Y1 may be O or S, and each of Y2 to Y4 may be a chemical bond,
each of X1 and X3 may be C, and each of X2 and X4 may be N,
T1 may be a single bond, a double bond, *—N(R51)—*′, *—B(R51)—*′, *—P(R51)—*′, *—C(R51)(R52)—*′, *—Si(R51)(R52)—*′, *—Ge(R51)(R52)—*′, *—S—*′, *—Se—*′, *—O—*′, *—C(═O)—*′, *—S(═O)—*′, *—S(═O)2—*′, *—C(R51)=*′, *═C(R51)—*′, *—C(R51)═C(R52)—*′, *—C(═S)—*′, or *—C≡C—*′,
T2 may be a single bond, a double bond, *—N(R53)—*′, *—B(R53)—*′, *—P(R53)—*′, *—C(R53)(R54)—*′, *—Si(R53)(R54)—*′, *—Ge(R53)(R54)—*′, *—S—*′, *—Se—*′, *—O—*′, *—C(═O)—*′, *—S(═O)—*′, *—S(═O)2—*′, *—C(R53)=*′, *═C(R53)—*′, *—C(R53)═C(R54)—*′, *—C(═S)—*′, or *—C≡C—*′,
T3 may be a single bond, a double bond, *—N(R55)—*′, *—B(R55)—*′, *—P(R55)—*′, *—C(R55)(R56)—*′, *—Si(R55)(R56)—*′, *—Ge(R55)(R56)—*′, *—S—*′, *—Se—*′, *—O—*′, *—C(═O)—*′, *—S(═O)—*′, *—S(═O)2—*′, *—C(R55)=*′, *═C(R55)—*′, *—C(R55)═C(R56)—*′, *—C(═S)—*′, or *—C≡C—*′,