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Columnar Mesophases Based on Zinc Chlorophyll Derivatives Functionalized with Peripheral Dendron Wedges
Author(s) -
Sengupta Sanchita,
Uemura Shinobu,
Patwardhan Sameer,
Huber Valerie,
Grozema Ferdinand C.,
Siebbeles Laurens D. A.,
Baumeister Ute,
Würthner Frank
Publication year - 2011
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201002659
Subject(s) - materials science , columnar phase , crystallography , scanning electron microscope , differential scanning calorimetry , scanning tunneling microscope , microscopy , zinc , discotic liquid crystal , molecule , analytical chemistry (journal) , chemistry , liquid crystal , nanotechnology , organic chemistry , optics , liquid crystalline , optoelectronics , physics , metallurgy , composite material , thermodynamics
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.