Stefano Luca Giaffreda

Solvent effect in a “solvent free” reaction

Vapour digestion of a mixture of solid [Fe(η5-C5H4–C5H4N)2] and solid pimelic acid HOOC(CH2)5COOH in the presence of solvent vapours generates co-crystals of different stoichiometry depending on the protic or aprotic nature of the solvent. The nature of the products has been ascertained by a combined use of SSNMR and X-ray diffraction.

Making crystals from crystals: three solvent-free routes to the hydrogen bonded co-crystal between 1,1′-di-pyridyl-ferrocene and anthranilic acid

The organometallic complex [Fe(η5-C5H4–C5H4N)2] has been reacted with the anthranilic acid (C6H4)NH2COOH to generate the hydrogen bonded supramolecular macrocycle {[Fe(η5-C5H4–C5H4N)2] [(C6H4)NH2COOH]}2. The product has been fully characterized by means of X-ray powder diffraction, 13C and 15N solid-state NMR and single crystal X-ray diffraction. It has been shown that the same product can be obtained, quantitatively, by three different processes, namely kneading, i.e. solid-state mixing in the presence of a catalytic amount of MeOH, wet compression, i.e. pressure without mixing in the presence of MeOH, and vapour digestion, i.e. a mixture of the solid reactants is left in an atmosphere of MeOH vapours. The product can also be obtained via thermally induced reaction of a mixture of the two solid reactants, while no reaction is observed by dry mixing and dry compression. These experiments provide new insights into the factors controlling the process suggesting that the reaction requires the intermediacy of a catalytic amount of solvent or melting of one reactant to take place.

Mechanochemical and solution preparation of the coordination polymers Ag[N(CH2CH2)3N]2[CH3COO]·5H2O and Zn[N(CH2CH2)3N]Cl2

The coordination polymer Ag[N(CH2CH2)3N]2[CH3COO]·5H2O has been obtained by co-grinding in the solid state and in the air of a stoichiometric amount of silver acetate and of [N(CH2CH2)3N]. Single crystals suitable for X-ray diffraction have been obtained from a water–methanol solution and used to compare calculated and experimental X-ray powder diffractograms. When ZnCl2 is used instead of AgCH3COO in the equimolar reaction with [N(CH2CH2)3N], the solution and solid-state treatments afford different products. Single crystals of the Zn-based coordination polymer Zn[N(CH2CH2)3N]Cl2 have been obtained by layering a solution of ZnCl2 in methanol over a solution of [N(CH2CH2)3N] in CH2Cl2. The product of the co-grinding, identified only on the basis of X-ray powder diffraction, converts, on prolonged grinding, into the crystalline material obtained from the reaction in solution, namely anhydrous Zn[N(CH2CH2)3N]Cl2.

Mechanochemical assembly of hybrid organic–organometallic materials. Solid–solid reactions of 1,1′-di-pyridyl-ferrocene with organic acids

Manual kneading of the organometallic complex [Fe(η5-C5H4-C5H4N)2] with solid fumaric, succinic, tridecanedioic, terephthalic, trimesic and thiophene-2,5-dicarboxylic acids generated the corresponding adducts, whether salts or molecular complexes: [Fe(η5-C5H4-C5H4N)(η5-C5H4-C5H4NH)][HOOC(CH)2COO]·CH3OH, [Fe(η5-C5H4-C5H4N)(η5-C5H4-C5H4NH)][HOOC(CH2)2COO]·[HOOC(CH2)2COOH], [Fe(η5-C5H4-C5H4N)2]·[HOOC(CH2)11COOH]·2CH3OH, [Fe(η5-C5H4-C5H4N)2]·[HOOC(C6H4)COOH], [Fe(η5-C5H4-C5H4NH)2][C6H3(COOH)2(COO)]2 and 3{[Fe(η5-C5H4-C5H4N)(η5-C5H4-C5H4NH)][HOOC(SC4H2)COO]}·[Fe(η5-C5H4-C5H4N)2]·2[HOOC(SC4H2)COOH]. Direct reaction in solution yielded the same compounds, which were characterized by single crystal X-ray diffraction, thus allowing comparison of observed and calculated powder diffraction patterns. Kneading of the organometallic complex with maleic acid, on the other hand, yielded a different product from the one obtained via reaction in solution, which was characterized by single crystal X-ray diffraction as the salt [Fe(η5-C5H4-C5H4NH)2][HOOC(CH)2COO]2. The solid–solid processes described herein imply molecular diffusion through the lattice and breaking and reassembling of hydrogen bonded networks with or without proton transfer from acid to base.

Crystal forms of the hydrogen oxalate salt of o-desmethylvenlafaxine.

To prepare new crystalline forms of the antidepressant o‐desmethylvenlafaxine salt as potential new commercial forms and evaluate their physicochemical properties, in particular the dissolution rate.