Preparation, antibacterial activity and absorption spectra of pyrazolo-oxadiazine cyanine dyes

Article abstract of DOI:10.1002/jccs.200900125

Anew pyrazolo[4,3-e]-1,3,4-oxadiazine heterocyclic ring system was prepared and employed to synthesize cyanine dyes of different methine types, including monomethine (simple cyanine) and trimethine (carbocyanine). The antibacterial activity of all the new

Full text of DOI:10.1002/jccs.200900125

Journal of the Chinese Chemical Society, 2009, 56, 843-849
843
Preparation, Antibacterial Activity and Absorption Spectra of
Pyrazolo-Oxadiazine Cyanine Dyes
Fayez M. Eissa
Chemistry Department, Aswan Faculty of Science, Aswan 81528, Egypt
A new pyrazolo[4,3-e]-1,3,4-oxadiazine heterocyclic ring system was prepared and employed to syn-
thesize cyanine dyes of different methine types, including monomethine (simple cyanine) and trimethine
(carbocyanine). The antibacterial activity of all the newly synthesized compounds was investigated
against some bacterial strains. The electronic absorption spectra of the dyes were studied in absolute etha-
nol. The structure of all the synthesized compounds was identified via elemental and spectroscopic analy-
sis.
Keywords: Cyanine dyes; Pyrazolo-oxadiazine; Synthesis; Antibacterial activity; Absorption
spectra; Monomethine; Trimethine.
1. INTRODUCTION
reacted with a bimolar ratio of acetic acid azide of hydra-
zine or phenyl hydrazine (2a,b), in ethylene glycol as a sol-
vent and sodium bicarbonate as a basic catalyst, and af-
forded 2,5-dimethyl-4H(phenyl)pyrazolo[4,3-e]-1,3,4-
oxadiazine (3a,b), Scheme I.
Fused 1,3,4-oxadiazine heterocyclic systems are an
important class of organic compounds which have wide ap-
plications, especially in antimicrobial activity, as reported
in our previous work.1 Also, cyanine dyes2,3 are of great im-
portance due to their useful applications, such as in nucleic
acid detection,4 as optical sensors,5 photovoltaic devices,6
near infrared laser dyes,7 histological staining,8 and dyes
for polymers as well as sensitizers for various silver halide
emulsions.9 Hence, intense research activity has been de-
voted to report new heterocyclic ring systems with antibac-
terial activity,10-15 and their derived cyanine dyes of relative
stability, high molar extinction coefficients and high fluo-
rescent intensity.
Quaternization of (3a,b) using iodomethane pro-
duced the 3,6-diquaternized compounds (4a,b). Further re-
action of the 3,6-diquaternized compounds (4a,b) with a
bimolar ratio of N-methylquinolinium iodide salt, in etha-
nol and the presence of piperidine as catalyst, achieved the
2,5(4)-bis-monomethine cyanine dyes (5a,b) (Scheme I).
Additionally, the 3,6-diquaternized compounds (4a,b)
were reacted with a bimolar ratio of triethylorthoformate,
in ethanol containing piperidine as a basic catalyst, and
achieved the 2,5-di(2-diethoxy-ethane) compounds (6a,b)
as intermediates. Further reaction of the intermediates
(6a,b) with a bimolar ratio of N-methylquinaldinium io-
dide salt, in ethanol and the presence of piperidine, resulted
in the 2,5(2)-bis-trimethine cyanine dyes (7a,b), Scheme
II.
This work reports the synthesis of newly synthesized
cyanine dyes incorporating a pyrazolo-[4,3-e]-1,3,4-oxa-
diazine heterocyclic ring system as a new synthesis contri-
bution in this important field and investigates the antibacte-
rial activity of all the synthesized derivatives against se-
lected bacterial strains. Also, this work reports the elec-
tronic absorption spectra of the newly synthesized cyanine
dyes in absolute ethanol in order to elucidate their photo-
sensitization activity.
2.2. Antibacterial activity
The antibacterial activity of some selected newly syn-
thesized compounds, as representatives, against some bac-
terial strains, Pseudomonas, Serratia, Bacillus cereus,
Escherichia coli, and Staphylococcus citrus, was investi-
gated and the inhibition zone diameter IZD is recorded in
Table 1. The results revealed that the selected compounds
2. RESULTS AND DISCUSSION
2.1. Synthesis
4-Bromo-3-methyl-1-pheny-pyrazol-5-one (1) was

844 J. Chin. Chem. Soc., Vol. 56, No. 4, 2009
Eissa
Scheme I
Route to bis mono methine cyanine dyes incorporating pyrazolo-oxadiazine heterocyclic ring system
Fayez M. Eissa
Pyrazolo[4,3-e]-1,3,4-oxadiazine heterocyclic ring system was obtained from 4-bromo-3-methyl-1-pheny-
pyrazol-5-one and a bimolar ratio of acetic acid azide of hydrazine derivatives. A ring closure reaction, involv-
ing dehydration and dehydrobromination, was carried out. The resultant heterocyclic ring system was quater-
nized, and the quaternized compound was employed to establish bis mono methine cyanine dyes.
Scheme II
Route to bis tri methine cyanine dyes incorporating pyrazolo-oxadiazine heterocyclic ring system
Fayez M. Eissa

Pyrazolo-Oxadiazine Cyanine Dyes
J. Chin. Chem. Soc., Vol. 56, No. 4, 2009 845
Table 1. Antibacterial activity of the tested compounds against some bacterial strains (Fayez M. Eissa)
Staphylococcus.
citrus
Comp.
Pseudomonas
Serratia
Bacillus cereus
Escherichia coli
DMSO (control)
00.0
-
00.0
-
00.0
-
00.0
00.0
-
-
11.0 mm
++
12.0 mm
++
13.0 mm
++
00.0
14.0 mm
3a
3b
4a
4b
5a
5b
6a
6b
7a
7b
-
++
12.0 mm
++
11.0 mm
++
12.0 mm
++
00.0
11.0 mm
-
++
14.0 mm
++
16.0 mm
++
16.0 mm
++
00.0
12.0 mm
-
++
12.0 mm
++
12.0 mm
++
11.0 mm
++
00.0
00.0
-
00.0
-
-
14.0 mm
++
15.0 mm
++
13.0 mm
++
00.0
-
12.0 mm
++
11.0 mm
++
10.0 mm
+
16.0 mm
++
00.0
-
16.0 mm
++
00.0
15.0 mm
++
00.0
-
00.0
-
-
00.0
12.0 mm
++
11.0 mm
++
00.0
-
14.0 mm
-
-
18.0 mm
++
00.0
13.0 mm
++
00.0
-
16.0 mm
++
-
15.0 mm
++
13.0 mm
++
11.0 mm
++
11.0 mm
++
-
showed promising moderate antibacterial activity against
the given bacterial strains.
2.3. Absorption spectra
Photosensitization activity of the newly synthesized
cyanine dyes was determined by studying their electronic
visible absorption spectral behaviour in absolute ethanol.
The dyes were thought to be better photosensitizers when
they absorb the visible light, to initiate the electronic transi-
tions, at higher wavelengths (bathochromic and/or red
shifted dyes). Consequently, the photosensitization of these
dyes decreases when they absorb light at shorter wave-
lengths (hypsochromic and/or blue shifted dyes).
The starting compounds 3a,b showed a significant
activity of the pyrazolo[4,3-e]-1,3,4-oxadiazine heterocy-
clic system which is more pronounced in 3a than 3b due to
the importance of the N-hydrogen over N-phenyl that in-
troduced a facile linkage between the compound and the
outer tissue of the bacterial cells.
Additionally, the 3,6-diquaternized compounds 4a,b
showed more intensified antibacterial activity if compared
with that of the non-quaternized 3a,b. This in turn may
point out the great role of quaternary nitrogen atoms in
blocking some important functions of bacterial growth and
multiplication.
The electronic absorption spectra of the monome-
thine cyanine 5a,b (lmax: 529, 537 nm; emax: 12300, 12900
mol-1 cm2); trimethine cyanine 7a,b (lmax: 673, 677 nm;
emax: 21100, 22000 mol-1 cm2), respectively, in absolute
ethanol showed absorption maxima in the visible region.
The positions and molar extinction coefficients of these
maxima were influenced by the nature of the N-substituent
present in the oxadiazine heterocycle; hence, it is clear that
the N-phenyl in dyes (5b and 7b) caused bathochromic
shifts if compared with N-hydrogen in dyes (5a and 7a) due
to an extra conjugation present in the phenyl ring. Also, the
ethanol solutions of these dyes were associated with great
Also, the antibacterial activity of cyanine dyes and
their intermediates showed stronger activity due to the ac-
cumulative staining property and the presence of the trans-
methine unites that introduced further linkages with the
bacterial function sites. This staining property may inhibit
the bacterial growth and exert a bactericidal function, be-
sides all the pre-mentioned functions, through staining the
nutrition media.

846 J. Chin. Chem. Soc., Vol. 56, No. 4, 2009
Eissa
visible fluorescence (green in the case of monomethine and
greenish red in the case of trimethine); this in turn showed
the promising applicability of these dyes in nucleic acid de-
tection as well as in fields related to emission spectral be-
havior.
ysis: (Calculated %) C: 71.04, H: 5.30, N: 18.41, O: 5.25
(Found %) C: 71.12, H: 5.24, N: 18.39, O: 5.25; 1HNMR
(400 MHz, DMSO-d6): 1.80 (s, 3H-CH3), 2.29 (s, 3H-
CH3), 6.45-7.80 (m, 10H-Ar); 13CNMR (400 MHz, DMSO):
11.90 (CH3), 22.19 (CH3), 118.87 (2CH), 119.05 (CH),
123.19 (2CH), 127.00 (CH), 129.03 (2CH), 129.83 (2CH),
131.09 (C), 132.89 (C), 138.11 (C), 140.71 (C),146.01 (C),
150.97 (C).
3. EXPERIMENTAL
3.1. General
Melting points were recorded on an electro-thermal
Gallenkanp melting point apparatus and were uncorrected.
Elemental and spectroscopic analyses were carried out in
the Micro Analytical Center of Cairo University. The fine
chemicals were purchased from Aldrich Co. and the or-
ganic solvents were of spectroscopic grades. The reactions
were monitored using TLC and all the resultant compounds
were crystallized and then extra purified using a column
chromatography technique.
3.2.2. Synthesis of 2,3,5,6-tetramethyl-4H(Phenyl)-7-
phenylpyrazolo[4,3-e]-1,3,4-oxadiazine 3,6-di-
quaternized iodide salts (4a,b)
General procedure: A pure crystallized sample of
(3a,b) (0.01 mol) was dissolved in an excess of iodoethane
(10 mL) and heated gently under reflux at low temperature
(40-60 oC) for 1 hour. The solvent was evaporated and the
residue (4a,b) was collected and crystallized from ethanol.
These compounds were extra purified using column chro-
matography on silica gel eluting with ethyl acetate/hexanes
(30/70).
3.2. Synthesis
3.2.1. Synthesis of 2,5-dimethyl-4H(Phenyl)-7-phenyl-
pyrazolo[4,3-e]-1,3,4-oxadiazine (3a,b)
4a: (Y: 97%); M.P.: 181 ºC; Mol. F.: C14H18I2N4O;
Mol. Wt.: 511.13; m/z (FABMS): 512.96; Elemental anal-
ysis: (Calculated %) C: 32.83, H: 3.54, I: 49.56, N: 10.94,
O: 3.12 (Found %) C: 32.78, H: 3.60, I: 49.55, N: 10.89, O:
3.17; 1HNMR (400 MHz, DMSO-d6): 1.96 (s, 3H-CH3),
2.07 (s, 3H-CH3), 2.31 (s, 3H-CH3), 2.70 (s, 3H-CH3), 4.73
(s, NH), 6.59-7.74 (m, 5H-Ar); 13CNMR (400 MHz,
DMSO): 13.56 (CH3), 16.12 (CH3), 25.71 (CH3), 28.00
(CH3), 121.00 (3CH), 129.67 (2CH), 140.09 (2C), 144.19
(C), 149.99 (C), 157.00 (C).
General procedure: 4-Bromo-3-methyl-1-pheny-
pyrazol-5-one (1) (0.01 mol) and an equimolar ratio of ace-
tic acid azide of hydrazine or phenyl hydrazine (2a,b) was
refluxed in ethylene glycol for 1 hour until the mixture at-
tained a faint red color. Five milliliters of 20% aqueous so-
dium bicarbonate solution was added to the reaction mix-
ture which was then refluxed again for a further 4 hours.
The reaction mixture was filtered off while hot to remove
unreacted materials, poured into an ice water mixture with
continuous shaking. The precipitated compounds (3a,b)
were filtered, washed with cold water, dried and crystal-
lized from ethanol. These compounds were extra purified
using column chromatography on silica gel eluting with
ethyl acetate/hexanes (20/ 80).
4b: (Y: 92%); M.P.: 190 ºC; Mol. F.: C20H22I2N4O;
Mol. Wt.: 588.22; m/z (FABMS): 589.99; Elemental anal-
ysis: (Calculated %) C: 40.84, H: 3.77, I: 43.15, N: 9.52,
O: 2.72 (Found %) C: 40.77, H: 3.83, I: 43.14, N: 9.47, O:
2.76; 1HNMR (400 MHz, DMSO-d6): 1.70 (s, 3H-CH3),
2.11 (s, 3H-CH3), 2.40 (s, 3H-CH3), 2.41 (s, 3H-CH3),
6.21-7.72 (m, 10H-Ar); 13CNMR (400 MHz, DMSO):
11.91 (CH3), 15.00 (CH3), 27.21 (CH3), 32.11 (CH3),
115.11 (2CH), 118.98 (CH), 128.00 (2CH), 128.90 (3CH),
129.90 (2CH), 137.32 (C), 144.41 (C), 148.45 (C), 151.66
(C), 155.00 (C), 1.8599 (C).
3a: (Y: 69%); M.P.: 176 ºC; Mol. F.: C12H12N4O;
Mol. Wt.: 228.25; m/z (FABMS): 229.10; Elemental anal-
ysis: (Calculated %) C: 63.15, H: 5.30, N: 24.55, O: 7.01
(Found %) C: 63.07, H: 5.24, N: 24.48, O: 7.09; 1HNMR
(400 MHz, DMSO-d6):1.80 (s, 3H-CH3), 2.29 (s, 3H-CH3),
3.93 (s, NH), 6.46-7.31 (m, 5H-Ar); 13CNMR (400 MHz,
DMSO): 11.90 (CH3), 22.19 (CH3), 116.87 (2CH), 119.05
(CH), 123.19 (2CH), 131.09 (C), 132.89 (C), 138.11 (C),
140.71 (C), 150.97 (C).
3.2.3. Synthesis of 3,6-dimethyl-4H(Phenyl)-7-phenyl-
pyrazolo[4,3-e]-1,3,4-oxadiazine-2,5(4)-bis-mono-
methine cyanine dyes (5a,b)
3b: (Y: 73%); M.P.: 184 ºC; Mol. F.: C18H16N4O;
Mol. Wt.: 304.35; m/z (FABMS): 305.15; Elemental anal-
General procedure: The 3,6-diquaternized com-
pounds (4a,b) (0.01 mol) and bimolar ratios of N-methyl-

Pyrazolo-Oxadiazine Cyanine Dyes
J. Chin. Chem. Soc., Vol. 56, No. 4, 2009 847
quinolinium iodide salt were refluxed in ethanol (50 mL)
containing piperidine (1 mL) for 6 hours. The reaction
mixture was filtered off while hot to remove unreacted
materials, cooled, poured into an ice-water mixture with
continuous shaking till complete precipitation and neu-
tralized with acetic acid. The precipitates (5a,b) were fil-
tered, washed with water, dried and crystallized from eth-
anol. These compounds were extra purified using column
chromatography on silica gel eluting with ethyl acetate/
hexanes (25/75).
pounds (6a,b) were extra purified using column chroma-
tography on silica gel eluting with ethyl acetate/hexanes
(20/80).
6a: (Y: 89%); M.P.: 189 ºC; Mol. F.: C24H38I2N4O5;
Mol. Wt.: 716.39; m/z (FABMS): 717.10; Elemental anal-
ysis: (Calculated %) C: 40.24, H: 5.35, I: 35.43, N: 7.82,
O: 11.17 (Found %) C: 40.20, H: 5.34, I: 35.41, N: 7.76, O:
1
11.22; HNMR (400 MHz, DMSO-d6): 1.08 (T, 12H-
4CH3), 2.39 (d, 4H-2CH2), 2.83 (s, 6H-2CH3), 3.46 (q,
8H-4CH2), 4.09 (s, NH), 4.39 (t, 2H-2CH), 6.98-7.99 (m,
5H-Ar); 13CNMR (400 MHz, DMSO-d6): 16.56 (4CH3),
24.11 (CH2), 30.89 (CH2), 36.24 (2CH3), 63.22 (4CH2),
94.21 (CH), 99.72 (CH), 126.00 (3CH), 129.00 (2CH),
137.45 (C), 142.49 (C), 147.19 (C), 149.12 (C), 154.56
(C).
5a: (Y: 80%); M.P.: 203 ºC; Mol. F.: C34H32I2N6O;
Mol. Wt.: 794.47; m/z (FABMS): 795.08; Elemental anal-
ysis: (Calculated %) C: 51.40, H: 4.06, I: 31.95, N: 10.58,
O: 2.01 (Found %) C: 51.43, H: 3.99, I: 31.93, N: 10.56, O:
2.07; 1HNMR (400 MHz, DMSO-d6): 2.39 (s, 6H-2CH3),
2.579 (s, 6H-2CH3), 4.600 (s, NH), 4.98 (s, H-CH), 5.56 (s,
H-CH), 6.270-7.98 (m, 17H-Ar); 13CNMR (400 MHz,
DMSO-d6): 34.33 (CH3), 41.00 (CH3), 47.51 (2CH3),
78.22 (CH), 97.3 (C), 109.20 (CH), 115.91 (2CH), 118.00
(2CH), 119.90 (CH), 123.00 (2C), 125.55 (3CH), 128.00
(4CH), 129.90 (4CH), 134.99 (C), 139.49 (2C), 146.09
(2C), 151.89 (C), 156.99 (2C), 162.00 (C).
6b: (Y: 92%); M.P.: 201 ºC; Mol. F.: C30H42I2N4O5;
Mol. Wt.: 792.49; m/z (FABMS): 793.13; Elemental anal-
ysis: (Calculated %) C: 45.47, H: 5.34, I: 32.03, N: 7.07,
O: 10.09 (Found %) C: 45.44, H: 5.29, I: 32.01, N: 7.05, O:
1
10.13; HNMR (400 MHz, DMSO-d6): 1.11 (T, 12H-
4CH3), 2.32 (d, 4H-2CH2), 2.76 (s, 6H-2CH3), 3.39 (q,
8H-4CH2), 4.29 (t, 2H-2CH), 7.22-8.13 (m, 10H-Ar);
13CNMR (400 MHz, DMSO-d6): 17.98 (4CH3), 26.45
(CH2), 33.08 (CH2), 36.99 (2CH3), 66.00 (4CH2), 97.07
(CH), 103.84 (CH), 128.90 (6CH), 134.67 (4CH), 139.00
(C), 141.00 (C), 145.17 (C), 148.00 (C), 150.99 (C),
157.11 (C).
5b: (Y: 89%); M.P.: 211 ºC; Mol. F.: C40H36I2N6O;
Mol. Wt.: 870.56; m/z (FABMS): 871.11; Elemental anal-
ysis: (Calculated %) C: 55.19, H: 4.17, I: 29.15, N: 9.65,
O: 1.84 (Found %) C: 55.16, H: 4.09, I: 29.14, N: 9.61, O:
1.89; 1HNMR (400 MHz, DMSO-d6): 2.49 (s, 6H-2CH3),
2.63 (s, 6H-2CH3), 5.32 (s, 2H-2CH), 6.10-8.60 (m, 22H-
Ar); 13CNMR (400 MHz, DMSO): 33.20 (CH3), 39.10
(CH3), 47.90 (2CH3), 85.93 (CH), 96.00 (C), 107.10 (CH)
113.20 (4CH), 117.90 (2CH), 120.00 (2CH), 123.10 (2CH
+ 2C), 124.40 (2CH), 126.90 (4CH), 128.80 (4CH + C),
135.30 (2C), 141.00 (2C), 144.10 (2CH), 151.90 (C),
156.80 (2C), 163.80 (C).
3.2.5. Synthesis of 3,6-dimethyl-4H(Phenyl)-7-phenyl-
pyrazolo[4,3-e]-1,3,4-oxadiazine-2,5(2)-bis-tri-
methine cyanine dyes (7a,b)
General procedure: The intermediate compounds
(6a,b) (0.01 mol) and bimolar ratios of N-methylquin-
aldinium iodide salt were refluxed in ethanol (50 mL) con-
taining piperidine (1 mL) for 8 hours. The reaction mix-
tures that turned dark violet with green fluorescence at the
end of the reaction course were filtered off while hot,
cooled, poured into an ice-water mixture with continuous
shaking till complete precipitation and neutralized with
acetic acid. The precipitated products (7a,b) were filtered,
washed with water, dried and crystallized from ethanol.
These compounds were extra purified using column chro-
matography on silica gel eluting with ethyl acetate/hexanes
(30/70).
3.2.4. Synthesis of 2,5-di-[2-diethoxyethane]-3,6-di-
methyl-4H(Phenyl)-7-phenylpyrazolo[4,3-e]-
1,3,4-oxadiazine 3,6-diquaternized iodide salts
(6a,b)
General procedure: The di-quaternized salts (4a,b)
(0.01 mol) and bimolar ratios of triethylorthoformate were
refluxed in ethanol (50 mL) containing piperidine (1 mL)
for 4 hours. The reaction mixtures were filtered off to re-
move unreacted materials, poured into an ice-water mix-
ture, neutralized with acetic acid, stirred vigorously, fil-
tered, dried, and crystallized from ethanol. These com-
7a: (Y: 91%); M.P.: 223 ºC; Mol. F.: C38H36I2N6O;
Mol. Wt.: 846.54; m/z (FABMS): 847.11; Elemental anal-

848 J. Chin. Chem. Soc., Vol. 56, No. 4, 2009
Eissa
ysis: (Calculated %) C: 53.91, H: 4.29, I: 29.98, N: 9.93,
O: 1.89 (Found %) C: 53.86, H: 4.25, I: 29.97, N: 9.90, O:
1.96; 1HNMR (400 MHz, DMSO-d6): 2.64 (s, 6H-2CH3),
2.99 (s, 6H-2CH3), 3.98 (s, NH), 4.23 (d, H-CH), 5.51 (d,
H-CH), 6.01 (t, 2H-2CH), 6.43 (d, 2H-2CH), 6.99-8.46 (m,
17H-Ar); 13CNMR (400 MHz, DMSO): 39.01 (CH3),
43.90 (CH3), 45.01 (2CH3), 70.71 (CH), 94.23 (C), 104.33
(CH), 113.00 (2CH), 119.43 (5CH), 124.77 (2CH), 127.40
(6CH + 2C), 133.00 (4CH + C), 136.99 (C), 139.09 (3C),
142.00 (CH), 149.09 (2C), 153.11 (C), 163.32 (C).
7b: (Y: 96%); M.P.: 227 ºC; Mol. F.: C44H40I2N6O;
Mol. Wt.: 922.64; m/z (FABMS): 923.14; Elemental anal-
ysis: (Calculated %) C: 57.28, H: 4.37, I: 27.51, N: 9.11, O:
1.73 (Found %) C: 57.22, H: 4.33, I: 27.50, N: 9.05, O:
1.77; 1HNMR (400 MHz, DMSO-d6): 2.77 (s, 6H-2CH3),
2.80 (s, 6H-2CH3), 4.02 (d, H-CH), 5.64 (d, H-CH), 6.30 (t,
2H-2CH), 6.66 (d, 2H-2CH), 7.30-8.78 (m, 22H-Ar);
13CNMR (400 MHz, DMSO-d6): 37.99 (CH3), 43.00 (CH3),
45.65 (2CH3), 73.00 (CH), 97.11 (C), 108.00 (CH), 116.32
(2CH), 120.00 (5CH), 126.13 (3CH), 128.09 (8CH + 2C),
132.79 (6CH + C), 136.21 (2C), 138.97 (3C), 144.55 (CH),
147.97 (2C), 157.10 (C), 166.00 (C).
IZD = 2-10 mm beyond control = + (low activity).
IZD = 11-24 mm beyond control = ++ (moderate ac-
tivity).
IZD = 25-35 mm beyond control = +++ (high activ-
ity).
3.4. Absorption spectroscopy
The electronic visible absorption spectra of the pre-
pared cyanine dyes were studied in absolute ethanol and
measured on a Shimadzu UV/visible 160-A spectro-pho-
tometer. The stock solution was about 1 ´ 10-3 Mole/L; the
lower molarities were obtained by accurate dilution.
4. CONCLUSION
In summary, the new heterocyclic system and its de-
rivatives exhibited a broad spectrum of antibacterial activ-
ity including a growth inhibition of some of the selected
bacterial strains, (Pseudomonas, Serratia, Bacillus cereus,
and Staphylococcus citrus). These results could be a poten-
tial lead to further development of new antibacterial candi-
dates. The electronic visible absorption spectra of the
newly synthesized cyanine dyes showed strong absorption
maxima of high molar extinction coefficient, thus revealing
great photosensitization activity.
3.3. Antibacterial activity
The antibacterial activity was established in the Mi-
crobiology Division of the Micro Analytical Center of
Cairo University, via the diffusion plate method.16-18 A bot-
tomless cylinder containing a measured quantity (1 mL,
mg/mL) of the sample was placed on a plate (9 cm diame-
ter) containing a solid bacterial medium (nutrient agar
broth) which was heavily seeded with the spore suspension
of the test organism. After incubation for 24 hours, the
IZD, (the zone diameter within which the inhibition of the
bacterial growth occurred by the influence of the sample
under investigation), was taken as a measure of the inhibi-
tory power of the sample against the particular test organ-
ism.
Received February 20, 2009.
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The solvent used was DMSO.
Concentration of the sample was 50 µg/mL.

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