Synthesis and spectroscopic studies of cyclometalated Pt(II) complexes containing a functionalized cyclometalating ligand, 2-phenyl-6-(1H-pyrazol-3-yl) -pyridine

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

75 Scopus Citations
View graph of relations

Author(s)

  • Chi-Kin Koo
  • Yu-Man Ho
  • Cheuk-Fai Chow
  • Michael Hon-Wah Lam
  • Tai-Chu Lau
  • And 1 others
  • Wai-Yeung Wong

Detail(s)

Original languageEnglish
Pages (from-to)3603-3612
Journal / PublicationInorganic Chemistry
Volume46
Issue number9
Online published5 Apr 2007
Publication statusPublished - 30 Apr 2007

Abstract

Three new luminescent cyclometalated Pt(II) complexes, [Pt(L)Cl] (1), [Pt2(L-)2] (2), and [Pt(L)(PPh3)]ClO4 (3·ClO4) (where HL = 2-phenyl-6-(1H-pyrazol-3-yl)-pyridine), were synthesized and characterized by X-ray crystallography. HL represents a new class of C,N,Npyrazolyl cyclometalating ligands containing a Cphenyl, a Npyridyl, and a Npyrazolyl donor moiety, as well as a 1-pyrazolyl-NH, that can also be available for metal coordination and other chemical interactions. Complex 1 possesses intense intraligand transitions at 275−375 nm and moderately intense metal-to-ligand charge transfer (1MLCT) (dπ(Pt) → π*(L)) transition at 380−410 nm. The room temperature solid-state emission λmax of 1 occurs at 580 nm and is attributable to the 3MMLCT (dσ*(Pt) → π*(L)) transition. It also displays strong phosphorescence in acetonitrile solutions at room temperature with an emission λmax at 514 nm, which can be tentatively assigned to the 3MLCT (π*(L) → dπ(Pt)) transition. Complex 1 can be deprotonated in organic solvents to yield a cycloplatinated dimer 2, which shows a relatively high room-temperature luminescent quantum yield of 0.59 in DMF (λmax = 509 nm). Substitution of the ancillary chloro-ligand in 1 by triphenylphosphine yields 3, which also possesses a good room-temperature luminescent quantum yield of 0.52 in DMF (λmax = 504 nm) and a better solubility in water. Complex 3 is synthesized to demonstrate the pH dependence of luminescent properties of this C,N,Npyrazolyl cyclometalated Pt(II) system. Such a pH response is ascribable to the protonation/deprotonation of the 1-pyrazolyl-NH on the C,N,Npyrazolyl cyclometalating ligand. The pKa of the 1-pyrazolyl-NH in 3, measured in 1:2 (v/v) aqueous DMF solutions, is approximately 4.0.

Citation Format(s)

Synthesis and spectroscopic studies of cyclometalated Pt(II) complexes containing a functionalized cyclometalating ligand, 2-phenyl-6-(1H-pyrazol-3-yl) -pyridine. / Koo, Chi-Kin; Ho, Yu-Man; Chow, Cheuk-Fai et al.

In: Inorganic Chemistry, Vol. 46, No. 9, 30.04.2007, p. 3603-3612.

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review