matrix = SparseArray[
             {{i_, i_} -> Eo, {i_, j_} /;
               Abs[i - j] == 1 -> -t, {i_, j_} /;
               i == 1 && j == NA -> -t, {i_, j_} /;
               j == 1 && i == NA -> -t}, {NA, NA}];

MatrixForm[matrix];