Charge density study of naphthalene based on X-ray diffraction data at four different temperatures and theoretical calculations

The crystal electron density of naphthalene has been investigated on the basis of highly redundant X-ray diffraction data collected to high resolution at 100, 135, 170, and 205 K and from quantum chemical calculations. An analysis of the X-ray diffraction data showed that for the data collected below 200 K thermal motion can be successfully deconvoluted from the diffraction data. A topological analysis of the resulting static crystal electron-density map revealed that the intramolecular bond critical points have characteristics that are very similar to those of the isolated molecule. There is excellent agreement between the bond critical points cot-responding to the intermolecular interactions in the experimental and theoretical crystal electron densities. The strongest intermolecular interaction is a C-H...pi interaction that causes a change in the electron distribution of the C-H bond.