Transformation from kinetically into thermodynamically controlled self-organization of complex helical columns with 3D periodicity assembled from dendronized perylene bisimides.

ABSTRACT

The dendronized perylene 3,49,10-tetracarboxylic acid bisimide (PBI), (3,4,5)12G1-1-PBI, was reported by our laboratory to self-assemble into complex helical columns containing dimers of dendronized PBI with one molecule in each stratum, with different intra- and interdimer rotation angles but identical intra- and interdimer distance of 3.5 Å, exhibiting a four-strata 2(1) helical repeat. A thermodynamically controlled 2D columnar hexagonal phase with short-range intracolumnar order represents the thermodynamic product at high temperature, while a kinetically controlled monoclinic columnar array with 3D periodicity is the thermodynamic product at low temperature. With heating and cooling rates higher than 10 °C/min to 1 °C/min, at low temperature the 2D columnar periodic array is the kinetic product for this dendronized PBI. Here the synthesis and structural analysis of a library of (3,4,5)nG1-m-PBI with n = 12 to 6 and m = 1 are reported. A combination of differential scanning calorimetry, X-ray diffraction on powder and orientated fibers, including pattern simulation and electron density map reconstruction, and solid-state NMR, all as a function of temperature and heating and cooling rate, was employed for their structural analysis. It was discovered that at low temperature the as-prepared n = 12 to 10 exhibit a 3D layered array that transforms irreversibly into columnar periodicities during heating and cooling. Also the kinetically controlled 3D columnar phase of n = 12 becomes thermodynamically controlled for n = 10, 9, 8, 7, and 6. This unprecedented transformation is expected to facilitate the design of functions from dendronized PBI and other self-assembling building blocks.