Photophysical Behavior of Self-Organizing Derivatives of 10-and 12-Vertex p-Carboranes, and their Bicyclo[2.2.2]octane and Benzene Analogues

Four series of isostructural derivatives of 3-ring liquid crystalline derivatives containing p-carboranes (12 vertex A, and 10-vertex B), bicyclo[2.2.2]octane (C), or benzene (D) as the variable structural element were investigated for their mesogenic behavior and electronic interactions. Comparative studies demonstrated that the effectiveness of elements A-D in stabilization of the mesophase typically increases in the order: B Spectroscopic characterization was supplemented with polarization electronic spectroscopy and solvatochromic studies of selected series. Overall, 12-vertex p-carborane A acts as an electron withdrawing auxochromic substituent with interactions similar to those of bicyclo[2.2.2]octane, although capable of accepting some electron density in the excited state. In contrast, 10-vertex p-carborane B is much more interactive with the 7E-aromatic electron manifold and exhibits greater ability to participate in photo-induced CT processes. Absorption and emission energies and quantum yields (151 %) for carborane derivatives, representing the D -A -D system, were compared to those of their isoelectronic zwitterionic analogues (the A -D -A system). The analysis is supplemented with four single-crystal XRD structures.

Automated summary

The mesogenic behavior and electronic interactions of four series of isostructural derivatives of 3-ring liquid crystalline derivatives containing p-carboranes, bicyclo[2.2.2]octane, or benzene as the variable structural element were investigated. Comparative studies demonstrated that the effectiveness of the different structural elements in stabilization of the mesophase typically increases in the order of B Spectroscopic characterization was supplemented with polarization electronic spectroscopy and solvatochromic studies. Overall, the analysis included absorption and emission energies, quantum yields, and crystal structure determination.