The nature of resonance-assisted hydrogen bonds (RAHB) is still subject of an ongoing debate. We therefore analyzed the σ and π charge redistributions associated with the formation of intramolecular hydrogen bonds in malonaldehyde (MA) and its saturated analogue 3-hydroxypropanal (3-OH) and addressed the question whether there is a resonance assistance phenomenon in the sense of a synergistic i...

The vicinity of a hydrogen bond donor (O–H) and a hydrogen bond acceptor (C=O or C=N– R) in salicylaldehydes and ortho-Schiff bases results in significant structural variations compared to the monosubstituted derivatives that are reflected in the electronic structure and thus in the spectroscopic properties. This interplay between intramolecular hydrogen bonding and multicenter πelectron deloca...

In the mol-ecular structure of the title compound, C(21)H(15)N(3)O(4), the inter-planar angle between the benzoyl units is 89.7 (1)°. The corresponding angles between the phenyl-hydrazono and the benzoyl groups are 31.4 (3) and 60.8 (2)°, respectively. In the crystal, a strong resonance-assisted intra-molecular hydrogen bond (N-H⋯O) and a weak intra-molecular hydrogen bond (C-H⋯N) strongly affe...

The paper deals with the use of isotope effects on chemical shifts in characterizing intramolecular hydrogen bonds. Both so-called resonance-assisted (RAHB) and non-RAHB systems are treated. The importance of RAHB will be discussed. Another very important issue is the borderline between "static" and tautomeric systems. Isotope effects on chemical shifts are particularly useful in such studies. ...

The title compound, C(17)H(19)NO(3), adopts the phenol-imine tautomeric form, with a resonance-assisted O-H⋯N intra-molecular hydrogen bond [O⋯N = 2.551 (3) Å]. The dihedral angle between the two benzene rings is 45.42 (7)°. The two meth-oxy groups are coplanar with the attached benzene ring [C-O-C-C torsion angles = -1.1 (5) and 3.2 (4)°].

The mol-ecular structure of the title compound, C(21)H(15)ClN(2)O(2), features one strong intra-molecular N-H⋯O resonance-assisted hydrogen bond (RAHB). In the crystal, mol-ecules form inversion-related dimers via pairs of weak inter-molecular N-H⋯O contacts. These dimers are further stabilized via three weak C-H⋯O contacts, developing the three-dimensional structure.

We have generated 3 ns molecular dynamic (MD) simulations, in aqueous solution, of the bacterial soluble glucose dehydrogenase enzyme.PQQ.glucose complex and intermediates formed in PQQ reduction. In the MD structure of enzyme.PQQ.glucose complex the imidazole of His144 is hydrogen bonded to the hydroxyl hydrogen of H[bond]OC1(H) of glucose. The tightly hydrogen-bonded triad Asp163-His144-gluco...

In the title compound, C(8)H(9)N(5)O, the mean planes through the pyrimidine and triazine rings form a dihedral angle of 2.83 (16)°. The amino group adopts a trigonal-planar configuration and forms an intra-molecular resonance-assisted N-H⋯O=C hydrogen bond with the carbonyl group. In the crystal, mol-ecules are linked via inter-molecular N-H⋯N hydrogen bonds into chains of C(2) (2)(6)[R(2) (2)...