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

Abstract

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 -bisdodecyloxy)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. 1 H-13 C heteronuclear dipolar correlation MAS NMR experiments provided the 1 H resonance assignment of the chlorin rings that allowed accurate probing of ring currents related to the stacking of macrocycles. DFT ring-current shift calculations revealed that both chlorins selfassemble in antiparallel -stacks in planar layers in the solid-state. Concomitantly, X-ray powder diffraction measurements for chlorin 2 at 80°C revealed a 3D lattice for the mesoscale packing that matches molecular mechanics optimized aggregate models. For chlorin 2 the stacks alternate with a periodicity of 0.68 nm and a 3D unit cell with an approximate volume of 6.28 nm 3 containing 4 molecules, which is consistent with space group P2 1221. artificial antenna ͉ density functional theory ͉ microcrystalline structure ͉ solid state NMR ͉ X-ray diffraction

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

“…[36] The self-assembly process was primarily driven by a combination of p-p stacking and coordination of central zinc ion with 3 1 -methoxy functionality of a neighboring molecule, and the contributions of various bonding and non-bonding interactions involved were investigated in order to elucidate the precise solid-state pigment organization. [36] On the other hand, ZnChl 1 molecules functionalized with wider and more bulky second-generation dendron (3,4-3,4,5)12G2-CH 2 OH, as in the present case, self-assemble into columnar LC phases that are self-organized into 2D oblique unit cell lattice. Obviously, here the dendron shape primarily controls the self-assembly of 1 by nanophase segregation of chlorin cores and alkyl side chains, promoting columnar arrangement.…”

A multinuclear solid-state magnetic resonance and GIPAW DFT study of anhydrous calcium chloride and its hydrates

“…[7][8][9][10][11][12][13][14][15][16][17] There is an increasing interest in "NMR crystallography", which pertains to obtaining molecular-level and crystal structure information for solid materials using SSNMR data. 18 Although there have been a number of exciting recent advances in this area of research, 6,[19][20][21][22][23][24][25] one cannot currently convert SSNMR data into a unique solid-state structure in a completely generalized manner. With a small amount of a priori knowledge, however, NMR crystallography methods have been applied to solve and refine the structures related to certain classes of materials, such as zeolites, [26][27][28] which are sometimes subject to crystal twinning and typically do not possess enough long-range order to produce crystals that would be considered suitable for X-ray diffraction (XRD) studies.…”

Mixtures of achiral amphiphilic cyanine dyes form helical tubular J-aggregates

“…Supramolecular assemblies of dye molecules have attracted ongoing attention in the past years [1] due to their unique photophysical properties, which make them interesting for technical applications as organic optoelectronic materials [2,3], models for light-harvesting photosynthetic antenna complexes [4][5][6][7][8], structure-sensitive probes in bioanalytics [9][10][11][12], and functional nanomaterials [13][14][15]. Among a variety of organic dyes those being able to form supramolecular aggregates cyanine dyes are of particular interest.…”