The intracluster reaction dynamics initiated by femtosecond laser pulses at 263 nm has been studied in nondeuterated and deuterated indole-ammonia clusters. No isotope effect is observed on the sub-ps timescale. On the long-timescale (of few 100 ps), however, the structural reorientation dynamics of the parent as well as the product clusters is prolongated (up to about 3 times) for the deuterated complexes. This effect is interpreted as due to the difference of the torsion modes and due to low energetic barriers between different isomers of both isotopic complexes. (C) 2003 Elsevier Science B.V. All rights reserved.