Substituent-dependence of photophysical properties of trans-2- styrylpyridazin-3(2H)-ones

Article abstract of DOI:10.1002/jhet.137

(Figure Presented) The photophysical behavior of trans-2-styrylpyridazin- 3(2H)-ones 3 strongly depend on the number and the position of substituents in the phenyl ring in THF, methylene chloride, acetonitrile and methanol. The absorption spectra of 3 containing the electron-donating substituents at the para-position show the red-shift, whereas the spectra of 3 containing the electron-withdrawing substituents show the blueshift. For the trans-2-(p-substituted-styryl)pyridazin-3(2H)-ones 3b-3h and 3k-3o, the magnitude of the solvatochromic shifts and the shape of the fluorescence spectra depend on the number and/or the position of substituents in benzene ring. The emission maximum of trans-2-styrylpyridazin-3(2H)-ones involving the electron-donating group is larger than one of trans-2-styrylpyridazin-3(2H)-ones involving the electron-withdrawing group in the phenyl ring. The magnitude of the emission maximum is roughly parallel to the relative electron-withdrawing ability of the substituents of the phenyl ring.

Full text of DOI:10.1002/jhet.137

July 2009
Substituent-Dependence of Photophysical Properties of
trans-2-Styrylpyridazin-3(2H)-ones
691
Bo Ram Kim, Su-Dong Cho, Hyung-Geun Lee, Heung-Seop Yim,
Min-Jung Kim, Jaeyoung Hwang, Song-Eun Park, Jeum-Jong Kim,
Kwang-Ju Jung, and Yong-Jin Yoon*
Department of Chemistry, Environmental Biotechnology National Core Research Center and
Research Institute of Natural Science, Graduate School for Molecular Materials and
Nanochemistry, Gyeongsang National University, Jinju 660-701, Korea
*E-mail: yjyoon@gnu.ac.kr
Received October 3, 2009
DOI 10.1002/jhet.137
Published online 10 July 2009 in Wiley InterScience (www.interscience.wiley.com).
The photophysical behavior of trans-2-styrylpyridazin-3(2H)-ones 3 strongly depend on the number
and the position of substituents in the phenyl ring in THF, methylene chloride, acetonitrile and metha-
nol. The absorption spectra of 3 containing the electron-donating substituents at the para-position show
the red-shift, whereas the spectra of 3 containing the electron-withdrawing substituents show the blue-
shift. For the trans-2-(p-substituted-styryl)pyridazin-3(2H)-ones 3b–3h and 3k–3o, the magnitude of the
solvatochromic shifts and the shape of the fluorescence spectra depend on the number and/or the posi-
tion of substituents in benzene ring. The emission maximum of trans-2-styrylpyridazin-3(2H)-ones
involving the electron-donating group is larger than one of trans-2-styrylpyridazin-3(2H)-ones involving
the electron-withdrawing group in the phenyl ring. The magnitude of the emission maximum is roughly
parallel to the relative electron-withdrawing ability of the substituents of the phenyl ring.
J. Heterocyclic Chem., 46, 691 (2009).
INTRODUCTION
because of the lack of flexible design strategies. The
design also is largely empirical at present. Thus, the tun-
ing of the photophysical properties introducing the sub-
stituent is very useful in this field.
The creation of luminescent molecules is an active
field of research in supramolecular chemistry [1–8]. The
chemosensors also have the advantages of possessing
high sensitivity and selectivity, as well as providing on-
line and real time analysis [9–25]. However, the devel-
opment of a useful fluorescent probes is difficult
Organic molecules that contain styryl moiety are
an important fluorescent class and show a number of
attractive photophysical and electro-optical properties
C
V
2009 HeteroCorporation

692
B. R. Kim, S.-D. Cho, H.-G. Lee, H.-S. Yim, M.-J. Kim, J. Hwang, S.-E. Park, J.-J Kim,
K.-J. Jung, and Y.-J. Yoon
Vol 46
Scheme 1
[20,26–36]. The substitution of phenyl ring in stilbene
with a heterocyclic acceptor (pyridine) significantly
affected the photophysical and photochemical behavior,
because of the involvement of the (np*) state [28,37].
According to the literature [26,28,38–40], the photo-
physical behavior and the torsional barrier of trans-stil-
bene derivatives depend on the nature of substituents
and/or solvent polarity. Therefore, the fluorescent prop-
erty could be tunable by the introduction of a suitable
substituent on the phenyl ring in stilbene.
ture [41] using the synthetic sequence outlined in
Scheme 1. Compound 2 [43] was reacted with benzalde-
hyde after treating potassium iodide and then triphenyl-
phosphine to give trans-isomers 3 as the major product.
Although cis-isomers 4 were formed as the minor prod-
uct, it was not isolated since the cis-isomer changed
slowly to trans-isomer at room temperature during the
workup. The structures of 3 were established by NMR,
IR and elemental analyses.
Absorption spectra. All the trans-2-styrylpyridazin-
3(2H)-ones 3a–3aa displays a single intense long wave-
length absorption band in methylene chloride, tetrahydro-
furan, acetonitrile and methanol. The absorption maxima
are reported in Table 2. In general, the absorption maxi-
mum of 3 depends on substituent of para-position in ben-
zene ring; that is, the electron-donating group shows the
red-shift (e.g., 3o vs. 3a), whereas the electron-withdraw-
ing group shows the blue-shift (e.g., 3f vs. 3a).
The substituted position also affects about absorp-
tion maximum of nitrophenyl derivatives, that is, the
4-nitro: the red-shift (3h vs. 3a); the 2-nitro or 3-nitro
group: the blue-shift (3i/3j vs. 3a). The 3b show the
blue-shift in the absorption maximum due to the 4-flu-
oro group.
Recently, we reported the synthesis the photophysical
properties and the potentiality for the application as
spectroscopic or fluorescent probes for some N-styrylazi-
nones containing Het-NACH¼¼CHAAr (Het ¼ heteto-
cycle) moiety [41]. The heterocycle-dependent photo-
physical behavior of trans-2-(2-arylvinyl)-4,5-dichloro-
pyridazin-3(2H)-ones was also reported [42]. Because of
the utility of CACl bond in 4,5-dichloropyridazin-
3(2H)-one ring for the derivatization, we selected trans-
4,5-dichloro-2-styrylpyridazin-3(2H)-one as parent fluo-
rescence molecules, and studied on the dependence on
the substituents of the phenyl ring about the photophysi-
cal properties of 3. Here we report on the synthesis and
tuning of the photophysical properties of some trans-2-
styrylpyridazin-3(2H)-ones 3.
On the other hand, we investigated the dependence of
an absorption spectrum on the position and the number
of methoxy group. All methoxy compounds showed the
red-shift compared with 3a in the absorption spectrum.
The magnitude of the bathochromic effect of 2-methoxy
and 4-methoxy compounds (3o and 3p) is larger than
that of 3-methoxy derivative (3q) (Table 2 entries 15–
17). For the dimethoxy derivatives, the bathochromic
effect of 2,4-, 2,5-, 2,6-, and 3,4-dimethoxy compounds
(3r, 3u, 3w, 3v) is also larger than one of 3,5-and 2,3-
dimethoxy derivatives (3s, 3t) (Table 2 entries 18–23).
All four trimethoxy derivatives (3x–3aa) show much
larger the bathochromic effect than mono- and dime-
thoxy derivatives. Among four trimethoxy derivatives,
the magnitude of the bathochromic shift for 2,4,5- and
2,4,6-trimethoxy compounds (3y and 3z) is especially
large (Table 2 entries 25 and 26).
RESULTS AND DISCUSSION
Synthesis. Various trans-2-(substituted-styryl)pyrida-
zin-3(2H)-ones 3 were prepared according to the litera-
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

July 2009
Substituent-Dependence of Photophysical Properties of
trans-2-Styrylpyridazin-3(2H)-ones
693
Table 1
Synthesis of trans-3 from 2.
Entry
3, R
Yield (%)a
Entry
3, R
Yield (%)a
1
2
a
b
c
d
e
C6H5A
4-FC6H4A
4-ClC6H4A
4-BrC6H4A
4-IC6H4A
4-NCC6H4A
4-(MeO2C)C6H4A
4-NO2C6H4A
2-NO2C6H4A
3-NO2C6H4A
4-MeC6H4A
4-(C6H5)C6H4A
4-(C6H5CHCH)C6H4A
4-(Me)2NC6H5A
47
45
44
51
42
41
49
58
49
54
65
43
41
51
15
16
17
18
19
20
21
22
23
24
25
26
27
o
p
q
r
s
t
u
v
w
x
y
z
aa
4-MeOC6H4A
2-MeOC6H4A
3-MeOC6H4A
46
45
43
43
44
41
42
41
47
45
42
38
39
3
4
2,4-(MeO)2C6H3
3,5-(MeO)2C6H3A
2,3-(MeO)2C6H3A
2,5-(MeO)2C6H3A
3,4-(MeO)2C6H3A
2,6-(MeO)2C6H3A
3,4,5-(MeO)3C6H3A
2,4,6-(MeO)3C6H2A
2,4,5-(MeO)3C6H2A
2,3,4-(MeO)3C6H2A
5
6
7
f
g
h
i
j
k
l
8
9
10
11
12
13
14
m
n
a Isolated yield.
In addition, the absorption spectra of 3 show hypso-
chromic and hyperchromic effects (exception for 3l, 3m,
3o, 3s, 3u, 3w, and 3y-3aa) in acetonitrile comparing
with the spectra in methylene chloride. The absorption
spectra of 3 show hypsochromic and hyperchromic
effects (exception for 3b, 3d, 3g-3l, 3n, 3r, and 3z) in
methanol comparing with the spectra in methylene chlo-
ride. The absorption spectra of 3 show bathochromic
effect (exception for 3h, 3k, 3m, 3p, 3r, 3u, 3v, 3z, and
3aa) and hyperchromic effect (exception for 3c, 3e, 3o,
Table 2
The absorption maxima (nm) for trans-2-(substituted-styryl)pyridazin-3(2H)-ones 3 at room temperature.a
kmax (e)
Entry
3
CH2Cl2
THF
CH3CN
MeOH
1
2
3a
3b
3c
3d
3e
3f
3g
3h
3i
3j
3k
3l
3m
3n
3o
3p
3q
3r
3s
371 (8657)
370 (7935)
371 (8090)
370 (6919)
370 (8837)
362 (7941)
369 (9209)
373 (7004)
362 (7358)
356 (7036)
379 (9820)
384 (9594)
396 (8898)
373 (6264)
389 (8684)
383 (8382)
373 (8699)
401 (8670)
373 (8857)
373 (7366)
395 (8435)
399 (8775)
392 (9180)
386 (7788)
411 (9237)
415 (8930)
393 (8844)
371 (8799)
371 (8017)
371 (7236)
370 (8596)
373 (8763)
364 (8009)
370 (9954)
372 (9546)
365 (8901)
361 (8750)
379 (8010)
382 (4797)
390 (9427)
439 (8509)
389 (8314)
382 (8755)
374 (8232)
401 (8794)
374 (8653)
376 (8024)
394 (7464)
397 (8842)
393 (8327)
387 (8118)
414 (8056)
413 (8357)
394 (9618)
365 (10410)
361 (10117)
363 (10104)
365 (9874)
367 (10110)
359 (8587)
363 (9349)
370 (9369)
358 (7952)
356 (8813)
373 (8350)
374 (5285)
387 (7948)
432 (8589)
382 (7115)
373 (8920)
367 (9164)
394 (8844)
368 (8499)
367 (9517)
386 (8096)
388 (8833)
385 (7635)
378 (8655)
405 (8620)
407 (6915)
384 (8396)
366 (8254)
364 (8172)
365 (7429)
365 (8780)
367 (8629)
357 (7030)
363 (8511)
378 (7310)
358 (7612)
353 (9042)
374 (8570)
376 (6154)
390 (7055)
437 (8272)
382 (8610)
366 (8254)
366 (8649)
397 (8748)
369 (7211)
368 (7556)
387 (8172)
390 (8970)
387 (8717)
378 (7310)
410 (8728)
408 (8213)
387 (8992)
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
3t
3u
3v
3w
3x
3y
3z
3aa
a Data were collected from sample solution prepared under atmosphere without degassing or inert gas bubbling.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

694
B. R. Kim, S.-D. Cho, H.-G. Lee, H.-S. Yim, M.-J. Kim, J. Hwang, S.-E. Park, J.-J Kim,
K.-J. Jung, and Y.-J. Yoon
Vol 46
Table 3
Maxima of fluorescence (kf), fluorescence band half-width (Dm1/2), 0,0 transition (k0,0), Stokes shifts (Dmst), and quantum yields of
2-styryl-pyridazin-3(2H)-ones 3 in tetrahydrofuran, methylene chloride, methanol, and acetonitrile.a
Quantum yield
(U)e
Compound
Solvent
kfb(nm)
Dmst (cmꢀ1 c
)
k0,0 (nm)d
Dm1/2 (cmꢀ1
)
3a
3b
3c
3d
3e
3f
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
492(513)
492
494
496 (519)
492 (501)
491
6629
6608
7096
7335
6645
6697
7329
7233
6773
6603
7051
7223
6650
6472
7175
7203
6423
6640
7225
7053
6726
6588
7003
7092
6387
6310
6866
6951
6019
5409
6554
5821
6455
6454
6702
7023
6141
6875
7689
7111
6480
6320
6913
7044
6757
6568
7309
7474
6720
6420
6984
7320
6624
10664
6793
7753
6711
6747
7415
7373
435
434
431
431
435
434
431
431
435
435
431
431
436
434
433
431
440
438
436
434
427
423
443
421
431
431
426
428
429
425
424
423
421
417
415
412
416
417
418
416
444
446
442
441
453
457
479
449
477
476
508
470
545
532
572
535
466
466
467
462
3451
3407
3432
3383
3355
3396
3431
3375
3384
3401
3487
3404
3404
3416
3496
3378
3335
3324
3335
3271
3648
3751
3717
3787
3594
3567
3661
3575
3718
3591
3932
3747
3844
3889
3837
4098
4072
3774
3816
3865
3122
3177
3148
3710
2883
2862
2854
2820
2425
2408
3002
2741
2121
2168
2665
16816
2431
2492
2503
2543
0.18
0.41
0.18
0.12
0.18
0.27
0.20
0.11
0.33
0.18
0.09
0.09
0.05
0.08
0.02
0.01
0.24
0.19
0.04
0.06
0.18
0.41
0.18
0.12
0.18
0.27
0.20
0.11
0.33
0.18
0.09
0.09
0.05
0.08
0.02
0.01
0.24
0.19
0.04
0.06
0.55
0.42
0.51
0.35
0.83
0.46
0.83
0.84
0.32
0.27
0.16
0.33
0.11
0.13
_
496
494
496 (517)
491
492 (516)
495 (517)
493
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
487
495
495
491
491
499
496 (513)
482
475
CH2Cl2
MeOH
CH3CN
THF
476
485
485
476
484
486
3g
3h
3i
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
479
467
482
471
478
472
471
480
463
471
485
477
502
502
3j
CH2Cl2
MeOH
CH3CN
THF
3k
3l
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
504
505
514
514
519
521
3m
3n
3o
529
531
536
535
619
618
621
641
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
0.01
0.75
0.83
0.74
0.69
526
527
532
531
(Continued)
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

July 2009
Substituent-Dependence of Photophysical Properties of
trans-2-Styrylpyridazin-3(2H)-ones
695
Table 3
(Continued)
Quantum yield
(U)e
Compound
Solvent
kfb(nm)
519
Dmst (cmꢀ1 c
)
k0,0 (nm)d
Dm1/2 (cmꢀ1
)
3p
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
6910
6842
7725
7480
6774
6745
7544
7423
6260
6316
6653
7070
6972
6847
7374
7541
7043
7298
7468
7689
6739
6729
4709
7332
6581
6438
7292
7337
6361
6441
6862
6991
7355
7609
9038
8914
5562
5808
6372
6863
7104
7031
5922
8150
6513
6663
7148
7320
455
455
453
449
441
440
438
436
484
483
485
479
444
442
438
437
444
443
436
433
475
476
438
433
482
479
479
475
465
467
465
461
475
473
460
467
494
495
497
490
509
508
477
478
472
472
471
468
2842
2457
2797
2742
3220
3222
3308
3187
2348
2400
2816
2755
3189
3214
3227
4084
3165
3148
3386
3307
2716
2864
4249
6092
2521
2491
3082
3047
2602
2611
2615
2541
3020
3091
3614
3409
2390
2488
2881
2835
2760
2857
4155
3878
2453
2426
2614
2623
0.73
0.78
0.81
0.64
0.46
0.67
0.31
0.25
0.62
0.85
0.30
0.52
0.39
0.55
0.29
0.10
0.62
0.77
0.04
0.02
0.21
0.12
0.02
0.01
0.76
0.78
0.17
0.24
0.95
0.50
0.66
0.58
0.35
0.35
0.03
0.15
0.69
0.40
0.33
0.43
0.24
0.16
_
519
523
523
500
498
508
504
535
537
540
541
505
500
506
507
511
513 (516)
507
514
536
538
473
534
537
536
544
541
524
524
526
528
540
546
573
574
537
539
555
547
585
585
538
601
530
532
535
535
3q
3r
3s
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
3t
3u
3v
3w
3x
3y
3z
3aa
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
THF
CH2Cl2
MeOH
CH3CN
0.01
0.64
0.91
0.18
0.55
a Fluorescence data were obtained from corrected spectra.
b The second vibronic band is given in parentheses.
c Dmst ¼ mabsꢀ mf.
d The value of k0,0 was obtained from the intersection of normalized absorption and fluorescence spectra.
e Quantum yield of the emission is evaluated at 25ꢁC, the quantum yield values is that relative to 9,10-diphenylanthracene (1.00 ꢂ 10ꢀ4 M) in ace-
tonitrile (from 352 nm excitation wavelength, U ¼ 0.95).
3q, 3s, 3u, 3w, and 3y-3aa) in tetrahydrofuran compar-
ing with the spectra in methylene chloride. However,
the solvatochromic effect of these compounds is rather
small, which indicate a small difference between the
dipole moment of the Franck-Condon excited state and
the ground state [44].
Emission spectra. The fluorescence maxima (kf), the
half-bandwidth (Dm1/2), the 0,0 transitions (k0,0), the
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

696
B. R. Kim, S.-D. Cho, H.-G. Lee, H.-S. Yim, M.-J. Kim, J. Hwang, S.-E. Park, J.-J Kim,
K.-J. Jung, and Y.-J. Yoon
Vol 46
Stokes shift (Dmst), and the fluorescence quantum yield
(U) of all compounds 3 are reported in four solvents in
Table 3. For the trans-2-(p-substituted-styryl)pyridazin-
3(2H)-ones 3b–3h and 3k–3o, the magnitude of the sol-
vatochromic shifts and the shape of the fluorescence
spectra depend on the substituents in four solvents. In
general, the emission maximum of 3 involving an elec-
tron-donating substituent is larger than one of 3 involv-
ing an electron-withdrawing. Among all p-substituted
derivatives, compound 3n shows the largest emission
maximum and the lowest fluorescence efficiency in four
solvents.
Figure 2. In four solvents, a nice linear relationship can
be observed for p-substituted derivatives 3e–3h, 3k, and
3o except for 3l.
For the 3h (4-NO2), 3i (2-NO2), and 3j (3-NO2), the
magnitude of the solvatochromic shifts and the shape of
the fluorescence spectra (Fig. 1) depend on the substi-
tuted position. The magnitude of the emission maximum
for 3h–3j is in the order 3i (2-NO2) >3j (3-NO2) >3h
(4-NO2) in methylene chloride and acetonitrile, 3j (3-
NO2) >3h (4-NO2) >3i (2-NO2) in methanol and 3h (4-
NO2) >3i (2-NO2) >3j (3-NO2) in THF. The magnitude
of the quantum yields for 3h, 3i, and 3j is in the order
3h (4-NO2) >3j (3-NO2) >3i (2-NO2). According 0-0
transition energies (Table 3), the stability of the planar
1t* (ICT) state in the excited state for trans-2-(nitrostyr-
yl)pyridazin-3(2H)-ones 3h-3j depends on the substi-
tuted position of the nitro group and/or slightly the sol-
vent. Among the trans-2-(p-substituted-styryl)pyridazin-
3(2H)-ones, p-methoxy derivative 3o shows the largest
value of the emission maximum and the 0-0 transition
energy in four solvents. Therefore, we have been inves-
tigated the dependence of the fluorescence spectra for
mono-, di- and trimethoxystyryl derivatives on the posi-
tion and the numbers of the methoxy group. Among the
three monomethoxy derivatives, p-substituted derivative
3o shows excellent emission maximum and the high flu-
orescence intensity in four solvents except for 3p in
methanol.
The magnitude of the emission maximum for p-sub-
stituted derivatives 3a–3h and 3k–3o is in the order 3n
(4-Me2N) >3m (4-C6H5CHCH) >3o (4-MeO) >3l (4-
C6H) >3k (4-Me) >3a (4-H) >3b (4-F), 3c (4-Cl), 3e
(4-I) >3d (4-Br) >3g (4-CO2Me) >3f (4-CN) >3h (4-
NO2) in methylene chloride, 3n (4-Me2N) >3m (4-
C6H5CHCH) >3o (4-MeO) >3l (4-C6H5) >3k (4-Me)
>3a (4-H), 3e (4-I) >3d (4-Br), 3c (4-Cl) >3b (4-F)
>3g (4-CO2Me) >3f (4-CN) >3h (4-NO2) in acetonitri-
le,3n (4-Me2N) >3m (4-C6H5CHCH) >3o (4-MeO) >3l
(4-C6H5) >3k (4-Me) >3e (4-I) >3b (4-F) >3d (4-Br)
>3a (4-H) >3c (4-Cl) >3g (4-CO2Me) >3h (4-NO2)
>3f (4-CN) in methanol and 3n (4-Me2N) >3m (4-
C6H5CHCH) >3o (4-MeO) >3l (4-C6H5) >3k (4-Me)
>3c (4-Cl) >3d (4-Br) >3a (4-H), 3b (4-F) >3e (4-I)
>3g (4-CO2Me) >3f (4-CN) >3h (4-NO2) in Tetrahy-
drofuran. The magnitude of the emission maximum for
p-substituted derivatives is roughly parallel with the rel-
ative electron-withdrawing ability of the substitutents.
According to the 0-0 transition energies (Table 3), the
For the trans-2-(dimethoxystyryl)pyridazin-3(2H)-
ones 3r-3w, the emission maximum and the quantum
yield depend very highly on the solvent and the substi-
tuted position (Table 3). Among six dimethoxy deriva-
tives, compound 3v [3,4-(MeO)2] shows the highest
quantum yield in tetrahydrofuran. For the trans-2-(trime-
thoxystyryl)pyridazin-3(2H)-ones 3x-3aa, the number
and the position of the methoxy group and/or the solvent
affected about the magnitude of the solvatochromic
shifts, the shape of the fluorescence spectra and the
quantum yield.
1
planar t* (ICT) state of 3a (4-H) is stabilized by the
electron-donating substituents (e.g., 3k, 3n, and 3o) but
destabilized by the electron-withdrawing substituents
(e.g., 3b, 3f, 3g, and 3h) [26,38]. The number and the
position of the substituents on the phenyl ring and/or the
solvents affected about the magnitude of fluorescence
band half-width (Dm1/2) of all derivatives. Fluorescence
band half-width increases due to the electron-withdraw-
ing groups, whereas one of derivatives containing the
electron-donating groups decreases. All derivatives are
strongly fluorescent in methylene chloride, but the val-
ues of Uf decrease in more polar solvents. It depends on
the substituents of the phenyl ring. The quantum yields
of 3f–3j decrease due to the strong electron-withdrawing
substituents, whereas one of 3b–3e and 3k–3aa
increases due to halogen at the para-position (for 3b–3e)
and the electron-donating substituents (for 3k–3aa).
According to the literatures [26,45], the energies of
the fluorescence maxima of benzene derivatives corre-
late better with the Hammett rþ than with the r con-
stants. The relationship of the energies of the fluores-
cence maxima for 3 and the Hammett rþ shows in the
In case of the trans-2-(methoxystyryl)pyridazin-
3(2H)-ones 3o-3aa, the magnitude of the solvatochromic
shifts and the shape of the fluorescence spectra depend
on the number and the substituted position of the
methoxy group. These effects for the di- and trimethoxy
derivatives 3r–3w, 3x–3aa are larger than the monome-
thoxy derivatives 3p and 3q in polar solvents such as
acetonitrile and methanol. Among the methoxy deriva-
tives, the magnitude of the solvatochromic shifts and the
shape of the fluorescence spectra for 2,5-dimethoxy de-
rivative (3u) change dramatically in polar solvent such
as methanol and acetonitrile. The magnitude of the fluo-
rescence maxima for the trimethoxy derivatives 3x–3z is
larger than the magnitude of the mono- or dimethoxy-
phenyl derivatives 3p–3w except for 3r. In the case of
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

July 2009
Substituent-Dependence of Photophysical Properties of
trans-2-Styrylpyridazin-3(2H)-ones
697
The magnitude of the solvatochromic shifts and the
shape of the fluorescence spectra for 3 depend on the
substituents. In general, the emission maxima of trans-
2-styrylpyridazin-3(2H)-ones involving the electron-
donating group is larger than that of trans-2-styrylpyri-
dazin-3(2H)-ones involving the electron-withdrawing
group. The magnitude of the emission maximum is
roughly parallel with the relative electron-withdrawing
ability of the substitutents. According to the 0-0 transi-
1
tion energies (Table 3), the planar t* (ICT) state of the
trans-2-(p-substituted-styryl)pyridazin-3(2H)-ones is sta-
bilized by electron donating substituents but destabilized
by electron withdrawing substituents. The number and
the position of the substituents on the phenyl ring and/or
the solvents also affected about the magnitude of fluo-
rescence band half-width (Dm1/2) of all derivatives. The
quantum yield and fluorescent intensity of all com-
pounds 3 depend on the number, the kind and the posi-
tion of substituent in the phenyl ring and the solvent.
By introducing the suitable substituent in the phenyl
ring of styryl moiety, trans-2-styrylpyridazin-3(2H)-ones
3 may use as a platform for fluorescence probes. These
results may be a guide-line for the tuning of novel fluo-
rescence molecules containing styryl moiety.
Figure 1. Normalized fluorescence spectra of p-substituted-2-styrylpyr-
idazin-3(2H)-ones 3a-3h and 3k-3o in methylene chloride (I), acetoni-
trile (II), methanol (III), and tetrahydrofuran (IV).
dimethoxy derivatives 3r–3w, the emission maximum
strongly depends on the substitution position and the
solvent. According to the 0-0 transition energies (Table
3), the stability of the planar 1t* (ICT) state for all
methoxy compounds 3o–3aa depends also on the substi-
tuted position and the number of the methoxy group and
slightly the solvent. Especially, the methoxy group at
the para-position should be more stabilized, whereas the
methoxy group at the meta-position should be more
destabilized.
CONCLUSIONS
The substituent-dependent photophysical behavior of
the 28 trans-2-styryl-4,5-dichloropyridazin-3(2H)-ones 3
as novel fluorescent molecules has been elucidated.
According to our observation, the absorption maximum
of compounds 3 depends on the substituent, the substi-
tuted position of the benzene ring and the solvent polar-
ity. In addition, the intensity of absorption spectra for
compounds 3 depends on the solvent polarity.
Figure 2. Correlation diagram of the energies of the fluorescence max-
ima against the Hammett rþ constants for p-substituted derivatives 3e-
3h, 3k, 3l, and 3o in methylene chloride, tetrahydrofuran, methanol
and acetonitrile.
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

698
B. R. Kim, S.-D. Cho, H.-G. Lee, H.-S. Yim, M.-J. Kim, J. Hwang, S.-E. Park, J.-J Kim,
K.-J. Jung, and Y.-J. Yoon
Vol 46
excess diethyl ether and dried to give the product as thin yel-
low crystals. The product was used without further
purification.
Further dynamic, theoretical and application studies
on these and the related systems would complement the
current results and provide more insights into the
photophysical behaviors of trans-N-styryl-nitrogen-
heterocycles.
To a solution of crude ((4,5-dichloro-6-oxopyridazin-1(6H)-
yl)methyl)triphenyl phosphonium iodide (8 g, 14.10 mmol) in
acetonitrile (50 mL) was added benzaldehyde (1.5 g, 14.10
mmol) at 0–10ꢁC. After stirring for 30 min, potassium t-butox-
ide (2.05 g, 95%, 17.21 mmol) was added. The resulting mix-
ture was stirred for 2 h. The solution was concentrated under
reduced pressure. After adding dichloromethane (100 mL) and
then water (50 mL), the solution was stirred for 10 min, and
neutralized to pH 6.7–7.4 by using saturated solution of
NaHCO3. The organic layer was separated and then dried over
anhydrous magnesium sulfate. The resulting organic solution
was evaporated under reduced pressure. The resulting residue
was applied to the top of an open-bed silica gel. The column
was eluted with methylene chloride/n-hexane (1:4, v/v). Frac-
tions containing trans-isomer 3 were combined and evaporated
to give pure trans-isomer 3, respectively. The yields of all
compounds 3 showed in Table 1.
EXPERIMENTAL
General comments. Melting points were determined with a
capillary apparatus and uncorrected. 1H and
13
NMR spectra
were recorded on a 300 MHz spectrometer with chemical shift
values reported in d units (ppm) relative to an internal standard
TMS. IR spectra were obtained on an IR spectrophotometer.
Elemental analyses were performed with a Perkin Elmer 240
C. Open-bed chromatography was carried out on silica gel
(70–230 mesh, Merck) using gravity flow. The column was
packed as slurries with the elution solvent.
Typical process of 4,5-dichloro-2-chloromethylpyridazin-
3(2H)-one (2). A mixture of 4,5-dichloropyridazin-3(2H)-one
(1, 60 g, 364 mmol) and distilled water (350 mL) was stirred
for 10 min at room temperature. After adding formaldehyde
solution (36%, 70 mL), the solution was refluxed for 1.5 h. Af-
ter cooling to 5–10ꢁC, the resulting precipitate was filtered,
washed with cold water (0–5ꢁC, 200 mL) and dried in air to
give N-hydroxymethyl-4,5-dichloropyridazin-3(2H)-one. A so-
lution of thionyl chloride (357 mmol) and dimethylformamide
(360 mmol) in methylene chloride (50 mL) was added slowly
to the mixture of N-hydroxymethyl-4,5-dichloropyridazin-
3(2H)-one and methylene chloride (550 mL) for 30 min at
room temperature with stirring. The resulting mixture was
stirred for 2 h at room temperature. After cooling to 0ꢁC,
water (200 mL) was added slowly. The solution was neutral-
ized to pH 6.7–7.4 by using saturated solution of NaHCO3.
The organic layer was separated and then dried over anhydrous
magnesium sulfate. The resulting organic solution was evapo-
rated under reduced pressure. The residue was washed with n-
hexane (100 mL) to give 4,5-dichloro-2-chloromethylpyrida-
zin-3(2H)-one (2, 71.2 g, 92%) as white color. White crystal
(diethyl ether/n-hexane ¼ 1:5, v/v). mp 69–70ꢁC (lit. 43 mp
70–71ꢁC). TLC (CH2Cl2) Rf ¼ 0.65. IR (KBr) 3046, 2984,
(E)-4,5-Dichloro-2-styrylpyridazin-3(2H)-one (3a). Pale yel-
low crystal (diethyl ether:n-hexane ¼ 1:2, v/v). mp 161–
162ꢁC. IR (KBr) 3108, 1664, 1592, 1300, 1238, 1134, 958,
898, 742, 696 cmꢀ1
.
1H NMR (CDCl3); d 7.25 ꢃ 7.38 (m,
4H), 7.47 ꢃ 7.50 (m, 2H), 7.86 (s, 1H), 8.10 (d, J ¼ 14.35
Hz, 1H). 13C NMR (CDCl3); d 122.21, 124.13, 127.02,
128.49, 128.88, 134.49, 134.56, 135.94, 136.04, 154.68. Anal.
Calcd. for C12H8Cl2N2O: C, 53.96; H, 3.02; N, 10.49. Found:
C, 53.94; H, 3.01; N, 10.51.
(E)-4,5-Dichloro-2-(4-fluorostyryl)pyridazin-3(2H)-one (3b).
Pale yellow crystal (methylene chloride). mp 158–159ꢁC. IR
(KBr) 3096, 1664, 1596, 1520, 1240, 1138, 960, 858, 748
1
cmꢀ1. H NMR (CDCl3); d 7.01 ꢃ 7.09 (m, 2H), 7.24 (d, J ¼
14.58 Hz, 1H), 7.43 ꢃ 7.48 (m, 2H), 7.87 (s, 1H), 8.04 (d, J
¼ 14.34 Hz, 1H). 13C NMR (CDCl3); d 115.78 (CAF), 116.07
(CAF), 121.02, 123.79 (CAF), 123.82 (CAF), 128.58 (CAF),
128.69 (CAF), 130.65 (CAF), 130.69 (CAF), 134.49, 136.00
(CAF), 136.11 (CAF), 154.66, 161.12, 164.42. Anal. Calcd.
for C12H7Cl2FN2O: C, 50.55; H, 2.47; N, 9.83. Found: C,
50.56; H, 2.49; N, 9.84.
(E)-4,5-Dichloro-2-(4-chlorostyryl)pyridazin-3(2H)-one (3c).
Light yellow crystal (methylene chloride). mp 177–178ꢁC. IR
1
1670, 1292, 1122, 964 cmꢀ1
;
1H NMR (CDCl3): d 5.83 (s,
(KBr) 3086, 1664, 1582, 1494, 1290, 960, 818 cmꢀ1. H NMR
2H), 7.88 ppm (s, 1H); 13C NMR (CDCl3) d 58.40, 134.87,
137.23, 137.34, 155.58 ppm. Elemental analysis calcd. for
C5H3Cl3N2O: C 28.13, H 1.42, N 13.12; found: C 28.10, H
1.41, N 13.09.
(CDCl3); d 7.21 (d, J ¼ 14.36 Hz, 1H), 7.27 ꢃ 7.34 (m, 2H),
7.38 ꢃ 7.43 (m, 2H), 7.87 (s, 1H), 8.08 (d, J ¼ 14.35 Hz,
1H). 13C NMR (CDCl3); d 120.80, 124.37, 128.14, 129.06,
133.03, 134.16, 134.52, 136.06, 136.20, 154.63. Anal. Calcd.
for C12H7Cl3N2O: C, 47.79; H, 2.34; N, 9.29. Found: C,
47.78; H, 2.33; N, 9.25.
Typical process of synthesis for trans-4,5-dichloro-2-styr-
ylpyridazin-3(2H)-one 3. A mixture of 2-chloromethyl-4,5-
dichloropyridazin-3(2H)-one (2, 3 g, 14.055 mmol), sodium
iodide (2.45 g, 14.76 mmol) and acetonitrile (50 mL) was
refluxed for 10 h. After cooling to 30–40ꢁC, triphenylphos-
phine (4.07 g, 15.51 mmol) was added to the reaction solution.
The mixture was then refluxed for 6 h. After cooling to room
temperature, the mixture was filtered by using Celite 545 and
washed with methylene chloride (50 mL). The organic layer
was concentrated under reduced pressure. After adding
dichloromethane (100 mL) to the resulting mixture, the solu-
tion was stirred for 20 min. The solution was filtered and then
concentrated under reduced pressure. After cooling to room
temperature, the resulting precipitate was filtered, washed with
(E)-2-(4-Bromostyryl)-4,5-dichloropyridazin-3(2H)-one (3d).
Light yellow crystal (methylene chloride). mp 183–184ꢁC. IR
(KBr) 3100, 1676, 1594, 1496, 1300, 1138, 963, 902, 820
1
cmꢀ1. H NMR (CDCl3); d 7.20 (d, J ¼ 14.35 Hz, 1H), 7.32
ꢃ 7.36 (m, 2H), 7.46 ꢃ 7.50 (m, 2H), 7.87 (s, 1H), 8.09 (d, J
¼ 14.32 Hz, 1H). 13C NMR (CDCl3); d 120.91, 122.37,
124.55, 128.43, 132.04, 133.55, 134.58, 136.05, 136.19,
154.63. Anal. Calcd. for C12H7BrCl2N2O: C, 41.65; H, 2.04;
N, 8.10. Found: C, 41.66; H, 2.03; N, 8.08.
(E)-4,5-Dichloro-2-(4-iodostyryl)pyridazin-3(2H)-one (3e).
Light yellow crystal (methylene chloride). mp 194–195ꢁC. IR
(KBr) 3122, 1680, 1596, 1298, 1234, 970, 900, 806, 760
Journal of Heterocyclic Chemistry
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Substituent-Dependence of Photophysical Properties of
trans-2-Styrylpyridazin-3(2H)-ones
699
1
cmꢀ1. H NMR (CDCl3); d 7.17 ꢃ 7.24 (m, 3H), 7.69 (d, J ¼
8.42 Hz, 2H), 7.88 (s, 1H), 8.12 (d, J ¼ 14.37 Hz, 1H). 13C
NMR (CDCl3); d 99.94, 121.01, 124.54, 128.61, 134.09,
134.59, 136.09, 136.25, 137.99, 154.66. Anal. Calcd. for
C12H7ICl2N2O: C, 36.67; H, 1.80; N, 7.13. Found: C, 36.65;
H, 1.79; N, 7.10.
213ꢁC. IR (KBr) 3088, 1680, 1614, 1140, 972, 838, 760 cmꢀ1
.
1H NMR (CDCl3); d 7.31 ꢃ 7.38 (m, 2H), 7.42 ꢃ 7.47 (m,
2H), 7.55 ꢃ 7.63 (m, 6H), 7.92 (s, 1H), 8.16 (d, J ¼ 14.31
Hz, 1H). 13C NMR (CDCl3); d 121.99, 123.92, 126.84,
126.96, 127.43, 127.49, 128.77, 133.47, 134.34, 136.09,
136.26, 140.29, 141.25, 154.84. Anal. Calcd. for
C18H12Cl2N2O: C, 62.99; H, 3.52; N, 8.16. Found: C, 62.98;
H, 3.49; N, 8.15.
(E)-2-(4-Cyanostyryl)-4,5-dichloropyridazin-3(2H)-one (3f).
Light yellow crystal (methylene chloride). mp 226–227ꢁC. IR
(KBr) 3092, 2998, 2226, 1665, 1584, 1294, 1136, 962, 947,
.
895, 864, 824, 556 cmꢀ1 1H NMR (CDCl3); d 3.81 (s,
2OCH3), 6.40 ꢃ 6.42 (t, J ¼ 2.19 Hz, 1H), 6.62 (d, J ¼ 2.21
Hz, 2H), 7.27 (d, J ¼ 14.37 Hz, 1H), 7.56–7.59 (m, 2H), 7.64
ꢃ 7.67 (m, 2H), 7.91 (s, 1H), 8.19 (d, J ¼ 14.38 Hz, 1H). 13C
NMR (CDCl3); d 111.57, 118.67, 119.97, 126.65, 127.38,
132.66, 134.83, 136.40, 136.62, 139.28, 154.73 ppm. Anal.
Calcd. for C13H7Cl2N3O: C, 53.45; H, 2.42; N, 14.38. Found:
C, 53.44; H, 2.42; N, 14.35.
4,5-Dichloro-2-((E)-4-(E)-styrylstyryl)pyridazin-3(2H)-one
(3m). Yellow crystal (methylene chloride). mp 224–225ꢁC. IR
(KBr) 3106, 1670, 1600, 1520, 1306, 1142, 968, 906, 820,
768, 698 cmꢀ1
.
1H NMR (CDCl3); d 7.12 (d, J ¼ 4.01 Hz,
2H), 7.24 ꢃ 7.29 (m, 2H), 7.32 ꢃ 7.39 (m, 25H), 7.47 ꢃ 7.54
(m, 6H), 7.89 (s, 1H), 8.15 (d, J ¼ 14.32 Hz, 1H). 13C NMR
(CDCl3); d 121.87, 123.93, 126.58, 126.98, 127.39, 127.81,
128.02, 128.71, 129.28, 133.86, 134.38, 136.07, 137.18,
137.67. Anal. Calcd. for C20H14Cl2N2O: C, 65.06; H, 3.82; N,
7.59. Found: C, 65.05; H, 3.81; N, 7.57.
(E)-4,5-Dichloro-2-(4-methoxycarbonylstyryl)pyridazin-3(2H)-
one (3g). Light yellow crystal (methylene chloride). mp 212–
214ꢁC. IR(KBr) 3086, 3053, 3005, 2954, 1711, 1670, 1589,
.
1436, 1277, 1182, 112, 954 cmꢀ1 1H NMR (CDCl3); d 3.91
(E)-4,5-dichloro-2-(4-(dimethylamino)styryl)pyridazin-3(2H)-
one (3n). Deep red crystal (methylene chloride). mp 130–
132ꢁC. IR (KBr) 3134, 2962, 1678, 1620, 1540, 1522, 1380,
.
1200, 1248, 1236, 964, 914 cmꢀ1 1H NMR (CDCl3); d 2.99
(s, 6H), 6.68 (d, J ¼ 8.86 Hz, 2H), 7.22 (d, J ¼ 14.26 Hz,
1H), 7.39 (d, J ¼ 8.84 Hz, 2H), 7.85 (s, 1H), 7.98 (d, J ¼
14.24 Hz, 1H). 13C NMR (CDCl3); d 40.30, 112.25, 120.51,
122.36, 122.75, 128.27, 133.89, 135.33, 135.60, 150.59,
154.52. Anal. Calcd. for C14H13Cl2N3O: C, 54.21; H, 4.22; N,
13.55. Found: C, 54.19; H, 4.20; N, 13.52.
(s, OCH3), 7.30 (d, J ¼ 14.37 Hz, 1H), 7.54 ꢃ 7.57 (m, 2H),
7.90 (s, 1H), 8.02 ꢃ 8.05 (m, 2H), 8.20 (d, J ¼ 14.35 Hz,
1H). 13C NMR (CDCl3); d 52.17, 120.91, 125.82, 126.85,
129.77, 130.17, 134.70, 136.21, 136.38, 139.12, 154.72,
166.62 ppm. Anal. Calcd. for C14H10Cl2N2O3: C, 51.72; H,
3.10; N, 8.62. Found: C, 51.71; H, 3.11; N, 8.60.
d 7.32 (d, J ¼ 14.38 Hz, 1H), 7.61 ꢃ 7.65 (m, 2H), 7.92 (s,
1H), 8.20 ꢃ 8.27 (m, 3H). 13C NMR (CDCl3); d 119.47,
124.25, 127.19, 127.44, 134.86, 136.44, 136.69, 141.26,
147.32, 154.72. Anal. Calcd. for C12H7Cl2N3O3: C, 46.18; H,
2.26; N, 13.46. Found: C, 46.16; H, 2.23; N, 13.47.
(E)-4,5-dichloro-2-(4-methoxystyryl)pyridazin-3(2H)-one (3o).
Yellow crystal (methylene chloride). mp 177–178ꢁC. IR (KBr)
3062, 2944, 1666, 1614, 1590, 1522, 1308, 1258, 1196, 1140,
1
1038, 960, 906, 812, 744 cmꢀ1. H NMR (CDCl3); d 3.83 (s,
(E)-4,5-dichloro-2-(2-nitrostyryl)pyridazin-3(2H)-one (3i).
Light yellow crystal (methylene chloride). mp 180–181ꢁC. IR
(KBr) 3108, 3068, 1668, 1596, 1520, 1340, 1300, 1280, 1146,
OCH3), 6.87 ꢃ 6.92 (m, 2H), 7.23 (d, J ¼ 14.32 Hz, 1H),
7.41 ꢃ 7.4 5 (m, 2H), 7.86 (s, 1H), 8.01 (d, J ¼ 14.29 Hz,
1H). 13C NMR (CDCl3); d 55.34, 114.32, 121.95, 122.36,
127.09, 128.37, 134.25, 135.74, 135.88, 154.62, 159.95. Anal.
Calcd. for C13H10Cl2N2O2: C, 52.55; H, 3.39; N, 9.43. Found:
C, 52.52; H, 3.38; N, 9.40.
(E)-4,5-dichloro-2-(2-methoxystyryl)pyridazin-3(2H)-one (3p).
Light yellow crystal (methylene chloride). mp 133–135ꢁC. IR
(KBr) 3132, 2987, 1684, 1600, 1500, 1478, 1300, 1260, 1140,
1042, 966, 760 cmꢀ1 1H NMR (CDCl3); d 3.91 (s, OCH3),
.
1122, 964, 950, 898, 738 cmꢀ1
.
1H NMR (CDCl3); d 7.45 ꢃ
7.50 (m, 1H), 7.61 ꢃ 7.66 (m, 1H), 7.70 ꢃ 7.73 (m, 1H), 7.80
(d, J ¼ 14.15 Hz, 1H), 7.93 (s, 1H), 8.00 ꢃ 8.04 (m, 1H),
8.08 (d, J ¼ 14.12 Hz, 1H). 13C NMR (CDCl3); d 117.55,
125.07, 127.30, 128.59, 128.92, 130.38, 133.46, 134.72,
136.50, 136.64, 148.24, 154.79. Anal. Calcd. for
C12H7Cl2N3O3: C, 46.18; H, 2.26; N, 13.46. Found: C, 46.15;
H, 2.24; N, 13.45.
d 7.38 (d, J ¼ 14.26 Hz, 1H), 7.59 ꢃ 7.64 (m, 1H), 7.88 ꢃ
7.91 (m, 1H), 8.08 ꢃ 8.15 (m, 2H), 8.23 (d, J ¼ 14.38 Hz,
1H), 8.34 (s, 1H). 13C NMR (CDCl3); d 119.34, 121.89,
123.06, 127.12, 130.78, 133.35, 134.01, 136.36, 136.92,
137.69, 148.83, 154.75. Anal. Calcd. for C12H7Cl2N3O3: C,
46.18; H, 2.26; N, 13.46. Found: C, 46.13; H, 2.23; N, 13.42.
(E)-4,5-dichloro-2-(4-methylstyryl)pyridazin-3(2H)-one (3k).
Light yellow crystal (methylene chloride). mp 179–180ꢁC. IR
(KBr) 3150, 2976, 1688, 1610, 1322, 1158, 980, 920, 832, 758
6.91 ꢃ 6.99 (m, 2H), 7.26 ꢃ 7.31 (m, 1H), 7.48 ꢃ 7.51 (m,
1H), 7.53 (d, J ¼ 14.02 Hz, 1H), 7.89 (s, 1H), 8.87 (d, J ¼
14.32 Hz, 1H). 13C NMR (CDCl3); d 55.50, 110.96, 118.06,
120.82, 123.42, 124.89, 128.31, 129.58, 134.33, 135.81,
135.90, 154.73, 157.45. Anal. Calcd. for C13H10Cl2N2O2: C,
52.55; H, 3.39; N, 9.43. Found: C, 52.53; H, 3.37; N, 9.42.
(E)-4,5-dichloro-2-(3-methoxystyryl)pyridazin-3(2H)-one (3q).
Pale yellow crystal (methylene chloride). mp 143–145ꢁC. IR
(KBr) 3126, 2988, 1676, 1602, 1504, 1478, 1264, 1134, 1046,
960, 900, 796, 740 cmꢀ1 1H NMR (CDCl3); d 3.84 (s,
.
cmꢀ1
.
1H NMR (CDCl3); d 2.35 (s, CH3), 7.15 (d, J ¼ 7.97
OCH3), 6.84 ꢃ 6.88 (m, 1H), 7.01 ꢃ 7.02 (m, 1H), 7.08 ꢃ
7.11 (m, 1H), 7.24 ꢃ 7.31 (m, 2H), 7.89 (s, 1H), 8.12 (d, J ¼
14.32 Hz, 1H). 13C NMR (CDCl3); d 55.33, 112.12, 114.34,
119.73, 122.15, 124.30, 129.88, 134.52, 135.92, 136.00,
136.12, 154.72, 159.95. Anal. Calcd. for C13H10Cl2N2O2: C,
52.55; H, 3.39; N, 9.43. Found: C, 52.51; H, 3.38; N, 9.43.
(E)-4,5-dichloro-2-(2,4-dimethoxystyryl)pyridazin-3(2H)-one
(3r). Yellow crystal (methylene chloride). mp 169–170ꢁC. IR
(KBr) 3066, 2982, 1660, 1620, 1592, 1516, 1460, 1298, 1280,
Hz, 2H), 7.25 (d, J ¼ 14.34 Hz, 1H), 7.38 (d, J ¼ 8.08 Hz,
2H), 7.85 (s, 1H), 8.08 (d, J ¼ 14.32 Hz, 1H). 13C NMR
(CDCl3); d 21.28, 122.22, 123.37, 126.94, 129.57, 131.69,
134.37, 135.80, 135.91, 138.59. Anal. Calcd. for
C13H10Cl2N2O: C, 55.54; H, 3.59; N, 9.96. Found: C, 55.51;
H, 3.58; N, 9.93.
(E)-2-(2-(biphenyl-4-yl)vinyl)-4,5-dichloropyridazin-3(2H)-
one (3l). Light yellow crystal (methylene chloride). mp 212–
Journal of Heterocyclic Chemistry
DOI 10.1002/jhet

700
B. R. Kim, S.-D. Cho, H.-G. Lee, H.-S. Yim, M.-J. Kim, J. Hwang, S.-E. Park, J.-J Kim,
K.-J. Jung, and Y.-J. Yoon
Vol 46
1216, 1156, 1134, 1040, 966, 898, 834 cmꢀ1
.
1H NMR
130.12, 134.46, 135.95, 136.11, 138.69, 153.52, 154.68. Anal.
Calcd. for C15H14Cl2N2O4: C, 50.44; H, 3.95; N, 7.84. Found:
C, 50.43; H, 3.93; N, 7.82.
(E)-4,5-dichloro-2-(2,4,6-trimethoxystyryl)pyridazin-3(2H)-
one (3y). Orange crystal (methylene chloride). mp 209–210ꢁC.
IR (KBr) 3058, 2950, 1650, 1600, 1580, 1458, 1334, 1232,
1196, 1120, 956 cmꢀ1 1H NMR (CDCl3); d 3.84 (s, OCH3),
.
3.90 (s, 2OCH3), 6.16 (s, 2H), 7.62 (d, J ¼ 14.37 Hz, 1H),
7.88 (s, 1H), 8.51 (d, J ¼ 14.37 Hz, 1H). 13C NMR (CDCl3);
d 55.36, 55.80, 90.62, 105.36, 113.45, 124.96, 133.86, 135.30,
135.45, 154.70, 159.78, 161.20. Anal. Calcd. for
C15H14Cl2N2O4: C, 50.44; H, 3.95; N, 7.84. Found: C, 50.41;
H, 3.93; N, 7.83.
d 3.89 (s, 2 OCH3), 3.92 (s, OCH3), 6.53 (s, 1H), 6.99 (d,
J ¼ 2.66 Hz, 1H), 7.47 (d, J ¼ 14.38 Hz, 1H), 7.87 (s, 1H),
8.14 (d, J ¼ 14.37 Hz, 1H). 13C NMR (CDCl3); d 56.10,
56.45, 56.61, 97.40, 110.86, 115.04, 117.73, 123.03, 134.09,
135.59, 135.75, 143.38, 150.41, 152.41, 152.52, 154.64. Anal.
Calcd. for C15H14Cl2N2O4: C, 50.44; H, 3.95; N, 7.84. Found:
C, 50.40; H, 3.93; N, 7.84.
(CDCl3); d 3.83 (s, OCH3), 3.88 (s, OCH3), 6.47 ꢃ 6.52 (m,
2H), 7.39 ꢃ 7.46 (m, 3H), 7.86 (s, 1H), 8.17 (d, J ¼ 14.36
Hz, 1H). 13C NMR (CDCl3); d 55.42, 55.51, 98.64, 105.08,
116.50, 118.10, 123.21, 129.30, 134.08, 135.52, 135.65,
154.62, 158.71, 161.23. Anal. Calcd. for C14H12Cl2N2O3: C,
51.40; H, 3.70; N, 8.56. Found: C, 51.38; H, 3.70; N, 8.55.
d 3.81 (s, 2OCH3), 6.40 ꢃ 6.42 (t, J ¼ 2.19 Hz, 1H), 6.62
(d, J ¼ 2.21 Hz, 2H), 7.20 (d, J ¼ 14.30 Hz, 1H), 7.86 (s,
1H), 8.09 (d, J ¼ 14.29 Hz, 1H). 13C NMR (CDCl3); d 55.43,
100.85, 104.99, 122.16, 124.40, 134.47, 135.98, 136.12,
136.41, 154.66, 161.03. Anal. Calcd. for C14H12Cl2N2O3: C,
51.40; H, 3.70; N, 8.56. Found: C, 51.36; H, 3.69; N, 8.53.
(E)-4,5-dichloro-2-(2,3-dimethoxystyryl)pyridazin-3(2H)-one
(3t). Yellow crystal (methylene chloride). mp 149–150ꢁC. IR
(KBr) 3066, 2962, 1674, 1592, 1482, 1276, 1076, 966 cmꢀ1
.
1H NMR (CDCl3); d 3.86 (s, OCH3), 3.88 (s, OCH3), 6.87
(dd, J ¼ 1.28, 8.06 Hz, 1H), 7.05 (t, J ¼ 7.96 Hz, 1H), 7.15
(dd, J ¼ 1.27, 7.90 Hz, 1H), 7.54 (d, J ¼ 14.46 Hz, 1H), 7.89
(s, 1H), 8.20 (d, J ¼ 14.44 Hz, 1H). 13C NMR (CDCl3); d
55.85, 60.96, 112.34, 117.20, 118.82, 124.27, 125.26, 128.72,
134.38, 135.95, 136.03, 147.46, 153.12, 154.75. Anal. Calcd.
for C14H12Cl2N2O3: C, 51.40; H, 3.70; N, 8.56. Found: C,
51.39; H, 3.68; N, 8.55.
(E)-4,5-dichloro-2-(2,3,4-trimethoxystyryl)pyridazin-3(2H)-
one (3aa). Yellow crystal (methylene chloride). mp 127–
128ꢁC. IR (KBr) 3106, 2964, 1670, 1598, 1500, 1472, 1420,
.
1306, 1114, 1100, 970, 896 cmꢀ1 1H NMR (CDCl3); d 3.89
(E)-4,5-dichloro-2-(2,5-dimethoxystyryl)pyridazin-3(2H)-one
(3u). Yellow crystal (methylene chloride). mp 158–159ꢁC. IR
(KBr) 3068, 2974, 1664, 1594, 1506, 1300, 1228, 1046, 972,
(s, 2 OCH3), 3.93 (s, OCH3), 6.69 (d, J ¼ 8.77 Hz, 1H), 7.22
(d, J ¼ 8.74 Hz, 1H), 7.426 (d, J ¼ 14.43 Hz, 1H), 7.88 (s,
1H), 8.14 (d, J ¼ 14.39 Hz, 1H). 13C NMR (CDCl3); d 56.06,
60.88, 61.12, 107.76, 117.54, 121.48, 122.12, 123.66, 134.19,
135.73, 135.85, 142.51, 152.25, 154.07, 154.66. Anal. Calcd.
for C15H14Cl2N2O4: C, 50.44; H, 3.95; N, 7.84. Found: C,
50.43; H, 3.94; N, 7.85.
896, 814, 742 cmꢀ1 1H NMR (CDCl3); d 3.80 (s, OCH3),
.
3.85 (s, OCH3), 6.83 (s, 2H), 7.02 (d, J ¼ 1.93 Hz, 1H), 7.47
(d, J ¼ 14.40 Hz, 1H), 7.86 (s, 1H), 8.23 (d, J ¼ 14.38 Hz,
1H). 13C NMR (CDCl3); d 55.80, 56.10, 112.20, 113.06,
114.83, 117.78, 124.10, 125.05, 134.29, 135.79, 135.90,
151.92, 153.63, 154.66. Anal. Calcd. for C14H12Cl2N2O3: C,
51.40; H, 3.70; N, 8.56. Found: C, 51.38; H, 3.67; N, 8.53.
(E)-4,5-dichloro-2-(3,4-dimethoxystyryl)pyridazin-3(2H)-one
(3v). Yellow crystal (methylene chloride). mp 163–164ꢁC. IR
(KBr) 3076, 2966, 1674, 1600, 1530, 1272, 1156, 1036, 958,
Absorption spectra, fluorescence spectra and quantum
yield. UV spectra were measured on a Shimadzu PC-2401
double beam spectrophotometer. Absorption spectra were col-
lected from sample solution prepared under atmosphere with-
out degassing or inert gas bubbling. The concentration of the
b
sample solution is 1.0 ꢂ 10ꢀ4 M. (Mꢀ1 cmꢀ1).
1
908, 814 cmꢀ1. H NMR (CDCl3); d 3.90 (s, OCH3), 3.93 (s,
Fluorescence spectra were recorded on a PerkinElmer
OCH3), 6.84 (d, J ¼ 7.97 Hz, 1H), 7.01 ꢃ 7.04 (m, 2H), 7.22
(d, J ¼ 14.30 Hz, 1H), 7.85 (s, 1H), 8.01 (d, J ¼ 14.28 Hz,
1H). 13C NMR (CDCl3); d 55.94, 55.97, 109.01, 111.27,
120.81, 122.20, 122.48, 127.41, 134.25, 135.74, 135.90,
149.26, 149.67, 154.59. Anal. Calcd. for C14H12Cl2N2O3: C,
51.40; H, 3.70; N, 8.56. Found: C, 51.39; H, 3.68; N, 8.55.
(E)-4,5-dichloro-2-(2,6-dimethoxystyryl)pyridazin-3(2H)-one
(3w). Light yellow crystal (methylene chloride). mp 190ꢁC. IR
(KBr) 3060, 2964, 1660, 1590, 1480, 1258, 1136, 1106, 962,
LS50B spectrofluorometer at room temperature. Quantum yield
of the emission is evaluated in acetonitrile at 25ꢁC, the quan-
tum yield values are that relative to 9,10-diphenylanthrancene
(1.00 ꢂ 10ꢀ4 M) in acetonitrile (from 352 nm extraction, U ¼
0.95).
Acknowledgment. This work was supported by a grant from the
Korea Science and Engineering Foundation (KOSEF) to the
Environmental Biotechnology National Core Research Center
(grant no. R15-2003-012-02001-0).
1
776, 720 cmꢀ1. H NMR (CDCl3); d 3.90 (s, 2OCH3), 6.56 (d,
J ¼ 8.39 Hz, 2H), 7.19 (t, J ¼ 8.37 Hz, 1H), 7.66 (d, J ¼
14.42 Hz, 1H), 7.86 (s, 1H), 8.63 (d, J ¼ 14.42 Hz, 1H). 13C
NMR (CDCl3); d 55.84, 103.75, 111.99, 113.20, 126.91,
12916, 134.06, 135.53, 135.62, 154.73, 158.81. Anal. Calcd.
for C14H12Cl2N2O3: C, 51.40; H, 3.70; N, 8.56. Found: C,
51.37; H, 3.66; N, 8.54.
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