Infrared and Raman spectroscopy of non-conventional hydrogen bonding betweenN,N′-disubstituted urea and thiourea groups: a combined experimental and theoretical investigation

Abstract

Selective study of intermolecular HBs with 2 types of HB acceptor.

Dumbbell‐Shaped T8‐POSS with Functional Organic Linkers

“…This may be attributed to the possible stronger H‐bonding between the urea‐thiourea groups in the former compared with the dumbbell compound holding two bulky POSS moieties at both ends of the latter structure . The bands due to the stretching vibrations ν(C=O) at 1654 cm –1 and δ(NH) at 1524 cm –1 are also observed . These results were confirmed by HR‐ESI mass spectroscopy with the molecular peak at m/z 1925 being very close to the expected theoretical value of 1922.…”

“…While this NH vibration is clearly seen in the case of the urea‐thiourea linker (Figure c) it is much less intense in the urea‐thiourea dumbbell (Figure b). This may be attributed to the possible stronger H‐bonding between the urea‐thiourea groups in the former compared with the dumbbell compound holding two bulky POSS moieties at both ends of the latter structure . The bands due to the stretching vibrations ν(C=O) at 1654 cm –1 and δ(NH) at 1524 cm –1 are also observed .…”

“…In this case, there was no issue with the selectivity of the reaction, as the resulting bis‐urea compound is symmetrical. Recent work within our group demonstrated that in the case of the corresponding thiourea reagent, the reaction did not proceed to completion for the substitution of both amino groups with urea derivatives . Instead, only one amino group was selectively transformed into the thiourea function, leaving the other one intact (Scheme a) to give the intermediate amino‐urea compound 3 (90 % yield).…”

CF3-groups critically enhance the binding of thiourea catalysts to ketones – a NMR and FT-IR study

“…26 In general, the NH stretching vibrations of the thiourea group are very sensitive to molecular associations, as the N-H stretching markedly red-shifts upon hydrogen-bond formation. 27 In Fig. 3 we show the infrared absorption spectra for solutions of 0CF-DPTU ( Fig.…”

Lilypad aggregation: localised self-assembly and metal sequestration at a liquid–vapour interface

“…S17, ESI †). In particular, shiing of the amide I band from 1654 cm À1 to 1710 cm À1 suggests that the urea carbonyl interacts more weakly in the aggregate, 79 and aggregation is likely driven by the formation of a nickel(II) complex. X-ray photoelectron spectroscopy (XPS) measurements on the surface of the vacuum-dried aggregate support this conclusion, as the presence of shake-up peaks in the Ni 2p region are diagnostic of a paramagnetic octahedral complex ( Fig.…”