Intramolecular and intermolecular bifurcated hydrogen bonds in 2‐pyrrolyl‐7‐hydroxy‐2‐methylidene‐2,3‐dihydro‐1H‐inden‐1‐one

Abstract

Cyclic and linear dimers as well as the solvate H-bonded complexes of the Z and E isomers of 2-pyrrolyl-7-hydroxy-2-methylidene-2,3-dihydro-1H-inden-1one 1 were investigated by theoretical calculations, and their formation was proved by FT-IR and UV spectroscopy. In dimers, both strengthening and weakening of the intramolecular component of the bifurcated hydrogen bond are observed depending on the type of the formed intermolecular hydrogen bond. The effect of proton donors MeOH, HCN, and proton acceptor DMSO on the intramolecular components in solvent H-bonded complexes is discussed. A larger energy gap in the 1-E than in 1-Z isomer allows to predict photoinduced isomeric transition 1-Е → 1-Z in nonpolar aprotic solvents.

Fully zwitterionic diaminobenzoquinonediimines promoted by cyanoaromatic N-substituents

“…By examining the actual geometries predicted by DFT, we could rationalize this outcome. Indeed, as can be seen in Figure 6, in the canonical form of 1, a bifurcated hydrogen bond absent in the zwitterion is present [50,51], as the transferred hydrogen atom is in close contact with one of the oxygen atom of the vicinal ortho nitro group. Such interaction is absent in where the transferred hydrogen atom is more than 2.8 Å away from the nitrogen atom of the cyano group.…”