We report a novel class of star-shaped multi-azobenzene photoswitches comprising individual photochromes connected to a central trisubstituted 1,3,5-benzene core. The unique design of such C3-symmetric molecules, consisting of conformationally rigid and pseudo-planar scaffolds, made it possible to explore the role of electronic decoupling in the isomerization of the individual azobenzene units. The design of our tris-, bis-and mono(azobenzene) compounds limits the π-conjugation between the switches belonging to the same molecule, thus enabling their efficient and independent isomerization of each photochrome. An in-depth experimental insight by making use of different complementary techniques such as UV-Vis absorption spectroscopy, high performance liquid chromatography and advanced mass spectrometry methods as ion mobility revealed an almost complete absence of electronic delocalization. Such evidence was further supported by both experimental (electrochemistry, kinetical analysis) and theoretical (DFT calculations) analyses. The electronic decoupling provided by this molecular design guarantees a remarkably efficient photoswitching of all azobenzenes, as evidenced by their photoisomerization quantum yields, as well as by the Z-rich UV photostationary states. Ion mobility mass spectrometry was exploited for the first time to study multi-photochromic compounds revealing the occurrence of a large molecular shape change in such rigid star-shaped azobenzene derivatives. In view of their high structural rigidity and efficient isomerization, our multi-azobenzene photoswitches can be used as key components for the fabrication of complex stimuli-responsive porous materials. ASSOCIATED CONTENTThe Supporting Information is available free of charge via the Internet at: www.------.com Detailed experimental procedures, synthesis and characterization of the products, computational methodologies.

We report the synthesis of a novel C3-symmetrical multiphotochromic molecule bearing three azobenzene units at positions 1,3,5 of the central phenyl ring. The unique geometrical design of such a rigid scaffold enables the electronic decoupling of the azobenzene moieties to guarantee their simultaneous isomerisation. Photoswitching of all azobenzenes in solution was demonstrated by means of UV-Vis absorption spectroscopy and high performance liquid chromatography (HPLC) analysis. Scanning tunnelling microscopy investigations at the solid-liquid interface, corroborated by molecular modelling, made it possible to unravel the dynamic self-assembly of such systems into ordered supramolecular architectures, by visualising and identifying the patterns resulting from three different isomers, thereby demonstrating that the multi-photochromism is retained when the molecules are confined in two-dimensions. Figure 1. Chemical structure of tris(azobenzene) compound 1 and its non-photoactive analogue 2.The Supporting Information is available free of charge via the Internet at http://pubs.acs.org.. Detailed experimental procedures; synthesis and characterisation of the products, computational methodologies.

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