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.     

双核Pt(II)配合物的光谱结构和激发态性质的密度泛函理论研究

采用基于第一性原理的密度泛函理论对单核和双核三联吡啶Pt(II)配合物[Pt(trpy)C≡CH]^＋ (1)和[Pt(trpy)C≡ (2)的基态和激发态以及光谱性质进行了系统研究. 结果揭示了双体配合物中Pt—Pt间距离在激发态时明显短于基态时的距离, 而且双体聚合后最低能吸收和发射波长相对单体配合物发生了明显红移, 这种激发的本质被指认为是来自于[d_σ*(d_δ*π*)]的MMLCT (metal-to-metal-to-ligand charge transfer)电荷转移跃迁. 另外, 对研究的配合物, 用VWN (Vosko-Wilk-Nusair)泛函优化得到的几何和用SAOP(轨道势的统计平均)计算的光谱能量和实验值符合得很好, 能够准确反映实验现象.     

Experimental Studies on Isonicotinato Cadmium(II) Complex [Cd(C<Subscript>6</Subscript>H<Subscript>4</Subscript>NO<Subscript>2</Subscript>)<Subscript>2</Subscript>(H<Subscript>2</Subscript>O)<Subscript>4</Subscript>] and Density Functional Calculations

Isonicotinato cadmium(II) complex [Cd(C₆H₄NO₂)₂(H₂O)₄] has been synthesized by hydrothermal method and characterized by elemental analysis, electronic-spectra and thermogravimetric analysis. Density functional theory (DFT) method calculations of the structure, atomic charges distribution, electronic spectra, natural population analysis and the thermodynamic properties at different temperatures have been performed. The calculated results show the electronic transitions are mainly derived from the contribution of bands π → π^* and the decomposition of the title compound should first occur at the bond of Cd—O, then at the bond of Cd—N, which agrees very well with the experimental data.     

二甲醚在Pt(100)表面吸附的密度泛函理论研究

采用密度泛函理论(DFT)方法结合周期性平板模型,研究了二甲醚(DME)分子在Pt(100)表面上的吸附.通过对不同吸附位(顶位、空位和桥位)下的几何结构、吸附能和mulliken电荷布局计算发现,吸附后C-O键和C-H键都有不同程度的伸长,top位的吸附能最大,hcp位最小;top位吸附有利于C-O键的断裂,bri位吸附则更利于C-H键的断裂。     

Theoretical Investigation on the Electron and Energy Transfer between Peripheral Carrier Transport Groups and Central Chromophores in Electroluminescent Materials

The molecular materials with structures of luminescent core and peripheral carrier groups (e.g. carbazoles), have exhibited high‐performance in organic light‐emitting diodes (OLEDs). Present work is to understand the basic process of electronic and energy exchange between the peripheral functional groups and the central core through quantum chemical analysis. As an example, 4,7‐bis(9,9‐bis(6‐(9H‐carbazol‐9‐yl)hexyl)‐9H‐fluoren‐2‐yl)benzo[c]‐[1,2,5]thiadiazole (TCBzC) is investigated in regards to optoelectronic properties using density functional theory (DFT). The results suggest that the forbidden transition from peripheral carbazole to the central chromophore core makes for separated electrical and optical properties, and high performance electroluminescence (EL) is mainly attributed to the energy‐transfer from carbazoles to the fluorene derivative core     

1,2,3-三氮杂苯－(水)3复合物多体相互作用

The interaction between 1,2,3-triazine and three water molecules was studied using density functional theory B3LYP method at 6-31-t＋＋G^＊＊ basis set. Various structures for 1,2,3-triazine-（water）n （n= 1, 2, 3） complex were investigated and the different lower energy structures were reported. Many-body analysis was also carded out to obtain relaxation energy and many-body interaction energy （two, three, and four-body）, and the most stable conformer has the basis set superposition error corrected interaction energy of -- 102.61 kJ/mol. The relaxation energy, two- and three-body interactions have significant contribution to the total interaction energy whereas four-body interaction was very small for 1,2,3-triazine-（water）3 complex.     

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.     

Structure of AcMet-Gly and Its Interaction with Palladium（Ⅱ） Tetraaqua Complex Studied by Electrospray Mass Spectrometry and Density Functional Theory

The structure of dipepide AcMet‐Gly was determined by X‐ray crystallographic analysis. It possesses mono‐clinic, space group P2₁ (No. 4). with cell dimensions of α=0.8571(2) nm, b=0.5871(2) nm, c= 1.197(3) nm, β= 99.290(10)°. V=0.5944(15) nm³, Z=2, μ=2.74 cm^?1. Mononuclear chelates, described as [Pd(X)(S,N,O‐AcMet‐Gly)]^?, in which Pd(II) is coordinated by thioether, deprotonated amide nitrogen, carbonyl oxygen of me‐thionine and X (AcMetGly or other ligands present in aqueous solution or in mobile phase solution), were detected 5 min after mixing AcMet‐Gly with [Pd(H₂O)₄]^2‐ at room temperature using electrospray ionization mass spectrometry. The geometry of [Pd(H₂O)(S,N,O‐AcMet‐Gly)]^? is optimized at density functional B3LYP/LanL2DZ level. The fused five‐ and six‐membered chelate is responsible for cleavage of Met‐Gly bond. This is the first time to provide a direct evidence for Pd(II)‐mediated cleavage of dipeptides via external solvent attack.     

A density functional study on magnetic exchange interaction between Mn(II) ion and nitronyl nitroxide radical in <Emphasis Type="Italic">trans</Emphasis>-and <Emphasis Type="Italic">cis</Emphasis>-metal-radical complexes

The magneto-structural correlation between a Mn(ll) ion, coordinated in an octahedral environment, and two nitronyl nitroxide radical ligands in trans- and cis-metal-radical complexes is investigated by the broken symmetry (BS) approach within density functional theory (DFT). The dependences of coupling constants J on three structural parameters: (i) bond angle θ (Mn-O-N (nitroxide)); (ii) rotating angle ψ, defined by the nitronyl nitroxide radical plane rotating around the axial Mn-O (nitroxide); (iii) bond distance R (Mn-O (nitroxide)) are directly calculated. Our calculations showed that both trans- and cis-Mn(ll)-radical complexes behave a stronger antiferromagnetic interaction, consistent with experiments. In view of molecular orbital theory, the direct exchanges, including σ-type and π-type exchanges, are responsible for the magnetic exchange pathways. There is a preferable linear correlation between the calculated coupling constants J and the overlap integral squares S b between the local magnetic orbitals at the various rotating angle ψ at the fixed bond angle θ and bond distance R, in both trans- and cis-Mn(ll)-radical complexes.     

Features of the electronic structure of ruthenium tetracarboxylates with axially coordinated nitric oxide (II)

The electronic structure of Ru₂(μ-O₂CR)₄, Ru₂(μ-O₂CR)₄(L)₂ and Ru₂(μ-O₂CR)₄(NO)₂ (R = H, CH₃, CF₃; L = H₂O, THF) ruthenium tetracarboxylates is analyzed on the basis of calculations by the density functional method with full geometry optimization. It is concluded that the axial coordination of nitric oxide (II) to Ru₂(μ-O₂CR)₄ is accompanied by destruction of the metal-metal π-bond with d _πAO Ru reorientation on bonding with NO molecules.     

Complexes of substituted dipyridylpyridazines with palladium(II) and platinum(II)

Reactions of 3,6-bis(2′-pyridyl)pyridazine derivatives (n-dppn)¶ ¶For the n-dppn ligands, n stands for the size of the cyclic aliphatic ring on positions 4 and 5 of the pyridazine ring, n?=?5, 6, 8, and 12. with MX₂(PhCN)₂ (M?=?Pd, Pt; X?=?Cl,?Br) have been investigated. The new complexes cis-[PdCl₂(n-dppn)] (n?=?5,?6,?8,?12), cis-[PtCl₂(n-dppn)]?·?H₂O (n?=?5,?6), cis-[PtCl₂(8-dppn)] and cis-[PtBr₂(5-dppn)] have been characterized by elemental analyses, conductivity measurements, infrared, electronic and ¹H-NMR spectra.     

[M(N)X2]-(M=Ru, Os; X=S2C6H4, mnt)的电子结构和光谱性质的理论研究

利用密度泛函理论(DFT)中的B3LYP方法优化了氮化钌和氮化锇配合物[M(N)X2]-[M=Ru, Os; X=S2C6H4, mnt(maleonitriledithiolate)]的基态几何结构, 得到的几何参数与实验结果吻合得很好. 采用TD-DFT方法, 得到了配合物在CH3CN溶液中的激发态电子结构和电子吸收光谱. 利用SCRF方法中的CPCM模型来模拟溶剂化效应. 研究结果表明, 配合物1~4在CH3CN溶液中的吸收跃迁性质相似, 低能吸收均被指认为LMCT和LLCT的混合跃迁, 高能吸收均被指认为ILCT/LLCT跃迁.     

A density functional study on magnetic exchange interaction between Mn(II) ion and nitronyl nitroxide radical in trans- and cis-metal-radical complexes

In the recent few years, transition metal complexeswith radical ligands have received much attentionaiming at a so-called metal-radical approach for novelmolecular magnet design[1]. One of the more popularfamilies is concerned in nitronyl nitroxide radica…     

Spectral and photophysical properties of mono and dinuclear Pt(II) and Pd(II) complexes: An unusual emission behaviour

Eight mononuclear complexes of the formula [M(N-N)(DHB)] and two binuclear complexes of the formula [M₂(BPY)₂(THB)] where M = Pd(II) or Pt(II), N-N = 2,2′-bipyridine (BPY), 2,2′-biquinoline (BIQ), 4,7-diphenyl-1,10-phenanthroline (DPP), 1,10-phenanthroline (PHEN); DHB = dianion of 3,4-dihydroxybenzaldehyde and THB = tetraanion of 3,3′,4,4′-tetrahydroxy benzaldazine were prepared and their electrochemical, spectral and photophysical properties were examined. These complexes were characterized by chemical analysis, IR and proton NMR spectroscopy. A detailed study on the absorption spectroscopy of these complexes was made. These complexes were found to show a low-energy solvatochromic ligand-to-ligand charge-transfer (LLCT) band. The electronic energies of these bands have been analyzed and compared with electrochemical data. Emission behaviour of the complexes of the series, [Pt(N-N)(DHB)], [Pt(N-N)(DHBA)] where DHBA is the dianion of 3,4-dihydroxybenzoic acid and [Pt₂(BPY)₂(THB)] was also investigated. These platinum complexes were found to emit from a low-energy state at low temperature and a high-energy state at room temperature. Photophysics of these complexes is also discussed.