Structure and Mesomorphic Behavior of Alkoxy-Substituted Bis(phthalocyaninato)lanthanide(III) Complexes

Abstract

The influence of the lanthanide ion and the chain length on the thermal properties of bis[2,3,9,10,16,17,23,24-octakis(alkoxy)phthalocyaninato]lanthanide(III) complexes, denoted in the following as [(C n H 2n+1 O) 8 Pc] 2 Ln, have been investigated. Two series of complexes were considered: a first series in which the alkoxy chain was kept constant with different lanthanide ions (Ln) Pr, Nd, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu), namely, [(C 12 H 25 O) 8-Pc] 2 Ln, and a second series of bis(phthalocyaninato)erbium(III) doubledeckers , [(C n H 2n+1 O) 8-Pc] 2 Er, with different alkoxy chain lengths (n) 4-18). All these metallomesogens exhibit a hexagonal columnar mesophase (Col h) over wide temperature ranges. It was found that the transition temperatures were not affected to a great extent by the lanthanide ion and that they could be tuned by a proper choice of the alkoxy chain length. The orientational behavior of [(C 12 H 25 O) 8 Pc] 2 Er in contact with a substrate has also been investigated by scanning tunneling microscopy.

Liquid‐Crystalline Ternary Rare‐Earth Complexes

“…In the last decade, there has been considerable activity in the research field of lanthanide-containing liquid crystals (which are also called lanthanidomesogens). [2,[9][10][11] Different types of ligands were used to design new classes of lanthanidomesogens: Schiff bases, [12][13][14][15][16][17][18][19][20][21][22] β-enamino ketones, [23] alkanoates, [24,25] 4-alkoxybenzoates, [26][27][28] phthalocyanines, [29,[29][30][31][32][33] porphyrins, [34,35] imidazo [4,5-f] [1,10]phenanthrolines, [36] β-diketonates, [37] crown ethers, [38][39][40] 2,6-bis-(benzimidazol-2Ј-yl)pyridines, [11,41,42] and polyoxometalatesurfactant complexes. [43] Most examples of lanthanidomesogens are thermotropic liquid crystals, although some examples of lyotropic lanthanidomesogens have also been reported.…”

“…[43][44][45][46] The rationale for the research interest in lanthanidomesogens is that, by incorporation of rare-earth ions in liquid crystals, it is possible to obtain magnetic [13,47,48] or luminescent liquid crystals. [49,50] Although in some classes of lanthanidomesogens (like phthalocyanines [29] and imidazo [4,5-f] [1,10]phenanthrolines [36] ) the size of the lanthanide(III) ion has only limited or no effect on the transition temperatures, in many cases the lanthanide contraction has a very strong influence on the mesophase behavior. This was first illustrated by mesomorphic Schiff base complexes, where the temperature range over which the mesophase exists strongly decreases when going from lanthanum(III) to lutetium(III).…”

Assembly and Manipulation of Rotatable Cerium Porphyrinato Sandwich Complexes on a Surface

“…[11,12] These large double-and triple-decker molecules are generally susceptible to thermal decomposition and often unsuitable for high-temperature vapor deposition, indeed, only a few examples are reported. [13,14] Alternatively, observations are possible at solid/liquid interfaces in an insulating organic solvent [12,15] or under electrochemical control in an electrolyte solution. [16] Herein we report a novel route for the synthesis of bis(porphyrinato)cerium double-decker complexes (Ce-(TPP) 2 , TPP = tetraphenylporphyrin; Figure 1 a, c) directly on a Ag(111) surface under ultra-high-vacuum conditions by exposing a porphyrin precursor layer to an atomic beam of Ce followed by a temperature-programmed reaction and desorption of surplus material.…”

Encoding calamitic mesomorphism in thermotropic lanthanidomesogens

“…3 Two main strategies have been considered for restoring the minimal electronic and structural incompatibilities required for an efficient microsegregation: (1) the Ln III ions are embedded into aromatic polarizable cavities produced by several wrapped ligands, which globally display rodlike or disklike shapes (Fig. S1, ESI{), [3][4][5] or (2) the coordination of Ln III to pro-mesogenic polycatenar ligands possessing curved molecular interfaces and large melting entropies helps to induce thermotropic mesomorphism at 'low' temperature, as observed for [Ln(L1)(NO 3 ) 3 ] (Fig. 1).…”