Possible eight spin structures for four spin-site systems: (abcd) denotes (SQ2,Ru2,Ru1,SQ1) (2bb) or (SQ2,O1,Ru1,SQ1) (2a(+)ee) in accord with the notation for CaMn4O5 cluster CaMna(4)Mnb(3)Mnc(2)Mnd(1) (3). The same spin Hamiltonian model has been derived to elucidate similarity between artificial (2bb) and native (3) catalysts for water splitting reaction.