The mol-ecule of accanthomine A, C(15)H(13)N(5), is approximately planar, with the indolyl fused-ring and the pyrimidyl ring being twisted by 31.7 (1)° The amino group of the five-membered ring is an intramolecular hydrogen-bond donor to a nitro-gen acceptor of the pyrimide ring. The amino group of the pyrimide ring is a hydrogen-bond donor to the N atoms of adjacent mol-ecules. These hydrogen-...

We discuss theoretically the geometric and electronic structure properties of the thiazolidinedione derivative A and its hydrogen-bonded complex in dimethylformamide (DMF) solution in the S0 and S1 states. To gain insight into the photoinduced coupled excited-state proton transfer (ESPT) and twisted intramolecular charge transfer (TICT) associated with intermolecular hydrogen bonding, the poten...

We have synthesized a molecule containing a tight hydrogen-bonding interaction between an alcohol and a nonconjugated π-system. The strength of this hydrogen bond results in a large red shift, nearly 189 cm(-1), on the alcohol stretching frequency in the IR spectrum in comparison to a free alcohol control. The interaction is notable in that it possesses a better defined intramolecular hydrogen ...

Ab initio and density functional calculations are applied to study the influence of an increasing number of chlorine substituents on the properties of the intramolecular hydrogen bond in substituted Mannich bases. It is shown, that not only the acidity of the proton donor, which depends on the number of chlorine atoms at the aromatic ring, but also steric interactions modify the geometry of the...

In molecules of the title compound, C(14)H(12)N(2)O(4), the conformation is dominated by an intramolecular N-H.O hydrogen bond in which one of the nitro O atoms is the acceptor. The molecules are linked by paired C-H.O hydrogen bonds [H.O = 2.41 A, C.O = 3.2990 (17) A and C-H.O = 156 degrees ] into centrosymmetric R(2)(2)(14) dimers; these dimers are linked weakly into chains of alternating R(2...

In the title compound, C(11)H(16)ClNO, the side chain of the ethyl-amine group is almost perpendicular to the benzene ring; the dihedral angle between the C/C/N plane of the ethyl-amine grouping and the benzene plane is 87.4 (2)°. An intramolecular N-H⋯O hydrogen bond occurs. In the crystal structure, mol-ecules are connected weakly by O-H⋯N hydrogen bonds, forming a tetra-mer around the symmet...

In the present work, DFT calculations are employed to obtain the optimized structures of 4- acyl pyrazolone tautomers (19 tautomers) using B3LYP/6-311++G** calculations. In addition, molecular parameters, IR frequencies and relative energies are extracted for all tautomers. The existence of aromatic ring, keto tautomer (versus enol tautomer), N-H bond (versus C-H bond) and C=N double bond (vers...

The title compound, C 6 H 8 N 2 O 4 , a new derivative of isoxazole, has been synthesized and structurally characterized. crystal structure shows the molecule to be almost planar (r.m.s. deviation for non-hydrogen atoms = 0.029 Å), this conformation being supported by an intramolecular N—H...O hydrogen bond. In extended structure, molecules are linked bonds into chains propagating along [010].

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 acidity constants of 5-uracilmethylphosphonic acid, H2(5Umpa), and 6-uracilmethylphosphonic acid, H2(6Umpa), were determined by potentiometric pH titrations in aqueous solution (25 °C; I = 0.1 M, NaNO3). Comparison of these constants with those of related uracil derivatives (partly taken from the literature) allows the conclusion that an intramolecular hydrogen bond is formed between (N1)H ...