Millisecond transient luminescence and absorption spectra of wide gap MX-chain compound, [Pd(en)(2)][Pt(en)(2)Br-2](ClO4)(4), have been measured. A delayed luminescence band has been found at 1.55 eV. The time evolution of the intensity of the luminescence is proportional to the first derivative of the intensity of the photoinduced polaron absorption. The delayed luminescence band is considered to be caused by the radiative recombination of the self-trapped excitons which are generated in the annihilation processes of the polarons. (C) 2001 Elsevier Science B.V. All rights reserved.