Effect of Substituents on Electronic Structure and Photophysical Properties of Re(I)(CO)&amp;lt;sub&amp;gt;3&amp;lt;/sub&amp;gt;Cl(R-2, 2’-Bipyridine) Complex: DFT/TDDFT Study

Dereje Fedasa,Alemu Talema,Dunkana Negussa

doi:10.11648/j.ijctc.20200802.11

Abstract

The electronic structure, absorption and emission spectra, as well as phosphorescence efficiency of Re(I) tricarbonyl complexes of a general formula fac-[Re(I)(CO)3(L)(R-N^N)](L = Cl; N^N = 2, 2’-bipyridine; R = -H, 1; -NO2, 2; -PhNO2, 3; -NH2, 4; -TPA (triphenylamine), 5) were investigated by using density functional theory(DFT) and time dependents density functional theory (TDDFT) methods. The calculated results reveal that introductions of the Electron with drawing group (EWG) and Electron donating group (EDG) on the R position of 2, 2’-bipyridine ligand. When EWG (-NO2 and -PhNO2) are introduced into complex 2 and 3, the lowest energy absorption and emission bands are red shifted compared with that of complex 1. On the contrary, the introduction of the EDG (-NH2 and -TPA) in complex 4 and 5 cause corresponding blue shifted. The solvent effect on absorption and emission spectrum indicates that the lowest energy absorption and emission bands have red shifts with the decrease of solvent polarity. The electronic affinity (EA), ionization potential (IP) and reorganization energy (λ) results show that complex 5 is suitable to be used as an emitter in phosphorescence organic light emitting diodes (PHOLEDs). Meanwhile the emission quantum yield of complex 5 is possibly higher than that of other complexes.

Highlights

Organic light emitting diodes (OLEDs) are solid state electronic devices which emit light in response to the applied electric current
Introductions of Electron with drawing group (EWG) (-NO2 and -PhNO2) can decrease the energy level of LUMO resulting in narrower energy gap, which lead to red shifted of the lowest energy absorption bands in comparison with that of complex 1
The solvent effect on absorption and emission spectra indicates that lowest-energy absorption and emission bands have red-shift with the decrease of solvent polarity for these complexes

Summary

Introduction

Organic light emitting diodes (OLEDs) are solid state electronic devices which emit light in response to the applied electric current. Among different types of OLEDs, PHOLEDs are the classes of OLED that use the principle of phosphorescence to offer four times the internal efficiency of conventional fluorescent OLEDs. Light emitting organic materials has phosphorescent materials which serve as recombination centers for electrons and holes to produce the electronic excited states are mainly captivating. Light emitting organic materials has phosphorescent materials which serve as recombination centers for electrons and holes to produce the electronic excited states are mainly captivating Because, they harvest light from both singlet and triplet excitons and enabling the devices with close to 100% internal quantum efficiency [1]. PHOLEDs have attracted worldwide attention over the past decades due to their unique features and huge potential for flat panel, flexible display, energy saving solid state lighting and virtual reality [3]

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