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We report here the synthesis, characterization, and crystal structures of three perfluoropropylated dibenzo[ a , c ]phenazine constitutional isomers, in which the only difference among them was the positions of the perfluoropropyl substituents. The crystal structures of these perfluropropylated dibenzo[ a , c ]phenazine isomers indicated that the stereo-electronic effect of the perfluoropropyl group on the dibenzo[ a , c ]phenazine molecule plays a crucial role in determining the crystal-packing motif in the solid state. Our results from both X-ray crystallography and computational approaches revealed that the positions of the perfluoropropyl groups on the dibenzo[ a , c ]phenazine ring significantly affected the electrostatic potential distribution along the aromatic ring surface, resulting in drastic changes in the molecular packing in the solid state, from herringbone to lamellar crystal packing, among these three constitutional isomers. Simple topological consideration of the molecular packing in the solid state was coincidently cooperative with the changes in the electrostatic potential distributions, where localized partial positive and partial negative charges perhaps dominated the intermolecular interactions between the aromatic rings. Together, the perfluoropropylation on the dibenzo[ a , c ]phenazine ring provided us with a fortunate scenario, wherein the molecular topological structure and electrostatic potential worked together to facilitate the formation of the desired lamellar π–π stacked crystal packing. Meanwhile, electrochemistry, UV-visible absorption and emission spectra, and the computational chemistry results pointed out that there were only minor to moderate changes in the electronic properties of the molecules upon changing the position of the perfluoroalkylation on the dibenzo[ a , c ]phenazine core. While controlling the solid-state structure of aromatics by design still has a long way to go, we hope that our work will ignite a spark that can potentially spread into the field of the design of organic solid-state materials. 

ABSTRACT The ATOMS, standing for ALMA Three-millimeter Observations of Massive Star-forming regions, survey has observed 146 active star-forming regions with ALMA band 3, aiming to systematically investigate the spatial distribution of various dense gas tracers in a large sample of Galactic massive clumps, to study the roles of stellar feedback in star formation, and to characterize filamentary structures inside massive clumps. In this work, the observations, data analysis, and example science of the ATOMS survey are presented, using a case study for the G9.62+0.19 complex. Toward this source, some transitions, commonly assumed to trace dense gas, including CS J = 2−1, HCO+J = 1−0, and HCN J = 1−0, are found to show extended gas emission in low-density regions within the clump; less than 25 per cent of their emission is from dense cores. SO, CH3OH, H13CN, and HC3N show similar morphologies in their spatial distributions and reveal well the dense cores. Widespread narrow SiO emission is present (over ∼1 pc), which may be caused by slow shocks from large–scale colliding flows or H ii regions. Stellar feedback from an expanding H ii region has greatly reshaped the natal clump, significantly changed the spatial distribution of gas, and may also account for the sequential high-mass star formation in the G9.62+0.19 complex. The ATOMS survey data can be jointly analysed with other survey data, e.g. MALT90, Orion B, EMPIRE, ALMA_IMF, and ALMAGAL, to deepen our understandings of ‘dense gas’ star formation scaling relations and massive protocluster formation.