Scaling of computed cyano-stretching frequencies and IR intensities of nitriles, their anions, and radicals.

Specialized scale factors and scaling equations have been determined for both cyano stretching vibrational frequencies and IR intensities of nitrile molecules, anions and radicals (269 data points in all). Various double and triple-zeta basis sets, viz. 3-21G, 6-31G, 6-311G, 6-31G*, 6-311G*, 6-31+G, 6-311+G, 6-31G**, 6-31+G*, 6-311+G*, 6-31++G**, 6-311++G**, and aug-cc-pVDZ at the B3LYP and HF theory levels have been applied. Besides the theory and basis set, the mean deviations between scaled computed and experimental spectroscopic features have been found to depend also on the series studied: frequencies or intensities, and molecules, anions, or radicals. Use of scaling equations instead of scale factors has given slightly worse results for frequencies, but essentially better ones for infrared intensities.