The crucial effect on relaxing the molecular geometry in the presence of central metal is found to be significantly larger by means of the bond length modification and vibration frequency analysis between ground state and the lowest excited state for the spiro-linked Zn(PyIm)(2) (PyIm = 2(2'-pyridine)-imidazole) complex. The bond resonance intensity of harmonic vibration mode for the excited singlet state (SI) has affirmed central metal directly affect to a certain extent the electronic structure, resuming to pronounced change photoelectric properties, even though it is vanishingly small contribution to frontier molecular orbitals. The consentaneous conclusions can be drawn from other analogous complexes. (c) 2005 Elsevier B.V. All rights reserved.