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European	Journal	of	Chemistry	3	(4)	(2012)	461‐467	

European	Journal	of	Chemistry	
ISSN	2153‐2249	(Print)	/	ISSN	2153‐2257	(Online)		2012	EURJCHEM	

DOI:10.5155/eurjchem.3.4.461‐467.699	

	
	

	

	

European	Journal	of	Chemistry	
Journal	homepage:	www.eurjchem.com	

	 	 	

Benzo[g]quinoline	heterocyclic	derivative	as	a	typical	precursor	in	
the	synthesis	of	new	class	of	cyanine‐like	dyes	

Maha	Mobaruk	Gomaa	a,	Naglaa	Salah	El‐Deen	a,b,	*	and	Nadia	Ali	El‐Kanzi	a	

a	Chemistry	Department,	Aswan	Faculty	of	Science,	Aswan	University,	Aswan,	81528,	Egypt	
b	Chemistry	Department,	Najran	Faculty	of	Sciences	and	Arts,	Najran	University,	Najran,	11114,	Kingdom	of	Saudi	Arabia	

*Corresponding	author	at:	Chemistry	Department,	Najran	Faculty	of	Sciences	and	Arts,	Najran	University,	Najran,	11114,	Kingdom	of	Saudi	Arabia.		
Tel.:	+2.097.2312850;	Fax:	+2.097.3480450.	E‐mail	address:	naglaanaglaa@yahoo.com	(N.S.	El‐Deen).	

	
	

	 	

	 	 	
ARTICLE	INFORMATION	 	 ABSTRACT
Received:	31	October	2012	
Accepted:	06	November	2012	
Online:	31	December	2012	

KEYWORDS	

	 New	 unsymmetrical	 cyanine‐like	 dyes	 have	 been	 synthesized	 including	 monomethine,
dimethine,	and	tetramethine,	containing	heterocyclic	quinone	of	benzo[g]quinoline	derivative.
The	new	synthesized	compounds	were	identified	by	elemental	analysis,	IR	and	1H	NMR.	The
UV	visible	absorption	spectra	of	dyes	are	also	reported.	

Quinone	
Carbonitrile	
Quinolinium		
Meso	substituted	
Cyanine	like‐dyes	
Spectral	behavior	

	
1.	Introduction	
	

Our	 target	 in	 this	work	employing	heterocyclic	 compound	
of	 benzo[g]quinoline	 derivative	 as	 a	 typical	 precursor	 to	
prepare	new	heterocyclic	cyanine‐like	dyes	related	to	quinones	
expected	 to	 have	 a	 biological	 activity	 and	 other	 applications.	
This	is	due	to	the	fact	that	quinone	derivatives	are	widely	used	
as	 fungicides	 [1,2]	 and	 antibacterial	 agents	 [2‐4].	 Also	 a	 large	
number	of	chemicals	derived	from	quinone	as	the	basic	subunit	
exhibit	 prominent	 pharmacological	 applications	 such	 as	
antimalarial	 [5]	and	herbicidal	activity	[6].	On	the	other	hand,	
cyanine	 dyes	 have	 been	 extensively	 studied	 over	 the	 past	
century,	 mainly	 as	 photosensitizes	 for	 photography	 [7,8].	 In	
recent	 decades,	 other	 applications	 such	 as	 optical	 recording	
and	storage	media	 [9,10],	 visible	 and	near‐infrared	 laser	dyes	
[10‐12],	 biological	 fluorescent	 stains	 and	 probes	 [13]	 cyanine	
dyes	find	extensive	application	as	photo	sensitizers	in	the	blue	
green	 light	 [14].	 Some	 of	 these	 dyes	 are	 growth	 inhibitors	 to	
bacteria	 and	 to	 the	mitosis	 of	 fertilized	 sea	 urchin	 eggs	 [15].	
Additionally,	wide	applications	of	quinones	can	also	be	found	in	
the	 field	 of	 synthetic	 new	 heterocyclic	 derivatives	 [16]	 and	
cyanine	dyes	[8,17,18].		

In	 continuation	 of	 our	 interest	 by	 cyanine	 dyes,	 several	
types	of	cyanines	by	different	routes	have	been	synthsised	[19‐
24].	 Here,	 by	 using	 a	 joint	 theoretical	 and	 experimental	
approach,	 we	 demonstrate	 the	 correspondence	 between	
cyanines	 and	 the	 new	 class	 of	 cyanine‐like	 dyes	 involving	
heterocyclic	quinone	of	benzo[g]quinoline	derivatives	 [25,26].	
This	 paper	 describes	 the	 synthesis	 and	 spectral	 behavior	 of	
new	dimethine,	merocyanine,	monomethine	 and	 tetramethine	
cyanine‐like	 dyes	 incorporating	 4‐amino‐2‐methyl‐5,10‐dioxo‐
1,5,10,11‐tetra‐hydro‐benzo[g]quinoline‐3‐carbonitrile	 moiety	
[27].	
	
	

2.	Experimental		
	
2.1.	Instrumentation	
	

All	 melting	 points	 are	 uncorrected.	 Elemental	 analyses	
were	 carried	 out	 at	 the	 Micro	 analytical	 center	 (Assuit‐
University).	 The	 IR	 (KBr)	 spectra	 were	 determined	 with	
Perkin‐Elmer	 Infrared	 127B	 Spectrophotometer	 (Assuit	
University).	1H	NMR	spectra	were	recorded	with	a	Bruker	AMX‐
250	 spectrometer.	 The	 electronic	 absorption	 spectra	 were	
recorded	within	 the	wavelength	range	 (350‐700	nm)	on	6405	
UV/Visible	 recording	 spectrophotometer,	 Faculty	 of	 Science,	
Aswan,	 Egypt.	Mass	 spectra	were	 recorded	 on	 an	HpMs	6988	
spectrometer	(Cairo	University).		
	
2.2.	Synthesis	of	4‐amino‐2‐methyl‐5,10‐dioxo‐1,5,10,11‐
tetrahydrobenzo[g]quinoline‐3‐carbonitrile	(1)		
	

The	compound	1	was	carried	out	according	 to	Khalafallah	
et	al.,	2002	[27].	
	
2.3.	Synthesis	of	4‐amino‐5,10‐dioxo‐1,5,10,11‐tetrahydro‐
benzo[g]quinoline‐3‐carbonitrile‐merocyanine‐2(4)mono‐
methine	cyanine‐	like	dye	(2a),	4‐amino‐5,10‐dioxo‐1,5,10,	
11‐tetrahydro‐benzo[g]quinoline‐3‐carbonitrile‐mero‐
cyanine‐2(4)monomethine	cyanine‐like	dye	(2b),	4‐amino‐
5,10‐dioxo‐1,5,10,11‐tetrahydro‐benzo[g]quinoline‐3‐carbo	
nitrile‐merocyanine‐2(1)monomethine	cyanine‐	like	dye	
(2c)	
	

An	ethanolic	solution	of	equimolar	amount	of	compound	1	
and	 1‐ethyl(pyridinium,	 quinolinium	 and/or	 isoquinolinium)	
salts	 (0.01	 mol)	 were	 refluxed	 for	 7‐8	 hr,	 in	 the	 presence	 of	
piperidine	(3‐5	drops),	 filtered	hot,	concentrated	and	acidified	
with	acetic	acid.		

	



462	 Gomaa	et	al.	/	European	Journal	of	Chemistry	3	(4)	(2012)	461‐467	
	

	

 
	

Scheme	1	
	
	
The	precipitated	products	after	dilution	with	water	filtered	

off	 and	 crystallized	 from	 ethanol	 to	 give	 the	 corresponding	
products	(Scheme	1,	Tables	1,	2).	
	
2.4.	Synthesis	of	4‐amino‐2‐methyl‐5,10‐dioxo‐1,5,10,11‐
tetra‐hydrobenzo[g]quinoline	meso‐substituted‐3(2)	
dimethine	cyanine‐like	dye	(3a),	4‐amino‐2‐methyl‐5,10‐
dioxo‐1,5,10,11‐tetra‐hydrobenzo[g]quinoline	meso‐subs‐
tituted‐3(2)dimethinecyanine‐like	dye	(3b),	4‐amino‐2‐
methyl‐5,10‐dioxo‐1,5,10,11‐tetra‐hydrobenzo[g]quinoline	
meso‐substituted‐3(4)	dimethine	cyanine‐like	dye	(3c)	
	

Equimolar	 amounts	 of	 compound	 1	 and	 2‐methyl	
quaternary	salts	(α(γ)‐picoline	and/or	quinaldine)	ethyl	iodide	
(0.01	mol)	were	dissolved	 in	ethanol	 (30	mL)	 then	piperidine	
(3‐5	drops)	was	added.	The	reaction	mixture	was	refluxed	for	8	
hr,	 filtered	 hot,	 concentrated	 cooled	 and	 acidified	with	 acetic	
acid.	The	precipitated	products	after	dilution	with	water	were	
collected	 and	 crystallized	 from	 aqueous	 ethanol	 (Scheme	 1,	
Tables	1	and	2).	
	
2.5.	Synthesis	of	4‐amino‐2‐formyl‐5,10‐dioxo‐1,5,10,11‐
tetrahydrobenzo[g]quinoline‐3‐carbonitrile	(4)		
	

The	compound	1	was	refluxed	for	12‐15	hr,	with	selenium	
dioxide	 (0.02	mol)	 in	 dioxane	 (20	mL).	 The	 reaction	mixture	
was	filtered	hot	from	selenium	metal.	The	filtrate	was	allowed	
to	 cool	 and	 the	 filtrate	 was	 concentrated	 and	 the	 separated	
product	 dilution	 with	 water	 and	 cooling	 was	 filtered	 off,	

washed	with	water,	 and	 crystallized	 from	 ethanol	 (Scheme	 2,	
Tables	1	and	2).	
	
2.6.	Synthesis	of	4‐amino‐5,10‐dioxo‐1,5,10,11‐tetra‐hydro	
benzo[g]quinoline‐2(2)	dimethine	cyanine‐	like	dye	(5a),	4‐
amino‐5,10‐dioxo‐1,5,10,11‐tetra‐hydrobenzo[g]	quinoline‐
2(2)	dimethine	cyanine‐	like	dye	(5b),	4‐amino‐5,10‐dioxo‐
1,5,10,11‐tetra‐hydrobenzo[g]quinoline‐2(4)	dimethine	
cyanine‐like	dye	(5c)		
	

Equimolar	 amounts	 of	 compound	 4	 and	 2‐methyl	
heterocyclic	quaternary	salts	(α(γ)‐picoline	and/or	quinaldine)	
ethyl	iodide	(0.01	mol)	were	dissolved	in	ethanol	(30	mL)	then	
piperidine	 (3‐5	 drops)	 was	 added	 .The	 reaction	 mixture	 was	
refluxed	for	8	hr,	filtered	hot,	concentrated	cooled	and	acidified	
with	acetic	 acid.	The	precipitated	products	 after	dilution	with	
water	 were	 collected	 and	 crystallized	 from	 aqueous	 ethanol	
(Scheme	2,	Tables	1	and	2).	
	
2.7.	Synthesis	of	intermediate	compounds	(6a‐e)	
	

Equimolar	 amounts	 of	 compound	 4	 and	 acetaldehyde,	
acetone	 and/or	 acetophenone	 derivatives	 were	 refluxed	with	
30	mL	ethanol	and	(3‐5	drops)	of	piperidine	for	6‐8	hr,	filtered	
hot,	 concentrated,	 cooled	 and	 acidified	 with	 acetic	 acid.	 The	
precipitated	products	after	dilution	with	water	were	collected	
and	crystallized	from	aqueous	ethanol	(Scheme	3,	Tables	1	and	
2).	
	



Gomaa	et	al.	/	European	Journal	of	Chemistry	3	(4)	(2012)	461‐467	 463	
 

	
Table	1.	Characterization	of	compounds	(2a‐7g).	
Compound	No	 Yield,	%	 M.P.,	oC	 Mol.	Formula,	(M.wt.,	g)	 Elemental	Analysis,	%	Calculated	(Found)	 Mass,	m/z	

C H N	
2a	 70	 	>	300	 C22H18N4O2	

(370.41)	
71.35	
(71.47)		

4.86	
(4.78)	

15.14	
(15.22)	

370	

2b	 75	 240	 C26H20N4O2
(420.47)	

74.29
(74.37)		

4.76;
(4.71)	

13.33.	
(13.25)	

420

2c	 80		 >	300	 C26H20N4O2	
(420.47)	

74.29
(74.38)	

4.76
(4.67)	

13.33	
(13.42)	

420

3a	 60		 300	 C23H23N4O2I
(514.37)	

53.70
(53.57)	

4.47
(4.40)	

10.90	
(10.93)	

514

3b	 70		 200	 C27H25N4O2I	
	(564.43)	

57.44	
(57.39)	

4.43	
(4.52)	

9.93	
(9.88)	

564	

3c	 65		
	

200	 C23H23N4O2I		
(514.37)

53.70	
(53.53)

4.47	
(4.42)

10.90	
(10.91)	

514	

4	 50		 300	 C15H9N3O3	
(279.25)	

64.52	
(64.59)	

3.23	
(3.29)	

15.05	
(15.12)	

279	

5a	 60		 185	 C23H19N4O2I
(510.33)	

54.12
(54.19)	

3.73
(3.78)	

10.98	
(10.90)	

510

5b	 65		 230	 C27H21N4O2I	
(560)	

57.86
(57.95)	

3.75
(3.62)	

10.00	
(9.91)	

560

5c	 60		 300	 C23H19N4O2I
(510.33)	

54.12
(54.15)	

3.73
(3.75)	

10.98	
(10.94)	

510

6a	 60		 185	 C17H11N3O3	
(305.29)	

66.89	
(66.99)	

3.61	
(3.88)	

13.77	
(13.69)	

305	

6b	 65		 230	 C18H13N3O3	
(319.32)	

67.71	
(67.85)	

4.08	
(4.13)	

13.17	
(13.23)	

319	

6c	 58		 300	 C23H15N3O3
(381.39)	

72.44
(72.52)	

3.94
3.88)	

11.02	
(11.10)	

381

6d	 49		
	

220	 C24H17N3O4
(411)	

70.07
(70.12)	

4.14
(4.19)	

10.22	
(10.16)	

411

6e	 62		 222	 C23H14N4O5
	(426.39)

64.79
(64.72)

3.29
(3.36)

13.15	
(13.11)	

426

7a	 55		 >300	 C31H25N4O2I		
(612)	

60.78	
(60.69)	

4.09	
(4.18)	

9.15	
(9.19)	

612	

7b	 75		 260	 C35H27N4O2I		
(662)	

63.44	
(63.55)

4.08	
(4.13)

8.46	
(8.43)	

662	

7c	 51		 265	 C31H25N4O2I		
(612)	

60.78	
(60.71)	

4.09	
(4.22)	

9.15	
(9.20)	

612	

7d	 75		 260	 C36H29N4O3I	
(692)	

62.43
(62.52)	

4.19
(4.23)	

8.09	
(8.16)	

692

7e	 62		 263	 C35H26N5O4I	
(707)	

59.41
(59.48)	

3.68
(3.56)	

9.90	
(9.82)	

707

7f	 52	 260	 C29H23N4O2I
	(586)	

59.39
(59.45)	

3.93
(3.87)	

9.56	
(9.49)	

586

7g	 57	 260	 C30H25N4O2I	
(600)	

60	
(59.95)	

4.17	
(4.17)	

9.33	
(9.31)	

600	

	
	
	

 
Scheme	2	



464	 Gomaa	et	al.	/	European	Journal	of	Chemistry	3	(4)	(2012)	461‐467	
	
	
Table	2.	IR	and	1H	NMR	spectral	data	of	compounds	2a‐c,	3a‐b,	4,	5a‐b,	6a‐d,	and	7a‐g.	
Compound	No		 IR	(cm‐1)	 1H	NMR	(δ,	ppm)
2a	 2200	 (CN),	2900‐2800	 (N‐C2H5	 of	heterocyclic	 group),	

3400‐3100	(NH2),	1650	(Quinone	ring)	
1.00	(t,	3H,	CH3),	2.00	(s,	2H,	NH2),	2.69	(q,	2H,	CH2),	4.81	(s,	1H,	Quinone),	
5.60‐6.46	(m,	5H,	CH	+	4H,	Pyridine	ring),	7.64‐792	(m,	4H,	Ar),	2.85	(s,	1H,	
CH‐CN).	

2b	 2215	 (CN),	2900‐2800	 (N‐C2H5	 of	heterocyclic	 group),	
3400‐3100	(NH2),	1690	(Quinone	ring).		
	

1.13	(t,	3H,	CH3),	2.00	(s,	2H,	NH2),	3.10	(q,	2H,	CH2),	4.81	(s,	1H,	Quinone),	
5.50‐8.05	(m,	11H,	CH	+	Heterocyclic‐H	+	Ar‐H),	2.86	(s,	1H,	CH‐CN).	

2c	 2220	 (CN),	2900‐2800	 (N‐C2H5	 of	heterocyclic	 group),	
3400‐3100	(NH2),	1650	(Quinone	ring)	
	

‐	

3a	 1495	 (C=N),	 2924	 (ethyl	 iodide	 of	 heterocyclic	 salt),	
3400‐3100	(NH2),	1600‐1590	(Quinone	ring)		

1.71	(s,	3H,	CH3),	1.00	(t,	3H,	CH3 (Ethyl	iodide)),	2.00	(s,	4H,	2NH2),	2.59	(q,	
2H,	 CH2	 (Ethyl	 iodide)),	 4.81	 (s,	 1H,	 Quinone),	 4.52‐6.17	 (m,	 5H,	 CH	 +	
Pyridine	ring),	7.63‐8.05	(m,	4H,	Ar‐H),	2.85	(s,	1H,	CH‐CN).	

3b	 2922	 (Ethyl	 iodide	 of	 heterocyclic	 salt),	 1497	 (C=N),	
3400‐3100	(NH2),	1600‐1580	(Quinone	ring)	
	

‐	

4	 2200	 (CN),	 2922	 (Ethyl	 iodide	 of	 heterocyclic	 salt),	
3400‐3100	(NH2),	1598	(Quinone	ring),	1718	(CHO)	
	

2.00	(s,	2H,	NH2),	4.81	(s,	1H,	Quinone),	7.63‐8.05	(m,	4H,	Ar‐H),	9.68	(s,	1H,	
CHO),	2.86	(s,	1H,	CH‐CN).	

5a	 1500	 (C=N),	 1595	 (Conjugated	C=C),	 2220	 (CN),	 2923	
(Ethyl	 iodide	 of	 heterocyclic	 salt),	 3450‐3350	 (NH2),	
1600	(Quinone	ring)		

1.00	(t,	3H,	CH3),	2.00	(s,	2H,	NH2),	2.59	(q,	2H,	CH2),	4.81	(s,	1H,	Quinone),	
5.04‐6.39	(m,	6H,	CH=CH	+	Pyridine	ring),	7.64‐8.05	(m,	4H,	Ar‐H),	2.85	(s,	
1H,	CH‐CN).	

5b	 1500	 (C=N),	 1595	 (Conjugated	C=C),	 2200	 (CN),	 2922	
(Ethyl	 iodide	 of	 heterocyclic	 salt),	 3450‐3350	 (NH2),	
1600	(Quinone	ring)	

‐

6a	 1595	 (Conjugated	 C=C),	 2200	 (CN),	 3450‐3350	 (NH2),	
1600	(Quinone	ring),	1700	(C=O)		
	

2.00	(s,	2H,	NH2),	4.81	 (s,	1H,	Quinone),	6.29‐8.05	(m,	6H,	CH=CH	+	Ar‐H),	
9.68	(s,	1H,	CHO),	2.85	(s,	1H,	CH‐CN).	

6b	 1595	 (Conjugated	 C=C),	 2200	 (CN),	 3450‐3350	 (NH2),	
1600	(Quinone	ring),	1700	(C=O)	
	

‐

6c	 1595	 (conjugated	 C=C),	 2200	 (CN),	 3450‐3350	 (NH2),	
1620‐1600	(Quinone	ring),	1718	(C=O)		
	

2.00	(s,	2H,	NH2),	4.81	(s,	1H,	Quinone),	7.22‐8.05	(m,	11H,	CH=CH	+	Ar‐H),	
2.86	(s,	1H,	CH‐CN).	

6d	 1595	 (Conjugated	 C=C),	 2200	 (CN),	 3450‐3350	 (NH2),	
1620‐1600	(Quinone	ring),	1700	(C=O)	
	

2.00	 (s,	 2H,	 NH2),	 4.81	 (s,	 1H,	 Quinone),	 3.73	 (s,	 3H,	 OCH3),	 6.96‐8.05	 (m,	
10H,	CH=CH	+	Ar‐H),	2.82	(s,	1H,	CH‐CN).	

7a	 1487	 (Cyclic	 C=N),1595	 (Conjugated	 C=C),	 1620‐1600	
(Quinone	 ring),	 2200	 (CN),	 3450‐3350	 (NH2),	 2900	
(Ethyl	iodide	of	heterocyclic	salt)	

0.9	 (t,	 3H,	 CH3),	 2.00	 (s,	 2H,	NH2),	 1.4	 (q,	 2H,	 CH2),	 4.81	 (s,	 1H,	 Quinone),	
6.51‐9.30	(m,	16H,	CH=CH‐C=CH	+	heterocyclic	H	+	Ar‐H),	2.82	(s,	1H,	CH‐
CN).	

7b	 1487	 (cyclic	 C=N),1595	 (conjugated	 C=C),	 1620‐1600	
(Quinone	 ring),	 2200	 (CN),	 3450‐3350	 (NH2),	 2900	
(ethyl	iodide	of	heterocyclic	salt)		

0.9	 (t,	 3H,	 CH3),	 2.00	 (s,	 2H,	NH2),	 1.4	 (q,	 2H,	 CH2),	 4.81	 (s,	 1H,	 Quinone),	
6.51‐8.90	(m,	18H,	CH=CH‐C=CH	+	heterocyclic	H	+	Ar‐H),	2.80	(s,	1H,	CH‐
CN).	

7d	 1595	(Conjugated	C=C),	1487	(Cyclic	C=N),	2200	(CN),	
3450‐3350	(NH,	NH2),	1620‐1600	(Quinone	ring),	2929‐
2921	(Ethyl	iodide	of	heterocyclic	salt)	

‐	

7f	 1595	 (Conjugated	 C=C),	 1487	 (cyclic	 C=N),	 1620‐1600	
(Quinone	ring),	2200	(CN),	2929‐2921	(Ethyl	 iodide	of	
heterocyclic	salt),	3450‐3350	(NH2)		

0.9	 (t,	 3H,	 CH3),	 2.00	 (s,	 2H,	NH2),	 1.4	 (q,	 2H,	 CH2),	 4.81	 (s,	 1H,	 Quinone),	
6.51‐8.90	(m,	14H,	CH=CH‐CH=CH	+	heterocyclic	H	+	Ar‐H),	2.84	(s,	1H,	CH‐
CN).	

7g	 1595	(Conjugated	C=C),	1487	(Cyclic	C=N),	2200	(CN),	
3450‐3350	 (NH2),	 1620‐1600	 (Quinone	 ring),	 2929‐
2921	(Ethyl	iodide	of	heterocyclic	salt)

‐

	
	
2.8.	Synthesis	of	4‐amino‐5,10‐dioxo‐1,5,10,11‐tetrahydro	
benzo[g]quinoline‐3‐carbonitrile‐meso‐substituted‐2(2)	
tetra	methine	cyanine‐like	dye	(7a),	4‐amino‐5,10‐dioxo‐1,5,	
10,11‐tetrahydrobenzo[g]quinoline‐3‐carbonitrile‐meso‐
substituted‐	2(2)	tetramethine	cyanine‐like	dye	(7b),												
4‐amino‐5,10‐dioxo‐1,5,10,11‐tetrahydrobenzo[g]quinoline‐
3‐carbonitrile‐meso‐substituted‐	2(4)tetramethine	cyanine‐
like	dye	(7c),	4‐amino‐5,10‐dioxo‐1,5,10,11‐tetrahydrobenzo	
[g]	quinoline	‐3‐carbonitrile‐meso‐substituted‐2(2)tetra	
methine	cyanine‐like	dye	(7d),	4‐amino‐5,10‐dioxo‐1,5,10,	
11‐tetrahydrobenzo[g]quinoline‐3‐carbonitrile‐meso‐subs‐
tituted‐2(2)tetramethine	cyanine‐like	dye	(7e),	4‐amino‐
5,10‐dioxo‐1,5,10,11‐tetrahydrobenzo[g]quinoline‐3‐carbo‐
nitrile‐meso‐substituted‐2(2)	tetramethine	cyanine‐like	dye	
(7g)	
	

Equimolar	 amounts	 of	 compounds	 6a‐e	 and	 2‐methyl	
heterocyclic	quaternary	salts	(α(γ)‐picoline	and/or	quinaldine)	
ethyl	 iodide	with	(3‐4	drops)	of	piperidine	and	30	mL	ethanol	
refluxed	 for	 8	 hr,	 then	 filtered	 hot,	 concentrated	 cooled	 and	
acidified	 with	 acetic	 acid.	 The	 precipitated	 products	 after	
dilution	with	water	 filtered	 off	 and	 crystallized	 from	 aqueous	
ethanol	(Scheme	4,	Tables	1	and	2).	

	

3.	Results	and	discussion	
	
3.1.	Synthesis	
	

Reaction	 of	 equimolar	 ratios	 of	 4‐amino‐2‐methyl‐5,10‐
dioxo‐1,5,10,11‐tetra‐hydrobenzo[g]quinoline‐3‐carbonitrile	
compound	 1	 [27]	 with	 heterocyclic	 quaternary	 salts	 of	
(pyridinum,	 quinolinium	 and	 isoquinolinium)	 ethyl	 iodide	 in	
the	presence	of	piperidine	as	basic	catalyst	afforded	the	desired	
4‐amino‐5,10‐dioxo‐1,5,10,11‐tetrahydrobenzo[g]quinoline‐3‐
carbonitrile‐merocyanine2[4(1)]	 monomethine	 cyanine‐like	
dyes	2a‐c	 (Scheme	1).	Treating	on	 the	 latter	 compounds	2a‐c	
by	 conc.	 H2SO4	 resulted	 in	 liberating	 no	 iodine	 vapor	 on	
warming.	 This	 is	 due	 to	 that	 the	 above	 reaction	 between	 the	
compound	1	 and	 heterocyclic	 quaternary	 salts	 of	 (pyridinum,	
quinolinium	 and/or	 isoquinolinium)	 ethyl	 iodide	 was	
suggested	 to	 proceed	 through	 oxidative	 elimination	 via	
liberation	of	hydrogen	followed	by	hydrogen	iodide	molecules.	
On	the	other	hand,	reaction	of	compound	1	with	active	methyl	
heterocyclic	 quaternary	 salts	 (α()‐picolines	 and/or	
quinaldine)ethyl	 iodide	 gave	 the	 corresponding	 4‐amino‐2‐
methyl‐5,10‐dioxo‐1,5,10,11‐tetra‐hydrobenzo[g]quinolin‐
meso‐substituted‐3[2(4)]	 dimethine	 cyanine‐like	 dyes	 2a‐c	
(Scheme	1).		



Gomaa	et	al.	/	European	Journal	of	Chemistry	3	(4)	(2012)	461‐467	 465	
 

	

	
	

Scheme	3
	
	
The	 active	methyl	 group	 in	 compound	1	 is	 oxidized	using	

equimolar	 ratios	 of	 compound	 1	 and	 selenium	 dioxide	 in	
presence	 of	 dioxane	 as	 a	 solvent	 afforded	 the	 intermediate	
compound	 4‐amino‐2‐formyl‐5,10‐dioxo‐1,5,10,11‐tetrahydro	
benzo[g]quinoline‐3‐carbonitrile	4	[28,29]	(Scheme	2).	

Reaction	 of	 compound	 4	 with	 active	 methyl	 heterocyclic	
quaternary	 salts	 [α	 ()‐picolines	 and/or	 quinaldine]	 ethyl	
iodide	 gave	 the	 corresponding	 4‐amino‐5,10‐dioxo‐1,5,10,11‐
tetrahydrobenzo[g]quinoline‐3‐carbonitrile‐2[2(4)]dimethine	
cyanine‐like	dyes	5a‐c	(Scheme	2).	The	reaction	was	suggested	
to	proceed	through	condensation	reaction	between	the	formyl	
group	 of	 the	 compound	 4	 and	 active	 methyl	 group	 of	
heterocyclic	 quaternary	 salts	 [α()‐picolines	 and/or	
quinaldine]	ethyl	iodide	involving	dehydration	process.	

Condensation	 reaction	of	 equimolar	 ratios	of	 compound	4	
and	 acetaldehyde,	 acetone	 and/or	 acetophenone	 derivatives	
between	the	formyl	group	of	the	former	compound	and	active	
methyl	group	of	the	latter	ones	in	the	presence	of	piperidine	as	
basic	catalyst	and	ethyl	alcohol	as	solvent	takes	placed	to	afford	
the	intermediate	compounds	6a‐e,	(Scheme	3).	The	reaction	of	
latter	 compounds	 6a‐e	 with	 quaternary	 heterocyclic	 salts	 (α	
()‐picolines	 and/or	 quinaldine)	 ethyl	 iodide	 in	 presence	 of	
piperidine	 as	 basic	 catalyst	 and	 ethanol	 as	 solvent	 gave	 the	
corresponding	4‐amino‐5,10‐dioxo‐1,5,10,11‐tetra‐hydrobenzo	
[g]quinoline‐3‐carbonitrile‐meso‐substituted‐2[2(4)]‐tetra‐
methine	cyanine‐like	dyes	7a‐g,	(Scheme	4).		

The	 newly	 synthesized	 cyanine‐like	 dyes	 2a‐c,	3a‐c,	5a‐c	
and	7a‐g	are	highly	colored	compounds,	easily	soluble	in	polar	
organic	 solvents	 giving	 a	 green	 fluorescence	 but	 sparingly	

soluble	in	non‐polar	solvents.	Compounds	3a‐c,	5a‐c	and	7a‐g	
are	soluble	in	conc.	H2SO4	liberating	iodine	vapor	on	warming.		
	
3.2.	Spectral	behavior		
	

The	 electronic	 absorption	 spectral	 features	 (max	 and	 max	
values)	of	 the	newly	synthesized	cyanine‐like	dyes	2a‐c,	3a‐c,	
5a‐c	and	7a‐g	in	ethanol	solution	are	depicted	in	(Table	3).		

The	 visible	 absorption	 spectra	 of	 4‐amino‐5,10‐dioxo‐
1,5,10,11‐tetra‐hydrobenzo[g]quinone‐3‐carbonitrile	 mero‐
cyanine‐2[4(1)]	 monomethine	 cyanine‐like	 dyes	 2a‐c	 in	 95%	
ethanol	 undergo	 bathochromic	 or	 hypsochromic	 shifts	
depending	 on	 the	 nature	 of	 the	 quaternary	 salts	 residue	 and	
their	 linkage	 position.	 Thus,	 the	 electronic	 absorption	 spectra	
of	compound	2a	which	 incorporating	a	heterocyclic	of	N‐ethyl	
pyridin‐4‐ium,	 showed	 max	 at	 465	 nm.	 Substitution	 of	 a	
heterocyclic	 of	 N‐ethyl	 pyridin‐4‐ium	 in	 compound	 2a	 by	 a	
heterocyclic	 of	 N‐ethyl	 quinolin‐4‐ium	 in	 compound	 2b	
resulted	 in	 a	 bathochromic	 shift	 of	 max	 =	 5	 nm	 and	
appearance	 of	 a	 new	 absorption	 band,	 so	 compound	 2b,	
exhibited	max	=	470,	540	nm.	This	is	due	to	the	more	extensive	
π‐delocalization	and	extra	conjugation	within	the	extra	phenyl	
ring	in	quinolinium	ring	in	compound	2b.	

Additionally,	 changing	 the	 linkage	 position	 from	 4‐ium	 in	
compound	 2b	 which	 incorporating	 a	 heterocyclic	 of	 N‐ethyl	
quinolin‐4‐ium	to	1‐ium	in	compound	2c	which	incorporating	a	
heterocyclic	 of	 N‐ethyl	 isoquinolin‐1‐ium	 causes	 a	 hypso‐
chromic	shift	of	max	=	40,	5	nm,	so	compound	2c,	showed	max	
=	430,	535	nm.		
	



466	 Gomaa	et	al.	/	European	Journal	of	Chemistry	3	(4)	(2012)	461‐467	
	
	
Table	3.	The	electronic	absorption	spectra	of	new	synthesized	cyanine‐like	dyes	(2a‐c),	(3a‐c),	(5a‐c)	and	(7a‐g)	in	95%	EtOH	*.	
Compound	 max,	nm	(ε	max	mol‐1.cm‐1)	
Merocyanine	monomethine		
cyanine‐like	dyes,	2a‐c	

2a	
465	(2210)	

2b	
470	(2424)	
540	(1451)	

2c	
430	(1869)	
535	sh	(1507)	

Meso‐substituted	dimethine		
cyanine‐like	dyes,	3a‐c	

3a	
430	(1655)	
‐	

3b	
580	(723)	
690	(226)

3c	
450	(2029)	

Dimethine	
cyanine‐like	dyes,	5a‐c	

5a	
455	(1865)	

5b
570	(2628)	
660	(876)	

5c
455	(2064)	
‐	

Meso‐substituted‐tetramethine		
cyanine‐like	dyes,	7a‐g	

7a	
430	(1588)	

7b
520	(724)	
555	(481)	
600	(657)	
690	(379)	

7c
490	(2402)	

7d
525	(1366)	
560	(1975)	

7e
455	(1.068)	

7f	
510	(2150)	
550	(1715)	
	

7g
520	(2152)	
555	(1719)	

*	sh	=	shoulder	of	absorption	band.	
	
	

 
Scheme	4	



Gomaa	et	al.	/	European	Journal	of	Chemistry	3	(4)	(2012)	461‐467	 467	
 

	
This	is	due	to	the	more	extensive	π‐delocalization	within	4‐ium	
rather	than	1‐ium	linkage	position,	(Table	3).		

The	 electronic	 absorption	 spectra	 of	 4‐amino‐2‐methyl‐
5,10‐dioxo‐1,5,10,11‐tetrahydrobenzo[g]quinolin‐meso‐subs‐
tituted‐3[2(4)]dimethine	 cyanine‐like	 dyes	3a‐c	 and	 4‐amino‐
5,10‐dioxo‐1,5,10,11‐tetrahydrobenzo[g]quinoline‐3‐carbo‐
nitrile‐2[2(4)]dimethine	cyanine‐like	dyes	5a‐c	in	95%	ethanol	
exhibited	 absorption	 band	 which	 become	 more	 intense	 and	
with	 strong	 red	 shift	 on	 increasing	 the	 conjugation	 of	
quaternary	heterocyclic	residue.	

The	 absorption	 spectra	 of	 compound	 3a	 quaternary	
heterocyclic	 residue	 of	 1‐ethyl	 pyridinium‐2‐ium	 salt	 had	
absorbed	maxima	at	430	nm.	Replacing	on	the	pyridyl	residue	
by	 quinoline	 analogue,	 compound	 3b,	 the	 absorption	 band	
becoming	more	high	intense	concomitant	with	an	increasing	in	
the	number	of	absorption	band	and	showing	strong	red	shift	of	
max	 =	 150,	 260	 nm,	 max	 =	 580,	 690	 nm.	 This	 is	 due	 to	 the	
more	 extensive	 π	 delocalization	 within	 the	 molecule	 through	
the	extra	phenyl	ring	for	compound	3b.	

Additionally,	 changing	 the	 linkage	 position	 of	 heterocyclic	
quaternary	 residue	 from	 2‐ium	 in	 compound	 3a	 to	 4‐ium	 in	
compound	3c	resulted	in	a	bathochromic	shift	of	max	=	30	nm	
(3c)	quaternary	heterocyclic	residue	of	1‐ethyl	quinolinium	4‐
ium	 salt	 max	 =	 450	 nm.	 This	 is	 due	 to	 the	 increasing	 of	 the	
extension	conjugation	of	4‐linkage	pyridine	moiety	better	than	
2‐linkage	analogous,	(Table	3).		

Also	 the	 absorption	 spectra	 of	 compound	 5a	 quaternary	
heterocyclic	 residue	 of	 pyridinium	 2‐ium	 ethyl	 iodide	 had	
absorption	 maxima	 at	 445	 nm.	 On	 replacing	 quaternary	
heterocyclic	 residue	 of	 pyridinium	 2‐ium	 ethyl	 iodide	 in	
compound	 5a	 by	 quaternary	 heterocyclic	 residue	 of	
quinolinium‐2‐ium	 ethyl	 iodide	 in	 compound	 5b	 causes	 the	
strong	 red	 shift	 of	 max	 =	 125	 nm,	 concomitant	 with	 the	
appearance	of	a	new	absorption	band	at	max	=	660	nm.	This	is	
due	to	the	more	extensive	π‐delocalization	within	the	molecule.	

Additionally,	 changing	 the	 linkage	 position	 of	 heterocyclic	
quaternary	 residue	 from	 2‐ium	 in	 compound	 5a	 to	 4‐ium	 in	
compound	5c	resulted	in	a	bathochromic	shift	of	max	=	10	nm	
5c	max	=	455	nm.	This	is	due	to	the	increasing	of	the	extension	
conjugation	of	4‐linkage	pyridine	moiety	better	than	2‐linkage	
analogous,	(Table	3).		

The	 visible	 absorption	 spectra	 of	 4‐amino‐5,10‐dioxo‐
1,5,10,11‐tetrahydrobenzo[g]quinoline‐3‐carbonitrile‐meso‐
substituted‐2[2(4)]‐tetramethine	 cyanine‐like	 dyes	 7a‐g	 in	
95%	ethanol	 showed	absorption	band	undergo	batho	 (hypso)	
chromically	 shifted	 depending	 upon	 the	 heterocyclic	
quaternary	 residue,	 their	 linkage	position	 and	 the	 substituted	
derivatives.	 Thus,	 the	 absorption	 spectra	 of	 compound	 7a	
quaternary	heterocyclic	residue	of	1‐ethyl	pyridin‐2‐ium	ethyl	
iodide	 showed	 max	 =	 430	 nm.	 Substituting	 of	 heterocyclic	
quaternary	 residue	 1‐ethyl	 pyridin‐2‐ium	 ethyl	 iodide	 in	
compound	 7a	 by	 quaternary	 heterocyclic	 residue	 of	 1‐ethyl	
quinolin‐2‐ium	ethyl	iodide	in	compound	7b	resulted	in	strong	
bathochromic	 shift	 of	 max	 =	 90	 nm	 concomitant	 with	 the	
increasing	 number	 of	 absorption	 bands,	 7b,	 max	 =	 690,	 600,	
555,	 and	 520	 nm.	 This	 is	 due	 to	 the	 more	 extensive	 π	
delocalization	within	the	extra	phenyl	ring	in	compound	7b.		

Additionally,	 changing	 the	 linkage	 position	 from	 2‐ium	
linkage	 position	 in	 compound	 7a,	 quaternary	 heterocyclic	
residue	 of	 1‐ethyl	 pyridin‐2‐ium	 ethyl	 iodide	 to	 4‐ium	 in	
compound	 7c,	 quaternary	 heterocyclic	 residue	 of	 1‐ethyl	
pyridin‐4‐ium	 ethyl	 iodide	 resulted	 in	 a	 remarkable	
bathochromic	 shift	 of	 max	 =	 60	 nm,	 if	 compared	 with	
compound	7c,	max	=	 490	nm.	This	 is	due	 to	 the	 increasing	of	
the	 extension	 conjugation	 of	 4‐linkage	 pyridine	moiety	 better	
than	 2‐linkage	 analogous,	 (Table	 3).	 On	 the	 other	 hand,	
substitution	 of	 C6H5‐	 in	 compound	 7b	 by	 C6H4‐NO2	 in	
compound	7e	resulted	in	a	hypsochromic	shift	of	max	=	65	nm	
accompanied	with	 the	 disappearance	 of	 the	 other	 absorption	

bands.	This	is	due	to	the	strong	electron	withdrawing	effect	of	
NO2	 group.	Also,	 substitution	of	C6H4‐NO2	 in	 compound	7e	 by	
C6H4‐OCH3	 in	 compound	 7d	 causes	 a	 bathochromic	 shift	 of	
max	 =	 70	 nm	 accompanied	 with	 the	 appearance	 of	 a	 new	
absorption	band	located	at	560	nm.	This	is	due	to	the	electron	
donating	effect	of	CH3O	group	(Table	3).	
	
4.	Conclusion	
	

New	unsymmetrical	cyanine‐like	dyes	have	been	prepared	
incorporating	 heterocyclic	 quinone	 of	 benzo[g]quinoline	
derivative	 and	were	 identified	 by	 chemical	 and	 spectroscopic	
evidences	 (Elemental	 analyses,	 UV,	 IR,	 1H‐NMR	 and	 MS	
spectra).		
	
Acknowledgement	
	

We	 are	 thankful	 to	 the	 Department	 of	 Chemistry,	 Aswan‐
Faculty	of	Science,	Aswan	University	for	support	of	this	work.		
	
References	
	
[1]. Harinath,	B.	B.;	Subba,	R.	N.	V.	Proc.	Indian	Acad.	Sci.	1968,	67A,	31‐36.		
[2]. El‐Kanzi,	N.	A.	IOSR	J.	Appl.	Chem.	2012,	1(1),	18‐30.		
[3]. Shellhammer,	C.	W.	Petersen	S.	Ann.	1959,	624,	108‐119.		
[4]. Liao,	T.	K.;	Nyberg,	W.	H.;	Cheng,	C.	C.	Angew.	Chem.	(Int.	Edn.).	1967,	

6,	82‐82.		
[5]. Silva,	 A.	 J.	 M.;	 Netto,	 C.	 D.;	 Pacienza‐Lima,	 W.;	 Torres‐Santos,	 E.	 C.;	

Rossi‐Bergmann,	 B.;	 Maurel,	 S.;	 Valentin,	 A.;	 Costa,	 P.	 R.	 R.	 J.	 Braz.	
Chem.	Soc.	2009,	20,	176‐182.		

[6]. Gonzalez‐Ibarra,	M.;	Farfan,	N.;	Trejo,	C.;	Uribe,	S.;	Lotina‐Hennsen,	B.	
J.	Agric.	Food	Chem.	2005,	53,	3415‐3420.		

[7]. Khalafallah,	A.	K.;	Koraiem,	A.	 I.	M.;	Elmaghraby,	M.	A.;	 Shindy,	H.	A.	
Egypt	Chem.	1993,	36(3),	159‐166.		

[8]. Abd	El‐Aal,	R.	M.;	Koraiem,	A.	I.	M.;	El‐Deen	N.	S.	Dyes	Pigments	2004,	
63,	301‐314.		

[9]. Sturnmer,	 D.	 M.;	 Heseltine,	 D.	 W.;	 James,	 T.	 H.	 Sensitizing	 and	
desensitizing	dyes‐the	theory	of	photographic	processes,	4th	edn,	New	
York,	Macmillan,	1977;	Chapter	8.		

[10]. Matsuoka,	M.	Infrared	absorbing	dyes,	New	York,	Plenum	Press,	1990.		
[11]. Okawara,	M.;	Kitao,	T.;	Hirashima,	T.;	Matsuoka,	M.	Organic	colorants‐

a	 handbook	 of	 data	 of	 selected	 dyes	 for	 electro‐optical	 applications.	
Amsterdam,	Elsevier	Science	Publishers,	B.	V.,	1988.		

[12]. Fabian,	 J.;	Nakazumi,	H.;	Matsuoka,	M.	Chem.	Rev.	1992,	92(6),	1197‐
1226.		

[13]. Haugland,	 R.	 F.	 Handbook	 of	 fluorescent	 probes	 and	 research	
chemicals,	7th	edn.	Molecular	Probes,	Inc.,	1999.		

[14]. Broker,	L.	G.	S.;	Keyes,	G.	H.	J.	Am.	Chem.	Soc.	1935,	57,	2488‐2492.		
[15]. Shindy,	H.	A.;	Koraiem,	A.	I.	M.	Proc.	Indian	Acad.	Sci.	(Chem.	Sci.)	2002,	

114(2),	125‐136.		
[16]. Elkanzi	N.	A.	A.	Phosphorus	Sulfur	2008,	183(8),	2040‐2057.		
[17]. Presiado,	 I.;	 Karton‐Lifshin,	 N.;	 Erez,	 Y.;	 Gepshtein,	 R.;	 Shabat,	 D.;	

Huppert,	D.	J.	Phys.	Chem.	A	2012,	116(27),	7353‐7363.		
[18]. Koraiem,	A.	I.	M.;	Abu	El‐Hamd,	R.	M.;	Khalafallah,	A.	K.;	Hammam,	A.	

S.;	El‐Maghraby,	M.	A.;	Gomaa,	M.	M.	Dyes	Pigments	1996,	30(2),	 89‐
98.		

[19]. Koraiem,	A.	I.	M.;	Abd	El‐Aal,	R.	M.;	El‐Deen	N.	S.	Dyes	Pigments	2006,	
68,	235‐242.		

[20]. Koraiem,	A.	 I.	M.;	 Girgis,	M.	M.;	 Khalil,	 Z.	H.;	 EL‐Hamd,	R.	M.	 A.	Dyes	
Pigments	1991,	15(2),	89‐105.		

[21]. Ramos,	S.	S.;	Santos,	P.	F.;	Reis,	L.	V.;	Almeida,	P.	Dyes	Pigments	2002,	
53,	143‐152.		

[22]. Abd	El‐Aal,	R.	M.;	Younis,	M.	Bioorganic	Chem.	2004,	32(4),	193‐210.		
[23]. Abd	El‐Aal,	R.	M.;	Koraiem,	A.	I.	M.	Dyes	Pigments	2002,	54,	121‐129.		
[24]. Abd	El‐Aal,	R.	M.;	Koraiem,	A.	I.	M.;	Khalil,	Z.	H.;	El‐Kodey,	A.	M.	M.	Dyes	

Pigments	2005,	66,	201‐209.		
[25]. Ohira,	 S.;	 	 Hales,	 J.	 M.;	 	 Thorley,	 K.	 J.;	 Anderson,	 H.	 L.;	 Perry,	 J.	 W.;		

Breedas,	J.	J.	Am.	Chem.	Soc.	2009,	131	(17),	6099‐6101.		
[26]. Mykola,	 P.	 S.;	 Viktor,	 P.	 Y;	 Andriy,	 O.	 G;	 Olexiy,	 D.	 K;	 Yevgen,	 M.	 P;	

Yuriy,	P.	K.	Eur.	J.	Org.	Chem.	2012,	9,	1825‐1834.		
[27]. Khalafallah,	A.	K.;	Abd	El‐Aal,	R.	M.;	El	Kanzi,	N.	A.	A.	J.	Chin.	Chem.	Soc.	

2002,	49,	387‐396.		
[28]. Katritzky,	A.	R.;	Meth‐Cohn,	O.;	 Pattenden	G.	Comprehensive	organic	

functional	 group	 transformations:	 Synthesis	 of	 carbon	 with	 one	
heteroatom	attached	by	multiple	bond,	Pattenden	G.	Editor,	Elsevier	
Pub.,	1995,	vol.	3.		

[29]. Mshalker,	U.	C.;	Audi,	A.	A.	Indian	J.	Chem.	B	2006,	45,	967‐971.