Theoretical study on photophysical property of cuprous bis-phenanthroline coordination complexes

We herein report a theoretical analysis using density functional theory (DFT) and time-dependent DFT (TDDFT) to study the electronic structures and photophysical properties of mixed-ligand Cu(i) complexes. An evaluation of the non-radiative and radiative decay rate constants (knr and kr) is presented. It is found that large spin-orbit coupling (SOC) matrix elements do not necessarily result in large values of kr. Introducing the POP (bis[2-(diphenylphosphino)phenyl]ether) ligand instead of a pair of PPh3 (triphenylphosphine) ligands, it is found that the ether linkage plays an important role in governing the quantum efficiency of the studied complexes. However, the balance between hole injection and electron acceptance, which leads to the quantum yield of [Cu(dmp)(POP)](+) being close to that of [Cu(dbp)(POP)](+), is another important factor in tuning the quantum efficiency. A thorough understanding of the effect of the coordinating ligand on the photophysical behavior of a transition metal complex is desirable for the rational synthesis of highly phosphorescent materials.

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“…The method of calculation of the inner reorganization energy λ i for hole and electron transfer is same as our previously used method in ref. 26.…”

Section: Comparison Of Performance In Oledsmentioning

confidence: 99%

A theoretical analysis of the phosphorescence efficiencies of Cu(i) complexes

Zou

Cheng

et al. 2014

Dalton Trans.

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“…On the other hand, several efforts have been focused on the chemical isolation of Cu(I) complexes containing Cu(I) centers such as those present in bioavailable Cu-based enzymes and proteins as copper monooxygenase (e.g., laccase). This enzyme reduces dioxygen by a four-electron mechanism, or as hemocyanins that react reversibly with molecular oxygen and catalyze its reduction at potentials very close to that of the O 2 /H 2 O reversible potential. − It is well-known that the Cu(I) bisphenanthroline complexes in organic media are oxidized by O 2 to form Cu(II) bisphenanthroline in homogeneous media and the rates of the reaction are very sensitive to the nature of substituents on the ligand. , The formal potential of the complexes and their photophysical and electrochemistry properties are also dependent of the p K a of the ligands in these kinds of complexes. − However, the catalytic activity of Cu(I) complexes for ORR in aqueous media, when they are confined on an electrode surface, has been difficult to study because of the existing dynamic equilibria between the bisphenanthroline complex ([Cu(I)(phen) 2 ] + ) and the monophenanthroline complex ([Cu(I)(phen)X 2 ] + , X = solvent coordinating ligand). − Some authors have pointed out that monophenanthroline complexes are more catalytic than bisphenanthroline complexes; ,,− this might be related to favorable changes in the binding energy of Cu–O 2 for mono- compared to bisphenanthroline complexes but to the best of our knowledge no theoretical calculations of these energies have been reported. The coordination geometry is strongly dependent on the oxidation state of the copper center; for four-coordinated Cu(I) a pseudo-tetrahedral configuration is more stable, and for Cu(II) a square-planar configuration is more favorable. , Thus, the Cu(II)/Cu(I) redox process for the studied species is accompanied by a geometric flattening of the Cu(I) center.…”

Section: Introductionmentioning

confidence: 99%

Theoretical and Experimental Reactivity Predictors for the Electrocatalytic Activity of Copper Phenanthroline Derivatives for the Reduction of Dioxygen

et al. 2019

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We have systematically studied the catalytic activity of a series of substituted bisphenanthroline Cu complexes adsorbed on glassy carbon electrodes for the oxygen reduction reaction (ORR) in aqueous media. The aim of this work is to test reactivity descriptors for ORR previously proposed for MN4 complexes. As the active site is the Cu(I) center, the foot of the wave for O 2 reduction on electrodes modified with Cu bisphenanthrolines appears at potentials very close to the [Cu(II)phen 2 ] ad ++ + e − ⇆ [Cu(I)phen 2 ] ad + redox process. Generally, the catalytic activity as (log i)E versus the E Cu(II)/(I) °redox potentials follows a linear correlation with a slope close to +0.120 V/decade, where the activity increases as the E Cu(II)/(I) °becomes more positive. This indicates that electron-withdrawing substituents on the ligand favor the reaction by shifting the E Cu(II)/(I) °to more positive values, making the Cu center more noble. This shift in the E Cu(II)/(I) °is essentially an electronic effect. However, another way to stabilize the Cu(I) state is by placing groups on the ligand that hinder the [Cu(II) square-planar ] ad ++ /[Cu(I) tetrahedral ] ad+ change. We have found that this steric effect seems to be more prominent than the electronic effects caused by electron-withdrawing groups and the increase in the catalytic activity for ORR is more pronounced.

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“…In particular, extensive photophysical studies were conducted for copper(I) complexes that are pseudo-tetrahedrally coordinated by two bidentate chelating ligands. Homoleptic complexes with N^N (bisimine) 6,9,10,[54][55][56][57][58][59][60] or P^P (bisphosphine) 54,[61][62][63] ligands as well as heteroleptic complexes with N^N/P^P (bisimine/ bisphosphine) 10,28,31,32,54,[64][65][66] ligands were investigated. Typically, for such complexes optical or electrical excitation induces a metal-to-ligand charge transfer (MLCT) by which Cu(I) is formally oxidized to Cu(II).…”

Section: Introductionmentioning

confidence: 99%

A new class of luminescent Cu(i) complexes with tripodal ligands – TADF emitters for the yellow to red color range

et al. 2015

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A new class of emissive and neutral Cu(I) compounds with tripodal ligands is presented. The complexes were characterized chemically, computationally, and photophysically. Under ambient conditions, the powders of the compounds exhibit yellow to red emission with quantum yields ranging from about 5% to 35%. The emission represents a thermally activated delayed fluorescence (TADF) combined with a short-lived phosphorescence which represents a rare situation and is a consequence of high spin-orbit coupling (SOC). In the series of the investigated compounds the non-radiative rates increase with decreasing emission energy according to the energy gap law while the radiative rate is almost constant. Furthermore, a well-fit linear dependence between the experimental emission energies and the transition energies calculated by DFT and TD-DFT methods could be established, thus supporting the applicability of these computational methods also to Cu(I) complexes.

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Theoretical study on photophysical property of cuprous bis-phenanthroline coordination complexes

Cited by 24 publications

References 27 publications

A theoretical analysis of the phosphorescence efficiencies of Cu(i) complexes

A theoretical analysis of the phosphorescence efficiencies of Cu(i) complexes

Theoretical and Experimental Reactivity Predictors for the Electrocatalytic Activity of Copper Phenanthroline Derivatives for the Reduction of Dioxygen

A new class of luminescent Cu(i) complexes with tripodal ligands – TADF emitters for the yellow to red color range

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