Seed-Induced Pathway Control of Low-Dispersity Polymorphic\nMicrocrystals of pi-Conjugated Molecules

The\nprecise synthesis of polymorphic π-conjugated micro-\nand nanocrystals remains challenging due to the existence of competing\nassembled pathways. Here we realize controlled polymorphic microcrystals\nof a dicyanodistyrylbenzene derivative (<b>A</b>) via a seed-induced\npathway transformation. Small-sized α-<b>A</b> nanocrystals\nthat are thermodynamically stable are prepared via a microspacing\nphysical vapor transport (PVT) method. These vapor-grown nanocrystals\nfunction as seeds and tailor the assembled pathway of potentially\noccurring β-<b>A</b> microcrystals corresponding to kinetically\nmetastable products, leading to the controlled growth of α-<b>A</b> microcrystals. Intriguingly, the length and surface area\nof the seed-induced α-<b>A</b> microcrystals increase\nlinearly with the molar ratios of the added monomer to seeds. Such\na seed-induced transformation strategy resembles living supramolecular\npolymerization of amphiphilic dyes, which is also applicable to more\npolymorphic π-conjugated microcrystals even binary alloys. This\nwork provides deeper insights in controlling assembled pathways and\npolymorphs of π-conjugated systems and producing organic microcrystals\nof narrow size distributions.