Structural and Spectroscopic Properties of Aryl Substituted Aminoboranes as Model Compounds and Synthons for B/C/N Materials and New Fluorescent Systems

Abstract

AbstractTetraphenylaminoborane (1) and carbazonyldiphenylborane (2) are examples for isolated BN bonds completely substituted by aryl ligands, which enable π‐interactions. Such systems can serve as building blocks for new fluorescent polymers and are also suitable precursors for B/C/N materials. The compounds were characterized by multinuclear NMR spectroscopy, UV/Vis spectroscopy, and single‐crystal X‐ray diffractometry. Both compounds 1 and 2 are principal structures for tricoordinate, aryl substituted BN bonds. Compound 1 crystallizes in the monoclinic crystal system in the space group P21, with two formula units per unit cell with a = 9.8236(9) Å, b = 9.2743(8) Å, c = 10.7426(10) Å; α = 90°, β = 107.228(4)°, γ = 90°, Z = 2, V = 934.81(15) Å3 (final R indices [I > 2 σ(I)]: R1 = 0.0597; wR2 = 0.1489) and compound 2 crystallizes in the monoclinic crystal system of the space group C2/c. The unit cell contains four formula units as a set of two pairs of diastereomers. The cell parameters are a = 17.404(4) Å, b = 11.020(2) Å, c = 9.4195(19) Å; α = 90°, β = 91.45(3)°, γ = 90°, Z = 4, V = 1805.9(6) Å3 (final R indices [I > 2 σ(I)]: R1 = 0.038; wR2 = 0.0847). The UV/Vis spectra of 1 and 2 reveal strong absorptions (240 nm and 285 nm) for 1 and broad features (260 nm and 290 nm) for 2. The 11B NMR spectroscopic data of 1 (48.7 ppm) and 2 (53.0 ppm) clearly indicate tricoordinate BN systems in solution with a weaker BN π‐interaction compared to dialkylborylamines.