A new Shiff base molecule N.N'-bis(2-hydroxy-5-methylbenzylidene)-1,2-ethanediamine (1) has been successfully encapsulated in the nanoporous channels of MCM-41 host. The bathochromic shifts of the 0-0 transitions have been correlated with the reduction of the HOMO-LUMO band gap accompanying by the increased energies of the frontier orbitals. This trend indicates that the molecular orbital confinement of organic molecules is indeed realized in larger cavities, such as nanoporous MCM-41. The variations in the 0-0 transitions observed here have also been confirmed by theoretical calculations. (C) 2002 Elsevier Science B.V. All rights reserved.