A new class of halogen bonds of the type X = Hal center dot center dot center dot Y has been investigated by using the density functional theory calculations. The strength of this new class of halogen bonds is in the range of 90-120 kcal/mol, which is greatly larger than that of the conventional halogen bond of the type X-Hal center dot center dot center dot Y. The geometry of this new class of halogen bonds is not determined by the halogen's positive sigma-hole. Natural bond orbital analysis shows it is the n -> pi* interaction that determines the geometry of this new class of halogen bonds. Experimental results are in good agreement with the theoretical predictions. (c) 2012 Elsevier B.V. All rights reserved.