Columnar Mesophases Based on Zinc Chlorophyll Derivatives Functionalized with Peripheral Dendron Wedges

Abstract

A chlorophyll derivative with a central zinc ion, a methoxy functionality at its 3(1)-position, and functionalized with a second-generation dendron (3,4-3,4,5)12G2-CH(2)OH at its 17(2)-position was synthesized starting from natural chlorophyll a (Chl a). This compound exhibits liquid crystalline (LC) behavior and its mesomorphic properties have been characterized by differential scanning calorimetry (DSC), polarisation optical microscopy (POM), powder X-ray diffraction (XRD), and scanning probe microscopy (SPM). A combination of powder XRD, high resolution scanning tunneling microscopy (STM), and atomic force microscopy (AFM) experiments revealed the formation of nano-segregated well-ordered columnar tubular superstructures consisting of about five molecules in the column stratum. These self-assembled columns are further self-organized into a two-dimensional oblique unit cell lattice. Semiconducting behavior of this compound has been studied by pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) method and charge carrier mobility values of ∼10(-2) cm(2) V(-1) s(-1) are observed. Such organized columnar superstructures constructed from semisynthetic zinc chlorins are reminiscent of the tubular organization of the bacteriochlorophyll dyes in the light-harvesting chlorosomal antennae of green sulphur bacteria.

High‐Optical‐Quality Ferroelectric Film Wet‐Processed from a Ferroelectric Columnar Liquid Crystal as Observed by Non‐linear‐Optical Microscopy

“…Therefore, the observed fibrils here may be of molecular columns lying on the substrate plane of the film. Actually, the similar fibril‐like structures have been reported previously in AFM observation in some other columnar LC systems 19, 20. Figure 2b is an AFM image of the same FCLC film taken at RT cooled after poling.…”

Biosupramolecular Nanowires from Chlorophyll Dyes with Exceptional Charge‐Transport Properties

“…estimated an upper limit of 0.002 cm 2 V −1 s −1 for an ideally ordered solid‐state material of these dyes. Microwave‐conductivity experiments on a liquid‐crystalline zinc chlorin derivative performed by our research group showed charge mobilities exactly in this range 17…”

Biosupramolecular Nanowires from Chlorophyll Dyes with Exceptional Charge‐Transport Properties

“…So far, in contrast to the excellent excitontransport characteristics, [2,15] (bacterio-)chlorophyll dyes have not been demonstrated to possess outstanding charge-carriertransport properties. [17] In an identical experiment, the intrinsic charge-carrier mobility of zinc chlorin 1 in the solid state was characterized by the pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) technique in the temperature range from À25 to 100 8C ( Figure S7 and Table S1). Microwaveconductivity experiments on a liquid-crystalline zinc chlorin derivative performed by our research group showed charge mobilities exactly in this range.…”

“…Microwaveconductivity experiments on a liquid-crystalline zinc chlorin derivative performed by our research group showed charge mobilities exactly in this range. [17] In an identical experiment, the intrinsic charge-carrier mobility of zinc chlorin 1 in the solid state was characterized by the pulse-radiolysis time-resolved microwave conductivity (PR-TRMC) technique in the temperature range from À25 to 100 8C ( Figure S7 and Table S1). With this technique, a short pulse of high-energy electrons (10-50 ns, 3 MeV) generates a uniform concentration of charge carriers in the sample that is detected by a continuous source of microwaves.…”