Gaëlle Ramon

Methanol mediated crystal transformations in a solvatochromic metal organic framework constructed from Co(II) and 4-(4-pyridyl) benzoate

The structural transformations of compound 1 {[Co(44pba)2]4·(DMF)3·(EtOH)0.25·(H2O)4}n [44pba = 4-(4-pyridyl) benzoate] were followed during the exchange of DMF and ethanol molecules by methanol at room temperature. The new phases obtained 2 {[Co(44pba)2]·(MeOH)2.5·(H2O)}n, 3 {[Co(44pba)2(MeOH)2]2·(MeOH)2.5·(H2O)2}n and 4 {[Co(44pba)2(MeOH)2]·(MeOH)0.5·(H2O)0.5}n were studied using differential scanning calorimetry, thermogravimetric analysis and X-ray diffraction methods. The final phase 4 reverts back to 1 upon soaking 4 in a dry DMF–ethanol mixture as evidenced by the powder diffraction data and infrared spectra.

Structures of benzoic acids with substituted pyridines and quinolines: salt versus co-crystal formation

A series of five substituted benzoic acids with 10 substituted pyridines and quinolines have been crystallized so that their ΔpKa, defined as pKa base–pKa acid, varied from −1.14 to +4.16. This spans the ‘uncertainty’ region for the formation of salt versus co-crystals. Although most of our results confirmed that structure formation of co-crystal versus salt parts at ΔpKa ≈ 2, we report here a structure that does not follow the general rule and serves as a cautionary tale.

The role of C–H⋯π interactions in modulating the breathing amplitude of a 2D square lattice net: alcohol sorption studies

A breathing 2D net 1 {[Zn(34pba)2]·DMF}n assembled from mononuclear zinc(II) centres and 3-(4-pyridyl) benzoate (34pba) ditopic linker is presented. 1 undergoes a displacive phase transition to give 1d, [Zn(34pba)2]n on evacuation of DMF. This is accompanied by a 37% decrease in solvent accessible void volume. Exposure of 1d to alcohol vapours shows that the saturation uptake increases with an increase in number of carbon atoms in the alcohol. The enhanced uptake of n-butanol and n-propanol is attributed to the long alkyl chain which enhances C–H⋯π interactions with the hydrophobic pyridyl and phenyl rings of the network. These interactions trigger the breathing motion of the 2D network and allow for the entry of n-propanol and n-butanol into the channels. Methanol and ethanol are unable to initiate the dynamic motion of the framework which increases the channel volume. In consequence, these solvents are absorbed to a lesser extent. Vapour phase competition studies show that the activated material is able to absorb n-butanol in the presence of a high vapour pressure of methanol. The selectivity observed may be based on factors that allow the metal organic framework inclusion compound to assume the most relaxed conformation.

Alcohol responsive 2D coordination network of 3-(4-pyridyl)benzoate and Zinc(II)

Abstract The solvothermal reaction of 3-(4-pyridyl)benzoic acid and zinc nitrate yielded a 2D network with an sql topology. Both elemental analysis and single crystal X-ray diffraction studies confirmed the formula of the compound as {[Zn(34pba)2] · (0.5 DMF) · (0.5 H2O)}n (1). At room temperature, the desolvated phase of 1, 1d, absorbs methanol, ethanol, 1-propanol and 1-butanol but not water vapour.

Inclusion Compounds from a Host Mixture: A Cautionary Tale

The inclusion properties of a dibenzocycloheptenol host with a variety of volatile guests have been analysed. The packing and intermolecular interactions of the inclusion compounds have been examined. Unexpected structures arising from impurities in the host, termed the ‘host mixture’, have been elucidated.

Inclusion compounds from a decomposing host: a cautionary tale

C283 were synthesized and their crystal structures were determined. Unexpectedly all such molecules form interlocked Piedfort-associates. Thus the two superposed molecules of a Piedfort-unit serve as supramolecular synthon[1]. We can also clearly see intramolecular halogen-halogen interactions which are developed at the external surface of the Piedfort-pair. The effect of the halogen atom on the Piedfort stacking distances and the dimensions of the halogen synthon will be described in details. The authors acknowledge Hungarian Scientific Research Fund (OTKA grants T042642).