Charge‐Transfer Emission Involving Three‐Coordinate Organoboron: V‐Shape versus U‐Shape and Impact of the Spacer on Dual Emission and Fluorescent Sensing

Abstract

New V-shaped bifunctional organosilicon compounds that contain an electron acceptor, B(Mes)2, and an electron donor, N(1-naph)Ph, with the formulae Ph2Si{p-C6H4B(Mes)2}{p-C6H4N(1-naph)ph)} (1), Ph2Si{p-C6H4(Mes)2}{p-biphenyl-N(1-naph)ph} (2), and Si{p-C6H4B(Mes)2}2{p-C6H4N(1-naph)ph)}2 (3) have been synthesized as model compounds for the investigation of through-space charge-transfer emission involving triarylboron and triarylamino centers. The photophysical properties of the new bifunctional organosilicon compounds are compared to two U-shaped compounds sBN and BN in which the boron acceptor and the amino donor groups are linked together by a rigid 1,10-naphthyl group. The results of our investigation establish that dual emission pathways, namely through-space donor-acceptor charge transfer and pi-pi* transitions coexist in the V-shaped molecules 1-3, while charge transfer emission is dominant in the U-shaped molecules. It is found that depending on the geometry of the linker and the BN separation distance, the compound either displays dual emission bands simultaneously or single emission band. In addition, the dual emission pathways in these molecules can be selectively switched on or off by using fluoride ions. The sensitivity of response to fluoride ions by these molecules is also found to be highly dependent on the geometry of the linker and the BN separation distance. The V-shaped molecules are found to be "turn-on" sensors to fluorides with a much higher sensitivity than the U-shaped molecules.

Tetrahedral silicon-centered imidazolyl derivatives: Promising candidates for OLEDs and fluorescence response of Ag (I) ion

“…The bromo-substituted groups in 5 and 6 didn't have contribution to the HOMO or LUMO orbitals. The results also indicated that the tetrahedral silicon core does not have significant effect on the electronic properties of 1e6, which is consistent with previous reports [6,7]. It is noteworthy that these compounds all have a deep energy gap with the range from 4.9585 eV (6) to 5.1879 eV (1).…”

A trivalent organoboron compound as one and two-photon fluorescent chemosensor for fluoride anion

“…Gabbaï and coworkers have made excellent progress of chelating a fluoride anion by combining dimesitylboryl and another F − sensitive group [14][15][16][17][18][19]. Wang and co-workers also demonstrated their results of F − sensing fluorescent borane based on different charge-transfer emission from B--N derivatives [20][21][22]. The F − bonding action by triarylborane-functionalized polystyrene was also found by Jäkle et al [23].…”

“…Recently, several research groups have reported that trivalent boron compounds can be used as effective colorimetric, fluorescent, or ratiometric sensors for the detection of fluoride by utilizing the empty p orbital on the boron center [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25][26]. Yamaguchi et al firstly reported the colorimetric fluoride ion sensing of triarylboron [11][12][13].…”

A class of fascinating optoelectronic materials: Triarylboron compounds

“…[29]). Figure 8) [30]. The emission color of these compounds changed evidently after addition of F  , which was attributed to the dual fluorescent emission.…”