Nitrile IR intensities characterize electric fields and hydrogen bonding in protic, aprotic, and protein environments

Nitriles are widely used as vibrational probes; however, the interpretation of their IR frequencies is complicated by hydrogen bonding (H-bonding) in protic environments. We report a new vibrational Stark effect (VSE) that correlates the electric field projected on the nitrile bond to the transition dipole moment and, by extension, the nitrile peak area or integrated intensity. This linear VSE applies to both H-bonding and non-H-bonding interactions. It can therefore be generally applied to determine electric fields in all environments. Additionally, it allows for semi-empirical extraction of the H-bonding contribution to the blueshift of the nitrile frequency. Nitriles were incorporated at H-bonding and non-H-bonding protein sites using amber suppression, and each nitrile variant was structurally characterized at high resolution. We exploited the combined information now available from variations in frequency and integrated intensity and demonstrate that nitriles are a generally useful probe for electric fields.

Bis(dimethylamine-κN)bis[4-(1,2,4-triazol-1-yl)benzoato-κO]copper(II)

In the title compound, [Cu(C9H6N3O2)2(C2H7N)2], the Cu2+ cation is situated on an inversion center and is coordinated by the N atoms of two dimethylamine ligands and the carboxylate O atoms of two 4-(1,2,4-triazol-1-yl)benzoate anions, leading to a slightly distorted square-planar N2O2 coordination environment. In the crystal, intermolecular N—H...N hydrogen bonds between the amine function and the central N atom of the triazole ring lead to the formation of ribbons parallel to [1\overline{1}1]. Weak intermolecular C—H...O hydrogen-bonding interactions are also observed that consolidate the crystal packing.

Crystal structure and Hirshfeld surface analysis of the hydrated 2:1 adduct of piperazine-1,4-diium 3,5-dinitro-2-oxidobenzoate and piperazine

The crystal structure of the adduct piperazine-1,4-diium 3,5-dinitro-2-oxidobenzoate–piperazine–water (2/1/2) shows the existence of a 3,5-dinitrosalicylate dianion (DNSA2−) and a protonated piperazine-1,4-diium cation (PIP2+) along with a piperazine molecule. The formula of the title adduct in the asymmetric unit is 2C4H12N2 2+·2C7H2N2O7 2−·C4H10N2·2H2O with Z = 1. The piperazine ring in the piperazine-1,4-diium cation and in the neutral piperazine molecule adopt chair conformations. All O atoms in the DNSA2− moiety and the water molecule act as hydrogen-bonding acceptors for various intermolecular O—H...O, N—H...O and C—H...O interactions, which stabilize the crystal structure. Various supramolecular architectures formed by the different intermolecular interactions are discussed. The relative contribution of various intermolecular contacts is analysed with the aid of two-dimensional (full and decomposed) fingerprint plots, indicating that H...O/O...H (50.2%) and H...H (36.2%) contacts are the major contributors to the stabilization of the crystal structure.

2,2′-(Ethane-1,2-diyl)bis(4-chlorophenol)

The X-ray structure of the title compound, obtained as a byproduct in a natural product synthesis, has been determined and shows an unusual pattern featuring chains of molecules with both intra- and intermolecular hydrogen bonding of the OH groups.