Crystal structures and vibrational spectra of L-argininium(2+) bis(tetrafluoroborate) and L-argininium(2+) bis(perchlorate)

In the present work crystal structures of (L-ArgH₂)(BF₄)₂ (I) and (L-ArgH₂)(ClO₄)₂ (II) isostructural salts have been determined. They crystallize in triclinic system with space group P1 and Z = 1. Structure features of the (I) and (II) were compared with respective data of previously known (L-ArgH)(BF₄) and (L-ArgH)(ClO₄) salts with singly charged L-argininium(+) cation. Infrared and Raman spectra of the (I) and (II) are compared with spectra of (L-ArgH)(BF₄) and (L-ArgH)(ClO₄) salts. The presence of cation and anions and hydrogen bonds between them are reflected in the IR and Raman spectra. The crystals (I) and (II) exhibit second harmonic generation activity.

Molecular mechanics calculations of 10-vertex boron cage compounds

The model proposed earlier for molecular mechanics calculations of 7- and 12-vertex boranes, carboranes, and metallocarboranes has been extended to the case of 10-vertex borane cage compounds. To use the MM3 program with the standard connectivity file, and to avoid program alterations, the 10-vertex cages of the molecules were presented as a superposition of four formally independent fragments. Interactions between the fragments were described with a Hill-like potential, with the parameters adjusted for valence interactions. Standard values for the bond lengths and bond angles in the 10-vertex boron cage have been found by statistical analysis of X-ray data on borane cage compounds stored in the Cambridge Structural Database. Several substituted neutral molecules and anions have been considered, and good agreement of the calculated and experimental data has been obtained. Using the approach developed, the unknown structure of the [mu-B20H16O(CH2)4O(CH2)2CH(CH3)2]3- ion has been calculated.