Heterocyclic compound and organic light-emitting device including the same

An organic light-emitting device comprising:

• a first electrode;
• a second electrode facing the first electrode;
• and
• an organic layer between the first electrode and the second electrode, the organic layer comprising an emission layer,
• wherein the emission layer comprises a mixture of a first compound represented by Formula 1, and a third compound represented by Formula 401,
• the first compound is a delayed fluorescent dopant, and
• the first compound satisfies Equation 1:
• |ED, S1−ED, T1|≤0.3 eV, Equation 1
• wherein, in Equation 1,
• ED, S1 is a singlet energy level (eV) of the first compound, and
• ED, T1 is a triplet energy level (eV) of the first compound,
• wherein, in Formulae 1, 2-1, 2-2, 3-1, and 3-2,
• X1 is O or S,
• Ar1 and Ar2 are each independently a substituted or unsubstituted C5-C60 carbocyclic group or a substituted or unsubstituted C2-C60 heterocyclic group,
• a1 and a2 are each independently an integer from 0 to 3,
• b1 and b2 are each independently 0 or 1,
• a1, a2, b1, and b2 satisfy a1+b1≥1 and a2+b2≥1,
• R1 and R2 are each independently a group represented by Formula 2-1,
• R3 is a group represented by Formula 2-2,
• A1 to A4 are each independently selected from a benzene group, a naphthalene group, a phenanthrene group, a fluoranthene group, a triphenylene group, a pyrene group, a chrysene group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, and a tetrazine group,
• A5 to A8 are each independently selected from a benzene group, a naphthalene group, a phenanthrene group, a fluoranthene group, a triphenylene group, a pyrene group, a chrysene group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, and a tetrazine group,
• Y1 is a single bond, O, S, SO2, N(R19), C(R19)(R20), Si(R19)(R20), S(═O)(R19), S(═O)2(R19), or P(═O)(R19),
• Y2 is a single bond, O, S, SO2, N(R19), C(R19)(R20), Si(R19)(R20), S(═O)(R19), S(═O)2(R19), or P(═O)(R19),
• Y3 is a single bond, O, S, SO2, N(R19), C(R19)(R20), Si(R19)(R20), S(═O)(R19), S(═O)2(R19), or P(═O)(R19),
• Y4 is a single bond, O, S, SO2, N(R19), C(R19)(R20), Si(R19)(R20), S(═O)(R19), S(═O)2(R19), or P(═O)(R19),
• Y5 is a single bond, O, S, SO2, N(R19), C(R19)(R20), Si(R19)(R20), S(═O)(R19), S(═O)2(R19), or P(═O)(R19),
• wherein (i) when Y2 is a single bond, S, or O, a group represented by Formula 2-1 and a group represented by Formula 2-2 are different from each other, and
• (ii) when —(Ar1)a1—(R1)b1 and —(Ar2)a2—(R2)b2 each represent a phenyl group, either Y2 is S(═O)(R19) or S(═O)2(R19), or at least one of R13 and R14 is selected from a group represented by Formula 3-1 and a group represented by Formula 3-2,
• R11 to R14 are each independently selected from a group represented by Formula 3-1, a group represented by Formula 3-2, hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a substituted or unsubstituted C1-C60 alkyl group, a substituted or unsubstituted C2-C60 alkenyl group, a substituted or unsubstituted C2-C60 alkynyl group, a substituted or unsubstituted C1-C60 alkoxy group, a substituted or unsubstituted C3-C10 cycloalkyl group, a substituted or unsubstituted C1-C10 heterocycloalkyl group, a substituted or unsubstituted C3-C10 cycloalkenyl group, a substituted or unsubstituted C1-C10 heterocycloalkenyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C6-C60 aryloxy group, a substituted or unsubstituted C6-C60 arylthio group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —S(═O)(Q1), and —P(═O)(Q1)(Q2),
• wherein two or more R11(s) are optionally linked to form a substituted or unsubstituted C5-C60 carbocyclic group or a substituted or unsubstituted C2-C60 heterocyclic group, two or more R12(s) are optionally linked to form a substituted or unsubstituted C5-C60 carbocyclic group or a substituted or unsubstituted C2-C60 heterocyclic group, two or more R13(s) are optionally linked to form a substituted or unsubstituted C5-C60 carbocyclic group or a substituted or unsubstituted C2-C60 heterocyclic group, and two or more R14(s) are optionally linked to form a substituted or unsubstituted C5-C60 carbocyclic group or a substituted or unsubstituted C2-C60 heterocyclic group,
• b11 to b14 are each independently an integer from 1 to 8,
• when X1 is O, at least one of R13 and R14 is a group represented by Formula 3-1 or a group represented by Formula 3-2, provided that Y2 and Y3 are not both a single bond at the same time, and Y2 and Y4 or Y2 and Y5 are not both a single bond at the same time,
• R15 to R20 are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a substituted or unsubstituted C1-C60 alkyl group, a substituted or unsubstituted C2-C60 alkenyl group, a substituted or unsubstituted C2-C60 alkynyl group, a substituted or unsubstituted C1-C60 alkoxy group, a substituted or unsubstituted C3-C10 cycloalkyl group, a substituted or unsubstituted C1-C10 heterocycloalkyl group, a substituted or unsubstituted C3-C10 cycloalkenyl group, a substituted or unsubstituted C1-C10 heterocycloalkenyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C6-C60 aryloxy group, a substituted or unsubstituted C6-C60 arylthio group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic, —S(═O)(Q1), and —P(═O)(Q1)(Q2),
• b15 to b18 are each independently an integer from 1 to 8,
• * in Formulae 2-1 and 2-2 indicates a binding site to a corresponding neighboring atom in Formula 1, and
• * in Formulae 3-1 and 3-2 indicates a binding site to a corresponding neighboring atom in Formulae 2-1 or 2-2,
• In Formulae 401 and 402,
• M is selected from iridium (Ir), platinum (Pt), palladium (Pd), osmium (Os), titanium (Ti), zirconium (Zr), hafnium (Hf), europium (Eu), terbium (Tb), rhodium (Rh), and thulium (Tm),
• L401 is selected from ligands represented by Formula 402, and xc1 is 1, 2, or 3, wherein, when xc1 is two or more, two or more L401(s) are identical to or different from each other,
• L402 is an organic ligand, and xc2 is an integer from 0 to 4, wherein, when xc2 is two or more, two or more L402(S) are identical to or different from each other,
• X401 to X404 are each independently nitrogen or carbon,
• X401 and X403 are linked via a single bond or a double bond, and X402 and X404 are linked via a single bond or a double bond,
• A401 and A402 are each independently a C5-C60 carbocyclic group or a C1-C60 heterocyclic group,
• X405 is a single bond *—S—**, *—C(═O)—**, *—N(Q411)-**, *—C(Q411)(Q412)-**, *—C(Q411)=C(Q412)-**, *—C(Q411)=**, or *═C(Q411)=**, wherein Q411 and Q412 are each independently hydrogen, deuterium, a C1-C20 alkyl group, a C1-C20 alkoxy group, a phenyl group, a biphenyl group, a terphenyl group, or a naphthyl group,
• X406 is a single bond, O, or S,
• R401 and R402 are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a substituted or unsubstituted C1-C20 alkyl group, a substituted or unsubstituted C1-C20 alkoxy group, a substituted or unsubstituted C3-C10 cycloalkyl group, a substituted or unsubstituted C1-C10 heterocycloalkyl group, a substituted or unsubstituted C3-C10 cycloalkenyl group, a substituted or unsubstituted C1-C10 heterocycloalkenyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C6-C60 aryloxy group, a substituted or unsubstituted C6-C60 arylthio group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —Si(Q401)(Q402)(Q403), —N(Q401)(Q402), —B(Q401)(Q402), —C(═O)(Q401), —S(═O)2(Q401), and —P(═O)(Q401)(Q402), wherein Q401 to Q403 are each independently selected from a C1-C10 alkyl group, a C1-C10 alkoxy group, a C0-C20 aryl group, and a C1-C20 heteroaryl group,
• xc11 and xc12 are each independently an integer from 0 to 10,
• * and *′ in Formula 402 each indicate a binding site to M in Formula 401,
• at least one substituent of the substituted C5-C60 carbocyclic group, the substituted C2-C60 heterocyclic group, the substituted C1-C60 alkyl group, the substituted C2-C60 alkenyl group, the substituted C2-C60 alkynyl group, the substituted C1-C60 alkoxy group, the substituted C3-C10 cycloalkyl group, the substituted C1-C10 heterocycloalkyl group, the substituted C3-C10 cycloalkenyl group, the substituted C1-C10 heterocycloalkenyl group, the substituted C6-C60 aryl group, the substituted C6-C60 aryloxy group, the substituted C6-C60 arylthio group, the substituted C1-C60 heteroaryl group, the substituted monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group is selected from:
• deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C1-C60 alkyl group, a C2-C60 alkenyl group, a C2-C60 alkynyl group, and a C1-C60 alkoxy group;
• a C1-C60 alkyl group, a C2-C60 alkenyl group, a C2-C60 alkynyl group, and a C1-C60 alkoxy group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C3-C10 cycloalkyl group, a C1-C10 heterocycloalkyl group, a C3-C10 cycloalkenyl group, a C1-C10 heterocycloalkenyl group, a C6-C60 aryl group, a C6-C60 aryloxy group, a C6-C60 arylthio group, a C1-C60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —Si(Q11)(Q12)(Q13), —N(Q11)(Q12), —B(Q11)(Q12), —C(═O)(Q11), —S(═O)2(Q11), and —P(═O)(Q11)(Q12);
• a C3-C10 cycloalkyl group, a C1-C10 heterocycloalkyl group, a C3-C10 cycloalkenyl group, a C1-C10 heterocycloalkenyl group, a C6-C60 aryl group, a C6-C60 aryloxy group, a C6-C60 arylthio group, a C1-C60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group;
• a C3-C10 cycloalkyl group, a C1-C10 heterocycloalkyl group, a C3-C10 cycloalkenyl group, a C1-C10 heterocycloalkenyl group, a C6-C60 aryl group, a C6-C60 aryloxy group, a C6-C60 arylthio group, a C1-C60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C1-C60 alkyl group, a C2-C60 alkenyl group, a C2-C60 alkynyl group, a C1-C60 alkoxy group, a C3-C10 cycloalkyl group, a C1-C10 heterocycloalkyl group, a C3-C10 cycloalkenyl group, a C1-C10 heterocycloalkenyl group, a C6-C60 aryl group, a C6-C60 aryloxy group, a C6-C60 arylthio group, a C1-C60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —Si(Q21)(Q22)(Q23), —N(Q21)(Q22), —B(Q21)(Q22), —C(═O)(Q21), —S(═O)2(Q21), and —P(═O)(Q21)(Q22);
• and
• —Si(Q31)(Q32)(Q33), —N(Q31)(Q32), —B(Q31)(Q32), —C(═O)(Q31), —S(═O)2(Q31), and —P(═O)(Q31)(Q32),
• Q1, Q2, Q11 to Q13, Q21 to Q23, and Q31 to Q33 are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C1-C60 alkyl group, a C2-C60 alkenyl group, a C2-C60 alkynyl group, a C1-C60 alkoxy group, a C3-C10 cycloalkyl group, a C1-C10 heterocycloalkyl group, a C3-C10 cycloalkenyl group, a C1-C10 heterocycloalkenyl group, a C6-C60 aryl group, a C1-C60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, a biphenyl group, and a terphenyl group.

An organic light-emitting device comprising:

• a first electrode;
• a second electrode facing the first electrode;
• an organic layer between the first electrode and the second electrode, the organic layer comprising an emission layer;
• and
• a capping layer located outside the electrodes,
• wherein the capping layer comprises a compound represented by Formula 1:
• wherein, in Formulae 1, 2-1, 2-2, 3-1, and 3-2,
• X1 is O or S,
• Ar1 and Ar2 are each independently a substituted or unsubstituted C5-C60 carbocyclic group or a substituted or unsubstituted C2-C60 heterocyclic group,
• a1 and a2 are each independently an integer from 0 to 3,
• b1 and b2 are each independently 0 or 1,
• a1, a2, b1, and b2 satisfy a1+b1≥1 and a2+b2≥1,
• R1 and R2 are each independently a group represented by Formula 2-1,
• R3 is a group represented by Formula 2-2,
• A1 to A4 are each independently selected from a benzene group, a naphthalene group, a phenanthrene group, a fluoranthene group, a triphenylene group, a pyrene group, a chrysene group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, and a tetrazine group,
• A5 to A8 are each independently selected from a benzene group, a naphthalene group, a phenanthrene group, a fluoranthene group, a triphenylene group, a pyrene group, a chrysene group, a pyridine group, a pyrimidine group, a pyrazine group, a pyridazine group, and a tetrazine group,
• Y1 is a single bond, O, S, SO2, N(R19), C(R19)(R20), Si(R19)(R20), S(═O)(R19), S(═O)2(R19), or P(═O)(R19),
• Y2 is a single bond, O, S, SO2, N(R19), C(R19)(R20), Si(R19)(R20), S(═O)(R19), S(═O)2(R19), or P(═O)(R19),
• Y3 is a single bond, O, S, SO2, N(R19), C(R19)(R20), Si(R19)(R20), S(═O)(R19), S(═O)2(R19), or P(═O)(R19),
• Y4 is a single bond, O, S, SO2, N(R19), C(R19)(R20), Si(R19)(R20), S(═O)(R19), S(═O)2(R19), or P(═O)(R19),
• Y5 is a single bond, O, S, SO2, N(R19), C(R19)(R20), Si(R19)(R20), S(═O)(R19), S(═O)2(R19), or P(═O)(R19),
• wherein when Y2 is O, a group represented by Formula 2-1 and a group represented by Formula 2-2 are different from each other,
• R11 to R14 are each independently selected from a group represented by Formula 3-1, a group represented by Formula 3-2, hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a substituted or unsubstituted C1-C60 alkyl group, a substituted or unsubstituted C2-C60 alkenyl group, a substituted or unsubstituted C2-C60 alkynyl group, a substituted or unsubstituted C1-C60 alkoxy group, a substituted or unsubstituted C3-C10 cycloalkyl group, a substituted or unsubstituted C1-C10 heterocycloalkyl group, a substituted or unsubstituted C3-C10 cycloalkenyl group, a substituted or unsubstituted C1-C10 heterocycloalkenyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C6-C60 aryloxy group, a substituted or unsubstituted C6-C60 arylthio group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic group, —S(═O)(Q1), and —P(═O)(Q1)(Q2),
• wherein two or more R11(s) are optionally linked to form a substituted or unsubstituted C5-C60 carbocyclic group or a substituted or unsubstituted C2-C60 heterocyclic group, two or more R12(s) are optionally linked to form a substituted or unsubstituted C5-C60 carbocyclic group or a substituted or unsubstituted C2-C60 heterocyclic group, two or more R13(s) are optionally linked to form a substituted or unsubstituted C5-C60 carbocyclic group or a substituted or unsubstituted C2-C60 heterocyclic group, and two or more R14(s) are optionally linked to form a substituted or unsubstituted C5-C60 carbocyclic group or a substituted or unsubstituted C2-C60 heterocyclic group,
• b11 to b14 are each independently an integer from 1 to 8,
• when Y2 is a single bond, at least one of R13 and R14 is a group represented by Formula 3-1 or a group represented by Formula 3-2,
• R15 to R20 are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a substituted or unsubstituted C1-C60 alkyl group, a substituted or unsubstituted C2-C60 alkenyl group, a substituted or unsubstituted C2-C60 alkynyl group, a substituted or unsubstituted C1-C60 alkoxy group, a substituted or unsubstituted C3-C10 cycloalkyl group, a substituted or unsubstituted C1-C10 heterocycloalkyl group, a substituted or unsubstituted C3-C10 cycloalkenyl group, a substituted or unsubstituted C1-C10 heterocycloalkenyl group, a substituted or unsubstituted C6-C60 aryl group, a substituted or unsubstituted C6-C60 aryloxy group, a substituted or unsubstituted C6-C60 arylthio group, a substituted or unsubstituted C1-C60 heteroaryl group, a substituted or unsubstituted monovalent non-aromatic condensed polycyclic group, a substituted or unsubstituted monovalent non-aromatic condensed heteropolycyclic, —S(═O)(Q1), and —P(═O)(Q1)(Q2),
• b15 to b18 are each independently an integer from 1 to 8,
• at least one substituent of the substituted C5-C60 carbocyclic group, the substituted C2-C60 heterocyclic group, the substituted C1-C60 alkyl group, the substituted C2-C60 alkenyl group, the substituted C2-C60 alkynyl group, the substituted C1-C60 alkoxy group, the substituted C3-C10 cycloalkyl group, the substituted C1-C10 heterocycloalkyl group, the substituted C3-C10 cycloalkenyl group, the substituted C1-C10 heterocycloalkenyl group, the substituted C6-C60 aryl group, the substituted C6-C60 aryloxy group, the substituted C6-C60 arylthio group, the substituted C1-C60 heteroaryl group, the substituted monovalent non-aromatic condensed polycyclic group, and the substituted monovalent non-aromatic condensed heteropolycyclic group is selected from:
• deuterium, —F, —Cl —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C1-C60 alkyl group, a C2-C60 alkenyl group, a C2-C60 alkynyl group, and a C1-C60 alkoxy group;
• a C1-C60 alkyl group, a C2-C60 alkenyl group, a C2-C60 alkynyl group, and a C1-C60 alkoxy group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C3-C10 cycloalkyl group, a C1-C10 heterocycloalkyl group, a C3-C10 cycloalkenyl group, a C1-C10 heterocycloalkenyl group, a C6-C60 aryl group, a C6-C60 aryloxy group, a C6-C60 arylthio group, a C1-C60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —Si(Q11)(Q12)(Q13), —N(Q11)(Q12), —B(Q11)(Q12), —C(═O)(Q11), —S(═O)2(Q11), and —P(═O)(Q11)(Q12);
• a C3-C10 cycloalkyl group, a C1-C10 heterocycloalkyl group, a C3-C10 cycloalkenyl group, a C1-C10 heterocycloalkenyl group, a C6-C60 aryl group, a C6-C60 aryloxy group, a C6-C60 arylthio group, a C1-C60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group;
• a C3-C10 cycloalkyl group, a C1-C10 heterocycloalkyl group, a C3-C10 cycloalkenyl group, a C1-C10 heterocycloalkenyl group, a C6-C60 aryl group, a C6-C60 aryloxy group, a C6-C60 arylthio group, a C1-C60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, and a monovalent non-aromatic condensed heteropolycyclic group, each substituted with at least one selected from deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C1-C60 alkyl group, a C2-C60 alkenyl group, a C2-C60 alkynyl group, a C1-C60 alkoxy group, a C3-C10 cycloalkyl group, a C1-C10 heterocycloalkyl group, a C3-C10 cycloalkenyl group, a C1-C10 heterocycloalkenyl group, a C6-C60 aryl group, a C6-C60 aryloxy group, a C6-C60 arylthio group, a C1-C60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, —Si(Q21)(Q22)(Q23), —N(Q21)(Q22), —B(Q21)(Q22), —C(═O)(Q21), —S(═O)2(Q21), and —P(═O)(Q21)(Q22);
• and
• —Si(Q31)(Q32)(Q33), —N(Q31)(Q32), —B(Q31)(Q32), —C(═O)(Q31), —S(═O)2(Q31), and —P(═O)(Q31)(Q32),
• Q1, Q2, Q11 to Q13, Q21 to Q23, and Q31 to Q33 are each independently selected from hydrogen, deuterium, —F, —Cl, —Br, —I, a hydroxyl group, a cyano group, a nitro group, an amidino group, a hydrazino group, a hydrazono group, a C1-C60 alkyl group, a C2-C60 alkenyl group, a C2-C60 alkynyl group, a C1-C60 alkoxy group, a C3-C10 cycloalkyl group, a C1-C10 heterocycloalkyl group, a C3-C10 cycloalkenyl group, a C1-C10 heterocycloalkenyl group, a C6-C60 aryl group, a C1-C60 heteroaryl group, a monovalent non-aromatic condensed polycyclic group, a monovalent non-aromatic condensed heteropolycyclic group, a biphenyl group, and a terphenyl group,
• * in Formulae 2-1 and 2-2 indicates a binding site to a corresponding neighboring atom in Formula 1, and
• * in Formulae 3-1 and 3-2 indicates a binding site to a corresponding neighboring atom in Formulae 2-1 or 2-2.