ARTICLE IN PRESS
B.N. Achar, K.S. Lokesh / Journal of Solid State Chemistry 177 (2004) 1987–1993
1988
2.2. a-Copper phthalocyanine
contacts were checked to verify the ohmic connection
and resistance measurements were done from 25ꢀC to
200ꢀC using Milli Ohm Meter digital, Dot 402 and
Insulation Resistance Tester Dot 425.
Pure 1.0 g copper phthalocyanine was dissolved in
50 mL concentrated sulfuric acid and stirred well. It was
then poured into 250 mL water slowly drop by drop.
The precipitate was filtered and washed with water till
the filtrate was acid free. Finally washed with acetone
and dried over phosphorus pentoxide [1].
3. Results and discussions
3.1. IR spectral study
2.3. b-Copper phthalocyanine
IR spectra recorded in the fingerprint region using the
Nujol-mull technique are presented in Fig. 1. Absorp-
tion peaks observed around 1456, 1377 and 730 cmꢁ1
are due to Nujol. The relevant absorption data along
with the possible vibrational transitions are presented in
Table 1. The peaks around 1121–1123, 1090–1092,
1067–1070, 947–949, 872–885 and 754 cmꢁ1 are due to
phthalocyanine skeletal vibrations [21]. All the poly-
morphic forms of copper phthalocyanine showed
common absorption peaks at 1420–23, 1335, 1286–88,
1202–10, 1165–67, 1001–05, 901, 799–802 and 770–
773 cmꢁ1. a; g and e polymorphic forms of copper
phthalocyanine showed absorption peaks around
1190 cmꢁ1 which is absent in b-form. Similarly, all the
forms showed absorption peaks around 957 and
781 cmꢁ1 except the a-form. But this form showed a
peak at 941 cmꢁ1. b- and g-forms showed absorption
peaks around 1178 cmꢁ1 which is not shown by the
other two forms. Two peaks around 1100 and 980 cmꢁ1
are observed only in the case of b- and e-forms.
Absorption peak at 864 cmꢁ1 is observed by a- and
g-forms only. Additional peaks at 743 and 710 cmꢁ1 are
observed by the g-form of copper phthalocyanine. Thus,
the experimental data in IR absorption peaks show
sufficient evidence for the existence of the four a-, b-,
g- and e-polymorphs of copper phthalocyanine. The
presently observed data does not agree with the earlier
conclusion of having the same structure for the a and g
phases [15].
A 1.0 g of a-copper phthalocyanine was added to
130 mL o-xylene. It was heated on a water bath for 1 h at
a temperature of 60ꢀC. It was filtered, washed with
acetone and dried over phosphorus pentoxide [1].
2.4. g-Copper phthalocyanine
A 1.0 g of a-copper phthalocyanine was heated at
60ꢀC for 2 h in 98% sulfuric acid diluted with 22.7 g
tetrahydrofuran. The reaction mixture was poured into
water. The precipitate was filtered, washed with water
until the filtrate was neutral and then dried over
phosphorus pentoxide [16].
2.5. e-Copper phthalocyanine
A mixture of 1.75 g urea, 0.015 g sulfuric acid (92%),
2.0 g pure copper phthalocyanine, 7.5 g sodium chloride,
and 0.5 g water was heated at 50–60ꢀC for 18 h. Then
85 mL of water was added, boiled for 1 h, filtered,
washed several times with water and dried at 60ꢀC [14].
Carbon, hydrogen and nitrogen analysis were done by
the Regional Sophisticated Center, Lucknow. IR spectra
were recorded using Shimadzu 8201 PC FT-IR spectro-
photometer by Nujol-mull technique. Magnetic sus-
ceptibility measurements were done using a Gouy
magnetic balance consisting of the type NP-53 electro-
meter with DC power supply type MP-1053 and a Keroy
semimicro balance supplied by Universal Scientific,
Bombay, India. Pure HgCo(SCN)4 was synthesized
and used as a calibration standard [18]. The ESR
spectra were recorded using a Varian E-109, X-band
spectrometer. DPPH was used as a reference standard
for g-factor measurements. The spectra were recorded in
solid state at ambient temperature. A JEOL-JDX-8P
X-ray diffractometer was used to study powder X-ray
diffraction of the samples. Powdered copper phthalo-
cyanine complexes were compressed into pellets of
1.3 cm and thickness ranging from 0.15 to 0.25 cm under
pressure of 500 kg/cm2. The Carver laboratory Press
Model—diaton capacity was been used for the purpose.
Conducting silver paint (ELTECKS preparation No.
1228-C) was coated on both flat surfaces of the pellet
and electrical contacts to the samples were made using
the same silver paint to the electrodes. The electrical
3.2. Magnetic susceptibility measurements
Magnetic susceptibility properties of a-, b-, g- and e-
copper phthalocyanine polymorphs have been studied in
solid state at ambient temperature and varying magnetic
field strengths ranging from 1.02 to 3.58 kG. Magnetic
moment values are calculated using the corrected
susceptibility data. The experimental data are in
agreement with the paramagnetic nature of the com-
plexes. The nature of variation of the magnetic moment
values with field strength for all the four polymorphs are
presented in Fig. 2 and the data are summarized in
Table 2. The variations of magnetic susceptibility values
with respect to the magnetic field strengths for a; b and e
are found to be qualitatively similar except for g-form.
Higher or lower values of meff indicate the contribution