Tetraoctylthio- and tetraoctyloxy-substituted lead phthalocyanines: Synthesis, characterization, liquid-crystalline prop
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Tamara V. Basova Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090, Russia
Vitaly G. Kiselev Institute of Chemical Kinetics and Combustion SB RAS, Novosibirsk 630090, Russia; and Novosibirsk State University, Novosibirsk 630090, Russia
Sergei A. Gromilov and Irina V. Jushina Nikolaev Institute of Inorganic Chemistry SB RAS, Novosibirsk 630090, Russia
Mahmut Durmuşa) and Ayşe G. Gürek Department of Chemistry, Gebze Institute of Technology, Gebze 41400, Kocaeli, Turkey
Vefa Ahsen Department of Chemistry, Gebze Institute of Technology, Gebze 41400, Kocaeli, Turkey; and Materials Institute, TUBITAK-Marmara Research Center, 41470 Gebze, Kocaeli, Turkey (Received 9 June 2011; accepted 19 September 2011)
Peripherally and nonperipherally tetrakisoctylthio- and tetrakisoctyloxy-substituted lead(II) phthalocyanines (PbPcs) were synthesized and characterized using elemental analysis, nuclear magnetic resonance, ultra violet–visible (UV-Vis), infrared (IR), and mass spectroscopies. The mesogenic properties of PbPcs were studied by differential scanning calorimetry, polarized optical microscopy, and x-ray diffraction. The effects of the substitution position and nature of linkage heteroatom on the liquid-crystalline properties and the orientation of the molecules were also studied. Visible absorption spectroscopy yielded an evidence of a thermally induced molecular reorganization in the films. Reflection–absorption IR spectroscopy was used to study the preferential orientation of molecules relative to the substrate surface. The intense bands in the IR spectra of the PbPcs were assigned with the aid of quantum chemical (density functional theory) computations.
I. INTRODUCTION
Self-assembling of discotic molecules into columnar phases offers a unique opportunity of developing potential one-dimensional charge carrier systems. Among the huge variety of mesogenic species, liquid-crystalline (LC) phthalocyanines (Pcs) are of significant interest as organic semiconductors for electronic devices,1–6 mainly due to their high thermal and chemical stability. Particular attention has been already paid to lead(II) phthalocyanines (PbPcs) because of their promising structural, electrical, and optical properties.7–13 It is well known that the substitution at the peripheral and nonperipheral positions of Pc ring can significantly alter the structure and optical properties of Pc species.14–20 For example, alkoxy-substituted PbPc complexes were used to obtain the optical limiting materials a)
Address all correspondence to this author. e-mail: [email protected] DOI: 10.1557/jmr.2011.350 2962
J. Mater. Res., Vol. 26, No. 23, Dec 14, 2011
http://journals.cambridge.org
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with broad protective wavelength and high optical transmission as well as quick response.21 It is well known that the properties of LC Pcs depend on the type and position of substituents in macrocycle. Despite many examples of PbPcs described in literature such investigations were not carried out for PbPcs. Moreover, although many meso
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