Liquid crystalline porphyrins

Nanoscale discotic liquid crystalline porphyrins, (I), were prepared by Li et al. 

The recent description of the construction of a solid state photocell [145] based on order attained via a columnar mesophase of a liquid crystalline porphyrin [146] represents one application of photoinduced electron transfer within organized media which may prove to be fruitful in the future in the burgeoning area of molecular electronics. 

Warman JM, Kroeze JE, Schouten PG, van de Craats AM. (2003) Charge mobility in discotic liquid crystalline porphyrins and phthalocyanines measiared by PR-TRMC. J Porphyrins and Phthalocyanines 7 341-349. 

L. Li, S. Kang, J. Harden, Q. Sun, X. Zhou, L. Dai, A. Jakli, S. Kumar, Q. Li, Nature inspired light-harvesting liquid crystalline porphyrins for organic photovoltaics. Liq. Cryst. 

Novel nanoscale discotic liquid crystalline porphyrins 14 with partial alkyl chain perfluorination has been designed and synthesized in our group which exhibits exceptionally enhanced tendency to spontaneously self-assemble into homeotropically ordered nanostructures [107]. The defect-free homeotropically aligned fluorinated porphyrin thin films were fabricated and characterized. In the films thinner than 10 pm in glass cells, it shows strong tendency towards homeotropic... 

Q. Sun, L. Dai, X. Xiaoli, L. Li, Q. Li, Bilayer- and bulk-heterojunction solar cells using liquid crystalline porphyrins as donors by solution processing. Appl. Phys. Lett. 91, 253505... 

Liquid crystalline porphyrins carrying ester substituents of various chain lengths (see Fig. 19) behave differently [148g]. Some of these compounds show two liquid crystalline phases before they melt yielding isotropic liquids with low viscosity. 

Figure 11-12. Crossed polarizing micrographic textures of spontaneous homeotropically aligned columnar phase of liquid crystalline porphyrin P8 at room temperature (A and B with different cooling rate. The dark areas are homeotropic alignment where the planes of the disk-shaped molecules are parallel to the substtates. Bright domains represent areas where the molecular planes are tilted with respect to the substtates.)...

Most of the devices described up to now are based on materials that tend to crystallize [phthalocyanines, porphyrins and perylenetetracarboxydiimids, (59)] [276, 277], or form liquid crystalline phases [278, 279]. With respect to amorphous glasses, light sensitive donor-acceptor type molecules, for example, the p-type triarylamines tris [4-methylphenyl(4-nitrophenyl)ammo]triphenylamine and tris[5-(dimesitylboryl)thiophen-2-yl]triphenylamine have been combined with an n-type material in a double-layer heterostructure [280]. The cells respond to visible light from 400 to 800 nm with overall efficiencies of 0.1%. 

In the last few years disc-like molecules have been shown to form liquid crystals (Chandrasekhar, 1994). Typical of them are hexasubstituted esters of benzene (I) and certain porphyrin esters (II) (see below). In the liquid crystalline state, the disc-like molecules are stacked aperiodically in columns (liquid-like), the different columns packing in a two-dimensional array (crystal-like). The phases have translational periodicity in two dimensions but liquid-like disorder in the third. In addition to the columnar phase(D), the disc-like molecules also exhibit a nematic phase (Nj,). A transition between D and phases has been reported. 

Third-order NLO properties have been described for liquid-crystalline phthalocyanine and porphyrin complexes. The values for the meso-genic cobalt(II), nickel(II), copper(II), zinc(ll) and vanadyl complexes of 5,10,15,20-tetrakis(4-w-pentadecylphenyl)porphyrin have been measured in benzene solution by the technique of degenerate four-wave mixing (DFWM) at 532 nm. The values varied between 1.5 and... 

Fig. 6 (a) Host and guest molecules used in the glycoluril-based materials, (b) Computer-modeled representation of the liquid-crystalline host-guest complex between porphyrin %% and four molecules of Host 21. (c) Modeled structure of the arrangement of dimers in the lamellar plastic crystal formed by 23, (d) Modeled structures of the 1 1 host-guest complexes between 23 and MDB (top) and between 23 and DBA (bottom). (View this art in color at www.dekker.com.)... 

The orientation of n-nonoxyethyl octa-substituted liquid-crystalline material was explored by X-ray diffraction. The molecules were found to structurally order in columns such that the macrocyclic planes tilt at an angle of 46° to the columns (Figure 2) The intricacy of the structure was further elaborated for the n-decoxyl derivative. The interfacial porphyrin-porphyrin distance was found to be 3.98 A, and the intercolumn. separation was 23.59 A (Figure 3). This structure has been suggested as a one-dimensional molecular wire motif for electronic conduction. ... 

Due to the disc-like geometry of the porphyrin macrocycle, discotic mesophases have generally been the most common for porphyrin liquid-crystalline materials. The first porphyrin liquid crystals featuring rod-like calamitic mesophases were described by Bruce and coworkers using substituted 5,15-di(phenyl) zinc porphyrin complexes as the basic molecular building block.The first materials... 

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