Picrate salts with bipyridine derivatives: Intra and intermolecular aspects

Abstract

Here, we present the preparation and characterization of two novel picrate salts. Compound 1 (DPK-PA) crystallizes in the triclinic system and centrosymmetric space group P\(\stackrel{-}{1}\), with unit cell parameters a = 9.378(17) Å, b = 9.790(15) Å, c = 10.141(16) Å, α = 99.63(7)°, β = 99.09(8)° and γ = 102.55(8)°, while the compound 2 (BBBPY-PA) crystallizes in the non-centrosymmetric P212121 space group, orthorhombic unit cell parameters a = 6.3902(6) Å, b = 23.416(3) Å and c = 16.7320(18) Å. Both crystal structures present an ion-pair in the asymmetric unit, one picrate anion, and one bipyridine derivative. In the compound 1 structure, the molecule of DPK presents one intramolecular N1-H…N Hbond that contributes to stabilizing the planar conformation of DPK. The absence of intramolecular Hbonding in compound 2 can be explained by the steric hindrance of the tert-butyl group. For 1 and 2, the crystal packing is stabilized N-H…O strong hydrogen bonding interactions, which could be identified by the Hirshfield Surface analysis and fingerprint plots. The compounds were also studied by UV-Vis and infrared analyses, which may support the statement of the formation of new material. Finally, as an attempt to obtain a molecular system to act as a chemical sensor, we studied the fluorescence of both compounds, in solution and in solid state, however, no fluorescence was observed.