Histidine and deuterium-labelled histidine by asymmetric catalytic reduction and assignment of the absolute stereochemistry by neutron diffraction

Novel three-dimensional coordination polymer of 2-(1,3,5-triaza-7-phosphoniatricyclo[3.3.1.13,7]decan-7-yl)ethanoic acid with silver(I) tetrafluoroborate

An AgI-based coordination polymer (CP), namely, poly[[[μ3-2-(1,3,5-triaza-7-phosphoniatricyclo[3.3.1.13,7]decan-7-yl)ethanoate-κ4 N:N′:O,O′]silver(I)] tetrafluoroborate], {[Ag(C9H16N3O2P)]BF4} n , was synthesized in an aqueous solution of zwitterionic 2-(1,3,5-triaza-7-phosphoniatricyclo[3.3.1.13,7]decan-7-yl)ethanoate (L) and AgBF4 with exclusion of light at room temperature. The colourless and light-insensitive CP crystallized in the monoclinic space group Cc. The asymmetric unit consists of an AgI cation, the zwitterionic L ligand and a BF4 − counter-ion. Each AgI ion is coordinated by two carboxylate oxygen atoms in a chelating coordination mode, as well as one of the nitrogen atoms of two neighbouring L ligands. The crystal structure of the CP was classified as a unique three-dimensional arrangement. The CP was also characterized in aqueous solutions by multinuclear NMR and HRMS spectroscopies and elemental analysis.

Hydrogen Bonds with BF4− Anion as a Proton Acceptor

The BF4− anion is characterised by weak Lewis base properties; it is usually classified as a “non-coordinating anion”. The searches through the Cambridge Structural Database (CSD) were performed and it was found that the BF4− anion often occurs in crystal structures and it is involved in numerous intermolecular interactions; hydrogen bonds are the majority of them. The hydrogen bonds involving the BF4− anion as a proton acceptor are closer to linearity with the increase of the strength of interaction that is in line with the tendency known for other hydrogen bonds. However, even for short contacts between the proton and the Lewis base centre, slight deviations from linearity occur. The MP2/aug-cc-pVTZ calculations on the BF4−…HCN complex and on the BF4−…(HCN)4 cluster were also carried out to characterise corresponding C-H…F hydrogen bonds; such interactions often occur in crystal structures.