Malays. J. Anal. Sci. Volume 29 Number 1 (2025): 1347

 

Research Article

 

Synthesis and characterisation of cationic iridium(III) complex with phenanthroline-based ancillary ligand

 

Nur Khaliesa Zulkarnaen, Noorshida Mohd Ali*, Suzaliza Mustafar, Azlan Kamari and Nurul Husna As Saedah Bain

 

Faculty of Sciences and Mathematics, Universiti Pendidikan Sultan Idris, Tanjong Malim, Perak, Malaysia

 

*Corresponding author: noorshida@fsmt.upsi.edu.my

 

Received: 19 September 2024; Revised: 27 November 2024; Accepted: 2 December 2024; Published: 23 February 2025

 

Abstract

The unique photophysical properties of cyclometalated iridium(III) complexes have sparked great interest in their synthesis as dopants for organic light-emitting diodes (OLEDs). Herein, a cationic iridium(III) complex, [Ir(dfppy)2(neocuproine)]+[PF6]- (dfppy = 2-(2,4-difluorophenyl)pyridine and neocuproine = 2,9-dimethyl-1,10-phenan throline) was synthesised and characterised. The essential structural conformation of the newly synthesised complex was accomplished by utilising a combination of FTIR, 1H, 13C, 19F, 31P-NMR spectroscopies and Elemental Analyser (CHN). FTIR spectrum revealed absorption bands for C=N and C=C stretching at 1406–1514 cm⁻¹ and 1558–1599 cm⁻¹, respectively. The ¹H-NMR spectrum displayed signals for phenylpyridine and phenanthroline protons between δ 5.64 and 8.51 ppm, along with a distinct methyl singlet at δ 2.22 ppm. The 13C-NMR spectrum showed 36 carbon atoms, corresponding to the number of carbon atoms present in the complex. In the ¹⁹F-NMR spectrum, the PF6⁻ counterion displayed signals at δ -72.5 and -74.1 ppm, while the fluorine atoms on the phenyl ring of dfppy gave signals at δ -106.2 and -108.5 ppm. At δ -134.4 to -154.5ppm in the 31P-NMR spectrum, the PF6⁻ counterion exhibited a significant septet peak. Elemental analysis confirmed the complex's purity and composition of carbon, hydrogen, and nitrogen, aligning with its molecular formula. The UV-Vis spectrum showed a weaker band from 320 nm into the visible region, attributed to metal-to-ligand charge-transfer (MLCT) transitions. Steady-state emission spectroscopy demonstrated the iridium(III) complex emitted green light in dichloromethane solution at room temperature (lem = 483 nm) due to radiative deactivation of ³MLCT.

 

Keywords: Iridium(III) complex, 2-(2,4-difluorophenyl)pyridine, ancillary ligand, phenanthroline, 2,9-dimethyl-1,10-phenanthroline

 

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