Effect of electron donating substituents on supramolecular structure of salts having phenylphosphonic acid and pyrazoles

Abstract

The reactions of phenylphosphonic acid [(OH) 2 POC 6 H 5 ] (PPA) with a variety of ditopic pyrazoles Pz R1,R2 H (where R 1 = R 2 = H for 1, R 1 = R 2 = Me for 2, R 1 = Ph, R 2 = Me for 3 and R 1 = R 2 = iPr for 4) produce salts 1-4. Due to the presence of different substituents on pyrazole, each salt shows different structure. This study demonstrates that the presence of different substituents on the pyrazole moieties provides sufficient non-covalent interactions which are responsible for the different supramolecular structures adopted. Theoretical studies reveal that the proton affinity increases on the nitrogen having lone pair of electron with the increase of electron density on pyrazole ring but the orientation remains the same in both the solid and gaseous phase.

A supramolecular approach towards the construction of molecular salts using phosphonic acid and pyrazole

“…The implementation of a concerted and methodical approach has led researchers to understand the intermolecular interactions between two components 20 and utilize them to tailor new desired solids. Although the exploitation of structural interaction patterns of phosphonic acid 8d,21 and pyrazole 9 have been performed individually, the structural chemistry of both these components via the synthon approach has not been reported yet. In this regard, we have applied the supramolecular synthon approach to the construction of six molecular salts entailing the bent core molecule, MBPz and a variety of phosphonic acids, viz., aliphatic phosphonic acid (H 2 tBPA), aromatic phosphonic acid (H 2 PPA), homo/heterosubstituted phosphonic acid (H 2 PAA, H 2 PPRA, H 4 DPA and H 4 EA) (Scheme 1).…”

“…This journal is © The Royal Society of Chemistry 2014 phosphonic acid is deprotonated; hence in the asymmetric unit, all MBpz are doubly protonated and all phosphonic acid molecules are singly deprotonated. The crystal structure study of 2 exemplifies an intriguing stacked arrangement of a pair of infinite 2D undulated sheets; thereby both sheets of the pair are further composed of alternate catemeric arrangements of two symmetry independent charge assisted heterosynthons i.e., heterotrimer VI, R 2 3 (9) and heterotetramer (extended trimer) VIII, R 3 4 (11) as shown in Fig. 5a…”

“…8 Among the N-heterocyclic ligands, phosphonic acid has been exploited with pyridyl supported bases however, very few reports have been found with pyrazole analogues. 9 Hence, we are interested in exploring the system of substituted phosphonic acids (possessing different hydrogen bonding moieties) and flexible bent bispyrazole i.e., methylenebis(3,5dimethylpyrazole) (MBPz) that may assist to design solid architectures with new persistent supramolecular synthons by applying the basic rationale of crystal engineering. Although, the pyrazole has already been exploited solely 10 and as a coformer 11 resulting in various robust supramolecular synthons, nonetheless, there is no report on synthons built by phosphonate and pyrazole.…”

Anion directed supramolecular architecture of benzimidazole-based receptor

“…(DHA) [31,32]. Along with dimerization, head-to-tail hydrogen bonding also exists in the same system (O18-H18Á Á ÁO10, 1.707(3) Å) (Fig.…”

Pentafluorophenylphosphonic Acid as a New Building Block for Molecular Crystal Fabrication

“…Literature melting point: 141-142 °C 56,57. The 1 H,13 C{19 F},19 F, and 31 P NMR data of 4 in DMSO-d6 can be found in ref.18 Equimolar amounts of 4 and glycine were dissolved in water. The resulting solution was allowed to evaporate to dryness, giving colorless crystals.…”