Heteronuclear NMR spectroscopic investigations of hydrogen bonding in 2-(benzo[d]thiazole-2′-yl)-N -alkylanilines

Abstract

The 2-(benzo[d]thiazole-2'-yl)-N-alkylanilines have previously revealed the presence of a strong intramolecular hydrogen bond. This in turn gives rise to a more complicated multiplet for the protons attached to the carbon adjacent to the amino group. This intramolecular hydrogen bond was investigated by a deuterium exchange experiment using heteronuclear NMR spectroscopy (1H, 13C, 15N and 2H). We observed changes in the multiplet structure and chemical shifts providing further evidence that the deuterium replaces the hydrogen in the intramolecular hydrogen bond. A time course study of the D2O exchange confirmed the presence of a strong hydrogen bond. The comparison of the structures obtained by X-ray crystallography showed a very small difference in planarity between the two-substituted and four-substituted amino compounds. In both the cases, the phenyl ring is not absolutely coplanar with the thiazole unit. The existence of this intramolecular hydrogen bond in 2-(benzo[d]thiazole-2'-yl)-N-alkylanilines was further confirmed by single crystal X-ray crystallography.

Synthesis and photophysical properties of rare earth (La, Nd, Gd, Y, Ho) complexes with silanediamido ligands bearing a chelating phenylbenzothiazole chromophore

“…Still, several T-shaped p interactions can be found, and the most noticeable ones are between the lone electron pairs of a sulfur atom with the nearest benzothiazole cycle (angle of 591 between the heterocycle planes, d(SÁ Á ÁC2 0 ) = 3.58 Å, d(SÁ Á ÁC2) = 3.46 Å). Similar p contacts are present in the structure of MeN(H)-Pbt, 28 where the closest distance is found between the sulfur atom and carbon atoms of the benzothiazole unit of the neighboring molecule (611 angle between heterocycle planes, d(SÁ Á ÁC7 0 ) = 3.48 Å, d(SÁ Á ÁC7a 0 ) = 3.84 Å). Deprotonation of the earlier studied Dipp-and Messubstituted silanediamines was easily achieved by treatment with KH.…”

“…After performing measurements, Scheme 1 Conventional designation of silanediamine and numbering of atoms in the Pbt substituent according to IUPAC. 28 the intensity of luminescence of the samples did not decrease, which meant that the solutions remained intact.…”

Lanthanide complexes with a new luminescent iminophosphonamide ligand bearing phenylbenzothiazole substituents

“…The numbering of atoms in the Pbt substituent according to IUPAC is given. 78 Table 1 Selected distances and angles for compounds 1, 1•CH 3 CN, and 3-6 from the XRD data. Parameters for two Pbt fragments of one ligand are separated by a slash and given in the same order; each line contains data for a separate ligand…”