Absorption and emission spectra of supramolecular complexes (SC) placed in the proximity of a metal nanoparticle (MNP) are computed using a microscopic model. Concerning the absorption of a J-aggregate type SC the treatment predicts a remarkable rearrangement of Frenkel-exciton oscillator strength where all exciton levels become visible. Time and frequency resolved emission spectra display a SC-MNP coupling dependent line-shift, directly reflecting the MNP-induced electron-vibrational level renormalization. (C) 2011 Elsevier B.V. All rights reserved.