Ganapathy Swapna, Sengupta Sanchita, Wawrzyniak Piotr K, Huber Valerie, Buda Francesco, Baumeister Ute, Würthner Frank, de Groot Huub J M
Leiden Institute of Chemistry, Einsteinweg 55, 2333CC Leiden, The Netherlands.
Proc Natl Acad Sci U S A. 2009 Jul 14;106(28):11472-7. doi: 10.1073/pnas.0811872106. Epub 2009 Jul 8.
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. (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 self-assemble in antiparallel pi-stacks in planar layers in the solid-state. Concomitantly, X-ray powder diffraction measurements for chlorin 2 at 80 degrees 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(1)22(1).
我们引入了一个概念，即利用魔角旋转（MAS）核磁共振光谱结合X射线粉末衍射和密度泛函理论（DFT）计算，在无需距离限制的情况下，以天然丰度解析固态微晶材料的结构。该方法应用于一类新型材料，这类材料可形成用于超分子电子学和人工光捕获的（半）导电一维导线。二氢卟吩锌3 - 脱乙烯基 - 3(1)-羟甲基 - 13(2)-去甲氧基羰基脱镁叶绿酸a（3',5'-双十二烷氧基）苄酯配合物1和二氢卟吩锌3 - 脱乙烯基 - 3(1)-甲氧基甲基 - 13(2)-去甲氧基羰基脱镁叶绿酸a（3',5'-双十二烷氧基）苄酯配合物2自组装成扩展的激子耦合发色团堆叠。质子 - 碳（¹H - ¹³C）异核偶极相关MAS核磁共振实验给出了二氢卟吩环的¹H共振归属，从而能够精确探测与大环堆叠相关的环电流。DFT环电流位移计算表明，两种二氢卟吩在固态下均以反平行π堆叠的形式自组装在平面层中。同时，在80℃下对二氢卟吩2进行的X射线粉末衍射测量揭示了中尺度堆积的三维晶格，该晶格与分子力学优化的聚集体模型相匹配。对于二氢卟吩2，堆叠以0.68 nm的周期交替，三维晶胞的近似体积为6.28 nm³，包含4个分子，这与空间群P2(1)22(1)一致。
