Crystallographic study and molecular orbital calculations of thiadiazole derivatives. 1. Phenanthro[9,10-c]-1,2,5-thiadiazole 1,1-dioxide and acenaphtho[1,2-c]-1,2,5-thiadiazole 1,1-dioxide

Single-crystal X-ray diffraction studies are reported for phenanthro[9,10-c ]-1,2,5-thiadiazole 1,1-dioxide (I) and acenaphtho[1,2-c]-1,2,5-thiadiazole 1,1-dioxide (II), Ab initio molecular orbital (MO) calculations on the ele ctronic structure, conformation and reactivity of I and II an also reported and compared with the X-ray results. A charge sensitivity analysis of the studied molecules has been performed by resorting to density functional the ory (DFT), obtaining several sensitivity coefficients such as the molecular energy, net atomic charges, global and local hardness, global and local so ftness and Fukui functions. With these results and the analysis of the dipo le moments and the total electron density maps, several conclusions have be en inferred about the preferred sites of chemical reaction of the studied c ompounds. (C) 2001 Elsevier Science B.V. All rights reserved.