K.S. Lokesh et al. / Polyhedron 28 (2009) 1022–1028
1023
phthalocyanine. These substituted platinum phthalocyanines
have been prepared for the first time by using a novel route,
with high purity. These compounds were characterized by ele-
mental analysis, UV–Vis and infrared spectral analysis, magnetic
susceptibility, powder X-ray diffraction and thermogravimetric
studies. The electrical conductivity measurements of these com-
pounds were analysed in the temperature range from ambient
to 473 K.
to remove the unreacted impurities. The product was then dried at
45 °C in an oven.
Anal. Calc. for platinum phthalocyanine, C32
16 8
H N Pt: C, 54.32;
H, 2.26; N, 15.84. Found: C, 54.76; H, 2.35; N, 15.69%. IR absorption
ꢀ1
bands (cm ): 717 (s), 724 (w), 736 (s), 752 (w), 869 (s), 949 (w),
1068 (w), 1093 (m), 1118 (s), 1319 (s), 1359 (m), 1437 (w), 1481
(s), 1520 (s), 3061 (m). Yield: 93%.
2.3. Platinum tetranitro phthalocyanine
2
. Materials and methods
One gram (5.8 mmol) of nitrophthalonitrile and 0.45 g
(
1.34 mmol) of platinic(IV) chloride were mixed well and then
Platinic(IV) chloride, phthalonitrile, nitrophthalonitrile were of
placed in a vessel with a small opening at the top. This vessel
was then placed in a microwave and irradiated with at a power
of 540 W for 2 min, whereupon the compound started to turn a
slight bluish color, and then at 720 W for 3 min to complete the
reaction. The compound turned totally to a bluish black color.
The crude product was ground well and washed with ethanol
and water, and then with acetone in a Soxhlet extractor with
AR grade, obtained from Fluka, USA and were used as received.
All the other reagents used were of analytical grade and were used
as such without purification, unless otherwise mentioned.
2.1. Physico-chemical measurements
A domestic L.G. microwave oven, model MG-555F (max. 900 W,
2
5 mL volume three times to remove the unreacted impurities.
min. 180 W, L.G. electronics, India) with five select power levels
was used for carrying out the reactions. Elemental analysis for car-
bon, hydrogen and nitrogen were done using a Vario EL-III CHN & S
Elemental Analyser, Analytikjena, Germany. Electronic spectra in
the UV–Vis region were recorded in analytical grade 28 M sulfuric
acid using a Systronics type – 117 model spectrophotometer with
The product was then dried at 45 °C in an oven.
Anal. Calc. for platinum(II) tetranitro phthalocyanine,
C
1
1
32 12 12 8
H N O Pt: C, 43.29; H, 1.35; N, 18.94. Found: C, 42.97; H,
.38; N, 19.15%. IR absorption bands (cm ): 3068 (m), 1610 (m),
524 (s), 1483 (m), 1338 (s), 1252 (m), 1132 (s), 1084 (s), 931
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(
m), 846 (s), 748 (s), 730 (s), 671 (m). Yield: 90%.
1
cm silica cells, Systronics, Ahmedabad, India. IR spectra were re-
corded in potassium bromide using a Shimadzu 8201 PC FT-IR
spectrometer, Japan. Magnetic susceptibility measurements were
done using a Gouy magnetic balance consisting of a NP-53 electro-
magnet with a DC power supply, type NP 1053, and a Keroy semi-
micro balance, supplied by the Universal Scientific Company,
Mumbai, India. Pure mercury tetrathiocyanato cobaltate(II) was
synthesized and used as a calibration standard [21]. Thermogravi-
metric analyses were done at the National Institute of Technology,
Tiruchirapalli, India, using a TGA 7 Analyser, Perkin–Elmer, USA.
Two to five milligram of the sample was used for the analysis
and a heating rate of 10 °C/min was used in air atmosphere at a
flow rate of 100 ml/min. A JEOL-JDX-8P X-ray diffractometer with
2
.4. Platinum tetramino phthalocyanine
For the preparation of the amino derivative of platinum, a simi-
lar procedure as used by Achar et al. to synthesize cobalt tetramino
phthalocyanine [8] was followed, with a slight modification. 1.0 g
(
1.13 mmol) of platinum tetranitro phthalocyanine was dissolved
in a 50 ml aqueous solution containing 2.5 g (10.42 mmol) of so-
dium sulfide nonahydrate. The slurry was stirred at 50 °C for 3 h.
Then, the bluish complex was separated and washed repeatedly
with 0.5 M hydrochloric acid, 1 M sodium hydroxide solution and
finally with distilled water until the filtrate was neutral to litmus
paper. The dark bluish green product was dried in an oven at 363 K.
Anal. Calc. for platinum(II) tetramino phthalocyanine,
Cu K
a radiation (k = 1.934 Å) was used to study the powder X-
ray diffraction pattern of the samples. Powdered complexes were
compressed into pellets of 1.3 cm diameter and thickness ranging
from 0.15 to 0.25 cm, using a Perkin–Elmer KBr Die under a pres-
32 20
C H N12Pt: C, 50.07; H, 2.61; N, 21.90. Found: C, 50.38; H, 2.54;
ꢀ
1
N, 21.76%. IR absorption bands (cm ): 3354 (w), 3225 (w), 3057
w), 1613 (s), 1490 (s), 1328 (s), 1122 (m), 1101 (m), 1033 (w),
62 (m), 867 (w), 745 (s). Yield: 88%.
2
(
9
sure of 500 kg/cm . A KBr press, Techno Search Instruments, Thane,
India, was used for applying the pressure. The diameter and thick-
ness of the pellets were determined by using a screw gauge, read-
able up to 0.005 cm. Conducting silver paint (ELTECKS preparation
No. 1228-C) was coated on both flat surfaces of the pellets and the
electrical contacts to the samples were made using the same silver
paint to the electrodes. The electrical contacts were checked to ver-
ify the ohmic connection and resistance measurements were done
from room temperature to 473 K using a DOT 402 Digital Milli
Ohm Meter and a DOT 425 Insulation Resistance Tester, Bhandari
Electronics and Electricals, Bangalore, India.
3. Results and discussion
Platinum phthalocyanine and the tetranitro and tetramino
derivatives were synthesized with very good quantitative yields,
88–93%. These phthalocyanines are dark bluish to greenish in col-
or. The elemental analysis for carbon, hydrogen and nitrogen
agreed very well with the theoretical calculations, indicating the
very good purity of the synthesized compounds. The microwave
radiations were carried out at different power levels, ranging from
180 to 900 W for different periods of time to evaluate the optimum
conditions for the synthetic procedures. Completion of the reaction
under the given microwave power was followed by recording FT-IR
spectra at different time intervals. The reactions were carried in a
microwave oven until the C„N group stretching around
2230 cm disappeared. The basic reaction and the structure of
the synthesized complexes are as shown in Scheme 1. It is clear
from the reaction conditions that microwave synthesis is consider-
ably more advantageous with respect to the time required for the
completion of the reaction compared to the conventional method.
The synthetic yields are also found to be fairly good. Achar et al.
2.2. Platinum phthalocyanine
One gram (7.8 mmol) of phthalonitrile and 0.5 g (1.5 mmol) of
platinic(IV) chloride were mixed well and then placed in a vessel
with a small opening at the top. This vessel was then placed in a
microwave and irradiated with at a power of 360 W for 2 min,
whereupon the compound started to turn a slight bluish color,
and then at 720 W for 3 min to complete the reaction. The com-
pound turned totally to a bluish black color. The crude compound
was ground well and washed with ethanol and water, and then
with acetone in a Soxhlet extractor with 25 mL volume three times
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