Understanding the solid-state emission of a trio of 1,4-diaryl-1,3-butadiynes in terms of their molecular structure and crystal packing interactions

• Published in: Journal of molecular structure Vol. 1177; pp. 9 - 15
• Main Authors: San Angelo, Michael, Khago, Domarin, Choi, Brandon, Fronczek, Frank R., Isovitsch, Ralph
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 05.02.2019
• Subjects: 1,4-Diaryl-1,3-butadiynes; Crystal packing interactions; Solid-state absorption and emission; X-ray structures; Crystal packing interactions; Solid-state absorption and emission; 1,4-Diaryl-1,3-butadiynes; X-ray structures
• ISSN: 0022-2860; 1872-8014
• DOI: 10.1016/j.molstruc.2018.09.041

A trio of 1,4-diaryl-1,3-butadiynes with methoxy and trifluoromethoxy substituents in the 4- and 4′-positions were prepared in useful yields (42% for one, 95+% for the others), their structures determined and their purity ascertained. Analysis of the single crystal X-ray data for the three compounds revealed that two were mostly planar with small dihedral angles of 6–9° between their aryl rings, while one existed in a twisted conformation with a dihedral angle of approximately 53° between it's aryl rings. The solid-state absorption spectra of all three compounds were similar, with structured absorptions at approximately 340 nm. One of the compounds had absorption bands at 263 and 457 nm. Two of the compounds had similar emission bands with maxima that ranged from 440 to 450 nm, while the other was quite different, with a broad emission band with a maximum at 564 nm. Each of the three compounds had excited state decay traces that were fit to tri-exponential curves which yielded three lifetimes: a longer one attributed to aggregate emission, a shorter one arising from an intermolecular charge transfer transition, and a medium one that is assigned to a locally excited transition. [Display omitted] •A trio of 1,4-diaryl-1,3-butadiynes were prepared in useful yields.•The purity and identity of the butadiynes was ascertained.•X-ray structures of two of the butadiynes were determined.•Steady-state and time-resolved photophysical properties of the solid butadiynes were examined.•Observed photophysical properties were rationalized in terms of structure and crystal packing interactions.