Thermal and optical behaviour of octa-alkoxy substituted phthalocyaninatovanadyl complexes

Abstract

This paper deals with the synthesis of vanadyl phthalocyanines substituted with eight alkoxy chains in the peripheral (2,3, 9, 10,16, 17, 23, 24 ) positions. The alkoxy chain length was varied, and octa-octyloxy (C8H17O), octa-dodecyloxy (C12H25O) and octa-hexadecyloxy (C16H33O) substituted vanadyl phthalocyanine complexes were prepared. Studies by polarizing optical microscopy and small angle X-ray di V raction (XRD) revealed that all the complexes are liquid crystalline and that these metallomesogens exhibit a columnar phase. The symmetry of the 2D lattice is rectangular, with a c 2 mm space group, as determined by the indexation of the XRD re ections; hence a rectangular columnar phase (Colr ) was assigned. A double periodicity, although weak, along the axis of the columns was found, which indicates some degree of pairing or dimerization. A tentative explanation based on an antiferroelectric stacking is given. Transition enthalpies were determined by di V erential scanning calorimetry. The compounds start to decompose above 250 ß C before reaching the clearing temperatures. A signi cant bathochromic shift of the Q-band in the UV/Vis spectra of the vanadyl complexes compared with the metal-free ligands and other metallophthalocyanines (M = Co II , Ni II , Cu II , ZnII ) was also observed.

Electrochemical characterization of phthalocyanine derivatives carrying a bulky triester unit on each benzo group

“…Phthalocyanines are an interesting class of compounds with increasingly varied industrial applications including photosensitization, linear optics, liquid crystal, gas sensor, catalysis, photovoltaic cell and electrochromic display [1][2][3][4][5][6][7][8][9][10]. The functions of metalophthalocyanine derivatives are almost all based on their electron transfer reactions because of the p electron conjugated ring system.…”

Liquid-crystalline phthalocyanine-based nanostructures

“…As was shown in [45,49], upon the substitution with aliphatic chains involving 16 or 18 carbon atoms, melt ing points of phthalocyanines insubstantially increase. In a number of cases, the symmetry of the system decreases due to the increase in the aliphatic domain of phthalocyanine molecules, which results in polymeso morphism, and the less structured mesophase occurs at the lower temperatures.…”

Lamellar columnar mesomorphism in a series of oxovanadium(IV) complexes derived from N, N/-di-(4-n-alkoxysalicylidene)diaminobenzene

“…Such polar order is quite significant in the context of novel ferroelectric/piezoelectric and NLO materials [12]. Despite the inherent difficulties in synthesizing mesogenic vanadyl(IV) complexes, a number of vanadyl(IV) liquid crystalline complexes have been documented [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26][27][28][29][30]. Rich but complex mesomorphism exhibited by the salicylaldimines and their metal complexes including vanadium has attracted considerable interests.…”

“…Rich but complex mesomorphism exhibited by the salicylaldimines and their metal complexes including vanadium has attracted considerable interests. The Schiff base complexes of vanadium(IV) that possess a calamitic (rod-like) mesogenic group to which terminal flexible alkyl or alkoxy chains are attached, results in mesogens which either exhibit nematic or smectic phases, have been rather extensively studied [20][21][22][23][24][25][26][27][28][29][30]. However, by coordinating non-discoid ligands, a molecular shape with a reduced length-to-breadth ratio is formed, mimicking disk-like metallomesogens [31].…”

“…Noteworthy here is to mention that most vanadyl-mesogens show either rectangular or hexagonal mesomorphism [12][13][14]20,23,27]. DSC thermograms (Fig.…”