The steady-state and time-resolved photophysical properties and some molecular orbital calculation results of a dimeric indium phthalocyanine complex with an indium-indium bond, i.e., [tBu(4)PcIn](2)center dot 2tmed, have been described. The results regarding triplet excited state lifetimes can be ascribed to strong intramolecular interactions existing only in the excited state of this dimer because no significant difference in the absorption spectra of the tBu(4)PclnCl monomer and the [tBu(4)PcIn](2)center dot 2tmed dimer is observed, suggesting that no ground-state interaction can be assessed. The deactivation processes of the excited singlet state of [tBu(4)PcIn](2)center dot 2tmed are apparently faster than that of mu-oxo-bridged PcIn dimer [tBu(4)PcIn](2)O. Molecular orbital calculation on the PcIn dimer shows no node between two indium atoms was found in the HOMO - 2 of the Pcln-InPc dimer, suggesting that bonding electrons distribute between two indium atoms. (c) 2005 Elsevier B.V. All rights reserved.