Luminol, one of the most popular electrochemiluminescence systems used in forensic chemistry, proved to be a suitable system to study the importance of cooperativity in hydrogen-bond chains. The computational pairwise approach PiMM was applied to the system and a thorough band assignment was accomplished. Hydrogen-bond and hydrogen-bond cooperativity effects were assessed through a confrontation of energy, geometry and wavenumber changes from monomer and dimer on one hand and dimer and “full-cluster” trimer on the other. For the first time the PiMM method was also used to successfully predict changes in band relative intensities. Crown Copyright (C) 2012 Published by Elsevier B.V. All rights reserved.