Luminescent mesogenic dimeric borondifluoride complexes

ABSTRACT

Two new families of dimeric borondifluoride complexes derived from β-enaminoketones containing terminal phenyl and naphthalenyl groups were prepared, and their mesomorphic and optical properties investigated. One single crystallographic structure of mesogenic complex 1a-BF₂ (n = 12) was determined by X-ray analysis; it crystallises in a monoclinic space group P21/c and the geometry on boron atoms was all tetrahedral. The crystal was considered as linear-shaped with a length of ~51.95 Å. A relatively large dihedral angle of ~38.85° between the central phenyl spacer and tetrahedral BF₂ moiety was observed. Mesomorphic properties were crucially impacted by the structure of the central spacer and terminal group; all bis(borondifluoride) complexes formed SmC or SmA phase except complexes 1b-BF₂ (m = 2, 3) and 1c-BF₂. H–bond interactions supported by FT-IR spectra were attributed to the induction of SmA phase in compound 2 c-BF₂. The optical property of the boron complexes was related with their molecular structures, and they emitted blue-to-green emissions at λ_max = 420–538 nm in CH₂Cl₂. This is the first twin liquid crystal of bis(BF₂) complexes derived from Schiff baseβ-enaminoketones.

Graphical Abstract

KEYWORDS:

• Bis(borondifluoride)
• β-enaminoketones
• luminescent
• mesogens
• smectic

Acknowledgments

We thank the Ministry of Science and Technology, Taiwan, ROC (MOST 108-2113-M-008-005) in generous support of this work. Also we deeply appreciated Prof. Hwo-Shuenn Sheu for performing powder XRD experiments at the National Synchrotron Radiation Research Center.

Disclosure statement

No potential conflict of interest was reported by the authors.

Supplementary material

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Additional information

Funding

This work was supported by Ministry of Science and Technology, Taiwan, ROC (MOST 108-2113-M-008-005)