Showing papers by "Rosa M. Claramunt published in 2017"

Supramolecular organization of perfluorinated 1H-indazoles in the solid state using X-ray crystallography, SSNMR and sensitive (VCD) and non sensitive (MIR, FIR and Raman) to chirality vibrational spectroscopies

Abstract: 1H-Indazole derivatives exhibit a remarkable property since some of them form chiral supramolecular structures starting from achiral monomers. The present work deals with the study of three perfluorinated 1H-indazoles that resolve spontaneously as conglomerates. These conglomerates can contain either a pure enantiomer (one helix) or a mixture of both enantiomers (both helices) with an enantiomeric excess (e.e.) of one of them. The difficulty of the structural analysis of these types of compounds is thus clear. We outline a complete strategy to determine the structures and configurations (M or P helices) of the enantiomers (helices) forming the conglomerates of these perfluorinated 1H-indazoles based on X-ray crystallography, solid state NMR spectroscopy and different solid state vibrational spectroscopies that are either sensitive (VCD) or not (FarIR, IR and Raman) to chirality, together with quantum chemical calculations (DFT).

The Curious Case of 2-Propyl-1H-benzimidazole in the Solid State: An Experimental and Theoretical Study.

Abstract: 2-Propyl-1H-benzimidazole (2PrBzIm) is a small molecule, commercially available, which displays a curious behavior in the solid state. 2PrBzIm, although devoid of chirality by fast rotation about a single bond of the propyl group in solution, crystallizes as a conglomerate showing chiroptical properties. An exhaustive analysis of its crystal structure and a wide range of experiments monitored by vibrational circular dichroism spectroscopy eliminated all possibilities of an artifact. What remains is a new example of the unexplained phenomenon of persistent supramolecular chirality.

19F‐NMR Diastereotopic Signals in Two N-CHF2 Derivatives of (4S,7R)-7,8,8-Trimethyl-4,5,6,7-tetrahydro-4,7-methano-2H-indazole

Abstract: In this paper, we report the anisochrony of the fluorine atoms of a CHF2 group when linked to a pyrazole ring. The pyrazole is part of (4S,7R)-7,8,8-trimethyl-4,5,6,7-tetrahydro-4,7-methano-2H-indazole also known as (4S,7R)-campho[2,3-c]pyrazole, which has two stereogenic centers. Gauge-Independent Atomic Orbital (GIAO)/Becke, 3-parameter, Lee-Yang-Parr (B3LYP)/6-311++G(d,f) calculated 19F chemical shifts of the minimum energy conformations satisfactorily agree with the experimental data. The energy differences between minima need to consider solvent effects (continuum model) to be satisfactorily reproduced.

Curcumin Related 1,4-Diazepines: Regioselective Synthesis, Structure Analysis, Tautomerism, NMR Spectroscopy, X-ray Crystallography, Density Functional Theory and GIAO Calculations

Abstract: The reaction of 1,2-ethylenediamine with seven fluorinated β-diketones affords two different 1,4-diazepine series depending on the experimental conditions. Their structures as well as tautomerism have been established by 1H, 13C, 15N and 19F nuclear magnetic resonance in solution supported by density functional theory calculations at the B3LYP/6-311++G(d,p) level. The two compounds obtained from (E)-5-(2-fluoro-4-hydroxyphenyl)-1-phenylpent-4-ene-1,3-dione were analyzed by X-ray crystallography and studied by solid-state NMR.

Crystal structure of (1Z,4Z)-2,4-dimethyl-3H-benzo[b][1,4]diazepine.

Abstract: The title compound, C11H12N2, is not planar due to the folding of the seven-membered ring. In the crystal, mol­ecules are packed opposite each other to minimize the electronic repulsion but the long inter­molecular distances indicate that no directional contacts are found.