Quasilinear molecule par excellence, SrCl₂: Structure from high-temperature gas-phase electron diffraction and quantum-chemical calculations - Computed structures of SrCl₂·argon complexes

The molecular geometry of strontium dichloride has been determined by high-temperature electron diffraction (ED) and computational techniques. The computation at the MP2 level of theory yields a shallow bending potential with a barrier of about 0.1 kcal mol^-1 at the linear configuration. The experimentally determined thermal average Sr-Cl bond length. r_g, is 2.625 ± 0.010 Å and the bond angle. <_a, is 142.4 ± 4.0°. There is excellent agreement between the equilibrium bond lengths estimated from the experimental data. 2.607 ± 0.013 Å, and computed at different levels of theory and basis sets, 2.605 ± 0.006 Å. Based on anharmonic analyses of the symmetric and asymmetric stretching as well as the bending motions of the molecule, we estimated the thermal average structure from the computa tion for the temperature of the ED experiment. In order to emulate the effect of the matrix environment on the measured vibrational frequencies, a series of complexes with argon atoms. SrCl₂·Ar_n (n = 1-7), with different geometrical arrangements were calculated. The complexes with six or seven argon atoms approximate the interaction best and the computed frequencies of these molecules are closer to the experimental ones than those computed for the free SrCl ₂ molecule.