Surface Functionalization of Black Phosphorus with Nitrenes: Identification of P=N Bonds by Using Isotopic Labeling

Abstract

Surface functionalization of two-dimensional crystals is a key path to tuning their intrinsic physical and chemical properties. However, synthetic protocols and experimental strategies to directly probe chemical bonding in modified surfaces are scarce. Introduced herein is a mild, surfacespecific protocol for the surface functionalization of few-layer black phosphorus nanosheets using a family of photolytically generated nitrenes (RN) from the corresponding azides. By embedding spectroscopic tags in the organic backbone, a multitude of characterization techniques are employed to investigate in detail the chemical structure of the modified nanosheets, including vibrational, X-ray photoelectron, solid state 31 P NMR, and UV-vis spectroscopy. To directly probe the functional groups introduced on the surface, R fragments were selected such that in conjunction with vibrational spectroscopy, 15 N-labeling experiments, and DFT methods, diagnostic P = N vibrational modes indicative of iminophosphorane units on the nanosheet surface could be conclusively identified.

Molecularly Engineered Black Phosphorus Heterostructures with Improved Ambient Stability and Enhanced Charge Carrier Mobility

“…Alternatively, chemical functionalization is a preferred strategy in terms of using BP sheets toward solution processing and the precise control over the designed properties. For instance, covalent functionalization of BP, relying on the formation of PC, POC or PN bonds with reactive intermediates such as free radicals, [ 13 ] nitrenes, [ 14 ] and carbocations, [ 15 ] protects the topological structure of BP sheets. However, this strategy largely compromises their electronic properties due to the direct breaking of PP bonds.…”

Synthesis of Unsupported Primary Phosphido Complexes of Aluminum(III)

“…Other Physical Measurements. 1 H-NMR, 13 C-NMR, 31 P-NMR, spectra were recorded at ambient temperature using a Varian 600 MHz or 400 MHz spectrometer. Chemical shifts were referenced to residual solvent.…”

“…Crystals were grown as brown blocks from a concentrated toluene solution and stored at À 25 °C overnight . 1 H-NMR (600 MHz, C 6 D 6 ): δ 7.08-6.80 (m, 18H, Ar, m-py, PHC 6 H 5 ), 6.27 (t, J = 7.3 Hz, 1H, p-py, PHC 6 H 5 ), 5.90 (t, J = 7.7 Hz, 1H, p-py), 3.20 (d, J = 224 Hz, 1H, PH), 1.26 (s, 6H CH 3 ). 0.75 (s, 6H, (CH 3 ).…”

“…Materials containing element -phosphorous multiple bonds continue to receive interest for their promising materials properties. [1] Ongoing efforts to expand the scope of Group 13 -Group 15 containing species, with single, double, or triple bonds have resulted in many contributions to Al and Ga chemistry. Using the combination of Al and P has thus far led to the isolation of some terminal AlÀ phosphido complexes which contain an AlÀ P single bond.…”

“…1 H-NMR (600 MHz, C 6 D 6 ): δ 7.14-6.84 (m, 18H, Ar, m-py), 6.64 (s, 3H, Mes), 5.77 (t, J = 7.7 Hz, 1H, p-py), 3.37 (hept, J = 6.7 Hz 4H, CH(CH 3 ) 2 ), 2.97 (d, J = 215.5 Hz, 1H, PH), 2.26 (s, 9H, Mes), 1.10 (d, J = 6.8 Hz, 6H, CH(CH 3 ) 2 ). 0.74 (d, J = 6.6 Hz 6H, CH(CH 3 ) 2 ).…”