“CH”/N Substituted mer-Gaq3 and mer-Alq3 Derivatives:  An Effective Approach for the Tuning of Emitting Color

Abstract

Equilibrium geometry configurations of the "CH"/N substituted Alq3 and Gaq3 derivatives are calculated by density functional theory (B3LYP/6-31G). The frontier molecular orbital and gap energy calculations for all complexes have been performed at the HF/6-31G level. It was shown that, compared to the pristine molecules, the HOMO and LUMO are stabilized, the net effect being however an increasing/decreasing of the gap (Eg) depending on the position of the substituted group. On the basis of the equilibrium geometries, the effect of the substitution on the absorption and emission spectra was evaluated using TDB3LYP/3-21G. It was shown that the change of "CH"/N substituted position on 8-hydroxyquinoline ligand is a powerful approach for the tuning of emitting color. An important blue shift was predicted for 5-substituted 8-hydroxyquinoline derivatives, an important red one being observed for 4-substituted ones. Interestingly, relatively significant blue and red shifts were also predicted for the 7- and 2-substituted derivatives. In this work, the correlation between the spectrum shifts and the metal-ligand bonding is also discussed.

Push-pull effect on the geometrical, optical and charge transfer properties of disubstituted derivatives of mer-tris(4-hydroxy-1,5-naphthyridinato) aluminum (mer-AlND3)

“…The electron/hole transport is predictable from the electron (λ ele )/hole (λ hole ) reorganization energies and in general has good agreement with the experimental observations [27,71,82,[85][86][87][88][89][90][91][92][93][94][95]. Previously the reorganization energies for hole/ electron of mer-Alq3 and its derivatives [56,57,59,61,63] and mer-AlND3 [64] has been calculated at B3LYP/6-31G(D) level. Hence the reorganization energy calculations have been carried out for (1-8) using the same methodology and compared with AlND3 (Table 7).…”

“…The geometry optimizations have been carried out using DFT/B3LYP/6-31G(D) method using G09 package [53]. This method has been proved to be a reliable approach for Alq3 and its derivatives [54][55][56][57][58][59][60][61][62][63], mer-AlND3 and its methyl derivatives [64]. During optimization the atomic positions of the all these derivatives have been fully relaxed without any constraints and only the lowestlying minima are reported.…”

“…Frequency calculations have been carried out to ensure that the optimized geometry has all positive frequencies and thus is a minimum on the potential energy surface. The first excited state (S 1 ) geometries have been optimized using the ab initio CIS approach [37] and previously this approach has been applied on mer-Alq3 and its derivatives [54][55][56][57][58][59][60][61][62][63], mer-AlND3 and its methyl derivatives [64] and other OLED materials [67][68][69][70][71] which has given reliable results. The absorption and emission spectra of these derivatives have been evaluated at by PBE0/6-31G(D) method using the B3LYP/6-31G(D) and CIS/6-31G(D) optimized geometries respectively.…”

“…The S 1 geometry optimizations for (1-8), have been carried out by CIS/6-31G(D) method using the corresponding HF/6-31G(D) optimized ground state (HF-S 0 ) geometries. In our previous study, the same approach has been adopted for mer-AlND3 and its methyl derivatives [64] and in earlier reports this method has been successfully applied on Alq3 and its derivatives [27,[54][55][56][57][58][59][60][61][62][63]. The optimized bond lengths of the ground state at the optimized at HF/6-31G(D) (HF-S 0 ) and the excited state at the CIS/6-31G(D) (S 1 )methods respectively along with the differences between the bond lengths of the S 1 and HF-S 0 states for ligands A(∆A E-G ), B(∆B E-G ) and C(∆C E-G ) are shown in Table 3 [1 (type I) and 5 (type II)] and Table S1(a-d) [supportinginformation for (1)(2)(3)(4)(5)(6)(7)(8)].…”

Chemical failure modes of AlQ3-based OLEDs: AlQ3 hydrolysis

“…7 From a theoretical standpoint, numerous studies have been carried out examining the properties of AlQ3 directly related to its role in OLED devices; including the mechanism of charge transport 8 and the nature of the excited electronic states giving rise to device emission. [9][10][11][12] Despite showing excellent device characteristics, full realization of this technology has been hampered due to a lack of device stability. OLEDs incorporating AlQ3 suffer from device degradation due to localized chemical failure and from a longtime intrinsic degradation in performance.…”