Multicolor Emission in <i>o</i>-Carborane Derivatives Induced by Conformation Diversity through C–C Double Bond Substitution

Rationally designed molecules with versatile conformations are ideal candidates for creating challenging single component-based multicolor emissive materials. Herein, a new strategy is presented by introducing a C-C double bond in an <i>o</i>-carborane derivative. Compared to a linear connection using a C-C triple bond (CbPyY), a C-C double bond connection (CbPyE) exhibited a zigzag structure and unique fluorescence behavior. Yellow, yellowish orange, and red crystals or films of CbPyE can be obtained, while only orange ones of CbPyY were achieved under the same condition. Single crystal XRD and theoretical calculation studies revealed the zigzag structure brings asymmetry to one arm of CbPyE, which causes conformation diversity and leads to the multicolor emission. Interestingly, different emissions showed different responses to acetone vapor; the yellow one showed much higher sensitivity and faster response than the other two. It is believed that the prepared materials and the proposed strategy would contribute to future advances in single-fluorophore-based multicolor emissive materials.