Influence of metal coordination and light irradiation on hierarchical self-assembly processesElectronic supplementary information (ESI) available: Synthesis and characterization, description of experimental techniques, and additional images. CCDC 1864670. For ESI and crystallographic data in CIF or other electronic format see DOI: 10.1039/c8sc03875a

• Main Authors: Kartha, Kalathil K, Allampally, Naveen Kumar, Politi, Antiope T, Prabhu, Deepak D, Ouchi, Hayato, Albuquerque, Rodrigo Q, Yagai, Shiki, Fernández, Gustavo
• Format: Article
• Language: English
• ISSN: 2041-6520; 2041-6539
• DOI: 10.1039/c8sc03875a

Smart light-responsive supramolecular materials have been extensively investigated in the past decade, but so far the impact of metal coordination on hierarchical supramolecular structures of light-responsive building blocks has remained nearly unexplored. Herein, we unravel the hierarchical self-assembly of a small π-conjugated azo-containing pyridyl ligand that is able to respond to UV-light and metal complexation. The ligand self-assembles in an antiparallel fashion into long twisted fibers, which are then disassembled upon photoisomerization of the azobenzene groups, resulting in shorter rigid rods with a different packing motif. Complexation of Pd( ii ) ions enhances the cooperativity of the aggregation and induces a molecular rearrangement into slipped stacks with subsequent formation of long thin fibers. These are then transformed into thinner, shorter rods upon light irradiation. The observed different light-responsiveness, besides clearing up the influence of metal coordination and light irradiation in self-assembly processes, paves the way towards the design of novel supramolecular photochromic systems. We unravel the impact of metal coordination and light irradiation on hierarchical self-assembly processes by combined theoretical and experimental results.