Discotic liquid-crystal behaviour of some multinuclear phthalocyanine derivatives

Abstract

The liquid-crystal properties are reported for a series of multinuclear phthalocyanines containing either two or three macrocyclic ring units. All but one of the compounds, the 'dimer' with the shortest spacer group between the two rings, exhibit discotic columnar mesophase behaviour. On cooling from the isotropic liquid the liquid-crystalline dimers show two distinct mesophases and the trimers one. Phase-transition temperatures are dependent upon the length of the linkages and whether or not copper is inserted into the macrocycle. The materials become very viscous, if not glass-like, when cooled to room temperature but retain the mesophase features defined by X-ray diffraction measurements.

Synthesis and mesomorphism of triphenylene-based dimers with a highly ordered columnar plastic phase

“…16 The smaller scattering angles (about 2q ¼ 5 -15 ) showed two separate peaks of roughly equal intensity and additional peaks of lower intensity, these peaks were identied as the (200), ( 110), (020) and (400) reections of a two dimensional rectangular lattice in which the molecules are tilted with respect to the column axis. 25,26 It was the rst report on a rectangular lattice in a columnar plastic phase, according to the previous denition of the rectangular columnar phase, this new phase could be dened as a rectangular columnar plastic phase. The lattice constants a and b were calculated to be a ¼ 32.…”

Liquid crystalline properties of unsymmetrically substituted phthalocyanines: structural features leading to nematic mesophase materials

“…The series of novel compounds 1-4 was prepared according to the route depicted in Scheme 1. The synthetic scheme has been exploited earlier by us to provide examples of homologues of type C where the six alkyl chains on three of the benzenoid rings are hexyl, octyl or undecyl groups and with various length hydroxyalkyl chain on the fourth benzenoid ring [13][14][15][16]. In the present work, the mixed cyclisation of two phthalonitrile derivatives, a 3-methyl-6-hydroxyalkyl phthalonitrile and 3,6-dipentylphthalonitrile, step iii in Scheme 1, produces the desired phthalocyanine compound along with 1,4,8,11,15,18,22,25-octakis(pentyl)phthalocyanine as the main side-product together with limited amounts of other cross condensation products.…”

“…The UEA group then reported that compounds bearing eight medium length alkyl [6][7][8][9] or alkoxymethyl groups [10,11] at the non-peripheral (1,4,8,11,15,18,22,25-) sites of the macrocycle, as metal-free or M II metallated derivatives, also exhibited columnar mesophase behavior. The same group further established that columnar liquid crystal phases were exhibited by non-uniformly substituted phthalocyanines such as those depicted in Fig 1 [12][13][14][15][16]. Nowadays there is a broad range of liquid crystalline phthalocyanine derivatives available [17] and, for some examples, there is particular interest in their electrical conductivities.…”

Design and synthesis of liquid crystalline phthalocyanines: combinations of substituents that promote the discotic nematic mesophase

“…The synthetic method was developed earlier by us to provide examples of homologues designed for other studies. [22][23][24][25] In the present work, the mixed cyclisation of two phthalonitrile derivatives, i.e. a 3-methyl-6-(hydroxyalkyl) phthalonitrile and a 3,6-dialkylphthalonitrile, step iii in Scheme 1, produced the desired metal-free phthalocyanine compound.…”

“…Simon's Pcs carried eight alkoxymethyl chains at the peripheral (2,3,9,10,16,17,23,24-) sites of the Pc ring. [11][12][13][14] The UEA group then reported new examples bearing eight medium length alkyl [15][16][17][18] or alkoxymethyl groups 19,20 located at the alternative non-peripheral (1, 4,8,11,15,18,22,25-) [21][22][23][24][25] All the liquid crystalline examples referred to above exhibit columnar mesophase behaviour, see Fig 2, and is discussed later. Our recent preliminary study 26 probed how a combination of particular ring substituents on the Pc core of type C metal-free compounds also promotes mesophase formation.…”