RESUMEN
Magnetic, structural and computational data of four complex salts with the same mononuclear high spin octahedral Mn(iii) complex cation are reported. The manifestation of Jahn-Teller-like distortions in the Mn(iii) cation is dependent on the nature of the charge-balancing anion, with small anions yielding a planar elongation and large anions freezing out a preferential axial elongation along one of the amine-Mn-imine directions within that same plane. Modulation of the lattice by changing the charge balancing anion results in mixing of the orbital symmetry due to vibrational perturbation.
RESUMEN
Multi-ionizable compounds, such as dicarboxylic acids, offer the possibility of forming salts of drugs with multiple stoichiometries. Attempts to crystallize ciprofloxacin, a poorly water-soluble, amphoteric molecule with succinic acid (S) resulted in isolation of ciprofloxacin hemisuccinate (1:1) trihydrate (CHS-I) and ciprofloxacin succinate (2:1) tetrahydrate (CS-I). Anhydrous ciprofloxacin hemisuccinate (CHS-II) and anhydrous ciprofloxacin succinate (CS-II) were also obtained. It was also possible to obtain stoichiometrically equivalent amorphous salt forms, CHS-III and CS-III, by spray drying and milling, respectively, of the drug and acid. Anhydrous CHS and CS had melting points at â¼215 and â¼228 °C, while the glass transition temperatures of CHS-III and CS-III were â¼101 and â¼79 °C, respectively. Dynamic solubility studies revealed the metastable nature of CS-I in aqueous media, resulting in a transformation of CS-I to a mix of CHS-I and ciprofloxacin 1:3.7 hydrate, consistent with the phase diagram. CS-III was observed to dissolve noncongruently leading to high and sustainable drug solution concentrations in water at 25 and 37 °C, with the ciprofloxacin concentration of 58.8±1.18 mg/mL after 1 h of the experiment at 37 °C. This work shows that crystalline salts with multiple stoichiometries and amorphous salts have diverse pharmaceutically relevant properties, including molecular, solid state, and solubility characteristics.
Asunto(s)
Ciprofloxacina/química , Sales (Química)/química , Ácido Succínico/química , Rastreo Diferencial de Calorimetría , Cristalografía por Rayos X , Cromatografía de Gases y Espectrometría de Masas , Estructura Molecular , Solubilidad , Espectroscopía Infrarroja por Transformada de Fourier , Termogravimetría , Difracción de Rayos XRESUMEN
Crystal structures of new trinuclear complexes [Ni 3(mu-OAc F) 4(mu-AA) 2(tmen) 2], [Ni 3(mu-OAc F) 4(mu-BA) 2(tmen) 2], and [Co 3(mu-OAc F) 4(mu-BA) 2(tmen) 2] have been determined (OAc F = CF 3COO (-), AA = acetohydroxamate anion, BA = benzohydroxamate anion, tmen = N, N, N', N'-tetramethylethylenediamine). In each structure, the metal ions have distorted octahedral coordination and are triply bridged by one hydroxamate and two trifluoroacetate bridges. Magnetic properties of these compounds and of relative [Co 3(mu-OAc F) 4(mu-AA) 2(tmen) 2] were studied by susceptibility and magnetization measurements. It was shown that for nickel trimers the intramolecular magnetic coupling is weak ferromagnetic in the case of the complex with the AA group, and there is nearly no coupling in the case with BA group. Rather large zero field splitting was obtained for the distorted octahedral environments of the terminal nickel ions. The cobalt trimers were additionally studied by magnetic circular dichroism (MCD) measurements. The exchange interaction of the cobalt complexes is antiferromagnetic.