Shimadzu QP-1000 spectrometer. NMR spec-
tra were obtained by a Varian Inova 400 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 F-4500 spectrophotometers, respectively.
Materials. Diaminomaleonitrile (DAMN, 1) and 9-ethyl-3-
carbazolecarbaldehyde (11) were purchased from Sigma-Aldrich.
Acetylacetone (2a), 1-phenyl-1,3-butanedione (2b), benzaldehyde
(5), 4-chlorobenzaldehyde (6), 4-(diethylamino)benzaldehyde (7),
2-thiophenecarbaldehyde (9), 2-furaldehyde (10) were purchased
from Tokyo Kasei Co., Ltd. 4-(Dimethylamino)benzoylacetone
(2c),14 4-(cyanobenzoyl)acetone (2d),14 2,3-dicyano-5,7-dimeth-
yl-6H-1,4-diazepine (4a),15 2,3-dicyano-7-methyl-5-phenyl-6H-
1,4-diazepine (4b),16 2,3,6,7-tetrahydro-1H,5H-benzo[ij]quinoli-
zine-9-carbaldehyde (8),17 3-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]-

E. Horiguchi et al.
Bull. Chem. Soc. Jpn., 78, No. 2 (2005)
321
5,7-Bis(4-cꢁhlorostyryl)-2,3-dicyano-6H-1,4-diazepine (160):
75.67; H, 5.23; N, 18.64%. Calcd for C28H22N6: C, 76.00; H,
5.01; N, 18.99%.
1
Mp 267–269 C (dec); H NMR (CDCl3) ꢂ 1.85 (br s, 1H), 4.85
(br s, 1H), 6.83 (d, J ¼ 16:1 Hz, 2H), 7.39 (d, J ¼ 8:7 Hz, 4H),
7.47 (d, J ¼ 8:7 Hz, 4H), 7.54 (d, J ¼ 16:1 Hz, 2H); EIMS (70
eV) m=z (rel intensity) 420 (Mþ + 4, 13), 418 (Mþ + 2, 64),
417 (88), 416 (Mþ, 89), 415 (85), 128 (100).
2,3-Dicyano-5-[4-(diethylamino)styryl]-7-methyl-6H-1,4-di-
azepine (17): Mp 222–224 ꢁC (dec); 1H NMR (CDCl3) ꢂ 1.21 (t,
J ¼ 7:2 Hz, 6H), 1.59 (s, 3H), 1.83 (br s, 1H), 3.43 (q, J ¼ 7:2 Hz,
4H), 4.57 (br s, 1H), 6.67 (d, J ¼ 15:9 Hz, 1H), 6.68 (d, J ¼ 8:7
Hz, 2H), 7.44 (d, J ¼ 15:9 Hz, 1H), 7.45 (d, J ¼ 8:7 Hz, 2H);
EIMS (70 eV) m=z (rel intensity) 331 (Mþ, 57), 317 (85), 316
(100). Found: C, 72.52; H, 6.53; N, 21.38%. Calcd for C20H21N5:
C, 72.48; H, 6.39; N, 21.13%.
2,3-Dicyano-5-methyl-7-[2-(2-thienyl)ethenyl]-6H-1,4-diaze-
pine (19): Mp 190–192 ꢁC (dec); 1H NMR (CDCl3) ꢂ 1.84 (br s,
1H), 2.27 (s, 3H), 4.57 (br s, 1H), 6.67 (d, J ¼ 15:7 Hz, 1H), 7.13
(dd, J ¼ 4:7, 3.6 Hz, 1H), 7.38 (d, J ¼ 3:6 Hz, 1H), 7.49 (d, J ¼
4:7 Hz, 1H), 7.68 (d, J ¼ 15:7 Hz, 1H); EIMS (70 eV) m=z (rel
intensity) 266 (Mþ, 62), 265 (100), 225 (36), 135 (46), 91 (45).
Found: C, 63.13; H, 3.90; N, 21.21%. Calcd for C14H10N4S: C,
63.14; H, 3.78; N, 21.04%.
2,3-Dicyano-5,7-bis[2-(2-thienyl)ethenyl]-6H-1,4-diazepine
ꢁ
1
(190): Mp 287–289 C (dec); H NMR (DMSO-d6) ꢂ 2.10 (br s,
1H), 5.23 (br s, 1H), 6.79 (d, J ¼ 16:0 Hz, 2H), 7.19 (dd, J ¼ 5:0,
3.6 Hz, 2H), 7.62 (d, J ¼ 3:6 Hz, 2H), 7.80 (d, J ¼ 5:0 Hz, 2H),
8.26 (d, J ¼ 16:0 Hz, 2H); EIMS (70 eV) m=z (rel intensity) 360
(Mþ, 24), 359 (23), 135 (22), 91 (100).
2,3-Dicyano-5-methyl-7-[2-(2,3,6,7-tetrahydro-1H,5H-ben-
zo[ij]quinolizin-9-yl)ethenyl]-6H-1,4-diazepine (18a): Mp >
ꢁ
1
300 C; H NMR (CDCl3) ꢂ 1.80 (br s, 1H), 1.96 (quin, J ¼ 6:0
Hz, 4H), 2.18 (s, 3H), 2.74 (t, J ¼ 6:0 Hz, 4H), 3.29 (t, J ¼ 6:0
Hz, 4H), 4.51 (br s, 1H), 6.61 (d, J ¼ 15:9 Hz, 1H), 7.04 (s,
2H), 7.35 (d, J ¼ 15:9 Hz, 1H); 13C NMR (CDCl3) 21.4, 25.7,
27.7, 44.2, 50.1, 115.4, 115.7, 117.9, 120.8, 121.1, 121.4, 124.6,
128.4, 146.2, 146.6, 149.9, 155.4; EIMS (70 eV) m=z (rel intensi-
ty) 355 (Mþ, 100), 354 (32), 303 (20); IR (KBr) 2217 cmꢂ1 (CN).
Found: C, 73.85; H, 6.13; N, 19.44%. Calcd for C22H21N5: C,
74.34; H, 5.96; N, 19.70%.
2,3-Dicyano-5-[2-(2-furyl)ethenyl]-7-methyl-6H-1,4-diaze-
pine (20): Mp 174–176 ꢁC (dec); 1H NMR (CDCl3) ꢂ 1.84 (br s,
1H), 2.26 (s, 3H), 4.55 (br s, 1H), 6.56 (dd, J ¼ 3:4, 1.4 Hz, 1H),
7.33 (d, J ¼ 15:8 Hz, 1H), 7.57 (d, J ¼ 1:4 Hz, 1H), 7.73 (d, J ¼
15:8 Hz, 1H), 7.79 (d, J ¼ 3:4 Hz, 1H); EIMS (70 eV) m=z (rel
intensity) 250 (Mþ, 48), 209 (49), 180 (100), 179 (69), 91 (58),
65 (62), 63 (57), 51 (69). Found: C, 66.91; H, 4.15; N, 22.38%.
Calcd for C14H10N4O: C, 67.19; H, 4.03; N, 22.39%.
2,3-Dicyano-5,7-bis[2-(2-furyl)ethenyl]-6H-1,4-diazepine
ꢁ
1
2,3-Dicyano-5,7-bis[2-(2,3,6,7-tetrahydro-1H,5H-benzo[ij]-
(200): Mp 281–283 C (dec); H NMR (DMSO-d6) ꢂ 2.09 (br s,
1H), 5.24 (br s, 1H), 6.69 (dd, J ¼ 3:2, 1.4 Hz, 2H), 6.75 (d, J ¼
16:1 Hz, 2H), 7.05 (d, J ¼ 3:2 Hz, 2H), 7.89 (d, J ¼ 16:1 Hz, 2H),
7.91 (d, J ¼ 1:4 Hz, 2H); EIMS (70 eV) m=z (rel intensity) 328
(Mþ, 65), 271 (38), 180 (72), 179 (47), 91 (95), 65 (100), 63
(47), 51 (55).
quinolizin-9-yl)ethenyl]-6H-1,4-diazepine (180a):
Mp > 300
1
ꢁC; H NMR (CDCl3) ꢂ 1.80 (br s, 1H), 1.95 (quin, J ¼ 6:0 Hz,
8H), 2.71 (t, J ¼ 6:0 Hz, 8H), 3.26 (t, J ¼ 6:0 Hz, 8H), 4.76 (br
s, 1H), 6.58 (d, J ¼ 15:8 Hz, 2H), 6.98 (s, 4H), 7.36 (d, J ¼
15:8 Hz, 2H); 13C NMR (CDCl3) 21.5, 27.8, 38.9, 50.2, 116.6,
118.3, 121.2, 121.6, 122.5, 128.2, 144.7, 145.8, 151.5; EIMS
(70 eV) m=z (rel intensity) 538 (Mþ, 14), 355 (21), 186 (100);
IR (KBr) 2220 cmꢂ1 (CN). Found: C, 77.67; H, 6.50; N,
15.53%. Calcd for C35H34N6: C, 78.04; H, 6.36; N, 15.60%.
2,3-Dicyano-5-phenyl-7-[2-(2,3,6,7-tetrahydro-1H,5H-ben-
zo[ij]quinolizin-9-yl)ethenyl]-6H-1,4-diazepine (18b): Mp >
300 ꢁC; 1H NMR (CDCl3) ꢂ 1.93 (br, 1H), 1.93 (quin, J ¼ 6:0
Hz, 4H), 2.70 (t, J ¼ 6:0 Hz, 4H), 3.26 (t, J ¼ 6:0 Hz, 4H),
5.23 (br, 1H), 6.53 (d, J ¼ 15:6 Hz, 1H), 6.95 (s, 2H), 7.42 (d, J ¼
15:6 Hz, 1H), 7.44–7.52 (m, 3H), 7.96–7.99 (m, 2H); EIMS (70
eV) m=z (rel intensity) 417 (Mþ, 100), 416 (39), 186 (58). Found:
C, 77.45; H, 5.73; N, 16.46%. Calcd for C27H23N5: C, 77.67; H,
5.55; N, 16.77%.
2,3-Dicyano-5-[2-(9-ethyl-3-carbazolyl)ethenyl]-7-methyl-
6H-1,4-diazepine (21): Mp 222–224 ꢁC (dec); 1H NMR (CDCl3)
ꢂ 1.47 (t, J ¼ 7:3 Hz, 3H), 1.88 (br s, 1H), 2.29 (s, 3H), 4.41 (q,
J ¼ 7:3 Hz, 2H), 4.76 (br s, 1H), 6.99 (d, J ¼ 16:0 Hz, 1H), 7.31
(t, J ¼ 7:8 Hz, 1H), 7.45 (d, J ¼ 7:8 Hz, 2H), 7.53 (t, J ¼ 7:8 Hz,
1H), 7.74 (d, J ¼ 8:2 Hz, 1H), 7.79 (d, J ¼ 16:0 Hz, 1H), 8.12 (d,
J ¼ 8:2 Hz, 1H), 8.34 (s, 1H); EIMS (70 eV) m=z (rel intensity)
377 (Mþ, 100), 376 (66), 362 (32), 57 (31). Found: C, 76.32; H,
5.28; N, 18.26%. Calcd for C24H19N5: C, 76.37; H, 5.07; N,
18.55%.
2,3-Dicyano-5,7-bis[2-(9-ethyl-3-carbazolyl)ethenyl]-6H-1,4-
ꢁ
1
diazepine (210): Mp 275–277 C (dec); H NMR (DMSO-d6) ꢂ
1.21 (t, J ¼ 7:1 Hz, 6H), 2.09 (br, 1H), 4.34 (q, J ¼ 7:1 Hz, 4H),
5.47 (br, 1H), 7.17 (d, J ¼ 16:5 Hz, 2H), 7.23 (t, J ¼ 8:2 Hz, 2H),
7.47 (t, J ¼ 8:2 Hz, 2H), 7.57 (d, J ¼ 8:2 Hz, 4H), 7.92 (d, J ¼
7:7 Hz, 2H), 8.16 (d, J ¼ 7:7 Hz, 2H), 8.37 (d, J ¼ 16:5 Hz,
2H), 8.66 (s, 2H); EIMS (70 eV) m=z (rel intensity) 582 (Mþ,
3), 377 (22), 246 (51), 231 (100), 208 (48), 219 (21).
2,3-Dicyano-5-[4-(dimethylamino)phenyl]-7-[2-(2,3,6,7-tet-
rahydro-1H,5H-benzo[ij]quinolizin-9-yl)ethenyl]-6H-1,4-di-
azepine (18c): Mp > 300 ꢁC; 1H NMR (CDCl3) ꢂ 1.82 (br, 1H),
1.94 (quin, J ¼ 6:0 Hz, 4H), 2.71 (t, J ¼ 6:0 Hz, 4H), 3.06 (s,
6H), 3.24 (t, J ¼ 6:0 Hz, 4H), 5.14 (br, 1H), 6.54 (d, J ¼ 15:8
Hz, 1H), 6.65 (dd, J ¼ 7:1, 2.1 Hz, 2H), 6.95 (s, 2H), 7.35 (d, J ¼
15:8 Hz, 1H), 7.89 (dd, J ¼ 7:1, 2.1 Hz, 2H); EIMS (70 eV) m=z
(rel intensity) 460 (Mþ, 41), 224 (16), 196 (26), 186 (100). Found:
C, 75.41; H, 6.22; N, 17.90%. Calcd for C29H28N6: C, 75.63; H,
6.13; N, 18.25%.
2,3-Dicyano-5-(4-cyanophenyl)-7-[2-(2,3,6,7-tetrahydro-1H,
5H-benzo[ij]-quinolizin-9-yl)ethenyl]-6H-1,4-diazepine (18d):
Mp > 300 ꢁC; 1H NMR (CDCl3) ꢂ 1.73 (br s, 1H), 1.95 (quin, J ¼
6:0 Hz, 4H), 2.72 (t, J ¼ 6:0 Hz, 4H), 3.29 (t, J ¼ 6:0 Hz, 4H),
5.17 (br s, 1H), 6.50 (d, J ¼ 15:6 Hz, 1H), 6.97 (s, 2H), 7.47
(d, J ¼ 15:6 Hz, 1H), 7.76 (dd, J ¼ 8:7, 1.8 Hz, 2H), 8.09 (dd,
J ¼ 8:7, 1.8 Hz, 2H); EIMS (70 eV) m=z (rel intensity) 442
(Mþ, 100), 221 (32), 218 (50), 186 (80), 128 (35). Found: C,
2,3-Dicyano-5-methyl-7-[4-(2,3,6,7-tetrahydro-1H,5H-ben-
(22):
zo[ij]quinolizꢁin-9-yl)-1,3-butadienyl]-6H-1,4-diazepine
1
Mp 220–223 C (dec); H NMR (CDCl3) ꢂ 1.80 (br s, 1H), 1.96
(quin, J ¼ 6:0 Hz, 4H), 2.21 (s, 3H), 2.74 (t, J ¼ 6:0 Hz, 4H),
3.27 (t, J ¼ 6:0 Hz, 4H), 4.50 (br s, 1H), 6.25 (d, J ¼ 15:4 Hz,
1H), 6.72 (dd, J ¼ 15:4, 11.0 Hz, 1H), 6.87 (d, J ¼ 15:4 Hz,
1H), 6.96 (s, 2H), 7.35 (dd, J ¼ 15:4, 11.0 Hz, 1H); EIMS (70
eV) m=z (rel intensity) 381 (Mþ, 100), 355 (44), 186 (39), 172
(30), 91 (31). Found: C, 75.32; H, 6.37; N, 18.04%. Calcd for
C24H23N5: C, 75.56; H, 6.08; N, 18.36%.
2,3-Dicyano-5-methyl-7-[6-(2,3,6,7-tetrahydro-1H,5H-ben-
zo[ij]quinolizꢁin-9-yl)-1,3,5-hexatrienyl]-6H-1,4-diazepine (23):
1
Mp 217–220 C (dec); H NMR (CDCl3) ꢂ 1.80 (br s, 1H), 1.96

322 Bull. Chem. Soc. Jpn., 78, No. 2 (2005)
Near-Infrared Fluorescent Diazepins
(quin, J ¼ 5:9 Hz, 4H), 2.20 (s, 3H), 2.74 (t, J ¼ 5:9 Hz, 4H),
3.23 (t, J ¼ 5:9 Hz, 4H), 4.49 (br s, 1H), 6.25 (d, J ¼ 15:0 Hz,
1H), 6.39 (dd, J ¼ 15:0, 11.4 Hz, 1H), 6.67–6.69 (m, 2H),
6.81–6.87 (m, 1H), 6.92 (s, 2H), 7.23–7.29 (m, 1H); EIMS (70
eV) m=z (rel intensity) 407 (Mþ, 60), 406 (46), 405 (100), 173
(44), 172 (30). Found: C, 76.32; H, 6.37; N, 17.04%. Calcd for
C26H25N5: C, 76.63; H, 6.18; N, 17.19%.
8
Y. Kawamura, Y. Wada, M. Iwamura, T. Kitamura, and S.
Yanagida, Chem. Lett., 2002, 280.
H. Langhals, G. Schonmann, and L. Feiler, Tetrahedron
Lett., 36, 6423 (1995).
9
10 S. Kobayashi, S. Matsumura, N. Taniguchi, Y. Yoshinaga,
T. Sudo, H. Morishita, and T. Kaneko, EP 0 627 426 A1; Chem.
Abstr., 123, 70471 (1995).
2,3-Dicyano-5-methyl-7-[8-(2,3,6,7-tetrahydro-1H,5H-ben-
zo[ij]quinolizin-9-yl)-1,3,5,7-octatetraenyl]-6H-1,4-diazepine
11 E. Horiguchi, S. Matsumoto, K. Funabiki, and M. Matsui,
Chem. Lett., 2004, 170.
ꢁ
1
(24): Mp 218–220 C (dec); H NMR (CDCl3) ꢂ 1.78 (br, 1H),
1.96 (quin, J ¼ 6:0 Hz, 4H), 2.20 (s, 3H), 2.73 (t, J ¼ 6:0 Hz,
4H), 3.20 (t, J ¼ 6:0 Hz, 4H), 4.47 (br, 1H), 6.26 (d, J ¼ 15:3
Hz, 1H), 6.34–6.40 (m, 2H), 6.56–6.59 (m, 1H), 6.64–6.67 (m,
2H), 6.78 (dd, J ¼ 14:2, 11.2 Hz, 1H), 6.90 (s, 2H), 7.24 (dd,
J ¼ 15:3, 11.2 Hz, 1H); EIMS (70 eV) m=z (rel intensity) 433
(Mþ, 42), 432 (81), 431 (100), 172 (48), 131 (49), 91 (84). Found:
C, 77.34; H, 6.37; N, 15.87%. Calcd for C28H27N5: C, 77.57; H,
6.28; N, 16.15%.
12 M. J. Frisch, G. W. Trucks, H. B. Schlegel, G. E. Scuseria,
M. A. Robb, J. R. Cheeseman, J. A. Montgomery, Jr., T. Vreven,
K. N. Kudin, J. C. Burant, J. M. Millam, S. S. Iyengar, J. Tomasi,
V. Barone, B. Mennucci, M. Cossi, G. Scalmani, N. Rega, G. A.
Petersson, H. Nakatsuji, M. Hada, M. Ehara, K. Toyota, R.
Fukuda, J. Hasegawa, M. Ishida, T. Nakajima, Y. Honda, O.
Kitao, H. Nakai, M. Klene, X. Li, J. E. Knox, H. P. Hratchian,
J. B. Cross, C. Adamo, J. Jaramillo, R. Gomperts, R. E. Stratmann,
O. Yazyev, A. J. Austin, R. Cammi, C. Pomelli, J. W. Ochterski,
P. Y. Ayala, K. Morokuma, G. A. Voth, P. Salvador, J. J.
Dannenberg, V. G. Zakrzewski, S. Dapprich, A. D. Daniels,
M. C. Strain, O. Farkas, D. K. Malick, A. D. Rabuck, K.
Raghavachari, J. B. Foresman, J. V. Ortiz, Q. Cui, A. G. Gul, S.
Clifford, J. Cioslowski, B. B. Stefanov, G. Liu, A. Liashenko, P.
Piskorz, I. Komaromi, R. L. Martin, D. J. Fox, T. Keith, M. A.
Al-Laham, C. Y. Peng, A. Nanayakkara, M. Challacombe, P. M.
W. Gill, B. Johnson, W. Chen, M. W. Wong, C. Gonzalez, and
J. A. Pople, Gaussian Inc., Gaussian 03W Program, Pittsburgh
PA, 2003.
The authors would like to thank Dr. Hisayoshi Shiozaki of
Technology Research Institute of Osaka Prefecture for help
in MO calculations and Dr. Shinya Matsumoto of Yokohama
National University for useful discussions.
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