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Cyclometallated iridium and platinum complexes with noninnocent ligands

Hirani, Bhavna; Li, Jian; Djurovich, Peter I.; Yousufuddin, Muhammed; Oxgaard, Jonas; Persson, Petter LU ; Wilson, Scott R.; Bau, Robert; Goddard, William A., III and Thompson, Mark E. (2007) In Inorganic Chemistry 46(10). p.3865-3875
Abstract
The electronic properties of the cyclometalated ((CN)-N-and) complexes of iridium and platinum metals with a catechol ligand have been studied experimentally and computationally. The synthesis and characterization of (p-tolylpyridine)Ir(3,5-di-tert-butylcatechol) (abbreviated Ir-sq) and (2,4-diflorophenylpyridine)Pt(3,5-di-tert-butylcatechol) (abbreviated Pt-sq) are reported along with their structural, spectral, and electrochemical properties. Reaction of the 3,5-di-tert-butylcatechol (DTBCat) ligand with the prepared cyclometalated metal complex was carried out in air in the presence of a base. The resulting complexes are air stable and are paramagnetic with the unpaired electron residing mainly on the catechol ligand. The bond lengths... (More)
The electronic properties of the cyclometalated ((CN)-N-and) complexes of iridium and platinum metals with a catechol ligand have been studied experimentally and computationally. The synthesis and characterization of (p-tolylpyridine)Ir(3,5-di-tert-butylcatechol) (abbreviated Ir-sq) and (2,4-diflorophenylpyridine)Pt(3,5-di-tert-butylcatechol) (abbreviated Pt-sq) are reported along with their structural, spectral, and electrochemical properties. Reaction of the 3,5-di-tert-butylcatechol (DTBCat) ligand with the prepared cyclometalated metal complex was carried out in air in the presence of a base. The resulting complexes are air stable and are paramagnetic with the unpaired electron residing mainly on the catechol ligand. The bond lengths obtained from X-ray structure analysis and the theoretical results suggest the semiquinone form of the catechol ligand. Low-energy, intense (similar to 10(3) M-1 cm(-1)) transitions are observed in the visible to near-infrared region (600-700 nm) of the absorption spectra of the metal complexes. Electrochemically, the complexes exhibit a reversible reduction of the semiquinone form to the catechol form of the ligand and an irreversible oxidation to the unstable quinone form of the ligand. The noninnocent catechol ligand plays a significant role in the electronic properties of the metal complexes. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations on the two open-shell molecules provide the ground-state and excited-state energies of the molecular orbitals involved in the observed low-energy transitions. The spin density in the two complexes resides mainly on the catechol ligand. The intense transition arises from excitation of the beta electron from a HOMO-n (n = 1 or 2 here) to the LUMO, rather than from the excitation of the unpaired alpha electron. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
Inorganic Chemistry
volume
46
issue
10
pages
3865 - 3875
publisher
The American Chemical Society
external identifiers
  • wos:000246209800015
  • scopus:34249684730
ISSN
1520-510X
DOI
10.1021/ic061556b
language
English
LU publication?
yes
id
fc6f6e09-6d01-4d3e-8ebc-bd47fbfbb928 (old id 662642)
date added to LUP
2007-12-11 14:14:51
date last changed
2017-10-08 03:44:53
@article{fc6f6e09-6d01-4d3e-8ebc-bd47fbfbb928,
  abstract     = {The electronic properties of the cyclometalated ((CN)-N-and) complexes of iridium and platinum metals with a catechol ligand have been studied experimentally and computationally. The synthesis and characterization of (p-tolylpyridine)Ir(3,5-di-tert-butylcatechol) (abbreviated Ir-sq) and (2,4-diflorophenylpyridine)Pt(3,5-di-tert-butylcatechol) (abbreviated Pt-sq) are reported along with their structural, spectral, and electrochemical properties. Reaction of the 3,5-di-tert-butylcatechol (DTBCat) ligand with the prepared cyclometalated metal complex was carried out in air in the presence of a base. The resulting complexes are air stable and are paramagnetic with the unpaired electron residing mainly on the catechol ligand. The bond lengths obtained from X-ray structure analysis and the theoretical results suggest the semiquinone form of the catechol ligand. Low-energy, intense (similar to 10(3) M-1 cm(-1)) transitions are observed in the visible to near-infrared region (600-700 nm) of the absorption spectra of the metal complexes. Electrochemically, the complexes exhibit a reversible reduction of the semiquinone form to the catechol form of the ligand and an irreversible oxidation to the unstable quinone form of the ligand. The noninnocent catechol ligand plays a significant role in the electronic properties of the metal complexes. Density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations on the two open-shell molecules provide the ground-state and excited-state energies of the molecular orbitals involved in the observed low-energy transitions. The spin density in the two complexes resides mainly on the catechol ligand. The intense transition arises from excitation of the beta electron from a HOMO-n (n = 1 or 2 here) to the LUMO, rather than from the excitation of the unpaired alpha electron.},
  author       = {Hirani, Bhavna and Li, Jian and Djurovich, Peter I. and Yousufuddin, Muhammed and Oxgaard, Jonas and Persson, Petter and Wilson, Scott R. and Bau, Robert and Goddard, William A., III and Thompson, Mark E.},
  issn         = {1520-510X},
  language     = {eng},
  number       = {10},
  pages        = {3865--3875},
  publisher    = {The American Chemical Society},
  series       = {Inorganic Chemistry},
  title        = {Cyclometallated iridium and platinum complexes with noninnocent ligands},
  url          = {http://dx.doi.org/10.1021/ic061556b},
  volume       = {46},
  year         = {2007},
}