  The new layered manganese oxychalcogenides (LaO)$_2$Mn$_2$Se$_2$O and
(BaF)$_2$Mn$_2$Se$_2$O, isostructural to (LaO)$_2$Fe$_2$Se$_2$O, were
synthesized by using solid state reaction. The single crystals of former
compound were also successfully grown by using high temperature fusion method.
The polycrytalline samples showed the insulating behavior, with the activation
energy gaps of about 278 meV and 416 meV for (LaO)$_2$Mn$_2$Se$_2$O and
(BaF)$_2$Mn$_2$Se$_2$O, respectively. The magnetic susceptibility indicated an
antiferromagnetic (AFM) transition at around 160K and strong anisotropic
magnetic properties below T$_N$ for the former compound, which suggests a
long-range canted AFM ordering. A broad maximum of the susceptibility can be
observed for the two compound at high temperatures, say 360 K and 210 K
respectively, suggesting that strong magnetic correlation gives rise to
low-dimensional AFM or short-range ordering at high temperatures in these rare
transition metal oxychalcogenides with a frustrated AFM checkerboard spin
lattice.
