Mesogenic Ni(II) complexes of C_ssymmetry forming Col_hphase by dipole-dipole interaction

Influence of mesogenic core polarity and position of chains attachment on columnar phase stability

“…In a few compounds, the aroyl moiety is replaced with more extended coumaranone or chromanone moiety that includes the phenyl ring and blocks its free rotation. These oxygen analogues of indanone and tetralone structures [31], similar as previously, give very stable Col h phase with broad temperature range and extremely high clearing points. The permanent dipole moment created in the mesogenic core was confirmed in quantum mechanical calculations.…”

“…This feature is also visible in a cyclic imidazolidine derivatives: 1,3-dimethyl-2-imidazolidinone and 1,3-dimethyl-2-imidazolidinethione. [33] The latest compound with thiocarbonyl group has dipole moment equal to 5.20 D, whereas the previous one having carbonyl group is 4.08 D. The strong dipole moment in the synthesised molecules gives stabilisation of Col h phase through dipole-dipole interaction along LC columns [29,31] ( Figure 2) and the antiparallel molecular arrangement Liquid Crystals 3 results in symmetrical (circular) columnar shape. However, there is no correlation among dipole directions in adjacent columns.…”

“…Some of their symmetric analogues constructed from two enaminoketone branches do not exhibit LC phases and have low clearing points. [18,31] Comparing couples of materials having in barbituric ring oxygen or sulfur atom and at carbonyl phenyl ring the same substituents (i.e. the couples: with two attached chains I-1-II-1, I-3-II-3 with three chains, I-2-II-2 and with chromanone moieties I-2s-II-2s, I-4s-II-4s), it can be concluded that the replacement of oxygen atom with sulfur atom increases the temperature of isotropisation about 10-20°C.…”

“…These reactions were presented in our previous work. [31] The new compounds 2, which contain sulfur atom in barbituric ring, were synthesised from 1,3-dialkyl-2-thiobarbituric acid in exactly the same preparation way. Phenylenediamine and barbituric pyridine derivatives 2 in condensation reaction gave semi-ligands 3 as solid.…”

“…[28][29][30] In this contribution, LC nickel(II) complexes having molecules of low C s symmetry are presented (Scheme 1), and this is an extension of our previous work. [31] The molecules of the described compounds have more or less triangular shape and they form only Col h phase. Their mesogenic cores are constructed from two different chelating rings: enaminoketone ring and enaminoamide moiety coming from barbituric derivatives.…”