2-Indazole Tautomers Stabilized by Intra- and Intermolecular Hydrogen Bonds.

2-[(2-Indazol-3-yl)methylene]-1-indene-1,3(2)-dione and ()-2-[(2-indazol-3-yl)methylene]-2,3-dihydro-1-inden-1-one have been synthesized. In the crystal, the NH hydrogen atom of is disordered between the N(1) and N(2) atoms with the population ratio of 0.69:0.

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

A series of 7-hydroxy-2-methylidene-2,3-dihydro-1H-inden-1-ones with 2-pyrrolyl (3), 4-dimethylaminophenyl (4), 4-nitrophenyl (5), and carboxyl group (6) as substituents at the exocyclic double bond was synthesized in the form of the E-isomers (4-6) or predominantly as the Z-isomer (3) which in solution is converted to the E-isomer. The synthesized compounds and their model analogues were studied by NMR spectroscopy, X-ray analysis, and MP2 theoretical calculations. The E-isomers having intramolecular O-H···O═C hydrogen bond are converted by UV irradiation to the Z-isomers having bifurcated O-H···O···H-X hydrogen bond.

Variable coordination of tris(2-pyridyl)phosphine and its oxide toward M(hfac): a metal-specifiable switching between the formation of mono- and bis-scorpionate complexes.

An unexpected substitution of the anionic chelating ligands at the M centre by a neutral tripodal ligand has been observed in the reaction of Mn, Co, Ni and Cu hexafluoroacetylacetonates (hfac) with tris(2-pyridyl)phosphine (PyP) or its oxide (PyP = O). The nature of the metal ion in M(hfac) and the M/L ratio determine the degree of substitution of hfac-anions (partial vs. total) and therefore, the structure of the complex formed (scorpionate vs.

Molecular Structure and Photoinduced Intramolecular Hydrogen Bonding in 2-Pyrrolylmethylidene Cycloalkanones.

The structures of pyrrolylmethylidene derivatives of 2,3-dihydro-1H-inden-1-one (3), 3,4-dihydro-naphthalen-1(2H)-one (4), and cycloalkanones (5-7) were studied for the first time in the solid state and solution by NMR, IR, and UV spectroscopies supported by DFT quantum mechanical calculations. It was shown that all studied compounds except cycloheptanone derivative 7 both in crystal and in solution exist in the form of dimers where single E or E,E configuration with respect to the exocyclic C═C bond is stabilized by intermolecular hydrogen bonds N-H···O═C. UV irradiation at a wavelength of 365 nm of MeCN or DMSO solutions of 3-6 results, depending on the exposition time and solvent, partial to complete isomerization to the Z or Z,E isomers (in the case of 6, also the Z,Z isomer).