On the structure of meso-substituted F-BODIPYs and their assembly in molecular crystals: An experimental-theoretical approach

•Molecular crystals were solved in the P -1 space group.•UV–vis excitations have been computed and correlated with the experiments.•The electron density for each unit cell was analyzed by QTAIM.•NBO mapping of intermolecular orbital overlap was derived.•Density of states was derived through CASTEP analysis.

Molecular crystals of meso-(5-((4-formylphenyl)ethynyl)thiophen-2-yl)-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene 4a and meso-(4-((4-formylphenyl)ethynyl)phenyl)-4,4-difluoro-4-bora-3a,4a-diaza-s-indacene 4b were synthesized using palladium(0)-catalyzed Sonogashira cross coupling reactions and characterized using an experimental-theoretical approach. The crystal structures of F-BODIPYs 4a-b are structurally analogous, yet their crystal packing motifs displayed remarkable differences due to contrasting hydrogen-bonding interactions. A CASTEP study of the unit cell for each compound provided the theoretical band structure and density-of-states (DOS) diagrams for each molecular crystal, suggesting a semiconductor character for both solids. Analysis of the computed electron density with Bader's QTAIM describes the intermolecular-contact network within each periodic system, while Natural Bonding Orbitals (NBO) display in-phase overlap between stacked units, denoting intermolecular delocalization of the electron density via stacking. TDDFT analysis of solution UV-Vis spectra gives insight into the nature of the observed excitations along with the effects derived from the relative rotation of π-subsystems in solution.

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