Temperature (T)-dependent emission from [{Mo6X8}(n-C(3)F(7)C00)6](2-) (X = Cl (1), Br (2), and I (3)) in optically transparent polyethylene glycol dimethacrylate matrices were studied in 3 K < T < 300 K to elucidate the spectroscopic and photophysical properties of the clusters, in special reference to zero-magnetic-field splitting (zfs) in the lowest-energy excited triplet states (T-1) of the clusters. The cluster complexes 1 and 2 showed the T-dependent emission characteristics similar to those of [{Mo6C18}Cl-6](2-), while 3 exhibited emission properties different completely from those of 1 and 2. Such T -dependent emission characteristics of 1, 2, and 3 were explained successfully by the excited triplet state spin-sublevel (phi(n,n) = 1-4) model. The zfs energies between the lowest -energy (phi(1)) and highest-energy (phi(4)) spin sublevels, Delta E-14, resulted by the first-order spin orbit coupling, were evaluated to be 650, 720, and 1000 cm(-1) for 1, 2, and 3, respectively. The emission spectra of 1, 2, and 3 in CH3CN at 298 K were reproduced very well by the Delta E-14 values and the population percentages of On at 300 K. We also report that the Delta E-14 values of the clusters correlate linearly with the fourth power of the atomic number (Z) of X: Delta E-14 alpha{Z(X)}(4).