Synthesis of Triptycene-Based Molecular Rotors for Langmuir–Blodgett Monolayers

Abstract

We describe syntheses of six triptycene-containing molecular rotors with several single-crystal X-ray diffraction analyses. These rod-shaped molecules carrying an axial rotator are designed to interleave on an aqueous surface into Langmuir-Blodgett (LB) monolayers containing a two-dimensional trigonal array of dipoles rotatable about an axis normal to the surface. Monolayer formation was verified with the simplest of the rotor structures. On an aqueous subphase containing divalent cations (Mg(2+), Ca(2+), Zn(2+), Sr(2+), or Cd(2+)), the LB isotherm yielded an area of 53 ± 3 Å(2)/molecule (monolayer of type A), compatible with the anticipated triangular packing of axes normal to the surface. On pure water, the area is 30 ± 3 Å(2)/molecule, and it is proposed that in this monolayer (type B), the molecular axes are tilted by 40-45° to a structure similar to those observed in single crystals of related triptycenes. After transfer to a gold surface, ellipsometry and PM IRRAS yield tilt angles of 29 ± 4° (monolayers of type A) and 38 ± 4° (type B). A full-scale examination of monolayers from all the rotors on a subphase and after transfer is underway and will be reported separately.

From coherent quasi-irreversible quantum dynamics towards the second law of thermodynamics: The model boron rotor B13+

“…3 for the examples of the initial preparations of GM 16 (B 13 + ) and GM 1 (T 2 ), 30 respectively. Apparently, the boron rotor B 13 + (left) tunnels from the initial GM 16 in equivalent clockwise (along -ϕ) and anti-clockwise (along +ϕ) manners sequentially to its "left" (GM 15 ) and "right" (GM 17 ) neighbors, then to the next nearest neighbors (GM 14 and GM 18 ), etc. see Fig.…”

“…[1][2][3] Fundamental developments have discovered fascinating phenomena and enabled a wealth of applications in the gas phase, [4][5][6][7][8] in solution, 4,[9][10][11] in crystals, 4,12 on surfaces, [4][5][6][13][14][15] and in biosystems. 16 Here we use a molecular model rotor to demonstrate the way from molecular quantum dynamics to explicitly time dependent statistical thermodynamics.…”

“…+ with inner triangular wheel rotating in outer pseudo-rotating bearing (schematic). Clockwise and anti-clockwise tunneling from the global minimum GM 16 to the neighbors GM 15 and GM 17 , respectively (left), and then sequentially to GM 14 , GM 13 , GM 12 , GM 11 , etc, and simultaneously also to GM 18 , GM 19 , GM 20 , GM 21 , etc (right). Subsequent tunneling tends to populate all GMs, see Fig.…”

Triptycene‐based fluorescent polymers with pendant alkyl chains: interaction with fullerenes and morphology of thin films

“…Consequently, such polymers (derived from iptycene monomers) have found application in the design of gas separation membranes, organic photovoltaic devices, liquid crystals, . molecular sensors (for explosives derived from nitroaromatics) and molecular machinery . Moreover, polymers with iptycenes in main/side chain are reported to be efficient materials for selective capture/storage of gases and adsorbents of dyes for purification of industrial effulents …”

Structure of a monolayer of molecular rotors on aqueous subphase from grazing-incidence X-ray diffraction

“…The latter condition requires large rotatable dipoles μ spaced a small distance a apart, since T C is expected to be proportional to μ 2 /a 3 . After dealing with surface inclusions, in which molecular rotors were contained on the surface of a host crystal, and detecting ferroelectric interactions but no ferroelectric phase in bulk inclusions (4), we are now also exploring monolayers produced on aqueous surfaces using a Langmuir-Blodgett (LB) trough (5) and molecular rotors designed to assemble into a trigonal lattice (6). The hope is that the rotor axes will be perpendicular to the surface and separated by a small lattice constant (a < 1 nm) and that large monocrystalline domains can be produced.…”