Topological analysis of the experimental electron density of diisocyanomethane at 115 K.

Abstract

The structure and charge density of diisocyanomethane, derived from low-temperature X-ray diffraction data and by ab initio calculations are reported. Different refinement models are tested to judge the physical sign ifi-cance of the density parametrization.The experimental distances of the formal triple bonds are significantly shorter than those obtained by energy optimization. In terms of topological indice s the former method gives a higher bond order than the latter one, even if the calculation is performed at the experimental geometry, indicating that crystal field effects may not be negligible when the results are compared. These effects, although caused by weak close contacts, can directly be revealed by comparing the electrostatic potential extracted from the diffraction data with that derived from the wave function of the isolated molecule.