Synthesis and phase behaviour of β-octaalkyl porphyrins

Abstract

A homologous series of three octakis-alkyl-substituted porphyrin (OAP) derivatives with alkyl chain lengths of C 8 , C 10 and C 12 has been synthesised. For each compound, both the free-base (i.e. two H-atoms) and the fourfold coordinated zinc complex were investigated, where the latter for each chainlength was found to exhibit liquid crystalline mesophase behaviour. At low temperatures 10 all three metal coordinated compounds formed a solid S phase with a structure based on a square packing of columns with a stacking periodicity of 4.7 Å. At increased temperatures the square packed solid S phases undergo phase transitions to liquid-crystalline columnar phases based on centered rectangular lattices of C2/m symmetry, with the ratio of the lattice parameters, a/b, ranging between 1 and 1.732. The a/b ratio exhibited two discontinuous jumps with increasing 15 temperature prior to melting to the isotropic phase for Zn-OAP-C 8, implying the existence of three columnar phases denoted Col r1 , Col r2 and Col r3 . For the longer chainlength compounds, the number of mesophases formed was reduced, first to two for Zn-OAP-C 10 , then to one for Zn-OAP-C 12 .

Unconventional Approaches to Prepare Triazine-Based Liquid Crystal Dendrimers

“…Compared with traditional disk molecules, dendrimer 1 with a C2-symmetry having a columnar LC phase on cooling, is unusual. To exhibit columnar mesophases, the traditional C2-symmetry molecules may consist of a macrocyclic core [ 56 , 57 ]. Introducing a chiral core to result in helical stacking columns by modulating the intermolecular π–π interaction between molecules is another approach [ 58 ].…”

“…Co simulations for the conformations of dendrimers 1 and 2 showed that the steric eff the peripheral skeleton of 1 is more significant than that of 2 [54], i.e., the dendr formation of 1 is less coplanar due to congestion between the branched mainfram reducing the face-to-face π-π interactions between dendritic molecules and form columnar phase on thermal treatment. Compared with traditional disk molecu drimer 1 with a C2-symmetry having a columnar LC phase on cooling, is unusua hibit columnar mesophases, the traditional C2-symmetry molecules may consist o rocyclic core [56,57]. Introducing a chiral core to result in helical stacking colu modulating the intermolecular π-π interaction between molecules is another a [58].…”

Preferential formation of columnar mesophases via peripheral modification of discotic π-systems with immiscible side chain pairs

“…For discotic LC molecules, the major driving force to enable columnar structures via self-assembly is mostly given by the peripheral modification of disc-shaped cores with long paraffinic chains, [4][5][6][7] where rigid p-systems and flexible side chains are segregated in a nanoscopic scale. Nevertheless, the volume balance between a discotic core and peripheral chains has a remarkable impact on the stable phase structures, 8 leading to the formation of other phases such as micelle cubic, [9][10][11] bicontinuous cubic, [12][13][14] crystalline, 15,16 and amorphous phases. 17,18 Therefore, in order to obtain columnar LC materials, the try-and-error in the synthesis process is required for every discotic p-system such as changing the number and length of chains.…”

Metallomesogens with Luminescent Behaviour: Palladium Complexes Derived from Alkylamide Tetraarylporphyrins

“…[20,21] The most significant LC behaviour was found by peripheral modification of octa-substituted and meso-tetraphenylporphyrinic derivatives. [2,[20][21][22][23][24][25][26][27][28] Additionally,s ome tetrapyrrolic macrocyclesp eripherally substituted have LCs properties and exhibit columnar mesophases. [29,30] Following our research interests in discotic LC and luminescent materials, [31][32][33] and considering the potential of functionalised meso-tetraarylporphyrins in this field, [34] we decided to prepareaseries of easily accessible porphyrins containing four (3a,b)o re ight (3c,d)a liphatic amide chains with different lengths.…”

“…on mesogenic porphyrins, many other scientific groups synthesised new porphyrinic derivatives and investigated their mesomorphic properties . The most significant LC behaviour was found by peripheral modification of octa‐substituted and meso ‐tetraphenylporphyrinic derivatives . Additionally, some tetrapyrrolic macrocycles peripherally substituted have LCs properties and exhibit columnar mesophases …”