Synthesis and characterization of cyclometalated Ir(III) complexes with pyrazolyl ancillary ligands

Jian Li; Peter I. Djurovich; Bert D. Alleyne; Irina Tsyba; Nam N. Ho; Robert Bau; Mark E. Thompson

doi:10.1016/j.poly.2003.11.028

Synthesis and characterization of cyclometalated Ir(III) complexes with pyrazolyl ancillary ligands

Jian Li
, Peter I. Djurovich
, Bert D. Alleyne
, Irina Tsyba
, Nam N. Ho
, Robert Bau
, Mark E. Thompson

Research output: Contribution to journal › Article › peer-review

157 Scopus citations

Abstract

The syntheses and structures of a series of (N,C2′-(2-para- tolylpyridine))₂Ir(LX) [(tpy)₂Ir(LX)] and (N,C2′-(4′,6′-difluorophenylpyridine))₂Ir(LX) [(dfppy)₂Ir(LX)] are reported, where LX are pyrazolyl and pyrazolyl-borate ligands. Reaction of the dichloro-bridged dimer [(tpy) ₂Ir(μ-Cl)]₂ with excess pyrazolyl-borate ligands forms a protonated-dipyrazolyl Ir complex, (tpy)₂Ir(pz₂H). The Ir bound chloride in [(tpy)₂Ir(μ-Cl)]₂ presumably facilitates the hydrolysis of pyrazolyl-borate. Thus, the syntheses of Ir complexes with bis(pyrazolyl)borates, e.g., (tpy)₂Ir(pz ₂Bpz₂) and (tpy)₂Ir(pz₂BEt ₂) require the chloride abstraction by CF₃SO ₃Ag before pyrazolyl-borate is added to the reaction solution. (tpy)₂Ir(pz₂H), (tpy)₂Ir(pzH) ₂(CF₃SO₃), (tpy)₂Ir(pz ₂Bpz₂) and (tpy)₂Ir(pz₂BEt ₂) have been structurally characterized by X-ray crystallography. The two pyrazolyl rings of (tpy)₂Ir(pz₂H) are nearly coplanar (dihedral angle, 12°), due to the presence of N-HN hydrogen bond (NN distance of 2.56 Å), while the two pyrazolyl rings of (tpy) ₂Ir(pzH)₂(CF₃SO₃) are not coplanar (pz-pz dihedral angle, 47°). Unlike other η²-pyrazolyl- borate complexes, the (tpy)₂Ir(pz₂BEt₂) exhibits a rare quasi-chair conformation adopted by the ring, rather than the more common boat conformations which have been observed previously. Similarly, the cycle of (tpy)₂Ir(pz₂Bpz₂) adopts a half-chair conformation, more flattened than the typical boat conformation. While the choice of pyrazolyl-borate ligand does not change the structural properties of the "(tpy)₂Ir" fragment, it markedly affects the photophysical properties of both (tpy)₂Ir(pz₂BR ₂) and (dfppy)₂Ir(pz₂BR₂) complexes. The pyrazolyl-borate ancillary ligands affect the absorption and emission energies of these complexes by tuning the HOMO (highest occupied molecular orbital) energies. The electron-withdrawing ancillary ligands, e.g., pz ₂Bpz₂^-, decrease the electron density on the iridium, stabilizing the metal-centered HOMOs.

Original language	English (US)
Pages (from-to)	419-428
Number of pages	10
Journal	Polyhedron
Volume	23
Issue number	2-3
DOIs	https://doi.org/10.1016/j.poly.2003.11.028
State	Published - Jan 22 2004
Externally published	Yes

Keywords

Boat conformations
Cyclometalated Ir(II) complexes
Electroluminescence
Iridium
Luminescent
Pyrazolyl ancillary ligands

ASJC Scopus subject areas

Physical and Theoretical Chemistry
Inorganic Chemistry
Materials Chemistry

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10.1016/j.poly.2003.11.028

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@article{4a1c7087b6dc45ac8dbac206d0f9e792,

title = "Synthesis and characterization of cyclometalated Ir(III) complexes with pyrazolyl ancillary ligands",

abstract = "The syntheses and structures of a series of (N,C2′-(2-para- tolylpyridine))2Ir(LX) [(tpy)2Ir(LX)] and (N,C2′-(4′,6′-difluorophenylpyridine))2Ir(LX) [(dfppy)2Ir(LX)] are reported, where LX are pyrazolyl and pyrazolyl-borate ligands. Reaction of the dichloro-bridged dimer [(tpy) 2Ir(μ-Cl)]2 with excess pyrazolyl-borate ligands forms a protonated-dipyrazolyl Ir complex, (tpy)2Ir(pz2H). The Ir bound chloride in [(tpy)2Ir(μ-Cl)]2 presumably facilitates the hydrolysis of pyrazolyl-borate. Thus, the syntheses of Ir complexes with bis(pyrazolyl)borates, e.g., (tpy)2Ir(pz 2Bpz2) and (tpy)2Ir(pz2BEt 2) require the chloride abstraction by CF3SO 3Ag before pyrazolyl-borate is added to the reaction solution. (tpy)2Ir(pz2H), (tpy)2Ir(pzH) 2(CF3SO3), (tpy)2Ir(pz 2Bpz2) and (tpy)2Ir(pz2BEt 2) have been structurally characterized by X-ray crystallography. The two pyrazolyl rings of (tpy)2Ir(pz2H) are nearly coplanar (dihedral angle, 12°), due to the presence of N-HN hydrogen bond (NN distance of 2.56 {\AA}), while the two pyrazolyl rings of (tpy) 2Ir(pzH)2(CF3SO3) are not coplanar (pz-pz dihedral angle, 47°). Unlike other η2-pyrazolyl- borate complexes, the (tpy)2Ir(pz2BEt2) exhibits a rare quasi-chair conformation adopted by the ring, rather than the more common boat conformations which have been observed previously. Similarly, the cycle of (tpy)2Ir(pz2Bpz2) adopts a half-chair conformation, more flattened than the typical boat conformation. While the choice of pyrazolyl-borate ligand does not change the structural properties of the {"}(tpy)2Ir{"} fragment, it markedly affects the photophysical properties of both (tpy)2Ir(pz2BR 2) and (dfppy)2Ir(pz2BR2) complexes. The pyrazolyl-borate ancillary ligands affect the absorption and emission energies of these complexes by tuning the HOMO (highest occupied molecular orbital) energies. The electron-withdrawing ancillary ligands, e.g., pz 2Bpz2-, decrease the electron density on the iridium, stabilizing the metal-centered HOMOs.",

keywords = "Boat conformations, Cyclometalated Ir(II) complexes, Electroluminescence, Iridium, Luminescent, Pyrazolyl ancillary ligands",

author = "Jian Li and Djurovich, \{Peter I.\} and Alleyne, \{Bert D.\} and Irina Tsyba and Ho, \{Nam N.\} and Robert Bau and Thompson, \{Mark E.\}",

note = "Funding Information: The authors thank Universal Display Corporation and the Defense Advanced Research Projects Agency for financial support of this work.",

year = "2004",

month = jan,

day = "22",

doi = "10.1016/j.poly.2003.11.028",

language = "English (US)",

volume = "23",

pages = "419--428",

journal = "Polyhedron",

issn = "0277-5387",

publisher = "Elsevier Limited",

number = "2-3",

}

TY - JOUR

T1 - Synthesis and characterization of cyclometalated Ir(III) complexes with pyrazolyl ancillary ligands

AU - Li, Jian

AU - Djurovich, Peter I.

AU - Alleyne, Bert D.

AU - Tsyba, Irina

AU - Ho, Nam N.

AU - Bau, Robert

AU - Thompson, Mark E.

N1 - Funding Information: The authors thank Universal Display Corporation and the Defense Advanced Research Projects Agency for financial support of this work.

PY - 2004/1/22

Y1 - 2004/1/22

N2 - The syntheses and structures of a series of (N,C2′-(2-para- tolylpyridine))2Ir(LX) [(tpy)2Ir(LX)] and (N,C2′-(4′,6′-difluorophenylpyridine))2Ir(LX) [(dfppy)2Ir(LX)] are reported, where LX are pyrazolyl and pyrazolyl-borate ligands. Reaction of the dichloro-bridged dimer [(tpy) 2Ir(μ-Cl)]2 with excess pyrazolyl-borate ligands forms a protonated-dipyrazolyl Ir complex, (tpy)2Ir(pz2H). The Ir bound chloride in [(tpy)2Ir(μ-Cl)]2 presumably facilitates the hydrolysis of pyrazolyl-borate. Thus, the syntheses of Ir complexes with bis(pyrazolyl)borates, e.g., (tpy)2Ir(pz 2Bpz2) and (tpy)2Ir(pz2BEt 2) require the chloride abstraction by CF3SO 3Ag before pyrazolyl-borate is added to the reaction solution. (tpy)2Ir(pz2H), (tpy)2Ir(pzH) 2(CF3SO3), (tpy)2Ir(pz 2Bpz2) and (tpy)2Ir(pz2BEt 2) have been structurally characterized by X-ray crystallography. The two pyrazolyl rings of (tpy)2Ir(pz2H) are nearly coplanar (dihedral angle, 12°), due to the presence of N-HN hydrogen bond (NN distance of 2.56 Å), while the two pyrazolyl rings of (tpy) 2Ir(pzH)2(CF3SO3) are not coplanar (pz-pz dihedral angle, 47°). Unlike other η2-pyrazolyl- borate complexes, the (tpy)2Ir(pz2BEt2) exhibits a rare quasi-chair conformation adopted by the ring, rather than the more common boat conformations which have been observed previously. Similarly, the cycle of (tpy)2Ir(pz2Bpz2) adopts a half-chair conformation, more flattened than the typical boat conformation. While the choice of pyrazolyl-borate ligand does not change the structural properties of the "(tpy)2Ir" fragment, it markedly affects the photophysical properties of both (tpy)2Ir(pz2BR 2) and (dfppy)2Ir(pz2BR2) complexes. The pyrazolyl-borate ancillary ligands affect the absorption and emission energies of these complexes by tuning the HOMO (highest occupied molecular orbital) energies. The electron-withdrawing ancillary ligands, e.g., pz 2Bpz2-, decrease the electron density on the iridium, stabilizing the metal-centered HOMOs.

AB - The syntheses and structures of a series of (N,C2′-(2-para- tolylpyridine))2Ir(LX) [(tpy)2Ir(LX)] and (N,C2′-(4′,6′-difluorophenylpyridine))2Ir(LX) [(dfppy)2Ir(LX)] are reported, where LX are pyrazolyl and pyrazolyl-borate ligands. Reaction of the dichloro-bridged dimer [(tpy) 2Ir(μ-Cl)]2 with excess pyrazolyl-borate ligands forms a protonated-dipyrazolyl Ir complex, (tpy)2Ir(pz2H). The Ir bound chloride in [(tpy)2Ir(μ-Cl)]2 presumably facilitates the hydrolysis of pyrazolyl-borate. Thus, the syntheses of Ir complexes with bis(pyrazolyl)borates, e.g., (tpy)2Ir(pz 2Bpz2) and (tpy)2Ir(pz2BEt 2) require the chloride abstraction by CF3SO 3Ag before pyrazolyl-borate is added to the reaction solution. (tpy)2Ir(pz2H), (tpy)2Ir(pzH) 2(CF3SO3), (tpy)2Ir(pz 2Bpz2) and (tpy)2Ir(pz2BEt 2) have been structurally characterized by X-ray crystallography. The two pyrazolyl rings of (tpy)2Ir(pz2H) are nearly coplanar (dihedral angle, 12°), due to the presence of N-HN hydrogen bond (NN distance of 2.56 Å), while the two pyrazolyl rings of (tpy) 2Ir(pzH)2(CF3SO3) are not coplanar (pz-pz dihedral angle, 47°). Unlike other η2-pyrazolyl- borate complexes, the (tpy)2Ir(pz2BEt2) exhibits a rare quasi-chair conformation adopted by the ring, rather than the more common boat conformations which have been observed previously. Similarly, the cycle of (tpy)2Ir(pz2Bpz2) adopts a half-chair conformation, more flattened than the typical boat conformation. While the choice of pyrazolyl-borate ligand does not change the structural properties of the "(tpy)2Ir" fragment, it markedly affects the photophysical properties of both (tpy)2Ir(pz2BR 2) and (dfppy)2Ir(pz2BR2) complexes. The pyrazolyl-borate ancillary ligands affect the absorption and emission energies of these complexes by tuning the HOMO (highest occupied molecular orbital) energies. The electron-withdrawing ancillary ligands, e.g., pz 2Bpz2-, decrease the electron density on the iridium, stabilizing the metal-centered HOMOs.

KW - Boat conformations

KW - Cyclometalated Ir(II) complexes

KW - Electroluminescence

KW - Iridium

KW - Luminescent

KW - Pyrazolyl ancillary ligands

UR - https://www.scopus.com/pages/publications/0842332882

UR - https://www.scopus.com/pages/publications/0842332882#tab=citedBy

U2 - 10.1016/j.poly.2003.11.028

DO - 10.1016/j.poly.2003.11.028

M3 - Article

SN - 0277-5387

VL - 23

SP - 419

EP - 428

JO - Polyhedron

JF - Polyhedron

IS - 2-3

ER -

Synthesis and characterization of cyclometalated Ir(III) complexes with pyrazolyl ancillary ligands

Abstract

Keywords

ASJC Scopus subject areas

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