Theoretical Studies of Ground and Excited Electronic States in a Series of Rhenium(I) Bipyridine Complexes Containing Diarylethynyl-Based Structure (original) (raw)
Related papers
Journal of Physical Chemistry A, 2004
Density functional theory (DFT) is applied to analyze ground-and excited-state properties of the Re(I) halide bipyridine complex ReCl(CO) 3 (bpy) (1) and the related complexes ReCl(CO) 3 (5,5′-dibromo-bpy) (2), ReCl-(CO) 3 (4,4′-dimethyl-bpy) (3), and ReCl(CO) 3 (4,4′-dimethylformyl-bpy) (4) (where bpy ) 2,2′bipyridine). The electronic properties of the neutral molecules, in addition to the positive and negative ions, are studied using the B3LYP functional. Excited singlet and triplet states are examined using time-dependent DFT (TDDFT). The low-lying excited-state geometries are optimized at the ab initio configuration interaction singlets (CIS) level. As shown, the occupied orbitals involved in the transitions have a significant mixture of the metal Re and the group Cl, by the amount of metal 5d character which varies from 30 to 65%. The lowest unoccupied molecular orbital (LUMO) is a π* orbital of the ligand bpy for the series of molecules. The TDDFT result indicates that the absorption maxima are at relatively high energy and are mainly assigned to bpy-based ππ* transitions with somewhat metal-to-ligand charge transfer (MLCT) [d(Re) f π*(bpy)] and ligand-to-ligand charge transfer (LLCT) [p(Cl) f π*(bpy)] except for complex 3, in which this band is mainly assigned to mixed MLCT/LLCT, and overlaps bpy ππ* character. All the low-lying transitions are categorized as mixed MLCT/LLCT. The absorption bands are blue shifted when substituted by an electron-releasing group (-CH 3 ), and they are red shifted when substituted by an electron-withdrawing group (-Br or -COOCH 3 ). The luminescence of all complexes is assigned as a triplet metal/chlorine to bpy charge transfer (MLCT/LLCT).
0riginal article, 2020
To cite this article: Dereje Fedasa, Dunkana Negussa, Alemu Talema. Effect of Substituents on Electronic Structure and Photophysical Properties of Re(I)(CO) 3 Cl(R-2, 2'-Bipyridine) Complex: DFT/TDDFT Study. 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;-NO 2 , 2;-PhNO 2 , 3;-NH 2 , 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 (-NO 2 and-PhNO 2) 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 (-NH 2 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.
International journal of computational and theoretical chemistry, 2020
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;-NO 2 , 2;-PhNO 2 , 3;-NH 2 , 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 (-NO 2 and-PhNO 2) 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 (-NH 2 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.
Inorganic Chemistry, 2013
A computational approach for calculating the distortions in the lowest energy triplet metal to ligand charge-transfer (3 MLCT = T 0) excited states of ruthenium(II)−bipyridine (Ru−bpy) complexes is used to account for the patterns of large variations in vibronic sideband amplitudes found in the experimental 77 K emission spectra of complexes with different ancillary ligands (L). Monobipyridine, [Ru(L) 4 bpy] m+ complexes are targeted to simplify analysis. The range of known emission energies for this class of complexes is expanded with the 77 K spectra of the complexes with (L) 4 = bis-acetonylacetonate (emission onset at about 12 000 cm −1) and 1,4,8,11-tetrathiacyclotetradecane and tetrakis-acetonitrile (emission onsets at about 21 000 cm −1); no vibronic sidebands are resolved for the first of these, but they dominate the spectra of the last two. The computational modeling of excited-state distortions within a Franck−Condon approximation indicates that there are more than a dozen important distortion modes including metal−ligand modes (low frequency; lf) as well as predominately bpy modes (medium frequency; mf), and it simulates the observed 77 K emission spectral band shapes of selected complexes very well. This modeling shows that the relative importance of the mf modes increases very strongly as the T 0 energy increases. Furthermore, the calculated metal-centered SOMOs show a substantial bpy−π-orbital contribution for the complexes with the highest energy T 0. These features are attributed to configurational mixing between the diabatic MLCT and the bpy 3 ππ* excited states at the highest T 0 energies.
Inorganic Chemistry, 2002
Infrared data in the ν(CO) region (1800−2150 cm-1 , in acetonitrile at 298 K) are reported for the ground (ν gs) and polypyridyl-based, metal-to-ligand charge-transfer (MLCT) excited (ν es) states of cis-[Os(pp) 2 (CO)(L)] n+ (pp) 1,-10-phenanthroline (phen) or 2,2′-bipyridine (bpy); L) PPh 3 , CH 3 CN, pyridine, Cl, or H) and fac-[Re(pp)(CO) 3 (4-Etpy)] + (pp) phen, bpy, 4,4′-(CH 3) 2 bpy, 4,4′-(CH 3 O) 2 bpy, or 4,4′-(CO 2 Et) 2 bpy; 4-Etpy) 4-ethylpyridine). Systematic variations in ν gs , ν es , and ∆ν (∆ν) ν es − ν gs) are observed with the excited-to-ground-state energy gap (E 0) derived by a Franck−Condon analysis of emission spectra. These variations can be explained qualitatively by invoking a series of electronic interactions. Variations in dπ(M)−π*(CO) back-bonding are important in the ground state. In the excited state, the important interactions are (1) loss of back-bonding and σ(M−CO) bond polarization, (2) π*(pp•-)−π*(CO) mixing, which provides the orbital basis for mixing π*(CO)-and π*(4,4′-X 2 bpy)-based MLCT excited states, and (3) dπ(M)−π(pp) mixing, which provides the orbital basis for mixing ππ*-and π*(4,4′-X 2bpy•-)-based MLCT states. The results of density functional theory (DFT) calculations on the ground and excited states of fac-[Re I (bpy)(CO) 3 (4-Etpy)] + provide assignments for the ν(CO) modes in the MLCT excited state. They also support the importance of π*(4,4′-X 2 bpy•-)−π*(CO) mixing, provide an explanation for the relative intensities of the A′(2) and A′′ excited-state bands, and provide an explanation for the large excited-to-ground-state ν(CO) shift for the A′(2) mode and its relative insensitivity to variations in X.
Excited-State Electronic Structure in Polypyridyl Complexes Containing Unsymmetrical Ligands
Inorganic Chemistry, 1999
Step-scan Fourier transform infrared absorption difference time-resolved (S 2 FTIR ∆A TRS) and time-resolved resonance Raman (TR 3 ) spectroscopies have been applied to a series of questions related to excited-state structure in the metal-to-ligand charge transfer (MLCT) excited states of [Ru(bpy) 2 (4,4′-(CO 2 Et) 2 bpy)] 2+ , [Ru(bpy) 2 (4-CO 2 Et-4′-CH 3 bpy)] 2+ , [Ru(bpy)(4,4′-(CO 2 Et) 2 bpy) 2 ] 2+ , [Ru(4,4′-(CO 2 Et) 2 bpy) 3 ] 2+ , [Ru(bpy) 2 (4,4′-(CONEt 2 ) 2bpy)] 2+ , [Ru(bpy) 2 (4-CONEt 2 -4′-CH 3 bpy)] 2+ , and [Ru(4-CONEt 2 -4′-CH 3 bpy) 3 ] 2+ (bpy is 2,2′-bipyridine). These complexes contain bpy ligands which are either symmetrically or unsymmetrically derivatized with electronwithdrawing ester or amide substituents. Analysis of the vibrational data, largely based on the magnitudes of the ν j(CO) shifts of the amide and ester substituents (∆ν j(CO)), reveals that the ester-or amide-derivatized ligands are the ultimate acceptors and that the excited electron is localized on one acceptor ligand on the nanosecond time scale. In the unsymmetrically substituted acceptor ligands, the excited electron is largely polarized toward the ester-or amide-derivatized pyridine rings. In the MLCT excited states of [Ru(bpy) 2 (4,4′-(CO 2 Et) 2 bpy)] 2+ and [Ru(bpy) 2 (4,4′-(CONEt 2 ) 2 bpy)] 2+ , ∆ν j(CO) is only 60-70% of that observed upon complete ligand reduction due to a strong polarization interaction in the excited state between the dπ 5 Ru III core and the excited electron.
Inorganic Chemistry, 1989
A series of dirhenium complexes of the type Re2(CO),(p-H)(p-py)(L), where L = CO or py and py = pyridine or 4-benzoylpyridine, have been synthesized. Excited-state properties of these and related rhenium carbonyl complexes containing pyridine or 4benzoylpyridine as a-bound or p-bridged ligands have been investigated in an effort to design organometallic complexes that possess long-lived excited states generated from the photoexcitation of the M-M a-bond. Emissive metal-to-ligand charge-transfer states of the type dl(M)r*L or UM-MT*L have been observed in complexes containing bridging ligands, and their intermolecular electron-transfer reactions with a variety of neutral or charged donors and acceptors have been studied by emission and transient absorption spectroscopic techniques. Quenching of [Re2(C0)7(p-H)(p-py)(L)] * (py = L = 4-benzoylpyridine) by a series of trialkyl-and triarylphosphines is shown to proceed solely by electron-transfer pathways. We have also studied the electron-transfer reduction of a series of substituted N-methylpyridinium salts by the same excited-state molecule and attempted to correlate the rate of electron tranfser with the reduction potential of the quencher.
The Journal of Physical Chemistry A, 2005
Absorption, emission, and excitation spectra for solid-state and solution of Tb(III), Dy(III), and Gd(III) complexes with the polypyridine ligand 6,6′-bis[bis(2-pyridylmethyl)-aminomethyl]-2,2′-bipyridine (C 36 H 34 N 8) are presented. Measurements of excited-state lifetimes and quantum yields in various solvents at room temperature and 77 K are also reported and used to characterize the excited-state energetics of this system. Special attention is given to the characterization of metal-to-ligand energy transfer efficiency and mechanisms. The measurement of circularly polarized luminescence (CPL) from the solution of the Dy(III) complex following circularly polarized excitation confirms the chiral structure of the complexes under study. No CPL is present in the luminescence from the Eu(III) or Tb(III) complex because of efficient racemization. The variation of the magnitude of the CPL as a function of temperature from an aqueous solution of DyL is used for the first time to characterize the solution equilibria between different chiral species.
Inorganic Chemistry, 1990
The photophysical and photochemical properties of the series of tris-chelate complexes Ru(bpy),(bpyz),-?+, Ru(bpy),(bpym)3-:+, R~(bpym),(bpyz)~-,2+, and Ru(bpy)(bpym)(bpyz)2+ (n = 0, 1, 2, 3; bpy = 2,2'-bipyridine, bpyz = 2,2'-bipyrazine, bpym = 2,2'-bipyrimidine) are described. From the results of temperature-dependent lifetime (210-345 K) and room-temperature emission quantum yield measurements have been obtained: (1) k, and k,,, the radiative and nonradiative decay rate constants for the emitting MLCT manifold and (2) kinetic parameters which suggest the intervention of additional excited states. The significant points of the study are the following: (1) trends in k,, properties are understandable based on the energy gap law, (2) low-lying dd states strongly influence lifetimes and photochemical instabilities for the complexes Ru(bpy~)~'+, Ru(bp~m)3~+, Ru(bpy)(b~yz)~~+, Ru(bpy)(b~ym)~~+, Ru(bpym)(b~yz)~~+, Ru(bp~m)~(bpyz)~+, and Ru-(bpy)(bpym)(bpyz)*+ at room temperature, and (3) for the complexes R~(bpy),(bpyz)~+ and R~(bpy),(bpym)~+ there is no evidence for low-lying dd states and these and/or related mixed-ligand complexes may provide a basis for a new series of photochemically stable Ru-polypyridyl chromophores. The absorption spectra of polypyridyl complexes of Ru(I1) and Os(I1) are dominated by metal-to-ligand charge-transfer (MLCT) transitions, e.g.,