Molecular Networks Created by Charge-Assisted Hydrogen Bonding in Carboxylate Salts of a Bis(amidine)

Abstract

Amidines can be protonated by carboxylic acids to give amidinium carboxylates, and the ions can associate by forming multiple charge-assisted hydrogen bonds according to reliable motifs. Extended hydrogen-bonded networks can be constructed by treating suitable bis(amidines) with acids containing multiple carboxyl groups. To further explore the potential of this strategy, we have determined the structures of salts produced by treating 2,2′-bi-2-imidazoline, a cyclic bis(amidine), with oxalic, fumaric, terephthalic, and trimesic acids. The structures of the salts proved to incorporate features resulting predictably from the geometry of the ions and their ability to engage in charge-assisted hydrogen bonds.

Porous Hydrogen-Bonded Organic Frameworks

“…In their work, dicationic bis(amidine) analogues were deliberately selected as hydrogen bonding donors, which was able to complex with anionic species, including phosphonate, sulfonate, or carboxylate compounds. However, single crystals revealed that nearly all resulting crystalline geometries were indeed no porous even though hydrogen bonding interactions were significantly enhanced [ 98 , 99 ]. What’s more, it was found that the charge-assisted hydrogen bonding protocol can be exploited in the fabrication of functionalized supramolecular copolymers [ 100 , 101 ].…”

Self-assembly of the tetrachlorido(oxalato)rhenate(iv) anion with protonated organic cations: X-ray structures and magnetic properties

“…The average C-C and C-N bond length values agree with those found in previously reported salts containing this monoprotonated organic cation. [64][65][66][67][68] In Figure 6 and Table 3). As seen in 1, short Cl···Cl contacts of 3.507(1) Å [Cl(4)···Cl(4a), (a) = -x+2, -y+1, -z+1] and 3.987(1) Å [Cl(1)···Cl(1b), (b) = -x+2, -y+1, -z+2] between [ReCl4(ox)] 2anions direct anionic chains, which grow along the crystallographic c axis (see Fig.…”

Supramolecular polymer gels formed from carboxy-terminated telechelic polybutadiene and polyamidine through amidinium-carboxylate salt bridge

“…Amidines are an important class of compounds that are found throughout nature and have many uses in organic chemistry . Consequently, a number of useful and facile methods have been developed for the preparation of amidines, being able to synthetically incorporate amidine functionality to polymers .…”