Interpenetration in extended three-dimensional (3D) arrays has been investigated by a systematic analysis of the crystallographic structural databases, using an ad hoc version of the program package TOPOS. In this paper we describe the comprehensive results of our investigation of interpenetration in organic hydrogen-bonded 3D arrays from the Cambridge Structural Database. The great interest in the self-assembly of organic molecules into hydrogen-bonded supramolecular arrays has prompted us to investigate these systems at a rather unusual level; that is, beyond the formation of synthons, we have examined the topologies of the resulting networks and looked for their entanglements. Within 3D architectures we have extracted a complete list including 122 different motifs showing the phenomenon of interpenetration (76 unseen by the original authors). These organic networks include species assembled by a single or by different building blocks; they are discussed and classified according to the previously introd...

Interpenetrated Three-Dimensional Networks of Hydrogen-Bonded Organic Species: A Systematic Analysis of the Cambridge Structural Database

Infrared and Raman study of polyaniline Part I. Hydrogen bonding and electronic mobility in emeraldine salts

In this paper, the intermolecular structural study asserted by the vibrational analysis in the stretch frequencies of hydrogen bonds (π⋯H) and dihydrogen bonds (H−δ⋯H+δ) have definitively been revisited by means of calculations carried out by Density Functional Theory (DFT) and topological parameters derived from the classic treatise of the Quantum Theory of Atoms in Molecules (QTAIM). As a matter of fact the π⋯H hydrogen bond is formed between the hydrofluoric acid and the CC bond of the acetylene, but the QTAIM calculations revealed a distortion in this interaction due to the formation of the ternary complex C2H2⋯2(HF). Although the π bonds of ethylene (C2H4), propylene (C2H3(CH3)), and t-butylene (C2H2(CH3)2) are considered proton acceptors, two hydrogen-bond types—π⋯H and C⋯H—can be observed. Over and above the analysis of the π hydrogen bonds, theoretical arguments also were used to discuss the red-shifts in the stretch frequencies of the binary dihydrogen complexes formed by BeH2⋯HX with X = F, Cl, CN, and CCH. Although a vibrational blue-shift in the stretch frequency of the H–C bond of HCF3 due to the formation of the BeH2⋯HCF3 dihydrogen complex was obtained, unmistakable red-shifts were detected in LiH⋯HCF3, MgH2⋯HCF3, and NaH⋯HCF3. Moreover, the alkali–halogen bonds were identified in relation to the formation of the trimolecular systems NaH⋯2(HCF3) and NaH⋯2(HCCl3). At last, theoretical calculations and QTAIM molecular integrations were used to study a novel class of dihydrogen-bonded complexes (mC2H5+ ⋯nMgH2 with m = 1 or 2 and n = 1 or 2) based in the insight that MgH2 can bind with the non-localized hydrogen H+δ of the ethyl cation (C2H5+). In an overview, QTAIM calculations were applied to evaluate the molecular topography, charge density, as well as to interpret the shifted frequencies either to red or blue caused by the formation of the hydrogen bonds and dihydrogen bonds.

Structure, energy, vibrational spectrum, and Bader's analysis of π⋯H hydrogen bonds and H −δ ⋯H +δ dihydrogen bonds

Studies of the crystal structures and formation of a charge-transfer (CT) complex proved that 2,2′-bi-1H-imidazole (H2BIM0) forms a new system concerned with the interplay of proton-transfer (PT) and electron-transfer (or charge-transfer (CT)) interactions. X-Ray crystal analyses of newly isolated species, 2-(2-1H-imidazolyl)-1H-imidazolium (H3BIM+) and 2,2′-bi-1H-imidazolium (H4BIM2+), revealed the formation of strong hydrogen bonds along the side-by-side direction of the molecular plane. CT complexes of H3BIM+ and H4BIM2+ with the 7,7,8,8-tetracyanoquinodimethane derivatives (TCNQs) were synthesized by a method metathesis, and the crystal structure of (H3BIM+)2(TCNQ−)2(TCNQ0) was determined. During CT complex formation, the initial simple protonated states of [H3BIM+] or [H4BIM2+] changed to different ones, for example, [H4BIM2+]x[H3BIM+]1−x, [H3BIM+]x[H2BIM0]1−x, and H2BIM0. According to the protonated states of the H2BIM system, the formal charge of the TCNQs in the CT complexes varies from completely...

Multiplex Proton-Transfer and Electron-Transfer Natures Based on the 2,2′-Bi-1H-imidazole System. II. Crystal Structures and Charge-Transfer Complex Formations

Isotopic effects in NH…N hydrogen bonds

The structure of 4‐aminopyridine hemiperchlorate, C5H6N2⋅1/2HClO4, has been determined from three‐dimensional neutron diffraction data The crystals are monoclinic, space group P21/n, with cell dimensions a=11224 (7) A, b=9325 (6) A, c=16631 (9) A, β=10272 (3) ° and Z=4 The structure was refined to an R(F02) =0102 for 862 reflections with F02≳σF02 The structure consists of perchlorate anions and asymmetrically H‐bridged (NH2Py⋅H⋅⋅PyNH2)+ cations The cations contain a short, asymmetric, nearly linear (N⋅H⋅⋅⋅N)+ hydrogen bond (N⋅⋅⋅N=2698 (8) A, N–H=117 (2) A) The dihedral angle between the planes of the N–H⋅⋅N bridged pyridine rings is 85° The IR spectra are consistent with those predicted for this type of bridge system Strong temperature effects were found to occur both in the stretching frequency region νNH2 and in the low‐frequency broad absorption band below 800 cm−1 The νNH+band shift towards lower frequencies indicating that the bridge becomes shortened which, in turn, results in an incr

L. Sobcyzk

Papers

A strong asymmetric N–H–N hydrogen bond: Neutron diffraction and IR spectroscopic studies of 4‐aminopyridine hemiperchlorate