Competition between OH⋯O and multiple halogen–dipole interactions on the formation of intramolecular three-centred hydrogen bond in 3-acyl coumarins

X-Ray Supramolecular Structure, NMR Spectroscopy and Synthesis of 3-Methyl-1-phenyl-1H-chromeno[4,3-c]pyrazol-4-ones Formed by the Unexpected Cyclization of 3-[1-(Phenyl-hydrazono)ethyl]-chromen-2-ones

“…It is noteworthy that in these compounds, neither –Cl, –Br or –NO 2 substituents in the benzenoid ring nor the lactone carbonyl, are involved in dipole-dipole interactions [ 33 , 34 ]. This observation contrasts with most of the coumarins studied by our group, whose supramolecular architectures are strongly influenced by the participation of these groups in multicentered interactions [ 35 , 36 ].…”

Thermal [4 + 2] Cycloadditions of 3-Acetyl-, 3-Carbamoyl-, and 3-Ethoxycarbonyl-Coumarins with 2,3-Dimethyl-1,3-butadiene under Solventless Conditions: A Structural Study

“…Thus, compound 15i is worthy to mention, since its crystal network is organized by several CH···O and Br···Br polarization-induced interactions, in the bc plane [ Figure 3 (a)], and CH···π bifacial contacts developing the third dimension along the (7 0 3) direction [( Figure 3 (b)]. The Br···Br i distance of 3.496(6) Å (symmetry code: ( i ) 1-x, 1-y, 2-z) is shorter than the reported value of 3.618(4) Å for 6-bromo- N -(2-hydroxyethyl)-2-oxo-2 H -1-benzopyran-3-carboxamide [ 13 ]. The geometric parameters associated with non covalent interactions are listed in Table 2 , C—H···O [ 14 ] and C—H···π [ 15 ] interactions are in agreement with accepted criteria and particularly with values reported for other coumarins [ 12 , 16 ].…”

Influence of the halogen substituent on the formation of halogen and hydrogen bonding in co-crystals formed from acridine and benzoic acids

“…Although crystallographic studies of proton transfer between acridine and acids (including benzoic acids) have been carried out, 12 structural investigations into the molecular complexes of acridine and ortho-and meta- 10 halobenzoic acids have not been performed. Thus, in order to explain how the ortho-and meta-halogen substituent in the phenyl ring of the benzoic acid influences the formation and competition of C-H···X hydrogen-bonds and X···O halogenbonds in the co-crystals formed from acridine and benzoic acids, 15 we synthesized and structurally characterized the following compounds: acridine • benzoic acid (1), acridine • 2fluorobenzoic acid (2), acridine • 2-chlorobenzoic acid (3), acridine • 2-bromobenzoic acid (4), acridine • 2-iodobenzoic acid (5), acridine • 3-fluorobenzoic acid (6), acridine • 3- 20 chlorobenzoic acid (7), acridine • 3-bromobenzoic acid (8) and acridine • 3-iodobenzoic acid (9) co-crystals. The number, type and strength of hydrogen bonds, halogen bonds, and melting points of co-crystals 1-9 were compared.…”