Crystallization Selectivity of Ribavirin Solution and Amorphous Phase

Crystallization selectivity is an important principle in polymorph control. Ribavirin Form I, Form II, DMSO solvate, and amorphous ribavirin are prepared, and the short-range order similarities between these solid forms and ribavirin aqueous solution and DMSO solution are compared via mid-frequency Raman difference spectra (MFRDS). The crystallization process from amorphous ribavirin to Form I and from solution to amorphous phase is explained. Reasons for the difficulty in preparing the DMSO solvate are proposed. The rationale provided for the crystallization selectivity provides a foundation for the synthesis of metastable phases with a robust and convenient method.

Molybdenum-Mediated Insertion of Ketones into the P-P bond of cyclo-(P5 Ph5 ) and Formation of Trinuclear Molybdenum Complexes

The reaction of cyclopentaphosphine cyclo-(P5 Ph5 ) (1) with ketones (acetone and cyclooctanone) in the presence of [Mo(CO)4 (cod)] (cod=cycloocta-1,5-diene) led to air-stable trinuclear complexes in which the bis-phosphanido ligands (PPh-PPh-PPh-PPh-CMe2 O-PPh)2- (complex 2) and (PPh-PPh-PPh-PPh-C(CH2 )7 O-PPh)2- (complex 3) bridge a Mo(CO)3 -Mo(CO)3 unit. This extends the reaction of 1 with transition metal carbonyl complexes to further substrates and represents the first examples of insertion of carbonyl compounds into the P-P bond of cyclic oligophosphorus compounds. Complexes 2 and 3 have been characterized by 31 P NMR spectroscopy and single crystal X-ray diffraction. Furthermore, the thermal properties of the obtained complexes have been studied by differential scanning calorimetry (DSC) and fast scanning calorimetry (FSC).

Determination of Melting Parameters of Cyclodextrins Using Fast Scanning Calorimetry

The first evidence of native cyclodextrins fusion was registered using fast scanning calorimetry (FSC) with heating rates up to 40,000 K s-1. The endothermal effects, detected at low heating rates, correspond to the decomposition processes. Upon the increase of the heating rate the onset of these effects shifts to higher temperatures, reaching a limiting value at high heating rates. The limiting temperatures were identified as the melting points of α-, β- and γ-cyclodextrins, as the decomposition processes are suppressed at high heating rates. For γ-cyclodextrin the fusion enthalpy was measured. The activation energies of thermal decomposition of cyclodextrins were determined by dependence of the observed thermal effects on heating rates from 4 K min-1 in conventional differential scanning calorimetry to 40,000 K s-1 in FSC. The lower thermal stability and activation energy of decomposition of β-cyclodextrin than for the other two cyclodextrins were found, which may be explained by preliminary phase transition and chemical reaction without mass loss. The obtained values of fusion parameters of cyclodextrins are needed in theoretical models widely used for prediction of solubility and solution rates and in preparation of cyclodextrin inclusion compounds involving heating.

Functionalized resorcin[4]arene-based coordination polymers as heterogeneous catalysts for click reactions

One Cu(i) and two Cd(ii) coordination polymers have been achieved using a 4-mercaptopyridine-functionalized resorcin[4]arene. 1 exhibits predominant efficiency and excellent recyclability for the synthesis of 1,2,3-triazoles and β-OH-1,2,3-triazoles.