Columnar mesophases based on zinc chlorophyll derivatives functionalized with peripheral dendron wedges.

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.

Zinc chlorins for artificial light-harvesting self-assemble into antiparallel stacks forming a microcrystalline solid-state material.

We introduce a concept to solve the structure of a microcrystalline material in the solid-state at natural abundance without access to distance constraints, using magic angle spinning (MAS) NMR spectroscopy in conjunction with X-ray powder diffraction and DFT calculations. The method is applied to a novel class of materials that form (semi)conductive 1D wires for supramolecular electronics and artificial light-harvesting. The zinc chlorins 3-devinyl-3(1)-hydroxymethyl-13(2)-demethoxycarbonylpheophorbide a (3',5'-bis-dodecyloxy)benzyl ester zinc complex 1 and 3-devinyl-3(1)-methoxymethyl-13(2)-demethoxycarbonylpheophorbide a (3',5'-bis-dodecyloxy)benzyl ester zinc complex 2, self-assemble into extended excitonically coupled chromophore stacks.

Structure-property relationships for self-assembled zinc chlorin light-harvesting dye aggregates.

A series of zinc 3(1)-hydroxymethyl chlorins 10 a-e and zinc 3(1)-hydroxyethyl chlorins 17 with varied structural features were synthesized by modifying naturally occurring chlorophyll a. Solvent-, temperature-, and concentration-dependent UV/Vis and CD spectroscopic methods as well as microscopic investigations were performed to explore the importance of particular functional groups and steric effects on the self-assembly behavior of these zinc chlorins. Semisynthetic zinc chlorins 10 a-e possess the three functional units relevant for self-assembly found in their natural bacteriochlorophyll (BChl) counterparts, namely, the 3(1)-OH group, a central metal ion, and the 13(1) C==O moiety along the Qy axis, and they contain various 17(2)-substituents.

Self-assembled single- and double-stack pi-aggregates of chlorophyll derivatives on highly ordered pyrolytic graphite.

The highly efficient, light-harvesting antennae systems present in chlorosomes of green phototrophic bacteria, such as Chloroflexus aurantiacus, serve as a model for the design of bioinspired nanostructured materials. A semisynthetic zinc chlorin, derived from natural chlorophyll a, is used as a building block that self-assembles into excitonically coupled chromophore stacks. Temperature-dependent UV/Vis and circular dichroism spectroscopic measurements show the reversible formation of soluble chiral aggregates of this new zinc chlorin dye.