in this article, theoretical studies on the selective complexation of the halide ions (f¯, cl¯ and br¯) and ion pairs (na+f¯, na+cl¯ and na+br¯) with the cyclic nano-hexapeptide (cp) composed of l-proline have been performed in the gas phase. in order to calculate the dispersion interaction energies of the cp and ions, dft-d3 calculations at the m05-2x-d3/6-31g(d) level was employed. based on t...

A simple, sensitive and rapid spectrophotometric method was developed and validated for the determination of two skeletal muscle relaxants namely, tizanidine hydrochloride (I) and orphenadrine citrate (II) in pharmaceutical formulations. The proposed method is based on the formation of a binary complex between the studied drugs and eosin Y in aqueous buffered medium (pH 3.5). Under the optimum ...

A sensitive and rapid extractive spectrophotometer method has been developed for the assay of carvedilol in pharmaceutical formulations. The method is based on the formation of a chloroform soluble ion-pair complex between carvedilol and bromocresol green in an acidic medium. The complex shows absorption maximum at 415 nm and the system obeys Beer’s law in the concentration range of 5-25 μg/ml....

complexes of benzo-15-crown-5 macrocycle with li+ and cs+ ions were investigated by 7li and 133cs nmr in a number of nonoqueous solutions. the resulting 1:1 complex with li+ ion was found to be much more stable than that with cs+ ion. with the exception of pyridine solutions the stabilities of the complexes varied inversely with the gutmann donor number of the solvents. some indirect evidence f...

Electron transfer in collisions between Rydberg atoms and targets that attach free low-energy electrons can lead to the formation of heavy-Rydberg ion-pair states comprising a positive-negative ion pair that orbit each other at large separations weakly bound by their mutual electrostatic attraction. It is shown that measurements of the velocity distribution of the ion-pair states produced in su...