Electronic structures and spectroscopic properties of promising highly efficient red phosphorescent Os(II)(LR)2(PH3)2 complexes: a theoretical exploration

The red phosphorescent osmium(II) complexes [Os(LR)₂(PH₃)₂] (L = 2-pyridyltriazole (ptz): R = H (1a), CF₃ (1b), t-Bu (1c)); L = 2-pyridylpyrazole (ppz): R = H (2a), CF₃ (2b), t-Bu (2c)); L = 2-phenylpyridine (ppy): R = H (3a)) were explored using density functional theory (DFT) methods. The ground- and excited-state geometries of the complexes were optimized at the B3LYP/LANL2DZ and UB3LYP/LANL2DZ levels, respectively. The absorption and phosphorescence of the complexes in CH₂Cl₂ media were calculated based on the optimized ground- and excited-state geometries using time-dependent density functional theory method with the polarized continuum model. The optimized geometry structural parameters of the complexes in the ground state agree well with the corresponding experimental values. The lower-lying unoccupied molecular orbitals of the complexes are dominantly localized on the L ligand, while the higher-lying occupied ones are composed of Os(II) atom and L ligand. The low-lying metal-to-ligand and intraligand charge transfer (MLCT/ILCT) transitions and high-lying ILCT transitions are red-shifted with the increase in the π-donating ability of the L ligand and the π electron-donating ability of R substituent. The calculation revealed that the phosphorescence originated from ³MLCT/³ILCT excited state. However, the complex 3a displayed different types of MLCT/ILCT excited state compared with that of 1a–2c, and the different types of transition were also found in the absorption. In addition, we found that the phosphorescence quantum efficiency of Os(II) complexes is related to the metal composition in the high-energy occupied molecular orbitals, it will be helpful to designing highly efficient phosphorescent materials.     

Theoretical study on the spectroscopic properties and electronic structures of heteroleptic phosphorescent Ir(III) complexes

The geometries, spectroscopic and electronic structures properties of a series of heteroleptic phosphorescent Ir(III) complexes including N981, N982, N983, N984 have been characterized by density functional theory calculations. The excited‐state properties of the Ir(III) complexes have been characterized by CIS method. The ground‐ and excited‐state geometries were optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. By using the time‐dependent density functional theory method, the absorption and phosphorescence spectra were calculated based on the optimized ground‐ and excited‐state geometries, respectively. The results show that the absorption and emission data agree well with the corresponding experimental results. The calculated results also revealed that the nature of the substituent at the 4‐position of the pyridyl moiety can influence the distributions of HOMO and LUMO and their energies. In addition, the charge transport quality has been estimated approximately by the calculated reorganization energy (λ). Our result also indicates that the positions of the substitute groups not only change the transition characters but also affect the charge transfer rate and balance, and complex N982 is a very good charge transfer material for green OLEDs. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009     

Synthesis and spectroscopic characterization of new mono- and binuclear complexes of some NH(1) thiosemicarbazides

4-Ethylthiosemicarbazide and its NH(1) derivatives have been prepared and confirmed by elemental analysis and ¹H?NMR spectra to produce diverse complexes with Co(II), Ni(II) and Cu(II) ions. The obtained complexes have been investigated based on elemental and thermal analyses, spectral (UV/VIS, ESR, mass) studies and magnetic measurements. The IR data reveal the presence of variable modes of chelation for the investigated ligands. The electronic spectra of the complexes as well as their magnetic moments provide information about geometries. The ESR spectra give evidence for the proposed structure and the bonding for some Cu(II) complexes. Thermal decomposition of some complexes ended with metal or metal oxide as a final product.     

高效膦基锇配合物磷光材料的结构和光谱性质

采用B3LYP和UB3LYP方法分别优化了一系列(N^N)2Os(P^P)[P^P=1,2-双(膦基)-甲基,N^N=5-(苯并咪唑-2-基)-3-三氟甲基吡啶(1);ibfpH=5-(1-异丙基-苯并咪唑-2-基)-3-三氟甲基吡啶(2);fppzH=5-(吡啶-2-基)-3-三氟甲基吡啶(3);tfpH=5-(噻唑-2-基)-3-三氟甲基吡啶(4);btfpH=5-(苯基噻唑-2-基)-3-三氟甲基吡啶(5)]配合物的基态和激发态结构.计算得到的Os-P(1),Os-N(1)和Os-N(2)基态键长和相应实验值符合较好.相对于基态,激发态几何结构变化较小,与实验上观察到的斯托克斯频移相一致.配合物1-5的最高占据分子轨道主要由Os的d轨道和N^N配体的π轨道构成,而它们的最低空轨道主要由N^N配体的π反键轨道占据,前线分子轨道能量受N^N配体影响较大.在TD-DFT计算水平下结合PCM溶剂模型,得到配合物1-5的最低能吸收和发射分别在415,416,465,458,481nm和541,538,569,629,655nm.这些跃迁均来自于HOMO→LUMO的激发,具有MLCT/ILCT混合跃迁性质,并且它们的高能吸收也具有相似的跃迁特征.发射波长的巨大差异显示出通过调节N^N配体的π电子捐赠能力可以实现对此类配合物发光颜色的调节.     

Theoretical study on the influence of ancillary ligand on the spectroscopic properties and electronic structures of phosphorescent Pt(II) complexes

The geometries, energies, and electronic properties of a series of phosphorescent Pt(II) complexes including FPt, CFPt, COFPt, and NFPt have been characterized within density functional theory DFT calculations which can reproduce and rationalize experimental results. The properties of excited‐states of the Pt(II) complexes were characterized by configuration interaction with singles (CIS) method. The ground‐ and excited‐state geometries were optimized at the B3LYP/LANL2DZ and CIS/LANL2DZ levels, respectively. In addition, we also have performed a triplet UB3LYP optimization for complex FPt and compared it with CIS method in the emission properties. The datum (562.52 nm) of emission wavelength for complex FPt, which were computed based on the triplet UB3LYP optimization excited‐state geometry, is not agreement with the experiment value (500 nm). The absorption and phosphorescence wavelengths were computed based on the optimized ground‐ and excited‐state geometries, respectively, by the time‐dependent density functional theory (TD‐DFT) methods. The results revealed that the nature of the substituent at the phenylpyridine ligand can influence the distributions of HOMO and LUMO and their energies. Moreover, the auxiliary ligand pyridyltetrazole can make the molecular structure present a solid geometry. In addition, the charge transport quality has been estimated approximately by the predicted reorganization energy (λ). Our result also indicates that the substitute groups and different auxiliary ligand not only change the nature of transition but also affect the rate and balance of charge transfer. By summarizing the results, we can conclude that the NFPt is good OLED materials with a solid geometry and a balanced charge transfer rate. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010     

Solid-state spectroscopic properties and the geometry of binuclear rhodium(I) diisocyanoalkane complexes

A series of crystalline dinuclear rhodium complexes with different bridging diisocyano ligands and different counter ions have been studied by low-temperature crystallographic and solid-state spectroscopic techniques. The Rh-Rh distances vary from 4.5153(3) to 3.0988(7) angstroms, and the twist angles around the Rh-Rh line from 58.3(1) to 0 degree, both depending on the size and conformational rigidity of the bridging ligand. For very long distances as occur in the [Rh(2)(dimen)(4)](2+) salts the absorption is significantly blue-shifted compared to other complexes. For a given cation a shorter Rh-Rh bond gives a red shift of the phosphorescence emission band, indicating a smaller energy gap between the ground and emitting excited states. An exception occurs for the [Rh(2)(1,6-diisocyanohexane)(4)](2+) ion, in which dimer formation in the calixarate salt lengthens the Rh-Rh intramolecular bond length without affecting the emission spectrum.     

Electronic structures and photophysical properties of phosphorescent platinum (II) complexes with tridentate C^N*N cyclometalated ligands

To get an insight into the structure–property relationships in a series of strongly phosphorescent platinum(II) complexes with tridentate C^N*N cyclometalated ligands, their electronic structures and electroluminescence properties were systematically investigated via density functional theory and time‐dependent density functional theory. Moreover, the factors related to the radiative and non‐radiative decay process, including the transition electric dipole moment μ(S_n), the energy difference between singlet and lowest triplet excited states ΔE(S_n–T₁) and the spin–orbital coupling matrix elements $?S_n\left|{\stackrel{?}{H}}_{\mathrm{SOC}}\right|T_1?$, as well as the energy gap between T₁ and S₀ states ΔE(T₁–S₀) and absorption–emission Stokes shifts have been calculated. Fine emission color tuning and high phosphorescence quantum yield of phosphorescent complexes may be achieved through introducing five–six‐membered metallacycle geometries and linking a substituent (such as phenyl) at bridge atoms. Additionally, phosphorescent properties of these complexes show a clear dependence on the electronegativity of bridge atoms.     

Reactions of platinum complexes with 4,7-phenanthroline: crystal structures of mono- and binuclear platinum(II) complexes containing 4,7-phenanthroline

The reaction of a mixture of cis and trans-[PtCl₂(SMe₂)₂] with 4,7-phen (4,7-phen = 4,7-phenanthroline) in a molar ratio of 1 : 1 or 2 : 1 resulted in the formation of mono and binuclear complexes trans-[PtCl₂(SMe₂)(4,7-phen)] (1) and trans-[Pt₂Cl₄(SMe₂)₂(μ-4,7-phen)] (2), respectively. The products have been fully characterized by elemental analysis, ¹H, ¹³C{¹H}, HHCOSY, HSQC, HMBC, and DEPT-135 NMR spectroscopy. The crystal structure of 1 reveals that platinum has a slightly distorted square planar geometry. Both chlorides are trans with a deviation from linearity 177.66(3)°, while the N–Pt–S angle is 175.53(6)°. Similarly, the reaction of a mixture of cis and trans-[PtBr₂(SMe₂)₂] with 4,7-phen in a 1 : 1 or 2 : 1 mole ratio afforded the mono or binuclear complexes trans-[PtBr₂(SMe₂)(4,7-phen)] (3) and trans-[Pt₂Br₄(SMe₂)₂(μ-4,7-phen)] (4), respectively. The crystal structure of trans-[Pt₂Br₄(SMe₂)₂(μ-4,7-phen)].C₆H₆ reveals that 4,7-phen bridges between two platinum centers in a slightly distorted square planar arrangement of the platinum. In this structure, both bromides are trans, while the PtBr₂(SMe₂) moieties are syn to each other. NMR data of mono and binuclear complexes of platinum 1–4 show that the binuclear complexes exist in solution as a minor product, while the mononuclear complexes are major products.     

Synthesis and X-ray structures of some mono- and binuclear ruthenium complexes with bisphosphine ligands

Summary The dinuclear complexes {RuCp*(-Cl)}₂(-dppm) (1) and {RuCp*(-Cl)}₂ (-dppe) (3) are obtained by reacting [RuCp*(³-Cl)]₄ withdppm, anddppe, respectively.1 is readily oxidized with AgCF₃SO₃, instead of chloride abstraction, to afford the dinuclear complex [{RuCp*(-Cl)}₂(-dppm)](SO₃CF₃)₂ (2) with two metal centers connected by a single Ru-Ru bond. Under the same conditions,3 decomposes to several intractable materials. Similarly to1, RuCp* (dmpe)Cl reacts with AgCF₃SO₃ to afford the Ru(III) complex [RuCp*(dmpe)Cl](SO₃CF₃) (4) without no halide abstraction. The crystal structures of2,3, and4 are presented.

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Synthese und Röntgenstrukturanalyse einiger ein- und zweikerniger Rutheniumkomplexe mit Bisphosphinliganden

Zusammenfassung Die Komplexe {RuCp*(-Cl)}₂(-dppm) (1) und {RuCp*(-Cl₂(-dppe) (3) wurden durch Umsetzung von [RuCp*(³-Cl)]₄ mitdppm bzw.dppe dargestellt.1 wird durch AgCF₃SO₃ zum zweikernigen Komplex [{RuCp*(-Cl)}₂(-dppm)](SO₃CF₃)₂ (2) oxidiert, welcher eine Ru-Ru-Metallbindung aufweist. Unter den gleiche Reaktionsbedingungen zersetzt sich3 zu undefinierten Produkten. Analog zu1 reagiert RuCp* (dmpe)Cl mit AgCF₃SO₃ zum Ru(III)-Komplex [Ru(Cp*)(dmpe)Cl](SO₃CF₃) (4) wobei es zu keiner Chloridabspaltung kommt. Von2,3, und4 wurden die Kristallstrukturen bestimmt.

     

New mono- and binuclear Pd(II) complexes containing 1,2,4-triazole moieties

The reaction of AMTT (AMTT = 4-amino-3-methyl-1,2,4-triazol-5-thione, HL1) with palladium(II) chloride and triphenylphosphane as a co-ligand in acetonitrile afforded the mononuclear Pd^II-complex [(PPh₃)Pd(HL1)Cl]Cl·2CH₃CN (1). The complex [(PPh₃)Pd(HL1)I]Cl·1/2H₂O (2) was prepared via halogen exchange between 1 and sodium iodide in methanol/acetonitrile. The first binuclear palladium(II) complex containing singly deprotonated HL1, [(PPh₃)₂ClPd(L1)Pd(PPh₃)Cl]Cl·1/3H₂O·CH₃OH (3), was prepared by the reaction of HL1 with palladium(II) chloride and triphenylphosphane in the presence of sodium acetate in methanol.     

Structural and spectroscopic features of mono- and binuclear nickel(II) complexes with tetradentate N(amine)2S(thiolate)2 ligation

Three complexes containing Ni(II)N(amine)2S(thiolate)2 units have been prepared and characterized. Both (R,R)-N,N'-bis(1-carboxy-2-mercaptoethyl)-1,2-diaminoethane [(R,R)-1] and N,N'-bis(2-methyl-2-mercaptoprop-1-yl)-1,3-diamino-2,2-dimethylpropane (4) act as tetradentate S-N-N-S ligands to form complexes Ni((R,R)-1) and Ni4 with nearly planar cis-NiN2S2 units. The N-Ni-N and S-Ni-S angles differ significantly in the two complexes yet are very nearly supplementary. The 1,3-disubstituted cyclohexane species rac-N,N'-bis(2-mercapto-2-methylprop-1-yl)-1,3-cyclohexanediamine (6) behaves as a bis(bidentate-N,S) ligand to form an unexpectedly intense-blue dinickel complex (1S,3R,1'S,3'R)-7, which contains two trans-NiN2S2 units bridged by 1,3-disubstituted cyclohexane groups. The coordination geometry in (1S,3R,1'S,3'R)-7 is distorted 15 degrees toward tetrahedral, most likely as a result of steric crowding, suggested by several short contacts between the NiS2 units and both the cyclohexyl and gem-dimethyl groups of the N,S-chelate rings. The complexes exhibit rich UV-vis spectra, whose deconvoluted bands are now fully assigned, from low to high energy, as ligand field (LF), pi(S) --> Ni(II) ligand-to-metal charge transfer (LMCT), sigma(S) --> Ni(II) LMCT, sigma(N) --> Ni(II) LMCT, localized S, and S,N Rydberg transitions. The unusually intense LF absorptions shown by (1S,3R,1'S,3'R)-7 are thought to result from relaxation of the Laporte restriction arising from the 15 degrees tetrahedral twist.     

d8和d10配合物激发态性质和金属间弱相互作用的理论研究

随着量子化学理论方法和计算机技术的发展,量子理论模型已成为一种研究分子的高能、不稳定电子态-激发态的最有效手段.通过对一系列d8和d10配合物的激发态电子结构和电子激发前后金属相互作用的理论研究进行了评述.电子吸收和发射是极其复杂的微观过程,涉及到基态与激发态的电子结构性质、金属间弱相互作用、相对论效应等量子理论的基础问题,揭示配合物发光性质的规律性对新型光学材料的探索和设计具有重要指导意义.     

Electronic structures and optical properties of neutral substituted fluorene-based cyclometalated platinum(II)-acetylide complexes: A DFT exploration

We report a combinational DFT and TD-DFT study of the electronic and optical properties of several tridentate cyclometalated mononuclear [Pt(C^N^N)(CCR)] (1-3), [Pt(C^N^N)(CCRCCH)] (4), and dinuclear [Pt(C^N^N)(CCRCC)Pt(C^N^N)] (5 (C₂ symmetry) and 5′ (C_s symmetry)) platinum(II) complexes with σ-acetylide ligand bearing fluorene substituents, where HC^N^N = 6-aryl-2,2′-bipyridine, R = fluorene-2,7-diyl 1, 4, 5 and 5′, R = 9,9-dimethylfluorene-2,7-diyl 2, R = 9,9-diethylfluorene-2,7-diyl 3. The structural and electronic properties of the ground- and lowest triplet state and the EA and IP values of the complexes are discussed. It is found that all of the lowest-lying absorptions are categorized as the LLCT combined with the MLCT transitions. The oscillator strengths of the lowest energy absorptions get a remarkable enhancement for the dinuclear complexes 5 and 5′compared to 1-4 due to the increase of electronic delocalization on the more planar molecular geometry. In general, the phosphorescent emissions of these complexes in CH₂Cl₂ are the reverse process of their lowest energy absorption transitions, except that of 4 is assigned as ³[π∗−π]/³MLCT transition because of the strengthened electronic localization effect and the interaction with the solvent in the lowest triplet state. In addition, these complexes hold promise as a new kind of nonlinear optical material owing to their large static first hyperpolarizabilities (β₀). The β₀ value has increased in the dinuclear complexes in contrast to those of the mononuclear ones owing to their larger transition moment and smaller transition energy.     

两种8-羟基喹啉锌配合物电子结构和光谱性质的理论研究

采用密度泛函理论在PBE0/6-31+G(d)-LANL2DZ水平下优化了两种8-羟基喹啉锌配合物的基态几何构型,并在相同水平下进行了频率分析以确认稳定点的性质.根据基态优化的构型,在TD-PBE0/6-31+G(d)-LANL2DZ水平下,采用极化连续介质模型(PCM)计算了甲醇溶剂中配合物的电子结构和电子吸收光谱.计算结果表明,配合物B中8-羟基喹啉2号位取代基蒽较大的π共轭作用使其具有较小的HOMO-LUMO能级差,从而使配合物B的最大吸收波长发生了红移现象.     

Two binuclear tetracarboxylate-bridged complexes: syntheses,structures, and properties

Cu₂(C₉N₅H₉)₂(C₆H₅CO₂)₄ (1) and Zn₂(C₉N₅H₉)₂(C₁₀H₇CH₂CO₂)₄ (2) have been synthesized by hydrothermal methods with 2,4-diamine-6-phenyl-1,3,5-triazine (phdat) and aromatic carboxylic acid (benzoic acid (ba) or naphthylacetic acid (naa)) as ligands and characterized by single-crystal X-ray diffractions, elemental analyses, infrared spectra, magnetism, fluorescence spectra, and thermogravimetric analyses. In 1 and 2, the two metals are bridged by four carboxylates in paddle-wheel-shaped binuclear [M₂(CO₂)₄] units (M=Cu (1) and Zn (2)) and coordinated by one nitrogen from phdat, forming five-coordinate centers. The temperature-dependent magnetic susceptibility of 1 was obtained from 300 to 2?K, showing an anti-ferromagnetic interaction between Cu(II)'s. Compound 2 exhibits solid state fluorescence at 404?nm upon excitation at 304?nm.     

Structure and chromotropic properties of mono- and binuclear mixed-ligand nickel(II) complexes containing 1,3-diketonate and polyamine ligands

Abstract  Mixed-ligand Ni^II complexes have been synthesized with 1,3-diketonate and bulky tri- or tetra-amine ligands. Their structures were determined by X-ray crystallography, and solvatochromic behavior was examined by UV–vis–NIR spectroscopy. Steric effects of the bulky ligands on the coordination distances and spectral properties are discussed. Graphical Abstract  

Structure and chromotropic properties of mono- and binuclear mixed-ligand nickel(II) complexes containing 1,3-diketonate and polyamine ligands

Abstract  

Mixed-ligand Ni^II complexes have been synthesized with 1,3-diketonate and bulky tri- or tetra-amine ligands. Their structures were determined by X-ray crystallography, and solvatochromic behavior was examined by UV–vis–NIR spectroscopy. Steric effects of the bulky ligands on the coordination distances and spectral properties are discussed.     

Ligand effects on structures and spectroscopic properties of pyridine-2-aldoxime complexes of Re(CO)3(+): DFT/TDDFT theoretical studies

The series of novel rhenium(I) tricarbonyl mixed-ligand complexes Re(X)(CO)(3)(N^N) (N^N = pyridine-2-aldoxime; X = -Cl, 1; X = -CN, 2; and X = -C≡C, 3) has been investigated theoretically to explore the ligand X effect on their electronic structures and spectroscopic properties. The contribution of the X ligand to the highest occupied molecular orbital (HOMO) and HOMO-1 decreases in the order of 3 > 1 > 2, in line with the π-donating abilities of the X: -C≡C > -Cl > -CN. The reorganization energy (λ) calculations show that 1 and 3 will result in the higher efficiency of organic light-emitting diodes than 2. The lowest-lying absorptions of 1 and 3 can be assigned to the {[d(xz), d(yz)(Re) + π(CO) + π(X)] → [π* (N^N)]} transition with mixing metal-to-ligand, ligand-to-ligand, and X ligand-to-ligand charge transfer (MLCT/LLCT/XLCT) character, whereas this absorption at 354 nm (H-1 → L) of 2 is assigned to {[d(xz), d(yz)(Re) + π(CO) + π(N^N)] → [π* (N^N)]} transition with MLCT/LLCT/ILCT (intraligand charge transfer). Furthermore, the absorptions are red-shifted in the order 2, 1, and 3, with the increase of π-donating abilities of X ligands. The solvent effects cause red shifts of the absorption and emission spectra with decreasing solvent polarity.