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Updated: Jan 7, 2026

Synthesis of pH Dependent Pyrazole, Imidazole, and Isoindolone Dipyrrinone Fluorophores using a Claisen-Schmidt Condensation Approach
Published on: June 10, 2021
Addition of Amine-Substituted Heteroaromatic Rings to Alkynyl Bridging Ligands to Generate Phosphorescent Emitters
Cristina Martín-Escura1, Enrique Oñate1, Montserrat Oliván1
1Departamento de Química Inorgánica, Instituto de Síntesis Química y Catálisis Homogénea (ISQCH), Centro de Innovación en Química Avanzada (ORFEO-CINQA), Universidad de Zaragoza─CSIC, 50009 Zaragoza, Spain.
Abstract:
Alkynyl ligands are versatile building blocks in the design of luminescent iridium(III) complexes due to their ability to support postcoordination functionalization that gives rise to ligands non available through conventional coordination chemistry. Here, we report the synthesis and characterization of a new family of heteroleptic iridium(III) green emitters based on cyclometalated 2-p-tolylpyridine as main ligands and new C,N-chelating units as the auxiliary ligand that yield iridaimidazole structures. The alkynyl bridging dimer cis-[Ir(μ-C≡CtBu){κ2-C,N-(MeC6H3-py)}2]2 (1) reacts with amine-substituted five-membered heterocycles bearing two heteroatoms, such as 1-methyl-1H-imidazol-2-amine, 1-methyl-1H-benzo[d]imidazol-2-amine, 4-methyloxazol-2-amine, benzo[d]oxazol-2-amine, 4-methylthiazol-2-amine, and benzo[d]thiazol-2-amine, giving the iridaimidazole derivatives Ir{κ2-C,N-(MeC6H3-py)}2{κ2-C,N-[C(CH2tBu)N-im]} (im = imidazole, 2), Ir{κ2-C,N-(MeC6H3-py)}2{κ2-C,N-[C(CH2tBu)N-bzim]} (bzim = benzimidazole, 3), Ir{κ2-C,N-(MeC6H3-py)}2{κ2-C,N-[C(CH2tBu)N-oxazol]} (4), Ir{κ2-C,N-(MeC6H3-py)}2{κ2-C,N-[C(CH2tBu)N-bzoxazol]} (5), Ir{κ2-C,N-(MeC6H3-py)}2{κ2-C,N-[C(CH2tBu)N-thiazol]} (6), and Ir{κ2-C,N-(MeC6H3-py)}2{κ2-C,N-[C(CH2tBu)N-bzthiazol]} (7), respectively. The iridium center in these complexes is in an octahedral environment with nitrogen and carbon atoms in a facial disposition. Complexes 2, 4, and 6 feature one five-membered heteroaromatic ring fused to the iridaimidazole cycle whereas 3, 5, and 7 additionally contain a benzo group fused to the organic heterocycle. All complexes are green phosphorescent emitters (474-558 nm) upon photoexcitation, with high quantum yields (0.55-0.92) in poly(methyl methacrylate) films and 2-MeTHF at 298 K.
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Electrophilic Addition to Alkynes: Halogenation
Halogenation is another class of electrophilic addition reactions where a halogen molecule gets added across a π bond. In alkynes, the presence of two π bonds allows for the addition of two equivalents of halogens (bromine or chlorine). The addition of the first halogen molecule forms a trans-dihaloalkene as the major product and the cis isomer as the minor product. Subsequent addition of the second equivalent yields the tetrahalide.