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IUPAC Prize for Young Chemists - 2000
Honorable Mention

 

 

Tamara V. Basova receives one of five Honorable Mention awards associated with the IUPAC Prize for Young Chemists, for her Ph.D. thesis work entitled "Physical chemical and Raman spectral investigation of phthalocyanines of copper and aluminum and their thin films"

Current address (at the time of application)

Lavrentiev Pr., 3
RU-630090 Novosibirsk, Russia

Tel.: +7(3832)343957
Fax: +7(3832)344489
E-mail: [email protected]

Academic degrees

  • Ph.D., Institute of Inorganic Chemistry, Siberian Branch of RAS (Physical Chemistry)

Ph.D. Thesis

Title Physical chemical and Raman spectral investigation of phthalocyanines of copper and aluminum and their thin films
Advisers Dr. Boris A. Kolesov and Prof. Igor K. Igumenov
Thesis Committee Prof. F.A. Kuznetsov; Dr. Buyanova L.M.

Essay

The phthalocyanines have been a subject of a vast amount of study, both theoretical and experimental. They have been studied for their possible use as dyes and catalysts. Because of their similarity to chlorophyll and haemoglobin, they have been extensively studied as model compounds in biochemistry. However, the most exciting application of phthalocyanines is that they represent one of the most promising materials for future molecular opto-electronic devices. In spite of advances in metal phthalocyanine chemistry, till present there are no reliable experimental data on thermal properties of phthalocyanines in condensed and gas phase, and on methods to characterise their films.

The present investigation is aimed at the solution of the following scientific problems: first, investigation of thermal properties of free phthalocyanine (a, b-H2Pc) and its complexes with copper (a, b-CuPc) and aluminium (AlClPc, AlFPc, (AlPc)2O); second, the development of scientific foundations for the preparation of oriented films on various substrates; third, the development of a new method for the determination of phthalocyanine films orientation by means of Raman spectroscopy.

The following results were obtained when solving the listed problems.

1. Copper and aluminium phthalocyanines and free phthalocyanine have been synthesised and characterised using elemental analysis, vibrational spectroscopy, X-ray phase analysis. On the basis of the data obtained by means of high-temperature mass spectrometry, differential thermal analysis and thermogravimetry in vacuum, the regimes of purification and separation of phthalocyanines by gradient sublimation in a vacuum have been proposed.

2. The composition of the gas phase above the free phthalocyanine and its complexes with copper and aluminium has been studied by means of high-temperature mass spectrometry. It has been stated that phthalocyanine decomposition does not occur in the gas phase within the temperature range studied (up to 700 oC). The vapour pressure of these phthalocyanines has been determined as a function of temperature by the Knudsen effusion method, in which the rate of effusion of the equilibrium vapour through a small orifice was measured. Thermodynamic parameters of phthalocyanine vaporisation (DHoT , DSoT ) have been obtained using experimental data P=f(T). These investigations for phthalocyanine and aluminium phthalocyanines have been obtained for the first time.

3. On the basis of experimental data obtained, the regimes of phthalocyanine film deposition have been optimised. By means of vacuum organic molecular beam deposition, oriented polycrystalline films of copper phthalocyanine have been obtained. The films thus obtained have been studied by means of Raman spectroscopy and X-ray diffraction. It has been stated that at the substrate temperature within the range 20-160 oC, polycrystalline films are formed, their structure corresponding to the a-modification of copper phthalocyanine, while at the temperature of 180-185 oC, b-modification is observed. 4. In order to develop the technique of the determination of phthalocyanine film orientation the detail analysis of the Raman spectra of CuPc was performed. The normal coordinate analysis for all in-plane gerade modes of copper phthalocyanines (CuPc) has been carried out. We at first have determined the symmetry of modes based on the polarized Raman spectra of the oriented CuPc single crystal and its solution. So far the calculations of phthalocyanine spectra were not confirmed by the data for isotopically substituted compounds. In the present work, the isotopic frequency shifts upon 15N substitution for nitrogen atoms in CuPc have been measured. These experimental data enabled us to confirm the calculation and to discuss some details of normal vibrations of CuPc molecule. It was shown that the bands at frequencies below 200 cm-1 correspond to the crystal modes. The bands at frequencies above 200 cm-1 are assigned to the internal molecular vibrations.

5. In this work, we have suggested the general approach to the analysis of the orientation of phthalocyanine thin films by the method of Raman spectroscopy, using the films of a and b copper phthalocyanine as an example. It has been shown that the orientation of thin films may be determined using the analysis of crystal modes as well as internal molecular vibrations. The determination of the orientation by the analysis of external modes is based on the comparison of b-CuPc single crystal spectra recorded at various polarization of incident light with the spectrum of film. The crystal modes are directly connected with crystal structure determining their number and symmetry. However, given approach does not apply for the analysis of the films of compounds with unknown crystal structure. In this case, the analysis of internal molecular vibrations is more a general and universal method. The principle of the approach based on the analysis of internal molecular vibrations is the following. The information on structural features of any film (oriented, partially oriented, disordered) is contained in the matrix elements of scattering tensors of individual type of vibrations. In order to obtain such information, it will suffice to measure the Iii / Iij ratios ( Iii / Iij is the ratio of average values of Raman intensities in parallel and cross polarization of incident and scattering light) for each vibration types. It was determined that the CuPc films are oriented so that the XY plane of microcrystallites is parallel to the substrate surface, the molecule planes in a-CuPc film forming an angle of about 29o with the normal to the substrate surface. The molecules in b-CuPc film form an angle of about 40o.

6. The investigation of the orientation of the polycrystalline CuPc films deposited on the substrates from quarts, aluminium, copper, silicon, MoS2, NaCl has been carried out using the proposed techniques. It was stated that the films deposited on above mentioned substrates at identical conditions had the same orientation. The results are of theoretical importance as well as of practical use. The results of the measurements of the temperature dependence of phthalocyanine saturated vapour pressure within rather wide temperature range allowed to obtain reliable quantitative information that served as a basis to develop optimal regimes of the deposition of thin phthalocyanine films by OMBD. The application of the technique to determine film orientation proposed in the present work is not limited to the analysis of phthalocyanines. This approach can be used successfully to analyse various molecular films deposited onto any substrates. It may be especially important in determining the orientation of polymers in Langmuir-Blodgett and liquid crystal films, which are extensively studied today.


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