Ferrocenyl pyrazaboles: design, synthesis, structure, and properties.

This article reports the design and synthesis of donor-acceptor-donor type ferrocenyl-substituted pyrazaboles by the Pd-catalyzed Suzuki and Sonogashira coupling reactions. The photophysical and electrochemical behaviors of the ferrocenyl-substituted pyrazaboles were found to be dependent on the nature and length of the spacer groups. The single crystal X-ray structures of ferrocenyl-substituted pyrazaboles 11a, 11b, and 11d were obtained, which reveals that the pyrazabole core exists in chair, planar, and boat conformations. The crystal structures show marvelous supramolecular interactions. The pyrazaboles 11a-11g show good thermal stability, which increases with the length of spacer. The computational study reveals donor-acceptor interactions in ferrocenyl pyrazaboles. The computational results show good agreement with the experimental results.