一类[Os(II)(CO)3(tfa)(L)](L=O^O,O^N,N^N)配合物的结构和光谱特征

采用密度泛函理论以及B3LYP方法和单激发组态相互作用(CIS)方法分别优化了一系列[Os(II)(CO)3(tfa)(L)](tfa为三氟乙酸; L=O^O(1), O^N(2), N^N(3), 其中O^O为六氟乙酰丙酮, O^N为羟基喹啉, N^N为3-(三氟甲基)-5-(2-吡啶基)吡唑)配合物的基态和激发态结构. 利用含时密度泛函理论(TD-DFT)结合极化连续溶剂化模型(PCM)计算了配合物在CH2Cl2溶液中的吸收和发射光谱. 研究结果表明, 优化得到的几何结构参数和相应的实验值符合得非常好, 激发态几何构型相对基态变化较小, 这与实验上观察到的较小的斯托克斯频移现象一致. 配合物1-3的最低能吸收分别在342、431和329 nm, 其磷光发射分别在521、638 和488 nm. 配合物1-3的最高占据分子轨道和最低空轨道主要表现为L配体的π和π*轨道特征, 所以它们的最低能吸收归属于π-π*电荷跃迁, 并混有少量的金属到配体的电荷跃迁(MLCT)和配体之间电荷跃迁(LLCT)微扰, 且其高能吸收也表现为配体内部(IL)和配体间(LL)的电荷跃迁. 此外, 它们的磷光发射和吸收有相似的跃迁特征.     

系列二亚胺Os(II)配合物[Os(L)2(CN)2(phen)] (L＝PH3, DMSO; phen＝1,10-邻二氮杂菲)及[Os(PH3)2(phen)Br2]电子结构和 光谱性质的理论研究

采用自旋限制和非限制B3LYP/UB3LYP方法分别优化了系列Os(II)二亚胺配合物[Os(L)2(CN)2(phen)] [phen＝1,10-邻二氮杂菲; L＝Ph3 (1), 二甲基亚砜(DMSO) (2)]及[Os(PH3)2(phen)Br2] (3)的基态和激发态几何构型. 通过TD-DFT方法结合PCM溶剂化模型计算了配合物1～3在二氯甲烷溶液中的吸收和发射光谱并指认了相应的跃迁性质. 通过理论化学计算, 揭示了π酸配体及π碱配体对配合物磷光发射性质的影响及原因. 并进一步解释了配合物3易于在Os—Br键处断裂而发生反应的量子化学机理. 对配合物在不同溶剂中的磷光发射性质的计算表明, 溶剂对配合物的量子产率存在着影响并且配合物具有溶剂化显色效应.     

DFT/TDDFT insight into the impact of ring size of the NHC chelating unit of high effective phosphorescent Platinum (II) complexes

Uncovering the photodeactivation mechanisms of unique N‐heterocyclic carbene (NHC)‐based transition metal complexes is favorable for designing more high‐efficiency phosphorescent materials. In this work, four bidentate platinum (II) complexes with NHC‐chelate are investigated by the density functional theory (DFT) and time‐dependent density functional theory (TDDFT) to probe into how the ring size of NHC‐chelate unit influences on electronic structures and the phosphorescent properties. To illustrate the photodeactivation mechanisms clearly, three significant photodeactivation processes (radiative decay process, temperature‐independent and temperature‐dependent nonradiative decay processes) were taken into consideration. We stated that radiative decay rate constants k_r slightly increased with declined number of NHC‐chelate ring, owing to the gradually larger SOC matrix elements between the T₁ state and S_n states. Combining the temperature‐independent with temperature‐dependent nonradiative decay processes, the nonradiative decay rate k_nr is Pt‐4 (five‐membered) < Pt‐3 (six‐membered) < Pt‐2 (seven‐membered) < Pt‐1 (eight‐membered). The calculated results testify that the decrease of size of the NHC chelating unit is a reliable insurance to improve the quantum yield. The designed complex Pt‐4 with five‐membered NHC‐ring can serve as a highly efficient phosphorescent material in the future. The results indicated controlling the ring size of NHC‐chelate is a feasible method to tune phosphorescence properties of Pt (II) complexes.     

TD-DFT Studies on Electronic and Spectral Properties of Platinum(II) Complexes with Phenol and Pyridine Groups

The molecular structures of the ground and the lowest triplet states for a series of Pt(II) complexes PtLCl(1)[L=6-(2-hydroxyphenyl)-2,2′-bipyridine], Pt(pp)₂[pp=2-(2-hydroxyphenyl)pyridine](2), PtbpyCl₂(bpy=2,2′- bipyridine)(3), and the free tridentate L ligand(4) were optimized by the density functional theory B3LYP and UB3LYP methods, respectively. On the basis of optimized geometries, the spectral properties were investigated with time-dependent density functional theory(TD-DFT). In comparison with those of complexes 2 and 3, the more rigid structure of complex 1 together with its low rate of the radiationless decay via nonemissive d-d state leads to higher photoluminescence quantum efficiency. And the phosphorescence quantum efficiency of complex 1 can be easily controlled by modifying auxiliary ligands. The introduction of fluorine ligand into complexes can effectively increase the radiation transition rate and decrease the radiationless d-d transition rate, and as a result, a novel complex PtLF(5) might be a good phosphorescent material suitable for organic electronic devices.     

Ambient-temperature metal-to-ligand charge-transfer phosphorescence facilitated by triarylboron: Bnpa and its metal complexes

A Cu(I) complex, 1, and a Pt(II) complex, 2a, of a triarylboron ligand, Bnpa, with bright ambient-temperature phosphorescence have been obtained. The phosphorescence of these complexes is highly sensitive toward molecular oxygen and has a distinct response to fluoride ions. For 1, the fluoride ion causes phosphorescent quenching and Bnpa dissociation, and for 2a, it switches phosphorescent color from yellow to green. The Cu(I) complex has an exceptionally high emission quantum yield (0.88) in the solid state.     

Structural,Electronic and Optical Properties of Multifunctional Iridium(III) and Platinum(II) Metallophosphors for Organic Light‐Emitting Diodes

An elaborated theoretical investigation on the optical and electronic properties of three fluorene‐based platinum(II) and iridium(III) cyclometalated complexes Pt‐a , Ir‐a and Ir‐b is reported. The geometric and electronic structures of the complexes in the ground state are studied with density functional theory and Hartree Fock approaches, while the lowest triplet excited states are optimized by singles configuration interaction (CIS) methods. At the time‐dependent density functional theory (TD‐DFT) level, molecular absorption and emission properties were calculated on the basis of optimized ground‐ and excited‐state geometries, respectively. The computational results show that the appearance of triphenylamino (TPA) moiety at the 9‐position of fluorene ring favors the hole‐creation and leads to red‐shifts of absorption and emission spectra. Moreover, Pt‐a and Ir‐b are nice hole‐transporting materials whereas Ir‐a has good charge‐transfer balance, which render them useful for the realization of efficient OLEDs (Organic Light‐Emitting Diodes).     

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.     

Meso-四(对-酰氧基苯基)卟啉铂配合物的合成和性能

合成了meso-四(对-酰氧基苯基)卟啉铂配合物。采用UV-Vis、1HNMR、MS、光致发光光谱、DSC、热台偏光显微镜等分析测试技术对化合物的结构和性能进行了表征。结果表明,配合物在660nm附近有较强的三线态发射,磷光量子效率在0.183～0.211之间,三线态寿命为8.86～13.52μs。表明在卟啉铂meso位上连接长链酰氧基后,能够降低三线态寿命,减少配合物分子间的相互作用。同时长链酰氧基的引入赋予配合物液晶性质。这类卟啉铂配合物有望用作有机电致发光器件和线偏振发光器件的磷光材料。     

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, structure, and spectral luminescent properties of novel 1,2,4-triazole derivatives containing benzthiazole group

Novel derivatives of 1,2,4-triazol with benzthiazole fragment have been prepared, including Cu(II) and Be complexes. Their structure and spectral luminescent properties have been investigated. With ohydroxyphenylbenzthiazolyl-1,2,4-triazole as an example, the density functional theory has been applied to find the stable conformers with different structures of coordination nodes, stabilized by intramolecular hydrogen bonds between hydroxyl group hydrogen and either triazole of benzthiazole nitrogen.     

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     

Effect of Water Microsolvation on the Excited-State Proton Transfer of 3-Hydroxyflavone Enclosed in γ-Cyclodextrin

The effect of microsolvation on excited-state proton transfer (ESPT) reaction of 3-hydroxyflavone (3HF) and its inclusion complex with γ-cyclodextrin (γ-CD) was studied using computational approaches. From molecular dynamics simulations, two possible inclusion complexes formed by the chromone ring (C-ring, Form I) and the phenyl ring (P-ring, Form II) of 3HF insertion to γ-CD were observed. Form II is likely more stable because of lower fluctuation of 3HF inside the hydrophobic cavity and lower water accessibility to the encapsulated 3HF. Next, the conformation analysis of these models in the ground (S₀) and the first excited (S₁) states was carried out by density functional theory (DFT) and time-dependent DFT (TD-DFT) calculations, respectively, to reveal the photophysical properties of 3HF influenced by the γ-CD. The results show that the intermolecular hydrogen bonding (interHB) between 3HF and γ-CD, and intramolecular hydrogen bonding (intraHB) within 3HF are strengthened in the S₁ state confirmed by the shorter interHB and intraHB distances and the red-shift of O–H vibrational modes involving in the ESPT process. The simulated absorption and emission spectra are in good agreement with the experimental data. Significantly, in the S₁ state, the keto form of 3HF is stabilized by γ-CD, explaining the increased quantum yield of keto emission of 3HF when complexing with γ-CD in the experiment. In the other word, ESPT of 3HF is more favorable in the γ-CD hydrophobic cavity than in aqueous solution.     

Phosphorescent Bimetallic C^C* Platinum(ii) Complexes with Bridging Substituted Diphenylformamidinates

A series of phosphorescent bimetallic platinum(II) complexes is presented, which were synthesized by the combination of bidentate cyclometalated N-heterocyclic carbene ligands and different bridging diphenylformamidinates. The complexes were characterized by standard techniques and additionally two solid-state structures could be obtained. Photoluminescence measurements revealed the strong emissive behavior of the compounds with quantum yields of up to 90 % and emission lifetimes of approx. 2 μs. The effect of the substitution pattern in the bridging ligands on the structural and photophysical properties of the complexes was examined in detail and rationalized by density functional theory calculations (PBE0/6-311G*).     

Theoretical studies on structures and spectroscopic properties of photoelectrochemical cell ruthenium sensitizers, [Ru(Hmtcterpy)(NCS)3]n- (m = 0, 1, 2, and 3; n = 4, 3, 2, and 1)

A series of ruthenium(II) complexes, [Ru(tcterpy)(NCS)3](4-) (0H), [Ru(Htcterpy)(NCS)3](3-) (1H), [Ru(H2tcterpy)(NCS)3](2-) (2H), and [Ru(H3tcterpy)(NCS)3](-) (3H) (tcterpy = 4,4',4'-tricarboxy-2,2':6',2'-terpyridine), are investigated theoretically to explore their electronic structures and spectroscopic properties. The geometry structures of the complexes in the ground and excited states are optimized by the density functional theory and single-excitation configuration interaction methods, respectively. The absorption and emission spectra of the complexes in gas phase and solutions (ethanol and water) are predicted at the TDDFT(B3LYP) level. The calculations indicate that the protonation effect slightly affects the geometry structures of the complexes in the ground and excited states but leads to significant change in the electronic structures. In cases of both absorptions and emissions, the energy levels of HOMOs and LUMOs for 0H-3H decrease dramatically as a result of the introduction of the COOH groups. The protonation much stabilizes the unoccupied orbitals with respect to the occupied orbitals. Thus, both the absorptions and emissions are red-shifted from 0H to 3H. The phosphorescence of 0H-3H are attributed to tcterpyridine --> d(Ru)/NCS ((3)MLCT/(3)LLCT) transitions. The solvent media can influence the molecular orbital distribution of the complexes; as a consequence, the spectra calculated in the presence of the solvent are in good agreement with the experimental results. The MLCT/LLCT absorptions of 0H in ethanol and water are red-shifted relative to that in the gas phase. However, the MLCT/LLCT absorptions of the protonated complexes (1H-3H) are blue-shifted in ethanol and water with respect to the gas phase. Similarly, the solvent effect causes a blue-shift of the phosphorescent emission for 0H-3H.     

Origin of the Aggregation-Induced Phosphorescence of Platinum(II) Complexes: The Role of Metal–Metal Interactions on Emission Decay in the Crystalline State

Discerning the origins of the phosphorescent aggregation-induced emission (AIE) from Pt(II) complexes is crucial for developing the broader range of photo-functional materials. Over the past few decades, several mechanisms of phosphorescent AIE have been proposed, however, not have been directly elucidated. Herein, we describe phosphorescence and deactivation processes of four class of AIE active Pt(II) complexes in the crystalline state based on experimental and theoretical investigation. These complexes show metal-to-ligand and/or metal−metal-to-ligand charge transfer emission in crystalline state with different heat resistance against thermal emission quenching. The calculated energy profiles including the minimum energy crossing point between S₀ and T₁ states were consistent with the heat resistant properties, which provided the mechanism for AIE expression. Furthermore, we have clarified the role of metal-metal interaction in AIE by comparing two computational models.     

4(3H)-嘧啶酮及其类似物互变异构的理论研究

采用密度泛函理论,在B3LYP/6-311G**基组水平上,计算并考察了4(3H)-嘧啶酮及其类似物(5-氟-4(3H)-嘧啶酮、4-巯基嘧啶和5-氟-4-巯基嘧啶)醇式结构和酮式结构进行结构互变质子迁移过程中的2种可能途径:(a)分子内质子迁移;(b)水助质子迁移.计算结果表明,途经b所需要的活化能较小.研究还表明,氢键在降低反应活化能方面起着重要的作用.     

8-羟基喹啉铍及其衍生物电子光谱性质的含时密度泛函理论研究

运用密度泛函理论(DFT)B3LYP方法和abinitioHF单激发组态相互作用(CIS)法分别优化了有机金属配合物8-羟基喹啉铍(BeQ₂)及其3种衍生物分子的基态及最低激发单重态几何结构.系统分析了分子结构、前线分子轨道特征和能级分布规律以探索电子跃迁机理.应用含时密度泛函理论(TD-DFT)计算分子的电子光谱,揭示了BeQ₂及其衍生物的发光源于配体中π→π^*电子跃迁,指出通过配体修饰可以有效地影响配合物前线分子轨道分布,调整发光波段,并有效提高电荷转移量.     

碱(土)金属离子与2-(3′-羟基-2′-吡啶基)苯并噁唑阳离子-π复合物及其分子内质子转移过程的理论研究

采用密度泛函B3LYP方法,在6-311++G(d,p)基组水平上对碱(土)金属离子(Li+,Na+,K+,Be2+,Mg2+和Ca2+)与2-(3’-羟基-2’-吡啶基)苯并噁唑(HPyBO)的36种阳离子-π复合物的初始构型进行了几何全优化,并计算了其相互作用能.结果表明,碱(土)金属离子与HPyBO复合物有较强的阳离子-π相互作用,部分复合物甚至达到了化学键的强度.相对能量的变化表明碱(土)金属离子的作用能改变HPyBO分子内质子转移过程的能垒,甚至可以导致优势构型反转.当考虑水的溶剂效应后,各质子转移异构体的相对能量及质子转移的能垒均有一定程度的改变.另外,应用分子中的原子(AIM)方法对复合物分子内氢键的键临界点性质进行了分析.     

带烷氧基的苯基蒎烯吡啶铱配合物的合成及光物理性质

合成了一组新型的带有烷氧基团的铱(Ⅲ)配合物[Ir(RO-pppy)3], 并进行了结构表征. 该组配合物在~496 nm处有较强的三重态发射, 磷光量子产率为0.4~0.6, 三重态寿命为2~4 μs. 结果表明, 连接了长链的配合物可减少分子间的聚集, 可以用作有机电致发光器件中的磷光材料.     

Potential strategy used for controlling the phosphorescent properties in tetradentate Pt(II) complexes: Effect of azole ligand

Designing deep‐blue phosphorescent materials is vital and essential in the construction of white organic light‐emitting diodes. Using density functional theory (DFT) and time‐dependent DFT, three tetradentate Pt(II) complexes were investigated in detail to reveal the influence of azole ligand with varying number of N atoms on the emission wavelengths and radiative and non‐radiative decay processes. The calculated results indicate that with an increase of N atoms in azole rings, the radiative decay process can be effectively facilitated. Moreover, an increase of N atoms in azole rings could lead to a distinct blue‐shift of emission wavelengths from 553 to 470 nm. Also, the non‐radiative decay processes, including temperature‐independent and temperature‐dependent ones, were taken into account. The results may provide some valuable and meaningful information for designing high‐performance phosphorescent Pt(II) complexes.