Synthesis and Characterization of Metal(II) Phthalocyanine Containing N,N-dimethyl Phenyl Moieties

Synthesized of novel metal (II)-tetra-4-(N,N-dimethyl phenyl) methan-imine phthalocyanines (MTDMPhImPc) [M=Co, Ni, Cu, Zn] by an effective and suitable method. The tetra-nitrophthalocyanines converted into aminophthalocyanines by reduction. Than amino phthalocyanines derivatives bearing tetra-4-(N,N-dimethyl phenyl) to form tetra substituted 4-(N,N-dimethyl phenyl) methane-imine phthalocyanines complexes. These derivatives compounds were characterized by FTIR, elemental analysis, magnetic and powder XRD properties to check the purity and structural integrity. Magnetic measurements on copper and cobalt substituted phthalocyanine complexes in the range of magnetic strength 2.21 to 4.02 kG that a variation of field strength with magnetic moments due to the presence of an intermolecular cooperative effect.


INTRODUCTION
Phthalocyanines are heteroaromatic macrocyclic compounds. It is accidental investigated in 1928, the blue and green colour pigments 1 . Phthaloyanines are more versatility and highly stable complexes due to more than seventy (70) transitional non-metallic and metallic ions substituted in the ring cavity 2 . Phthalocyanines applications such as dyes and pigments 3 , in photovoltaic cells [4][5] , photodynamic therapy 6 , semiconductor materials 7 , as liquid crystals [8][9] , LED 10 , optical storage devices 11 , moletronics 12 , non-linear optical 13 , gas sensors 14 , and for electrochromic displays 15 . The reductionoxidation properties of pthalocyanines are use as industrial applications like dyes and pigments 16 . To modify these macrocyclic compounds have been performed advanced materials for numerous properties and applications.
Phthalocyanines are partially soluble in organic solvents like CCl 4 , acetone or in H 2 O. These insolubility due to peripheral substitution with long alkyl, alkylthio chain, alkoxy, and bulky groups lead to macrocyclic products. Phthalocyanines are soluble in a polar solvent.
In this work, we attempt has been made to synthesize and characterization of a non-peripherally metal(II) phthalocyanine presence of tetra substituents of (N,N-dimethyl phenyl) methan-imine molecule. The amino pthalocyaines complexes react with substituted aldehydes compounds to form imine group. Even though, literature papers revealed the reports on the synthesis and characterization of substituted metal(II) tetra-amino phthalocyanines, no documentary pieces of evidence were available on the newly synthesis and characterization of substituted metal-tetra-4-(N,N-dimethyl phenyl) methan-imine phthalocyanine pigments.
This paper concerns suitable synthetic route available in the literature and modified the procedure the synthesis of metal (II)-tetra-4-(N,Ndimethyl phenyl) methan-imine phthalocyanines in Scheme 1.

MATERIALS AND METHODS
The carbon, hydrogen and nitrogen analysis carried out by the Sophisticated Test and Instrumentation Centre at Cochin University, Kochi, India.The FTIR spectra were recorded on a Nicolet MX-FTIR spectrometer using KBr pellets. Magnetic susceptibility studies by using a Gouy balance and at room temperature (301 o K). Diamagnetic corrections is calculate were used Pascal's constants [18][19] . A calibrant used as a mercury tetra thiocyanato cobalt(II) complex and doubly distilled H 2 O was used in the experiments. Electronic spectra on a UV-Vis Shimadzu 3600 UV-spectrophotometers. Rigaku Miniflex 600 XRD diffractometer was used to measure the diffraction pattern. Thermogravimetric and DTA analysis is carried out by using Perkin-Elmer Thermal analyzer at the rate of 10 0 C/min in air and nitrogen atmosphere. EXPERIMENTAL 4-nitrophthalic acid was prepared as per literature 19 and other solvents and reagents used were analytical grade. The substituted metal(II) tetra-nitro phthalocynanines and metal(II) tetraaminophthalocyanines were prepared by the reported procedure 19 . These complexes converted into imino substituted complexes by condensation reaction 20 . Finally we prepared metal (II)-4-(N,Ndimethyl phenyl) methan-imine phthalocyanines complexes and synthesized compound analytical data were summarized in the table.

RESULTS AND DISCUSSION
All the substituted metal(II) phthalocyanines are bluish color. The metal phthalocyanine complexes are soluble in concentrated sulfuric acid and sparingly soluble in dimethyl sulfoxide, and Dimethylformamide and pyridine. The solubility increasing order like sulfuric acid> dimethyl sulfoxide> Dimethylformamide> pyridine. The elementary analysis C, H, and N result summarized in Table 1 and calculated values with consistent by the suggested structure( Figure 1).

Electronic spectra (UV-Visible)
The metal(II)-tetra-4-(N,N-dimethyl phenyl) methan-imine phthalocyanine complex (M-TDMPhImPc) were performed concentration range 1-1.5 X 10 -4 M in dimethyl sulfoxide and the data are presented in Table 2. The peaks were shown in the range of 774-784 for all the complexes due to a 2u e g and a 2u e g transition 20 . The Q-band M-TDMPhImPc's was found compared to higher corresponding parent substituted metal(II) phthalocyanines. The lower energy redshift band is due to extension in the p-p* transition electron of peripheral substitution of aromatic component imino group. CoTDMPhImPc, CuTDMPhImPc, NiTDMPhImPc and ZnTDMPhImPc absorption peak were shown in the range of 686-691nm which indicate for attributed to the phthalocyanine complexes 21 . B-band and L-band was observed in the range of 242-249nm and 206-217nm for all the complexes. Table 2: UV-Visible, Infra-red and X-ray diffraction spectral data of metal (II)-tetra-4-(N,N-dimethyl phenyl) methan-imine phthalocyanine complexes

Infra-red
The Infra-red spectral data of the metal (II)-tetra-4-(N,N-dimethyl phenyl) methanimine phthalocyanines are presented in Table 2 (Fig. 2). A peak is assigned in the range of 3422-3442 cm -1 in all the complexes due to H-bonding between the hydrogen atom of moisture observed on the KBr pellets and the nitrogen atom of the phthalocyanine skeleton 22 . A sharp is observed in the range of 1624-1633 cm -1 are assigned to C=N bond of the imine group. The peaks in the range of 1367-1386 cm -1 are attributed to C-N bond aromatic stretching 18 . A week peak at 2359-2367 cm -1 are assigned to C-H stretching vibration due to phthalocyanine moiety. All the peaks at 1040-1121 and 745-776 cm -1 can be attributed to the various characteristic phthalocyanine ring stretching skeletons 22 .

Magnetic Susceptibility Measurement
The synthesized M-TDMPhImPc's complexes are measure the magnetic susceptibility were solid state and summarized the results in Table 1. The measurement of applied magnetic field in the range of 2.21 to 4.02 kG and independent determination by average of three values.

Fig. 2. Infrared absorption spectra of (1) CuTDMPHImPc (2) CoTDMPhlmPc (3) NiTDMPhlmPc (4) ZnTDMPhlmPc
While copper and CoTDMPhImPc are paramagnetic behavior and NiTDMPhImPc, ZnTDMPhImPc complexes are diamagnetic nature. The magnetic moments of CuTDMPhImPc and CoTDMPhImPc are higher values than the spinspin only value corresponding to the one unpaired electron 1.73BM, due to the blending of higher energy state (b 2g ) 2 , (e g ) 3 , (a 1g ) 2 orbital with ground state (b 2g ) 2 , (e g ) 4 , (a 1g ) 1 orbitals degenerate states and inter-molecular cooperative effect 23 . As per the literature the magnetic field is higher than the higher magnetic moment values at lower field strength due to magnetic anisotropy of phthalocyanine coupled with intermolecular magnetic interaction [17][18][19][20] .

Powder X-ray Diffraction
The powder XRD pattern of MTDMPhImPc's are taken in the range of 2θ angle 06-70 o and it was observed that all the peaks are identical data is reported in the Table 2. In the spectra one of the sharp peak is observed maximum intensity with lower angle. The following values of interplanar spacing with angle. Co-TDMPhImPc 3.54, 27.87 Å; Cu-TDMPhImPc 2.78, 45.62 Å; Ni-TDMPhImPc 3.64, 27.92 Å and Zn-TDMPhImPc 3.55, 27.91 Å, It is clearly indicating these complexes are crystalline nature. A similar pattern is observed in un-substituted parent phthalocyanine complexes. The broadening of the peaks in the MTDMPhImPc's due to the attributed of the substituents group and play an important role in stacking the substituted metal (II) phthalocyanine complexes 24 .

Thermogravimatric studies
Thermogravimetric analytical data of metal(II)-tetra-4-(N,N-dimethyl phenyl) methanimine phthalocyanine pigment reported in Table 3 and 4. In these complexes the decomposition take place in 2 steps. Initially weight loss of complexes 2-3% due to moisture.  The values I and II stage represent the degradation in nitrogen atmosphere. 1 st step of degradation the temperature ranges from 240-350 o C, in air, the loss of all the four substituted imino groups. In second step the temperature ranges 351-620 o C maximum weight loss is identified in all the phthalocyanines complexes due to the oxidative degradation in the phthalocyanine moiety. Destruction of phthalocyanine complexes only in the second step. Finally, the remaining residue corresponds to metal oxide 23 .
Plot of graph ln(1/y) v/s 1/T. The activation energies (Eo), for the loss of periphery imino substituent groups in all the complexes lies in the range of 0.69-5.86 kJ/ (mol) due to the periphery substituents groups are removed, and the disrupt of the phthalocyanines complex ring. It is exothermic reaction the negative entropies and the degradations are completed. The changes in entropies ∆S varies from -158.56 to -174.86 kJ due to this result it is indicated that all functional groups are associated with negative entropies. The enthalpy, entropy and free energy have been calculated by using standard equations and results are summarized in Table 4.