Backbone Boron-Functionalized Imidazoles/Imidazolium Salts: Synthesis, Structure, Metalation Studies, and Fluoride Sensing Properties

摘要

Incorporation of a Lewis acidic BMes(2) (Mes = mesityl) moiety at the backbone of the imidazole ring was achieved by metal-halogen exchange procedure. Among them, two isomeric boron-phosphine functionalized imidazoles (3 and 6), monoboron-functionalized imidazoles (4 and 5), and its corresponding imidazolium salts were synthesized and thoroughly characterized. The solid-state structure of 3 reveals a dimeric B-N adduct that possesses six-membered [C-B-N](2) ring, and 5 crystallizes as tetrameric B-N adduct that forms an interesting 16membered macrocycle, whereas 4 and 6 were obtained as monomeric BMes(2)-substituted imidazoles. 6 behaves as a PAN-type ligand upon the coordination with Cul to afford luminescent L2Cu4I4-type metal complexes (10 and 11) whose photophysical properties were also studied. The presence (in 10) and the absence (in 11) of BMes(2) made a remarkable impact on fluorescence emission causing shift from the green (10) to orange (11) region. The fluoride sensing properties of BMes(2)-containing imidazoles (4 to 9) were studied using UV-vis and fluorescence spectroscopy.