Spectroscopic studies of bifurcated hydrogen bonds in solution

Photoinduced Intramolecular Bifurcate Hydrogen Bond: Unusual Mutual Influence of the Components

“…While the existence of bifurcated hydrogen bonds in crystals was unambiguously proved experimentally by different methods, and was studied in detail theoretically in the gas phase, the existence of bifurcated H-bond in liquids was disputable for a long time. , Both IR and NMR spectroscopy methods used for investigation of bifurcated H-bonds in solution suffer from inherent limitations. The advantage of IR spectroscopy is its short characteristic time allowing observation of separate species in fast equilibrium with others, but its flaw is that the conclusions on the H-bonds are usually based on the changes observed for covalent X–H bonds (special measurements in far-IR region are very scarce, see, e.g., ref ).…”

Hydrogen bonding in aromatic polyamine 2-guanidinobenzimidazole: Study based on density functional theory calculations

“…Among the different kinds of unconventional hydrogen bonds we can mention those containing C-H proton donors, those where p-electrons are proton acceptors and even such systems where both the proton donor and the proton acceptor are unconventional [1b]; the dihydrogen bonds usually designated as X-HÁ Á ÁH-Y [3b, 6] where X-H is the typical proton donating and the other hydrogen atom, H(Y), with excess of negative electron charge, is the proton acceptor. The unconventional bifurcated hydrogen bond (BHB) [7] that involves different double hydrogen bonded configurations with non-lineal hydrogen bonds has also been considered in the literature.…”

“…In this way, by the application of direct crystal structure analysis methods, other patterns of hydrogen bonding structure were obtained; an example of this is the fact that hydrogen bonds observed in the solid state are of the BHB type, these being rarely linear [7]. Likewise, in the last years plenty of theoretical investigations related with experimental investigations were performed [3b,11].…”

An analysis of bifurcated H‐bonds: crystal and molecular structures of O,O‐diphenyl 1‐(3‐phenylthioureido)­pentanephosphonate and O,O‐diphenyl 1‐(3‐phenylthioureido)butanephosphonate

“…11,12 The IR and 1 H NMR spectra of solutions containing 2,6-disubstituted phenol derivatives with strong intramolecular H-bonds confirmed the existence of the bifurcated H-bonds in the liquid state. 13 The aim of this paper is to describe bifurcated N-HÁÁÁO hydrogen bonds with two N-H donors and one oxygen-accepting centre. Such H-bonds were recently found, for example, for the crystal structures of O,Odiphenyl N-phenylthioureidoalkanephosphonates 14,15 and may be partly described in terms of R 2 1 (6) topological motifs (Scheme 1).…”