Optical properties and electronic structures of axially-ligated group 9 porphyrins

Abstract

A series of group 9 metal tetra(ptolyl)porphyrin (M(ttp), M = Co(II), Rh(III), Ir(III)) complexes with axial phenyl substituents have been synthesized and characterized. An aryl bromide cleavage reaction of transition metal complexes was used to prepare the complexes from Co(ttp), Rh(ttp)Cl and Ir(ttp)COCl, respectively. Magnetic circular dichroism (MCD) spectroscopy and TDDFT calculations have been used to study trends in the optical spectra and electronic structures. The effect of introducing different parasubstituents on the phenyl substituents was examined. During fluorescence emission studies, phosphorescence was observed for the Ir(III) complexes in the near infrared (NIR) region.

Near‐Infrared Phosphorescent Supramolecular Alkyl/Aryl‐Iridium Porphyrin Assemblies by Axial Coordination

“…Additionally, the quantum yields of the Ir(tptbp) complexes are more than twice those of the Ir(ttp) analogues. Notably, the Ir(ttp)‐based ensembles 3 – 5 exhibit emission maxima (742–745 nm) that are substantially redshifted relative to those of their precursors 2 a – 2 c (714–718 nm) observed in this work and those of [Ir(ttp)(Ar)] (Ar= p ‐FC 6 H 4 , p ‐BrC 6 H 4 , p ‐MeOC 6 H 4 ; 690–700 nm) reported previously . Large redshifts (25–28 nm) of the emission maxima were also found on going from 2 a – 2 c to 2 a′ – 2 c′ (Table ).…”

Iridium(III)porphyrin arrays with tuneable photophysical properties

“…The photophysical properties of Ir(III)porphyrins differ significantly from others cyclometalated Ir(III) compounds and other group 9 metal porphyrin complexes, which is due to the closed shell diamagnetic d 6 configuration. 10 The literature reports that d 6 metalloporphyrins exhibits red to near-infrared luminescence (NIR) derived from the 3 (π, π*) intraligand state of the porphyrin ligand or the 3 (dπ, π*) metal-to-ligand charge transfer (MLCT) state upon photoexcitation. 22 In the case of Ir(III)porphyrin complex derivatives, previously reported works reveal that the complexes exhibit a strong red to NIR PL in solution at room temperature, with an emission quantum yield up to 0.85.…”

“…22 In the case of Ir(III)porphyrin complex derivatives, previously reported works reveal that the complexes exhibit a strong red to NIR PL in solution at room temperature, with an emission quantum yield up to 0.85. [9][10][23][24] The optical properties of organic compounds are set through their energy gap, i.e., the energy separation amongst the highest occupied molecular orbital (HOMO) and respectively. [26][27] Five Q absorption transitions can be detected for the free porphyrin H 2 TTP in toluene (Figures 1a) and 2a)), peaked at 648 nm, 592 nm, 548 nm, 514 nm, 482 nm.…”

“…Actually, the combination of Ir(III) as central metal and porphyrin is quite rare and only few groups have contributed to the synthesis, spectroscopic properties studies, and catalytic activities of these complexes. [6][7][8][9][10] Iridium(III) ion metal is hexacoordinated, which enables the possibility of introducing axial ligands directly on the metal. These can change the complex solubility or introduce new binding groups to improve the photophysical properties, efficiency and versatility.…”